Molecular Tumor Boards: current practice and future needs

Background

Due to rapid technical advances, steeply declining sequencing costs, and the ever-increasing number of targeted therapies, it can be expected that extensive tumor sequencing such as whole-exome and whole-genome sequencing will soon be applied in standard care. Clinicians will thus be confronted with increasingly complex genetic information and multiple test-platforms to choose from. General medical training, meanwhile, can hardly keep up with the pace of innovation. Consequently, there is a rapidly growing gap between clinical knowledge and genetic potential in cancer care. Multidisciplinary Molecular Tumor Boards (MTBs) have been suggested as a means to address this disparity, but shared experiences are scarce in literature and no quality requirements or guidelines have been published to date.

Methods

Based on literature review, a survey among hospitals in The Netherlands, and our own experience with the establishment of a nationally operating MTB, this article evaluates current knowledge and unmet needs and lays out a strategy for successful MTB implementation.

Results

Having access to an MTB can improve and increase the application of genetics-guided cancer care. In our survey, however, <50% of hospitals and only 5% of nonacademic hospitals had access to an MTB. In addition, current MTBs vary widely in terms of composition, tasks, tools, and workflow. This may not only lead to variation in quality of care but also hinders data sharing and thus creation of an effective learning community.

Conclusions

This article acknowledges a leading role for MTBs to govern (extensive) tumor sequencing into daily practice and proposes three basic necessities for successful MTB implementation: (i) global harmonization in cancer sequencing practices and procedures, (ii) minimal member and operational requirements, and (iii) an appropriate unsolicited findings policy. Meeting these prerequisites would not only optimize MTB functioning but also improve general interpretation and application of genomics-guided cancer care.

Abstract P4-12-03: Estrogen receptor-positive breast cancer in BRCA1 mutation carriers shows a BRCAness profile, suggesting sensitivity to drugs targeting homologous recombination deficiency

Background

As estrogen receptor (ER)-positive breast cancer in BRCA1 mutation carriers arises at an older age with less aggressive tumor characteristics than ER negative BRCA1 mutated breast cancer, it has been suggested that these tumors are 'sporadic' and not BRCA1-driven. With the introduction of targeted treatments specific for tumors with a non-functioning BRCA1 or BRCA2 gene, the question whether the BRCA genes are impaired in the tumor, is highly relevant. Therefore, we performed genomic profiling of BRCA1-mutated ER+ tumors.

Methods

Genomic profiling, BRCA1 promoter methylation assessment, and loss of heterozygosity (LOH) analysis were done on 16 BRCA1-mutated ER+ tumors. Results were compared with 57 BRCA1-mutated ER- tumors, 36 BRCA2-mutated ER+ associated tumors, and 182 sporadic ER+ tumors.

Results

The genomic profile of BRCA1-mutated ER+ tumors was different from BRCA1-mutated ER- breast tumors, but highly similar to BRCA2-mutated ER+ tumors. In 83% of the BRCA1-mutated ER+ tumors, loss of the wildtype BRCA1 allele was observed. Clinico-pathological variables in BRCA1-mutated ER+ cancer were more similar to BRCA2-mutated ER+ and sporadic ER+ breast cancer than to BRCA1 mutated ER- cancers.

Conclusions

As BRCA1-mutated ER+ tumors showed a BRCAness copy number profile and LOH, it is likely that the loss of a functional BRCA1 protein plays a role in tumorigenesis in BRCA1-mutated ER+ tumors. Therefore, we hypothesize that these tumors are sensitive to drugs targeting the BRCA1 gene defect.

Citation Format: Lips EH, Debipersad R, Scheerman E, Mulder L, Sonke GS, van der Kolk LE, Wessling J, Hogervorst FBL, Nederlof PM. Estrogen receptor-positive breast cancer in BRCA1 mutation carriers shows a BRCAness profile, suggesting sensitivity to drugs targeting homologous recombination deficiency [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-12-03.

Abstract PD1-07: Comprehensive characterization of matched pre-treatment biopsies and residual disease of doxorubicin treated breast cancer

Background

Neoadjuvant chemotherapy is standard of care for locally advanced breast cancer. Unfortunately not all patients benefit from this treatment. Even after decades of research, we still cannot predict which tumor will or will not respond. This may in part be due to tumor heterogeneity, as the sample taken before treatment not necessarily represents the tumor cell population that causes therapy resistance.

Methods

To test this hypothesis, we collected pre-treatment biopsies, resection specimens, and matched blood from 21 breast cancer patients treated with doxorubicin and cyclophosphamide in a neoadjuvant setting. Specifically, tumors were selected with a tumor percentage &gt;50% after chemotherapy to enrich for resistant samples and ensure high quality data. RNA and whole exome sequencing were performed to characterize somatic mutations, copy number alterations and gene expression profiles. Histopathological characteristics were determined to obtain a comprehensive profile of all tumor samples.

Results

The comparisons of somatic variants and copy number alterations revealed a very diverse image: in several cases, high-level amplifications, large genomic gains or losses, and mutations in known oncogenes or tumor suppressors such as MAP3K1 and RUNX1 were either lost or gained during treatment, while in other cases no such changes were detected. We observed a remarkable number of genetic alterations involved in cell cycle progression and DNA damage checkpoints, including amplification of MDM2, CCND1 and CDK4, and copy number loss or mutations in CDKN1B and ATM. Strikingly, both cases of CDKN1B loss were identified in pre-treatment biopsies and no longer detectable in the surgery specimen. In contrast, CCND1, CDK4 and MDM2 amplifications were retained, although CCND1 expression decreased significantly in CCND1 amplified tumors.

In addition, eighty percent of tumors showed a decreased cell proliferation after chemotherapy, where the high-proliferative ER+ (Luminal B) tumors were most strongly affected. This trend was also visible in a validation cohort of 94 ER+ samples, but the prognosis of Luminal B tumors that showed a decrease in proliferation was still significantly worse than that of Luminal A tumors that did not show an altered proliferation rate.

