Elisabeth Mueller-Holzner

Epigenetic stem cell signature in cancer

Embryonic stem cells rely on Polycomb group proteins to reversibly repress genes required for differentiation. We report that stem cell Polycomb group targets are up to 12-fold more likely to have cancer-specific promoter DNA hypermethylation than non-targets, supporting a stem cell origin of cancer in which reversible gene repression is replaced by permanent silencing, locking the cell into a perpetual state of self-renewal and thereby predisposing to subsequent malignant transformation.

Age-dependent DNA methylation of genes that are suppressed in stem cells is a hallmark of cancer

Polycomb group proteins (PCGs) are involved in repression of genes that are required for stem cell differentiation. Recently, it was shown that promoters of PCG target genes (PCGTs) are 12-fold more likely to be methylated in cancer than non-PCGTs. Age is the most important demographic risk factor for cancer, and we hypothesized that its carcinogenic potential may be referred by irreversibly stabilizing stem cell features. To test this, we analyzed the methylation status of over 27,000 CpGs mapping to promoters of approximately 14,000 genes in whole blood samples from 261 postmenopausal women. We demonstrate that stem cell PCGTs are far more likely to become methylated with age than non-targets (odds ratio = 5.3 [3.8-7.4], P < 10(-10)), independently of sex, tissue type, disease state, and methylation platform. We identified a specific subset of 69 PCGT CpGs that undergo hypermethylation with age and validated this methylation signature in seven independent data sets encompassing over 900 samples, including normal and cancer solid tissues and a population of bone marrow mesenchymal stem/stromal cells (P < 10(-5)). We find that the age-PCGT methylation signature is present in preneoplastic conditions and may drive gene expression changes associated with carcinogenesis. These findings shed substantial novel insights into the epigenetic effects of aging and support the view that age may predispose to malignant transformation by irreversibly stabilizing stem cell features.

Circulating Tumor-Specific DNA: A Marker for Monitoring Efficacy of Adjuvant Therapy in Cancer Patients

Adjuvant systemic therapy (a strategy that targets potential disseminated tumor cells after complete removal of the tumor) has clearly improved survival of patients with cancer. To date, no tool is available to monitor efficacy of these therapies, unless distant metastases arise, a situation that unavoidably leads to death. We analyzed RASSF1A DNA methylation in pretherapeutic sera and serum samples collected 1 year after surgery from 148 patients with breast cancer who were receiving adjuvant tamoxifen; 19.6% and 22.3% of patients with breast cancer showed RASSF1A DNA methylation in their pretherapeutic and 1-year-after serum samples, respectively. RASSF1A methylation 1 year after primary surgery (and during adjuvant tamoxifen therapy) was an independent predictor of poor outcome, with a relative risk (95% confidence interval) for relapse of 5.1 (1.3-19.8) and for death of 6.9 (1.9-25.9). Measurement of serum DNA methylation allows adjuvant systemic treatment to be monitored for efficacy: disappearance of RASSF1A DNA methylation in serum throughout treatment with tamoxifen indicates a response, whereas persistence or new appearance means resistance to adjuvant tamoxifen treatment. It remains to be seen whether modifications made in adjuvant therapeutic strategies based on detection of circulating nucleic acids will improve survival as well as quality of life.

Mutation of hCDC4 Leads to Cell Cycle Deregulation of Cyclin E in Cancer

hCDC4, the gene that encodes the F-box protein responsible for targeting cyclin E for ubiquitin-mediated proteolysis, has been found to be mutated in a number of primary cancers and cancer-derived cell lines. We have observed that functional inactivation of hCDC4 does not necessarily correlate with elevated levels of cyclin E in tumors. Here we show, however, that hCDC4 mutation in primary tumors correlates strongly with loss of cell cycle regulation of cyclin E. Similarly, a breast carcinoma-derived cell line mutated for hCDC4 exhibits cell cycle deregulation of cyclin E, but periodic expression is restored by reintroducing hCDC4 via retroviral transduction. Conversely, small interfering RNA-mediated silencing of hCdc4 deregulates cyclin E with respect to the cell cycle. These results indicate that hCdc4 function is an absolute prerequisite for cell cycle regulation of cyclin E levels, and loss of hCdc4 function is sufficient to deregulate cyclin E.

