Nicole Concin

Transdominant ΔTAp73 Isoforms Are Frequently Up-regulated in Ovarian Cancer. Evidence for Their Role as Epigenetic p53 Inhibitors in Vivo

Despite strong homology, the roles of TP53 and TP73 in tumorigenesis seem to be fundamentally different. In contrast to TP53, tumor-associated overexpression of TP73 in many different cancers, combined with virtual absence of inactivating mutations and lack of a cancer phenotype in the TP73 null mouse are inconsistent with a suppressor function but instead support an oncogenic function. The discovery of NH2-terminally truncated p73 isoforms, collectively called ΔTAp73, is now the focus of intense interest because they act as potent transdominant inihibitors of wild-type p53 and transactivation-competent TAp73. Therefore, establishing deregulated ΔTAp73 expression in tumors could be the crucial link to decipher which of the two opposing roles of this bipolar gene is the biologically relevant one. This study is the largest to date and encompasses 100 ovarian carcinomas with complete expression profile of all NH2-terminal isoforms, discriminating between TAp73 and ΔTAp73 (ΔNp73, ΔN′p73, Ex2p73, and Ex2/3p73) by isoform-specific real-time reverse transcription-PCR. We find that the set of NH2-terminal p73 isoforms distinguishes ovarian cancer patients from healthy controls and thus is a molecular marker for this diagnosis. Ovarian cancers strongly and almost universally overexpress ΔN′p73 compared with normal tissues (95% of cancers). About one-third of tumors also exhibit concomitant up-regulation of the antagonistic TAp73, whereas only a small subgroup of tumors overexpress ΔNp73. Thus, deregulation of the E2F1-responsive P1 promoter, rather than the alternate P2 promoter, is mainly responsible for the production of transdominant p53/TAp73 antagonists in ovarian cancer. Tumor stage, grade, presence of metastases, p53 status, and residual disease after resection are significant prognostic markers for overall and recurrence-free survival. A trend is found for better overall survival in patients with low expression of ΔN′p73/ΔNp73, compared with patients with high expression. A strong correlation between deregulated ΔTAp73 and p53 status exists. p53 wild-type cancers exhibit significantly higher deregulation of ΔN′p73, ΔNp73, and Ex2/3p73 than p53 mutant cancers. This data strongly supports the hypothesis that overexpression of transdominant p73 isoforms can function as epigenetic inhibitors of p53 in vivo, thereby alleviating selection pressure for p53 mutations in tumors.

Clinical Relevance of Dominant-Negative p73 Isoforms for Responsiveness to Chemotherapy and Survival in Ovarian Cancer: Evidence for a Crucial p53-p73 Cross-talk In vivo

Purpose: We aimed to determine the clinical role of the p53 family members p53 and p73 in the responsiveness to platinum-based chemotherapy and survival in ovarian cancer, considering their cross-talk and the p53 polymorphism at codon 72. Experimental Design: A detailed analysis of p53 and p73 in a series of 122 ovarian cancers was done. We used a functional yeast-based assay to determine the p53 mutational status. Red yeast colonies, indicating mutant p53, were subsequently sequenced to determine the specific p53 alteration. p53 mutations were divided into two groups according to their previous characterization in the literature: those that efficiently inhibit transcriptionally active TAp73 function and those that do not. A p53 polymorphism at codon 72 was determined in corresponding normal tissue or blood of ovarian cancer patients. Isoform-specific p73 expression analysis using real-time reverse transcription-PCR has previously been done in the majority of ovarian cancers included in this study. In a retrospective chart review, responsiveness to chemotherapy was assessed, and survival data with long follow-up times were collected. Results: Eighty of 122 (65.6%) of ovarian cancers harbored p53 mutations. p53 mutational status was an important determinant of responsiveness to platinum-based chemotherapy in all patients with a residual tumor of <2 cm in diameter after initial surgery (wild-type versus mutant, P = 0.029). In addition, p53 mutational status was a strong prognosticator for recurrence-free and overall survival (P < 0.0001 and P = 0.003, respectively) in univariate analyses. High expression levels of dominant-negative p73 isoforms (ΔNp73 and ΔN′p73) significantly correlated with chemotherapeutic failure (P = 0.048) and with worse recurrence-free and overall survival in patients with p53 mutant cancers (P = 0.048 and P = 0.005, respectively). Eight p53 mutations, present in 19 cases, were found that efficiently inhibit TAp73 (i.e., 175H, 220C, 245S, 245D, 248W, 248Q, 266E, and 273H). Patients with p53 mutations that efficiently inhibit TAp73 function had a significantly shorter overall survival than patients with p53 mutations of unknown effect on TAp73 (P = 0.044). The p53 polymorphism at codon 72 had no influence on responsiveness to chemotherapy or survival. Conclusion: We provide the first clinical evidence that dominant-negative p73 isoforms contribute to drug resistance in vivo, underscoring the importance of a p53-p73 cross-talk. NH2-terminally truncated p73 isoforms were of significant clinical effect by providing an additional unfavorable factor for response to platinum-based chemotherapy and survival in p53 mutant ovarian cancers.