Conclusion

Our results confirm that biologically relevant genomic alterations can differ between pre- and post-treatment samples, which greatly impacts biomarker discovery. In addition, our findings emphasize the chemotherapy insensitivity of CCND1 amplified ER+ breast cancers, and stress the need for better treatment regimens for these patients. In contrast, genomic loss of CDKN1B may be a marker for sensitivity to doxorubicin.

Citation Format: Lips EH, Hoogstraat M, Mulder L, Nederlof PM, Sonke GS, Rodenhuis S, Wesseling J, Wessels LFA. Comprehensive characterization of matched pre-treatment biopsies and residual disease of doxorubicin treated breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr PD1-07.

Triple-negative breast cancer: BRCAness and concordance of clinical features with BRCA1-mutation carriers

Background:

BRCAness is defined as shared tumour characteristics between sporadic and BRCA-mutated cancers. However, how to exactly measure BRCAness and its frequency in breast cancer is not known. Assays to establish BRCAness would be extremely valuable for the clinical management of these tumours. We assessed BRCAness characteristics frequencies in a large cohort of triple-negative breast cancers (TNBCs).

Methods:

As a measure of BRCAness, we determined a specific BRCA1-like pattern by array Comparative Genomic Hybridisation (aCGH), and BRCA1 promoter methylation in 377 TNBCs, obtained from 3 different patient cohorts. Clinicopathological data were available for all tumours, BRCA1-germline mutation status and chemotherapy response data were available for a subset.

Results:

Of the tumours, 66–69% had a BRCA1-like aCGH profile and 27–37% showed BRCA1 promoter methylation. BRCA1-germline mutations and BRCA1 promoter methylation were mutually exclusive events (P=1 × 10⁻⁵). BRCAness was associated with younger age and grade 3 tumours. Chemotherapy response was significantly higher in BRCA1-mutated tumours, but not in tumours with BRCAness (63% (12 out of 19) vs 35% (18 out of 52) pathological complete remission rate, respectively).

Conclusion:

The majority of the TNBCs show BRCAness, and those tumours share clinicopathological characteristics with BRCA1-mutated tumours. A better characterisation of TNBC and the presence of BRCAness could have consequences for both hereditary breast cancer screening and the treatment of these tumours.

PD03-08: BRCA1-Like Triple Negative Tumors: Clinicopathological Variables and Chemosensitivity to Alkylating Agents

Background

Our group has previously employed array Comparative Genomic Hybridization (aCGH) to assess the genomic patterns of BRCA1-mutated breast cancers. It is reasonable to assume that this pattern indicates ‘BRCAness’ and thus serves as a marker for homologous recombination deficiency. This BRCA1-like aCGH profile is also present in about half of all triple negative sporadic breast cancers and has been shown to be predictive for benefit from intensive chemotherapy with DNA crosslinking agents. To study BRCA1-like tumors and conventional dose chemotherapy sensitivity in more detail, we compared clinical factors and survival rates in a uniform cohort of triple negative breast tumors treated with alkylating agents.

Patients and methods

103 patients with triple negative tumors received conventional dose adjuvant chemotherapy with doxorubicin/cyclophosphamide. DNA was extracted from tumor samples and BRCA1-like profiles were assessed. Tumors were classified as BRCA1 -like or non-BRCA1-like. Standard clinical and histopathological factors were determined and compared between both groups. Relapse free survival (RFS), disease specific survival (DSS) and overall survival (OS) after diagnosis were compared between BRCA1-like and non-BRCA1-like tumors.

Results

66 tumors (65%) had a BRCA1-like profile, while 35 tumors (35%) did not show such a profile. Patients with BRCA1-like tumors tended to be younger and had more often node-negative disease compared to the patients with non-BRCA1-like tumors (p=0.058 and p=0.034, respectively). There was no significant difference in survival between BRCA1-like and non BRCA1-like patients after treatment with alkylating agents: the median RFS was 121 vs. 109 months, median DSS was 129 vs. 114 months and OS was 127 vs. 110 months, for BRCA1-like versus non-BRCA1-like tumors. T-stage was the only variable significantly associated with survival.

Conclusion

BRCA1-like tumors occurred in younger patients and were more often node negative, which are features shared with tumors in BRCA1-mutation carriers. We did not observe a difference in survival between BRCA1-like and non-BRCA1-like triple negative breast cancers after treatment with conventional dose chemotherapy with alkylating agents. These results confirm our previous findings that BRCA1-like tumors have similar sensitivity to anthracycline-based adjuvant chemotherapy as other triple-negative tumors. It will be important to establish whether BRCA1-like tumors also share the exquisite sensitivity of BRCA-mutated tumors to PARP-inhibitors.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD03-08.

An aCGH classifier derived from BRCA1-mutated breast cancer and benefit of high-dose platinum-based chemotherapy in HER2-negative breast cancer patients

BACKGROUND

Breast cancer cells deficient for BRCA1 are hypersensitive to agents inducing DNA double-strand breaks (DSB), such as bifunctional alkylators and platinum agents. Earlier, we had developed a comparative genomic hybridisation (CGH) classifier based on BRCA1-mutated breast cancers. We hypothesised that this BRCA1-like(CGH) classifier could also detect loss of function of BRCA1 due to other causes besides mutations and, consequently, might predict sensitivity to DSB-inducing agents.

PATIENTS AND METHODS

We evaluated this classifier in stage III breast cancer patients, who had been randomly assigned between adjuvant high-dose platinum-based (HD-PB) chemotherapy, a DSB-inducing regimen, and conventional anthracycline-based chemotherapy. Additionally, we assessed BRCA1 loss through mutation or promoter methylation and immunohistochemical basal-like status in the triple-negative subgroup (TN subgroup).

RESULTS

We observed greater benefit from HD-PB chemotherapy versus conventional chemotherapy among patients with BRCA1-like(CGH) tumours [41/230 = 18%, multivariate hazard ratio (HR) = 0.12, 95% confidence interval (CI) 0.04-0.43] compared with patients with non-BRCA1-like(CGH) tumours (189/230 = 82%, HR = 0.78, 95% CI 0.50-1.20), with a significant difference (test for interaction P = 0.006). Similar results were obtained for overall survival (P interaction = 0.04) and when analyses were restricted to the TN subgroup. Sixty-three percent (20/32) of assessable BRCA1-like(CGH) tumours harboured either a BRCA1 mutation (n = 8) or BRCA1 methylation (n = 12).

