Beth Y. Karlan

Secondary mutations as a mechanism of cisplatin resistance in BRCA2 -mutated cancers

Ovarian carcinomas with mutations in the tumour suppressor BRCA2 are particularly sensitive to platinum compounds. However, such carcinomas ultimately develop cisplatin resistance. The mechanism of that resistance is largely unknown. Here we show that acquired resistance to cisplatin can be mediated by secondary intragenic mutations in BRCA2 that restore the wild-type BRCA2 reading frame. First, in a cisplatin-resistant BRCA2-mutated breast-cancer cell line, HCC1428, a secondary genetic change in BRCA2 rescued BRCA2 function. Second, cisplatin selection of a BRCA2-mutated pancreatic cancer cell line, Capan-1 (refs 3, 4), led to five different secondary mutations that restored the wild-type BRCA2 reading frame. All clones with secondary mutations were resistant both to cisplatin and to a poly(ADP-ribose) polymerase (PARP) inhibitor (AG14361). Finally, we evaluated recurrent cancers from patients whose primary BRCA2-mutated ovarian carcinomas were treated with cisplatin. The recurrent tumour that acquired cisplatin resistance had undergone reversion of its BRCA2 mutation. Our results suggest that secondary mutations that restore the wild-type BRCA2 reading frame may be a major clinical mediator of acquired resistance to platinum-based chemotherapy.

Localization of human BRCA1 and its loss in high-grade, non-inherited breast carcinomas

Although the link between the BRCA1 tumour–suppressor gene and hereditary breast and ovarian cancer is established, the role, if any, of BRCA1 in non–familial cancers is unclear. BRCA1 mutations are rare in sporadic cancers, but loss of BRCA1 resulting from reduced expression or incorrect subcellular localization is postulated to be important in non–familial breast and ovarian cancers. Epigenetic loss, however, has not received general acceptance due to controversy regarding the subcellular localization of BRCA1 proteins, reports of which have ranged from exclusively nuclear, to conditionally nuclear, to the ER/golgi, to cytoplasmic invaginations into the nucleus. In an attempt to resolve this issue, we have comprehensively characterized 19 anti–BRCA1 antibodies. These reagents detect a 220–kD protein localized in discrete nuclear foci in all epithelial cell lines, including those derived from breast malignancies. Immunohistochemical staining of human breast specimens also revealed BRCA1 nuclear foci in benign breast, invasive lobular cancers and low–grade ductal carcinomas. Conversely, BRCA1 expression was reduced or undetectable in the majority of high–grade, ductal carcinomas, suggesting that absence of BRCA1 may contribute to the pathogenesis of a significant percentage of sporadic breast cancers.

Comparative hybridization of an array of 21 500 ovarian cDNAs for the discovery of genes overexpressed in ovarian carcinomas

Comparative hybridization of cDNA arrays is a powerful tool for the measurement of differences in gene expression between two or more tissues. We optimized this technique and employed it to discover genes with potential for the diagnosis of ovarian cancer. This cancer is rarely identified in time for a good prognosis after diagnosis. An array of 21,500 unknown ovarian cDNAs was hybridized with labeled first-strand cDNA from 10 ovarian tumors and six normal tissues. One hundred and thirty-four clones are overexpressed in at least five of the 10 tumors. These cDNAs were sequenced and compared to public sequence databases. One of these, the gene HE4, was found to be expressed primarily in some ovarian cancers, and is thus a potential marker of ovarian carcinoma.

