BRCA1 dysfunction in sporadic basal-like breast cancer

Unveiling the vulnerabilities of synthetic lethality in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most invasive molecular subtype of breast cancer (BC), accounting for about nearly 15% of all BC cases reported annually. The absence of the three major BC hormone receptors, Estrogen (ER), Progesterone (PR), and Human Epidermal Growth Factor 2 (HER2) receptor, accounts for the characteristic "Triple negative" phraseology. The absence of these marked receptors makes this cancer insensitive to classical endocrine therapeutic approaches. Hence, the available treatment options remain solemnly limited to only conventional realms of chemotherapy and radiation therapy. Moreover, these therapeutic regimes are often accompanied by numerous treatment side-effects that account for early distant metastasis, relapse, and shorter overall survival in TNBC patients. The rigorous ongoing research in the field of clinical oncology has identified certain gene-based selective tumor-targeting susceptibilities, which are known to account for the molecular fallacies and mutation-based genetic alterations that develop the progression of TNBC. One such promising approach is synthetic lethality, which identifies novel drug targets of cancer, from undruggable oncogenes or tumor-suppressor genes, which cannot be otherwise clasped by the conventional approaches of mutational analysis. Herein, a holistic scientific review is presented, to undermine the mechanisms of synthetic lethal (SL) interactions in TNBC, the epigenetic crosstalks encountered, the role of Poly (ADP-ribose) polymerase inhibitors (PARPi) in inducing SL interactions, and the limitations faced by the lethal interactors. Thus, the future predicament of synthetic lethal interactions in the advancement of modern translational TNBC research is assessed with specific emphasis on patient-specific personalized medicine.

Analytical and therapeutic profiles of DNA methylation alterations in cancer; an overview of changes in chromatin arrangement and alterations in histone surfaces

DNA methylation is the most important epigenetic element that activates the inhibition of gene transcription and is included in the pathogenesis of all types of malignancies. Remarkably, the effectors of DNA methylation are DNMTs (DNA methyltransferases) that catalyze de novo or keep methylation of hemimethylated DNA after the DNA replication process. DNA methylation structures in cancer are altered, with three procedures by which DNA methylation helps cancer development which are including direct mutagenesis, hypomethylation of the cancer genome, and also focal hypermethylation of the promoters of TSGs (tumor suppressor genes). Conspicuously, DNA methylation, nucleosome remodeling, RNA-mediated targeting, and histone modification balance modulate many biological activities that are essential and indispensable to the genesis of cancer and also can impact many epigenetic changes including DNA methylation and histone modifications as well as adjusting of non-coding miRNAs expression in prevention and treatment of many cancers. Epigenetics points to heritable modifications in gene expression that do not comprise alterations in the DNA sequence. The nucleosome is the basic unit of chromatin, consisting of 147 base pairs (bp) of DNA bound around a histone octamer comprised of one H3/H4 tetramer and two H2A/H2B dimers. DNA methylation is preferentially distributed over nucleosome regions and is less increased over flanking nucleosome-depleted DNA, implying a connection between nucleosome positioning and DNA methylation. In carcinogenesis, aberrations in the epigenome may also include in the progression of drug resistance. In this report, we report the rudimentary notes behind these epigenetic signaling pathways and emphasize the proofs recommending that their misregulation can conclude in cancer. These findings in conjunction with the promising preclinical and clinical consequences observed with epigenetic drugs against chromatin regulators, confirm the important role of epigenetics in cancer therapy.

Molecular biology of microRNA-342 during tumor progression and invasion

Cancer is considered as one of the main causes of human deaths and health challenges in the world. Various factors are involved in the high death rate of cancer patients, including late diagnosis and drug resistance that result in treatment failure and tumor recurrence. Invasive diagnostic methods are one of the main reasons of late tumor detection in cancer patients. Therefore, it is necessary to investigate the molecular tumor biology to introduce efficient non-invasive markers. MicroRNAs (miRNAs) are involved in regulation of the cellular mechanisms such as cell proliferation, apoptosis, and migration. MiRNAs deregulations have been also frequently shown in different tumor types. Here, we discussed the molecular mechanisms of miR-342 during tumor growth. MiR-342 mainly functions as a tumor suppressor by the regulation of transcription factors and signaling pathways such as WNT, PI3K/AKT, NF-kB, and MAPK. Therefore, miR-342 mimics can be used as a reliable therapeutic strategy to inhibit the tumor cells growth. The present review can also pave the way to introduce the miR-342 as a non-invasive diagnostic/prognostic marker in cancer patients.

Meta-analysis of Genetic polymorphism of Enhancer of Zeste Homolog2 gene in cancer susceptibility

The alteration in the expression of enhancer of zeste homolog-2 (EZH2) gene is very well known in the progression, severity, and aggressiveness of cancer. Hence, it is important to study the genomic variation of the EZH2 gene. Previously, many association-based studies investigated the association between rs2302427C>G and cancer susceptibility. However, the result had been inconsistent. Therefore, our meta-analysis aimed to identify the association between EZH2 rs2302427 and cancer risk. A systematic literature search was done for databases PubMed, Google Scholar, Science Direct, and Cochrane library up to September 2020 and statistical analysis was performed by RevMan v 5.3. A total of six studies comprised 1876 cases and 2555 controls were included in the current meta-analysis. The pooled analysis showed that overall, there is significant association of rs2302427 C>G change with reduced cancer risk (odds ratio = 0.60, 95% confidence interval [0.35-1.03], P = 0.07) but non-significantly. Further, the subgroup analysis also revealed that there is no significant difference between the Asian and European population, and both exhibit the protective nature of rs2302427 with cancer. The present meta-analysis indicated that EZH2 rs2302427 has an association with cancer in reducing the risk but for the Indian population studies are required as the Indian population comprises various sub-population genetically isolated for long.

A transcription-independent mechanism determines rapid periodic fluctuations of BRCA1 expression

BRCA1 expression is highly regulated to prevent genomic instability and tumorigenesis. Dysregulation of BRCA1 expression correlates closely with sporadic basal-like breast cancer and ovarian cancer. The most significant characteristic of BRCA1 regulation is periodic expression fluctuation throughout the cell cycle, which is important for the orderly progression of different DNA repair pathways throughout the various cell cycle phases and for further genomic stability. However, the underlying mechanism driving this phenomenon is poorly understood. Here, we demonstrate that RBM10-mediated RNA alternative splicing coupled to nonsense-mediated mRNA decay (AS-NMD), rather than transcription, determines the periodic fluctuations in G1/S-phase BRCA1 expression. Furthermore, AS-NMD broadly regulates the expression of period genes, such as DNA replication-related genes, in an uneconomical but more rapid manner. In summary, we identified an unexpected posttranscriptional mechanism distinct from canonical processes that mediates the rapid regulation of BRCA1 as well as other period gene expression during the G1/S-phase transition and provided insights into potential targets for cancer therapy.

Harnessing Epigenetics for Breast Cancer Therapy: The Role of DNA Methylation, Histone Modifications, and MicroRNA

Breast cancer exhibits various epigenetic abnormalities that regulate gene expression and contribute to tumor characteristics. Epigenetic alterations play a significant role in cancer development and progression, and epigenetic-targeting drugs such as DNA methyltransferase inhibitors, histone-modifying enzymes, and mRNA regulators (such as miRNA mimics and antagomiRs) can reverse these alterations. Therefore, these epigenetic-targeting drugs are promising candidates for cancer treatment. However, there is currently no effective epi-drug monotherapy for breast cancer. Combining epigenetic drugs with conventional therapies has yielded positive outcomes and may be a promising strategy for breast cancer therapy. DNA methyltransferase inhibitors, such as azacitidine, and histone deacetylase inhibitors, such as vorinostat, have been used in combination with chemotherapy to treat breast cancer. miRNA regulators, such as miRNA mimics and antagomiRs, can alter the expression of specific genes involved in cancer development. miRNA mimics, such as miR-34, have been used to inhibit tumor growth, while antagomiRs, such as anti-miR-10b, have been used to inhibit metastasis. The development of epi-drugs that target specific epigenetic changes may lead to more effective monotherapy options in the future.

