Gender-related survival differences associated with polymorphic variants of estrogen receptor-β (ERβ) in patients with metastatic colon cancer

The Pharmacogenomics Journal (2011) 11, 375–382 & 2011 Macmillan Publishers Limited. All rights reserved 1470-269X/11 www.nature.com/tpj ORIGINAL ARTICLE Gender-related survival differences associated with polymorphic variants of estrogen receptor-b (ERb) in patients with metastatic colon cancer OA Press1, W Zhang1, MA Gordon1, D Yang2, CA Haiman2, M Azuma1, S Iqbal1 and H-J Lenz1,2 1 Division of Medical Oncology, University of Southern California/Norris Comprehensive Cancer Center, Keck School of Medicine, Los Angeles, CA, USA and 2Department of Preventive Medicine, University of Southern California/ Norris Comprehensive Cancer Center, Keck School of Medicine, Los Angeles, CA, USA Correspondence: Dr HJ Lenz, GI Oncology and Colorectal Center, USC/Norris Comprehensive Cancer Center, Keck School of Medicine, Sharon A. Carpenter Laboratory, 1441 Eastlake Avenue, Suite 3456, Los Angeles, CA 90033, USA. E-mail: Estrogen replacement therapy in women has shown a protective effect on the development of colonic carcinomas. Gender-related differences in the development of colonic carcinomas have also been reported. Estrogen receptor-b (ERb) is expressed in colon carcinomas and has shown prognostic value in colon cancer patients. This study investigated an ERb 30 non-coding polymorphism associated with transcriptional activity to determine clinical outcome in patients with metastatic colon cancer. Genomic DNA from 318 metastatic colon cancer patients, 177 males and 141 females, were collected from 1992 to 2003. These patients were analyzed for CA repeat polymorphism of the ERb gene. Gender-related survival differences were associated with an ERb (CA)n repeat polymorphism (P for interaction ¼ 0.003, the likelihood ratio test). Female patients with any short o22 (CA)n repeat alleles had shorter overall survival (OS) compared with female patients who had both long X22 (CA)n repeat alleles. In the male patients, the opposite OS difference was found. This study supports the role of an ERb (CA)n repeat polymorphism as a prognostic marker in metastatic colon cancer; however, this prognostic factor had opposite implications based on gender. The Pharmacogenomics Journal (2011) 11, 375–382; doi:10.1038/tpj.2010.45; published online 15 June 2010 Keywords: colon cancer; gender; ERb; polymorphisms; ERb CA repeat polymorphism; clinical outcome Introduction Received 28 February 2010; accepted 26 April 2010; published online 15 June 2010 Colorectal cancer is the second most common cause of cancer-related death in the United States. In 2009, an estimated 106 100 new cases will be diagnosed and 49 920 deaths will occur.1 Recent evidence suggests that there are gender-related differences in the development of colonic carcinomas. Women of all ages are less likely to develop colon cancer.2–4 Animal models have also shown that male rats exposed to experimental carcinogens have a higher risk of developing colon cancer compared with female rats.5,6 Large comprehensive studies such as the WHI (Women’s Health Initiative) have shown conclusively that postmenopausal women treated with estrogen replacement therapy have a significant reduction in their relative risk of developing colon cancer.7,8 The molecular mechanisms by which estrogen replacement therapy exerts its protective effect against colon cancer are not understood. However, the presence of sex hormones and their receptors in the colon may influence the development of colon cancer differently in men and women. Survival differences in ERb polymorphisms related to gender OA Press et al 376 Estrogen receptor-b (ERb) is expressed in colonic tissue.9 Loss of ERb expression has been linked to malignant transformation10 and advanced Dukes stage.11 Colon cancer cell lines expressing ERb treated with estrogen have shown induction in apoptosis.12 ERb expression in the colon is also associated with regulation of important prognostic markers, such as thymidylate synthase, survivin, telomerase,13 adenomatosis polyposis coli tumor-suppressor gene14 and p38/ mitogen-activated protein kinase.15 Multiple review articles indicate that loss of ERb expression is a common step in the development of colonic carcinoma.16–18 Within the ERb gene, located on chromosome 14q22-32, is a polymorphic dinucleotide (CA)n repeat in the 30 noncoding region. In vitro studies of vector insertion of short (CA)n repeats show an association with increased ERb protein expression.19 Women with increased numbers of ERb CA repeats have a sixfold increase in the risk of developing colon cancer.20 The number of CA repeats in the ERb polymorphism is also associated with higher bone mineral density in premenopausal women21 as well as with increased androgen hormone levels and increased sex steroid-binding globulin levels.22,23 On the basis of this information, we tested the hypothesis that genetic variation at the ERb locus may be associated with gender-related survival in patients with metastatic colon cancer. Materials and methods Eligible patients A total of 318 patients with metastatic colon cancer treated at the University of Southern California/Norris Comprehensive Cancer Center (USC/NCCC) or the Los Angeles County þ University of Southern California Medical Center (LAC þ USCMC) between 1992 and 2003 were eligible for this study. This population included only metastatic or recurrent colon cancer patients. All patients in this study signed informed consents and enrolled in protocols designed to study the molecular determinants of colon cancer. These protocols permitted blood collection (protocol 0S-99-10) and/or tissue collection (protocol 0S-00-15). All enrolled patients were followed with an institutional database. Patient information was collected through database review and retrospective chart review when additional patient information was necessary. A large number of the patients (220/318 ¼ 69%) were initially treated at an outside institution until, because of failure to respond to previous treatment, they were referred to USC/NCCC or LAC þ USCMC for future treatments. The end point of this study was overall survival (OS). The OS was determined by calculating the difference between the date of first treatment at USC/NCCC or LAC þ USC and the date of last follow-up appointment or date of death from disease. All 318 patients were enrolled in at least one chemotherapy clinical trial while being treated at this institution (USC/NCCC or LAC/USCMC). All patients were treated with 5-fluorouracil-based chemotherapy regimens. Response to The Pharmacogenomics Journal chemotherapy was not investigated as an end point for this study. This is a heavily pretreated cohort with 20 patients (6%) treated with one line of chemotherapy, 19 patients (6%) treated with two different chemotherapy regimens, 183 patents (58%) treated with three different chemotherapy regimens and 96 patients (30%) treated with X4 chemotherapy regimens. Although the treatment regimens varied among patients, the (...truncated)