Cytoreductive surgery followed by chemotherapy and olaparib maintenance in BRCA 1/2 mutated recurrent ovarian cancer: a retrospective MITO group study.

INTRODUCTION: The role of cytoreductive surgery in the poly-ADP ribose polymerase inhibitors era is not fully investigated. We evaluated the impact of surgery performed prior to platinum-based chemotherapy followed by olaparib maintenance in platinum-sensitive BRCA-mutated recurrent ovarian cancer. METHODS: This retrospective study included platinum-sensitive recurrent ovarian cancer BRCA-mutated patients from 13 Multicenter Italian Trials in Ovarian cancer and gynecological malignancies centers treated between September 2015 and May 2019. The primary outcomes were progression-free survival and overall survival. Data on post-progression treatment was also assessed. RESULTS: Among 209 patients, 72 patients (34.5%) underwent cytoreductive surgery followed by platinum-based chemotherapy and olaparib maintenance, while 137 patients (65.5%) underwent chemotherapy treatment alone. After a median follow-up of 37.3 months (95% CI: 33.4 to 40.8), median progression-free survival in the surgery group was not reached, compared with 11 months in patients receiving chemotherapy alone (P<0.001). Median overall survival was nearly double in patients undergoing surgery before chemotherapy (55 vs 28 months, P<0.001). Post-progression therapy was assessed in 127 patients: response rate to chemotherapy was 29.2%, 8.8%, and 9.0% in patients with platinum-free interval >12 months, between 6 and 12 months, and <6 months, respectively. CONCLUSION: Cytoreductive surgery performed before platinum therapy and olaparib maintenance was associated with longer progression-free survival and overall survival in BRCA-mutated platinum-sensitive relapsed ovarian cancer patients. In accordance with our preliminary results, the response rate to chemotherapy given after progression during olaparib was associated with platinum-free interval.

Pancreatic cancer.

Pancreatic cancer is a highly fatal disease with a 5-year survival rate of approximately 10% in the USA, and it is becoming an increasingly common cause of cancer mortality. Risk factors for developing pancreatic cancer include family history, obesity, type 2 diabetes, and tobacco use. Patients typically present with advanced disease due to lack of or vague symptoms when the cancer is still localised. High quality computed tomography with intravenous contrast using a dual phase pancreatic protocol is typically the best method to detect a pancreatic tumour and to determine surgical resectability. Endoscopic ultrasound is an increasingly used complementary staging modality which also allows for diagnostic confirmation when combined with fine needle aspiration. Patients with pancreatic cancer are often divided into one of four categories based on extent of disease: resectable, borderline resectable, locally advanced, and metastatic; patient condition is also an important consideration. Surgical resection represents the only chance for cure, and advancements in adjuvant chemotherapy have improved long-term outcomes in these patients. Systemic chemotherapy combinations including FOLFIRINOX (5-fluorouracil, folinic acid [leucovorin], irinotecan, and oxaliplatin) and gemcitabine plus nab-paclitaxel remain the mainstay of treatment for patients with advanced disease. Data on the benefit of PARP inhibition as maintenance therapy in patients with germline BRCA1 or BRACA2 mutations might prove to be a harbinger of advancement in targeted therapy. Additional research efforts are focusing on modulating the pancreatic tumour microenvironment to enhance the efficacy of the immunotherapeutic strategies.

A critical evaluation of methods to interpret drug combinations.

Combination therapy is increasingly central to modern medicine. Yet reliable analysis of combination studies remains an open challenge. Previous work suggests that common methods of combination analysis are too susceptible to noise to support robust scientific conclusions. In this paper, we use simulated and real-world combination datasets to demonstrate that traditional index methods are unstable and biased by pharmacological and experimental conditions, whereas response-surface approaches such as the BRAID method are more consistent and unbiased. Using a publicly-available data set, we show that BRAID more accurately captures variations in compound mechanism of action, and is therefore better able to discriminate between synergistic, antagonistic, and additive interactions. Finally, we applied BRAID analysis to identify a clear pattern of consistently enhanced AKT sensitivity in a subset of cancer cell lines, and a far richer array of PARP inhibitor combination therapies for BRCA1-deficient cancers than would be identified by traditional synergy analysis.

