Tumor suppressor in lung cancer 1 (TSLC1) alters tumorigenic growth properties and gene expression

To investigate this mechanism, we compared growth properties of A549 with the TSLC1-containing derivative. We found a G1/S phase transition delay in 12.2. Subtractive hybridization, quantitative PCR, and TranSignal Protein/DNA arrays were used to identify genes whose expression changed when TSLC1 was up-regulated. Members of common G1/S phase regulatory pathways such as TP53, MYC, RB1 and HRAS were not differentially expressed, indicating that TSLC1 may function through an alternative pathway(s). A number of genes involved in cell proliferation and tumorigenesis were differentially expressed, notably genes in the Ras-induced senescence pathway. We examined expression of several of these key genes in human tumors and normal lung tissue, and found similar changes in expression, validating the physiological relevance of the A549 and 12.2 cell lines.Gene expression and cell cycle differences provide insights into potential downstream pathways of TSLC1 that mediate the suppression of tumor properties in A549 cells.Non-small cell lung cancer (NSCLC) includes squamous and large cell carcinomas and adenocarcinoma. NSCLC accounts for approximately 75% of all lung cancers diagnosed in the United States [1]. Genetic mutations that activate oncogenes such as KRAS2 and NRAS [2], and loss of function in tumor suppressors such as RB1, TP53, PPP2R1B, CDKN2A, and TSLC1 have been demonstrated in NSCLC tumors [3-7].A549 is derived from an NSCLC adenocarcinoma and displays several properties that are characteristic of transformed cells, including a short cell cycle, loss of contact inhibition, and rapid development of tumors following injection into athymic mice [8]. Introduction of a 1.1 Mb YAC derivative containing the TSLC1 gene into A549 restored TSLC1 expression to normal levels, creating the stable cell line, 12.2 [8]. 12.2 cells do not develop tumors following injection into athymic mice. TSLC1 protein is down-regulated or lost in NSCLC and a number of other neoplastic diseases,