BRCA1 deficiency in triple-negative breast cancer: Protein stability as a basis for therapy

Mutations in breast cancer-associated 1 (BRCA1) increase the lifetime risk of developing breast cancer by up to 51% over the risk of the general population. Many aspects of this multifunctional protein have been revealed, including its essential role in homologous recombination repair, E3 ubiquitin ligase activity, transcriptional regulation, and apoptosis. Although most studies have focused on BRCA1 deficiency due to mutations, only a minority of patients carry BRCA1 mutations. A recent study has suggested an expanded definition of BRCA1 deficiency with reduced BRCA1 levels, which accounts for almost half of all triple-negative breast cancer (TNBC) patients. Reduced BRCA1 levels can result from epigenetic modifications or increased proteasomal degradation. In this review, we discuss how this knowledge of BRCA1 function and regulation of BRCA1 protein stability can help overcome the challenges encountered in the clinic and advance current treatment strategies for BRCA1-related breast cancer patients, especially focusing on TNBC.

Analyses of canine cancer mutations and treatment outcomes using real-world clinico-genomics data of 2119 dogs

Spontaneous tumors in canines share significant genetic and histological similarities with human tumors, positioning them as valuable models to guide drug development. However, current translational studies have limited real world evidence as cancer outcomes are dispersed across veterinary clinics and genomic tests are rarely performed on dogs. In this study, we aim to expand the value of canine models by systematically characterizing genetic mutations in tumors and their response to targeted treatments. In total, we collect and analyze survival outcomes for 2119 tumor-bearing dogs and the prognostic effect of genomic alterations in a subset of 1108 dogs. Our analysis identifies prognostic concordance between canines and humans in several key oncogenes, including TP53 and PIK3CA. We also find that several targeted treatments designed for humans are associated with a positive prognosis when used to treat canine tumors with specific genomic alterations, underscoring the value of canine models in advancing drug discovery for personalized oncology.

BMI-1 promotes breast cancer proliferation and metastasis through different mechanisms in different subtypes

Breast cancer is among the most common malignant cancers in women. B-cell-specific Moloney murine leukemia virus integration site 1 (BMI-1) is a transcriptional repressor that has been shown to be involved in tumorigenesis, the cell cycle, and stem cell maintenance. In our study, increased expression of BMI-1 was found in both human triple negative breast cancer and luminal A-type breast cancer tissues compared with adjacent tissues. We also found that knockdown of BMI-1 significantly suppressed cell proliferation and migration in vitro and in vivo. Further mechanistic research demonstrated that BMI-1 directly bound to the promoter region of CDKN2D/BRCA1 and inhibited its transcription in MCF-7/MDA-MB-231. More importantly, we discovered that knockdown of CDKN2D/BRCA1 could promote cell proliferation and migration after repression by PTC-209. Our results reveal that BMI-1 transcriptionally suppressed BRCA1 in TNBC cell lines whereas, in luminal A cell lines, CDKN2D was the target gene. This provides a reference for the precise treatment of different types of breast cancer in clinical practice.

The crosstalk of the human microbiome in breast and colon cancer: A metabolomics analysis

The human microbiome's role in colon and breast cancer is described in this review. Understanding how the human microbiome and metabolomics interact with breast and colon cancer is the chief area of this study. First, the role of the gut and distal microbiome in breast and colon cancer is investigated, and the direct relationship between microbial dysbiosis and breast and colon cancer is highlighted. This work also focuses on the many metabolomic techniques used to locate prospective biomarkers, make an accurate diagnosis, and research new therapeutic targets for cancer treatment. This review clarifies the influence of anti-tumor medications on the microbiota and the proactive measures that can be taken to treat cancer using a variety of therapies, including radiotherapy, chemotherapy, next-generation biotherapeutics, gene-based therapy, integrated omics technology, and machine learning.

Fucoxanthin Is a Potential Therapeutic Agent for the Treatment of Breast Cancer

Breast cancer (BC) is one of the most common cancers diagnosed and the leading cause of cancer-related death in women. Although there are first-line treatments for BC, drug resistances and adverse events have been reported. Given the incidence of BC keeps increasing, seeking novel therapeutics is urgently needed. Fucoxanthin (Fx) is a dietary carotenoid commonly found in seaweeds and diatoms. Both in vitro and in vivo studies show that Fx and its deacetylated metabolite fucoxanthinol (Fxol) inhibit and prevent BC growth. The NF-κB signaling pathway is considered the major pathway contributing to the anti-proliferation, anti-angiogenesis and pro-apoptotic effects of Fx and Fxol. Other signaling molecules such as MAPK, MMP2/9, CYP and ROS are also involved in the anti-cancer effects by regulating the tumor microenvironment, cancer metastasis, carcinogen metabolism and oxidation. Besides, Fx also possesses anti-obesity effects by regulating UCP1 levels and lipid metabolism, which may help to reduce BC risk. More importantly, mounting evidence demonstrates that Fx overcomes drug resistance. This review aims to give an updated summary of the anti-cancer effects of Fx and summarize the underlying mechanisms of action, which will provide novel strategies for the development of Fx as an anti-cancer therapeutic agent.

BRCA1: An Endocrine and Metabolic Regulator

The breast and ovarian cancer susceptibility gene (BRCA1) is a tumor suppressor whose mutation has been associated with the development of breast, ovarian and, probably, other malignancies at young ages. The BRCA1 gene product participates in multiple biological pathways including the DNA damage response, transcriptional control, cell growth and apoptosis. Inactivating germline mutations of the BRCA1 gene can be detected in a substantial portion of families with inherited breast and/or ovarian cancer. While the genomic and cancer-related actions of BRCA1 have been extensively investigated, not much information exists regarding the cellular and circulating factors involved in regulation of BRCA1 expression and action. The present review article dissects the emerging role of BRCA1 as an important regulator of various endocrine and metabolic axes. Experimental and clinical evidence links BRCA1 with a number of peptide and steroid hormones. Furthermore, comprehensive analyses identified complex interactions between the insulin/insulin-like growth factor-1 (IGF1) signaling axis and BRCA1. The correlation between metabolic disorders, including diabetes and the metabolic syndrome, and BRCA1 mutations, are discussed in this article.