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.

HOXA11 DNA methylation--a novel prognostic biomarker in ovarian cancer.

Epigenetic alterations play a major role in cancer. Recently we reported that stem cell Polycomb group targets (PcGTs) are up to 12‐fold more likely to have cancer‐specific promoter DNA hypermethylation than nontargets. To identify potential, prognostic DNA methylation markers in ovarian cancer we analyzed the DNA methylation at 71 different loci in 22 ovarian cancers and 18 non‐neoplastic ovarian specimens by means of a quantitative, real‐time PCR‐based technique (MethyLight). We identified DNA methylation of HOXA10 and HOXA11, both of them PcGTs, to be the best discriminators between cancer and non‐neoplastic tissue. In an independent set consisting of 92 ovarian cancer specimens further analysis demonstrated that HOXA11 DNA methylation is (i) strongly associated with the residual tumor after cytoreductive surgery and (ii) is a marker indicating poor prognosis. HOXA11 DNA methylation was independently associated with poor outcome [relative risk for death 3.4 (95% CI 1.2–9.9; p = 0.03)]. These findings support the view that the technical inability to optimally cytoreduce ovarian cancer is associated with particular molecular alterations in the tumor which per se define a subgroup of patients with poor outcome.

Immunohistochemical determination of HER2 expression in breast cancer from core biopsy specimens: a reliable predictor of HER2 status of the whole tumor.

HER2 overexpression in breast cancer is associated with a poor prognosis, resistance to endocrine therapy and chemosensitivity to anthracyclines and paclitaxel. Moreover, trastuzumab (HerceptinR) shows therapeutic benefit in patients with HER2 overexpressing tumors. Therefore, knowledge of the pretherapeutical HER2 status allows an optimal selection of patients for treatment. In addition to a definitive histological diagnosis, core biopsies of tumors offer the opportunity to evaluate the HER2 status preoperatively. In 64 patients with invasive breast cancer, sections of core biopsies and of the subsequently removed whole tumor were investigated immuno-histochemically with the DAKO HercepTestTM. Fifteen tumors (23%) revealed HER2 overexpression, and 44 tumors (69%) were negative in both, the core biopsy and the whole tumor sections. Two core biopsies were negative whereas the corresponding final specimen was 2+ positive. In 3 cases weak overexpression was observed in the core biopsy, but the whole tumor was negative. The overall concordance of the results achieved at core biopsy and whole tumor sections was 92% κ=0.8). A negative HER2 result on core biopsy was never associated with a score 3+ tumor specimen nor was there a case of negative whole tumor specimen with a preceding 3+ score in the biopsy. If one demands the highest degree of overexpression (3+), 100% of our study patients would have been selected correctly using the results on core biopsy alone. We thus conclude, that the immunohistochemical investigation of core biopsies offers the opportunity for a valid preoperative estimation of HER2 overexpression.

Cyclin E dysregulation and chromosomal instability in endometrial cancer.

Deregulation of cyclin E, an activator of cyclin-dependent kinase 2 (Cdk2), has been associated with a broad spectrum of human malignancies. Yet the mechanism linking abnormal cyclin E expression to carcinogenesis is largely unknown. The gene encoding the F-box protein hCdc4, a key component of the molecular machinery that targets cyclin E for degradation, is frequently mutated in endometrial cancer, leading to deregulation of cyclin E expression. Here we show that hCDC4 gene mutation and hyperphosphorylation of cyclin E, a parameter that usually correlates with hCDC4 mutation, have a strong statistically significant association with polypoidy and aneuploidy in endometrial cancer. On the contrary, elevated expression of cyclin E by itself was not significantly correlated with polyploidy or aneuploidy when tumors of similar grade are evaluated. These data suggest that impairment of cell cycle regulated proteolysis of cyclin E may be linked to carcinogenesis by promoting genomic instability.