Phase I Clinical Study of Pertuzumab, a Novel HER Dimerization Inhibitor, in Patients With Advanced Cancer

PURPOSE Pertuzumab, a recombinant humanized monoclonal antibody (2C4), binds to extracellular domain II of the HER-2 receptor and blocks its ability to dimerize with other HER receptors. Pertuzumab represents a new class of targeted therapeutics known as HER dimerization inhibitors. A clinical study was conducted to investigate safety and pharmacokinetics of pertuzumab and to perform a preliminary assessment of HER dimerization inhibition as a treatment strategy. PATIENTS AND METHODS Patients with incurable, locally advanced, recurrent or metastatic solid tumors that had progressed during or after standard therapy were recruited to a dose-escalation study of pertuzumab (0.5 to 15 mg/kg) given intravenously every 3 weeks. RESULTS Twenty-one patients received pertuzumab and 19 completed at least two cycles. Pertuzumab was well tolerated. Overall, 365 adverse events were reported and 122 considered to be possibly drug related. Of these, 116 were of grade 1 to 2 intensity. The pharmacokinetics of pertuzumab were similar to other humanized immunoglobulin G antibodies, supporting a 3-week dosing regimen. Trough plasma concentrations were in excess of target concentrations at doses greater than 5 mg/kg. Two patients, one with ovarian cancer (5.0 mg/kg) and one with pancreatic islet cell carcinoma (15.0 mg/kg), achieved a partial response. Responses were documented by Response Evaluation Criteria in Solid Tumors after 1.5 and 6 months of pertuzumab therapy, and lasted for 11 and 10 months, respectively. Stable disease lasting for more than 2.5 months (range, 2.6 to 5.5 months) was observed in six patients. CONCLUSION These results demonstrate that pertuzumab is well tolerated, has a pharmacokinetic profile which supports 3-week dosing, and is clinically active, suggesting that inhibition of dimerization may be an effective anticancer strategy.

Secondary BRCA1 Mutations in BRCA1-Mutated Ovarian Carcinomas with Platinum Resistance

Although ovarian carcinomas with mutated BRCA1 or BRCA2 are sensitive to platinum compounds, such carcinomas eventually develop platinum resistance. Previously, we showed that acquired resistance to cisplatin in BRCA2-mutated tumors can be mediated by secondary intragenic mutations in BRCA2 that restore the wild-type BRCA2 reading frame. Here, we show that secondary mutations of BRCA1 also occur in BRCA1-mutated ovarian cancer with platinum resistance. We evaluated nine recurrent BRCA1-mutated ovarian cancers previously treated with platinum compounds, including five with acquired platinum resistance, one with primary platinum resistance, and three with platinum sensitivity. Four of the six recurrent platinum-resistant tumors had developed secondary genetic changes in BRCA1 that restored the reading frame of the BRCA1 protein, whereas none of the three platinum-sensitive recurrent tumors developed BRCA1 sequence alterations. We immunohistochemically confirmed restored expression of BRCA1 protein in two cases with secondary mutations. Intriguingly, the case with primary platinum resistance showed back mutation of BRCA1 in the primary tumor and showed another secondary mutation in the recurrent tumor. Our results suggest that secondary mutations in BRCA1 can mediate resistance to platinum in BRCA1-mutated ovarian tumors.

Cancer Risks for Male Carriers of Germline Mutations in BRCA1 or BRCA2: A Review of the Literature

Major risks conferred by BRCA1 and BRCA2 in women are for cancers of the breast, ovary, fallopian tube, and peritoneum. Male carriers of mutations in BRCA1 or BRCA2 are also susceptible to cancer; however, their risks remain poorly understood and their optimal clinical management has not yet been defined. This article reviews studies that estimate risk associated with mutations in BRCA1 or BRCA2, with a focus on the cancer sites most relevant to men. Male BRCA1 mutation carriers are at increased risk of cancers of the prostate and breast. Evidence supporting increased susceptibility to colon cancer is limited. In contrast to women, who have a greater lifetime risk of cancer with mutations of the BRCA1 gene, BRCA2 is the more important gene for men. The spectrum of cancers is wide for BRCA2 and some studies report that the overall cancer risk for male BRCA2 carriers exceeds the risk for female carriers. In particular, the relative risk to male BRCA2 mutation carriers is high before age 65 years, largely attributable to breast, prostate, and pancreatic cancers. BRCA2 mutation carriers are also at risk of stomach cancer and melanoma (of the skin and eye). Additional research into risks to male BRCA1 or BRCA2 mutation carriers is necessary, specifically to determine the magnitude of excess cancer risk among BRCA2 carriers and to increase our understanding of the basis for the observed site-specificity in cancer development.