Mechanisms of PARP inhibitor resistance in ovarian cancer.

PURPOSE OF REVIEW: To summarize recently discovered PARP inhibitor resistance mechanisms and highlight the clinical relevance of these findings to date. RECENT FINDINGS: A predominant mechanism of acquired PARP inhibitor resistance in homologous recombination-deficient cancers is the acquisition of homologous recombination proficiency as a consequence of secondary genetic or epigenetic events, such as secondary mutations in BRCA1 or BRCA2, or reversal of BRCA1 promoter methylation that restores homologous recombination and leads to PARP inhibitor resistance. Multiple other potential mechanisms of acquired resistance to PARP inhibitors including loss of DNA end resection inhibition (53BP1/REV7/RIF1/Sheldin) or DNA replication fork protection (PTIP/EZH2), but also increased drug efflux or induction of a reversible senescent or mesenchymal cell state have been described in ovarian cancer models. However, only few of these mechanisms have been identified in clinical samples. SUMMARY: Multiple adaptive responses following PARP inhibitor treatment have been identified. Further research is needed to better understand what role these mechanisms play for clinical PARP inhibitor resistance and how these mechanisms may render ovarian cancer cells susceptible to subsequent novel combination therapies.

Targeting DNA repair in breast cancer.

Targeting of DNA repair is an important therapeutic approach in breast cancer, particularly for BRCA1/2 associated breast cancers and those characterized by a "BRCAness" phenotype including those with "triple negative" subtype. Various assays and scores have been developed to evaluate degree of homologous recombination deficiency in the hope that this would aid in predicting for susceptibility to DNA repair targeting agents, and yet, presence of a germline mutation in BRCA1/2 remains the strongest predictor for therapeutic efficacy of such agents. Pre-clinical studies suggested increased sensitivity to agents that damage DNA in a way that interferes with DNA replication forks and which subsequently require DNA repair by homologous recombination, such as platinum salts, and this data was further confirmed clinically. Recently published phase III data favor the use of PARP inhibitors amongst patients with BRCA1/2 associated advanced breast cancer. Novel chemotherapeutic agents targeting DNA damage repair are under evaluation as well as further combinations of PARP inhibitors with immuno-therapeutics and other biological agents.

Poly-ADP-ribosyl-polymerase inhibitor resistance mechanisms and their therapeutic implications.

PURPOSE OF REVIEW: Poly-ADP-ribosyl-polymerase (PARP) inhibitors are an increasingly-utilized therapy in women with high-grade serous ovarian carcinoma, but tumor resistance to PARP inhibitor monotherapy is inevitable. RECENT FINDINGS: PARP inhibitors have been most studied in patients with breast and ovarian cancers associated with deleterious germline BRCA1 or BRCA2 mutations, though their role has expanded to include use as maintenance therapy in women with platinum-sensitive high-grade serous ovarian cancer due to the high propensity of such cancers to have defects in DNA repair by homologous recombination. As mechanisms of PARP inhibitor resistance are elucidated, rationale combination strategies can be devised to extend therapeutic benefits and to abrogate resistance. SUMMARY: Mechanisms of resistance include restoration of homologous recombination repair proficiency, loss of cancer cell reliance on PARP, and increased intracellular signaling through cell growth pathways.

Prexasertib, a cell cycle checkpoint kinase 1 and 2 inhibitor, in BRCA wild-type recurrent high-grade serous ovarian cancer: a first-in-class proof-of-concept phase 2 study.

