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SummaryUnderstanding the mechanism underlying the regulation of the androgen receptor (AR), a central player in the development of castration-resistant prostate cancer (CRPC), holds promise for overcoming the challenge of treating CRPC. We demonstrate that the ubiquitin ligase Siah2 targets a select pool of NCOR1-bound, transcriptionally-inactive AR for ubiquitin-dependent degradation, thereby promoting expression of select AR target genes implicated in lipid metabolism, cell motility, and proliferation. Siah2 is required for prostate cancer cell growth under androgen-deprivation conditions in vitro and in vivo, and Siah2 inhibition promotes prostate cancer regression upon castration. Notably, Siah2 expression is markedly increased in human CRPCs. Collectively, we find that selective regulation of AR transcriptional activity by the ubiquitin ligase Siah2 is important for CRPC development.

The relationship between habitual consumption of foods with a high glycemic index (GI) and/or a diet with a high glycemic load (GL) and risk of endometrial cancer is uncertain, and relatively few studies have investigated these associations. The objectives of this study were to examine the association between GI/GL and risk of endometrial cancer using data from an Australian population-based case-control study and systematically review all the available evidence to quantify the magnitude of the association using meta-analysis.The case-control study included 1,290 women aged 18-79 years with newly diagnosed, histologically confirmed endometrial cancer and 1,436 population controls. Controls were selected to match the expected Australian state of residence and age distribution (in 5-year bands) of cases. For the systematic review, relevant studies were identified by searching PubMed and Embase databases through to July 2011. Random-effects models were used to calculate the summary risk estimates, overall and dose-response.In our case-control study, we observed a modest positive association between high dietary GI (OR 1.43, 95 % CI 1.11-1.83) and risk of endometrial cancer, but no association with high dietary GL (OR 1.15, 95 % CI 0.90-1.48). For the meta-analysis, we collated information from six cohort and two case-control studies, involving a total of 5,569 cases. The pooled OR for the highest versus the lowest intake category of GI was 1.15 (0.95-1.40); however, there was significant heterogeneity (p 0.004) by study design (RR 1.00 [95 % CI 0.87-1.14] for cohort studies and 1.56 [95 % CI 1.21-2.02] for case-control studies). There was no association in the dose-response meta-analysis of GI (RR per 5 unit/day increment of GI 1.00, 95 % CI 0.97-1.03). GL was positively associated with endometrial cancer. The pooled RR for the highest versus the lowest GL intake was 1.21 (95 % CI 1.09-1.33) and 1.06 (95 % CI 1.01-1.11) per 50 unit/day increment of GL in the dose-response meta-analysis.The pooled results from observational studies, including our case-control results, provide evidence of a modest positive association between high GL, but not GI, and endometrial cancer risk.

Low-grade serous ovarian cancer (LGSC) responds poorly to platinum based chemotherapy and is characterized by activating RAS-MAPK pathway mutations, including oncogenic BRAF. Drugs that target this pathway are effective in BRAF-mutant melanoma but other cancer types, such as colorectal cancers, are less sensitive. Early phase trials report a 15% response rate to MEK inhibitors in LGSC patients, however it is not known which features may predict response. We aimed to determine clinical characteristics and treatment response in women with LGSC and to determine whether response to targeted pathway inhibition is associated with specific mutation profiles in LGSC cell lines. Tumor samples from a cohort of grade 1 and 2 serous ovarian cancer patients were analyzed using targeted, exome or whole genome sequencing. Patient characteristics, treatment and clinical outcome were assessed. Cell lines derived from patients with LGSC with known mutation profiles, AOCS2 (KRAS/BRAF/NRAS wild-type), MPSC1 (BRAFV600L, NRASQ16R), VOA1056 (NRASQ16R) and HCC5075 (KRASG12V), were treated with BRAF (dabrafenib) or MEK inhibitors (trametinib, pimasertib and binimetinib) and response was compared to cell lines derived from high-grade serous cancer (HGSC) and BRAF-mutant melanoma. Women diagnosed with grade 1 or 2 serous carcinoma between 1994-2015 were identified from 1654 invasive ovarian serous cancer cases in the Australian Ovarian Cancer Study and the GynBiobank. HGSC cases were excluded following histopathology review and TP53 mutation screening. Amongst 65 confirmed LGSC patients, 18 (27.7%) had a KRAS mutation, 9 (13.8%) had a BRAF mutation and 7 (10.8%) had a NRAS mutation. Women with advanced stage LGSC and residual disease following debulking surgery had a similarly poor progression-free and overall-survival compared with HGSC patients. We saw a dramatic response to BRAF inhibition in a patient with BRAFV600E-positive LGSC, however, the LGSC cell lines did not respond to dabrafenib. This is not surprising as the cell lines did not harbour the hot-spot BRAFV600E mutation. MPSC1 has a BRAFV600L and a NRASQ16R mutation, but dabrafenib did not inhibit growth. HCC5075 (KRASG12V) was sensitive to all three MEK inhibitors, but response to MEK inhibition in the other LGSC cell lines was modest. In conclusion, LGSC are generally chemotherapy resistant and molecular analyses can identify targetable mutations. However, LGSC are heterogenous with respect to underlying mutations and response to pathway inhibitors is likely to depend on which mutations and pathways are activated. BRAF mutations are not uncommon in patients with LGSC and should be routinely tested as BRAF inhibitors can be an effective treatment for these patients. MEK inhibitors may also be effective in a subset of cases. The results highlight the need for novel clinical trial design, as traditional clinical trials are unlikely to be effective in rare ovarian cancer sub-types. Citation Format: Tania Moujaber, Dariush Etemadmoghadam, Cristina Mapagu, Catherine Kennedy, Yoke-Eng Chiew, Casina Kan, Nikilyn Nevins, Sivatharsny Srirangan, Sian Fereday, Nadia Traficante, Australian Ovarian Cancer Study group, David Bowtell, Rosemary Balleine, Paul Harnett, Anna deFazio. Mutations in low-grade serous ovarian cancer and response to BRAF and MEK inhibitors [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 2584.

