Gulnur Guler

MicroRNA-29 family reverts aberrant methylation in lung cancer by targeting DNA methyltransferases 3A and 3B

MicroRNAs (miRNAs) are small, noncoding RNAs that regulate expression of many genes. Recent studies suggest roles of miRNAs in carcinogenesis. We and others have shown that expression profiles of miRNAs are different in lung cancer vs. normal lung, although the significance of this aberrant expression is poorly understood. Among the reported down-regulated miRNAs in lung cancer, the miRNA (miR)-29 family (29a, 29b, and 29c) has intriguing complementarities to the 3′-UTRs of DNA methyltransferase (DNMT)3A and -3B (de novo methyltransferases), two key enzymes involved in DNA methylation, that are frequently up-regulated in lung cancer and associated with poor prognosis. We investigated whether miR-29s could target DNMT3A and -B and whether restoration of miR-29s could normalize aberrant patterns of methylation in non-small-cell lung cancer. Here we show that expression of miR-29s is inversely correlated to DNMT3A and -3B in lung cancer tissues, and that miR-29s directly target both DNMT3A and -3B. The enforced expression of miR-29s in lung cancer cell lines restores normal patterns of DNA methylation, induces reexpression of methylation-silenced tumor suppressor genes, such as FHIT and WWOX, and inhibits tumorigenicity in vitro and in vivo. These findings support a role of miR-29s in epigenetic normalization of NSCLC, providing a rationale for the development of miRNA-based strategies for the treatment of lung cancer.

Fragile genes as biomarkers: epigenetic control of WWOX and FHIT in lung, breast and bladder cancer.

This study aimed to (a) determine if DNA methylation is a mechanism of WWOX (WW domain containing oxidoreductase) and FHIT (fragile histidine triad) inactivation in lung, breast and bladder cancers; (b) examine distinct methylation patterns in neoplastic and adjacent tissues and (c) seek correlation of methylation patterns with disease status. Protein expression was detected by immunohistochemistry, and methylation status by methylation-specific PCR (MSP) and sequencing, in lung squamous cell carcinomas and adjacent tissues, invasive breast carcinomas, adjacent tissues and normal mammary tissues and bladder transitional cell carcinomas. Wwox and Fhit expression was reduced in cancers in association with hypermethylation. Differential patterns of WWOX and FHIT methylation were observed in neoplastic vs adjacent non-neoplastic tissues, suggesting that targeted MSP amplification could be useful in following treatment or prevention protocols. WWOX promoter MSP differentiates DNA of lung cancer from DNA of adjacent lung tissue. WWOX and FHIT promoter methylation is detected in tissue adjacent to breast cancer and WWOX exon 1 MSP distinguishes breast cancer DNA from DNA of adjacent and normal tissue. Differential methylation in cancerous vs adjacent tissues suggests that WWOX and FHIT hypermethylation analyses could enrich a panel of DNA methylation markers.

Concordant loss of fragile gene expression early in breast cancer development

The FHIT and WWOX genes encompass the FRA3B and FRA16D fragile sites at chromosomes 3p14.2 and 16q23.3, respectively. Reduced Fhit and Wwox expression has been reported in approximately two‐thirds of invasive breast tumors. Expression of these fragile gene products, as well as ErbB2 and p53, were evaluated immunohistochemically in 44 pure and 31 adjacent‐to‐invasive ductal carcinoma in‐situ (DCIS) cases. Reduced Fhit and Wwox expression were observed in (i) 70% and 68% of pure DCIS; (ii) 52% and 55% of DCIS adjacent‐to‐invasive tumor cases; and (iii) 20% and 50% of adjacent normal tissue in pure DCIS cases. Reduced Wwox expression in adjacent normal tissue was observed in 30% of cases in the DCIS adjacent‐to‐invasive group. Reduced Fhit and Wwox expression was observed in 61% of adjoining invasive tumors. In all normal, pure DCIS, and DCIS adjacent‐to‐invasive lesions, Fhit and Wwox expression was positively associated (P = 0.034, P = 0.042, P = 0.004, respectively) and in the invasive component there was a positive trend toward association (P = 0.075). Fhit and Wwox were more frequently reduced in high‐grade lesions in the DCIS adjacent‐to‐invasive (P = 0.025, P = 0.004, respectively). In the pure DCIS group, there was a statistically significant negative association between Fhit and ErbB2 expression in DCIS (P = 0.035). In summary, reduced Fhit and Wwox expression in in‐situ breast cancer was associated, which may contribute to the high‐grade DCIS–invasive tumor pathway.