BACKGROUND: High-grade serous ovarian carcinoma is characterised by TP53 mutations, DNA repair defects, and genomic instability. We hypothesised that prexasertib (LY2606368), a cell cycle checkpoint kinase 1 and 2 inhibitor, would be active in BRCA wild-type disease. METHODS: In an open-label, single-centre, two-stage, proof-of-concept phase 2 study, we enrolled women aged 18 years or older with measurable, recurrent high-grade serous or high-grade endometrioid ovarian carcinoma. All patients had a negative family history of hereditary breast and ovarian cancer or known BRCA wild-type status, measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, Eastern Cooperative Oncology Group performance status score 0-2, and adequate haematological, renal, hepatic, and bone-marrow function. Patients received intravenous prexasertib 105 mg/m2 administered over 1 h every 14 days in 28-day cycles until disease progression, unacceptable toxicity, or withdrawal of consent. The primary endpoint of investigator-assessed tumour response, based on RECIST version 1.1, was assessed per protocol (assessable patients who had undergone CT imaging at baseline and attended at least one protocol-specified follow-up) and by intention to treat. The final analysis of this cohort of patients with BRCA wild-type high-grade serous ovarian carcinoma is reported here. This ongoing trial is registered with ClinicalTrials.gov, number NCT02203513, and continues to enrol patients for the BRCA-mutated ovarian cancer cohort. FINDINGS: Between Jan 20, 2015, and Nov 2, 2016, we enrolled 28 women with a median age of 64 years (IQR 58·0-69·5) who had previously received a median of 5·0 (IQR 2·5-5·0) systemic therapies. Most patients (22 [79%]) had platinum-resistant or platinum-refractory disease. All women received at least one dose of prexasertib, but four (14%) of 28 patients were not assessable for RECIST response. Eight (33%, 95% CI 16-55) of 24 patients assessable per protocol had partial responses. In the intention-to-treat population, eight (29%, 95% CI 13-49) of 28 had a partial responses. The most common (in >10% patients) grade 3 or 4 treatment-emergent adverse events were neutropenia in 26 (93%) of 28 patients, reduced white blood cell count in 23 (82%), thrombocytopenia in seven (25%), and anaemia in three (11%). Grade 4 neutropenia was reported in 22 (79%) patients after the first dose of prexasertib and was transient (median duration 6 days [IQR 4-8]) and recovered without growth-factor support in all cases. The treatment-related serious adverse event of grade 3 febrile neutropenia was reported in two (7%) patients. One patient died during the study due to tumour progression. INTERPRETATION: Prexasertib showed clinical activity and was tolerable in patients with BRCA wild-type high-grade serous ovarian carcinoma. This drug warrants further development in this setting, especially for patients with platinum-resistant or platinum-refractory disease. FUNDING: Intramural Research Program of the National Institutes of Health and National Cancer Institute.

Targeting BRCA1/2 deficient ovarian cancer with CNDAC-based drug combinations.

PURPOSE: The mechanism of action of CNDAC (2'-C-cyano-2'-deoxy-1-ß-D-arabino-pentofuranosyl-cytosine) is unique among deoxycytidine analogs because upon incorporation into DNA it causes a single strand break which is converted to a double strand break after DNA replication. This lesion requires homologous recombination (HR) for repair. CNDAC, as the parent nucleoside, DFP10917, and as an oral prodrug, sapacitabine, are undergoing clinical trials for hematological malignancies and solid tumors. The purpose of this study is to investigate the potential of CNDAC for the therapy of ovarian cancer (OC). METHODS: Drug sensitivity was evaluated using a clonogenic survival assay. Drug combination effects were quantified by median effect analysis. RESULTS: OC cells lacking function of the key HR genes, BRCA1 or BRCA2, were more sensitive to CNDAC than corresponding HR proficient cells. The sensitization was associated with greater levels of DNA damage in response to CNDAC at clinically achievable concentrations, manifested as chromosomal aberrations. Three classes of CNDAC-based drug combinations were investigated. First, the PARP1 inhibitors, rucaparib and talazoparib, were selectively synergistic with CNDAC in BRCA1/2 deficient OC cells (combination index < 1) at a relatively low concentration range. Second, cisplatin and oxaliplatin had additive combination effects with CNDAC (combination index ~ 1). Finally, paclitaxel and docetaxel achieved additive cell-killing effects with CNDAC at concentration ranges of the taxanes similar for both BRCA1/2 deficient and proficient OC cells. CONCLUSIONS: This study provides mechanistic rationales for combining CNDAC with PARP inhibitors, platinum compounds and taxanes in ovarian cancer lacking BRCA1/2 function.

