High-dose alkylating chemotherapy in BRCA-altered triple-negative breast cancer: the randomized phase III NeoTN trial

Exploratory analyses of high-dose alkylating chemotherapy trials have suggested that BRCA1 or BRCA2-pathway altered (BRCA-altered) breast cancer might be particularly sensitive to this type of treatment. In this study, patients with BRCA-altered tumors who had received three initial courses of dose-dense doxorubicin and cyclophosphamide (ddAC), were randomized between a fourth ddAC course followed by high-dose carboplatin-thiotepa-cyclophosphamide or conventional chemotherapy (initially ddAC only or ddAC-capecitabine/decetaxel [CD] depending on MRI response, after amendment ddAC-carboplatin/paclitaxel [CP] for everyone). The primary endpoint was the neoadjuvant response index (NRI). Secondary endpoints included recurrence-free survival (RFS) and overall survival (OS). In total, 122 patients were randomized. No difference in NRI-score distribution (p = 0.41) was found. A statistically non-significant RFS difference was found (HR 0.54; 95% CI 0.23-1.25; p = 0.15). Exploratory RFS analyses showed benefit in stage III (n = 35; HR 0.16; 95% CI 0.03-0.75), but not stage II (n = 86; HR 1.00; 95% CI 0.30-3.30) patients. For stage III, 4-year RFS was 46% (95% CI 24-87%), 71% (95% CI 48-100%) and 88% (95% CI 74-100%), for ddAC/ddAC-CD, ddAC-CP and high-dose chemotherapy, respectively. No significant differences were found between high-dose and conventional chemotherapy in stage II-III, triple-negative, BRCA-altered breast cancer patients. Further research is needed to establish if there are patients with stage III, triple negative BRCA-altered breast cancer for whom outcomes can be improved with high-dose alkylating chemotherapy or whether the current standard neoadjuvant therapy including carboplatin and an immune checkpoint inhibitor is sufficient. Trial Registration: NCT01057069.

Identifying the BRCA1 c.-107A > T variant in Dutch patients with a tumor BRCA1 promoter hypermethylation

An inherited single nucleotide variant (SNV) in the 5'UTR of the BRCA1 gene c.-107A > T was identified to be related to BRCA1 promoter hypermethylation and a hereditary breast and ovarian cancer phenotype in two UK families. We investigated whether this BRCA1 variant was also present in a Dutch cohort of breast and ovarian cancer patients with tumor BRCA1 promoter hypermethylation. We selected all breast and ovarian cancer cases that tested positive for tumor BRCA1 promoter hypermethylation at the Netherlands Cancer Institute and Sanger sequenced the specific mutation in the tumor DNA. In total, we identified 193 tumors with BRCA1 promoter hypermethylation in 178 unique patients. The wild-type allele was identified in 100% (193/193) of sequenced tumor samples. In a large cohort of 178 patients, none had tumors harboring the previously identified c.-107A > T SNV in BRCA1. We therefore can conclude that the germline SNV is not pervasive in patients with tumor BRCA1 promoter hypermethylation.

Effect of HIPEC according to HRD/BRCAwt genomic profile in stage III ovarian cancer - results from the phase III OVHIPEC trial

The addition of hyperthermic intraperitoneal chemotherapy (HIPEC) with cisplatin to interval cytoreductive surgery improves recurrence-free (RFS) and overall survival (OS) in patients with stage III ovarian cancer. Homologous recombination deficient (HRD) ovarian tumors are usually more platinum sensitive. Since hyperthermia impairs BRCA1/2 protein function, we hypothesized that HRD tumors respond best to treatment with HIPEC. We analyzed the effect of HIPEC in patients in the OVHIPEC trial, stratified by HRD status and BRCAm status. Clinical data and tissue samples were collected from patients included in the randomized, phase III OVHIPEC-1 trial. DNA copy number variation (CNV) profiles, HRD-related pathogenic mutations, and BRCA1 promotor hypermethylation were determined. CNV-profiles were categorized as HRD or non-HRD, based on a previously validated algorithm-based BRCA1-like classifier. Hazard ratios (HR) and corresponding 99% confidence intervals (CI) for the effect of RFS and OS of HIPEC in the BRCAm, the HRD/BRCAwt and the non-HRD group were estimated using Cox proportional hazard models. DNA was available from 200/245 (82%) patients. Seventeen (9%) tumors carried a pathogenic mutation in BRCA1 and 14 (7%) in BRCA2. Ninety-one (46%) tumors classified as BRCA1-like. The effect of HIPEC on RFS and OS was absent in BRCAm tumors (HR 1.25; 99%CI 0.48-3.29), and most present in HRD/BRCAwt (HR 0.44; 99%CI 0.21-0.91), and non-HRD/BRCAwt tumors (HR 0.82; 99%CI 0.48-1.42), interaction p-value: 0.024. Patients with HRD tumors without pathogenic BRCA1/2 mutation appear to benefit most from treatment with HIPEC, while benefit in patients with BRCA1/2 pathogenic mutations and patients without HRD seems less evident.