Phase II, Open-Label, Randomized, Multicenter Study Comparing the Efficacy and Safety of Olaparib, a Poly (ADP-Ribose) Polymerase Inhibitor, and Pegylated Liposomal Doxorubicin in Patients With BRCA1 or BRCA2 Mutations and Recurrent Ovarian Cancer

PURPOSE Olaparib (AZD2281), an orally active poly (ADP-ribose) polymerase inhibitor that induces synthetic lethality in BRCA1- or BRCA2-deficient cells, has shown promising clinical efficacy in nonrandomized phase II trials in patients with ovarian cancer with BRCA1 or BRCA2 deficiency. We assessed the comparative efficacy and safety of olaparib and pegylated liposomal doxorubicin (PLD) in this patient population. PATIENTS AND METHODS In this multicenter, open-label, randomized, phase II study, patients with ovarian cancer that recurred within 12 months of prior platinum therapy and with confirmed germline BRCA1 or BRCA2 mutations were enrolled. Patients were assigned in a 1:1:1 ratio to olaparib 200 mg twice per day or 400 mg twice per day continuously or PLD 50 mg/m(2) intravenously every 28 days. The primary efficacy end point was Response Evaluation Criteria in Solid Tumors (RECIST) -assessed progression-free survival (PFS). Secondary end points included objective response rate (ORR) and safety. RESULTS Ninety-seven patients were randomly assigned. Median PFS was 6.5 months (95% CI, 5.5 to 10.1 months), 8.8 months (95% CI, 5.4 to 9.2 months), and 7.1 months (95% CI, 3.7 to 10.7 months) for the olaparib 200 mg, olaparib 400 mg, and PLD groups, respectively. There was no statistically significant difference in PFS (hazard ratio, 0.88; 95% CI, 0.51 to 1.56; P = .66) for combined olaparib doses versus PLD. RECIST-assessed ORRs were 25%, 31%, and 18% for olaparib 200 mg, olaparib 400 mg, and PLD, respectively; differences were not statistically significant. Tolerability of both treatments was as expected based on previous trials. CONCLUSION The efficacy of olaparib was consistent with previous studies. However, the efficacy of PLD was greater than expected. Olaparib 400 mg twice per day is a suitable dose to explore in further studies in this patient population.

Gene Expression Profile of BRCAness That Correlates With Responsiveness to Chemotherapy and With Outcome in Patients With Epithelial Ovarian Cancer

PURPOSE To define a gene expression profile of BRCAness that correlates with chemotherapy response and outcome in epithelial ovarian cancer (EOC). METHODS A publicly available microarray data set including 61 patients with EOC with either sporadic disease or BRCA(1/2) germline mutations was used for development of the BRCAness profile. Correlation with platinum responsiveness was assessed in platinum-sensitive and platinum-resistant tumor biopsy specimens from six patients with BRCA germline mutations. Association with poly-ADP ribose polymerase (PARP) inhibitor responsiveness and with radiation-induced RAD51 foci formation (a surrogate of homologous recombination) was assessed in Capan-1 cell line clones. The BRCAness profile was validated in 70 patients enriched for sporadic disease to assess its association with outcome. RESULTS The BRCAness profile accurately predicted platinum responsiveness in eight out of 10 patient-derived tumor specimens, and between PARP-inhibitor sensitivity and resistance in four out of four Capan-1 clones. [corrected] When applied to the 70 patients with sporadic disease, patients with the BRCA-like (BL) profile had improved disease-free survival (34 months v 15 months; log-rank P = .013) and overall survival (72 months v 41 months; log-rank P = .006) compared with patients with a non-BRCA-like (NBL) profile, respectively. The BRCAness profile maintained independent prognostic value in multivariate analysis, which controlled for other known clinical prognostic factors. CONCLUSION The BRCAness profile correlates with responsiveness to platinum and PARP inhibitors and identifies a subset of sporadic patients with improved outcome. Additional evaluation of this profile as a predictive tool in patients with sporadic EOC is warranted.

