Ngai Na Co

Understanding obesity and endometrial cancer risk: opportunities for prevention

Worldwide, obesity has become a major public health crisis. Overweight and obesity not only increase the risk of cardiovascular disease and type-2 diabetes mellitus but also are now known risk factors for a variety of cancer types. Among all cancers, increasing body mass index is associated most strongly with endometrial cancer incidence and death. The molecular mechanisms underlying how adipose tissue and obesity contribute to the pathogenesis of endometrial cancer are becoming better understood and have revealed a number of rational strategies, both behavioral and pharmaceutical, for the prevention of both primary and recurrent disease.

Exosomal transfer of stroma-derived miR21 confers paclitaxel resistance in ovarian cancer cells through targeting APAF1

Advanced ovarian cancer usually spreads to the visceral adipose tissue of the omentum. However, the omental stromal cell-derived molecular determinants that modulate ovarian cancer growth have not been characterized. Here, using next-generation sequencing technology, we identify significantly higher levels of microRNA-21 (miR21) isomiRNAs in exosomes and tissue lysates isolated from cancer-associated adipocytes (CAAs) and fibroblasts (CAFs) than in those from ovarian cancer cells. Functional studies reveal that miR21 is transferred from CAAs or CAFs to the cancer cells, where it suppresses ovarian cancer apoptosis and confers chemoresistance by binding to its direct novel target, APAF1. These data suggest that the malignant phenotype of metastatic ovarian cancer cells can be altered by miR21 delivered by exosomes derived from neighbouring stromal cells in the omental tumour microenvironment, and that inhibiting the transfer of stromal-derived miR21 is an alternative modality in the treatment of metastatic and recurrent ovarian cancer.

p53-R273H gains new function in induction of drug resistance through down-regulation of procaspase-3

Development of drug resistance is one of the major obstacles in cancer chemotherapy. The molecular mechanism leading to drug resistance is still not fully understood. A10A cells, a doxorubicin-resistant subline of human squamous cell carcinoma A431 cells, showed cross-resistance to methotrexate and also resistance to the drug-induced apoptosis. The cells also showed overexpression of a mutated form of p53, p53-R273H (Arg to His at codon 273), and down-regulation of procaspase-3. Knockdown of p53-R273H by p53 small interfering RNA in A431 cells increased procaspase-3 level and sensitized the cells to drug-induced apoptosis. On the other hand, transfection of p53-R273H into p53 null human osteosarcoma Saos-2 cells down-regulated procaspase-3 level and induced resistance to the drug toxicity and drug-induced apoptosis. The results support the idea that p53-R273H may gain new functions in induction of drug resistance and impairment in drug-induced apoptosis through down-regulation of procaspase-3 level. The study sheds new light on the understanding of the gain of function and drug resistance mechanisms associated with mutant p53. [Mol Cancer Ther 2007;6(3):1054–8]

Identification of FGFR4 as a Potential Therapeutic Target for Advanced-Stage, High-Grade Serous Ovarian Cancer

Purpose: To evaluate the prognostic value of fibroblast growth factor receptor 4 (FGFR4) protein expression in patients with advanced-stage, high-grade serous ovarian cancer, delineate the functional role of FGFR4 in ovarian cancer progression, and evaluate the feasibility of targeting FGFR4 in serous ovarian cancer treatment. Experimental Design: Immunolocalization of FGFR4 was conducted on 183 ovarian tumor samples. The collected FGFR4 expression data were correlated with overall survival using Kaplan–Meier and Cox regression analyses. The effects of FGFR4 silencing on ovarian cancer cell growth, survival, invasiveness, apoptosis, and FGF1-mediated signaling pathway activation were evaluated by transfecting cells with FGFR4-specific siRNAs. An orthotopic mouse model was used to evaluate the effect of injection of FGFR4-specific siRNAs and FGFR4 trap protein encapsulated in nanoliposomes on ovarian tumor growth in vivo. Results: Overexpression of FGFR4 protein was significantly associated with decreased overall survival durations. FGFR4 silencing significantly decreased the proliferation, survival, and invasiveness and increased apoptosis of ovarian cancer cells. Also, downregulation of FGFR4 significantly abrogated the mitogen-activated protein kinase (MAPK), nuclear factor-κB (NF-κB), and WNT signaling pathways, which are activated by FGF1. Targeting FGFR4 with the FGFR4-specific siRNAs and FGFR4 trap protein significantly decreased ovarian tumor growth in vivo. Conclusions: FGFR4 is a prognostic marker for advanced-stage, high-grade serous ovarian carcinoma. Silencing FGFR4 and inhibiting ligand-receptor binding significantly decrease ovarian tumor growth both in vitro and in vivo, suggesting that targeting ovarian cancer cells with high levels of FGFR4 protein expression is a new therapeutic modality for this disease and will improve survival of it. Clin Cancer Res; 19(4); 809–20. ©2012 AACR.

