Primary MALT lymphoma of the breast: pathological and radiological characteristics

PURPOSE

Primary Mucosa-associated lymphoid tissue (MALT) lymphoma is a rare diagnosis in the breast, and clinical diagnosis based on radiological features is often challenging. This study aimed to evaluate the clinicopathological, and radiological characteristics of the patients diagnosed with primary breast MALT lymphoma.

METHODS

This study examined 18 cases of primary MALT lymphoma of the breast diagnosed at a single tertiary center between January 2002 to December 2020. Medical charts, radiological imaging and original pathology slides were reviewed for each case.

RESULTS

All cases were female (gender assigned at birth) and presented with a palpable mass or an incidental imaging finding. Imaging presentation ranged from mammographic asymmetries, circumscribed masses, and ultrasound masses lacking suspicious features. Seventeen cases were biopsied under ultrasound; one received a diagnostic excision biopsy. Microscopic examination of the breast specimens demonstrated atypical small lymphocyte infiltration with plasmacytoid differentiation and rare lymphoepithelial lesions. Immunohistochemistry was performed in all cases and established the diagnosis. Most patients were treated with radiotherapy, and only three were treated with chemotherapy. The median follow-up period was 4 years and 7.5 months, and all patients were alive at the last follow-up.

CONCLUSION

Primary MALT breast lymphomas are usually indolent and non-systemic, and local radiotherapy may effectively alleviate local symptoms. Radiological findings show overlap with benign morphological features, which can delay the diagnosis of this unusual etiology. Although further studies involving a larger cohort could help establish the clinical and radiological characteristics of primary breast MALT lymphomas, pathology remains the primary method of diagnosis.

TRIAL REGISTRATION NUMBER

University Health Network Ethics Committee (CAPCR/UHN REB number 19-5844), retrospectively registered.

Reliability and Variability of Ki-67 Digital Image Analysis Methods for Clinical Diagnostics in Breast Cancer

Ki-67 is a nuclear protein associated with proliferation, and a strong potential biomarker in breast cancer, but is not routinely measured in current clinical management owing to a lack of standardization. Digital image analysis (DIA) is a promising technology that could allow high-throughput analysis and standardization. There is a dearth of data on the clinical reliability as well as intra- and interalgorithmic variability of different DIA methods. In this study, we scored and compared a set of breast cancer cases in which manually counted Ki-67 has already been demonstrated to have prognostic value (n = 278) to 5 DIA methods, namely Aperio ePathology (Lieca Biosystems), Definiens Tissue Studio (Definiens AG), Qupath, an unsupervised immunohistochemical color histogram algorithm, and a deep-learning pipeline piNET. The piNET system achieved high agreement (interclass correlation coefficient: 0.850) and correlation (R = 0.85) with the reference score. The Qupath algorithm exhibited a high degree of reproducibility among all rater instances (interclass correlation coefficient: 0.889). Although piNET performed well against absolute manual counts, none of the tested DIA methods classified common Ki-67 cutoffs with high agreement or reached the clinically relevant Cohen's κ of at least 0.8. The highest agreement achieved was a Cohen's κ statistic of 0.73 for cutoffs 20% and 25% by the piNET system. The main contributors to interalgorithmic variation and poor cutoff characterization included heterogeneous tumor biology, varying algorithm implementation, and setting assignments. It appears that image segmentation is the primary explanation for semiautomated intra-algorithmic variation, which involves significant manual intervention to correct. Automated pipelines, such as piNET, may be crucial in developing robust and reproducible unbiased DIA approaches to accurately quantify Ki-67 for clinical diagnosis in the future.

Healthcare and Cancer Treatment Costs of Breast Screening Outcomes among Higher than Average Risk Women

Concurrent cohorts of 644,932 women aged 50-74 screened annually due to family history, dense breasts or biennially in the Ontario Breast Screening Program (OBSP) from 2011-2014 were linked to provincial administrative datasets to determine health system resource utilization and costs. Age-adjusted mean and median total healthcare costs (2018 CAD) and incremental cost differences were calculated by screening outcome and compared by recommendation using regression models. Healthcare costs were compared overall and 1 year after a false positive (n = 46,081) screening mammogram and 2 years after a breast cancer diagnosis (n = 6011). Mean overall healthcare costs by age were highest for those 60-74, particularly with annual screening for family/personal history (CAD 5425; 95% CI: 5308 to 5557) compared to biennial. Although the mean incremental cost difference was higher (23.4%) by CAD 10,235 (95% CI: 6141 to 14,329) per breast cancer for women screened annually for density ≥ 75% compared to biennially, the cost difference was 12.0% lower (-CAD 461; 95% CI: -777 to -114) per false positive result. In contrast, for women screened annually for family/personal history, the mean cost difference per false positive was 19.7% higher than for biennially (CAD 758; 95% CI: 404 to 1118); however, the cost difference per breast cancer was only slightly higher (2.5%) by CAD 1093 (95% CI: -1337 to CAD 3760). Understanding that associated costs of annual compared to biennial screening may balance out by age and outcome can assist decision-making regarding the use of limited healthcare resources.

Resident Depression and Burnout During the COVID-19 Pandemic: A Survey of Canadian Laboratory Medicine Trainees

CONTEXT.—

Resident physicians face a higher rate of burnout and depression than the general population. Few studies have examined burnout and depression in Canadian laboratory medicine residents, and none during the COVID-19 pandemic.

OBJECTIVE.—

To identify the prevalence of burnout and depression, contributing factors, and the impact of COVID-19 in this population.

DESIGN.—

An electronic survey was distributed to Canadian laboratory medicine residents. Burnout was assessed using the Oldenburg Burnout Inventory. Depression was assessed using the Patient Health Questionnaire 9.

RESULTS.—

Seventy-nine responses were collected. The prevalence of burnout was 63% (50 of 79). The prevalence of depression was 47% (37 of 79). Modifiable factors significantly associated with burnout included career dissatisfaction, below average academic performance, lack of time off for illness, stress related to finances, lack of a peer or staff physician mentor, and a high level of fatigue. Modifiable factors significantly associated with depression further included a lack of access to wellness resources, lack of time off for leisure, and fewer hours of sleep. Fifty-five percent (41 of 74) of participants reported direct impacts to their personal circumstances by the COVID-19 pandemic.

CONCLUSIONS.—

Burnout and depression are significant issues affecting Canadian laboratory medicine residents. As the COVID-19 pandemic continues, we recommend the institution of flexible work arrangements, protected time off for illness and leisure, ongoing evaluation of career satisfaction, formal and informal wellness programming with trainee input, formal mentorship programming, and a financial literacy curriculum as measures to improve trainee wellness.

Annual Mammographic Screening Reduces the Risk of Interval or Higher Stage Invasive Breast Cancers Among Postmenopausal Women in the Ontario Breast Screening Program

Purpose: In the Ontario Breast Screening Program (OBSP) annual screening improved breast cancer detection for women 50–74 years with a family/personal history compared to biennial, while detection was equivalent for women screened annually for mammographic density ≥75%. This study compares the risk of interval or higher stage invasive cancers among postmenopausal women screened annually vs biennially by age and estrogen use. Methods: A retrospective design identified 4247 invasive breast cancers diagnosed among concurrent cohorts of women 50–74 screened in the OBSP with digital mammography between 2011 and 2014, followed until 2016. Polytomous logistic regression estimated the risk of interval or higher stage breast cancers by age and estrogen use between women screened annually because of first-degree relative with breast or ovarian cancer or personal history of ovarian cancer, or mammographic density ≥75%, and those screened biennially. Results: The risk of interval vs screen-detected cancers was significantly reduced in women screened annually for family/personal history (OR=.64; 95%CI:0.51–.80), particularly those 60–74 years (OR=.59; 95%CI:0.45–.77) or not currently using estrogen (OR=.66; 95%CI:0.52–.83) compared to those screened biennially. The risk of stage II–IV vs stage I tumors was also lower in women 60–74 years screened annually for family/personal history (OR=.79; 95%CI:0.64–.97) and in those screened annually for mammographic density ≥75% currently using estrogen (OR=.51; 95%CI:0.26–1.01) compared to women screened biennially. Conclusion: Postmenopausal women at increased risk screened annually had equivalent or reduced risks of interval or higher stage invasive breast cancers than those screened biennially, further supporting risk-based screening in this population.

Mutations in Noncoding Cis-Regulatory Elements Reveal Cancer Driver Cistromes in Luminal Breast Cancer

Whole-genome sequencing of primary breast tumors enabled the identification of cancer driver genes and noncoding cancer driver plexuses from somatic mutations. However, differentiating driver from passenger events among noncoding genetic variants remains a challenge. Herein, we reveal cancer-driver cis-regulatory elements linked to transcription factors previously shown to be involved in development of luminal breast cancers by defining a tumor-enriched catalogue of approximately 100,000 unique cis-regulatory elements from 26 primary luminal estrogen receptor (ER)⁺ progesterone receptor (PR)⁺ breast tumors. Integrating this catalog with somatic mutations from 350 publicly available breast tumor whole genomes, we uncovered cancer driver cistromes, defined as the sum of binding sites for a transcription factor, for ten transcription factors in luminal breast cancer such as FOXA1 and ER, nine of which are essential for growth in breast cancer with four exclusive to the luminal subtype. Collectively, we present a strategy to find cancer driver cistromes relying on quantifying the enrichment of noncoding mutations over cis-regulatory elements concatenated into a functional unit. IMPLICATIONS: Mapping the accessible chromatin of luminal breast cancer led to discovery of an accumulation of mutations within cistromes of transcription factors essential to luminal breast cancer. This demonstrates coopting of regulatory networks to drive cancer and provides a framework to derive insight into the noncoding space of cancer.

Heterogeneity of Circulating Tumor Cell-Associated Genomic Gains in Breast Cancer and Its Association with the Host Immune Response

Tumor cells that preferentially enter circulation include the precursors of metastatic cancer. Previously, we characterized circulating tumor cells (CTC) from patients with breast cancer and identified a signature of genomic regions with recurrent copy-number gains. Through FISH, we now show that these CTC-associated regions are detected within the matched untreated primary tumors of these patients (21% to 69%, median 55.5%, n = 19). Furthermore, they are more prevalent in the metastases of patients who died from breast cancer after multiple rounds of treatment (70% to 100%, median 93%, samples n = 41). Diversity indices revealed that higher spatial heterogeneity for these regions within primary tumors is associated with increased dissemination and metastasis. An identified subclone with multiple regions gained (MRG clone) was enriched in a posttreatment primary breast carcinoma as well as multiple metastatic tumors and local breast recurrences obtained at autopsy, indicative of a distinct early subclone with the capability to resist multiple lines of treatment and eventually cause death. In addition, multiplex immunofluorescence revealed that tumor heterogeneity is significantly associated with the degree of infiltration of B lymphocytes in triple-negative breast cancer, a subtype with a large immune component. Collectively, these data reveal the functional potential of genetic subclones that comprise heterogeneous primary breast carcinomas and are selected for in CTCs and posttreatment breast cancer metastases. In addition, they uncover a relationship between tumor heterogeneity and host immune response in the tumor microenvironment. SIGNIFICANCE: As breast cancers progress, they become more heterogeneous for multiple regions amplified in circulating tumor cells, and intratumoral spatial heterogeneity is associated with the immune landscape.