Association between BRCA1 and BRCA2 mutations and survival in women with invasive epithelial ovarian cancer

CONTEXT Approximately 10% of women with invasive epithelial ovarian cancer (EOC) carry deleterious germline mutations in BRCA1 or BRCA2. A recent article suggested that BRCA2-related EOC was associated with an improved prognosis, but the effect of BRCA1 remains unclear. OBJECTIVE To characterize the survival of BRCA carriers with EOC compared with noncarriers and to determine whether BRCA1 and BRCA2 carriers show similar survival patterns. DESIGN, SETTING, AND PARTICIPANTS A pooled analysis of 26 observational studies on the survival of women with ovarian cancer, which included data from 1213 EOC cases with pathogenic germline mutations in BRCA1 (n = 909) or BRCA2 (n = 304) and from 2666 noncarriers recruited and followed up at variable times between 1987 and 2010 (the median year of diagnosis was 1998). MAIN OUTCOME MEASURE Five-year overall mortality. RESULTS The 5-year overall survival was 36% (95% CI, 34%-38%) for noncarriers, 44% (95% CI, 40%-48%) for BRCA1 carriers, and 52% (95% CI, 46%-58%) for BRCA2 carriers. After adjusting for study and year of diagnosis, BRCA1 and BRCA2 mutation carriers showed a more favorable survival than noncarriers (for BRCA1: hazard ratio [HR], 0.78; 95% CI, 0.68-0.89; P < .001; and for BRCA2: HR, 0.61; 95% CI, 0.50-0.76; P < .001). These survival differences remained after additional adjustment for stage, grade, histology, and age at diagnosis (for BRCA1: HR, 0.73; 95% CI, 0.64-0.84; P < .001; and for BRCA2: HR, 0.49; 95% CI, 0.39-0.61; P < .001). The BRCA1 HR estimate was significantly different from the HR estimated in the adjusted model (P for heterogeneity = .003). CONCLUSION Among patients with invasive EOC, having a germline mutation in BRCA1 or BRCA2 was associated with improved 5-year overall survival. BRCA2 carriers had the best prognosis.

BRCA1 and BRCA2 Mutation Analysis of 208 Ashkenazi Jewish Women with Ovarian Cancer

Ovarian cancer is a component of the autosomal-dominant hereditary breast-ovarian cancer syndrome and may be due to a mutation in either the BRCA1 or BRCA2 genes. Two mutations in BRCA1 (185delAG and 5382insC) and one mutation in BRCA2 (6174delT) are common in the Ashkenazi Jewish population. One of these three mutations is present in approximately 2% of the Jewish population. Each mutation is associated with an increased risk of ovarian cancer, and it is expected that a significant proportion of Jewish women with ovarian cancer will carry one of these mutations. To estimate the proportion of ovarian cancers attributable to founding mutations in BRCA1 and BRCA2 in the Jewish population and the familial cancer risks associated with each, we interviewed 213 Jewish women with ovarian cancer at 11 medical centers in North America and Israel and offered these women genetic testing for the three founder mutations. To establish the presence of nonfounder mutations in this population, we also completed the protein-truncation test on exon 11 of BRCA1 and exons 10 and 11 of BRCA2. We obtained a detailed family history on all women we studied who had cancer and on a control population of 386 Ashkenazi Jewish women without ovarian or breast cancer. A founder mutation was present in 41.3% of the women we studied. The cumulative incidence of ovarian cancer to age 75 years was found to be 6.3% for female first-degree relatives of the patients with ovarian cancer, compared with 2.0% for the female relatives of healthy controls (relative risk 3.2; 95% CI 1.5-6.8; P=.002). The relative risk to age 75 years for breast cancer among the female first-degree relatives was 2.0 (95% CI 1.4-3.0; P=.0001). Only one nonfounder mutation was identified (in this instance, in a woman of mixed ancestry), and the three founding mutations accounted for most of the observed excess risk of ovarian and breast cancer in relatives.