Abstract A30: In vitro transformation of human primary epithelial cells by Myc

The Myc/Max/Mad network plays a critical role in cell proliferation, differentiation and apoptosis. Our previous data have shown that c-Myc is overexpressed in cervical cancer cell lines and that the HPV E6 oncoprotein in these cancer cells interacts with Myc both in vitro and in vivo. The consequence of these E6/Myc interactions results in the activation of telomerase and cell immortalization. Since the HPV E6/E7 genes cooperate to immortalize genital keratinocytes (both foreskin and cervical cells), we questioned whether Myc activation might be sufficient to replace E6 in cell immortalization. Our studies indicate that indeed Myc and E7 are sufficient to immortalize human genital keratinocytes. Surprisingly, the solitary transduction of Myc into cervical cells induced rapid cell death. These dying cells exhibited increased p53 expression and morphologic and biochemical characteristics of apoptosis. These results were also observed in human foreskin keratinocytes (when grown in commercially available, serum free medium) and suggest that the E7 protein counteracts the strong apoptotic activity of Myc. Myc-induced apoptosis in the genital keratinoctyes was observable as dramatic membrane blebbing. Since the Rho kinase (ROCK) inhibitor, Y-27632, has previously been shown to inhibit apoptosis in dissociated, detached stem cells, we tested whether it would inhibit membrane blebbing in Myc-expressing keratinoctyes and whether this might permit the establishment of Myc-driven keratinocyte cell lines. Within minutes, Y-27632 inhibited blebbing of Myc-expressing keratinocytes and reduced cell detachment. This activity is independent of expression of p53, pRB, and hTERT. More important, the use of Y-27632 allowed us to generate keratainocyte cell lines that were driven by overexpression of Myc. Our data suggest that immortalization and cell proliferation by Myc and Y-27632 are largely due to inhibition of apoptosis. An outgrowth of these studies is that we have screened for inhibitors of Myc-driven immortalization and found that two different HDAC inhibitors were able to induce cell death, including in established cervical carcinoma cell lines, and that cell death is paralleled by the down-regulation of Myc. Citation Format: Aleksandra Dakic, Shuang Fang, Sujata Choudhury, Nancy Palechor-Ceron, Songtao Yu, Richard Schlegel, Xuefeng Liu. In vitro transformation of human primary epithelial cells by Myc. [abstract]. In: Proceedings of the AACR Special Conference on Myc: From Biology to Therapy; Jan 7-10, 2015; La Jolla, CA. Philadelphia (PA): AACR; Mol Cancer Res 2015;13(10 Suppl):Abstract nr A30.