Stimulation of lactate receptor (HCAR1) affects cellular DNA repair capacity.

Numerous G-protein coupled receptors have been reported to enhance cancer cell survival and resistance to clinically used chemotherapeutics. Recently, hydroxycarboxylic acid receptor 1 (HCAR1) was shown to drive lactate-dependent enhancement of cell survival and metastasis in pancreatic and breast cancers. Furthermore, our previous study confirmed the involvement of HCAR1 in lactate-related enhancement of DNA repair in cervical cancer cells. In the present study, we examined the possible mechanisms of HCAR1-mediated enhancement of DNA repair capacity. We observed that the HCAR1 agonist dihydroxybenzoic acid (DHBA) up-regulated BRCA1 (breast cancer type 1 susceptibility protein) and NBS1 (Nijmegen breakage syndrome 1) expression in HeLa cells. Moreover, HCAR1 silencing decreased mRNA and protein levels of BRCA1 by 30% and 20%, respectively. Immunocytochemical analyses of BRCA1, nibrin and DNA-PKcs indicated an increased accumulation of these proteins in cell nuclei after DHBA stimulation. Subsequently, these changes in the DNA repair protein levels translated into an enhanced DNA repair rate after doxorubicin treatment, as shown by γ-H2AX and comet assay experiments. In contrast, the down-regulation of HCAR1 decreased the efficiency of DNA repair. Finally, we observed the abrogation of DHBA-driven BRCA1 protein up-regulation and enhanced DNA repair following the preincubation of cells with the PKC inhibitor Gö6983. Taken together, our data indicate that lactate receptor/HCAR1 expression in cervical carcinoma cells may contribute to the modulation of cellular DNA repair mechanisms.

Loss of BRCA1 or BRCA2 markedly increases the rate of base substitution mutagenesis and has distinct effects on genomic deletions.

Loss-of-function mutations in the BRCA1 and BRCA2 genes increase the risk of cancer. Owing to their function in homologous recombination repair, much research has focused on the unstable genomic phenotype of BRCA1/2 mutant cells manifest mainly as large-scale rearrangements. We used whole-genome sequencing of multiple isogenic chicken DT40 cell clones to precisely determine the consequences of BRCA1/2 loss on all types of genomic mutagenesis. Spontaneous base substitution mutation rates increased sevenfold upon the disruption of either BRCA1 or BRCA2, and the arising mutation spectra showed strong and specific correlation with a mutation signature associated with BRCA1/2 mutant tumours. To model endogenous alkylating damage, we determined the mutation spectrum caused by methyl methanesulfonate (MMS), and showed that MMS also induces more base substitution mutations in BRCA1/2-deficient cells. Spontaneously arising and MMS-induced insertion/deletion mutations and large rearrangements were also more common in BRCA1/2 mutant cells compared with the wild-type control. A difference in the short deletion phenotypes of BRCA1 and BRCA2 suggested distinct roles for the two proteins in the processing of DNA lesions, as BRCA2 mutants contained more short deletions, with a wider size distribution, which frequently showed microhomology near the breakpoints resembling repair by non-homologous end joining. An increased and prolonged gamma-H2AX signal in MMS-treated BRCA1/2 cells suggested an aberrant processing of stalled replication forks as the cause of increased mutagenesis. The high rate of base substitution mutagenesis demonstrated by our experiments is likely to significantly contribute to the oncogenic effect of the inactivation of BRCA1 or BRCA2.