Clinical Relevance of E2F Family Members in Ovarian Cancer—An Evaluation in a Training Set of 77 Patients

Purpose: The major obstacle in treating ovarian cancer is the rapid development of platinum resistance during therapy. Deregulation of members of the E2F family of transcription factors is crucially involved in carcinogenesis and probably in mechanisms underlying platinum resistance. We therefore investigated the relevance of the whole set of E2F family members in predicting clinical outcome and their significance in predicting platinum resistance. Experimental Design: Real-time PCR of all E2F family members was done from 77 ovarian carcinomas, defined as our training set, and 8 healthy control samples. The correlation with clinicopathologic characteristics, platinum resistance, and survival was investigated. Furthermore, the cross-talk of E2F family members was assessed for its value in predicting survival and platinum resistance. Results: The proliferation-promoting E2F1 and E2F2 were associated with grade 3 tumors and residual disease >2 cm in diameter after initial surgery. Survival analyses showed low expression of E2F1 or E2F2 to be significantly associated with favorable disease-free and overall survival (E2F1, P = 0.039 and 0.047, respectively; E2F2, P = 0.009 and 0.006, respectively). In contrast, high expression of inhibiting E2F4 or E2F7 predicted favorable disease-free and overall survival (E2F4, P = 0.047 and 0.042, respectively; E2F7, P = 0.048 and 0.042, respectively). A high E2F2 to E2F4 ratio was the most valuable prognostic variable for disease-free survival in multivariate analysis (hazard ratio, 6.494; P = 0.002). Tumors considered platinum resistant were associated with lower E2F4 and E2F7 expression (P = 0.012 and 0.009, respectively) compared with platinum-sensitive tumors. Again, ratios of E2F1 or E2F2 to E2F7 were the most favorable variables in predicting platinum resistance. Conclusions: We here show that deregulation of both proliferation-promoting and proliferation-inhibiting E2F transcription factors and their cross-talk is crucially involved in the tumor biology of ovarian cancer and influences clinical outcome. Furthermore, down-regulation of E2F7 may contribute to mechanisms underlying platinum resistance, and calculation of ratios of proliferation-promoting E2F1 to E2F7 could serve as a putative predictor of platinum resistance.

Plasma Fibrinogen Levels and Prognosis in Patients with Ovarian Cancer: A Multicenter Study

INTRODUCTION To evaluate pretherapeutic plasma fibrinogen levels as a prognostic parameter in patients with epithelial ovarian cancer (EOC). Materials and Methods. In the present multicenter study, pretherapeutic plasma fibrinogen levels were evaluated in 422 patients with EOC. Plasma fibrinogen levels were correlated with clinicopathological parameters and patient survival. RESULTS The mean (standard deviation) pretherapeutic plasma fibrinogen level was 450.0 (150.1) mg/dl. Elevated plasma fibrinogen levels were associated with advanced tumor stage (p = .01) and the presence of a postoperative residual tumor mass (p < .001), but not with histological grade (p = .1) and histological type (p = .8). In a multivariate Cox regression model, tumor stage (p < .001 and p < .001), postoperative residual tumor mass (p = .001 and p = .008), and plasma fibrinogen level (p < .001 and p = .002), but not histological type (p = .8 and p = .2), patient age (p = .9 and p = .9), and serum cancer antigen 125 (p = 0.2 and p = 0.3) and C-reactive protein (p = .2 and p = .3) levels, were associated with disease-free and overall survival, respectively. Histological grade was associated with overall but not with disease-free survival (p = .01 and p = .8), respectively. CONCLUSIONS Pretherapeutic plasma fibrinogen levels can be used as an independent prognostic parameter in patients with EOC.

