Genotyping of stathmin and its association with clinical factors and survival in patients with ovarian cancer

Stathmin is closely correlated with the progression and prognosis of a number of types of human cancer. The present study analyzed the associations between genetic variations in the stathmin gene and clinical outcomes of ovarian cancer. A total of 178 patients with epithelial ovarian cancer were treated with cytoreductive surgery followed by platinum-based chemotherapy. DNA was extracted from fresh tumor samples obtained during surgery. A total of 32 DNA samples were selected randomly for resequencing of the stathmin gene. Tag single nucleotide polymorphisms (SNPs) were identified based on the haplotype model as analyzed by PolyPhred software. Direct sequencing was employed in the genotyping of stathmin in 178 cases. A total of 10 nucleotide variations in stathmin were identified, of which 3 high-frequency variations were known SNPs from databases and 7 were new variations with low frequencies. The tag SNPs rs159531 and rs11376635 were selected from the linkage disequilibrium block of the gene to genotype stathmin in 178 cases. The distribution of the rs159531 genotype in ovarian cancer was 52.8% C/C, 35.4% C/T and 11.2% T/T. The distribution of the rs11376635 genotype in ovarian cancer was 32.0% G/G, 48.3% G/-, 18.5% -/-. The main haplotypes calculated by phase2.0 software were 55.6% CG, 27.8% T-, 15.4% C- and 1.2% TG. However, no associations between the stathmin genotype or haplotype and the outcomes in patients with ovarian cancer were observed. The stathmin genotype and haplotype were not associated with the phenotype of patients with ovarian cancer.

Functional study of risk loci of stem cell-associated gene lin-28B and associations with disease survival outcomes in epithelial ovarian cancer

Several single-nucleotide polymorphisms (SNPs) of the stem cell-associated gene lin-28B have been identified in association with ovarian cancer and ovarian cancer-related risk factors. However, whether these SNPs are functional or might be potential biomarkers for ovarian cancer prognosis remains unknown. The purposes of this study were to investigate the functional relevance of the identified lin-28B SNPs, as well as the associations of genotype and phenotype with epithelial ovarian cancer (EOC) survival. We analyzed five SNPs and mRNA levels of lin-28B in 211 primary EOC tissues using Taqman(®) SNP genotyping assays and SYBR green-based real-time PCR, respectively. The RNA secondary structures at the region of a genome-wide association-identified intronic rs314276 were analyzed theoretically with mfold and experimentally with circular dichroism spectroscopy. We found that rs314276 was a cis-acting expression quantitative trait locus (eQTL) in both additive and dominant models, while rs7759938 and rs314277 were significant or of borderline significance in dominant models only. The rs314276 variant significantly affects RNA secondary structure. No SNPs alone were associated with patient survival. However, we found that among patients initially responding to chemotherapy, those with higher lin-28B expression had higher mortality risk (hazard ratio =3.27, 95% confidence interval: 1.63-6.56) and relapse risk (hazard ratio = 2.53, 95% confidence interval: 1.41-4.54) than those with lower expression, and these associations remained in multivariate analyses. These results suggest that rs314276 alters RNA secondary structure and thereby influences gene expression, and that lin-28B is a cancer stem cell-associated marker, which may be a pharmaceutical target in the management of EOC.

The zinc finger gene ZIC2 has features of an oncogene and its overexpression correlates strongly with the clinical course of epithelial ovarian cancer

PURPOSE

Epithelial ovarian tumors (EOT) are among the most lethal of malignancies in women. We have previously identified ZIC2 as expressed at a higher level in samples of a malignant form (MAL) of EOT than in samples of a form with low malignant potential (LMP). We have now investigated the role of ZIC2 in driving tumor growth and its association with clinical outcomes.

EXPERIMENTAL DESIGN

ZIC2 expression levels were analyzed in two independent tumor tissue collections of LMP and MAL. In vitro experiments aimed to test the role of ZIC2 as a transforming gene. Cox models were used to correlate ZIC2 expression with clinical endpoints.

RESULTS

ZIC2 expression was about 40-fold in terms of mRNA and about 17-fold in terms of protein in MAL (n = 193) versus LMP (n = 39) tumors. ZIC2 mRNA levels were high in MAL cell lines but undetectable in LMP cell lines. Overexpression of ZIC2 was localized to the nucleus. ZIC2 overexpression increases the growth rate and foci formation of NIH3T3 cells and stimulates anchorage-independent colony formation; downregulation of ZIC2 decreases the growth rate of MAL cell lines. Zinc finger domains 1 and 2 are required for transforming activity. In stage I MAL, ZIC2 expression was significantly associated with overall survival in both univariate (P = 0.046) and multivariate model (P = 0.049).

