Abstract 1306: Synergistic function of a novel cell cycle regulator, Ecdysoneless with oncogenic Ras in the regulation of cell cycle and transformation

We have previously identified the mammalian ortholog of Drosophila ecdysoneless (Ecd) protein as a novel and essential regulator of Rb-E2F-dependent cell cycle progression. Consistent with role of Ecd in cell cycle, our recent studies show Ecd is overexpressed in breast cancer cell lines as well as in ductal carcinoma in situ and infiltrating ductal carcinomas of the breast. To explore the mechanism of Ecd overexpression and its correlation with oncogenesis, we overexpressed either Ecd alone, HRas-61L alone or both genes together in hTERT-immortalized human mammary epithelial cells (hMECs). These transfectants were then examined for their oncogenic properties. We observed while vector infected cells do not exhibit anchorage independence, all three transfectants showed increase in anchorage independent proliferation, particularly Ecd+Ras showed a significant increase in anchorage independence in comparison with either Ecd or Ras. Similarly, other oncogenic traits such as proliferation on matrigel, invasion and migration were dramatically increased when both genes were expressed in comparison with individual genes. Further analysis showed Ecd+Ras-expressing hMECs were unable to synchronize completely after growth factor deprivation and showed rapid progression into cell cycle, demonstrating synergy in altered cell cycle pathways in these cells. Most significantly, Ecd+Ras expressing hMECs were able to form tumors when implanted into mammary fat pads of NOD-SCID mice, whereas no tumors were observed with Ecd or Ras alone. These results demonstrate complete transformation of hMECs by overexpression of Ecd together with mutant Ras. Considering the known oncogenic role of Ras in human cancer and the known role of Ecd in cell cycle, these data are highly significant and present a novel synergistic pathway for mammary cell transformation. Current studies are directed towards defining the mechanism of synergy between Ecd and Ras in cellular transformation. Citation Format: Aditya Bele, Sameer Mirza, Riyaz Mir, Shakur Mohibi, Hamid Band, Vimla Band. Synergistic function of a novel cell cycle regulator, Ecdysoneless with oncogenic Ras in the regulation of cell cycle and transformation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1306. doi:10.1158/1538-7445.AM2014-1306