CONCLUSION

BRCA1 loss as assessed by CGH analysis can identify patients with substantially improved outcome after adjuvant DSB-inducing chemotherapy when compared with standard anthracycline-based chemotherapy in our series.

Neoadjuvant chemotherapy in ER+ HER2- breast cancer: response prediction based on immunohistochemical and molecular characteristics

A pathological complete remission (pCR) is rarely achieved by neoadjuvant chemotherapy in estrogen receptor-positive (ER+) HER2-negative (HER2-) tumors. Therefore, its use might be questionable in specific groups of this tumor type. To select which patients benefit and which could be spared neoadjuvant chemotherapy, we tested standard pathology and molecular markers in ER+ HER2- breast tumors. Pretreatment biopsies were available from 211 ER+ HER2- tumors, who had been treated with neoadjuvant chemotherapy (adriamycin/cyclophosphamide). mRNA expression data were available for 132 tumors. We determined progesterone receptor expression (PR), endocrine sensitivity, HER2 expression, histology, proliferation, and molecular subtypes. We correlated these data to chemotherapy response using pCR rates and the previously published neoadjuvant response index (NRI). PR-negative tumors (n = 65, 30.8%) and luminal B type tumors (n = 43, 20.4%) responded significantly better to chemotherapy than other tumors. These associations remained significant in multivariate analysis. However, even in the subgroup of patients with the lowest response rate, comprising tumors that had both a positive-PR expression and the luminal A subtype (n = 58, 44%), the majority of the patients had downstaging because of chemotherapy. For histology (lobular vs. ductal), endocrine sensitivity, and proliferation, no associations with chemotherapy response were observed. Gene expression array analysis resulted in 28 significant genes (FDR < 0.1). PR expression and luminal B status are associated with a better response to neoadjuvant chemotherapy. However, both markers had only weak response predictive power, and it was not possible to identify a subgroup with no or only minimal chemotherapy benefit. Therefore, the decision to refrain from neoadjuvant chemotherapy to ER+ HER2- breast tumors should not be based on predictive markers, but exclusively on estimates of prognosis.

A non-BRCA1/2 hereditary breast cancer sub-group defined by aCGH profiling of genetically related patients

Germline mutations in BRCA1 and BRCA2 explain approximately 25% of all familial breast cancers. Despite intense efforts to find additional high-risk breast cancer genes (BRCAx) using linkage analysis, none have been reported thus far. Here we explore the hypothesis that BRCAx breast tumors from genetically related patients share a somatic genetic etiology that might be revealed by array comparative genomic hybridization (aCGH) profiling. As BRCA1 and BRCA2 tumors can be identified on the basis of specific genomic profiles, the same may be true for a subset of BRCAx families. Analyses used aCGH to compare 58 non-BRCA1/2 familial breast tumors (designated BRCAx) to sporadic (non-familiar) controls, BRCA1 and BRCA2 tumors. The selection criteria for BRCAx families included at least three cases of breast cancer diagnosed before the age of 60 in the family, and the absence of ovarian or male breast cancer. Hierarchical cluster analysis was performed to determine sub-groups within the BRCAx tumor class and family heterogeneity. Analysis of aCGH profiles of BRCAx tumors indicated that they constitute a heterogeneous class, but are distinct from both sporadic and BRCA1/2 tumors. The BRCAx class could be divided into sub-groups. One subgroup was characterized by a gain of chromosome 22. Tumors from family members were classified within the same sub-group in agreement with the hypothesis that tumors from the same family would harbor a similar genetic background. This approach provides a method to target a sub-group of BRCAx families for further linkage analysis studies.

Abstract PD07-07: Indicators of Homologous Recombination Deficiency in Breast Cancer and Association with Response to Neoadjuvant Chemotherapy

Background: Tumors with homologous recombination (HR) deficiency are highly sensitive to DNA double strand break (DSB) inducing agents, such as alkylating agents and poly (ADP-ribose) polymerase (PARP)-inhibitors. BRCA1 or BRCA2- mutated tumors, which are HR deficient, have characteristic DNA gains and losses that can be assessed by an array Comparative Genomic Hybridization (aCGH) classifier, one for BRCA1 mutations and one for BRCA2 mutations. We have studied these aCGH profiles together with several other HR deficiency indicators in sporadic breast cancers and we have correlated their presence to neoadjuvant chemotherapy response.

Material and Methods: A total of 163 HER2-negative pre-treatment biopsies were examined, procured from sporadic breast cancer patients scheduled to receive neoadjuvant therapy with doxorubicin and cyclophosphamide. Triple negative (TN) and estrogen receptor positive (ER+/HER2-) tumors were analyzed separately. aCGH was performed to assess BRCA1-like and BRCA2-like profiles. In addition, BRCA1 promoter methylation, BRCA1 mRNA expression and amplification of the BRCA2-inhibiting gene EMSY were analyzed. Response to neoadjuvant treatment was assessed by measuring pathological complete remission (pCR) and near pCR at the time of surgery.

Results: Inactivation of BRCA1 was frequent in TN tumors: 57% of these tumors showed a BRCA1-like profile at aCGH. BRCA 1 promoter methylation and reduced BRCA1 mRNA expression were observed in 25% and 36% of the TN tumors, respectively. The BRCA1-like aCGH profile was not clearly associated with a better neoadjuvant treatment response (58% vs. 48%, p=0.47). In ER+ tumors, a BRCA2-like aCGH profile and the amplification of the BRCA2 inhibiting gene EMSY were frequently observed (43% and 13% respectively). A BRCA2-like aCGH profile was associated with a significantly higher response rate (35% vs. 14%, p=0.014). EMSY amplification and a BRCA2-like aCGH profile occurred together in only one case, suggesting mutual exclusivity. EMSY was not associated with treatment response, questioning the role of EMSY in HR deficiency.