Research advances and new challenges in overcoming triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a pathological term used to identify invasive breast cancers that lack expression of estrogen and progesterone receptors and do not have pathologic overexpression of the HER2 receptor or harbor ERBB2 gene amplification. TNBC includes a collection of multiple distinct disease entities based upon genomic, transcriptomic and phenotypic characterization. Despite improved clinical outcomes with the development of novel therapeutics, TNBC still yields the worst prognosis among all clinical subtypes of breast cancer. We will systematically review evidence of the genomic evolution of TNBC, as well as potential mechanisms of disease progression and treatment resistance, defined in part by advances in next-generation DNA sequencing technology (including single cell sequencing), providing a new perspective on treatment strategies, and promise to reveal new potential therapeutic targets. Moreover, we review novel therapies aimed at homologous recombination deficiency, PI3 kinase/AKT/PTEN pathway activation, androgen receptor blockade, immune checkpoint inhibition, as well as antibody-drug conjugates engaging novel cell surface targets, including recent progress in pre-clinical and clinical studies which further validate the role of targeted therapies in TNBC. Despite major advances in treatment for TNBC, including FDA approval of 2 PARP inhibitors for metastatic TNBC, the crossing of the superiority boundary in a phase 3, placebo-controlled study of adjuvant olaparib in early-stage patients with germline BRCA-mutated high-risk HER2-negative early breast cancer, the FDA approval of 2 PD-(L)1 checkpoint antibodies for metastatic TNBC, and the FDA approval of the first antibody drug conjugate for TNBC, significant challenges remain. For example, despite the dawn of immunotherapy in metastatic TNBC, durable responses are limited to a small subset of patients, definitive biomarkers for patient selection are lacking, and the Oncology Drug Advisory Committee to the FDA has recently voted against approval of an anti-PD-1 checkpoint antibody high risk early-stage TNBC in the neoadjuvant setting. Also, despite early positive randomized phase 2 studies of AKT inhibition in metastatic TNBC, a recent phase 3 registration trial failed to validate earlier phase 2 data. Finally, we note that level one evidence for clinical efficacy of androgen receptor blockade in TNBC is still lacking. To meet these and other challenges, we will catalogue the ongoing exponential increase in interest in basic, translational, and clinical research to develop new treatment paradigms for TNBC.

Surrogate endpoints for early-stage breast cancer: a review of the state of the art, controversies, and future prospects

Drug approval for early-stage breast cancer (EBC) has been historically granted in the context of registration trials based on adequate outcomes such as disease-free survival and overall survival. Improvements in long-term outcomes have made it more difficult to demonstrate the clinical benefit of a new cancer drug in large, randomized, comparative clinical trials. Therefore, the use of surrogate endpoints rather than traditional measures allows for cancer drug trials to proceed with smaller sample sizes and shorter follow-up periods, which reduces drug development time. Among surrogate endpoints for breast cancer, the increase in pathological complete response (pCR) rates was considered appropriate for accelerated drug approval. The association between pCR and long-term outcomes was strongest in patients with aggressive tumor subtypes, such as triple-negative and human epidermal growth factor receptor 2 (HER2)-positive/hormone receptor-negative breast cancers. Whereas in hormone receptor-positive/HER2-negative EBC, the most accepted surrogate markers for endocrine therapy-based trials include changes in Ki67 and the preoperative endocrine prognostic index. Beyond the classic endpoints, further prognostic tools are required to provide EBC patients with individualized and effective therapies, and the neoadjuvant setting provides an excellent platform for drug development and biomarker discovery. Nowadays, the availability of multigene signatures is offering a standardized quantitative and reproducible tool to potentiate the efficacy of standard treatment for high-risk patients and develop de-escalated treatments for patients at lower risk of relapse. In this article, we first evaluate the surrogacies used for long-term outcomes and the underlying evidence supporting the use of each surrogate endpoint for the accelerated or regular drug approval process in EBC. Next, we provide an overview of the most recent studies and innovative strategies in a (neo)adjuvant setting as a platform to accelerate new drug approval. Finally, we highlight some clinical trials aimed at tailoring systemic treatment of EBC using prognosis-related factors or early biomarkers of drug sensitivity or resistance.

Triple-negative breast cancer and basal-like subtype : Pathology and targeted therapy

Triple-negative breast cancer (TNBC) is a heterogenous disease. For personalized medicine, it is essential to identify and classify tumor subtypes to develop effective therapeutic strategies. Although gene expression profiling has identified several TNBC subtypes, classification of these tumors remains complex. Most TNBCs exhibit an aggressive phenotype, but some rare types have a favorable clinical course. In this review, we summarize the classification and characteristics related to the various TNBC subtypes, including the rare types. Therapeutic methods that are suitable for each subtype are also discussed. Of the intrinsic breast cancer subtypes identified by gene expression analysis, the basal-like subtype specifically displayed decreased expression of an estrogen receptor (ER) and human epidermal growth factor receptor 2 (HER2) cluster. We also present results that characterize the TNBC and basal-like phenotypes. TNBC may be categorized into four major classes : basal-like, immune-enriched, mesenchymal, and luminal androgen receptor. Therapeutic strategies for each subtype have been proposed along with newly approved targeted therapies for TNBC, such as immune checkpoint inhibitors. Understanding the classification of TNBC based on gene expression profiling in association with clinicopathological factors will facilitate accurate pathological diagnosis and effective treatment selection. J. Med. Invest. 68 : 213-219, August, 2021.

Molecular Targets and Promising Therapeutics of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is one of the most heterogeneous diseases in solid tumors and has limited therapeutic options. Due to the lack of appropriate targetable markers, the mainstay therapeutic strategy for patients with TNBC has been chemotherapy for the last several decades. Indeed, TNBC tumors have no expression of estrogen receptor, progesterone receptor, or human epidermal growth factor receptor 2 (HER2); therefore, they do not respond to hormone therapy and HER2-targeted therapy. In this review paper, the molecular heterogeneities, possible therapeutic targets, and recently approved and upcoming drugs for TNBC will be summarized.

Clustering subtypes of breast cancer by combining immunohistochemistry profiles and metabolism characteristics measured using FDG PET/CT

Background

The aim of this study was to investigate the effect of combining immunohistochemical profiles and metabolic information to characterize breast cancer subtypes.

Methods

This retrospective study included 289 breast tumors from 284 patients who underwent preoperative ¹⁸ F-fluorodeoxyglucose (FDG) positron emission tomography/ computed tomography (PET/CT). Molecular subtypes of breast cancer were classified as Hormonal, HER2, Dual (a combination of both Hormonal and HER2 features), and triple-negative (TN). Histopathologic findings and immunohistochemical results for Ki-67, EGFR, CK 5/6, and p53 were also analyzed. The maximum standardized uptake value (SUV) measured from FDG PET/CT was used to evaluate tumoral glucose metabolism.

Results

Overall, 182, 24, 47, and 36 tumors were classified as Hormonal, HER2, Dual, and TN subtypes, respectively. Molecular profiles of tumor aggressiveness and the tumor SUV revealed a gradual increase from the Hormonal to the TN type. The tumor SUV was significantly correlated with tumor size, expression levels of p53, Ki-67, and EGFR, and nuclear grade (all p < 0.001). In contrast, the tumor SUV was negatively correlated with the expression of estrogen receptors (r = − 0.234, p < 0.001) and progesterone receptors (r = − 0.220, p < 0.001). Multiple linear regression analysis revealed that histopathologic markers explained tumor glucose metabolism (adjusted R-squared value 0.238, p < 0.001). Tumor metabolism can thus help define breast cancer subtypes with aggressive/adverse prognostic features.

Conclusions

Metabolic activity measured using FDG PET/CT was significantly correlated with the molecular alteration profiles of breast cancer assessed using immunohistochemical analysis. Combining molecular markers and metabolic information may aid in the recognition and understanding of tumor aggressiveness in breast cancer and be helpful as a prognostic marker.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40644-021-00424-4.