DNA ploidy, nuclear size, proliferation index and DNA-hypomethylation in ovarian cancer

OBJECTIVE The present study was undertaken to analyze the impact of epigenetic alterations with a main focus on nuclear area, aneuploidy, hyperploidy, and proliferation in 70 ovarian cancer specimens. METHODS Morphometric changes and somatic chromosomal ploidy status were assessed by Feulgen spectrophotometry. DNA-hypomethylation of LINE1 repeats was analyzed by means of MethyLight PCR, and methylation levels of satellite 2 (Sat2) and satellite alpha (Satα) DNA sequences in chromosome 1 were measured by Southern blot analysis. These parameters were analyzed with regard to correlations as well as to recurrence and survival. RESULTS We identified a significant association between LINE1 DNA-hypomethylation and patient age (p=0.029). Furthermore, LINE1 DNA-hypomethylation was positively correlated with the nuclear area (r=0.47; p<0.001) and the proliferation index (r=0.36; p<0.001). Univariate survival analysis showed that the nuclear area and LINE1 DNA-hypomethylation were prognostic factors for overall (p=0.015 and =0.006, respectively) and progression-free survival (p=0.020 and p=0.001 respectively), the percentage of aneuploidy only for overall survival (p=0.031). Subgroup survival analyses revealed that the prognostic value of these factors is strictly confined to mucinous cancers. In serous cancers no prognostic value could be pointed out for any analyzed parameter. Multivariate analysis of the entire cohort showed that the percentage of hyperploidy was an independent prognostic parameter for overall survival (p=0.003) and LINE1 DNA-hypomethylation for progression-free survival (p=0.03). In mucinous cancers nuclear area and LINE1 DNA-hypomethylation were found to be independent predictors of progression-free and overall survival. CONCLUSIONS In this study we identified the correlations between early cancer-associated genome DNA-hypomethylation, nuclear morphometric changes, somatic chromosomal ploidy status and the proliferation index. Prognostic relevance of nuclear area and LINE1 DNA-hypomethylation was revealed exclusively in mucinous ovarian cancers.

Methylated NEUROD1 Promoter is a Marker for Chemosensitivity in Breast Cancer

Purpose: Chemotherapy can be an integral component of the adjuvant management strategy for women with early stage breast cancer. To date, no tool is available to predict or monitor the efficacy of these therapies. The aim of this proof-of-principle study was to assess whether NEUROD1 DNA methylation is able to predict the response to neoadjuvant and adjuvant chemotherapy. Experimental Design: Recently, we showed that NEUROD1 DNA is differentially methylated in neoplastic versus nonneoplastic breast tissue samples. In this study, we used MethyLight and analyzed NEUROD1 methylation in (a) 74 breast cancer tissue samples, (b) two independent sets of pretreatment core biopsies of 23 (training set) and 21 (test set) neoadjuvantly treated breast cancer patients, and (c) pretherapeutic and posttherapeutic serum samples from 107 breast cancer patients treated with adjuvant chemotherapy. Results: High-grade tumors showed higher NEUROD1 methylation levels. Estrogen receptor–negative breast cancers with high NEUROD1 methylation were 10.8-fold more likely to respond with a complete pathologic response following neoadjuvant chemotherapy. Patients with positive serum pretreatment NEUROD1 methylation, which persisted after chemotherapy, indicated poor relapse-free and overall survival in univariate and multivariate analyses (relative risk for relapse, 6.2; 95% confidence interval, 1.6-24; P = 0.008, and relative risk for death, 14; 95% confidence interval, 1.6-120; P = 0.02). Conclusions: These data support the view that NEUROD1 methylation is a chemosensitivity marker in estrogen receptor–negative breast cancer.