Abstract GS2-09: Tamoxifen instigates uterine cancer development by activating PI3K signaling and supersedes PIK3CA driver mutations

Tamoxifen is widely used in the adjuvant treatment of estrogen receptor–positive (ER+) breast cancer and is an important drug for pre-menopausal women and post-menopausal patients who cannot tolerate aromatase inhibitors. Despite the clear clinical benefit in improving relapse-free and overall survival in these patients, an adverse effect of tamoxifen is a 2- to 7-fold increased risk of uterine cancer (UC) after 2-5 years of treatment. To date, the mechanism of tamoxifen-driven tumorigenesis is not well understood, and preventive approaches are lacking. Here, to molecularly characterize tamoxifen-associated uterine cancers (TA-UCs) and gain insights into their unique evolution, we performed whole-exome sequencing of 21 TA-UCs (discovery cohort) and droplet digital PCR (ddPCR) of an additional 40 TA-UCs (validation cohort) obtained from the ‘Tamoxifen Associated Malignancies: Aspects of Risk’ (TAMARISK) study. In addition, we used in vivo mouse models to: (i) further investigate tamoxifen-activated molecular pathways that may be involved in TA-UC tumorigenesis; and (ii) offer mechanistic insights. Overall, we discovered that TA-UCs were genomically similar to non–TA-UCs from The Cancer Genome Atlas (TCGA) project, with one profound exception: TA-UCs are characterized by a lower-than-expected frequency of mutations in two highly prevalent UC driver genes in the PI3K pathway: PIK3CA (14% [3/21] vs 48% [265/554] in non–TA-UC; P=0.003, Fisher’s exact test; Q=0.02, Benjamini-Hochberg FDR) and PIK3R1 (0%, [0/21] vs 31% [174/554]; P=0.001; Q=0.01). We used ddPCR in the independent TA-UC validation cohort and confirmed the low frequency of mutations in PIK3CA (7.5% [3/40] vs 21% [144/685] in control UCs from the Dana-Farber contribution to the AACR GENIE project; P=0.04). We next performed mouse in vivo studies and demonstrated that tamoxifen activated the PI3K pathway and increased cell proliferation in normal mouse uterine tissue through paracrine and autocrine effects, both of which were abrogated by the PI3K inhibitor alpelisib. Taken together, we describe a distinct and novel pathway of carcinogenesis in which tamoxifen acts as a driver event in the uterus and promotes tumor development in a mutation-independent manner. Indeed, tamoxifen may increase the risk of UC by activating the PI3K pathway, which can substitute for the early acquisition of oncogenic PIK3CA or PIK3R1 mutations observed in non–TA-UC tumors. Furthermore, the ability of a PI3K inhibitor to reduce cell proliferation in our mouse model raises the possibility that downregulating the PI3K pathway may prevent or significantly reduce TA-UC development, offering a potential future therapeutic and prevention strategy for specific high-risk patients undergoing tamoxifen therapy.

Citation Format: Kirsten Kubler, Agostina Nardone, Shankara Anand, Daniel Gorvich, Marjolein Droog, Francisco Hermida-Prado, Tara Akshi, Avery S Feit, Gabriella Cohen, Gwen Dackus, Matthew Pun, Yanan Kuang, Justin Cha, Mendy Miller, William J Gibson, Cloud P Paweletz, Eliezer M Van Allen, Flora E van Leeuwen, Petra Nederlof, Harry Hollema, Quang-Dé Nguyen, Marian JE Mourits, Ignaty Leshchiner, Chip Stewart, Ursula A Matulonis, Wilbert Zwart, Yosef E Maruvka, Gad Getz, Rinath Jeselsohn. Tamoxifen instigates uterine cancer development by activating PI3K signaling and supersedes PIK3CA driver mutations [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS2-09.