Synergistic targeting of BRCA1 mutated breast cancers with PARP and CDK2 inhibition

Basal-like breast cancers (BLBC) are aggressive breast cancers that respond poorly to targeted therapies and chemotherapies. In order to define therapeutically targetable subsets of BLBC we examined two markers: cyclin E1 and BRCA1 loss. In high grade serous ovarian cancer (HGSOC) these markers are mutually exclusive, and define therapeutic subsets. We tested the same hypothesis for BLBC. Using a BLBC cohort enriched for BRCA1 loss, we identified convergence between BRCA1 loss and high cyclin E1 protein expression, in contrast to HGSOC in which CCNE1 amplification drives increased cyclin E1. In cell lines, BRCA1 loss was associated with stabilized cyclin E1 during the cell cycle, and BRCA1 siRNA led to increased cyclin E1 in association with reduced phospho-cyclin E1 T62. Mutation of cyclin E1 T62 to alanine increased cyclin E1 stability. We showed that tumors with high cyclin E1/BRCA1 mutation in the BLBC cohort also had decreased phospho-T62, supporting this hypothesis. Since cyclin E1/CDK2 protects cells from DNA damage and cyclin E1 is elevated in BRCA1 mutant cancers, we hypothesized that CDK2 inhibition would sensitize these cancers to PARP inhibition. CDK2 inhibition induced DNA damage and synergized with PARP inhibitors to reduce cell viability in cell lines with homologous recombination deficiency, including BRCA1 mutated cell lines. Treatment of BRCA1 mutant BLBC patient-derived xenograft models with combination PARP and CDK2 inhibition led to tumor regression and increased survival. We conclude that BRCA1 status and high cyclin E1 have potential as predictive biomarkers to dictate the therapeutic use of combination CDK inhibitors/PARP inhibitors in BLBC.

The Effects of Exercise Duration and Intensity on Breast Cancer-Related DNA Methylation: A Randomized Controlled Trial

Emerging research suggests that one mechanism through which physical activity may decrease cancer risk is through its influence on the methylation of genes associated with cancer. The purpose of the current study was to prospectively test, using a rigorous experimental design, whether aerobic exercise affects DNA methylation in genes associated with breast cancer, as well as whether quantity of exercise completed affects change in DNA methylation in a dose-response manner. 276 women (M age = 37.25, SD = 4.64) were recruited from the Denver metro area for a randomized controlled trial in which participants were assigned to a supervised aerobic exercise program varying in a fully crossed design by intensity (55-65% versus 75-85% of VO2max) and duration (40 versus 20 min per session). DNA methylation was assessed via blood samples provided at baseline, after completing a 16-week supervised exercise intervention, and six months after the intervention. 137 participants completed the intervention, and 81 had viable pre-post methylation data. Contrary to our hypotheses, total exercise volume completed in kcal/kg/week was not associated with methylation from baseline to post-intervention for any of the genes of interest. An increase in VO2max over the course of the intervention, however, was associated with decreased post-intervention methylation of BRCA1, p = 0.01. Higher levels of self-reported exercise during the follow-up period were associated with lower levels of GALNT9 methylation at the six-month follow-up. This study provides hypothesis-generating evidence that increased exercise behavior and or increased fitness might affect methylation of some genes associated with breast cancer to reduce risk.

Wnt/β-Catenin Inhibition Disrupts Carboplatin Resistance in Isogenic Models of Triple-Negative Breast Cancer

Triple-Negative Breast Cancer (TNBC) is the most aggressive breast cancer subtype, characterized by limited treatment options and higher relapse rates than hormone-receptor-positive breast cancers. Chemotherapy remains the mainstay treatment for TNBC, and platinum salts have been explored as a therapeutic alternative in neo-adjuvant and metastatic settings. However, primary and acquired resistance to chemotherapy in general and platinum-based regimens specifically strongly hampers TNBC management. In this study, we used carboplatin-resistant in vivo patient-derived xenograft and isogenic TNBC cell-line models and detected enhanced Wnt/β-catenin activity correlating with an induced expression of stem cell markers in both resistant models. In accordance, the activation of canonical Wnt signaling in parental TNBC cell lines increases stem cell markers' expression, formation of tumorspheres and promotes carboplatin resistance. Finally, we prove that Wnt signaling inhibition resensitizes resistant models to carboplatin both in vitro and in vivo, suggesting the synergistic use of Wnt inhibitors and carboplatin as a therapeutic option in TNBC. Here we provide evidence for a prominent role of Wnt signaling in mediating resistance to carboplatin, and we establish that combinatorial targeting of Wnt signaling overcomes carboplatin resistance enhancing chemotherapeutic drug efficacy.

Cavin3 released from caveolae interacts with BRCA1 to regulate the cellular stress response

Caveolae-associated protein 3 (cavin3) is inactivated in most cancers. We characterized how cavin3 affects the cellular proteome using genome-edited cells together with label-free quantitative proteomics. These studies revealed a prominent role for cavin3 in DNA repair, with BRCA1 and BRCA1 A-complex components being downregulated on cavin3 deletion. Cellular and cell-free expression assays revealed a direct interaction between BRCA1 and cavin3 that occurs when cavin3 is released from caveolae that are disassembled in response to UV and mechanical stress. Overexpression and RNAi-depletion revealed that cavin3 sensitized various cancer cells to UV-induced apoptosis. Supporting a role in DNA repair, cavin3-deficient cells were sensitive to PARP inhibition, where concomitant depletion of 53BP1 restored BRCA1-dependent sensitivity to PARP inhibition. We conclude that cavin3 functions together with BRCA1 in multiple cancer-related pathways. The loss of cavin3 function may provide tumor cell survival by attenuating apoptotic sensitivity and hindering DNA repair under chronic stress conditions.

ID4 predicts poor prognosis and promotes BDNF-mediated oncogenesis of colorectal cancer

Inhibitors of DNA binding and cell differentiation (ID) proteins regulate cellular differentiation and tumor progression. Whether ID family proteins serve as a linkage between pathological differentiation and cancer stemness in colorectal cancer is largely unknown. Here, the expression of ID4, but not other ID family proteins, was enriched in LGR5-high colon cancer stem cells. Its high expression was associated with poor pathological differentiation of colorectal tumors and shorter survival in patients. Knockdown of ID4 inhibited the growth and dissemination of colon cancer cells, while enhancing chemosensitivity. Through gene expression profiling analysis, brain-derived neurotrophic factor (BDNF) was identified as a downstream target of ID4 expression in colorectal cancer. BDNF knockdown decreased the growth and migration of colon cancer cells, and its expression enhanced dissemination, anoikis resistance and chemoresistance. ID4 silencing attenuated the epithelial-to-mesenchymal transition pattern in colon cancer cells. Gene cluster analysis revealed that ID4 and BDNF expression was clustered with mesenchymal markers and distant from epithelial genes. BDNF silencing decreased the expression of mesenchymal markers Vimentin, CDH2 and SNAI1. These findings demonstrated that ID4-BDNF signaling regulates colorectal cancer survival, with the potential to serve as a prognostic marker in colorectal cancer.

ID1 and ID4 Are Biomarkers of Tumor Aggressiveness and Poor Outcome in Immunophenotypes of Breast Cancer

Simple Summary

Inhibitor of differentiation (ID) proteins are essential to promote proliferation during embryonic development, but they are silenced in most adult tissues. Evidence to date shows ID1 expression in many tumor types, including breast cancer. However, the role of the remaining ID family members, especially ID4, in breast cancer remains unclear. In this work, we aimed to assess the four ID genes expression in breast cancer cell lines and a long series of breast cancer samples and correlate them with clinicopathological features and patients’ survival. We observed a significantly higher expression of ID4 in tumor cell lines than the healthy breast epithelium cell line. We confirmed that the overexpression of ID1 and ID4 correlated with more aggressive phenotypes and poor survival in breast cancer patients’ samples. Our results support the importance of ID proteins as targets for the development of anti-cancer drugs.