Single allele loss-of-function mutations select and sculpt conditional cooperative networks in breast cancer

The most common events in breast cancer (BC) involve chromosome arm losses and gains. Here we describe identification of 1089 gene-centric common insertion sites (gCIS) from transposon-based screens in 8 mouse models of BC. Some gCIS are driver-specific, others driver non-specific, and still others associated with tumor histology. Processes affected by driver-specific and histology-specific mutations include well-known cancer pathways. Driver non-specific gCIS target the Mediator complex, Ca++ signaling, Cyclin D turnover, RNA-metabolism among other processes. Most gCIS show single allele disruption and many map to genomic regions showing high-frequency hemizygous loss in human BC. Two gCIS, Nf1 and Trps1, show synthetic haploinsufficient tumor suppressor activity. Many gCIS act on the same pathway responsible for tumor initiation, thereby selecting and sculpting just enough and just right signaling. These data highlight ~1000 genes with predicted conditional haploinsufficient tumor suppressor function and the potential to promote chromosome arm loss in BC.

The tumor cell-derived matrix of lobular breast cancer: a new vulnerability

Invasive lobular carcinoma (ILC) of the breast is a very common disease. Despite its prevalence, these tumors are relatively understudied. One reason for this is a relative lack of models for ILC. This challenge was addressed by Brisken and colleagues through development of an intraductal injection-based xenograft system for the study of ERα⁺ breast cancers, including both ILC and more common invasive ductal carcinoma (IDC; Sflomos et al, 2016). In this issue of EMBO Molecular Medicine, the same group have applied intraductal injection-based xenografts to identify novel tumor cell-specific transcriptional signatures in ILC (Sflomos et al, 2021). In doing so they found overexpression of lysyl oxidase-like 1 (LOXL1) to be both responsible for the frequently seen stiff collagen-rich extracellular matrix of lobular breast cancer and essential for their robust growth and metastatic dissemination in vivo, thereby identifying a novel therapeutic target.

Annual vs Biennial Screening: Diagnostic Accuracy Among Concurrent Cohorts Within the Ontario Breast Screening Program

BACKGROUND

The Ontario Breast Screening Program recommends annual mammography to women age 50-74 years at increased risk because of family history of breast or ovarian cancer or personal history of ovarian cancer or mammographic density 75% or greater. Few studies have examined the diagnostic accuracy of recommendations based on risk factors and included screen film as well as digital mammography.

METHODS

A retrospective design identified concurrent cohorts of women age 50-74 years screened annually or biennially with digital mammography only between 2011 and 2014 and followed until 2016 or breast cancer diagnosis. Diagnostic accuracy measures were compared between women screened annually because of first-degree relative of breast or ovarian cancer or personal history of ovarian cancer (n = 67 795 women), mammographic density 75% or greater (n = 51 956), or both (n = 3758) and those screened biennially (n = 526 815). The association between recommendation and sensitivity and specificity was assessed using generalized estimating equation models. All P values are two-sided.

RESULTS

For annual screening because of family or personal history vs biennial, sensitivity was statistically significantly higher (81.7% vs 70.6%; OR = 1.86, 95% CI = 1.48 to 2.34), particularly for invasive cancers and postmenopausal women. Although there was no statistically significant difference in sensitivity for annual screening for mammographic density 75% or greater, specificity was statistically significantly lower (91.3%; OR = 0.87, 95% CI = 0.80 to 0.96) vs biennial (92.3%), particularly for women age 50-59 years.

CONCLUSION

Compared with biennial screening, annual screening improved detection for women with a family or personal history of breast and/or ovarian cancer, supporting screening that is more frequent. The benefit for annual screening for women with higher mammographic density must be weighed against possible harms of increased false positives.

GLUT1 inhibition blocks growth of RB1-positive triple negative breast cancer

Triple negative breast cancer (TNBC) is a deadly form of breast cancer due to the development of resistance to chemotherapy affecting over 30% of patients. New therapeutics and companion biomarkers are urgently needed. Recognizing the elevated expression of glucose transporter 1 (GLUT1, encoded by SLC2A1) and associated metabolic dependencies in TNBC, we investigated the vulnerability of TNBC cell lines and patient-derived samples to GLUT1 inhibition. We report that genetic or pharmacological inhibition of GLUT1 with BAY-876 impairs the growth of a subset of TNBC cells displaying high glycolytic and lower oxidative phosphorylation (OXPHOS) rates. Pathway enrichment analysis of gene expression data suggests that the functionality of the E2F pathway may reflect to some extent OXPHOS activity. Furthermore, the protein levels of retinoblastoma tumor suppressor (RB1) strongly correlate with the degree of sensitivity to GLUT1 inhibition in TNBC, where RB1-negative cells are insensitive to GLUT1 inhibition. Collectively, our results highlight a strong and targetable RB1-GLUT1 metabolic axis in TNBC and warrant clinical evaluation of GLUT1 inhibition in TNBC patients stratified according to RB1 protein expression levels.

Performance Measures of Magnetic Resonance Imaging Plus Mammography in the High Risk Ontario Breast Screening Program

BACKGROUND

The Ontario Breast Screening Program expanded in July 2011 to screen high-risk women age 30-69 years with annual magnetic resonance imaging (MRI) and digital mammography. This study examined the benefits of screening with mammography and MRI by age and risk criteria.

METHODS

This prospective cohort study included 8782 women age 30-69 years referred to the High Risk Ontario Breast Screening Program from July 2011 to June 2015, with final results to December 2016. Cancer detection rates, sensitivity, and specificity of MRI and mammography combined were compared with each modality individually within risk groups stratified by age using generalized estimating equation models. Prognostic features of screen-detected breast cancers were compared by modality using Fisher exact test. All P values are two-sided.

RESULTS

Among 20 053 screening episodes, there were 280 screen-detected breast cancers (cancer detection rate = 14.0 per 1000, 95% confidence interval [CI] = 12.4 to 15.7). The sensitivity of mammography was statistically significantly lower than that of MRI plus mammography (40.8%, 95% CI = 29.3% to 53.5% vs 96.0%, 95% CI = 92.2% to 98.0%, P < .001). In mutation carriers age 30-39 years, sensitivity of the combination was comparable with MRI alone (100.0% vs 96.8%, 95% CI = 79.2% to 100.0%, P = .99) but with statistically significantly decreased specificity (78.0%, 95% CI = 74.7% to 80.9% vs 86.2%, 95% CI = 83.5% to 88.5%, P < .001). In women age 50-69 years, combining MRI and mammography statistically significantly increased sensitivity compared with MRI alone (96.3%, 95% CI = 90.6% to 98.6% vs 90.9%, 95% CI = 83.6% to 95.1%, P = .02), with a small but statistically significant decrease in specificity (84.2%, 95% CI = 83.1% to 85.2% vs 90.0%, 95% CI = 89.2% to 90.9%, P < .001).

CONCLUSIONS

Screening high risk women age 30-39 years with annual MRI only may be sufficient for cancer detection and should be evaluated further, particularly for mutation carriers. Among women age 50-69 years, detection is most effective when mammography is included with annual MRI.

Cell invasion in digital microfluidic microgel systems

Microfluidic methods for studying cell invasion can be subdivided into those in which cells invade into free space and those in which cells invade into hydrogels. The former techniques allow straightforward extraction of subpopulations of cells for RNA sequencing, while the latter preserve key aspects of cell interactions with the extracellular matrix (ECM). Here, we introduce "cell invasion in digital microfluidic microgel systems" (CIMMS), which bridges the gap between them, allowing the stratification of cells on the basis of their invasiveness into hydrogels for RNA sequencing. In initial studies with a breast cancer model, 244 genes were found to be differentially expressed between invading and noninvading cells, including genes correlating with ECM-remodeling, chemokine/cytokine receptors, and G protein transducers. These results suggest that CIMMS will be a valuable tool for probing metastasis as well as the many physiological processes that rely on invasion, such as tissue development, repair, and protection.

Amplification of a calcium channel subunit CACNG4 increases breast cancer metastasis

BACKGROUND

Previously, we found that amplification of chromosome 17q24.1-24.2 is associated with lymph node metastasis, tumour size, and lymphovascular invasion in invasive ductal carcinoma. A gene within this amplicon, CACNG4, an L-type voltage-gated calcium channel gamma subunit, is elevated in breast cancers with poor prognosis. Calcium homeostasis is achieved by maintaining low intracellular calcium levels. Altering calcium influx/efflux mechanisms allows tumour cells to maintain homeostasis despite high serum calcium levels often associated with advanced cancer (hypercalcemia) and aberrant calcium signaling.

METHODS

In vitro 2-D and 3-D assays, and intracellular calcium influx assays were utilized to measure tumourigenic activity in response to altered CANCG4 levels and calcium channel blockers. A chick-CAM model and mouse model for metastasis confirmed these results in vivo.

FINDINGS

CACNG4 alters cell motility in vitro, induces malignant transformation in 3-dimensional culture, and increases lung-specific metastasis in vivo. CACNG4 functions by closing the channel pore, inhibiting calcium influx, and altering calcium signaling events involving key survival and metastatic pathway genes (AKT2, HDAC3, RASA1 and PKCζ).

INTERPRETATION

CACNG4 may promote homeostasis, thus increasing the survival and metastatic ability of tumour cells in breast cancer. Our findings suggest an underlying pathway for tumour growth and dissemination regulated by CACNG4 that is significant with respect to developing treatments that target these channels in tumours with aberrant calcium signaling.

FUNDING

Canadian Breast Cancer Foundation, Ontario; Canadian Institutes of Health Research.