Carboplatin-Cyclophosphamide or Paclitaxel without or with Bevacizumab as First-Line Treatment for Metastatic Triple-Negative Breast Cancer (BOOG 2013-01)

Background

The addition of bevacizumab to chemotherapy conferred a modest progression-free survival (PFS) benefit in metastatic triple-negative breast cancer (mTNBC). However, no overall survival (OS) benefit has been reported. Also, its combination with carboplatin-cyclophosphamide (CC) has never been investigated.

Methods

The Triple-B study is a multicenter, randomized phase IIb trial that aims to prospectively validate predictive biomarkers, including baseline plasma vascular endothelial growth factor receptor-2 (pVEGFR-2), for bevacizumab benefit. mTNBC patients were randomized between CC and paclitaxel (P) without or with bevacizumab (CC ± B or P ± B). Here we report on a preplanned safety and preliminary efficacy analysis after the first 12 patients had been treated with CC+B and on the predictive value of pVEGFR-2.

Results

In 58 patients, the median follow-up was 22.1 months. Toxicity was manageable and consistent with what was known for each agent separately. There was a trend toward a prolonged PFS with bevacizumab compared to chemotherapy only (7.0 vs. 5.2 months; adjusted HR = 0.60; 95% CI 0.33-1.08; p = 0.09), but there was no effect on OS. In this small study, pVEGFR-2 concentration did not predict a bevacizumab PFS benefit. Both the intention-to-treat analysis and the per-protocol analysis did not yield a significant treatment-by-biomarker test for interaction (p_interaction = 0.69).

Conclusions

CC and CC+B are safe first-line regimens for mTNBC and the side effects are consistent with those known for each individual agent. pVEGFR-2 concentration did not predict a bevacizumab PFS benefit.

POSEIDON Trial Phase 1b Results: Safety, Efficacy and Circulating Tumor DNA Response of the Beta Isoform-Sparing PI3K Inhibitor Taselisib (GDC-0032) Combined with Tamoxifen in Hormone Receptor Positive Metastatic Breast Cancer Patients

PURPOSE

The strategy of combining endocrine therapy with PI3K-mTOR inhibition has shown promise in estrogen receptor (ER)-positive breast cancer, but new agents and combinations with a better therapeutic index are urgently needed. Taselisib is a potent, selective, beta-isoform-sparing PI3 kinase inhibitor.

PATIENTS AND METHODS

30 patients with ER-positive, metastatic breast cancer who had failed prior endocrine therapy were treated with escalating doses of taselisib (2 or 4 mg in an intermittent or continuous schedule) combined with tamoxifen 20 mg once daily in this phase 1b study using a "rolling six" design.

RESULTS

Taselisib combined with tamoxifen was generally well tolerated, with treatment-emergent adverse events as expected for this class of drugs, including diarrhea (13 patients, 43%), mucositis (10 patients, 33%), and hyperglycemia (8 patients, 27%). No dose-limiting toxicities were observed. Objective responses were seen in 6 of 25 patients with RECIST-measurable disease (ORR 24%). Median time to disease progression was 3.7 months. Twelve of 30 patients (40%) had disease control for 6 months or more. Circulating tumor (ct)DNA studies using next-generation tagged amplicon sequencing identified early indications of treatment response and mechanistically relevant correlates of clinical drug resistance (e.g., mutations in KRAS, ERBB2) in some patients.

CONCLUSIONS

Taselisib can be safely combined with tamoxifen at the recommended phase 2 dose of 4 mg given once daily on a continuous schedule. Preliminary evidence of antitumor activity was seen in both PIK3CA mutant and wild-type cancers. The randomized phase 2 part of POSEIDON (testing tamoxifen plus taselisib or placebo) is currently recruiting.

Concurrent Radiotherapy and Panitumumab after Lymph Node Dissection and Induction Chemotherapy for Invasive Bladder Cancer

PURPOSE

In this prospective study we evaluated the safety and efficacy of concurrent radiotherapy and panitumumab following neoadjuvant/induction chemotherapy and pelvic lymph node dissection as a bladder preserving therapy for invasive bladder cancer.