Wwox and Ap2γ Expression Levels Predict Tamoxifen Response

Purpose: Assessment of expression levels of Wwox, Wwox-interacting proteins Ap2α, Ap2γ, and ErbB4, the Ap2γ transcriptional target protein Her2, and the possible Ap2α transcriptional target PrkaRIα, in breast cancers, to determine their roles in tamoxifen resistance. The hypothesis was that sequestration of Wwox interactors in the cytoplasm might control tamoxifen response. Experimental Design: Tissue sections from 51 tamoxifen-sensitive and 38 tamoxifen-resistant, estrogen receptor α–positive breast cancers were stained for the above proteins, as well as progesterone receptor (PR). The relation of tamoxifen resistance and other clinical features, with level of expression of these proteins, and pairwise correlations among various immunohistochemical markers were determined. Results: Menopausal status, tumor, node, and stage, loss of PR, lost or reduced expression of Wwox, and high level of expression of PrkaRIα, Ap2γ, and Her2 were significantly correlated with tamoxifen resistance. In multivariate analysis, Wwox, PrkaRIα, Ap2γ, and ErbB4 were found to be independent markers of tamoxifen resistance. Reduced Wwox expression was better than PR in prediction of resistance, especially in high-risk patients, and nuclear Ap2γ expression was better than Her2, especially in low-risk patients. Conclusion: The results illustrate the complex relationships among the marker proteins assessed in this in vivo study and suggest new markers for prediction of response to tamoxifen treatment as well as possible new targets for treatment of breast cancer. Wwox and Ap2γ emerge as new biomarkers that may be superior to PR and Her2 in predicting tamoxifen response.

Fragile histidine triad protein, WW domain-containing oxidoreductase protein Wwox, and activator protein 2γ expression levels correlate with basal phenotype in breast cancer

The expression of fragile histidine triad protein (Fhit) and WW domain‐containing oxidoreductase protein (Wwox), tumor suppressors that are encoded by fragile (FRA) loci FRA3B and FRA16D, are lost concordantly in breast cancers. In the current study, the authors examined correlations among Fhit, Wwox, the activator protein 2 transcription factors AP2α and AP2γ, cytokeratins 5 and 6 (CK5/6), epidermal growth factor receptor (EGFR), estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER‐2) and their associations with breast cancer phenotypes.

Aberrant expression of DNA damage response proteins is associated with breast cancer subtype and clinical features

Landmark studies of the status of DNA damage checkpoints and associated repair functions in preneoplastic and neoplastic cells has focused attention on importance of these pathways in cancer development, and inhibitors of repair pathways are in clinical trials for treatment of triple negative breast cancer. Cancer heterogeneity suggests that specific cancer subtypes will have distinct mechanisms of DNA damage survival, dependent on biological context. In this study, status of DNA damage response (DDR)-associated proteins was examined in breast cancer subtypes in association with clinical features; 479 breast cancers were examined for expression of DDR proteins γH2AX, BRCA1, pChk2, and p53, DNA damage-sensitive tumor suppressors Fhit and Wwox, and Wwox-interacting proteins Ap2α, Ap2γ, ErbB4, and correlations among proteins, tumor subtypes, and clinical features were assessed. In a multivariable model, triple negative cancers showed significantly reduced Fhit and Wwox, increased p53 and Ap2γ protein expression, and were significantly more likely than other subtype tumors to exhibit aberrant expression of two or more DDR-associated proteins. Disease-free survival was associated with subtype, Fhit and membrane ErbB4 expression level and aberrant expression of multiple DDR-associated proteins. These results suggest that definition of specific DNA repair and checkpoint defects in subgroups of triple negative cancer might identify new treatment targets. Expression of Wwox and its interactor, ErbB4, was highly significantly reduced in metastatic tissues vs. matched primary tissues, suggesting that Wwox signal pathway loss contributes to lymph node metastasis, perhaps by allowing survival of tumor cells that have detached from basement membranes, as proposed for the role of Wwox in ovarian cancer spread.