Leveraging DNA repair deficiency in gynecologic oncology.

PURPOSE OF REVIEW: The review discusses DNA repair deficiencies in ovarian cancer and how this has become the target for poly (ADP-ribose) polymerase (PARP) inhibition as a successful therapeutic strategy. RECENT FINDINGS: Hereditary ovarian cancers arise from germline mutations in BRCA1, BRCA2, or other important genes in the DNA repair process of homologous recombination. Sporadic ovarian cancers can also acquire a phenotype of homologous recombination deficiency through various other mechanisms. Recent studies have found the class of drugs called PARP inhibitors to selectively target ovarian cancers with homologous recombination deficiency. There are eight PARP inhibitors in various phases of clinical development with four being actively studied in phase III trials in ovarian cancer. In December 2014, the first-in-human PARP inhibitor olaparib was approved for ovarian cancer patients with two different clinical indications in Europe and the United States. SUMMARY: Ovarian cancer has become a model for the successful translation of targeted therapy against DNA repair deficiencies in cancer.

Triple-negative breast cancer: molecular subtypes and targeted therapy.

PURPOSE OF REVIEW: Triple-negative breast cancers (TNBCs), lacking estrogen receptor expression and human epidermal growth factor receptor 2 amplification, have no effective targeted therapy. Large-scale comprehensive genomic analyses have allowed stratification of TNBCs by molecular features. We will review the recent data regarding the classification of these poor prognosis cancers and the associated potential targeted treatment approaches. RECENT FINDINGS: TNBCs are a heterogeneous set of cancers characterized by a diverse set of gene-expression patterns and underlying genomic changes. Mutations in p53 are the only genomic alteration present in the majority of TNBCs. Other potential targetable alterations are only present in small subsets of TNBCs, and include defects in DNA repair present in BRCA1-mutant TNBCs and some sporadic TNBCs. Antiandrogens may be effective for TNBCs that express the androgen receptor and have luminal-like gene-expression features. PI3KCA pathway inhibitors and HSP90 inhibitors may also be effective in a small fraction of TNBCs. SUMMARY: Robust methods to functionally classify TNBCs to determine vulnerable pathways are urgently needed to guide the development of clinical trials. It is quite possible that TNBCs, like non-small cell lung cancer, will be stratified into many individually rare cancer classes, each requiring a distinct treatment approach.

miR-9 regulation of BRCA1 and ovarian cancer sensitivity to cisplatin and PARP inhibition.

BACKGROUND: Expression of BRCA1 is commonly decreased in sporadic ovarian cancer, and this is associated with platinum sensitivity and favorable prognosis. However, multiple mechanisms underlying low BRCA1 expression are not fully understood. METHODS: A bioinformatics-driven microRNA (miR) library screening was used to identify miRs that regulate BRCA1 expression. The effects of miR-9 on cisplatin (cDDP) and PARP inhibitor sensitivity were measured in ovarian cancer cells and C13* xenograft mice (n = 6 per group). The roles of miR-9 on prognosis were assessed in a cohort of ovarian cancer patients (n = 113) with Kaplan-Meier and Cox proportional hazards analyses. All statistical tests were two-sided. RESULTS: Reverse miR library screening revealed that miR-9 reduced the normalized luciferase activity to 60.3% (95% confidence interval [CI] = 52.0% to 68.5%; P < .001). miR-9 bound directly to the 3'-UTR of BRCA1 and downregulated BRCA1 expression in ovarian cancer cells. Treatment with miR-9 agomiR sensitized BRCA1-proficient C13* xenograft tumors to cisplatin and AG014699. In serous ovarian cancer, higher levels of miR-9 were inversely correlated with BRCA1 expression (Spearman rank correlation: R (2) = 0.379; P = .003). Patients with higher levels of miR-9 had better chemotherapy response, platinum sensitivity, and longer progression-free survival (PFS) (high vs low miR-9 expression: median PFS = 26.4 months, 95% CI = 13.8 to 39.0 months vs median PFS = 15.4 months, 95% CI = 6.8 to 23.9 months, P = .01). CONCLUSIONS: miR-9 mediates the downregulation of BRCA1 and impedes DNA damage repair in ovarian cancer. miR-9 may improve chemotherapeutic efficacy by increasing the sensitivity of cancer cells to DNA damage and may impact ovarian cancer therapy.