MATERIALS AND METHODS

Patients with cT1-4N0-2M0 bladder cancer were treated with pelvic lymph node dissection and 4 cycles of platinum based induction chemotherapy followed by a 6½-week schedule of weekly panitumumab (2.5 mg/kg) and concurrent radiotherapy to the bladder (33 × 2 Gy). As the primary objective we compared concurrent radiotherapy and panitumumab toxicity to a historical control toxicity rate of concurrent cisplatin/radiotherapy (less than 35% of patients with Grade 3-5 toxicity). A sample size of 31 patients was estimated. Secondary end points included complete remission at 3-month followup, the bladder preservation rate, EGFR (epidermal growth factor receptor) expression and RAS mutational status.

RESULTS

Of the 38 cases initially included in this study 34 were staged cN0. After pelvic lymph node dissection 7 cases (21%) were up staged to pN+. Of the 38 patients 31 started concurrent radiotherapy and panitumumab. During concurrent radiotherapy and panitumumab 5 patients (16%, 95% CI 0-31) experienced systemic or local grade 3-4 toxicity. Four patients did not complete treatment due to adverse events. Complete remission was achieved in 29 of 31 patients (94%, 95% CI 83-100). At a median followup of 34 months 4 patients had local recurrence, for which 3 (10%) underwent salvage cystectomy. Two tumors showed EGFR or RAS mutation while 84% showed positive EGFR expression.

CONCLUSIONS

Concurrent radiotherapy and panitumumab following induction chemotherapy and pelvic lymph node dissection has a safety profile that is noninferior to the historical profile of concurrent cisplatin/radiotherapy. The high complete remission and bladder preservation rates are promising and warrant further study.

Abstract 641: Cell free DNA in the supernatant of pleural effusion can detect driver and resistance mutations and can guide TKI treatment decisions

Introduction:

Molecular profiling of tumors has become the mainstay of diagnostics for metastasized solid malignancies and guides personalized treatment, especially in non-small cell lung cancer (NSCLC). In current practice it is often challenging to obtain sufficient tumor material for reliable molecular analysis. Cell free (cf) DNA in blood or other bio-sources could present an alternative approach to obtain genetic information from the tumor. In a retrospective cohort we analyzed the added value of cfDNA analysis in pleural effusions for molecular profiling.

Methods:

We retrospectively analyzed both the supernatant and the cell pellet of 44 pleural effusions sampled from 39 patients with KRAS (23) or EGFR (16) positive tumors for the original driver gene mutation as well as for EGFR T790M resistance mutations. Patients were diagnosed with either NSCLC (32), colon carcinoma (4), appendiceal carcinoma (2) or adenocarcinoma of unknown primary (1). Samples collected in the context of routine clinical care were stored in the NKI-AVL biobank. We used Bio-Rad QX200 droplet digital PCR for analysis.

Results:

The original driver gene mutation could be detected in 37 of the 44 pleural effusions by analysis of both supernatant (35/44 positive) and cell pellet (29/44 positive). In 7 out of 20 pleural effusions from patients with EGFR mutation positive tumors, a T790M mutation was detected. All 7 supernatants were positive as were 5 of the 7 cell pellets. The EGFR T790M mutation was confirmed in all supernatants (4/4) and in 3 of the 4 cell pellets sampled from patients with T790M positive tumors (4).

Conclusions:

Cell free DNA in pleural effusion proved to be a valuable bio-source and can be used to detect driver gene mutations as well as resistance mechanisms like EGFR T790M in pleural effusion.

Citation Format: Karlijn Hummelink, Mirte Muller, Dorothe Linders, Vincent van der Noort, Petra Nederlof, Sjaak Burgers, Gerrit Meijer, Michel van den Heuvel, Daan van den Broek, Kim Monkhorst. Cell free DNA in the supernatant of pleural effusion can detect driver and resistance mutations and can guide TKI treatment decisions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 641.