Another Surprise from Metformin: Novel Mechanism of Action via K-Ras Influences Endometrial Cancer Response to Therapy

Metformin is an oral biguanide commonly used for the treatment of type II diabetes and has recently been demonstrated to possess antiproliferative properties that can be exploited for the prevention and treatment of a variety of cancers. The mechanisms underlying this effect have not been fully elucidated. Using both in vitro and in vivo models, we examined the effects of metformin on endometrial tumors with defined aberrations in the PI3K/PTEN/mTOR and MAPK signaling pathways to understand metformin mechanism of action and identify clinically useful predictors of response to this agent. In vitro assays of proliferation, cytotoxicity, and apoptosis were used to quantify the effects of metformin on endometrial cancer cell lines with mutations in the PI3K/PTEN/mTOR and MAPK signaling pathways. The in vivo effects of oral metformin on tumor progression were further examined using xenograft mouse models of endometrial cancer. K-Ras localization was analyzed by confocal microscopy using GFP-labeled oncogenic K-Ras and by immunoblot following subcellular fractionation. Metformin inhibited cell proliferation, induced apoptosis, and decreased tumor growth in preclinical endometrial cancer models, with the greatest response observed in cells harboring activating mutations in K-Ras. Furthermore, metformin displaces constitutively active K-Ras from the cell membrane, causing uncoupling of the MAPK signaling pathway. These studies provide a rationale for clinical trials using metformin in combination with PI3K-targeted agents for tumors harboring activating K-Ras mutations, and reveal a novel mechanism of action for metformin. Mol Cancer Ther; 12(12); 2847–56. ©2013 AACR.

Loss of LKB1 in high-grade endometrial carcinoma

Liver kinase B1 (LKB1) is a serine/threonine kinase that functions as a tumor suppressor and regulates cell polarity, proliferation, and metabolism. Mutations in LKB1 are associated with Peutz‐Jeghers syndrome as well as sporadic cervical and lung cancers. Although LKB1‐null mice develop invasive endometrial cancers, the role and regulation of LKB1 in the pathogenesis of human endometrial cancer are not well defined and are the focus of these studies.

Loss of LKB1 in high-grade endometrial carcinoma: LKB1 is a novel transcriptional target of p53

Liver kinase B1 (LKB1) is a serine/threonine kinase that functions as a tumor suppressor and regulates cell polarity, proliferation, and metabolism. Mutations in LKB1 are associated with Peutz‐Jeghers syndrome as well as sporadic cervical and lung cancers. Although LKB1‐null mice develop invasive endometrial cancers, the role and regulation of LKB1 in the pathogenesis of human endometrial cancer are not well defined and are the focus of these studies.

Abstract 715: Adipose tissues derived exosomal microRNAs and their variants in ovarian cancer progression

Most ovarian cancers are diagnosed at an advanced stage when the tumor is widely metastatic. The 5-year survival drops to 50% for the cancer cases that spread beyond the pelvis to the omentum. However, the mechanisms underlying the effect of omental adipose tissue on ovarian cancer progression are poorly understood. Recent studies showed that exosomes also contain non-coding RNAs such as microRNAs (miRNAs). Thus, we hypothesize that the transfer of microRNAs and their variants from ovarian cancer-associated omental adipose tissues to ovarian cancer cells via exosomes may contribute to the nearby microenvironment for ovarian cancer metastasis and cancer progression. Ion Torrent next generation sequencing was performed on miRNAs isolated and enriched from exosomes and cell lysates of ovarian cancer cell lines (OVCA), the epithelial component of microdissected omental ovarian cancer tissues (CT), normal omental adipose tissues (OMN) and ovarian cancer-associated omental adipose tissues (OMT). By integrating the miRNA expression profiles, 65 miRNAs were expressed at significant higher levels in OMT-derived exosomes compared with those in OMN-derived exosomes and OVCA-derived exosomes. A set of miRNAs (miR-32a, miR-221 and miR320a), which had been implicated in controlling cell growth and chemoresistance, was identified. Also, the Ion Torrent results were validated and exosomal transfer of OMT-derived miRNAs was confirmed in vitro. The exosomal communication between adipose tissues and ovarian cancer cells in the omental tumor microenvironment is verified. The transferable miRNAs and their variants may remain functional in the recipient ovarian cancer cells and confer more aggressive phenotypes in these cells. Citation Format: Chi Lam Au Yeung, Tetsushi Tsuruga, Ngai Na Co, Tsz-Lun Yeung, Cecilia S. Leung, Kwong K. Wong, Samuel C. Mok. Adipose tissues derived exosomal microRNAs and their variants in ovarian cancer progression. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 715.