A Four-Chemokine Signature Is Associated with a T-cell-Inflamed Phenotype in Primary and Metastatic Pancreatic Cancer

PURPOSE

The molecular drivers of antitumor immunity in pancreatic ductal adenocarcinoma (PDAC) are poorly understood, posing a major obstacle for the identification of patients potentially amenable for immune-checkpoint blockade or other novel strategies. Here, we explore the association of chemokine expression with effector T-cell infiltration in PDAC.

EXPERIMENTAL DESIGN

Discovery cohorts comprised 113 primary resected PDAC and 107 PDAC liver metastases. Validation cohorts comprised 182 PDAC from The Cancer Genome Atlas and 92 PDACs from the Australian International Cancer Genome Consortium. We explored associations between immune cell counts by immunohistochemistry, chemokine expression, and transcriptional hallmarks of antitumor immunity by RNA sequencing (RNA-seq), and mutational burden by whole-genome sequencing.

RESULTS

Among all known human chemokines, a coregulated set of four (CCL4, CCL5, CXCL9, and CXCL10) was strongly associated with CD8⁺ T-cell infiltration (P < 0.001). Expression of this "4-chemokine signature" positively correlated with transcriptional metrics of T-cell activation (ZAP70, ITK, and IL2RB), cytolytic activity (GZMA and PRF1), and immunosuppression (PDL1, PD1, CTLA4, TIM3, TIGIT, LAG3, FASLG, and IDO1). Furthermore, the 4-chemokine signature marked tumors with increased T-cell activation scores (MHC I presentation, T-cell/APC costimulation) and elevated expression of innate immune sensing pathways involved in T-cell priming (STING and NLRP3 inflammasome pathways, BATF3-driven dendritic cells). Importantly, expression of this 4-chemokine signature was consistently indicative of a T-cell-inflamed phenotype across primary PDAC and PDAC liver metastases.

CONCLUSIONS

A conserved 4-chemokine signature marks resectable and metastatic PDAC tumors with an active antitumor phenotype. This could have implications for the appropriate selection of PDAC patients in immunotherapy trials.

Modelling the MYC-driven normal-to-tumour switch in breast cancer

The potent MYC oncoprotein is deregulated in many human cancers, including breast carcinoma, and is associated with aggressive disease. To understand the mechanisms and vulnerabilities of MYC-driven breast cancer, we have generated an in vivo model that mimics human disease in response to MYC deregulation. MCF10A cells ectopically expressing a common breast cancer mutation in the phosphoinositide 3 kinase pathway (PIK3CA^H1047R) led to the development of organised acinar structures in mice. Expressing both PIK3CA^H1047R and deregulated MYC led to the development of invasive ductal carcinoma. Therefore, the deregulation of MYC expression in this setting creates a MYC-dependent normal-to-tumour switch that can be measured in vivo. These MYC-driven tumours exhibit classic hallmarks of human breast cancer at both the pathological and molecular level. Moreover, tumour growth is dependent upon sustained deregulated MYC expression, further demonstrating addiction to this potent oncogene and regulator of gene transcription. We therefore provide a MYC-dependent model of breast cancer, which can be used to assay invivo tumour signalling pathways, proliferation and transformation from normal breast acini to invasive breast carcinoma. We anticipate that this novel MYC-driven transformation model will be a useful research tool to better understand the oncogenic function of MYC and for the identification of therapeutic vulnerabilities.

Summary: We present a MYC-driven transformation model of breast cancer that recapitulates the disease in vivo and which can be used to identify MYC-dependent cancer vulnerabilities.

Breast specimen handling and reporting in the post-neoadjuvant setting: challenges and advances

Neoadjuvant systemic therapy is becoming more commonly used in patients with earlier stages of breast cancer. To assess tumour response to neoadjuvant chemotherapy, pathological evaluation is the gold standard. Depending on the treatment response, the pathological examination of these specimens can be quite challenging. However, a uniform approach to evaluate post-neoadjuvant-treated breast specimens has been lacking. Furthermore, there is no single universally accepted or endorsed classification system for assessing treatment response in this setting. Recent initiatives have attempted to create a standardised protocol for evaluation of post-neoadjuvant breast specimens. This review outlines the necessary information that should be collected prior to macroscopic examination of these specimens, the recommended and most pragmatic approach to tissue sampling for microscopic examination, describes the macroscopic and microscopic features of post-therapy breast specimens, summarises two commonly used systems for classifying treatment response and outlines the critical variables that should be included in the final pathology report.

MYC Protein Interactome Profiling Reveals Functionally Distinct Regions that Cooperate to Drive Tumorigenesis

Transforming members of the MYC family (MYC, MYCL1, and MYCN) encode transcription factors containing six highly conserved regions, termed MYC homology boxes (MBs). By conducting proteomic profiling of the MB interactomes, we demonstrate that half of the MYC interactors require one or more MBs for binding. Comprehensive phenotypic analyses reveal that two MBs, MB0 and MBII, are universally required for transformation. MBII mediates interactions with acetyltransferase-containing complexes, enabling histone acetylation, and is essential for MYC-dependent tumor initiation. By contrast, MB0 mediates interactions with transcription elongation factors via direct binding to the general transcription factor TFIIF. MB0 is dispensable for tumor initiation but is a major accelerator of tumor growth. Notably, the full transforming activity of MYC can be restored by co-expression of the non-transforming MB0 and MBII deletion proteins, indicating that these two regions confer separate molecular functions, both of which are required for oncogenic MYC activity.

Cdh1 and Pik3ca Mutations Cooperate to Induce Immune-Related Invasive Lobular Carcinoma of the Breast

CDH1 and PIK3CA are the two most frequently mutated genes in invasive lobular carcinoma (ILC) of the breast. Transcription profiling has identified molecular subtypes for ILC, one of which, immune-related (IR), is associated with gene expression linked to lymphocyte and macrophage infiltration. Here, we report that deletion of Cdh1, together with activation of Pik3ca in mammary epithelium of genetically modified mice, leads to formation of IR-ILC-like tumors with immune cell infiltration, as well as gene expression linked to T-regulatory (Treg) cell signaling and activation of targetable immune checkpoint pathways. Interestingly, these tumors show enhanced Rac1- and Yap-dependent transcription and signaling, as well as sensitivity to PI3K, Rac1, and Yap inhibitors in culture. Finally, high-dimensional immunophenotyping in control mouse mammary gland and IR-ILC tumors by mass cytometry shows dramatic alterations in myeloid and lymphoid populations associated with immune suppression and exhaustion, highlighting the potential for therapeutic intervention via immune checkpoint regulators.

Negative Enrichment and Isolation of Circulating Tumor Cells for Whole Genome Amplification

Circulating tumor cells (CTCs) are a rare population of cells found in the peripheral blood of patients with many types of cancer such as breast, prostate, colon, and lung cancers. Higher numbers of these cells in blood are associated with a poorer prognosis of patients. Genomic profiling of CTCs would help characterize markers specific for the identification of these cells in blood, and also define genomic alterations that give these cells a metastatic advantage over other cells in the primary tumor. Here, we describe an immunomagnetic method to enrich CTCs from the blood of patients with breast cancer, followed by single-cell laser capture microdissection to isolate single CTCs. Whole genome amplification of isolated CTCs allows for many downstream applications to be performed to aide in their characterization, such as whole genome or exome sequencing, Single Nucleotide Polymorphism (SNP) and copy number analysis, and targeted sequencing or quantitative Polymerase Chain Reaction (qPCR) for genomic analyses.

Abstract P2-12-15: ReFilx- synthetic biodegradable soft tissue fillers for breast conserving surgery in breast cancer

Introduction: Breast conserving surgery (BCS) is the most common procedure performed in breast cancers, but it can often result in breast deformities that can have negative impacts on quality of life. With better treatments, more breast cancer survivors are expected to live longer, the demand for achieving optimal cosmetic outcomes has also increased accordingly. Currently, oncoplastic techniques involving local tissue rearrangement with or without contralateral balancing procedures are used in specialized centers to achieve breast symmetry in some patients. When a breast deformity occurs, corrective options include: fat grafting, autologous flap procedures and completion mastectomy with immediate reconstruction. These techniques have long operative times, longer length of hospital stay and higher complication rates. Commercially-available synthetic implants are fabricated in pre-determined sizes and thus are not suitable to reconstruct partial breast deformities of varying size and shape. We explored the use of amino-acid based biodegradable polyurethanes as tissue fillers for BCS due to their chemical versatility, superior mechanical properties and tailored biocompatibility. Objective: To evaluate novel biodegradable polymer constructs, referred to as ReFilx, as soft tissue fillers for BCS defects. Hypothesis: Implantation of ReFilx during BCS will maintain breast shape and size and promote tissue regeneration in and around the biodegradable biomaterial, in contrast to sham controls. Methods: Two ReFilx formulations with high porosity, mechanical properties (compressive modulus=45±6 kPa and 31±9 kPa) comparable to native breast tissue and a moderate degree of swelling (202±6% and 248±6%) were selected for implantation in porcine BCS defects. Three female Yucatan Minipigs (age=4 years, weight=100-120 kg, 12 breasts per pig) received BCS to remove normal breast tissue of approximately 2 cm diameter, after which the defects were filled with ReFilx Formulation A, ReFilx Formulation B, or no filler (sham control). At 6, 12, 24, and 36 weeks post-implantation (n=3 per group), ultrasound breast examinations and mastectomies of each selected group of breasts were performed. Samples were fixed in 10% buffered formalin and stained with H&E, Masson's Trichrome and immunohistomchemistry using CD31. Results: ReFilx formulations maintained breast size and shape, with similar stiffness to native breast tissue, while sham controls collapsed over 36 weeks. The ReFilx fillers supported cell and tissue infiltration and neovascularization, as indicated by Masson's Trichrome and CD31 staining, respectively, without eliciting foreign body giant cell formation, fibrosis, or chronic inflammation, commonly associated with implanted medical devices. Conclusions: ReFilx are promising soft tissue fillers for breast volume restoration, representing a simple, versatile, permanent, and aesthetically superior solution to prevent soft tissue deformities. Acknowledgements: MaRS PoP fund, grant # MI 2011-170, NSERC # SYN 430828. Haynes Connell Foundation Breast Cancer Fund.

Citation Format: Leong WL, Sharifpoor S, Battiston K, Charleton D, Corrigan M, McCready DR, Done SJ, Santerre JP. ReFilx- synthetic biodegradable soft tissue fillers for breast conserving surgery in breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-12-15.