Comparative Cistromics Reveals Genomic Cross-talk between FOXA1 and ERα in Tamoxifen-Associated Endometrial Carcinomas

Tamoxifen, a small-molecule antagonist of the transcription factor estrogen receptor alpha (ERα) used to treat breast cancer, increases risks of endometrial cancer. However, no parallels of ERα transcriptional action in breast and endometrial tumors have been found that might explain this effect. In this study, we addressed this issue with a genome-wide assessment of ERα-chromatin interactions in surgical specimens obtained from patients with tamoxifen-associated endometrial cancer. ERα was found at active enhancers in endometrial cancer cells as marked by the presence of RNA polymerase II and the histone marker H3K27Ac. These ERα binding sites were highly conserved between breast and endometrial cancer and enriched in binding motifs for the transcription factor FOXA1, which displayed substantial overlap with ERα binding sites proximal to genes involved in classical ERα target genes. Multifactorial ChIP-seq data integration from the endometrial cancer cell line Ishikawa illustrated a functional genomic network involving ERα and FOXA1 together with the enhancer-enriched transcriptional regulators p300, FOXM1, TEAD4, FNFIC, CEBP8, and TCF12. Immunohistochemical analysis of 230 primary endometrial tumor specimens showed that lack of FOXA1 and ERα expression was associated with a longer interval between breast cancer and the emergence of endometrial cancer, exclusively in tamoxifen-treated patients. Our results define conserved sites for a genomic interplay between FOXA1 and ERα in breast cancer and tamoxifen-associated endometrial cancer. In addition, FOXA1 and ERα are associated with the interval time between breast cancer and endometrial cancer only in tamoxifen-treated breast cancer patients. Cancer Res; 76(13); 3773-84. ©2016 AACR.

EGFR and KRAS quality assurance schemes in pathology: generating normative data for molecular predictive marker analysis in targeted therapy

INTRODUCTION

The aim of this study was to compare the reproducibility of epidermal growth factor receptor (EGFR) immunohistochemistry (IHC), EGFR gene amplification analysis, and EGFR and KRAS mutation analysis among different laboratories performing routine diagnostic analyses in pathology in The Netherlands, and to generate normative data.

METHODS

In 2008, IHC, in-situ hybridisation (ISH) for EGFR, and mutation analysis for EGFR and KRAS were tested. Tissue microarray sections were distributed for IHC and ISH, and tissue sections and isolated DNA with known mutations were distributed for mutation analysis. In 2009, ISH and mutation analysis were evaluated. False-negative and false-positive results were defined as different from the consensus, and sensitivity and specificity were estimated.

RESULTS

In 2008, eight laboratories participated in the IHC ring study. In only 4/17 cases (23%) a consensus score of ≥75% was reached, indicating that this analysis was not sufficiently reliable to be applied in clinical practice. For EGFR ISH, and EGFR and KRAS mutation analysis, an interpretable result (success rate) was obtained in ≥97% of the cases, with mean sensitivity ≥96% and specificity ≥95%. For small sample proficiency testing, a norm was established defining outlier laboratories with unsatisfactory performance.

CONCLUSIONS

The result of EGFR IHC is not a suitable criterion for reliably selecting patients for anti-EGFR treatment. In contrast, molecular diagnostic methods for EGFR and KRAS mutation detection and EGFR ISH may be reliably performed with high accuracy, allowing treatment decisions for lung cancer.

Abstract 4113: Kinase activity based biomarkers: Identification of prognostic and erlotinib response prediction markers in NSCLC patients

Background: Reliable diagnostic tests are needed to identify early stage non-small cell lung carcinoma (NSCLC) patients with poor prognosis. Concomitantly there is a clear need for tests that enable the selection of patients who will benefit from targeted therapy with kinase inhibitors. We evaluated kinase activity profiles in two groups of early stage NSCLC patients, either for prognosis of long- or short-term survival, or for predicting erlotinib drug response.

Method: Retrospective studies were performed on fresh frozen resection material of two groups of early stage NSCLC patients. The first group consisted of 48 short- and long-term survivors who underwent a complete surgical resection (5+ years follow-up). The second group consisted of 14 NSCLC patients who received 3 weeks of neo-adjuvant treatment with erlotinib prior to complete surgical resection. Response evaluation to neo-adjuvant treatment was based on histopathological examination of the surgical specimens. For both studies, kinase activity profiles of lysed cryosections of tumour tissues were generated in the presence and absence of protein tyrosine kinase inhibitors on PamChip® peptide micro-arrays, comprising 144 tyrosine containing peptides, derived from known phosphorylation sites of human proteins. Partial least square discriminant analysis was used to construct prediction models. ClustalW alignment algorithms were used to investigate the most informative phosphorylation sites.