EGFR expression and gene copy number in triple-negative breast carcinoma

Most basal-like breast carcinomas are estrogen receptor negative, progesterone receptor negative, and cerb-B2/HER-2/neu negative--the so-called triple-negative breast carcinomas--with high epidermal growth factor receptor (EGFR) expression, which makes EGFR a target of treatment. We evaluated EGFR expression by immunohistochemistry (IHC) with two different clones (EGFR.31G7 and EGFR.25) and gene copy number by fluorescence in situ hybridization (FISH) with Locus specific identifier EGFR/CEP 7 dual probe in 62 triple-negative breast carcinomas. Any complete or incomplete membranous and/or cytoplasmic expression was regarded as IHC positive. Cases showing gene amplification (a ratio of EGFR gene to chromosome 7 of ≥ 2 or 15 copies per cell in ≥ 10% of cells) and high polysomy (≥ 4 copies in ≥ 40% of cells) were considered FISH po sitive. We detected EGFR.31G7 positivity in 38 of 62 cases (61.4%), which was composed of 12 of 62 (19.4%) cytoplasmic, 14 of 62 (22.6%) incomplete membranous, and 12 of 62 (19.4%) complete membranous staining. Among 38 of 49 (77.6%) EGFR.25-positive cases, 7 of 49 (14.3%) exhibited cytoplasmic, 10 of 49 (20.4%) exhibited incomplete membranous, and 21 of 49 (42.9%) exhibited complete membranous staining pattern. Ten of 62 (16.1%) FISH-positive cases were identified; 1 of 62 (1.6%) showed amplification, and the rest showed high polysomy. All FISH-positive cases were also found to be IHC positive (P = 0.01) by both EGFR clones. The amplified case displayed strong complete membranous staining with both clones. Among the high polysomic cases; 4 of 9 (44.4%) incomplete membranous, 4 of 9 (44.4%) complete membranous and 1 of 9 (11.1%) cytoplasmic expression of EGFR.31G7, and 6 of 8 (75%) complete membranous and 2 of 6 (25%) cytoplasmic expression of EGFR.25 were detected. Here, we report that membranous EGFR expression is associated with increased gene copy number (P = 0.035 for EGFR.31G7 and P = 0.026 for EGFR.25 clone). Because the markers to predict anti-EGFR treatment response in other system tumors such as EGFR mutation and amplification seem to be rare events in breast cancer, membranous staining pattern of EGFR might be the best way to decide the patient eligibility for anti-EGFR therapy.

Androgen receptor status is a prognostic marker in non-basal triple negative breast cancers and determines novel therapeutic options.

Triple negative breast cancers are a heterogeneous group of tumors characterized by poor patient survival and lack of targeted therapeutics. Androgen receptor has been associated with triple negative breast cancer pathogenesis, but its role in the different subtypes has not been clearly defined. We examined androgen receptor protein expression by immunohistochemical analysis in 678 breast cancers, including 396 triple negative cancers. Fifty matched lymph node metastases were also examined. Association of expression status with clinical (race, survival) and pathological (basal, non-basal subtype, stage, grade) features was also evaluated. In 160 triple negative breast cancers, mRNA microarray expression profiling was performed, and differences according to androgen receptor status were analyzed. In triple negative cancers the percentage of androgen receptor positive cases was lower (24.8% vs 81.6% of non-triple negative cases), especially in African American women (16.7% vs 25.5% of cancers of white women). No significant difference in androgen receptor expression was observed in primary tumors vs matched metastatic lesions. Positive androgen receptor immunoreactivity was inversely correlated with tumor grade (p<0.01) and associated with better overall patient survival (p = 0.032) in the non-basal triple negative cancer group. In the microarray study, expression of three genes (HER4, TNFSF10, CDK6) showed significant deregulation in association with androgen receptor status; eg CDK6, a novel therapeutic target in triple negative cancers, showed significantly higher expression level in androgen receptor negative cases (p<0.01). These findings confirm the prognostic impact of androgen receptor expression in non-basal triple negative breast cancers, and suggest targeting of new androgen receptor-related molecular pathways in patients with these cancers.