CONCLUSIONS

ZIC2, a transcription factor related to the sonic hedgehog pathway, is a strong discriminant between MAL and LMP tumors: it may be a major determinant of outcome of EOTs.

Randomized phase III study of erlotinib versus observation in patients with no evidence of disease progression after first-line platin-based chemotherapy for ovarian carcinoma: A GCIG and EORTC-GCG study

LBA5000

Background: The epidermal growth factor receptor (EGFR) has been found to be overexpressed in 55-98% of advanced epithelial ovarian cancer. This trial evaluated the efficacy of maintenance erlotinib, an EGFR tyrosine kinase inhibitor, after first-line chemotherapy. Methods: Eligible patients (pts) had high-risk FIGO stage I or stage II-IV epithelial ovarian, peritoneal or fallopian tube cancer and were not selected for EGFR expression. All patients underwent first line therapy (6-9 cycles of 3-weekly platinum-based chemotherapy (CT)) and showed no signs of progression at the end of CT. Patients were randomised to maintenance erlotinib 150 mg daily for 2 years or observation. Primary endpoint was progression-free survival (PFS) by RECIST in combination with GCIG CA125 criteria. The final design provided 80% power to detect a PFS hazard ratio (HR) of 0.80 with 2-sided log-rank test at 5% after 632 events in 830 patients. Stratifications factors were stage, institution, age, response to and type of first-line CT. Immunohistochemistry (IHC) and FISH for EGFR, and EGFR mutation analyses were performed in 330 patients. The study was registered as NCT00263822 and EudraCT number 2004-004333-34. Results: Between Oct 2005 and Feb 2008, 835 pts were randomised by 125 institutions from 10 countries. The most important baseline characteristics, PFS and OS are summarized in the table. Median follow-up was 51 months. 25% of the patients stopped erlotinib due to side effects (of these 67% due to rash). The predictive value of IHC and FISH for EGFR, and EGFR mutations are being evaluated and will be presented at the meeting. Conclusions: In the overall study populationmaintenance erlotinib after first-line treatment in ovarian cancer did not improve progression-free or overall survival. [Table: see text]

Randomized phase III study of erlotinib versus observation in patients with no evidence of disease progression after first-line platin-based chemotherapy for ovarian carcinoma: A GCIG and EORTC-GCG study

LBA5000

The full, final text of this abstract will be available at abstract.asco.org at 12:01 AM (EDT) on Saturday, June 2, 2012, and in the Annual Meeting Proceedings online supplement to the June 20, 2012, issue of Journal of Clinical Oncology. Onsite at the Meeting, this abstract will be printed in the Saturday edition of ASCO Daily News.

Abstract 3655: Stem cell-associated gene Lin-28B genotype and phenotype in epithelial ovarian cancer and their associations with disease survival outcomes

Several single nucleotide polymorphisms (SNPs) in lin-28B, a gene encoding RNA binding protein that represses miRNA let-7 maturation and acts as an oncogene, were found in the genome-wide association studies (GWAS), to be associated with the risk of ovarian cancer and cancer-related risk factors such as age at menarche, body mass index (BMI) and height. However, whether these SNPs are functionally important and can serve as prognostic markers in ovarian cancer remain unknown. The purposes of this study were to investigate the genotype-phenotype relationship in lin-28B and their associations with patient survivals in epithelial ovarian cancer. To achieve these purposes, we analyzed five lin-28B SNPs using Taqman® assays and lin-28B expression using SYBR green-based qPCR in tumor samples collected from 211 patients diagnosed with primary epithelial ovarian cancer. Wilcoxon rank sum test was performed to analyze cis-regulatory eQTL; Kaplan-Meir survival curves and Cox proportional hazards regression models were used to assess the associations of lin-28B SNPs and expression with the risks of relapse and death. The results showed that three SNPs (rs314276, rs314277 and rs7759938) were associated with lin-28B mRNA levels. Using mfold, rs314276 and rs314277 were predicted to affect the secondary structures of lin-28B mRNA. SNP rs7759938 is located at the 500 bp downstream of the region with H3K4Me1 (an enhancer marker) enrichment restricted to stem cells. However, these SNPs were not significantly associated with clinical and pathological parameters including disease stage, tumor grade, histological types, residual tumor size, and debulking results. No SNPs alone were related to patient survivals. Among patients initially responding to chemotherapy, those with high lin-28B expression had higher risks of death (hazard ratio (HR)=3.27, 95% CI: 1.63-6.56), and relapse (HR=2.53, 95% CI: 1.41-4.54) than those with low one. After adjustment for patient age at surgery, disease stage, tumor grade, histological types and residual tumor size, the associations were still statistically significant. These findings suggest that 3 of the GWAS-hit SNPs in lin-28B may affect gene expression, but these SNPs are not associated with ovarian cancer survival. The results also indicate that lin-28B may affect the outcome of chemotherapy.