Results: Kinase activity profiles obtained in the absence of inhibitor did not distinguish between subgroups (long- versus short-term survival, responder or non-responder to TKI), whereas ratios of inhibited versus non-inhibited signals resulted in distinct classifiers predicting survival for the first group, and response for the second group. Multivariate unsupervised analysis with leave-one-out cross-validation resulted in an error rate for survival prediction of 29%. In the drug response prediction 13 out of 14 patients were correctly classified.

Conclusion: This is the first study to show that kinase activity profiles of tumour tissue exposed to a kinase inhibitor can be used to identify NSCLC patients likely to respond to erlotinib treatment. Furthermore, based on kinase activity profiles of early stage NSCLC tumours, a prognostic classifier, for a set of 48 patients, was obtained.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4113. doi:10.1158/1538-7445.AM2011-4113

Multifocal myxoid liposarcoma--metastasis or second primary tumor?: a molecular biological analysis

The classification of multifocal myxoid/round cell liposarcoma, which is defined as tumor presentation in at least two separate sites before manifestation in the lungs, as either metastasis or as a second primary tumor, has essential clinical consequences. Genetically, myxoid/round cell liposarcoma is characterized by t(12;16)(q13;p11) or t(12;22)(q13;q12), and various exon fusion transcripts are described with varying incidences, which permits their use as markers for clonality. Moreover, in solid tumors, analysis of loss of heterozygozity is valuable for clonality analysis. Therefore, fifteen multifocal myxoid/round cell liposarcoma patients with two to five metachronous (n = 12) or synchronous (n = 3) localizations were investigated. Using RT-PCR, the detailed molecular characteristics of the FUS-CHOP and EWS-CHOP breakpoints were determined. Loss of heterozygozity analysis at twelve loci was then used to further analyze clonal relationships. In all patients, tumor sites showed identical FUS-CHOP fusion products. In six patients, identical rare fusion transcripts were found, supporting a clonal relationship. Nine patients had the common exon5-FUS/exon2-CHOP fusion transcript, and two of these were identified as clonally related by loss of heterozygozity analysis. In all other patients, loss of heterozygozity analysis was highly suggestive of a clonal relationship, and no evidence for interpretation of a second primary tumor was found. This study supports the metastatic nature of apparent multifocal myxoid/round cell liposarcoma.

BRCA1-deficient mammary tumor cells are dependent on EZH2 expression and sensitive to Polycomb Repressive Complex 2-inhibitor 3-deazaneplanocin A

Introduction

Treatment of breast cancer is becoming more individualized with the recognition of tumor subgroups that respond differently to available therapies. Breast cancer 1 gene (BRCA1)-deficient tumors are usually of the basal subtype and associated with poor survival rates, highlighting the need for more effective therapy.

Methods

We investigated a mouse model that closely mimics breast cancer arising in BRCA1-mutation carriers to better understand the molecular mechanism of tumor progression and tested whether targeting of the Polycomb-group protein EZH2 would be a putative therapy for BRCA1-deficient tumors.

Results

Gene expression analysis demonstrated that EZH2 is overexpressed in BRCA1-deficient mouse mammary tumors. By immunohistochemistry we show that an increase in EZH2 protein levels is also evident in tumors from BRCA1-mutation carriers. EZH2 is responsible for repression of genes driving differentiation and could thus be involved in the undifferentiated phenotype of these tumors. Importantly, we show that BRCA1-deficient cancer cells are selectively dependent on their elevated EZH2 levels. In addition, a chemical inhibitor of EZH2, 3-deazaneplanocin A (DZNep), is about 20-fold more effective in killing BRCA1-deficient cells compared to BRCA1-proficient mammary tumor cells.

Conclusions

We demonstrate by specific knock-down experiments that EZH2 overexpression is functionally relevant in BRCA1-deficient breast cancer cells. The effectiveness of a small molecule inhibitor indicates that EZH2 is a druggable target. The overexpression of EZH2 in all basal-like breast cancers warrants further investigation of the potential for targeting the genetic make-up of this particular breast cancer type.

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.

[Table: see text]

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.