ABCB1 (adenosine triphosphate-binding cassette transporter B1) mediates cellular elimination of many chemotherapeutic agents including paclitaxel, which is commonly used to treat ovarian cancer. A significant association between common single nucleotide polymorphisms (SNPs) in ABCB1 and progression-free survival has been reported in patients with ovarian cancer. Variable paclitaxel clearance due to genotype specific differences in ABCB1 activity in cancer cells and/or normal tissues may underlie the association. Using cell-based models, we evaluated the correlations between ABCB1 expression, polymorphisms, transporter activity and paclitaxel sensitivity in ovarian cancer (n = 10) and lymphoblastoid (n = 19) cell lines. Close associations between ABCB1 expression, transporter function and paclitaxel sensitivity were found in lymphoblastoid cell lines, although we could not demonstrate an association with common SNPs. In ovarian cancer cell lines, ABCB1 expression was low and the association between expression and function was lost. These results suggest that ABCB1 related survival difference in ovarian cancer patients is more likely to be due to differential whole body paclitaxel clearance mediated by normal cells rather than a direct effect on cancer cells.

Purpose: A significant number of women with serous ovarian cancer are intrinsically refractory to platinum-based treatment. We analyzed somatic DNA copy number variation and gene expression data to identify key mechanisms associated with primary resistance in advanced-stage serous cancers. Experimental Design: Genome-wide copy number variation was measured in 118 ovarian tumors using high-resolution oligonucleotide microarrays. A well-defined subset of 85 advanced-stage serous tumors was then used to relate copy number variation to primary resistance to treatment. The discovery-based approach was complemented by quantitative-PCR copy number analysis of 12 candidate genes as independent validation of previously reported associations with clinical outcome. Likely copy number variation targets and tumor molecular subtypes were further characterized by gene expression profiling. Results: Amplification of 19q12, containing cyclin E (CCNE1), and 20q11.22-q13.12, mapping immediately adjacent to the steroid receptor coactivator NCOA3, was significantly associated with poor response to primary treatment. Other genes previously associated with copy number variation and clinical outcome in ovarian cancer were not associated with primary treatment resistance. Chemoresistant tumors with high CCNE1 copy number and protein expression were associated with increased cellular proliferation but so too was a subset of treatment-responsive patients, suggesting a cell-cycle independent role for CCNE1 in modulating chemoresponse. Patients with a poor clinical outcome without CCNE1 amplification overexpressed genes involved in extracellular matrix deposition. Conclusions: We have identified two distinct mechanisms of primary treatment failure in serous ovarian cancer, involving CCNE1 amplification and enhanced extracellular matrix deposition. CCNE1 copy number is validated as a dominant marker of patient outcome in ovarian cancer.