Conclusion: Alterations associated with BRCA1 inactivation are present in about half of the TN breast cancers, but were not predictive of chemotherapy response. In ER+/HER2- tumors, the BRCA2-like aCGH profile predicts sensitivity to DSB-inducing chemotherapy, and possibly as well to new targeted agents, such as the PARP inhibitors. After validation in independent series the aCGH classifiers may lead to a diagnostic test that could assist in neoadjuvant treatment selection.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD07-07.

Abstract PD01-04: Histological Features of ER-Low, HER2-Negative Breast Cancer Predict Response to High Dose, Platinum-Based Chemotherapy

Background: Breast cancer cells deficient for BRCA1 are hypersensitive to agents eventually resulting in double-strand DNA breaks, such as platinating agents and poly(ADP-ribose)polymerase (PARP)-inhibitors. Using a BRCA1 array comparative genomic hybridization (aCGH) classifier, we previously identified BRCA1-like tumors with a functional BRCA1-loss, caused by BRCA1-mutation, BRCA1-promoter methylation, or an as yet unidentified mechanism. We observed that these BRCA1- like(CGH) tumors showed an expansive growth pattern, one of the histological features of BRCA1-mutated breast cancer. The aim of this study was to determine which combination of histological features associated with BRCA1-mutated breast cancer were present in the BRCA1-like(CGH) subtype and might predict sensitivity to platinating chemotherapy. Methods: We studied histological features, which are known to be associated with BRCA1-mutations in literature: growth pattern, necrosis, lymphocytic infiltrate and mitotic count. In an independent series of metastatic breast cancer patients (MBC, n=39) for which BRCA1- like(CGH) status was known, whole slides were scored for all features. Features were first tested for significant association with BRCA1- like(CGH) status. Next, significantly associated features were tried in different combinations to find the highest sensitivity to predict for BRCA1- like(CGH) status (BRCA1-histological combination). This histological combination was subsequently tested in stage-III estrogen-receptor low, HER2-negative breast cancer patients, who had been randomized between adjuvant high-dose (HD) platinum-based alkylating chemotherapy and conventional chemotherapy. Additionally, we assessed the association of BRCA1-like(aCGH) status and BRCA1-loss through mutation or promoter methylation with the histological combination in a random subgroup. Results: The combination of a ‘mitotic count above 19 per 2 mm2 with either ‘an expansive growth pattern’ or ‘necrosis’ correctly identified the BRCA1-like(CGH) tumors with a sensitivity of 88% and a specificity of 86% in the MBC patients. In the adjuvant stage-III series, greater benefit was observed from HD-platinum-based chemotherapy versus conventional chemotherapy among patients with the BRCA1-histological combination (41/136=30%, multivariate HR=0.20, 95%CI 0.07-0.62; 7-year recurrence free survival (RFS) 78% versus 39%), compared to patients with other histological features (95/136=70%, HR=0.53, 95%CI 0.29-0.95, 7-year RFS 55% versus 43%), although without a significant difference (test for interaction p=0.14). Analyses of patients with tumors with a mitotic count above 19 only, showed similar results for the BRCA1-histological combination (in this subgroup: expansive growth or necrosis, p-interaction: 0.07). The BRCA1-histological combination was significantly associated with BRCA1-like(CGH) status and BRCA1-mutations, but not with BRCA1-promoter methylation.

Conclusion: Using histology only, we were able to identify a large proportion of the aCGH defined BRCA1 molecular subtype. Here, we present the first data that histology might be a biomarker for identifying high-risk patients benefiting from platinum-based chemotherapy in the absence of molecular-based techniques.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD01-04.

Indicators of homologous recombination deficiency in breast cancer and association with response to neoadjuvant chemotherapy

BACKGROUND

Tumors with homologous recombination deficiency (HRD), such as BRCA1-associated breast cancers, are not able to reliably repair DNA double-strand breaks (DSBs) and are therefore highly sensitive to both DSB-inducing chemotherapy and poly (ADP-ribose) polymerase inhibitors. We have studied markers that may indicate the presence of HRD in HER2-negative breast cancers and related them to neoadjuvant chemotherapy response.

PATIENTS AND METHODS

Array comparative genomic hybridization (aCGH), BRCA1 promoter methylation, BRCA1 messenger RNA (mRNA) expression and EMSY amplification were assessed in 163 HER2-negative pretreatment biopsies from patients scheduled for neoadjuvant chemotherapy.

RESULTS

Features of BRCA1 dysfunction were frequent in triple-negative (TN) tumors: a BRCA1-like aCGH pattern, promoter methylation and reduced mRNA expression were observed in, respectively, 57%, 25% and 36% of the TN tumors. In ER+ tumors, a BRCA2-like aCGH pattern and the amplification of the BRCA2 inhibiting gene EMSY were frequently observed (43% and 13%, respectively) and this BRCA2-like profile was associated with a better response to neoadjuvant chemotherapy.

CONCLUSIONS

Abnormalities associated with BRCA1 inactivation are present in about half of the TN breast cancers but were not predictive of chemotherapy response. In ER+/HER2- tumors, a BRCA2-like aCGH pattern was predictive of chemotherapy response. These findings should be confirmed in independent series.

Goblet cell carcinoid of the appendix: a specific type of carcinoma

AIMS

Goblet cell carcinoid is a poorly understood tumour of the appendix. The aim of this study was to determine whether it should be regarded as a separate entity or as a variant of classical carcinoid.

METHODS AND RESULTS

The immunohistochemical expression pattern of 21 markers and the mutation status of KRas codon 12 were determined in 16 goblet cell carcinoids and compared with 14 classical carcinoids, 19 colonic adenocarcinomas and 10 appendiceal mucinous cystadeno (carcino)mas. The results were subjected to a stepwise linear discriminant analysis. Goblet cell carcinoids were significantly different from the control groups. The most important markers for discriminating between the groups were CEA (classical carcinoid versus all others), KRas mutation (present in all mucinous cystadeno (carcino)mas), beta-catenin (goblet cell carcinoid versus left sided colonic adenocarcinoma) and chromogranin (goblet cell carcinoid versus right sided colonic adenocarcinoma). Expression of Math1 and HD5 was similar in goblet cell carcinoid and colonic adenocarcinoma but absent in classical carcinoid.