CpG methylation in the Fhit regulatory region: relation to Fhit expression in murine tumors.

To determine if: (1) 5′ CpG island methylation is related to Fhit inactivation; (2) there are tumor or carcinogen-specific methylation patterns, we examined 35 CpG sites in the promoter, exon and intron 1 of the mouse Fhit gene. In primary tumors of lung, urinary bladder and tongue, induced by different carcinogens, 15–35% of sites were methylated, with specific methylation patterns associated with each cancer type, suggesting cancer- or tissue-specific methylation patterns. The methylation patterns were associated with reduced Fhit expression, as determined by immunohistochemical analyses. Methylation of rat Fhit 5′ CpGs in mammary adenocarcinomas, detected by methylation specific PCR amplification, also correlated with reduced gene expression. Thus, there was an overall association between promoter/exon 1 methylation and decreased Fhit expression. In contrast, in cancer-derived cell lines 70–95% of the CpG sites were methylated. This is the first detailed study of the relationship between Fhit 5′ CpG island methylation and Fhit expression in murine tumors, our main models for preclinical cancer studies, and provides evidence that loss of Fhit expression and methylation are correlated in these mouse models and these models will be useful to examine the complex relationships among gene expression, methylation patterns and organ specificity.

Low ERCC1 expression is associated with prolonged survival in patients with bladder cancer receiving platinum-based neoadjuvant chemotherapy

PURPOSE Excision repair cross-complementation group 1 enzyme (ERCC1) plays a key role in the removal of platinum induced DNA adducts and cisplatin resistance. Prognostic role of ERCC1 expression in the neoadjuvant setting in bladder cancer has not been reported before. We evaluated the prognostic role of ERCC1 expression in bladder cancer receiving platinum-based neoadjuvant chemotherapy. MATERIALS AND METHODS Thirty-eight patients with muscle invasive bladder cancer who received neoadjuvant platinum-based chemotherapy were included. Clinical and histopathologic parameters along with immunohistochemical ERCC1 staining were examined and correlated with response rates and survival. RESULTS Pathologic complete response rates were similar between patients with low and high ERCC1 expression. Median disease-free survival (DFS) was 9.3 vs. 20.5 months (P = 0.186) and median overall survival (OS) was 9.3 vs. 26.7 months (P = 0.058) in patients with high ERCC1 expression compared with those with low expression, respectively. In multivariate Cox regression analysis: pathological complete response (pCR) after chemotherapy (hazard ratio (HR) 0.1, 95% CI 0.012-0.842, P = 0.034) and high ERCC1 expression (HR 3.7, 95% CI 1.2-11.2, P = 0.019) were significantly associated with DFS. Patient age (>60 vs. ≤ 60 years) (HR 3.4, 95% CI 1.2-9.4, P = 0.018), the presence of pCR (HR 0.11, 95% CI 0.014-0.981, P = 0.048) and high ERCC expression (HR 6.1, 95 CI 1.9-19.9, P = 0.002) were significantly associated with OS. CONCLUSIONS Our results showed that high ERCC1 expression was independently associated with shorter disease-free and overall survival in patients with bladder cancer who received neoadjuvant platinum-based chemotherapy. ERCC1 may represent a potential predictive marker for platinum-based treatment in bladder cancer.