Abstract 3874: An isogenic cell line approach to MMTV integration site analysis

Development of mammary tumors in mice carrying the retrovirus, mouse mammary tumor virus (MMTV), occurs by insertional mutagenesis in which viral transcriptional regulatory elements drive increased expression of adjacent genes. Several oncogenes have been identified due to their ability to cause loss of cell growth control in this system. However, most virus positive tumors feature multiple integration sites, and determination of which may be significant in tumor growth represents a challenge to validation of importance of integration site genes. We have developed a panel of more than 20 independent cell lines derived from MMTV-induced tumors of BALB/c mice. Analysis of common integration sites led to the identification of Tmem170, encoding a predicted transmembrane protein of 144 amino acids. Tmem170 RNA is highly expressed in several cell lines in the panel, but not in normal mouse mammary gland. Rabbit antiserum against a peptide in the predicted extracellular domain revealed a single band migrating at approximately 40 KDa in SDS gels. We developed a panel of vectors encoding silencing RNAs targeting Tmem170 and introduced these into cell lines expressing the Tmem170 RNA. Two independent cell lines exhibited decreased doubling times in culture when Tmem expression was silenced. The cells were introduced into the mammary fat pads of isogenic BALB/c mice and silenced lines exhibited dramatically decreased tumor growth. These studies support Tmem170's oncogenic role in tumor growth. In addition, the use of an easily manipulated cell line model for assessing the contribution of upregulated genes to tumorigenesis in immune competent animals allows for testing of other potential oncogenes. 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 3874. doi:10.1158/1538-7445.AM2011-3874