CONCLUSION

The results suggest that goblet cell carcinoids should be regarded as a separate entity. The formerly used term 'crypt cell carcinoma' may be more appropriate because it reflects the more aggressive clinical behaviour of these tumours as well as their greater similarity to adenocarcinomas rather than to carcinoids.

EGFR and KRAS mutations as criteria for treatment with tyrosine kinase inhibitors: retro- and prospective observations in non-small-cell lung cancer

Results of individualized therapy guided by mutational tumor profile of patients with non-small-cell lung cancer are presented. After confirming the importance of epidermal growth factor receptor (EGFR) and KRAS mutations for (non)response on gefitinib in a retrospective series of patients, EGFR mutations were looked for before--and were a condition for--treatment with gefitinib or erlotinib. To increase the chance to find such a mutation, we selected patients on the basis of smoking status, gender and histopathology. Out of 41 patients selected, 13 (32%) were found to harbor an EGFR mutation. In nine of them it concerned deletions in exon 19 and in none of them KRAS mutations were detected. All nine patients with an exon 19 deletion had a favorable and continuing response to tyrosine kinase inhibitors (TKIs), while four other patients with point mutations responded less favorably: stable disease or a response of short duration. These observations confirm the potential role of EGFR and KRAS mutations in predicting (non)response to TKIs. Exon 19 deletions that are associated with the best responses might be used for first-line treatment selection, while KRAS mutations could play a role in excluding patients from treatment with TKIs.

The mutation status of the epidermal growth factor receptor (EGFR) as a selection criterion for therapy with EGFR tyrosine kinase inhibitors (TKI’s) in non-small cell lung cancer (NSCLC)

10073

Background: Somatic mutations in the EGFR gene have been shown to be closely associated with a favorable response to small-molecule TKI’s, while K-ras mutations seem to be associated with primary resistance. We present an exploratory study confirming the importance of mutation status for response on anti EGFR therapy. Methods: Mutations in the EGFR TK domain were looked for in tumor material extracted from two series of patients with advanced NSCLC. In the first series, mutations were determined in patients with an objective response or clearly progressive under gefitinib therapy. In the second series, EGFR mutations were determined prospectively in an enriched population (two of three characteristics: female gender, non-smoking status, bronchoalveolar -or adenocarcinoma pathology). The presence of a mutation was the criterion for treatment with TKI’s. Response assessment was done according to RECIST. K-Ras mutations were determined retrospectively. Results: In the retrospective series, 15 biopsies were analyzed, belonging to 3 complete responders and 12 non-responders (gefitinib). All three responders harbored an EGFR mutation, none had a K-ras mutation. None of the non-responders had an EGFR mutation. Three of them had a K-ras mutation. In the prospective (enriched) series, 13 out of 41 patients (tumors) possessed an EGFR mutation. Eleven of them swiftly responded on erlotinib or gefitinib, 1 had stable disease, 1 stopped treatment due to severe toxicity. K-ras mutations were not found in this set. In a single EGFR mutation positive patient survival has extended over 40 months since start of therapy. Conclusions: Our findings corroborate other groups’ conclusions that EGFR mutations are a powerful indicator of response to TKI’s and that K-ras mutations are associated with resistance.

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A multiplex PCR predictor for aCGH success of FFPE samples

Formalin-fixed, paraffin-embedded (FFPE) tissue archives are the largest and longest time-spanning collections of patient material in pathology archives. Methods to disclose information with molecular techniques, such as array comparative genomic hybridisation (aCGH) have rapidly developed but are still not optimal. Array comparative genomic hybridisation is one efficient method for finding tumour suppressors and oncogenes in solid tumours, and also for classification of tumours. The fastest way of analysing large numbers of tumours is through the use of archival tissue samples with first, the huge advantage of larger median follow-up time of patients studied and second, the advantage of being able to locate and analyse multiple tumours, even across generations, from related individuals (families). Unfortunately, DNA from archival tissues is not always suitable for molecular analysis due to insufficient quality. Until now, this quality remained undefined. We report the optimisation of a genomic-DNA isolation procedure from FFPE pathology archives in combination with a subsequent multiplex PCR-based quality-control that simply identified all samples refractory to further DNA-based analyses.

Quality control in diagnostic molecular pathology in the Netherlands; proficiency testing for patient identification in tissue samples

AIMS

To describe the evolution of proficiency testing for molecular diagnostic pathology with respect to determining unambiguously the patient identity of tissue samples by microsatellite analysis.

METHOD

Four rounds of quality control exchanges of samples from different patients were sent with the purpose of identifying the correct origin of these samples. The samples were either paraffin wax embedded sections on glass, sections in tubes, or isolated DNA. Blinded samples were distributed to all participating laboratories. No restrictions to the method and short tandem repeat markers used for identification were imposed.

RESULTS

In four subsequent rounds the number of participating laboratories increased from three to 10. The numbers of samples tested increased in time from five to 12. The microsatellite markers used by the different laboratories showed little overlap. In the first three rounds, in which isolated DNA was provided, all samples were accurately classified irrespective of the microsatellite markers used. In the last round, which also included paraffin wax embedded sections, a small number of laboratories experienced problems, either with amplification or incorrect classification of a few samples.

CONCLUSION

Proficiency testing was useful, and showed country wide high quality and correct identification of (patient) samples with molecular techniques for diagnostic purposes.

