Abstract AP15: IDENTIFICATION OF P53 PRIONS AS AN INDEPENDENT PROGNOSTIC MARKER FOR SURVIVAL IN HIGH-GRADE SEROUS OVARIAN CANCER

PURPOSE: Although the discovery of prions was rewarded with a Nobel Prize, their existence was only attributed to a limited number of diseases. Recent evidence suggests that their role has been underestimated and several other proteins carry prion-like properties, like ß-amyloid, and most recently p53. High-grade serous ovarian cancers (HGSOC) harbor TP53 mutations in about 96% of cases. These mutations promote p53 aggregation, which might be responsible for complete abrogation of tumor suppressor functions, resulting in dominant-negative activity and oncogenic gain-of-function. Here, we describe the use of an ELISA-based technology for p53 prion detection in fresh-frozen tumor tissue and their clinical relevance in ovarian cancer.

EXPERIMENTAL PROCEDURES: Fresh-frozen tumor tissue specimens of 81 HGSOC patients, who previously had been included in the EU-funded OVCAD study, were analyzed. For each of these patients at least 5-year follow-up data were available. For the detection of p53 prions the Seprion-ELISA, previously designed for the detection of BSE and scrapie was adapted and optimized. To investigate the impact of p53 aggregation on clinical outcomes (overall survival and progression-free survival), we performed a complete-case analysis. In a subset of patients the Ki67 proliferation index and a homologous recombination deficiency (HRD) score, based on the Myriad score, were available. Correlations were analyzed using ANOVA and t-test.

RESULTS: In 39 of 46 (84.8%) patients with missense mutated cancers a p53 prion specific signal was observed. The aggregation propensity varied considerably within samples carrying the same mutations. Multivariable Cox regression models, with respect to other prognostic factors significantly associated with overall survival in patients with late-stage serous epithelial ovarian cancer (age, FIGO stage and presence of a residual tumor), show superiority of the group with extensive p53 aggregation in overall survival and in progression-free survival. No and moderate p53 aggregation are associated with a worse overall survival in contrast to high p53 aggregation (P values 0.025 and 0.011). Similar results in these groups are assessed for progression-free survival (P values 0.030 and 0.008). Interestingly, the group with extensive p53 aggregation was associated with a non-significant trend toward higher HR deficiency. Furthermore, this group had a significantly higher Ki67 index compared to patients with moderate p53 aggregation (P value 0.033).

CONCLUSIONS: This study reports the first specific and quantitative screening for p53 prions in patient material. We were able to demonstrate that the p53-Seprion-ELISA is a robust and highly sensitive detection tool for p53 prions. Our data show that the aggregation propensity is not only depending on the TP53 mutation and that other cofactors may be involved. Moreover, we show that p53 aggregation is an independent prognostic marker for survival. The higher Ki67 proliferation index and the trend towards higher genomic instability in patients with extensive p53 aggregation suggest that these tumors have an increased likelihood of response to platinum-containing therapy. To conclude, we demonstrated the high potential of p53 aggregation as a biomarker for patients' survival, suggesting that classification of patients based on the amount of aggregated p53 could allow therapy decisions.

Citation Format: Nicole Heinzl, Elisabeth Maritschnegg, Katarzyna Koziel, Stuart Wilson, Georg Heinze, Christine Wallisch, Reinhard Horvat, Jalid Sehouli, Ioana Braicu, Ignace Vergote, Els van Nieuwenhuysen, Sven Mahner, Eva Obermayr, Eva Schuster, Barbara Holzer, Nicole Concin, Robert Zeillinger. IDENTIFICATION OF P53 PRIONS AS AN INDEPENDENT PROGNOSTIC MARKER FOR SURVIVAL IN HIGH-GRADE SEROUS OVARIAN CANCER [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr AP15.