Abstract P4-15-05: The presence of one or multiple foci of microinvasion is not associated with an increased risk of local recurrence in women with ductal carcinoma in situ treated with breast conserving therapy

Background: Ductal Carcinoma in Situ (DCIS) is a non-invasive breast cancer often treated with breast-conserving surgery (BCS) with or without radiotherapy (RT). It is unclear if the presence of microinvasion (MI) (invasion ≤1mm) is associated with an increased risk of LR (DCIS or invasive) or invasive LR compared to women with pure DCIS. In addition, the impact of multiple foci (&gt;2) of MI compared to pure DCIS is also unknown; therefore, it is unclear if some women with MI require more aggressive treatment. We evaluated the impact of the presence of MI and the number of foci of MI on the risks of any LR and invasive LR in a population of women with DCIS with and without MI treated with BCS.

Methods: The cohort includes all women diagnosed with pure DCIS or DCIS with MI in Ontario from 1994-2003 treated with BCS +/- RT. All cases had systematic pathology review to confirm the presence and number of foci of MI. Treatment and outcomes were ascertained through administrative databases and validated by chart review. Cox proportional hazards model was used to evaluate the impact of MI and the number of foci of MI (1 vs &gt;2 foci) on the development of any LR and invasive LR compared to cases with pure DCIS. The 10-yr local recurrence-free survival (LRFS) and invasive LRFS rates were calculated using the Kaplan-Meier approach with differences compared using the log-rank test.

Results: The population cohort includes 2,988 women with DCIS treated by BCS (N=2,721 pure DCIS, N= 267 DCIS with MI). Median follow-up (12 years; p=.23) and median age at diagnosis (58 years; p=.17) were similar in both groups. RT was given in 58% of cases with MI and 51% of cases with pure DCIS (p=.03). Hormonal therapy was utilized in 7.1% of women with MI and 5.3% of women with pure DCIS (p=.22). LR developed in 59 (22.1%) cases with MI and 530 (19.6%) cases of pure DCIS. Women with MI were more likely to have high nuclear grade (p&lt;.001), and larger tumor size (p&lt;.001) compared to those without MI. On multivariable analyses adjusted for age, the presence of 1 focus of MI(HR=.92, 95% CI: .64-1.33) or ≥2 foci of MI (HR=1.26, 95% CI: .85-1.85) was not associated with an increased risk of any LR compared to cases with pure DCIS. Factors associated with any LR were age &lt;50 years at diagnosis, RT, multifocality and high nuclear grade. The presence of 1 focus of MI (HR=.86, 95% CI: .52-1.40) or &gt; 2 foci of MI (HR=1.45, 95% CI: .90-2.32) was also not associated with an increased risk of invasive LR compared to cases of pure DCIS. Among women treated with BCS alone, the 10 year LRFS rates were 80%, 75% and 73% for women with pure DCIS, 1 focus, &gt;2 foci of MI (p=.10). The invasive LRFS rates were 89%, 91% and 85% (p=.26). Among women treated with BCS+RT, the 10 year LRFS rates were 87%, 88% and 80% (p=0.32) for women with pure DCIS, 1 focus or ≥2 foci of MI. The invasive LRFS rates were 93%, 90% and 86% (p=.44). There was no interaction between the presence of MI and RT.

Conclusions: Women with DCIS with one or multiple foci of microinvasion (&lt;1mm) treated by breast conserving therapy do not have an increased risk of LR or invasive LR compared to women with pure DCIS.

Citation Format: Lalani N, Paszat L, Sutradhar R, Gu S, Fong C, Nofech-Mozes S, Hanna W, Tuck A, Youngson B, Miller N, Done SJ, Chang MC, Sengupta S, Elavathil L, Jani PA, Bonin M, Rakovitch E. The presence of one or multiple foci of microinvasion is not associated with an increased risk of local recurrence in women with ductal carcinoma in situ treated with breast conserving therapy [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-15-05.

Abstract P2-12-02: Is breast-conserving therapy effective in women with large ductal carcinoma in situ (DCIS) lesions? A population-based analysis

Background: Most women diagnosed with DCIS will be treated by breast-conserving surgery (BCS) with or without radiotherapy (RT). Data on outcomes following breast-conserving therapy are predominantly based on women with small (&lt;25mm) lesions. The paucity of data on outcomes of women with larger (&gt;40mm) DCIS lesions leads to uncertainty of the appropriateness of breast-conserving therapy for women with larger lesions. Specifically, it is unclear if women with large tumors experience higher risks of local recurrence (LR) and invasive LR after BCS+/-RT that would preclude recommendations of breast-conserving therapy. We report the outcomes and evaluate the impact of large tumor size (&gt;40mm) on recurrence risk in a population of women with pure DCIS treated by BCS alone or with RT.

Methods: The cohort includes all women diagnosed with DCIS in Ontario from 1994-2003 treated with BCS +/- RT; 82% had pathology review. Treatment and outcomes were ascertained through administrative databases and validated by chart review. Cox proportional hazards model was used to evaluate the impact of tumor size (≤10mm,11-25mm, 26-39mm, ≥40mm) on the development of any LR (DCIS or invasive) and invasive LR. The 10 and 15-year LR-free survival (LRFS) and invasive LRFS rates were calculated using the Kaplan-Meier method with differences compared using the log-rank test.

Results: The cohort includes 3262 women with DCIS treated by BCS (N=1635 had RT). Median age at diagnosis was 59 years (IQR 50-68 years). Median follow-up was 13 years (IQR 8-15 years). Distribution of tumor size: 707 (22%) ≤10mm, 524 (16%) 11-25mm, 107 (3%) 26-39mm, 84 (3%) ≥40mm, unable to determine in 1840 (56%). Women with lesions ≥ 40mm were more likely to be ≤50 years of age at diagnosis (p=.02), have high nuclear grade (p&lt;.001), multifocality (p&lt;.001), and positive margins (p&lt;.001) compared to women with smaller lesions. On multivariable analyses adjusted for age and year of diagnosis, tumor size ≥40mm was significantly associated with an increased risk of LR compared to size ≤10mm (HR=2.5, 95%CI:1.64-3.81). Other factors associated with LR were age &lt;50 years (p&lt;.001), omission of RT (p&lt;.001), high nuclear grade (p=.002), and multifocality (p=.0008). Tumor size ≥40mm was not significantly associated with an increased risk of invasive LR (HR=1.68, 95%CI:.94-3.04). Women with tumour size ≥40mm treated with BCS alone had lower 10 and 15 year LRFS (53% and 41%) and invasive LRFS rates (78% and 75%) compared to women with smaller lesions. However, women with larger lesions treated with RT had significantly higher LRFS and invasive LRFS rates

Outcomes by tumour size for women with DCIS treated with BCS with or without RT  ≤10mm N=70711-25mm N=52426-39mm N=107≥40mm N=84p-valueBCS AloneLRFS (%)      10 yr85797053&lt;0.001 15 yr81746741  Invasive LRFS (%)      10 yr928786780.03 15 yr89838375 BCS + RTLRFS (%)      10 yr928874850.01 15 yr86847079  Invasive LRFS (%)      10 yr959492910.27 15 yr90918789 

. There was a significant interaction between tumor size ≥40mm and RT (p=.02).

Conclusions: Women with DCIS lesions ≥40mm treated by BCS alone experience significantly higher risks of LR and invasive LR compared to smaller lesions but this risk can be mitigated with the addition of RT.

Citation Format: Lalani N, Paszat L, Nofech-Mozes S, Sutradhar R, Gu S, Hanna W, Fong C, Miller N, Youngson B, Done SJ, Tuck A, Chang MC, Sengupta S, Jani PA, Bonin M, Rakovitch E. Is breast-conserving therapy effective in women with large ductal carcinoma in situ (DCIS) lesions? A population-based analysis [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-12-02.

Changes of collagen ultrastructure in breast cancer tissue determined by second-harmonic generation double Stokes-Mueller polarimetric microscopy

Second-harmonic generation (SHG) double Stokes-Mueller polarimetric microscopy is applied to study the alteration of collagen ultrastructure in a tissue microarray containing three pathological human breast cancer types with differently overexpressed estrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor 2 (HER2). Kleinman symmetry is experimentally validated in breast tissue for 1028 nm laser wavelength and it has been shown that measurements with only linearly polarized incoming and outgoing states can determine molecular nonlinear susceptibility tensor component ratio, average in-plane orientation of collagen fibers and degree of linear polarization of SHG. Increase in the susceptibility ratio for ER, PgR, HER2 positive cases, reveals ultrastructural changes in the collagen fibers while the susceptibility ratio increase and decrease in degree of linear polarization for ER and PgR positive cases indicate alteration of the ultrastructure and increased disorder of the collagen fibers within each focal volume. The study demonstrates a potential use of polarimetric SHG microscopy for collagen characterization and cancer diagnostics.

Abstract 1534: Amplification of PITPNC1 affects breast cancer progression

Introduction

Identification of driver mutations at single gene level and determination of their respective contribution to the enhanced invasive potential of cancer cells, via expression profiling and functional assays, are indispensable steps toward elucidating breast cancer pathobiology. In our previous array comparative genomic hybridization studies, gain in a region of chromosome 17, 17q23.3-24.3, was frequently observed in invasive duct carcinoma (IDC) patients with lymph node metastasis. Particularly, phosphatidylinositol transfer protein, cytoplasmic 1 (PITPNC1), found in 17q24.2, was associated with higher histological grade, larger tumor size, positive HER2 staining, and poorer prognosis from the analysis of a NKI dataset. PITPNC1 is involved in signal transduction and intracellular lipid transport, and may be an essential part of the epidermal growth factor signaling pathway. Additionally, amplification of PITPNC1 via the loss of microRNA-126 suppression has been implicated in metastatic angiogenesis and colonization. In this study, we aim to assess the role of PITPNC1 in the development of aggressive breast cancer by evaluating its effects on breast cancer progression and invasion.

Method

A total of 21 samples - 13 pure duct carcinoma in situ (DCIS), 8 IDC with or without lymph node metastasis - were used for the preliminary round of this study. Formalin-fixed and paraffin-embedded tissue blocks were microdissected and whole genome amplified using ligation-mediated PCR. Amplified DNA was subjected to quantitative real-time PCR. Copy number alterations of PITPNC1 were calculated with Livak method, using B2M as the reference gene. Lipofectamine transfection overexpressing PITPNC1 in non-invasive MCF-10A and invasive MCF7, MD-MB-231 cell lines was prepared for subsequent in vitro assays. Proliferation and migration capabilities associated with PITPNC1 overexpression is being evaluated using MTT assay and transwell migration assay.

