Abstract 495: Overexpression of the cold-inducible RNA binding protein RBM3 attenuates the stem cell-like features of PC-3 cells

Abstract

Abstract Introduction: It has long been thought that the stem cell-like features of cancer cells contribute to their evolutionary capability to escape therapeutic strategies, such as chemotherapy, radiotherapy, or hormone deprivation in prostate cancer (PCa). At the same time, temperature is perhaps one of the most important elements of the environment. One of the most clinically relevant examples of the effect of temperature on stem-like cells is cryptorchidism, in which germ cells maintained at body temperature that is several degrees higher than in the scrotum do not function to form sperm. In contrast, these pluripotential cells have a high likelihood to develop cancer if they are not rescued by relocating them to the scrotum and therefore a lower environmental temperature, in very early childhood. RNA binding motif 3 (RBM3) belongs to a cold-inducible RNA binding protein family and has been shown to be highly expressed in normal testis tissue but is decreased in cryptorchid mouse. We previously reported that RBM3 was decreased by heat treatment in PCa cell lines. The goal of this study is to investigate the effect of RBM3 over-expression on stem cell-like features of PC-3 cells. Methods: RBM3 mRNA expression was detected by RT-PCR in fetal and adult human tissues, as well as in PCa samples. The normal prostate cell line, PrEc, was sorted with the stem cell surface marker CD133 using flow cytometry. PC-3 cells were transfected with pCMV6-RBM3-GFP vector. The soft agar clonogenic assay was performed with RBM3- or control vector-transfected cells. The expression of stem cell-related genes and miRNAs was determined using PCR array. Results: The RBM3 mRNA level is decreased in fetal tissues and CD133 (+) PrEc cells in comparison to adult tissues and CD133 (−) cells, respectively. Metastatic PCa expresses lower RBM3 mRNA than primary tumors. Moreover, RBM3 expression was decreased upon treatment of chemotherapy and maintained at a low level in the surviving clones after intensive chemo- or heat treatment in both PC-3 and DU-145 cells. PC-3 cells that over-express RBM3 demonstrated less heterogenic morphology than those with a control vector. Importantly, RBM3 over-expression greatly attenuates the anchorage-independent clonogenic ability of PC-3 cells. Additionally, a panel of genes and miRNAs that are involved in neural cell differentiation and self-renew are altered upon RBM3 expression. Conclusion: Taken together, these data suggest that lowering RBM3 may play an important role in maintaining the stem cell-like features of cancer cells during development and progression under environmental stress. 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 495. doi:10.1158/1538-7445.AM2011-495