Candidate tumor suppressor LUCA-15/RBM5/H37 modulates expression of apoptosis and cell cycle genes.

RBM5 (RNA-binding motif protein 5/LUCA-15/H37) is encoded at the lung cancer tumor suppressor locus 3p21.3 and itself has several important characteristics of a tumor suppressor, including both potentiation of apoptosis and inhibition of the cell cycle. Here, we report the effects of both upregulation and downregulation of LUCA-15/RBM5 on gene expression monitored using cDNA microarrays. Many of the genes modulated by LUCA-15/RBM5 are involved in the control of apoptosis, the cell cycle, or both. These effects were confirmed for the most significant genes using real-time RT-PCR and/or Western blotting. In particular, LUCA-15/RBM5 increased the expression of Stat5b and BMP5 and decreased the expression of AIB1 (Amplified In Breast Cancer 1), proto-oncogene Pim-1, caspase antagonist BIRC3 (cIAP-2, MIHC), and CDK2 (cyclin-dependent kinase 2). These effects on multiple genes controlling both apoptosis and proliferation are in line with the functional effects of LUCA-15/RBM5 and indicate that it plays a central role in regulating cell fate consistent with its tumor suppressor activity.