Background: X chromosome inactivation, which silences gene expression from one of the two X chromosomes in females, is usually random. Skewed X inactivation has been implicated in both the expression and the suppression of X-linked disease phenotypes and has been reported to occur more frequently in breast and ovarian cancer patients, including BRCA1 or BRCA2 mutation carriers, than in control subjects. Methods: We assessed the pattern of X chromosome inactivation using methylation-specific polymerase chain reaction amplification of the exon 1 microsatellite region of the X-linked androgen receptor (AR) gene in DNA from blood samples obtained from control subjects without a personal history of breast or ovarian cancer (n = 735), ovarian cancer patients (n = 313), familial breast cancer patients who did not carry mutations in BRCA1 or BRCA2 (n = 235), and affected and unaffected carriers of mutations in BRCA1 (n = 260) or BRCA2 (n = 63). We defined the pattern of X chromosome inactivation as skewed when the same X chromosome was active in at least 90% of cells. The association between skewed X inactivation and disease and/or BRCA mutation status was assessed by logistic regression analysis. The association between skewed X inactivation and age at cancer diagnosis was assessed by Cox proportional hazards regression analysis. All statistical tests were two-sided. Results: The age-adjusted frequency of skewed X inactivation was not statistically significantly higher in ovarian cancer or familial breast cancer case subjects compared with control subjects. Skewed X inactivation was higher in BRCA1 mutation carriers than in control subjects (odds ratio [OR] = 2.7, 95% confidence interval [CI] = 1.1 to 6.2; P = .02), particularly among unaffected women (OR = 6.1, 95% CI = 1.5 to 31.8; P = .005). Among BRCA1 mutation carriers, those with skewed X inactivation were older at diagnosis of breast or ovarian cancer than those without skewed X inactivation (hazard ratio [HR] of breast or ovarian cancer = 0.37, 95% CI = 0.14 to 0.95; P = .04). Among BRCA2 mutation carriers, skewed X inactivation also occurred more frequently in unaffected carriers than in those diagnosed with breast or ovarian cancer (OR = 5.2, 95% CI = 0.5 to 28.9; P = .08) and was associated with delayed age at onset (HR = 0.59, 95% CI = 0.37 to 0.94; P = .03). Conclusions: Skewed X inactivation occurs at an increased frequency in BRCA1 (and possibly BRCA2) mutation carriers compared with control subjects and is associated with a statistically significant increase in age at diagnosis of breast and ovarian cancer. © The Author 2008

Background: The five year survival rate for women with ovarian cancer (OC) is less than 40%. Crucial to improving the outcomes for ovarian cancer patients is the development of accurate pre-clinical models of human epithelial OC, which can be used to unravel the mechanisms underlying its evolution and behaviour. Methods: We have generated a novel xenograft model of human high-grade serous OC (HG-SOC) in order to enable preclinical molecular and drug response assessment of individual HG-SOC: this includes a comparison of standard OC xeno-transplantion approaches (intra-peritoneal, subcutaneous and sub renal capsular), with the novel use of the rodent ovarian bursa, the orthotopic site. Utilising the rodent bursa may better replicate the relevant microenvironment and increase the success of EOC xeno-transplantion. Other aspects designed to optimize the model include the use of NOD-SCID-IL-2rg recipient mice, systemic estrogen supplementation and transplantation of fresh human HG-SOC fragments which have had no prior in vitro culture. Histological, functional and molecular analysis of the novel xenograft cohort (at baseline and following xenotransplantation) includes histological review; documentation of in vitro Homologous Recombination (HR) DNA repair and drug response capabilities (using novel α-irradiation and explant drug assays); classification according to molecular subtype (Tothill classfier); documentation of NHEJ pathway status, BRCA1/2 status and other DNA repair gene status. In vivo drug treatment studies are being performed, with the choice of treatment targeted to the specific molecular characteristics of the HG-SOC in question. Results: Fourteen consecutive chemotherapy naive potentially HG-SOC samples have been collected. Corresponding clinical data has been collected. Data concerning DNA repair capability and response to DNA damaging agents will be presented, including IHC for markers of DNA damage (γH2AX), DNA repair (RAD51) and apoptosis (capsase 3 cleavage). HG-SOC in this cohort have been classified according to Tothilll (Tothill et al 2008). Eight appropriate HG-SOC have been transplanted and 5 of the first 6 have successfully xenografted, with phenotyping of xenografts underway. In vivo analysis of response to cisplatin treatment and other relevant therapeutics will be presented. Conclusions: A novel xenograft model has been developed of human HG-SOC, which includes comparative characterization of important prognostic features both in the baseline panel of fresh human HG-SOC and in subsequent xenografts. This clinically, functionally and molecularly annotated consecutive xenograft cohort of HG-SOC will provide outstanding utility for the development of improved therapeutic approaches. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3276. doi:1538-7445.AM2012-3276