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 3655. doi:1538-7445.AM2012-3655

Variation in gynecological oncology follow-up practice: attributable to cancer centers or to patient characteristics? A Piedmont Regional Oncology Network Study

AIMS AND BACKGROUND

Although guidelines recommend minimalist follow-up, there is wide variability in gynecological oncology practice. The aims of this study were to describe between-center differences in the follow-up of endometrial, ovarian, and uterine cervical cancer; to identify the determinants of test prescription; to estimate the related costs; and to assess the weight of center habits and patient characteristics as sources of unexplained variability.

METHODS AND STUDY DESIGN

The medical records of patients treated between August 2004 and July 2005 for gynecological malignancies and followed up for the detection of recurrent disease were retrospectively collected from 29 centers of the Piedmont Oncology Network. Multivariate multilevel analyses were performed to study the determinants of test prescription and costs.

RESULTS

Analyses were performed on 351 patients (median follow-up: 578 days). The unexplained variability in computed tomography prescriptions (26%), ultrasound prescriptions (17%), and total cost of follow-up (15%) can be attributed to center habits, independenty of the clinical characteristics of the patients.

CONCLUSIONS

Much of the unexplained variability in the follow-up for gynecological malignancies is attributable to different habits of centers belonging to a cancer network. These results prompted us to design a multicenter randomized controlled trial to compare minimalist versus intensive follow-up programs in endometrial cancer.

Lin-28 homologue A (LIN28A) promotes cell cycle progression via regulation of cyclin-dependent kinase 2 (CDK2), cyclin D1 (CCND1), and cell division cycle 25 homolog A (CDC25A) expression in cancer

The RNA-binding protein LIN28A regulates the translation and stability of a large number of mRNAs as well as the biogenesis of certain miRNAs in embryonic stem cells and developing tissues. Increasing evidence indicates that LIN28A functions as an oncogene promoting cancer cell growth. However, little is known about its molecular mechanism of cell cycle regulation in cancer. Using tissue microarrays, we found that strong LIN28A expression was reactivated in about 10% (7.1-17.1%) of epithelial tumors (six tumor types, n = 369). Both in vitro and in vivo experiments demonstrate that LIN28A promotes cell cycle progression in cancer cells. Genome-wide RNA-IP-chip experiments indicate that LIN28A binds to thousands of mRNAs, including a large group of cell cycle regulatory mRNAs in cancer and embryonic stem cells. Furthermore, the ability of LIN28A to stimulate translation of LIN28A-binding mRNAs, such as CDK2, was validated in vitro and in vivo. Finally, using a combined gene expression microarray and bioinformatics approach, we found that LIN28A also regulates CCND1 and CDC25A expression and that this is mediated by inhibiting the biogenesis of let-7 miRNA. Taken together, these results demonstrate that LIN28A is reactivated in about 10% of epithelial tumors and promotes cell cycle progression by regulation of both mRNA translation (let-7-independent) and miRNA biogenesis (let-7-dependent).

PDCD6 is an independent predictor of progression free survival in epithelial ovarian cancer

Background

Programmed cell death 6 (PDCD6) beside its known proapoptotic functions may be a player in survival pathways in cancer. The purpose of this study is to further explore the roles of PDCD6 in epithelial ovarian cancer.

Methods

Lentiviral vector with shRNA for PDCD6 was used to investigate the effects of PDCD6 knockdown on cell growth, cell cycle, apoptosis and motility in ovarian cancer cells. Two hundred twelve epithelial ovarian cancer tissues were analyzed for mRNA expression of PDCD6 using RT-PCR. Associations of its expression with clinical pathological factors, progression free and overall survival were evaluated.

Results

PDCD6 is highly expressed in metastatic ovarian cancer cells and positively regulates cell migration and invasion. Significantly, the level of PDCD6 expression in epithelial ovarian cancer correlates with clinical progression. Patients with medium or high levels of PDCD6 mRNA were at higher risk for disease progression, compared to those with low levels (HR, 1.29; P = 0.024 for medium levels; and HR, 1.57; P = 0.045 for high levels) after adjusting for age, disease stage, tumor grade, histologic type and residual tumor size. Kaplan-Meier survival analysis demonstrated similar results. However, no association was found between PDCD6 expression and overall survival.