Abstract

Inhibitor of differentiation (ID) proteins are a family of transcription factors that contribute to maintaining proliferation during embryogenesis as they avoid cell differentiation. Afterward, their expression is mainly silenced, but their reactivation and contribution to tumor development have been suggested. In breast cancer (BC), the overexpression of ID1 has been previously described. However, whether the remaining ID genes have a specific role in this neoplasia is still unclear. We studied the mRNA expression of all ID genes by q RT-PCR in BC cell lines and 307 breast carcinomas, including all BC subtypes. Our results showed that ID genes are highly expressed in all cell lines tested. However, ID4 presented higher expression in BC cell lines compared to a healthy breast epithelium cell line. In accordance, ID1 and ID4 were predominantly overexpressed in Triple-Negative and HER2-enriched samples. Moreover, high levels of both genes were associated with larger tumor size, histological grade 3, necrosis and vascular invasion, and poorer patients’ outcomes. In conclusion, ID1 and ID4 may act as biomarkers of tumor aggressiveness and worse prognosis in breast cancer, and they could be used as potential targets for new treatments discover.

Problematic breast tumors reassessed in light of novel molecular data

Breast cancer is a vastly heterogeneous disease encompassing a panoply of special histological subtypes. Although rare breast tumors have largely not been investigated systematically in large scale genomics series, recent studies have shed light on the genetic underpinnings of special histologic subtypes of breast cancer. Genomic analyses of estrogen receptor-positive special histologic types of breast cancer have not resulted in the identification of novel pathognomonic genetic alterations in addition to the confirmation of the presence of CDH1 loss-of-function mutations in invasive lobular carcinomas. By contrast, the analyses of triple-negative breast cancers have demonstrated that low-grade triple-negative breast cancers categorically differ from the common forms of high-grade triple-negative disease biologically and phenotypically and are underpinned by specific fusion genes or hotspot mutations. A subset of low-grade triple-negative disease has been shown to harbor highly recurrent if not pathognomonic genetic alterations, such as ETV6-NTRK3 fusion gene in secretory carcinomas, the MYB-NFIB fusion gene, MYBL1 rearrangements or MYB gene amplification in adenoid cystic carcinomas, and HRAS Q61 hotspot mutations coupled with mutations in PI3K pathway genes in estrogen receptor-negative adenomyoepitheliomas. A subset of these pathognomonic genetic alterations (e.g., NTRK1/2/3 fusion genes) now constitute an FDA approved indication for the use of TRK inhibitors in the advanced/metastatic setting. These studies have also corroborated that salivary gland-like tumors of the breast, other than acinic cell carcinomas, harbor the repertoire of somatic genetic alterations detected in their salivary gland counterparts. Reassuringly, the systematic study of special histologic types of breast cancer utilizing state-of-the-art sequencing approaches, rather than rendering pathology obsolete, has actually strengthened the importance of breast cancer histologic typing and is providing additional ancillary markers for the diagnosis of these rare but fascinating entities.

Impact of molecular subtype on 1325 early-stage breast cancer patients homogeneously treated with hypofractionated radiotherapy without boost: Should the indications for radiotherapy be more personalized?

Aim

We report molecular subtype impact on 1325 early breast cancer (BCa) patients treated with whole breast hypofractionated (WBH) adjuvant forward-planned intensity modulated radiotherapy (F-IMRT) without boost.

Methods and materials

From 02/2009-05/2017 1325 patients with pTis-pT3, pNx-N1aM0 BCa who underwent breast conservation surgery were treated with WBHF-IMRT in our institute, to a total dose of 40 Gy/15 fractions, without boost. Median age: 62 (interquartile range-IQR-:51.14–70.53) years. Histology: 8% in situ carcinoma (ISC), 92% invasive tumors. Molecular subtypes (invasive tumors): 49.9% Luminal A, 33.1% Luminal B Her2 negative (−), 6.2% Luminal B Her2 positive (+), 3.6% Hormone Receptor (HR)- Her2+, 7.1% Triple negative (TNBC), and 0.2% HR+. Chemotherapy (CT) was prescribed in 28% of patients, hormonal therapy in 80.3%, monoclonal antibodies (MAb) in 86.8% of Luminal B Her2+ and 97.7% of HR- Her2+ patients.

Results

Median follow up was 72.43 (IQR: 44.63–104.13) months. The 5-year Kaplan-Meier estimates of local relapse-free survival (LRFS) was 97.8%, regional-(RRFS) 98.6%, loco-regional- (LRRFS) 96.9%, distant- (DRFS) 96.6%, disease-free survival (DFS) 94.8% and overall survival (OS) 95.5%. Considering molecular subtypes, 5-year LRFS was: 99.8% for Luminal A, 96.7% for Luminal B Her2-, 94.1% for Luminal B Her2+, 87.9% for HR- Her2+, 95.1% for TNBC and 99.1% for in situ carcinoma.

Conclusion

While the overall estimated probability of LR within 5 years after WBHF-IMRT without boost is good (2.2%), molecular subtypes have a strong impact, despite MAb therapy in Her2+ patients, and CT for TNBC patients, and could be used as a parameter in deciding the boost prescription.

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Hypofractionated three-weeks radiotherapy ensures good local control whitout boost.

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In 1325 early stage breast cancers 5-year local relapse without boost was 2.2%.

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Molecular subtypes have a strong impact on estimated probability of local relapse.

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5-year local control (LC) was 99.8% for Luminal A vs 87.9% for HR- Her2+.

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5-year LC was 96.7% for Luminal B Her2-, 94.1% for Luminal B Her2+, 95.1% for TNBC.

Glucose Concentration in Cell Culture Medium Influences the BRCA1-Mediated Regulation of the Lipogenic Action of IGF-I in Breast Cancer Cells

Hyperglycaemia is a common metabolic alteration associated with breast cancer risk and progression. We have previously reported that BRCA1 restrains metabolic activity and proliferative response to IGF-I anabolic actions in breast cancer cells cultured in high glucose. Here, we evaluated the impact of normal physiological glucose on these tumour suppressive roles of BRCA1. Human breast cancer cells cultured in normal physiological and high glucose were treated with IGF-I (0-500 ng/mL). Cellular responses were evaluated using immunoblotting, co-immunoprecipitation, and cell viability assay. As we previously reported, IGF-I induced ACCA dephosphorylation by reducing the association between BRCA1 and phosphorylated ACCA in high glucose, and upregulated FASN abundance downstream of ACCA. However, these effects were not observed in normal glucose. Normal physiological glucose conditions completely blocked IGF-I-induced ACCA dephosphorylation and FASN upregulation. Co-immunoprecipitation studies showed that normal physiological glucose blocked ACCA dephosphorylation by increasing the association between BRCA1 and phosphorylated ACCA. Compared to high glucose, the proliferative response of breast cancer cells to IGF-I was reduced in normal glucose, whereas no difference was observed in normal mammary epithelial cells. Considering these results collectively, we conclude that normal physiological glucose promotes the novel function of BRCA1 as a metabolic restraint of IGF-I actions. These data suggest that maintaining normal glucose levels may improve BRCA1 function in breast cancer and slow down cancer progression.