Result

From preliminary qPCR data, PITPNC1 was shown to be amplified in DCIS samples (p = 0.0025) and IDC samples (p = 0.0093). The 95% confidence intervals of fold difference against normal breast tissue control are [7.1, 23.4] and [5.7, 24.4] respectively. PITPNC1 overexpressing MCF-10A cells exhibit a higher proliferation rate in culture compared to controls.

Conclusion

Consistent amplification of PITPNC1 is seen in both DCIS and IDC cases. However, it is still unclear if PITPNC1 amplification is a result of a single mutational event occurring early in cancer progression or a cumulative effect occurring over time. Additional qPCR on paired samples against a pooled control would be necessary to determine its contribution to invasion. The regularity of copy number gain in the PITPNC1 locus and its association with HER2 expression highlight its predictive potential as a novel biomarker for tumorigenesis or invasion.

Citation Format: Peiqi Wang, Ranju Nair, Nisha Kanwar, Grace Cheung, Susan J. Done. Amplification of PITPNC1 affects breast cancer progression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1534.

Abstract P4-03-05: Wide-field optical coherence tomography (WF-OCT) for near real-time, point-of-care assessment of margin status in breast-conserving surgery specimens: Results of a feasibility study at a high-volume single-centre

Wide-Field Optical Coherence Tomography (WF-OCT) is a non-destructive, non-contact light imaging modality capable of label-free visualization of the internal microscopic architecture of breast tissue specimens. Its unique combination of high-resolution imaging in near real-time with tissue penetration depths approaching 2-mm makes it a promising imaging modality for obtaining detailed surgical margin status in breast-conserving surgery (BCS) specimens. A prototype WF-OCT imaging platform developed by Perimeter Medical Imaging, Inc. (Toronto, Canada) has permitted fully-automated, dynamically-focused visualization of margin widths around the intact surfaces of freshly excised BCS specimens. Herein are reported the results of a feasibility study at a high-volume single-centre evaluating the routine use of WF-OCT for sampling of surgical margin status in BCS specimens at the point-of-care.

Methods: Women with biopsy confirmed breast cancer and scheduled for primary BCS were recruited at Princess Margaret Cancer Centre (Toronto, Canada). Standard medical care was not altered. Freshly excised BCS specimens including all lumpectomy samples were imaged by WF-OCT immediately prior to standard histological processing. The system acquired dynamically-focused, hemispherical coverage over two contra-lateral surfaces of the intact BCS specimen within the time constraints of the cold ischemic time window. High-resolution (10 μm) images of the tissue surface down to a 1 to 2-mm depth were obtained. Blinded assessments were performed on image data sets by two clinical readers (surgeon and radiologist) trained on a validated and unrelated data set correlating OCT images with histology slides. The readers were first asked to independently assess margin status using only blinded pre- and intra-operative knowledge (without OCT). Upon completion, the readers were provided OCT images of all scanned surface and similarly asked to assess the margin status with the additional OCT information. These assessments were subsequently evaluated by a breast pathologist comparing the OCT images and corresponding histopathology sections. The added utility of WF-OCT imaging information for margin prediction was studied.

Results: [Pending study completion in August 2015]. Through accurate correlation with the histopathologic gold standard, OCT demonstrated capability to differentiate tissue microstructures, including: distinctive patterns for adipose tissue, fibrous stroma, breast lobules and ducts, cysts and microcysts, as well as in-situ and invasive carcinomas.

Implications: The fully-automated WF-OCT imaging platform can integrate conveniently into standard pathological processing workflows to provide comprehensive sampling of surgical margin status in BCS specimens at the point-of-care. Clinical readers from surgical and radiological backgrounds can be trained to competently interpret WF-OCT images of BCS specimens for accurate prediction margin status. The implementation of WF-OCT at the point-of-care for routine surgical margin assessments will be further explored in future clinical trials.

Citation Format: Valic MS, Leong WL, Done SJ, Wilson BC, Kulkarni S, McCready DR, Niu CJ, Atachia Y, Munro EA, Rempel D. Wide-field optical coherence tomography (WF-OCT) for near real-time, point-of-care assessment of margin status in breast-conserving surgery specimens: Results of a feasibility study at a high-volume single-centre. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-03-05.

Digital versus screen-film mammography: impact of mammographic density and hormone therapy on breast cancer detection

Most studies that have examined the effects of mammographic density and hormone therapy use on breast cancer detection have included screen-film mammography. This study further examines this association in post-menopausal women screened by digital mammography. Approved by the University of Toronto Research Ethics Board, this study identified 688,418 women of age 50-74 years screened with digital or screen-film mammography from 2008 to 2009 within the Ontario Breast Screening Program. Of 2993 eligible women with invasive breast cancer, 2450 were contacted and 1421 participated (847 screen-film mammography, 574 digital direct radiography). Mammographic density was measured by study radiologists using the standard BI-RADS classification system and by a computer-assisted method. Information on hormone therapy use was collected by a telephone-administered questionnaire. Logistic regression and two-tailed tests for significance evaluated associations between factors and detection method by mammography type. Women with >75 % radiologist-measured mammographic density compared to those with <25 % were more likely to be diagnosed with an interval than screen-detected cancer, with the difference being greater for those screened with screen-film (OR = 6.40, 95 % CI 2.30-17.85) than digital mammography (OR = 2.41, 95 % CI 0.67-8.58) and aged 50-64 years screened with screen-film mammography (OR = 10.86, 95 % CI 2.96-39.57). Recent former hormone therapy users were also at an increased risk of having an interval cancer with the association being significant for women screened with digital mammography (OR = 2.08, 95 % CI 1.17-3.71). Breast screening using digital mammography lowers the risk of having an interval cancer for post-menopausal women aged 50-64 with greater mammographic density.

Ras Signaling Is a Key Determinant for Metastatic Dissemination and Poor Survival of Luminal Breast Cancer Patients

Breast cancer is associated with alterations in a number of growth factor and hormone-regulated signaling pathways. Mouse models of metastatic breast cancer typically feature mutated oncoproteins that activate PI3K, Stat3, and Ras signaling, but the individual and combined roles of these pathways in breast cancer progression are poorly understood. In this study, we examined the relationship between oncogenic pathway activation and breast cancer subtype by analyzing mouse mammary tumor formation in which each pathway was activated singly or pairwise. All three oncogenes showed cooperation during primary tumor formation, but efficient dissemination was only dependent on Ras. In addition, transcriptional profiling demonstrated that Ras induced adenocarcinomas with molecular characteristics related to human basal-like and HER2(+) tumors. In contrast, Ras combined with PIK3CA(H1047R), an oncogenic mutant linked to ERα(+)/luminal breast cancer in humans, induced metastatic luminal B-like tumors. Consistent with these data, elevated Ras signaling was associated with basal-like and HER2(+) subtype tumors in humans and showed a statistically significant negative association with estrogen receptor (ER) signaling across all breast cancer. Despite this, there are luminal tumors with elevated Ras signaling. Importantly, when considered as a continuous variable, Ras pathway activation was strongly linked to reduced survival of patients with ERα(+) disease independent of PI3K or Stat3 activation. Therefore, our studies suggest that Ras activation is a key determinant for dissemination and poor prognosis of ERα(+)/luminal breast cancer in humans, and hormone therapy supplemented with Ras-targeting agents may be beneficial for treating this aggressive subtype.

Digital Compared with Screen-Film Mammography: Measures of Diagnostic Accuracy among Women Screened in the Ontario Breast Screening Program

PURPOSE

To compare measures of diagnostic accuracy between large concurrent cohorts of women screened with digital computed radiography (CR), direct radiography (DR), and screen-film mammography (SFM).

MATERIALS AND METHODS

This study was approved by the University of Toronto Research Ethics Board; informed consent was not required. Three concurrent cohorts of women aged 50-74 years who were screened from 2008-2009 in the Ontario Breast Screening Program with SFM (487,334 screening examinations, 403,688 women), DR (254,758 screening examinations, 220,520 women), or CR (74,140 screening examinations, 64,210 women) were followed for 2 years or until breast cancer diagnosis. Breast cancers were classified as screening-detected or interval on the basis of the woman's final screening and assessment results. Interval cancer rate (per 10 000 negative screening examinations), sensitivity, and specificity were compared across the cohorts by using mixed-effects logistic regression analysis.

RESULTS

Interval cancer rates were higher, although not significantly so, for CR (15.2 per 10,000; 95% confidence interval [CI]: 12.8, 17.8) and were similar for DR (13.7 per 10,000; 95% CI: 12.4, 15.0) compared with SFM (13.0 per 10,000; 95% CI: 12.1, 13.9). For CR versus SFM, specificity was similar while sensitivity was significantly lower (odds ratio [OR] = 0.62; 95% CI: 0.47, 0.83; P = .001), particularly for invasive cancers detected at a rescreening examination, for women with breast density of less than 75%, for women with no family history, and for postmenopausal women. For DR versus SFM, sensitivity was similar while specificity was lower (OR = 0.92; 95% CI: 0.87, 0.98; P = .01), particularly for rescreening examinations, for women aged 60-74 years, for women with breast density of less than 75%, for women with a family history, and for women who were postmenopausal.

CONCLUSION

Given the 38% lower sensitivity of CR imaging systems compared with SFM, programs should assess the continued use of this technology for breast screening.

Abstract 3381: Standardizing the analysis of Ki-67 immunohistochemical assays

Intro

Immunohistochemical assays of the proliferation marker, Ki-67, have been associated with poorer clinical prognosis in breast cancer. However, a high degree of inconsistency in scores has been demonstrated in inter-laboratory and intra-laboratory Ki-67 positivity scorings, this has limited its potential in clinical practice. In this study, we aim to find a more consistent method for scoring Ki-67 positivity among malignant breast tumours.

Methods

Six Tissue Microarray (TMA) blocks were sectioned and immunohistochemistry was performed with Anti-Ki-67 antibody. Slides were then evaluated and Ki-67 positive cells in invasive breast carcinoma were scored as a percent positivity manually by a trained analyst with random sample quality assurance (QA) by trained pathologists. This was used as the standard benchmark for the experiment as it has been correlated successfully with clinical outcome. Successively, the same six slides were then annotated on Aperio ePathology software by two observers with different levels of pathology training and experience. The annotated regions were analyzed for Ki-67 positivity with Aperio ePathology software on UHN BioBank servers. The computer analyzed scores were compared to the manual benchmark scores.