Soy phytoestrogens modify DNA methylation of GSTP1, RASSF1A, EPH2 and BRCA1 promoter in prostate cancer cells.

BACKGROUND: The aim of this study was to determine the effects of soy phytoestrogens on the methylation of promoter genes in prostate tumors. The incidence of prostate cancer in Asia is thirty percent lower than in Western countries. Since soy phytoestrogens represent a large portion of the Asian diet, evidence suggests their protective effect against prostate cancer. MATERIALS AND METHODS: In three human prostate cancer cell lines, methylation-specific-PCR was used to determine the effect of soy isoflavones (genistein and daidzein), compared to known demethylating agent 5-azacytidine as control in the promoter regions of glutathione S-transferase P1 (GSTP1), Ras association domain family 1 (RASSF1A), ephrin B2 (EPHB2) and breast cancer 1 (BRCA1) genes. In parallel, immunohistochemistry was used to assess the effects of genistein, daidzein and 5-azacytidine treatment on the corresponding protein expression. RESULTS: All studied promoters, with the exception of that for BRCA1, were strongly methylated without treatment. After treatment by phytoestrogens, demethylation of GSTP1 and EPHB2 promoter regions was observed and an increase in their protein expression was demonstrated by immunohistochemistry. CONCLUSION: Epigenetic modifications of DNA, such as the promoter CpG island demethylation of tumor suppressor genes, might be related to the protective effect of soy on prostate cancer.

A systematic review of genes involved in the inverse resistance relationship between cisplatin and paclitaxel chemotherapy: role of BRCA1.

A systematic review of cell models of acquired drug resistance not involving genetic manipulation showed that 80% of cell models had an inverse resistance relationship between cisplatin and paclitaxel. Here we systematically review genetically modified cell lines in which the inverse cisplatin/paclitaxel resistance phenotype has resulted. This will form a short list of genes which may play a role in the mechanism of the inverse resistance relationship as well as act as potential markers for monitoring the development of resistance in the clinical treatment of cancer. The literature search revealed 91 genetically modified cell lines which report toxicity or viability/apoptosis data for cisplatin and paclitaxel relative to their parental cell lines. This resulted in 26 genes being associated with the inverse cisplatin/paclitaxel phenotype. The gene with the highest number of genetically modified cell lines associated with the inverse resistance relationship was BRCA1 and this gene is discussed in detail with reference to chemotherapy response in cell lines and in the clinical treatment of breast, ovarian and lung cancer. Other genes associated with the inverse resistance phenotype included dihydrodiol dehydrogenase (DDH) and P-glycoprotein. Genes which caused cross resistance or cross sensitivity between cisplatin and paclitaxel were also examined, the majority of these genes were apoptosis associated genes which may be useful for predicting cross resistance. We propose that BRCA1 should be the first of a panel of cellular markers to predict the inverse cisplatin/paclitaxel resistance phenotype.

Phosphatidylinositol 3-kinase/Akt signaling enhances nuclear localization and transcriptional activity of BRCA1.