Practical classification of triple-negative breast cancer: intratumoral heterogeneity, mechanisms of drug resistance, and novel therapies

Triple-negative breast cancer (TNBC) is not a unique disease, encompassing multiple entities with marked histopathological, transcriptomic and genomic heterogeneity. Despite several efforts, transcriptomic and genomic classifications have remained merely theoretic and most of the patients are being treated with chemotherapy. Driver alterations in potentially targetable genes, including PIK3CA and AKT, have been identified across TNBC subtypes, prompting the implementation of biomarker-driven therapeutic approaches. However, biomarker-based treatments as well as immune checkpoint inhibitor-based immunotherapy have provided contrasting and limited results so far. Accordingly, a better characterization of the genomic and immune contexture underpinning TNBC, as well as the translation of the lessons learnt in the metastatic disease to the early setting would improve patients' outcomes. The application of multi-omics technologies, biocomputational algorithms, assays for minimal residual disease monitoring and novel clinical trial designs are strongly warranted to pave the way toward personalized anticancer treatment for patients with TNBC.

miR-9-Mediated Inhibition of EFEMP1 Contributes to the Acquisition of Pro-Tumoral Properties in Normal Fibroblasts

Tumor growth and invasion occurs through a dynamic interaction between cancer and stromal cells, which support an aggressive niche. MicroRNAs are thought to act as tumor messengers to “corrupt” stromal cells. We previously demonstrated that miR-9, a known metastamiR, is released by triple negative breast cancer (TNBC) cells to enhance the transition of normal fibroblasts (NFs) into cancer-associated fibroblast (CAF)-like cells. EGF containing fibulin extracellular matrix protein 1 (EFEMP1), which encodes for the ECM glycoprotein fibulin-3, emerged as a miR-9 putative target upon miRNA’s exogenous upmodulation in NFs. Here we explored the impact of EFEMP1 downmodulation on fibroblast’s acquisition of CAF-like features, and how this phenotype influences neoplastic cells to gain chemoresistance. Indeed, upon miR-9 overexpression in NFs, EFEMP1 resulted downmodulated, both at RNA and protein levels. The luciferase reporter assay showed that miR-9 directly targets EFEMP1 and its silencing recapitulates miR-9-induced pro-tumoral phenotype in fibroblasts. In particular, EFEMP1 siRNA-transfected (si-EFEMP1) fibroblasts have an increased ability to migrate and invade. Moreover, TNBC cells conditioned with the supernatant of NFs transfected with miR-9 or si-EFEMP1 became more resistant to cisplatin. Overall, our results demonstrate that miR-9/EFEMP1 axis is crucial for the conversion of NFs to CAF-like cells under TNBC signaling.

IQGAP1 control of centrosome function defines distinct variants of triple negative breast cancer

Triple negative breast cancer (TNBC) is a heterogenous and lethal disease that lacks diagnostic markers and therapeutic targets; as such common targets are highly sought after. IQGAP1 is a signaling scaffold implicated in TNBC, but its mechanism is unknown. Here we show that IQGAP1 localizes to the centrosome, interacts with and influences the expression level and localization of key centrosome proteins like BRCA1 and thereby impacts centrosome number. Genetic mutant analyses suggest that phosphorylation cycling of IQGAP1 is important to its subcellular localization and centrosome-nuclear shuttling of BRCA1; dysfunction of this process defines two alternate mechanisms associated with cell proliferation. TNBC cell lines and patient tumor tissues differentially phenocopy these mechanisms supporting clinical existence of molecularly distinct variants of TNBC defined by IQGAP1 pathways. These variants are defined, at least in part, by differential mis-localization or stabilization of IQGAP1-BRCA1 and rewiring of a novel Erk1/2-MNK1-JNK-Akt-β-catenin signaling signature. We discuss a model in which IQGAP1 modulates centrosome-nuclear crosstalk to regulate cell division and imparts on cancer. These findings have implications on cancer racial disparities and can provide molecular tools for classification of TNBC, presenting IQGAP1 as a common target amenable to personalized medicine.

Proteogenomic analysis of Inhibitor of Differentiation 4 (ID4) in basal-like breast cancer

BACKGROUND

Basal-like breast cancer (BLBC) is a poorly characterised, heterogeneous disease. Patients are diagnosed with aggressive, high-grade tumours and often relapse with chemotherapy resistance. Detailed understanding of the molecular underpinnings of this disease is essential to the development of personalised therapeutic strategies. Inhibitor of differentiation 4 (ID4) is a helix-loop-helix transcriptional regulator required for mammary gland development. ID4 is overexpressed in a subset of BLBC patients, associating with a stem-like poor prognosis phenotype, and is necessary for the growth of cell line models of BLBC through unknown mechanisms.

METHODS

Here, we have defined unique molecular insights into the function of ID4 in BLBC and the related disease high-grade serous ovarian cancer (HGSOC), by combining RIME proteomic analysis, ChIP-seq mapping of genomic binding sites and RNA-seq.

RESULTS

These studies reveal novel interactions with DNA damage response proteins, in particular, mediator of DNA damage checkpoint protein 1 (MDC1). Through MDC1, ID4 interacts with other DNA repair proteins (γH2AX and BRCA1) at fragile chromatin sites. ID4 does not affect transcription at these sites, instead binding to chromatin following DNA damage. Analysis of clinical samples demonstrates that ID4 is amplified and overexpressed at a higher frequency in BRCA1-mutant BLBC compared with sporadic BLBC, providing genetic evidence for an interaction between ID4 and DNA damage repair deficiency.

CONCLUSIONS

These data link the interactions of ID4 with MDC1 to DNA damage repair in the aetiology of BLBC and HGSOC.

Metaplastic Breast Carcinoma: Update on Histopathology and Molecular Alterations

CONTEXT—

Metaplastic carcinoma is a rare, triple-negative carcinoma of the breast that exhibits transformation of part or all of its glandular carcinomatous component into a nonglandular, or metaplastic, component. The World Health Organization currently recognizes 5 variants of metaplastic carcinoma based on their histologic appearance.

OBJECTIVE—

To review the histologic classifications, differential diagnosis, prognosis, and recent laboratory studies of metaplastic breast carcinoma.

DATA SOURCES.—

We reviewed recently published studies that collectively examine metaplastic carcinomas, including results from our own research.

CONCLUSIONS.—

Metaplastic breast carcinoma has a broad spectrum of histologic patterns, often leading to a broad differential diagnosis. Diagnosis can typically be rendered by a combination of morphology and immunohistochemical staining for high-molecular-weight cytokeratins and p63. Recent studies elucidate new genes and pathways involved in the pathogenesis of metaplastic carcinoma, including the downregulation of CCN6 and WNT pathway gene mutations, and provide a novel MMTV-Cre;Ccn6^fl/fl knockout disease-relevant mouse model to test new therapies.

A genetic variant in microRNA-146a is associated with sporadic breast cancer in a Southern Brazilian Population

MicroRNAs (miRNAs) play an essential role in gene expression and affect the development of tumours, including breast cancer (BC). Polymorphisms in miRNA genes can affect the interaction of miRNAs with their target messenger RNA by interfering, creating or disrupting target sites. The single nucleotide polymorphism (SNP) rs2910164, located in the seed region of miR146a, was shown to be associated with BC among different populations. In the present study, we investigated whether rs2910164 is associated with BC in 326 patients and 411 controls from a Brazilian population of predominantly European ancestry. The presence of the allele rs2910164*C was associated with an increased risk of BC (OR=1.4, 95% CI=1.03-1.85, p = 0.03). We also analysed publicly available RNA-seq data to evaluate if miR146a is differentially expressed in different subtypes of BC. Genotyping was performed by polymerase chain reaction with sequence-specific primers (PCR-SSP). By leveraging public data from TCGA database, we analysed 461 patients and found that miR146a is significantly more expressed in BC than in non-tumor tissue (1.47 fold, p = 0.02) and is expressed to a greater degree in aggressive BC subtypes.