Integrative Kinome Profiling Identifies mTORC1/2 Inhibition as Treatment Strategy in Ovarian Clear Cell Carcinoma

Purpose: Advanced-stage ovarian clear cell carcinoma (OCCC) is unresponsive to conventional platinum-based chemotherapy. Frequent alterations in OCCC include deleterious mutations in the tumor suppressor ARID1A and activating mutations in the PI3K subunit PIK3CA In this study, we aimed to identify currently unknown mutated kinases in patients with OCCC and test druggability of downstream affected pathways in OCCC models.Experimental Design: In a large set of patients with OCCC (n = 124), the human kinome (518 kinases) and additional cancer-related genes were sequenced, and copy-number alterations were determined. Genetically characterized OCCC cell lines (n = 17) and OCCC patient-derived xenografts (n = 3) were used for drug testing of ERBB tyrosine kinase inhibitors erlotinib and lapatinib, the PARP inhibitor olaparib, and the mTORC1/2 inhibitor AZD8055.Results: We identified several putative driver mutations in kinases at low frequency that were not previously annotated in OCCC. Combining mutations and copy-number alterations, 91% of all tumors are affected in the PI3K/AKT/mTOR pathway, the MAPK pathway, or the ERBB family of receptor tyrosine kinases, and 82% in the DNA repair pathway. Strong p-S6 staining in patients with OCCC suggests high mTORC1/2 activity. We consistently found that the majority of OCCC cell lines are especially sensitive to mTORC1/2 inhibition by AZD8055 and not toward drugs targeting ERBB family of receptor tyrosine kinases or DNA repair signaling. We subsequently demonstrated the efficacy of mTORC1/2 inhibition in all our unique OCCC patient-derived xenograft models.Conclusions: These results propose mTORC1/2 inhibition as an effective treatment strategy in OCCC. Clin Cancer Res; 24(16); 3928-40. ©2018 AACR.

Methylome analysis of extreme chemoresponsive patients identifies novel markers of platinum sensitivity in high-grade serous ovarian cancer

BACKGROUND

Despite an early response to platinum-based chemotherapy in advanced stage high-grade serous ovarian cancer (HGSOC), the majority of patients will relapse with drug-resistant disease. Aberrant epigenetic alterations like DNA methylation are common in HGSOC. Differences in DNA methylation are associated with chemoresponse in these patients. The objective of this study was to identify and validate novel epigenetic markers of chemoresponse using genome-wide analysis of DNA methylation in extreme chemoresponsive HGSOC patients.

METHODS

Genome-wide next-generation sequencing was performed on methylation-enriched tumor DNA of two HGSOC patient groups with residual disease, extreme responders (≥18 months progression-free survival (PFS), n = 8) and non-responders (≤6 months PFS, n = 10) to platinum-based chemotherapy. DNA methylation and expression data of the same patients were integrated to create a gene list. Genes were validated on an independent cohort of extreme responders (n = 21) and non-responders (n = 31) using pyrosequencing and qRT-PCR. In silico validation was performed using publicly available DNA methylation (n = 91) and expression (n = 208) datasets of unselected advanced stage HGSOC patients. Functional validation of FZD10 on chemosensitivity was carried out in ovarian cancer cell lines using siRNA-mediated silencing.

RESULTS

Integrated genome-wide methylome and expression analysis identified 45 significantly differentially methylated and expressed genes between two chemoresponse groups. Four genes FZD10, FAM83A, MYO18B, and MKX were successfully validated in an external set of extreme chemoresponsive HGSOC patients. High FZD10 and MKX methylation were related with extreme responders and high FAM83A and MYO18B methylation with non-responders. In publicly available advanced stage HGSOC datasets, FZD10 and MKX methylation levels were associated with PFS. High FZD10 methylation was strongly associated with improved PFS in univariate analysis (hazard ratio (HR) = 0.43; 95% CI, 0.27-0.71; P = 0.001) and multivariate analysis (HR = 0.39; 95% CI, 0.23-0.65; P = 0.003). Consistently, low FZD10 expression was associated with improved PFS (HR = 1.36; 95% CI, 0.99-1.88; P = 0.058). FZD10 silencing caused significant sensitization towards cisplatin treatment in survival assays and apoptosis assays.