Signaling pathways involved in regulating nuclear-cytoplasmic distribution of BRCA1 have not been previously reported. Here, we provide evidence that heregulin beta1-induced activation of the Akt pathway increases the nuclear content of BRCA1. First, treatment of T47D breast cancer cells with heregulin beta1 results in a two-fold increase in nuclear BRCA1 as assessed by FACS analysis, immunoblotting and immunofluorescence. This heregulin-induced increase in nuclear BRCA1 is blocked by siRNA-mediated down-regulation of Akt. Second, mutation of threonine 509 in BRCA1, the site of Akt phosphorylation, to an alanine, attenuates the ability of heregulin to induce BRCA1 nuclear accumulation. These data suggest that Akt-catalyzed phosphorylation of BRCA1 is required for the heregulin-regulated nuclear concentration of BRCA1. Because most functions ascribed to BRCA1 occur within the nucleus, we postulated that phosphorylation-dependent nuclear accumulation of BRCA1 would result in enhanced nuclear activity, specifically transcriptional activity, of BRCA1. This postulate is affirmed by our observation that the ability of BRCA1 to transactivate GADD45 promoter constructs was enhanced in T47D cells treated with heregulin beta1. Furthermore, the heterologous expression of BRCA1 in HCC1937 human breast cancer cells, which have constitutively active Akt, also induces GADD45 promoter activity, whereas the expression of BRCA1 in which threonine 509 has been mutated to an alanine is able to only minimally induce promoter activity. These findings implicate Akt in upstream events leading to BRCA1 nuclear localization and function.

BRCA1 contributes to cell cycle arrest and chemoresistance in response to the anticancer agent irofulven.

Tumor suppressor gene BRCA1 is frequently mutated in familial breast and ovarian cancer. BRCA1 plays pivotal roles in maintaining genomic stability by interacting with numerous proteins in cell cycle control and DNA repair. Irofulven (6-hydroxymethylacylfulvene, HMAF, MGI 114, NSC 683863) is one of a new class of anticancer agents that are analogs of mushroom-derived illudin toxins. Preclinical studies and clinical trials have demonstrated that irofulven is effective against several tumor cell types. The exact nature of irofulven-induced DNA damage is not completely understood. We demonstrated previously that irofulven activates ATM and its targets, NBS1, SMC1, CHK2, and p53. In this study, we hypothesize that irofulven induces DNA double-strand breaks and that BRCA1 may affect chemosensitivity by controlling cell cycle checkpoints, DNA repair, and genomic stability in response to irofulven treatment. We observed that irofulven induces the formation of chromosome breaks and radials and the activation and foci formation of gamma-H2AX, BRCA1, and RAD51. We also provided evidence that irofulven induces the generation of DNA double-strand breaks. By using BRCA1-deficient or -proficient cells, we demonstrated that in response to irofulven, BRCA1 contributes to the control of S and G(2)/M cell cycle arrest and is critical for repairing DNA double-strand breaks and for RAD51-dependent homologous recombination. Furthermore, we found that BRCA1 deficiency results in increased chromosome damage and chemosensitivity after irofulven treatment.

Chemosensitization to cisplatin by inhibitors of the Fanconi anemia/BRCA pathway.

Cisplatin resistance occurs, at least in part, through the function of the Fanconi anemia (FA)/BRCA pathway, a DNA-damage response pathway required for repair of cisplatin cross-links. In the current study, we designed a cell-based screening strategy to identify small-molecule inhibitors of the FA/BRCA pathway with the hypothesis that such molecules could restore sensitivity to platinum agents. We identified four inhibitors, including three protein kinase inhibitors (wortmannin, H-9, and alsterpaullone) and one natural compound (curcumin) that inhibit the FA/BRCA pathway. We show that curcumin, a compound that is generally regarded as safe, inhibits the monoubiquitination of the FANCD2 protein as predicted by the screen and consequently sensitizes ovarian and breast tumor cell lines to cisplatin through apoptotic cell death. We believe that this study shows an efficient, high-throughput method for identifying new compounds that may sensitize cancer cells to DNA-damaging chemotherapy.