Conclusions

PDCD6 seems to play an important role in ovarian cancer progression and it may be an independent predictor of progression free survival in epithelial ovarian cancer. Further studies are needed to more completely elucidate the molecular mechanisms of PDCD6 involve in ovarian cancer progression.

A KRAS variant is a biomarker of poor outcome, platinum chemotherapy resistance and a potential target for therapy in ovarian cancer

Germ-line variants in the 3′ untranslated region (3′UTR) of cancer genes disrupting microRNA (miRNA) regulation have recently been associated with cancer risk. A variant in the 3′UTR of the KRAS oncogene, referred to as the KRAS-variant, is associated with both cancer risk and altered tumor biology. Here we test the hypothesis that the KRAS-variant can act as a biomarker of outcome in epithelial ovarian cancer (EOC), and investigate the cause of altered outcome in KRAS-variant positive EOC patients. As this variant appears to be associated with tumor biology, we additionally test the hypothesis that this variant can be directly targeted to impact cell survival.

EOC patients with complete clinical data were genotyped for the KRAS-variant and analyzed for outcome (n=536), response to neoadjuvant chemotherapy (n=125), and platinum resistance (n=306). Outcome was separately analyzed for women with known BRCA mutations (n=79). Gene expression was analyzed on a subset of tumors with available tissue. Cell lines were employed to confirm altered sensitivity to chemotherapy with the KRAS-variant. The KRAS-variant was directly targeted through siRNA/miRNA oligonucleotides in cell lines and survival was measured.

Post-menopausal EOC patients with the KRAS-variant were significantly more likely to die of ovarian cancer by multivariate analysis (HR=1.67, 95% CI=1.09–2.57, p=0.019, n=279). Possibly explaining this finding, EOC patients with the KRAS-variant were significantly more likely to be platinum resistant (OR=3.18, CI=1.31–7.72, p=0.0106, n=291). Additionally, direct targeting of the KRAS-variant led to a significant reduction in EOC cell growth and survival in vitro.

These findings confirm the importance of the KRAS-variant in EOC, and indicate that the KRAS-variant is a biomarker of poor outcome in EOC likely due to platinum resistance. In addition, this work supports the hypothesis that these tumors have continued dependence on such 3′UTR lesions, and that direct targeting may be a viable future treatment approach.

A combined array-based comparative genomic hybridization and functional library screening approach identifies mir-30d as an oncomir in cancer

Oncomirs are microRNAs (miRNA) that acts as oncogenes or tumor suppressor genes. Efficient identification of oncomirs remains a challenge. Here we report a novel, clinically guided genetic screening approach for the identification of oncomirs, identifying mir-30d through this strategy. mir-30d regulates tumor cell proliferation, apoptosis, senescence, and migration. The chromosomal locus harboring mir-30d was amplified in more than 30% of multiple types of human solid tumors (n = 1,283). Importantly, higher levels of mir-30d expression were associated significantly with poor clinical outcomes in ovarian cancer patients (n = 330, P = 0.0016). Mechanistic investigations suggested that mir-30d regulates a large number of cancer-associated genes, including the apoptotic caspase CASP3. The guided genetic screening approach validated by this study offers a powerful tool to identify oncomirs that may have utility as biomarkers or targets for drug development.

Novel surface targets and serum biomarkers from the ovarian cancer vasculature

The molecular phenotype of tumor vasculature is different from normal vasculature, offering new opportunities for diagnosis and therapy of cancer, but the identification of tumor-restricted targets remains a challenge. We investigated 13 tumor vascular markers (TVMs) from 50 candidates identified through expression profiling of ovarian cancer vascular cells and selected to be either transmembrane or secreted, and to be either absent or expressed at low levels in normal tissues while overexpressed in tumors, based on analysis of 1,110 normal and tumor tissues from publicly available Affymetrix microarray data. Tumor-specific expression of each TVM was confirmed at the protein level in tumor tissue and/or in serum. Among the 13 TVMs, 11 were expressed on tumor vascular endothelium; the remaining 2 TVMs were expressed by tumor leukocytes. Our results demonstrate that certain transmembrane TVMs such as ADAM12 and CDCP1 are selectively expressed in tumor vasculature and represent promising targets for vascular imaging or anti-vascular therapy of epithelial ovarian cancer, while secreted or shed molecules such as TNFRSF21/DR6 can function as serum biomarkers. We have identified novel tumor-specific vasculature markers which appear promising for cancer serum diagnostics, molecular imaging and/or therapeutic targeting applications and warrant further clinical development.