Results

The difference between computer-analyzed and manual-scores were relatively large, Observer-A-annotated-computer-analyzed vs. analyst-manual-scores had a difference of 4.23% to 16.96%, while Observer-B-annotated-computer-analyzed vs. analyst-manual-scores had a difference of 7.13% to 15.03%. Interestingly, Observer-A-annotated-computer-analyzed vs. Observer-B-annotated-computer-analyzed scores only had a difference of 0.49% to 2.91%. Pearson Correlation was calculated for all samples on a case-by-case basis and we found there to be a linear correlation of 0.564, with a P-value of 3.6082×10-8, between the computer scores and the manual scores; suggesting significant correlation between the computer scores and the manual score.

Conclusion

A significant linear correlation has been observed between the computer score and the manual score. However, while the data does not seem to support the idea that a semi-automatic method of computer scoring will replace analyst manual scoring, most of the large contributing variables have been identified. We plan in the next steps of the project to continue to decrease the effects of such variables. It is interesting that the inter-observer computer score displayed a minimal amount of difference, again with the variables identified. This could signify a more consistent method of Ki-67 scoring. Further experiments will be conducted to continue to reduce the variables and optimize the system to gain similar performance as manual scoring. Hopefully in the near future, computerized immunohistochemical analysis can replace the tedious task of manual scoring.

Citation Format: Tian Yu Liu, Trillium Chang, Adewunmi Adeoye, Willa Shi, Sheng-Ben Liang, Dianne Chadwick, Michael H.A. Roehrl, Naomi Miller, Fei-Fei Liu, Susan J. Done. Standardizing the analysis of Ki-67 immunohistochemical assays. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3381. doi:10.1158/1538-7445.AM2015-3381

Close or positive resection margins are not associated with an increased risk of chest wall recurrence in women with DCIS treated by mastectomy: a population-based analysis

Mastectomy is effective treatment for ductal carcinoma in situ (DCIS) but some women will develop chest wall recurrence. Most chest wall recurrences that develop after mastectomy are invasive cancer and are associated with poorer prognosis. Past studies have been unable to identify factors predictive of chest wall recurrence. Therefore, it remains unclear if a subset exists of women with DCIS treated by mastectomy experience a high rate of recurrence in whom more aggressive treatment may be of benefit. We report outcomes of all women in Ontario (N = 1,546) diagnosed with pure DCIS from 1994 to 2003 treated with mastectomy without radiotherapy and evaluate factors associated with the development of chest wall recurrence. Treatments and outcomes were validated by chart review. Proportional differences were compared using Chi square analyses. Survival analyses were used to study the development of chest wall recurrence in relation to patient and tumor characteristics. Median follow-up was 10.1 years. Median age was 57.1 years. 36 patients (2.3%) developed chest wall recurrence. The 10-year actuarial chest wall recurrence-free survival rates and invasive chest wall recurrence-free survival rates were 97.6 and 98.6%, respectively. There was no difference in cumulative 10 year rates of chest wall recurrence by age at diagnosis (<40 years = 5.2%, 40–44 years = 1.3%, 45–50 years = 2.9%, >50 years = 2.1%; p = 0.19), nuclear grade (high = 3.0%, intermediate = 1.4%, low = 1.0%, unreported = 2.5%; p = 0.41), or among women with close or positive resection margins (positive = 3.0%, 2 mm or less = 1.4%, >2 mm = 1.5%, unreported = 2.8%; p = 0.51). On univariate and multivariable analysis, none of the factors were significantly associated with the development of chest wall recurrence. In this population cohort, individuals treated by mastectomy experienced low rates of chest wall recurrence. We did not identify a subset of patients with a high rate of chest wall recurrence, including those with positive margins.

Identification of a Low-Risk Luminal A Breast Cancer Cohort That May Not Benefit From Breast Radiotherapy

PURPOSE

To determine the prognostic and predictive value of intrinsic subtyping by using immunohistochemical (IHC) biomarkers for ipsilateral breast relapse (IBR) in participants in an early breast cancer randomized trial of tamoxifen with or without breast radiotherapy (RT).

PATIENTS AND METHODS

IHC analysis of estrogen receptor, progesterone receptor, human epidermal growth factor receptor 2 (HER2), cytokeratin 5/6, epidermal growth factor receptor, and Ki-67 was conducted on 501 of 769 available blocks. Patients were classified as luminal A (n = 265), luminal B (n = 165), or high-risk subtype (luminal HER2, n = 22; HER2 enriched, n = 13; basal like, n = 30; or triple-negative nonbasal, n = 6). Median follow-up was 10 years.

RESULTS

Classification by subtype was prognostic for IBR (10-year estimates: luminal A, 5.2%; luminal B, 10.5%; high-risk subtypes, 21.3%; P < .001). Luminal subtypes seemed to derive less benefit from RT (luminal A hazard ratio [HR], 0.40; luminal B HR, 0.51) than high-risk subtypes (HR, 0.13); however, the overall subtype-treatment interaction term was not significant (P = .26). In an exploratory analysis of women with clinical low-risk (age older than 60 years, T1, grade 1 or 2) luminal A tumors (n = 151), 10-year IBR was 3.1% versus 11.8% for the high-risk cohort (n = 341; P = .0063). Clinical low-risk luminal A patients had a 10-year IBR of 1.3% with tamoxifen versus 5.0% with tamoxifen plus RT (P = .42). Multivariable analysis showed that RT (HR, 0.31; P < .001), clinical risk group (HR, 2.2; P = .025), and luminal A subtype (HR, 0.25; P < .001) were significantly associated with IBR.

CONCLUSION

IHC subtyping was prognostic for IBR but was not predictive of benefit from RT. Further studies may validate the exploratory finding of a low-risk luminal A group who may be spared breast RT.

Changes in insulin receptor signaling underlie neoadjuvant metformin administration in breast cancer: a prospective window of opportunity neoadjuvant study

INTRODUCTION

The antidiabetic drug metformin exhibits potential anticancer properties that are believed to involve both direct (insulin-independent) and indirect (insulin-dependent) actions. Direct effects are linked to activation of AMP-activated protein kinase (AMPK) and an inhibition of mammalian target of rapamycin mTOR signaling, and indirect effects are mediated by reductions in circulating insulin, leading to reduced insulin receptor (IR)-mediated signaling. However, the in vivo impact of metformin on cancer cell signaling and the factors governing sensitivity in patients remain unknown.

METHODS

We conducted a neoadjuvant, single-arm, "window of opportunity" trial to examine the clinical and biological effects of metformin on patients with breast cancer. Women with untreated breast cancer who did not have diabetes were given 500 mg of metformin three times daily for ≥2 weeks after diagnostic biopsy until surgery. Fasting blood and tumor samples were collected at diagnosis and surgery. Blood glucose and insulin were assayed to assess the physiologic effects of metformin, and immunohistochemical analysis of tumors was used to characterize cellular markers before and after treatment.

RESULTS

Levels of IR expression decreased significantly in tumors (P = 0.04), as did the phosphorylation status of protein kinase B (PKB)/Akt (S473), extracellular signal-regulated kinase 1/2 (ERK1/2, T202/Y204), AMPK (T172) and acetyl coenzyme A carboxylase (S79) (P = 0.0001, P < 0.0001, P < 0.005 and P = 0.02, respectively). All tumors expressed organic cation transporter 1, with 90% (35 of 39) exhibiting an Allred score of 5 or higher.

CONCLUSIONS

Reduced PKB/Akt and ERK1/2 phosphorylation, coupled with decreased insulin and IR levels, suggest insulin-dependent effects are important in the clinical setting. These results are consistent with beneficial anticancer effects of metformin and highlight key factors involved in sensitivity, which could be used to identify patients with breast cancer who may be responsive to metformin-based therapies.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT00897884. Registered 8 May 2009.

Glutathione and thioredoxin antioxidant pathways synergize to drive cancer initiation and progression

Controversy over the role of antioxidants in cancer has persisted for decades. Here, we demonstrate that synthesis of the antioxidant glutathione (GSH), driven by GCLM, is required for cancer initiation. Genetic loss of Gclm prevents a tumor's ability to drive malignant transformation. Intriguingly, these findings can be replicated using an inhibitor of GSH synthesis, but only if delivered prior to cancer onset, suggesting that at later stages of tumor progression GSH becomes dispensable potentially due to compensation from alternative antioxidant pathways. Remarkably, combined inhibition of GSH and thioredoxin antioxidant pathways leads to a synergistic cancer cell death in vitro and in vivo, demonstrating the importance of these two antioxidants to tumor progression and as potential targets for therapeutic intervention.

Identification of genomic signatures in circulating tumor cells from breast cancer

Levels of circulating tumor cells (CTCs) in blood have prognostic value in early and metastatic breast cancer. CTCs also show varying degrees of concordance with molecular markers of primary tumors they originate from. It is expected that individual cells reflect the heterogeneity and evolution of tumor cells as they acquire new functions and differential responses to chemotherapy. However, a degree of commonality is also plausible, highlighting alterations that allow tumor cells to perform CTC-defining activities such as invasion and intravasation. Using a matched tumor-normal approach, we performed high-resolution copy number profiling of CTCs from breast cancer to identify occult changes occurring during progression to metastasis. We identified a signature of recurrent gain in CTCs, consisting of 90 minimal common regions (MCRs) of copy number gain. These were predominantly found across chromosome 19 and were identified at low frequencies (3-4%) in 787 primary breast carcinomas examined. CTC genomic signatures clustered into two groups independent of subtype: a dormancy-related signature with 16 MCRs (AKT2, PTEN, CADM2); and a tumor-aggressiveness related signature with 358 MCRs (ANGPTL4, BSG, MIR-373). There were two MCRs in common between the groups on 19q13 and 21q21, containing genes involved in resistance to anoikis, TGFβ-signaling and metastasis (TFF3, LTBP4, NUMBL). Furthermore, a region harboring the ERBB2 gene was gained in a majority of patients. Regions 20q13 and 15q24 were associated with distant metastasis. The distinctiveness of CTC signatures highlights cell populations with different functional or metastatic potential. Such novel targets could help to specifically identify and block dissemination.

B7-H4 expression by nonhematopoietic cells in the tumor microenvironment promotes antitumor immunity

The B7 family plays a critical role in both positive and negative regulation of immune responses by engaging a variety of receptors on lymphocytes. Importantly, blocking coinhibitory molecules using antibodies specific for CTLA-4 and PD-1 enhances tumor immunity in a subset of patients. Therefore, it is critical to understand the role of different B7 family members since they may be suitable therapeutic targets. B7-H4 is another member that inhibits T-cell function, and it is also upregulated on a variety of tumors and has been proposed to promote tumor growth. Here, we investigate the role of B7-H4 in tumor development and show that B7-H4 expression inhibits tumor growth in two mouse models. Furthermore, we show that B7-H4 expression is required for antitumor immune responses in a mouse model of mammary tumorigenesis. We found that the expression levels of B7-H4 correlate with MHC class I expression in both mouse and human samples. We show that IFNγ upregulates B7-H4 expression on mouse embryo fibroblasts and that the upregulation of B7-H4 on tumors is dependent on T cells. Notably, patients with breast cancer with increased B7-H4 expression show a prolonged time to recurrence. These studies demonstrate a positive role for B7-H4 in promoting antitumor immunity.