BRCA1 Promoter Methylation Status in 1031 Primary Breast Cancers Predicts Favorable Outcomes Following Chemotherapy

Background

Breast Cancer 1 gene (BRCA1) is known to be inactivated in breast tumors by promoter methylation. Tumor cells in patients carrying a germline mutation in BRCA1 are sensitive to cytotoxic drugs that cause DNA double strand breaks. However, very little is known on whether patients with BRCA1 promoter methylated tumors are similarly sensitive to cytotoxic drugs. In this study, we address this by making use of extensive follow-up data on patients treated with cyclophosphamide, methotrexate, and fluorouracil in Iceland between 1976 and 2007.

Methods

We analyzed BRCA1 promoter methylation by pyrosequencing DNA from tumor samples from 1031 patients with primary breast cancer. Of those, 965 were sporadic cases, 61 were BRCA2, and five were BRCA1 germline mutation carriers. All cases were examined with respect to clinicopathological parameters and breast cancer–specific survival in patients treated with cytotoxic drugs. Information on chemotherapy treatment in noncarriers was available for 26 BRCA1 methylated tumors and 857 unmethylated tumors.

Results

BRCA1 was promoter methylated in 29 sporadic tumors or in 3.0% of cases (29 of 965), whereas none of the tumors derived from BRCA germline mutation carriers were promoter methylated. Important to note, patients with BRCA1 promoter methylation receiving chemotherapeutic drug treatment show highly improved breast cancer–specific survival compared with unmethylated controls (hazard ratio = 0.10, 95% confidence interval = 0.01 to 0.75, two-sided P = .02).

Conclusions

BRCA1 promoter methylation is predictive of improved disease outcome in patients receiving cyclophosphamide, methotrexate, and fluorouracil drug treatment. Our results support the use of markers indicative of “BRCAness” in sporadic breast cancers to identify patients that are likely to benefit from the use of DNA-damaging agents.

Differentially expressed microRNAs in exosomes of patients with breast cancer revealed by next‑generation sequencing

MicroRNAs (miRNAs/miRs) in exosomes play crucial roles in the onset, progression and metastasis of cancer by regulating the stability of target mRNAs or by inhibiting translation. In the present study, differentially expressed miRNAs were identified in exosomes of 27 breast cancer patients and 3 healthy controls using RNA sequencing. The differentially expressed microRNAs were selected by bioinformatic analysis. Subjects were followed up for 2 years and exosomal miRNA profiles were compared between patients with and without recurrence of breast cancer. A total of 30 complementary DNA libraries were constructed and sequenced and 1,835 miRNAs were detected. There were no significant differences in the expression of miRNAs between the basal-like, human epidermal growth factor receptor-2⁺, luminal A, luminal B and healthy control (HC) groups. A total of 54 differentially expressed miRNAs were identified in triple-negative breast cancer (TNBC) patients vs. HCs, including 20 upregulated and 34 downregulated miRNAs. The results of the reverse transcription-quantitative PCR were consistent with this. Receiver operating characteristic curve analyses indicated that miR-150-5p [area under the curve (AUC)=0.705, upregulated], miR-576-3p (AUC=0.691, upregulated), miR-4665-5p (AUC=0.681, upregulated) were able to distinguish breast cancer patients with recurrence from those without recurrence. In conclusion, the present results indicated differences in miRNA expression profiles between patients with TNBC and healthy controls. Certain exosomal miRNAs were indicated to have promising predictive value as biomarkers for distinguishing breast cancer with recurrence from non-recurrence, which may be utilized for preventive strategies.

DNA Repair Proteins as Therapeutic Targets in Ovarian Cancer

Epithelial ovarian cancer is a serious public health problem worldwide with the highest mortality rate of all gynecologic cancers. The current standard-of-care for the treatment of ovarian cancer is based on chemotherapy based on adjuvant cisplatin/carboplatin and taxane regimens that represent the first-line agents for patients with advanced disease. The DNA repair activity of cancer cells determines the efficacy of anticancer drugs. These features make DNA repair mechanisms a promising target for novel cancer treatments. In this context a better understanding of the DNA damage response caused by antitumor agents has provided the basis for the use of DNA repair inhibitors to improve the therapeutic use of DNA-damaging drugs. In this review, we will discuss the functions of DNA repair proteins and the advances in targeting DNA repair pathways with special emphasis in the inhibition of HRR and BER in ovarian cancer. We focused in the actual efforts in the development and clinical use of poly (ADPribose) polymerase (PARP) inhibitors for the intervention of BRCA1/BRCA2-deficient ovarian tumors. The clinical development of PARP inhibitors in ovarian cancer patients with germline BRCA1/2 mutations and sporadic high-grade serous ovarian cancer is ongoing. Some phase II and phase III trials have been completed with promising results for ovarian cancer patients.

Therapeutic landscape of metaplastic breast cancer

Metaplastic breast carcinomas (MPBC) are rare, aggressive and relatively chemorefractory tumors with a high unmet need. While most are "triple negative" and lack expression of estrogen, progesterone and HER2 receptors, MPBC are associated with worse outcomes compared to conventional triple negative invasive tumors. MPBCs are genetically heterogeneous and harbor somatic mutations, most frequently in TP53, PIK3CA and PTEN, with emerging studies suggesting a role for novel targeted therapies. These tumors have also been associated with overexpression of PD-L1 and tumor-infiltrating lymphocytes suggesting an endogenous immune response and therefore a rationale for treatment with immunotherapies. Here, we focus on therapeutic options for this difficult to treat breast cancer subtype and encourage physicians to consider targeted therapies/immunotherapies as part of ongoing clinical trials.

Gene Alterations in Triple-Negative Breast Cancer Patients in a Phase I/II Study of Eribulin and Olaparib Combination Therapy

BACKGROUND

We conducted a phase I/II clinical trial to evaluate the efficacy of eribulin and olaparib in a tablet form (EO study) for triple-negative breast cancer (TNBC) patients. We hypothesized that somatic BRCA mutations and homologous recombination repair (HRR)-related gene alterations might affect efficacy.

METHODS

Our analyses identified mutations in HRR-related genes and BRCA1/2, and we subsequently evaluated their association to response by the EO study participants. Tissue specimens were obtained from primary or metastatic lesion. Tissue specimens were examined for gene mutations or protein expression using a Foundation Medicine gene panel and immunohistochemistry.

RESULTS

In the 32 tissue specimens collected, we detected 33 gene mutations, with the most frequent nonsynonymous mutations found in TP53. The objective response rates (ORRs) in patients with and without HRR-related gene mutation were 33.3% and 40%, respectively (P = .732), and the ORRs in patients with and without somatic BRCA mutations were 60% and 33.3%, respectively (P = .264), with the ORR numerically higher in the somatic BRCA-mutation group but not statistically significant. There was no correlation between immunohistochemistry status and response or between BRCA status or HRR-related gene mutation and survival. Immunohistochemical analysis indicated that EGFR-negative patients had a tendency for better progression-free survival (log-rank P = .059) and significantly better overall survival (log-rank P = .046); however, there was no correlation between the status of other immunohistochemistry markers and survival.

CONCLUSION

These findings suggested somatic BRCA mutation and EGFR-negativity as a potential biomarker for predicting the efficacy of eribulin/olaparib combination therapy. (UMIN000018721).

