Secondary Somatic Mutations Restoring BRCA1/2 Predict Chemotherapy Resistance in Hereditary Ovarian Carcinomas

University of Washington Medical Center, Department of Obstetrics and Gynecology, Box 356460, Seattle, WA, USA.
Journal of Clinical Oncology (Impact Factor: 18.43). 06/2011; 29(22):3008-15. DOI: 10.1200/JCO.2010.34.2980
Source: PubMed


Secondary somatic BRCA1/2 mutations may restore BRCA1/2 protein in hereditary ovarian carcinomas. In cell lines, BRCA2 restoration mediates resistance to platinum chemotherapy and poly (ADP-ribose) polymerase (PARP) inhibitors. We assessed primary and recurrent BRCA1/2-mutated ovarian carcinomas to define the frequency of secondary mutations and correlate these changes with clinical outcomes.
Neoplastic cells were isolated with laser capture microdissection, and DNA was sequenced at the site of the known germline BRCA1/2 mutation. When secondary mutations were found that restored wild-type sequence, haplotyping was performed using single nucleotide polymorphisms in tumor and paired lymphocyte DNA to rule out retention of the wild-type allele.
There were 64 primary and 46 recurrent ovarian carcinomas assessed. Thirteen (28.3%) of 46 (95% CI, 17.3% to 42.6%) recurrent carcinomas had a secondary mutation compared with two (3.1%) of 64 (95% CI, 1.0% to 10.7%) primary carcinomas (P = .0003, Fisher's exact test). Twelve (46.2%) of 26 (95% CI, 28.7% to 64.7%) platinum-resistant recurrences had secondary mutations restoring BRCA1/2, compared with one (5.3%) of 19 (95% CI, 1.2% to 24.8%) platinum-sensitive recurrences (P = .003, Fisher's exact test). Six (66.7%) of nine (95% CI, 34.8% to 87.8%) women with prior breast carcinoma had a recurrent carcinoma with a secondary mutation, compared with six (17.1%) of 35 (95% CI, 8.2% to 32.8%) with no history of breast carcinoma (P = .007, Fisher's exact test).
Secondary somatic mutations that restore BRCA1/2 in carcinomas from women with germline BRCA1/2 mutations predict resistance to platinum chemotherapy and may also predict resistance to PARP inhibitors. These mutations were detectable only in ovarian carcinomas of women whom have had previous chemotherapy, either for ovarian or breast carcinoma.