Abstract 4968: Msi2 directly linked to Hedgehog and Wnt signaling in non-triple negative breast cancer

Introduction: Previously, we have shown that a gain on 17q22.24.2 was a predictor of invasiveness when found in duct carcinoma in situ (DCIS) and of nodal metastasis when found in invasive duct carcinoma (IDC). Within this amplicon, we have identified a gene that is a likely driver of breast tumorigenesis and progression: Musashi homolog 2 (Msi2). Msi2 has a functional role in neural stem cell maintenance and regulation of hematopoietic stem cells. Previously, Msi2 has been implicated in Notch and Hedgehog signaling in leukemia, and here we link Msi2 to an increase in Wnt activation.

Methodology: To understand the expression of Msi2 in patient tissue, tissue microarrays (TMAs) containing 232 breast cancers were analyzed by immunohistochemistry. MDA-MB-231 and MCF7 cells expressing Msi2-GFP and GFP clones were plated on transwells to examine cell migration and invasiveness. Proliferation was analyzed by the MTS assay. TOP-FOP and Gli1 Luciferase assays were used to confirm activation of Hedgehog and Wnt signaling. Western blots were used to assess total beta-catenin levels in the cell lines. Analysis of publicly available expression microarray databases and RT-PCR of the over-expression cell lines validated the proposed mechanism of action.

Results: Tissue microarrays confirmed that Allred scores for Msi2 significantly correlated with grade, size stage, and non-triple negative receptor status. Over-expression of Msi2, in MDA-MB-231 (triple negative) and MCF7 (luminal cell type with epithelial morphology) cell lines, caused an increase in proliferation, migration and invasion. The knockdowns demonstrated the reverse effect. As determined by the TOP-FOP luciferase assay and RT-PCR, Msi2 leads to increased signaling of Hedgehog and Wnt. Furthermore, Msi2-mediated activation of Wnt occurs independently of total beta-catenin levels. Microarray analysis of breast cancer cell lines and patients' tumors supports this mechanism of action for Msi2 in non-triple negative cell lines (as assessed by Pearson's correlation coefficient of pathway interactions).

Conclusion: When overexpressed in a cancerous cell system in vitro, Msi2 levels correlate with increased migratory and invasive capabilities. Furthermore, its implication in Notch, Hedgehog, and Wnt Signaling, make Msi2 a likely driver of the 17q22-24.2 amplicon in breast cancer. This study furthers our understanding of Msi2, and hints at the possibility that Msi2 plays a more significant role in cellular events and tumorigenesis than previously thought.

Citation Format: Moustafa Abdalla, Nisha Kanwar, Yanglong Zhu, Ranju Nair, Bruce J. Youngson, Naomi A. Miller, Tianyu Liu, Susan J. Done. Msi2 directly linked to Hedgehog and Wnt signaling in non-triple negative breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4968. doi:10.1158/1538-7445.AM2014-4968

Long-term outcomes of hypofractionation versus conventional radiation therapy after breast-conserving surgery for ductal carcinoma in situ of the breast

PURPOSE

Whole-breast radiation therapy (XRT) after breast-conserving surgery (BCS) for ductal carcinoma in situ (DCIS) may decrease the risk of local recurrence, but the optimal dose regimen remains unclear. Past studies administered 50 Gy in 25 fractions (conventional); however, treatment pattern studies report that hypofractionated (HF) regimens (42.4 Gy in 16 fractions) are frequently used. We report the impact of HF (vs conventional) on the risk of local recurrence after BCS for DCIS.

METHODS AND MATERIALS

All women with DCIS treated with BCS and XRT in Ontario, Canada from 1994 to 2003 were identified. Treatment and outcomes were assessed through administrative databases and validated by chart review. Survival analyses were performed. To account for systematic differences between women treated with alternate regimens, we used a propensity score adjustment approach.

RESULTS

We identified 1609 women, of whom 971 (60%) received conventional regimens and 638 (40%) received HF. A total of 489 patients (30%) received a boost dose, of whom 143 (15%) received conventional radiation therapy and 346 (54%) received HF. The median follow-up time was 9.2 years. The median age at diagnosis was 56 years (interquartile range [IQR], 49-65 years). On univariate analyses, the 10-year actuarial local recurrence-free survival was 86% for conventional radiation therapy and 89% for HF (P=.03). On multivariable analyses, age <45 years (hazard ratio [HR] = 2.4; 95% CI: 1.6-3.4; P<.0001), high (HR=2.9; 95% CI: 1.2-7.3; P=.02) or intermediate nuclear grade (HR=2.7; 95% CI: 1.1-6.6; P=.04), and positive resection margins (HR=1.4; 95% CI: 1.0-2.1; P=.05) were associated with an increased risk of local recurrence. HF was not significantly associated with an increased risk of local recurrence compared with conventional radiation therapy on multivariate analysis (HR=0.8; 95% CI: 0.5-1.2; P=.34).

CONCLUSIONS

The risk of local recurrence among individuals treated with HF regimens after BCS for DCIS was similar to that among individuals treated with conventional radiation therapy.

Digital compared to screen-film mammography: breast cancer prognostic features in an organized screening program

Our previous study found cancer detection rates were equivalent for direct radiography compared to screen-film mammography, while rates for computed radiography were significantly lower. This study compares prognostic features of invasive breast cancers by type of mammography. Approved by the University of Toronto Research Ethics Board, this study identified invasive breast cancers diagnosed among concurrent cohorts of women aged 50-74 screened by direct radiography, computed radiography, or screen-film mammography from January 1, 2008 to December 31, 2009. During the study period, 816,232 mammograms were performed on 668,418 women, and 3,323 invasive breast cancers were diagnosed. Of 2,642 eligible women contacted, 2,041 participated (77.3 %). The final sample size for analysis included 1,405 screen-detected and 418 interval cancers (diagnosed within 24 months of a negative screening mammogram). Polytomous logistic regression was performed to evaluate the association between tumour characteristics and type of mammography, and between tumour characteristics and detection method. Odds ratios (OR) and 95 % confidence intervals (CI) were recorded. Cancers detected by computed radiography compared to screen-film mammography were significantly more likely to be lymph node positive (OR 1.94, 95 %CI 1.01-3.73) and have higher stage (II:I, OR 2.14, 95 %CI 1.11-4.13 and III/IV:I, OR 2.97, 95 %CI 1.02-8.59). Compared to screen-film mammography, significantly more cancers detected by direct radiography (OR 1.64, 95 %CI 1.12-2.38) were lymph node positive. Interval cancers had worse prognostic features compared to screen-detected cancers, irrespective of mammography type. Screening with computed radiography may lead to the detection of cancers with a less favourable stage distribution compared to screen-film mammography that may reflect a delayed diagnosis. Screening programs should re-evaluate their use of computed radiography for breast screening.

Validation of the prognostic gene portfolio, ClinicoMolecular Triad Classification, using an independent prospective breast cancer cohort and external patient populations

Introduction

Using genome-wide expression profiles of a prospective training cohort of breast cancer patients, ClinicoMolecular Triad Classification (CMTC) was recently developed to classify breast cancers into three clinically relevant groups to aid treatment decisions. CMTC was found to be both prognostic and predictive in a large external breast cancer cohort in that study. This study serves to validate the reproducibility of CMTC and its prognostic value using independent patient cohorts.

Methods

An independent internal cohort (n = 284) and a new external cohort (n = 2,181) were used to validate the association of CMTC between clinicopathological factors, 12 known gene signatures, two molecular subtype classifiers, and 19 oncogenic signalling pathway activities, and to reproduce the abilities of CMTC to predict clinical outcomes of breast cancer. In addition, we also updated the outcome data of the original training cohort (n = 147).

Results

The original training cohort reached a statistically significant difference (p < 0.05) in disease-free survivals between the three CMTC groups after an additional two years of follow-up (median = 55 months). The prognostic value of the triad classification was reproduced in the second independent internal cohort and the new external validation cohort. CMTC achieved even higher prognostic significance when all available patients were analyzed (n = 4,851). Oncogenic pathways Myc, E2F1, Ras and β-catenin were again implicated in the high-risk groups.

Conclusions

Both prospective internal cohorts and the independent external cohorts reproduced the triad classification of CMTC and its prognostic significance. CMTC is an independent prognostic predictor, and it outperformed 12 other known prognostic gene signatures, molecular subtype classifications, and all other standard prognostic clinicopathological factors. Our results support further development of CMTC portfolio into a guide for personalized breast cancer treatments.

Age at diagnosis predicts local recurrence in women treated with breast-conserving surgery and postoperative radiation therapy for ductal carcinoma in situ: a population-based outcomes analysis

PURPOSE

The main goal of treating ductal carcinoma in situ (dcis) is to prevent the development of invasive breast cancer. Most women are treated with breast-conserving surgery (bcs) and radiotherapy. Age at diagnosis may be a risk factor for recurrence, leading to concerns that additional treatment may be necessary for younger women. We report a population-based study of women with dcis treated with bcs and radiotherapy and an evaluation of the effect of age on local recurrence (lr).

METHODS

All women diagnosed with dcis in Ontario from 1994 to 2003 were identified. Treatments and outcomes were collected through administrative databases and validated by chart review. Women treated with bcs and radiotherapy were included. Survival analyses were performed to evaluate the effect of age on outcomes.

RESULTS

We identified 5752 cases of dcis; 1607 women received bcs and radiotherapy. The median follow-up was 10.0 years. The 10-year cumulative lr rate was 27% for women younger than 45 years, 14% for women 45-50 years, and 11% for women more than 50 years of age (p < 0.0001). The 10-year cumulative invasive lr rate was 22% for women younger than 45 years, 10% for women 45-50 years, and 7% for women more than 50 years of age (p < 0.0001). On multivariate analyses, young age (<45 years) was significantly associated with lr and invasive lr [hazard ratio (hr) for lr: 2.6; 95% confidence interval (ci): 1.9 to 3.7; p < 0.0001; hr for invasive lr: 3.0; 95% ci: 2.0 to 4.4; p < 0.0001]. An age of 45-50 years was also significantly associated with invasive lr (hr: 1.6; 95% ci: 1.0 to 2.4; p = 0.04).