Abstract 1535: Omentin: A novel adipokine linking visceral obesity to ovarian cancer progression

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Advanced stage serous ovarian cancer metastasizes preferentially to the omentum, which is a major site of intra-abdominal fat accumulation, suggesting that the omental microenvironment is a favorable niche for ovarian cancer cells. The 5-year survival drops to below 50% for the cancer cases that spread beyond the pelvis to the omentum. It has also become apparent that obesity contributes to a poor clinical outcome. The mechanisms by which omental adipose tissue promotes tumor growth and disease progression are not entirely clear. Using transcriptome profiling analysis on the microdissected adipose tissue from patients with benign gynecologic diseases and from patients with advanced high-grade serous ovarian cancer (HGSOC), we found that a novel adipokine called omentin (Intestinal Lactoferrin Receptor ITLN1) was significantly down-regulated in ovarian cancer associated adipose tissue compared with the normal adipose tissue. Survival correlation studies demonstrated that patients with serum ITLN1 levels of >350 ng/mL at the time of first treatment experienced longer survival times than those with lower levels of ITLN1. We showed that ITLN1 suppressed the ovarian cancer cell migration ability and invasion potential in vitro. To delineate the underlying molecular mechanisms, RNA sequencing and pathway analyses were performed on ITLN1 treated ovarian cancer cells and we identified MMP1 as one of the potential mediators. It has been shown that MMP1 expression was induced by lactoferrin, which is abundant in ascites. We hypothesized ITLN1 could abrogate the effect of lactoferrin on ovarian cancer motility and invasion potential. Our preliminary data suggested that secreted ITLN1 may sequester lactoferrin in the ascites, thereby preventing it from binding to the low-density-lipoprotein-receptor-related-protein-1 (LRP-1) on ovarian cancer cell surface and thus inactivate downstream signaling pathways that control MMP1 expression. The study provides the first evidence that ovarian cancer cells modify the visceral adipose tissue through down-regulation of omentin to facilitate their growth in the omental microenvironment. Citation Format: Chi Lam Au Yeung, Ngai Na Co, Michaela Onstad, Tsz-Lun Yeung, Cecilia S. Leung, Rosemarie Schmandt, Karen H. Lu, Samuel C. Mok. Omentin: A novel adipokine linking visceral obesity to ovarian cancer progression. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1535. doi:10.1158/1538-7445.AM2015-1535

Abstract 4887: Omentin: A novel adipokine in the omental microenvironment associated with ovarian cancer progression

Advanced stage serous ovarian cancer metastasizes preferentially to the omentum, which is a well-vascularized fold of peritoneal tissue and is a major site of intra-abdominal fat accumulation, suggesting that the omental microenvironment is a favorable niche for ovarian cancer cells. The 5-year survival drops to below 50% for the cancer cases that spread beyond the pelvis to the omentum. It has also become apparent that obesity contributes to a poor clinical outcome. The mechanisms by which omental adipose tissue promotes tumor growth and disease progression are not entirely clear. Using transcriptome profiling analysis on the microdissected adipose tissue from patients with benign gynecologic diseases and from patients with advanced high-grade serous ovarian cancer (HGSOC), we identified a gene signature for ovarian cancer associated omental adipose tissue, suggesting that alteration of these genes in the ovarian cancer associated omental adipose tissue may generate a permissive microenvironment to support ovarian cancer growth. Among genes that are significantly up- or down-regulated in ovarian cancer associated adipose tissue compared with the normal adipose tissue, we seek to focus on evaluating the role of omentin (Intestinal Lactoferrin Receptor ITLN1) in ovarian cancer progression since it is a novel adipokine that is predominantly expressed and secreted by visceral adipose tissue and is barely detectable in subcutaneous fats. Our data showed for the first time that omentin was expressed predominantly by the mesothelial cells covering the visceral adipose tissue but not by other cell types in the omental adipose tissue. Interestingly, we showed that circulating omentin level is significantly lower in patients with HGSOC compared with those in the BMI matched healthy individuals. In addition, using monolayer culture models, we demonstrated that omentin suppressed ovarian cancer motility and invasion potential directly and ovarian cancer growth only in the presence of adipocytes. We also showed that omentin can increase insulin-dependent glucose up-take in adipocytes and omentin expression can be down-regulated by co-culturing with ovarian cancer cells and in the presence of TNF-α. The study provides the first evidence that ovarian cancer cells modify the visceral adipose tissue through down-regulation of omentin to facilitate their growth in the omental microenvironment. Citation Format: Chi Lam Au Yeung, Ngai Na Co, Michaela Onstad, Tsz-Lun Yeung, Cecilia S. Leung, Rosemarie Schmandt, Karen H. Lu, Samuel C. Mok. Omentin: A novel adipokine in the omental microenvironment associated with ovarian cancer progression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4887. doi:10.1158/1538-7445.AM2014-4887