Genomic deletions of MSH2 and MLH1 in colorectal cancer families detected by a novel mutation detection approach

Hereditary non-polyposis colorectal cancer is an autosomal dominant condition due to germline mutations in DNA-mismatch-repair genes, in particular MLH1, MSH2 and MSH6. Here we describe the application of a novel technique for the detection of genomic deletions in MLH1 and MSH2. This method, called multiplex ligation-dependent probe amplification, is a quantitative multiplex PCR approach to determine the relative copy number of each MLH1 and MSH2 exon. Mutation screening of genes was performed in 126 colorectal cancer families selected on the basis of clinical criteria and in addition, for a subset of families, the presence of microsatellite instability (MSI-high) in tumours. Thirty-eight germline mutations were detected in 37 (29.4%) of these kindreds, 31 of which have a predicted pathogenic effect. Among families with MSI-high tumours 65.7% harboured germline gene defects. Genomic deletions accounted for 54.8% of the pathogenic mutations. A complete deletion of the MLH1 gene was detected in two families. The multiplex ligation-dependent probe amplification approach is a rapid method for the detection of genomic deletions in MLH1 and MSH2. In addition, it reveals alterations that might escape detection using conventional diagnostic techniques. Multiplex ligation-dependent probe amplification might be considered as an early step in the molecular diagnosis of hereditary non-polyposis colorectal cancer.

A tumour with a neuroendocrine and papillary serous component: two or a pair?

AIMS

To examine the clonal origin of a tumour, made up of a neuroendocrine component and a papillary serous component by comparing the pattern of loss of heterozygosity (LOH) and the immunohistochemical protein expression of both components.

METHODS/RESULTS

A 70 year old woman, known to have a metastasised neuroendocrine carcinoma, underwent resection of the distal part of the ileum because of obstruction by a mesenterial mass. The macroscopically homogeneous mesenterial mass consisted histologically of an admixture of a neuroendocrine component and a papillary serous carcinoma. Loss of heterozygosity (LOH) analysis of both components with a panel of 15 polymorphic microsatellite markers showed a distinctive pattern of LOH, and both components showed LOH on chromosome 4q and 17, but involving different alleles at the same locus. Moreover, both components showed different immunohistochemical staining patterns for neuroendocrine markers, cytokeratin 7, carcinoembryonic antigen, and CA125.

CONCLUSION

Both LOH analysis of the neuroendocrine and papillary serous components of this tumour and the immunohistochemical profile of both components are consistent with a different clonal origin. The tumour is probably a collision tumour, in which the papillary serous carcinoma must have been of peritoneal origin because necropsy revealed a normal uterus and normal ovaries.

Senescence bypass screen identifies TBX2, which represses Cdkn2a (p19(ARF)) and is amplified in a subset of human breast cancers

To identify new immortalizing genes with potential roles in tumorigenesis, we performed a genetic screen aimed to bypass the rapid and tight senescence arrest of primary fibroblasts deficient for the oncogene Bmi1. We identified the T-box member TBX2 as a potent immortalizing gene that acts by downregulating Cdkn2a (p19(ARF)). TBX2 represses the Cdkn2a (p19(ARF)) promoter and attenuates E2F1, Myc or HRAS-mediated induction of Cdkn2a (p19(ARF)). We found TBX2 to be amplified in a subset of primary human breast cancers, indicating that it might contribute to breast cancer development.

The import pathway of human and Thermoplasma 20S proteasomes into HeLa cell nuclei is different from that of classical NLS-bearing proteins

Wild-type proteasomes of human erythrocytes and the archaeon Thermoplasma acidophilum compete with each other for transport into nuclei of digitonin-permeabilized HeLa cells in the presence of an energy-regenerating system and rabbit reticulocyte lysate. 'NLS'-mutated Thermoplasma proteasomes were also able to compete with human proteasomes in the same assay, although with lower efficiency. Furthermore, in contrast to the other archaeal and bacterial cell lysates tested, the Thermoplasma cytosol efficiently supported nuclear import of human and Thermoplasma proteasomes. However, the same lysate could barely direct the nuclear transport of BSA-NLSsv40 peptide conjugates or the classical NLS-bearing protein, nucleoplasmin. Finally, additional importin alpha/beta significantly decreased the import efficiency of both human and Thermoplasma proteasomes. Taken together, these results suggest that nuclear import of proteasomes may use a novel pathway that is different from that of classical NLS-bearing proteins.

Import of human and Thermoplasma 20S proteasomes into nuclei of HeLa cells requires functional NLS sequences

Proteasomes are present both in the nucleus and cytoplasm of eukaryotic cells. Their localization is regulated and changes during the cell cycle. Nuclear localization signal (NLS) type sequences were identified in proteasomes from various organisms. In addition, acidic complementary sequences were identified (cNLS) which could interact with the positively charged NLS, masking or unmasking them and thereby modulating nuclear import. In this paper we show that fluorescently labeled human erythrocyte 20S proteasomes accumulate in the nucleus of digitonin-permeabilized cells. This translocation is ATP-dependent and occurs through the nuclear pore complex as is shown by blocking of the nuclear pores with wheat germ agglutinin. In addition, we used 20S proteasomes from Thermoplasma acidophilum as a model system. Recombinant 20S proteasomes from the archaebacterium Thermoplasma acidophilum are imported into nuclei of HeLa and 3T3 cells similar to their eukaryotic counterpart. We constructed mutants in the putative NLS and cNLS region to study their effect on import. The NLS mutant was not imported into nuclei and showed cytoplasmic staining only. This indicates that this sequence is indeed responsible for nuclear targeting. Mutational studies of the cNLS do not support the involvement of this sequence in regulation of nuclear transport.

Proteasome: from structure to function

During the past two years, significant progress has been made in understanding the structure and function of the proteasome. Recent work has revealed the three-dimensional structure of the 700 kDa proteolytic complex at atomic resolution and elucidated its novel catalytic mechanism. Close relationships to a number of other amino-terminal hydrolases have emerged, making the proteasomal subunits the prototype of this newly discovered structural superfamily.