CONCLUSIONS

By applying genome-wide integrated methylome analysis on extreme chemoresponsive HGSOC patients, we identified novel clinically relevant, epigenetically-regulated markers of platinum-sensitivity in HGSOC patients. The clinical potential of these markers in predictive and therapeutic approaches has to be further validated in prospective studies.

Clinical characterization of long term survivors (LTS) in ovarian cancer (OC): Results of a propensity score matched (PSM) analysis of the international prospective tumor bank for ovarian cancer (TOC Network)

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Background: OC has the highest mortality rate amongst gynecological malignancies. Nevertheless a small fraction of OC patients will survive longer than 8 years. Aim of our study was to analyze differences in the clinical appearance and management of LTS versus “classical” OC patients. Methods: OC patients living longer than 8 years were identified within the TOC Network between 1998 and 2008, representing the LTS subgroup. PSM analysis was used to select comparable groups of LTS and OC patients who died within first 5 years (control group - CG). PSM was conducted using nearest neighbor caliper matching without replacement to match LTS and CG for age, FIGO and residual tumor mass. All calculations were performed with the R project for Statistical Computing (R-packages used: “MatchIt”). Results: A total of 347 OC patients with different histological subtypes were included in the current analysis, i.e. 173 LTS and 174 in the CG. After PSM 114 patients remained in each group. Patients had similar age, FIGO stage and residual mass (p = 0.99, p = 0.35 and p = 0.88, respectively). Tumor spread in middle and upper abdomen (p = 0.002 and 0.013, respectively) was higher and diaphragm, mesentery and peritoneum (p = 0.009, 0.037 and 0.002, respectively) were significantly more often involved in CG than in the LTS. When only considering the HGSOC patients, 95 patients remained in each group. All patients received surgery and platinum based chemotherapy. The PSM analysis showed significant higher involvement of upper abdomen (p = 0.028), higher peritoneal spread (p = 0.002), higher ascites volume (p = 0.0007) and higher bowel resection rates (p = 0.002) in the CG compared to LTS. Neoadjuvant chemotherapy rate was similar in the LTS and CG (p = 0.5). Conclusions: Based on this PSM analysis, HGSOC-LTS seem to have mainly similar clinical pattern as the control group, however with lower rates of ascites and involvement of upper abdomen. Molecular characterization including analysis of clonal diversity might help elucidate mechanisms of tumor spread and good prognosis.

Treatment reality in elderly patients with advanced ovarian cancer: a prospective analysis of the OVCAD consortium

Background

Approximately one third of women diagnosed with ovarian cancer is 70 years or older. Information on the treatment reality of these elderly patients is limited.

Methods

275 patients with primary epithelial ovarian cancer FIGO stage II-IV undergoing cytoreductive surgery and platinum-based chemotherapy were prospectively included in this European multicenter study. Patients <70 and ≥70 years were compared regarding clinicopathological variables and prognosis.

Results

Median age was 58 years (18–85); 47 patients (17.1%) were 70 years or older. The postoperative 60-day-mortality rate was 2.1% for elderly and 0.4% for younger patients (p < 0.001). Elderly patients were less likely to receive optimal therapy (no residual disease after surgery and platinum combination chemotherapy) compared to patients <70 years (40.4% vs. 70.1%, p < 0.001) and their outcome was less favorable regarding median PFS (12 vs. 20 months, p = 0.022) and OS (30 vs. 64 months, p < 0.001). However, in multivariate analysis age itself was not a prognostic factor for PFS while the ECOG performance status had prognostic significance in elderly patients.

Conclusions

Elderly patients with ovarian cancer are often treated less radically. Their outcome is impaired despite no consistent prognostic effect of age itself. Biological age and functional status should be considered before individualized treatment plans are defined.