CONCLUSIONS

Age at diagnosis is a strong predictor of lr in women with dcis after treatment with bcs and radiotherapy.

Abstract PD6-2: Identifying genomic signatures in circulating tumour cells from breast cancer

Introduction: Levels of circulating tumor cells (CTCs) in blood have prognostic value in early and metastatic breast cancer. CTCs also show varying degrees of concordance with the primary tumors they originate from. This is indicative of heterogeneity and dynamic evolution of tumor cells as they acquire new functionality. Profiling of CTCs will help identify occult changes occurring in breast cancer cells during progression to metastasis. CTCs could contain genomic alterations that define them as metastatic intermediates, and may be identified in primary tumors at low frequencies, as an aggressive component that responds differentially to chemotherapy.

Methodology: CTCs and matched normal white blood cells were isolated from the blood of 17/40 chemonaive breast cancer patients. Copy number analysis was performed with the Affymetrix Genome-Wide Human SNP 6.0 array using a paired tumor-normal approach. Minimal common regions (MCRs) of gain were extrapolated, followed by unsupervised clustering. Associations between MCRs and breast cancer subtypes; as well as metastasis, were identified using PLINK analysis. A TCGA copy number dataset of 787 invasive primary breast tumors was queried for frequency of CTC-like alterations.

Results: CTC genomic profiles clustered into 2 groups independent of subtype: a heterogeneous group with 11 MCRs (genes amplified: AKT2, SMAD2), and a more homogeneous group with 400 MCRs, of which 55 were on chromosome 19 (genes amplified: ANGPTL4, BSG). There were 2 MCRs in common, on 19q13 and 21q; containing genes involved in resistance to anoikis, TGFb signaling and metastasis (TFF3, LTBP4, NUMBL). A 1.2Mb region harboring the ERBB2 gene was gained in 15/17 samples. Patients with distant metastases and younger age (&lt;50) clustered together. Region 19q13 was associated with HER2 positivity and triple negative status of matched primary tumors. Regions 20q13 and 15q34 were associated with distant metastases. CTC-like gains were identified at low frequencies of 3-4% in 787 primary tumors (genes amplified: CCNE1, KLK7-14, MIR371-373).

Conclusions: The genomic profiles of CTCs clustered into 2 groups: a heterogeneous group with minimal alterations that may be sufficient for dissemination; and a more homogeneous group with extensive alteration, that could define those CTCs that may be en route to the next steps of metastasis. There were only 2 MCRs in common between the groups that highlights an important common point of evolution of CTC genomes. CTCs also appear to be more homogeneous for certain gains, specifically on chromosome 19, which may allow for CTC-like functionality such as invasion, intravasation, survival or chemo-resistance. Furthermore, CTC-like gains were identifiable at low frequencies within a dataset of primary breast tumors. We are currently using multispectral-FISH to examine the most frequent combinations of CTC-like gains in primary breast tumors pre- and post-chemotherapy. It is possible that CTC-like alterations, even if present only focally, could confer a more aggressive course of progression to metastasis. More importantly, these cells could be targeted to stop their spread to distant sites.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD6-2.

Role of Nek2 on centrosome duplication and aneuploidy in breast cancer cells

Breast cancer is the most common solid tumor and the second most common cause of death in women. Despite a large body of literature and progress in breast cancer research, many molecular aspects of this complex disease are still poorly understood, hindering the design of specific and effective therapeutic strategies. To identify the molecules important in breast cancer progression and metastasis, we tested the in vivo effects of inhibiting the functions of various kinases and genes involved in the regulation/modulation of the cytoskeleton by downregulating them in mouse PyMT mammary tumor cells and human breast cancer cell lines. These kinases and cytoskeletal regulators were selected based on their prognostic values for breast cancer patient survival. PyMT tumor cells, in which a selected gene was stably knocked down were injected into the tail veins of mice, and the formation of tumors in the lungs was monitored. One of the several genes found to be important for tumor growth in the lungs was NIMA-related kinases 2 (Nek2), a cell cycle-related protein kinase. Furthermore, Nek2 was also important for tumor growth in the mammary fat pad. In various human breast cancer cell lines, Nek2 knockdown induced aneuploidy and cell cycle arrest that led to cell death. Significantly, the breast cancer cell line most sensitive to Nek2 depletion was of the triple negative breast cancer subtype. Our data indicate that Nek2 has a pivotal role in breast cancer growth at primary and secondary sites, and thus may be an attractive and novel therapeutic target for this disease.

Abstract 1204: Heterogeneity within triple-negative breast cancer (TNBC)

Background: TNBC refers to those breast cancers which are negative for ER, PR and Her2/neu overexpression, thereby unsuitable for hormone and trastuzumab therapy. Although TNBC overlap with basal-like breast cancers, these terms are not synonymous. We decided, in a single institution cohort, to develop a better understanding of the types of tumors that make up TNBC

Materials and Methods: We carried out a clinicopathological study of a cohort of 192 patients diagnosed with TNBC at the University Health Network in 2007. Patient biodata, clinical and histopathological information of proven prognostic importance was retrieved from the records. Tissue microarrays were constructed from duplicate 0.6mm cores of representative tumour tissue and stained with 9 antibodies according to recommended protocols. The TMA slides were interpreted using the Allred method except for the Ki67 staining which was interpreted by the visual estimate method of assessing proportion of nuclei taking up stains. Results were tabulated and summary statistics was done to determine proportions.

Results: The age-range is 28 - 99 years. The median and modal age group was 50 -59 years. 70.3% of the patients are aged between 40 and 69 years at the time of diagnosis. The tumour size range was 0.6cm to 16 cm. 41.67% are pT1, 51.04% are pT2 while 6.8% are pT3. Four patients had T4 tumor with skin and nipple involvement. The diagnosis was predominantly invasive ductal carcinoma (IDC) in 84.9% of patients. Metaplastic carcinoma (10.4%), pleomorphic lobular carcinoma (1.5%), and single cases of invasive lobular carcinoma (ILC), tubular, apocrine and poorly differentiated carcinoma were seen. DCIS is a prominent feature in 26.6% of the cases. The number of lymph nodes identified ranged from 0 - 46. 59.90% were in pN0 category, 16.7% in the pN1 category, pN2 - 8.3%, and 15.1% in pN3 category. Extra-nodal metastasis at diagnosis was found in 7.3% of patients. The tumour grade: Grade I - 1.55%, Grade II - 13.47% and Grade III 84.97%. CD44 was positive in 17.71%, p63 - 4.17%, p53 - 51.56%, e-cadherin - 81.77%, Vimentin - 77.60%, Cyclin D1 - 22.40%, BCL-2 - 19.27%, and androgen receptor (AR) - 5.73%. 43.75% of cases show proliferation rates of ≥15%, while 26.04% have proliferation rates of between 5% and ≤14%.

Conclusion: While a large proportion of TNBCs show a high proliferation (Ki67, Cyclin D1 and grade III), a substantial number did not show this. This study provides clues to support the current hypothesis that several mechanisms drive the carcinogenesis of TNBC, with a heterogeneous pattern of biomarker expression. Further investigation is needed to better understand the factors driving the development and progression of the different types of TNBC.

Citation Format: Adewunmi O. Adeoye, Bruce J. Youngson, Naomi Miller, Susan J. Done. Heterogeneity within triple-negative breast cancer (TNBC). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1204. doi:10.1158/1538-7445.AM2013-1204

Abstract 5116: The calcium channel subunit CACNG4 plays a role in breast cancer metastasis

Introduction: Previously, we used aCGH to analyze genomic alterations in primary breast tumors with and without lymph node (LN) metastasis. A significant correlation was found between gain of chromosome 17q24 and LN metastasis. Selected genes including L-type calcium channel voltage dependent gamma subunit 4 (CACNG4) were further validated for increased protein expression in invasive breast tumors. CACNG4 is involved in calcium channel regulation in excitable cells of muscles and the brain. It is the only gamma subunit that also shows expression in non-excitable cells, such as glial and intestinal epithelial cells, suggestive of additional functions. It is over-expressed in glioblastoma multiforme cell lines resistant to EGFR inhibitors. Breast cancer gene expression datasets (NKI and IPC) identified an association of CACNG4 expression with LN metastasis and ER positivity. In the present study, we characterized CACNG4 in breast cancer with particular attention to its metastasis-related ability.

Methodology: RNA interference was used for knockdown studies in cell lines followed by cell migration, invasion, aggregation and adhesion assays. Intracellular calcium influx in response to calcium channel agonists and antagonists was measured using the Fluo-4 calcium indicator dye.

Results: CACNG4 showed variable expression across a panel of breast cancer cell lines. MCF10A (a non malignant cell line) does not express CACNG4, while it is highly expressed in ER positive cell lines (MCF7, MDA-MB-361, CAMA1) and lower in EGFR high cell lines (MDA-MB-468 and MDA-MB-231). CACNG4 knockdown inhibited cell migration and invasion in MCF7 and MDA-MB-231 cells. Conversely, cell adhesion and cell-cell aggregation was increased. RT-PCR revealed an inverse relation between CACNG4 expression and PKC-zeta specifically, which is involved in tight junction formation and shows low expression in breast, prostate and renal cancers. Thus, CACNG4 may play a role in de-adhesion and cell dissemination during metastasis. Blocking calcium channels with amlopidine had an anti-proliferative affect. Serum stimulation of EGFR high cell lines resulted in calcium influx, that was blocked in a dosage dependent manner with amlodipine, and synergistically blocked further with the EGFR specific tyrosine kinase inhibitor tryphostin AG1478. Knockdown of CACNG4 resulted in increased calcium influx suggesting a role in keeping the channel closed. Cells also showed resistance to amlodipine, requiring higher doses to block calcium influx.

Conclusions: L-type channels are active in non-excitable breast cancer cells, and are affected by EGFR activity. CACNG4 maintains these channels in a closed state, modulating calcium influx, and inhibiting PKC-zeta expression which may result in metastatic function. The ability of calcium channel blockers to target channels in a CACNG4 dependent manner suggests novel treatment possibilities for invasive breast cancer.

Citation Format: Nisha Kanwar, Ranju Nair, Dong-Yu Wang, Susan J. Done. The calcium channel subunit CACNG4 plays a role in breast cancer metastasis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5116. doi:10.1158/1538-7445.AM2013-5116