PARP Inhibitors in the Treatment of Triple-Negative Breast Cancer

Breast cancer is a heterogeneous disease, manifesting in a broad differentiation in phenotypes and morphologic profiles, resulting in variable clinical behavior. Between 10 and 20% of all breast cancers are triple negative. Triple-negative breast cancer (TNBC) lacks the expression of human epidermal growth factor receptor 2 (HER2) and hormone receptors; therefore, to date, chemotherapy remains the backbone of treatment. TNBC tends to be aggressive and has a high histological grade, resulting in a poor 5-year prognosis. It has a high prevalence of BRCA1 mutations and an increased Ki-67 expression. This subtype usually responds well to taxanes and/or platinum compounds and poly (ADP-ribose) polymerase (PARP) inhibitors. Studies with PARP inhibitors have demonstrated promising results in the treatment of BRCA-mutated breast and ovarian cancer, and PARP inhibitors have been studied as monotherapy and in combination with cytotoxic therapy or radiotherapy. PARP inhibitor efficacy on poly (ADP-ribose) polymer (PAR) formation in vivo can be quantified by pharmacodynamic assays that measure PAR activity in peripheral blood mononuclear cells (PBMC). Biomarkers such as TP53, ATM, PALB2 and RAD51C might be prognostic or predictive indicators for treatment response, and could also provide targets for novel treatment strategies. In summary, this review provides an overview of the treatment options for basal-like TNBC, including PARP inhibitors, and focuses on the pharmacotherapeutic options in these patients.

PARP3 comes to light as a prime target in cancer therapy

Poly(ADP-ribose) polymerase 3 (PARP3) is the third member of the PARP family that catalyze a post-translational modification of proteins to promote, control or adjust numerous cellular events including genome integrity, transcription, differentiation, cell metabolism or cell death. In the late years, PARP3 has been specified for its primary functions in programmed and stress-induced double-strand break repair, chromosomal rearrangements, transcriptional regulation in the zebrafish and mitotic segregation. Still, deciphering the therapeutic value of its inhibition awaits additional investigations. In this review, we discuss the newest advancements on the specific functions of PARP3 in cancer aggressiveness exemplifying the relevance of its selective inhibition for cancer therapy.

BRCA1-No Matter How You Splice It

BRCA1 (breast cancer 1, early onset), a well-known breast cancer susceptibility gene, is a highly alternatively spliced gene. BRCA1 alternative splicing may serve as an alternative regulatory mechanism for the inactivation of the BRCA1 gene in both hereditary and sporadic breast cancers, and other BRCA1-associated cancers. The alternative transcripts of BRCA1 can mimic known functions, possess unique functions compared with the full-length BRCA1 transcript, and in some cases, appear to function in opposition to full-length BRCA1 In this review, we will summarize the functional "naturally occurring" alternative splicing transcripts of BRCA1 and then discuss the latest next-generation sequencing-based detection methods and techniques to detect alternative BRCA1 splicing patterns and their potential use in cancer diagnosis, prognosis, and therapy.

Imaging Biomarkers as Predictors for Breast Cancer Death

Background

To differentiate the risk of breast cancer death in a longitudinal cohort using imaging biomarkers of tumor extent and biology, specifically, the mammographic appearance, basal phenotype, histologic tumor distribution, and conventional tumor attributes.

Methods

Using a prospective cohort study design, 498 invasive breast cancer patients diagnosed between 1996 and 1998 were used as the test cohort to assess the independent effects of the imaging biomarkers and other predictors on the risk of breast cancer death. External validation was performed with a cohort of 848 patients diagnosed between 2006 and 2010.

Results

Mammographic tumor appearance was an independent predictor of risk of breast cancer death (P=0.0003) when conventional tumor attributes and treatment modalities were controlled. The casting type calcifications and architectural distortion were associated with 3.13-fold and 3.19-fold risks of breast cancer death, respectively. The basal phenotype independently conferred a 2.68-fold risk compared with nonbasal phenotype. The observed deaths did not differ significantly from expected deaths in the validation cohort. The application of imaging biomarkers together with other predictors classified twelve categories of risk for breast cancer death.

Conclusion

Combining imaging biomarkers such as the mammographic appearance of the tumor with the histopathologic distribution and basal phenotype, accurately predicted long-term risk of breast cancer death. The information may be relevant for determining the need for molecular testing, planning treatment, and determining the most appropriate clinical surveillance schedule for breast cancer patients.

Epigenetic modulation of BRCA-1 and MGMT genes, and histones H4 and H3 are associated with breast tumors

Aberrant patterns in promoter methylation of tumor-suppressor genes and posttranslational modifications of histone proteins are considered as major features of malignancy. In this study, we aimed to investigate promoter methylation of three tumor-suppressor genes (BRCA-1, MGMT, and P16) and three histone marks (H3K9ac, H3K18ac, and H4K20me3) in patients with breast tumors. This case-control study included 27 patients with malignant breast tumors (MBT) and 31 patients with benign breast tumors (BBT). The methylation-specific PCR was used for determining promoter methylation of BRCA-1, MGMT, and P16 genes. Western blot analysis was performed to detect histone lysine acetylation (H3K9ac and H3K18ac) and lysine methylation (H4K20me3). BRCA-1 promoter methylation was detected in 44.4% of the MBT whereas this alteration was found in 9.7% of BBT (P = 0.005). The Kaplan-Meier analysis indicated that hypermethylation in BRCA-1 promoter was significantly associated with poor overall survival of patients with breast cancer (P = 0.039). MGMT promoter methylation was identified in 18.5% of MBT and 0.0% of the BBT (P = 0.01). The frequency of P16 promoter methylation was 25.8% in BBT and 11.1% in MBT (P = 0.12). As compared with BBT, MBT samples displayed the aberrant patterns of histones marks with hypomethylation of H4K20 and hypoacetylation of H3K18 (P = 0.03 and P = 0.04, respectively). There was a negative significant correlation between H3K9ac levels and tumor size in MBT group (r = -0.672; P = 0.008). The present findings suggest that promoter hypermethylation of MGMT and BRCA-1 genes along with alterations in H3K18ac and H4K20me3 levels may have prognostic values in patients with breast cancer. Moreover, the detection of these epigenetic modifications in breast tumors could be helpful in finding new methods for breast cancer therapy.

PARP inhibition enhances tumor cell-intrinsic immunity in ERCC1-deficient non-small cell lung cancer

The cyclic GMP-AMP synthase/stimulator of IFN genes (cGAS/STING) pathway detects cytosolic DNA to activate innate immune responses. Poly(ADP-ribose) polymerase inhibitors (PARPi) selectively target cancer cells with DNA repair deficiencies such as those caused by BRCA1 mutations or ERCC1 defects. Using isogenic cell lines and patient-derived samples, we showed that ERCC1-defective non-small cell lung cancer (NSCLC) cells exhibit an enhanced type I IFN transcriptomic signature and that low ERCC1 expression correlates with increased lymphocytic infiltration. We demonstrated that clinical PARPi, including olaparib and rucaparib, have cell-autonomous immunomodulatory properties in ERCC1-defective NSCLC and BRCA1-defective triple-negative breast cancer (TNBC) cells. Mechanistically, PARPi generated cytoplasmic chromatin fragments with characteristics of micronuclei; these were found to activate cGAS/STING, downstream type I IFN signaling, and CCL5 secretion. Importantly, these effects were suppressed in PARP1-null TNBC cells, suggesting that this phenotype resulted from an on-target effect of PARPi on PARP1. PARPi also potentiated IFN-γ-induced PD-L1 expression in NSCLC cell lines and in fresh patient tumor cells; this effect was enhanced in ERCC1-deficient contexts. Our data provide a preclinical rationale for using PARPi as immunomodulatory agents in appropriately molecularly selected populations.