Nuclear localization signals of human and Thermoplasma proteasomal alpha subunits are functional in vitro

Proteasomes are located both in the nuclei and in the cytoplasm of eukaryotic cells. Active transport of these complexes through the nuclear pores has been proposed to be mediated by nuclear localization signals (NLS), which have been found in several of the alpha-type proteasomal subunits. We have tested three different putative NLS sequences from human alpha-type proteasomal subunits (Hsc iota, Hsc9, and Hsc3), as well as a putative NLS-type sequence from the archaeon Thermoplasma acidophilum, for their ability to direct non-nuclear proteins to the nucleus. Synthetic peptides containing these putative NLS sequences were generated and conjugated to large fluorescent reporter molecules: allophycocyanin or fluorescein-labeled bovine serum albumin. The conjugates were introduced into digitonin-permeabilized HeLa and 3T3 cells in the presence of cell lysate and ATP, and nuclear import was monitored by fluorescence microscopy. All three putative NLS sequences from human proteasomal subunits were able to direct the reporter molecules to the nucleus in both cell types, although differences in efficiency were observed. Substitution of threonine for the first lysine residue of the eukaryotic NLS motifs inhibited nuclear import completely. Interestingly, the putative NLS sequence found in T. acidophilum was also functional as a nuclear targeting sequence.

Radiation-induced changes in nucleoid halo diameters of aerobic and hypoxic SF-126 human brain tumor cells

Nucleoid halo diameters were measured to assay changes in DNA supercoiling in human brain tumor cell line SF-126 after irradiation under aerobic or hypoxic conditions. In unirradiated aerobic cells, a typical propidium iodide titration curve showed that with increasing concentrations of propidium iodide, the halo diameter increased and then decreased with the unwinding and subsequent rewinding of DNA supercoils. In irradiated cells, the rewinding of DNA supercoils was inhibited, resulting in an increased halo diameter, in a radiation dose-dependent manner. To produce equal increases in halo diameter required about a threefold higher radiation dose in hypoxic cells than in aerobic cells. Quantitatively similar differences in the radiation sensitivities of hypoxic and aerobic cells were demonstrated by a colony-forming efficiency assay. These findings suggest that the nucleoid halo assay may be used as a rapid measure of the inherent radiation sensitivity of human tumors.

Thick-section fluorescence in situ hybridization on formalin-fixed, paraffin-embedded archival tissue provides a histogenetic profile

Fluorescence in situ hybridization has become a major tool for analysis of gene and chromosome copy number in normal and malignant tissue. The technique has been applied widely to fresh tissue and dispersed formalin-fixed, paraffin-embedded archival tissue, but its use on sections of archival tissue has largely been limited to sections < 6 mu thick. This does not provide intact, uncut nuclei for accurate analysis of gene or chromosome copy number. We report here a method of hybridization to sections > 20 microns thick that overcomes these difficulties. Key developments were the use of DNA probes directly labeled with fluorochromes and optical sectioning using laser-scanning confocal microscopy.

Fluorescence ratio measurements of double-labeled probes for multiple in situ hybridization by digital imaging microscopy

To expand the multiplicity of the in situ hybridization (ISH) procedure, which is presently limited by the number of fluorochromes spectrally separable in the microscope, a digital fluorescence ratio method is proposed. For this purpose, chromosome-specific repetitive probes were double-labeled with two haptens and hybridized to interphase nuclei of human peripheral blood lymphocytes. The haptens were immunocytochemically detected with specific antibodies conjugated with the fluorochromes FITC or TRITC. The FITC and TRITC fluorescence intensities of spots obtained with different double-haptenized probes were measured, and the fluorescence ratio was calculated for each ISH spot. Combinations of different haptens, such as biotin, digoxigenin, fluorescein, sulfonate, acetyl amino fluorene (AAF), and mercury (Hg) were used. The fluorescence intensity ratio (FITC/TRITC) of the ISH spots was fairly constant for all combinations used, with coefficients of variation between 10 and 30%. To study the feasibility of a probe identification procedure on the basis of probe hapten ratios, one probe was double-labeled with different ratios, by varying the relative concentrations of the modified nucleotides (biotin-11-dUTP and digoxigenin-11-dUTP) in the nick-translation reaction. Measurement of the FITC and TRITC intensities of the ISH spots showed that the concentration of modified nucleotides used in the labeling procedures was reflected in the mean fluorescence intensity of the ISH spots. Furthermore, the ratio distributions showed little overlap due to the relatively small coefficients of variation. The results indicate that a multiple ISH procedure based on fluorescence ratio imaging of double-labeled probes is feasible.

Quantification of inter- and intra-nuclear variation of fluorescence in situ hybridization signals

This study aims at the quantification of specific DNA sequences by using fluorescence in situ hybridization (ISH) and digital imaging microscopy. The cytochemical and cytometric aspects of a quantitative ISH procedure were investigated, using human peripheral blood lymphocyte interphase nuclei and probes detecting high copy number target sequences as a model system. These chromosome-specific probes were labeled with biotin, digoxigenin, or fluorescein. Quantification of the fluorescence ISH signals was performed using an epifluorescence microscope equipped with a multi-wavelength illuminator, and a cooled charge coupled device (CCD) camera. Specific image analysis programs were developed for the segmentation and analysis of the images provided by ISH. The fluorescence intensity distributions of the ISH spots showed large internuclear variation (CVs up to 65%) for the probes used. The variation in intensity was found to be independent of the probe, the type of labeling, and the type of immunocytochemical detection used. Variation in intensity was not caused primarily by the immunocytochemical detection method, since directly fluorescein-labeled probes showed similar internuclear variation. Furthermore, it was found that different white blood cell types, which harbor different degrees of compactness of the nuclear chromatin, showed the same variation. The intra-nuclear variation in intensity of the ISH spots on the two chromosome homologs within one nucleus was significantly smaller (approximately 20%) than the inter-nuclear variation, probably due to more constant local hybridization conditions. Due to the relatively small intranuclear variation, copy number polymorphisms of the satellite DNA sequence on chromosome 1 could readily be quantified.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of fluorescence in situ hybridization signals by image cytometry