Telomerase expression and telomere length in breast cancer and their associations with adjuvant treatment and disease outcome

Introduction

Telomere length plays important roles in maintaining genome stability and regulating cell replication and death. Telomerase has functions not only to extend telomere length but also to repair DNA damage. Studies have shown that telomerase may increase cancer cell resistance to DNA-damaging anticancer agents; tamoxifen may suppress telomerase expression in breast cancer cells. This study aimed to investigate the role of telomere length and telomerase activity in breast cancer prognosis.

Methods

qPCR and qRT-PCR were used to analyze telomere length and telomerase expression, respectively, in tumor samples of 348 breast cancer patients. Cox regression analysis was performed to examine telomere length and telomerase expression in association with disease-free survival and cause-specific mortality.

Results

Telomere length had no relation to tumor features or disease outcomes. Telomerase expression was detected in 53% of tumors. Larger tumors or aggressive disease were more likely to have telomerase expression. Among patients treated with chemotherapy, high telomerase was found to be associated with increased risk of death (hazard ratio (HR) = 3.15; 95% CI: 1.34 to 7.40) and disease recurrence (HR = 2.04; 95% CI: 0.96 to 4.30) regardless of patient age, disease stage, tumor grade, histological type or hormone receptor status. Patients treated with endocrine therapy had different results regarding telomerase: high telomerase appeared to be associated with better survival outcomes. Telomerase expression made no survival difference in patients who received both chemotherapy and endocrine therapy.

Conclusions

Overall, telomerase expression was not associated with disease outcome, but this finding may be masked by adjuvant treatment. Patients with high telomerase expression responded poorly to chemotherapy in terms of disease-free and overall survival, but fared better if treated with endocrine therapy.

MicroRNA let-7a: a potential marker for selection of paclitaxel in ovarian cancer management

OBJECTIVES

Let-7 is a family of small non-coding RNAs regulating the expression of many genes that control important cellular activities. Let-7 is shown in vitro to sensitize cancer cells to platinum, but induce ovarian cancer resistance to paclitaxel. This study aims to investigate the effect of let-7a expression on survival outcomes of epithelial ovarian cancer (EOC) patients treated with different chemotherapy.

METHODS

Let-7a expression was measured with qRT-PCR in ovarian tumors of 178 EOC patients who received platinum-based chemotherapy with and without paclitaxel after surgery. Survival analysis was performed to assess the effects of let-7a and chemotherapy on disease outcomes.

RESULTS

Let-7a expression was detectable in the EOC samples, but the expression was not associated with disease stage, tumor grade, histology and debulking results. Patients who responded to platinum with paclitaxel had significantly lower let-7a than those who did not. Survival analyses showed that patients with high let-7a had better survival compared to those with low let-7a when they were treated with platinum without paclitaxel. The hazards ratios (HRs) for death and disease progression were 0.52 (95% CI: 0.29-0.96) and 0.48 (0.26-0.89) for high let-7a when compared to low let-7a, respectively. However, when patients were treated with platinum and paclitaxel, high let-7a was associated with worse progression-free and overall survival. The HRs for death and disease progression were 3.87 (95% CI: 1.28-11.66) and 3.48 (95% CI: 1.25-9.67) for high let-7a when compared to low let-7a, respectively. Further studies showed that among patients with low let-7a, those treated with paclitaxel in addition to platinum survived better than those treated without paclitaxel [adjusted-HRs were 0.31 (95% CI: 0.15-0.66) for death and 0.40 (95% CI: 0.22-0.75) for disease], while among those with high let-7a, the two types of treatment made no difference in patient survival.

CONCLUSIONS

The study suggests that the beneficial impact of the addition of paclitaxel on EOC survival was significantly linked to let-7a levels, and that miRNAs such as let-7a may be a useful marker for selection of chemotherapeutic agents in EOC management.