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    • "Previous selection for cisplatin-resistant clones revealed BRCA2 reversion mutations that restore HR, as in the C4-2 clone (Fig. 1A–C), as well as clones that were resistant by an unknown mechanism (Sakai et al. 2009). Thus, the screen was performed in PEO1 cells because they reflect BRCA2 mutant ovarian cancers that develop both reversion and reversion-independent mechanisms of cisplatin resistance (Norquist et al. 2011). Cells were infected with viral pools containing the pGIPZ library comprised of ;81,000 shRNAs directed against 28,000 unique targets or a nonsilencing control (NSC), selected with puromycin, cisplatin-treated, and analyzed for colony formation (see the Materials and Methods) (Fig. 1D). "
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    ABSTRACT: Hereditary cancers derive from gene defects that often compromise DNA repair. Thus, BRCA-associated cancers are sensitive to DNA-damaging agents such as cisplatin. The efficacy of cisplatin is limited, however, by the development of resistance. One cisplatin resistance mechanism is restoration of homologous recombination (HR), which can result from BRCA reversion mutations. However, in BRCA2 mutant cancers, cisplatin resistance can occur independently of restored HR by a mechanism that remains unknown. Here we performed a genome-wide shRNA screen and found that loss of the nucleosome remodeling factor CHD4 confers cisplatin resistance. Restoration of cisplatin resistance is independent of HR but correlates with restored cell cycle progression, reduced chromosomal aberrations, and enhanced DNA damage tolerance. Suggesting clinical relevance, cisplatin-resistant clones lacking genetic reversion of BRCA2 show de novo loss of CHD4 expression in vitro. Moreover, BRCA2 mutant ovarian cancers with reduced CHD4 expression significantly correlate with shorter progression-free survival and shorter overall survival. Collectively, our findings indicate that CHD4 modulates therapeutic response in BRCA2 mutant cancer cells. © 2015 Guillemette et al.; Published by Cold Spring Harbor Laboratory Press.
    Genes & Development 03/2015; 29(5):489-94. DOI:10.1101/gad.256214.114 · 10.80 Impact Factor
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    • "Of note, a common mechanism of resistance to both platinum and PARP inhibitors is restoration of defective HR. For example, in BRCA-mutated tumors, secondary BRCA1/2 mutations that restore BRCA1/2 function have been described [23] [24] and may lead to development of both platinum and PARP inhibitor resistance. Although a discussion of mechanisms of PARP inhibitor resistance is beyond the scope of this review and is discussed elsewhere [24], responsiveness to platinum post-PARP inhibitor failure has been demonstrated suggesting that the mechanisms of resistance to platinum and PARP inhibitors are not completely overlapping [25]. "
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    ABSTRACT: Clinical investigation of poly(ADP-ribose) polymerase (PARP) inhibitors for ovarian cancer treatment has rapidly evolved from observations of single-agent in vitro activity of these agents in BRCA-deficient cancer cells in 2005 to the initiation of multiple phase III studies in 2013. With clinical trial design and treatment of ovarian cancer increasingly based on histological and molecular characteristics, PARP inhibitors are on the horizon of becoming the first biologic agents to be used to treat ovarian cancer based upon pre-selection characteristics of the patient’s cancer. PARP inhibitors are most active in ovarian cancers that have defects or aberrations in DNA repair; use of these agents has been of particular interest in high grade serous cancers (HGSC), where studies have shown that ~ 50% of HGSC have abnormalities of DNA repair through BRCA germline and somatic mutation, post-translational changes of BRCA, and abnormalities of other DNA repair molecules. In addition, as aberrant DNA pathways in other histological subtypes of ovarian cancer are identified, and through the combination of PARP inhibitors with other biologic agents, the pool of eligible patients who may benefit from PARP inhibitors will likely expand. Pending review by the Food and Drug Administration (FDA) and the outcome of confirmatory phase III studies, PARP inhibitors could become the first FDA-approved biologic agent for ovarian cancer and also the first new FDA-approval in ovarian cancer since carboplatin and gemcitabine were approved for platinum sensitive ovarian cancer in 2006. This review discusses the PARP inhibitors that are currently in testing for ovarian cancer treatment and the future of this class of anti-cancer agents.
    Gynecologic Oncology 05/2014; 133(2). DOI:10.1016/j.ygyno.2014.02.039 · 3.77 Impact Factor
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    • "PARP inhibitor therapy has shown promise in BRCA mutation carriers [56] [57]. However, with the development of platinum-resistant disease, nearly 50% of patient tumors demonstrate gene reversions [4]. Use of VEGFR3 inhibitors in combination with Figure 4. VEGFR3 inhibition with Maz51 chemosensitizes in vitro in a BRCA-dependent manner. "
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    ABSTRACT: In ovarian cancer, loss of BRCA gene expression in tumors is associated with improved response to chemotherapy and increased survival. A means to pharmacologically downregulate BRCA gene expression could improve the outcomes of patients with BRCA wild-type tumors. We report that vascular endothelial growth factor receptor 3 (VEGFR3) inhibition in ovarian cancer cells is associated with decreased levels of both BRCA1 and BRCA2. Inhibition of VEGFR3 in ovarian tumor cells was associated with growth arrest. CD133(+) ovarian cancer stemlike cells were preferentially susceptible to VEGFR3-mediated growth inhibition. VEGFR3 inhibition-mediated down-regulation of BRCA gene expression reversed chemotherapy resistance and restored chemosensitivity in resistant cell lines in which a BRCA2 mutation had reverted to wild type. Finally, we demonstrate that tumor-associated macrophages are a primary source of VEGF-C in the tumor microenvironment. Our studies suggest that VEGFR3 inhibition may be a pharmacologic means to downregulate BRCA genes and improve the outcomes of patients with BRCA wild-type tumors.
    Neoplasia (New York, N.Y.) 04/2014; 16(4):343-353.e2. DOI:10.1016/j.neo.2014.04.003 · 4.25 Impact Factor
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