Alternative splicing of p53 and p73 : the novel p53 splice variant p53δ is an independent prognostic marker in ovarian cancer

Similar to p73, the tumor suppressor gene p53 is subject to alternative splicing. Besides p53ΔE6 and p53β, we identified p53ζ, p53δ and p53ɛ, arising from alternative splicing of exon 6 and intron 9, respectively. p53 splice variants were present in 18 of 34 ovarian cancer cell lines (52.9%) and 134 of 245 primary ovarian cancers (54.7%). p53δ expression was associated with impaired response to primary platinum-based chemotherapy (P=0.032). Also, p53δ expression constituted an independent prognostic marker for recurrence-free and overall survival (hazard ratio 1.854, 95% confidence interval 1.121–3.065, P=0.016; and hazard ratio 1.937, 95% confidence interval 1.177–3.186, P=0.009, respectively). p53β expression was associated with adverse clinicopathologic markers, that is, serous and poorly differentiated cancers (P=0.002 and P=0.008, respectively), and correlated with worse recurrence-free survival in patients exhibiting functionally active p53 (P=0.049). ΔN′p73 constituted the main N-terminally truncated p73 isoform and was preferentially found in ovarian cancer cell lines showing functionally active p53, supporting our hypothesis that N-terminally truncated p73 isoforms can alleviate the selection pressure for p53 mutations by the inhibition of p53 protein function.

Expression of the E2F Family of Transcription Factors and Its Clinical Relevance in Ovarian Cancer

Abstract:  The E2F family of transcription factors plays a pivotal role in the regulation of cellular proliferation. On the basis of sequence homology and function, eight distinct members of E2F transcription factors (E2F‐1 to E2F‐8) have been distinguished to date. The regulation of E2F transcription factors is closely associated with the function of the retinoblastoma family of tumor suppressors (RB pathway). In the last decade various alterations of distinct components of the RB‐E2F pathway were found to be associated with tumor progression. However, no data on the role of E2F family members are available in tumor biology of ovarian cancer. Here we describe an expression study of E2F transcription factors in various human ovarian cancer cell lines; its clinical relevance was examined in a training set of 77 ovarian cancer patients. Expression levels of E2F‐1, E2F‐2, and E2F‐8 were elevated in all the ovarian cancer cell lines studied when compared with human peritoneal mesothelial cells (HPMCs). Interestingly, EGF treatment showed a time‐dependent upregulation of the activating transcription factor E2F‐3 and a simultaneous increase of DP‐1, the heterodimeric partner of E2F‐3. High expression of E2F‐1, E2F‐2, and E2F‐8 was found to be associated with histopathologic grade 3 tumors and residual tumor over 2 cm in diameter after primary debulking surgery in ovarian cancer patients. Taken together, these data suggest that the proliferation‐promoting E2F transcription factors E2F‐1 and especially E2F‐2 play a pivotal role in tumor biology of ovarian cancer and may be candidates for specific therapeutic targets.

Prognostic value of residual tumor size in patients with epithelial ovarian cancer FIGO stages IIA-IV: analysis of the OVCAD data.

Objective The objective of the study was to evaluate the prognostic impact of residual tumor size after cytoreductive surgery in patients with epithelial ovarian cancer. Methods In this prospective, multicenter study, 226 patients with epithelial ovarian cancer (International Federation of Gynecology and Obstetrics stages IIA–IV) were included. Patients were treated with cytoreductive surgery and adjuvant platinum-based chemotherapy. Univariate and multivariable survival analyses were performed to investigate the impact of residual tumor size on progression-free and overall survival. Results In 69.4% of patients, surgery resulted in complete tumor resection; minimal residual disease (≤1 cm) was achieved in 87.2% of patients. Advanced tumor stage was associated with a lower rate of complete tumor resection (P < 0.001). After cytoreductive surgery, 3-year overall survival rates were 72.4%, 65.8%, and 45.2% for patients without, with minimal, and with gross residual disease (>1 cm), respectively (P < 0.001). Multivariable survival analysis revealed residual tumor size (P = 0.04) and older patient age (P = 0.02) as independent prognosticators for impaired overall survival. Complete cytoreduction was predictive for a higher rate of treatment response (P = 0.001) and was associated with prolonged progression-free and overall survival (P < 0.001 and P = 0.001). Conclusions The size of residual disease after cytoreduction is one of the most crucial prognostic factors for patients with ovarian cancer. Patients after complete cytoreduction have a superior outcome compared with patients with residual disease. Leaving no residual tumor has to be the aim of primary surgery for ovarian cancer; therefore, patients should receive treatment at centers able to undertake complex cytoreductive procedures.