Frequent genetic abnormalities of the PI3K/AKT pathway in primary ovarian cancer predict patient outcome

Identification and characterization of underlying genetic aberrations could facilitate diagnosis and treatment of ovarian cancer. Copy number analysis using array Comparative Genomic Hybridization (aCGH) on 93 primary ovarian tumors identified PI3K/AKT pathway as the most frequently altered cancer related pathway. Furthermore, survival analyses to correlate gene copy number and mutation data with patient outcome showed that copy number gains of PIK3CA, PIK3CB, and PIK3R4 in these tumors were associated with decreased survival. To confirm these findings at the protein level, immunohistochemistry (IHC) for PIK3CA product p110α and p-Akt was performed on tissue microarrays from 522 independent serous ovarian cancers. Overexpression of either of these two proteins was found to be associated with decreased survival. Multivariant analysis from these samples further showed that overexpression of p-AKT and/or p110α is an independent prognostic factor for these tumors. siRNAs targeting altered PI3K/AKT pathway genes inhibited proliferation and induced apoptosis in ovarian cancer cell lines. In addition, the effect of the siRNAs in different cell lines seemed to correlate with the particular genetic alterations that the cell line carries. These results strongly support the utilization of PI3K pathway inhibitors in ovarian cancer. They also suggest identifying the specific component in the PI3K pathway that is genetically altered has the potential to help select the most effective therapy. Both mutation as well as copy number changes can be used as predictive markers for this purpose.

Frequent genetic abnormalities of the PI3K/AKT pathway in primary ovarian cancer predict patient outcome

Identification and characterization of underlying genetic aberrations could facilitate diagnosis and treatment of ovarian cancer. Copy number analysis using array Comparative Genomic Hybridization (aCGH) on 93 primary ovarian tumors identified PI3K/AKT pathway as the most frequently altered cancer related pathway. Furthermore, survival analyses to correlate gene copy number and mutation data with patient outcome showed that copy number gains of PIK3CA, PIK3CB, and PIK3R4 in these tumors were associated with decreased survival. To confirm these findings at the protein level, immunohistochemistry (IHC) for PIK3CA product p110α and p-Akt was performed on tissue microarrays from 522 independent serous ovarian cancers. Overexpression of either of these two proteins was found to be associated with decreased survival. Multivariant analysis from these samples further showed that overexpression of p-AKT and/or p110α is an independent prognostic factor for these tumors. siRNAs targeting altered PI3K/AKT pathway genes inhibited proliferation and induced apoptosis in ovarian cancer cell lines. In addition, the effect of the siRNAs in different cell lines seemed to correlate with the particular genetic alterations that the cell line carries. These results strongly support the utilization of PI3K pathway inhibitors in ovarian cancer. They also suggest identifying the specific component in the PI3K pathway that is genetically altered has the potential to help select the most effective therapy. Both mutation as well as copy number changes can be used as predictive markers for this purpose.

Abstract 3156: MicroRNA let-7a is a possible new marker for predicting the effect of paclitaxel in epithelial ovarian cancer

MicroRNA let-7 is a family of small non-coding RNAs post-transcriptionally regulating the expression of genes that are involved in cell proliferation, apoptosis and therapy response. Let-7 is shown in vitro to affect the sensitivity of cancer cells to platinum. Let-7a, a member of the let-7 family, is also found to induce ovarian cancer cell resistance to paclitaxel (taxol). The purpose of this study is to investigate the relationship of let-7a expression and survival outcomes of epithelial ovarian cancer patients treated with different chemotherapy. Levels of let-7a and RNU48 (an endogenous control for normalization) were analyzed using the Taqman® microRNA assays in 178 primary epithelial ovarian cancer patients who received chemotherapy after debulking surgery. Survival analysis was performed to assess the associations of let-7a expression with disease outcomes and chemotherapy. Patients with poor response to platinum with taxol had significantly higher let-7a expression than those with complete response, while no difference in let-7a expression between responders and non-responders treated with platinum without taxol. We also found that in patients treated with platinum without taxol, high let-7a was associated with better survival. The Hazard Ratios (HRs) for death were 0.55 (95% CI: 0.29-1.05) and 0.52 (95% CI: 0.29-0.96) when comparing patients with medium or high let-7a to those with low let-7a, respectively (p for trend = 0.033). Similar HRs for disease progression were 0.49 (95% CI: 0.27-0.91) and 0.48 (0.26-0.89), respectively (p for trend = 0.020). These associations became less significant when patient age at surgery, disease stage, tumor grade and histological type were adjusted in the analysis. However, in patients treated with platinum and taxol, high let-7a expression was associated with poor survival. The HRs for death were 1.70 (95% CI: 0.50-5.81) for medium and 3.87 (95% CI: 1.28-11.66) for high let-7a (p for trend = 0.009). The HRs for disease progression were 2.85 (95% CI: 0.99-8.22) for medium and 3.48 (95% CI: 1.25-9.67) for high let-7a (p for trend = 0.016). These associations remained significant after the analyses were adjusted for patient age at surgery, disease stage, tumor grade and histological type. These results suggest that let-7a may play different roles in disease outcome when patients received different combinations of chemotherapy, and the microRNA may serve as a marker for selecting patient who will respond to taxol treatment. This finding may have significant implication in the treatment of epithelial ovarian cancer with regard to reducing treatment cost and minimizing drug toxicity.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3156. doi:10.1158/1538-7445.AM2011-3156

