Abstract 4769: Inhibition of ribosomal protein L9 expression suppresses colorectal carcinoma cell growth in vitro and in vivo

Abstract

Abstract Background: Ribosomal protein L9 (RPL9), a component of the 60S subunit, is upregulated in human colorectal cancer (CRC). We thus hypothesized if targeting of RPL9 with small interfering (si) RNA could inhibit CRC progression. We also investigated molecular mechanism to mediate CRC cell death caused by RPL9 silencing. Methods: HCT116 and HT29 human CRC cells were transfected with RPL9 siRNA and tested for growth inhibition and apoptotic induction using MTS, FACS and microscopic analysis. To obtain insights into the molecular changes in response to RPL9 knockdown, global changes in gene expression were examined using RNA sequencing. Results: RPL9 silencing caused inhibition of CRC cell growth through induction of apoptotic cell death. RNA sequencing revealed that RPL9-specific knockdown led to dysregulation of 622 genes in HCT116 and 2882 genes in HT29 cells. Among those, 256 genes showed the same directional regulation (128 up- and 168 down-regulated genes), including up-regulation of tumor suppressors such as KLF6 and ATF3, and were considered as a common RPL9 knockdown signature. Western blotting proved that downregulation of RPL9 was accompanied with the decrease in the levels of PARP-1 and pro-caspase 3 delaying cell cycle progression and accelerating apoptotic signaling. Of importance, targeting RPL9 significantly inhibited CRC growth in a murine xenograft model. Conclusion: These results suggest that inhibition of RPL9 expression could be an attractive option for molecular targeted therapy of colorectal cancer. Citation Format: In Hye Baik, Keon Uk Park, Ilseon Hwang, Hun-Mo Ryoo, Yun-Han Lee. Inhibition of ribosomal protein L9 expression suppresses colorectal carcinoma cell growth in vitro and in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4769.