Comparison of p53 Mutational Status with mRNA and Protein Expression in a Panel of 24 Human Breast Carcinoma Cell Lines

We analyzed the p53 mutational status, mRNA and protein expression in 24 human breast carcinoma cell lines. Following measurement of their DNA content with flow cytometry, we ascertained the copy numbers of the centromere of chromosome 17 (cen17) and p53 with fluorescence in situ hybridization (FISH). A functional yeast assay (FASAY) was used to screen for inactivating mutations. Positive results were subsequently verified by DNA sequencing. Finally, we assessed the mRNA expression with a competitive reverse transcription-polymerase chain reaction (RT-PCR) assay and the protein expression with immunocytochemical staining, western blot, and quantitative flow cytometry. The DNA content of the cell lines ranged from 0.85 to 2.58. Nine cell lines had concordant copy numbers (between two and four) of p53 and cen17, whereas 12 had more, and three less cen17 than p53 copies. The FASAY was successful in all but one cell line and revealed the presence of mutated alleles in 16 of them, 13 cell lines expressed only the mutated, and three both the mutated and the wild-type alleles. The mutations were comprised of 11 missense, two nonsense, and three frameshift mutations. Immunocytochemical staining, western blot and quantitative flow cytometry yielded comparable p53 protein expression results. However, both the mRNA and the protein expression levels varied considerably in the different cell lines and no consistent pattern with regard to the respective p53 mutational status became evident. The results obtained in these breast carcinoma cell lines indicate that no clear-cut linear relationship exists between the p53 mutational status and the extent of its respective mRNA and protein expression. Therefore, direct DNA analyses and functional assays remain the only methods for the reliable detection of p53 mutations.

The time interval from surgery to start of chemotherapy significantly impacts prognosis in patients with advanced serous ovarian carcinoma — Analysis of patient data in the prospective OVCAD study

OBJECTIVE Cytoreductive surgery and platinum-based systemic therapy constitute the standard treatment of patients with advanced ovarian cancer. The aim of the present study was to evaluate whether the time interval from surgery to start of chemotherapy has an impact on clinical outcome. METHODS Data of 191 patients with advanced serous (FIGO III-IV) ovarian cancer from the prospective multicenter study OVCAD (OVarian CAncer Diagnosis) were analyzed. All patients underwent primary surgery followed by platinum-based chemotherapy. RESULTS The 25%, 50%, and 75% quartiles of intervals from surgery to start of chemotherapy were 22, 28, and 38 days, respectively (range, 4-158 days). Preoperative performance status (P<0.001), extent of surgery (P<0.001), and perioperative complications (P<0.001) correlated with intervals from surgery to initiation of chemotherapy. Timing of cytotoxic treatment [≤ 28 days versus >28 days; hazard ratio (HR) 1.73 (95% confidence interval 1.08-2.78), P=0.022], residual disease [HR 2.95 (95% confidence interval 1.87-4.67), P<0.001], and FIGO stage [HR 2.26 (95% confidence interval 1.41-3.64), P=0.001] were significant prognostic factors for overall survival in multivariate analysis. While the interval from surgery to start of chemotherapy did not possess prognostic significance in patients without postoperative residual disease (n=121), it significantly correlated with overall survival in patients with postoperative residual disease [n=70, HR 2.24 (95% confidence interval 1.08-4.66), P=0.031]. CONCLUSION Our findings suggest that delayed initiation of chemotherapy might compromise overall survival in patients with advanced serous ovarian cancer, especially when suboptimally debulked.

BRCA1 gene promoter methylation status in high-grade serous ovarian cancer patients - A study of the tumour Bank ovarian cancer (TOC) and ovarian cancer diagnosis consortium (OVCAD)

BACKGROUND Mutations in BRCA1/2 genes are involved in the pathogenesis of breast and ovarian cancer. Inactivation of these genes can also be mediated by hypermethylation of CpGs in the promoter regions. Aim of this study was to analyse the clinical impact of BRCA1 promoter gene methylation status in a homogenous cohort of high-grade serous ovarian cancer (HGSOC) patients. METHODS The cohort included 257 primary HGSOC patients treated by cytoreduction and platinum-based chemotherapy. DNA was extracted from fresh frozen tissue samples. BRCA1 gene promoter methylation rate was assessed using polymerase chain reaction (PCR). RESULTS 14.8% of patients presented hypermethylation within a selected region of the BRCA1 promoter. The rate of hypermethylation was significantly higher in younger patients (20.8% hypermethylation in the age group ⩽ 58 years versus 8.7% hypermethylation in the age group >58 years; p = 0.008). Optimal tumour debulking could be reached in 63% of patients, without significant differences in the extent of residual disease with respect to the methylation status. No impact of BRCA1 gene promoter methylation status on progression free- and overall-survival rates was found. No significant differences within BRCA1 promoter methylation status between primary and metastatic tissue could be observed. These results on BRCA1 promoter methylation status were also confirmed in a subgroup of 107 patients found negative for BRCA1 exon 11 mutations. CONCLUSIONS Our data suggest that BRCA1 methylation determines the earlier onset of HGSOC. Furthermore our study supports the idea that BRCAness is not only due to mutations but also to epigenetic changes in BRCA1 promoter gene.