Genomic instability and copy-number heterogeneity of chromosome 19q, including the kallikrein locus, in ovarian carcinomas

Many tissue kallikrein (KLK) genes and proteins are candidate diagnostic, prognostic and predictive biomarkers for ovarian cancer (OCa). We previously demonstrated that the KLK locus (19q13.3/4) is subject to copy-number gains and structural rearrangements in a pilot study of cell lines and ovarian cancer primary tissues, shown to overexpress KLK gene family members. To determine the overall frequency of genomic instability and copy-number changes, a retrospective study was conducted using formalin-fixed paraffin embedded (FFPE) tissues. Eighty-one chemotherapy naïve serous OCas were examined using 3-colour fluorescence in situ hybridization (FISH) to identify structural and numerical changes on 19q, including the KLK locus; in addition to immunohistochemistry (IHC) for KLK6, which has been shown to be overexpressed in OCa. The KLK locus was subject to copy-number changes in ∼83% of cases: net gain in 51%, net loss in 30% and amplified in 2%; and found to be chromosomally unstable (p < 0.001). All cases showed a wide range of immuoreactivity for KLK6 by IHC. Although no strong correlation could be found with copy-number, the latter was contributing factor to the observed KLK6 protein overexpression. Moreover, univariate and multivariate analyses showed an association between the net loss of the KLK locus and longer disease-free survival. Interestingly, FISH analyses indicated that chromosome 19q was subjected to structural rearrangement in 62% of cases and was significantly correlated to tumor grade (p < 0.001). We conclude that numerical and structural aberrations of chromosome 19q, affect genes including the KLK gene members, may contribute to ovarian carcinoma progression and aggressiveness.

IGF-II promoter specific methylation and expression in epithelial ovarian cancer and their associations with disease characteristics

High expression of insulin-like growth factor-II (IGF-II) in epithelial ovarian cancer is associated with aggressive disease and poor prognosis. IGF-II transcription is initiated from multiple promoters. Promoter-specific expression is regulated by DNA methylation, which is often dysregulated in cancer. Here, the effects of promoter-specific methylation on IGF-II expression are investigated in ovarian cancer. Fresh tumor samples were collected from 211 patients for analyses of IGF-II promoter methylation using methylation-specific PCR, and of promoter-specific expression of IGF-II mRNA with qRT-PCR, as well as tissue levels of IGF-II peptide with an ELISA. Cox regression analysis was performed to assess IGF-II methylation and expression in association with progression-free and overall survival. DNA methylation was high in IGF-II promoters 2 (P2, 64.2%) and 3 (P3, 52.1%) and low in promoter 4 (P4, 9.8%). High methylation was associated with low mRNA expression in a promoter-specific manner. P3 methylation and expression appeared to be critical in ovarian cancer compared to other promoters. While methylation in an individual promoter was not associated with the disease, a methylation pattern involving P2 and P3 was significantly different among patients with distinct tumor grade, debulking results, residual tumor size and treatment response. The methylation pattern was also associated with disease progression. The study suggests that DNA methylation regulates IGF-II promoter-specific expression in ovarian cancer and the regulation may play a role in disease progression. Assessing methylation patterns in IGF-II promoters may have clinical implications.

Double-negative feedback loop between reprogramming factor LIN28 and microRNA let-7 regulates aldehyde dehydrogenase 1-positive cancer stem cells

A relatively rare aldehyde dehydrogenase 1 (ALDH1)-positive "stem cell-like" subpopulation of tumor cells has the unique ability to initiate and perpetuate tumor growth; moreover, it is highly resistant to chemotherapy and significantly associated with poor clinical outcomes. The development of more effective therapies for cancer requires targeting of this cell population. Using cDNA microarray analysis, we identified that the expression of the Caenorhabditis elegans lin-28 homologue (LIN28) was positively correlated with the percentage of ALDH1+ tumor cells; this was further validated in an independent set of tissue arrays (n=197). Both loss-of-function and gain-of-function studies showed that LIN28 plays a critical role in the maintenance of ALDH1+ tumor cells. In addition, we found that there is a double-negative feedback loop between LIN28 and let-7 in tumor cells, and that let-7 negatively regulates ALDH1+ tumor cells. Finally, we report that a LIN28/let-7 loop modulates self-renewal and differentiation of mammary gland epithelial progenitor cells. Our data provide evidence that cancer stem cells may arise through a "reprogramming-like" mechanism. A rebalancing of the LIN28/let-7 regulatory loop could be a novel therapeutic strategy to target ALDH1+ cancer stem cells.