In this study we aimed at the development of a cytometric system for quantification of specific DNA sequences using fluorescence in situ hybridization (ISH) and digital imaging microscopy. The cytochemical and cytometric aspects of a quantitative ISH procedure were investigated, using human peripheral blood lymphocyte interphase nuclei and probes detecting high copy number target sequences as a model system. These chromosome-specific probes were labeled with biotin, digoxigenin, or fluorescein. The instrumentation requirements are evaluated. Quantification of the fluorescence ISH signals was performed using an epi-fluorescence microscope with a multi-wavelength illuminator, equipped with a cooled charge couple device (CCD) camera. The performance of the system was evaluated using fluorescing beads and a homogeneously fluorescing specimen. Specific image analysis programs were developed for the automated segmentation and analysis of the images provided by ISH. Non-uniform background fluorescence of the nuclei introduces problems in the image analysis segmentation procedures. Different procedures were tested. Up to 95% of the hybridization signals could be correctly segmented using digital filtering techniques (min-max filter) to estimate local background intensities. The choice of the objective lens used for the collection of images was found to be extremely important. High magnification objectives with high numerical aperture, which are frequently used for visualization of fluorescence, are not optimal, since they do not have a sufficient depth of field. The system described was used for quantification of ISH signals and allowed accurate measurement of fluorescence spot intensities, as well as of fluorescence ratios obtained with double-labeled probes.

Gene amplification in human cells may involve interchromosomal transposition and persistence of the original DNA region

In tumor cells in vivo and in vitro the amplification of large DNA sequences is a spontaneous and frequently occurring genetic event. We have used human cells to study independent events leading to a low level of amplification of a single copy of an integrated plasmid. Fluorescence in situ hybridization, chromosome banding, and chromosome painting revealed that the new amplified DNA sequences can become located on chromosomes that are totally unrelated to the chromosome that harbors the original DNA sequences, indicating that the transposition of amplified DNA sequences is interchromosomal. In cells containing amplified DNA sequences the integrated single-copy plasmid remained at its original location. The unit of amplification contained a DNA fragment of at least a 800 kb and the same fragment was also present in the parental single-copy cell clone. The data suggest that a doubling of the DNA region at the original location precedes or is coupled to gene amplification.

In situ hybridization with fluoresceinated DNA

We have used fluorescein-11-dUTP in a nick-translation format to produce fluoresceinated human nucleic acid probes. After in situ hybridization of fluoresceinated DNAs to human metaphase chromosomes, the detection sensitivity was found to be 50-100 kb. The feasibility and the increase in detection sensitivity of microscopic imaging of in situ hybridized, fluoresceinated DNA with an integrating solid state camera for rapid cosmid mapping is illustrated. Combination of fluoresceinated DNA with biotinated and digoxigeninated DNAs allowed easy performance of triple fluorescence in situ hybridization. The potential of these techniques for DNA mapping, cytogenetics and biological dosimetry is briefly discussed.

Multiple fluorescence in situ hybridization

A method for multiple fluorescence in situ hybridization is described allowing the simultaneous detection of more than three target sequences with only three fluorescent dyes (FITC, TRITC, AMCA), respectively emitting in the green, red, and blue. This procedure is based on the labeling of (DNA) probes with more than one hapten and visualisation in multiple colors. The possibility to detect multiple targets simultaneously is important for prenatal diagnosis and the detection of numerical and/or structural chromosome aberrations in tumor diagnosis. It may form the basis for an in situ hybridization based chromosome banding technique.

Human gametes and zygotes studied by nonradioactive in situ hybridization

A nonradioactive in situ hybridization technique was applied to human gametes and abnormally fertilized or developed zygotes. Using haptenized chromosome-specific probes, visualization was obtained using immunocytochemistry to achieve a fluorescent stain on specific hybrids. Using a chromosome 1-specific DNA probe, almost all spermatozoa gave a positive result, i.e., one hybridization signal per cell could be observed. Furthermore, it was possible to identify sperm cells with two spots, suggesting nondisjunction. Two cleavage arrested embryos from different patients showed both: two brightly fluorescent spots and two weaker spots with the same DNA probe. Using a Y-specific DNA probe the percentages of positive spermatozoa from the normal males ranged between 48.1% and 49.1%. In an embryo with four grossly haploid chromosome sets, three fluorescent spots were obtained with the Y-specific DNA probe, indicating the penetration of three spermatozoa.

Detection of chromosome aberrations in interphase tumor nuclei by nonradioactive in situ hybridization

In a blind study, chromosome aberrations in tumor cells were analyzed by conventional cytogenetic techniques (G banding) and nonradioactive in situ hybridization with chromosome-specific probes. The material was obtained directly from patients with hematologic diseases and from colon tumor derived cell lines. The cytogenetic data obtained with G banding were in accord with those obtained by in situ hybridization to metaphase chromosomes. Most importantly, in situ hybridization to interphase nuclei gave reliable results and even allowed detection of cell subpopulations that were not detected by analyzing metaphase chromosomes. Furthermore, in retrospect, even structural aberrations could be detected in interphase nuclei; abnormal cells with either an i(1q) or a translocation der(1)t(1;7) could be identified. Our results show that the application of in situ hybridization in combination with routine cytogenetic techniques offers significant advantages for cytogenetic analysis of solid tumors and hematologic malignancies.

Three-color fluorescence in situ hybridization for the simultaneous detection of multiple nucleic acid sequences

A method is described for visualizing three nucleic acid sequences simultaneously by in situ hybridization using a new blue immunofluorescent label, amino methyl coumarin acetic acid (AMCA), in combination with green and red fluorescing FITC and TRITC. Three chromosome-specific repetitive probes labeled with either amino acetyl fluorene (AAF), mercury, or biotin were hybridized simultaneously to metaphase chromosomes prepared from human blood lymphocytes or to interphase tumor nuclei. Conditions for the combined use of three immunocytochemical affinity systems as well as the optimal spectral separation of the three fluorescing labels have been determined. Three-color in situ hybridization was applied to the study of numerical chromosome abnormalities as occur in human solid tumors. Further applications of this method in prenatal diagnosis for the detection of aneuploidy of the most frequently involved autosomes, as well as for the quantification of gene copy number and mRNA expression, are discussed.