Let-7a regulation of insulin-like growth factors in breast cancer

Expression of certain microRNA genes is regulated by DNA methylation, which in turn affects the activities of their downstream molecules. Our previous study showed that methylated let-7a-3 was associated with low IGF-II expression and favorable prognosis of ovarian cancer. The roles of let-7a-3 methylation in breast cancer and in regulation of IGF expression in the tumor are still unknown. Let-7a-3 methylation, IGF mRNAs, and peptides were analyzed in 348 breast cancer samples using quantitative methylation-specific PCR, qRT-PCR, and ELISA, respectively. The associations of let-7a-3 methylation with IGFs, disease features, and patient survivals were analyzed. In vitro experiments were performed using HeLa cells transfected with let-7a precursors to assess the effect of let-7a on IGF expression. Let-7a-3 methylation was detected frequently in breast cancer. An inverse correlation between let-7a-3 methylation and IGF expression was observed in breast cancer, which was similar to that seen in ovarian cancer. Our in vitro experiment showed that let-7a could increase IGF expression in cancer cells which had low endogenous let-7a. Let-7a-3 methylation was also found to be associated with high grade tumors and ER- or PR-negative cancer. However, let-7a-3 methylation was not associated with disease-free survival or overall survival of breast cancer patients. The study provides further evidence in support of the notion that epigenetic regulation of let-7a-3 may affect the actions of IGFs in cancer. Let-7a may up-regulate the expression of IGFs in cancer cells, which is different from its inhibitory effects on other oncogenes.

Functional role and prognostic significance of CD157 in ovarian carcinoma

BACKGROUND

CD157, an ADP-ribosyl cyclase-related cell surface molecule, regulates leukocyte diapedesis during inflammation. Because CD157 is expressed in mesothelial cells and diapedesis resembles tumor cell migration, we investigated the role of CD157 in ovarian carcinoma.

METHODS

We assayed surgically obtained ovarian cancer and mesothelial cells and both native and engineered ovarian cancer cell lines for CD157 expression using flow cytometry and reverse transcription-polymerase chain reaction (RT-PCR), and for adhesion to extracellular matrices, migration, and invasion using cell-based assays. We investigated invasion of human peritoneal mesothelial cells by serous ovarian cancer cells with a three-dimensional coculture model. Experiments were performed with or without CD157-blocking antibodies. CD157 expression in tissue sections from ovarian cancer patients (n = 88) was examined by immunohistochemistry, quantified by histological score (H score), and categorized as at or above or below the median value of 60, and compared with clinical parameters. Statistical tests were two-sided.

RESULTS

CD157 was expressed by ovarian cancer cells and mesothelium, and it potentiated the adhesion, migration, and invasion of serous ovarian cancer cells through different extracellular matrices. CD157-transfected ovarian cancer cells migrated twice as much as CD157-negative control cells (P = .001). Blockage of CD157 inhibited mesothelial invasion by serous ovarian cancer cells in a three-dimensional model. CD157 was expressed in 82 (93%) of the 88 epithelial ovarian cancer tissue specimens. In serous ovarian cancer, patients with CD157 H scores of 60 or greater had statistically significantly shorter disease-free survival and overall survival than patients with lower CD157 H scores (CD157 H score > or =60 vs <60: median disease-free survival = 18 months, 95% confidence interval [CI] = 5.92 to 30.07 vs unreached, P = .005; CD157 H score > or =60 vs <60: median overall survival = 45 months, 95% CI = 21.21 to 68.79 vs unreached, P = .024). Multivariable Cox regression showed that CD157 is an independent prognostic factor for recurrence (hazard ratio of disease recurrence = 3.01, 95% CI = 1.35 to 6.70, P = .007) and survival (hazard ratio of survival = 3.44, 95% CI = 1.27 to 9.31, P = .015).

CONCLUSIONS

CD157 plays a pivotal role in the control of ovarian cancer cell migration and peritoneal invasion, and it may be clinically useful as a prognostic tool and therapeutic target.