Ras V12 induces Survivin/AuroraB pathway conferring tumor cell apoptosis resistance

Abstract

Several cancers are treated by interferons α and γ in association with conventional chemotherapy due to the resistance observed with interferon treatment alone. The frequency of un-sensitive cancer depends on tumor origin and oncogenic genes. Preclinical studies have highlighted interferon resistance in many cancers such as colon carcinoma due to oncogenic Ras. However, the resistance mechanism remains elusive. Apoptosis and proliferation of Ras wt and mutated Ras V12 transformed colon carcinoma cells treated with several recombinant interferon combinations were analyzed by flow cytometer and immunoblot. Apoptotic pathways of resistant Ras V12 cells were investigated using siRNA strategy to determine key proteins involved in this process. We show that interferons α and γ synergized to induce human Ras wt colon carcinoma cell (HT29) apoptosis by caspases and PARP-1 cleavages in contrast to Ras V12 mutated colon carcinoma cells (SW480, HT29 clone). However, Ras V12 siRNA restored interferon sensitivity of Ras V12-HT29 clone to apoptosis. Survivin siRNA increased interferon apoptosis in Ras wt cells demonstrating the key role of this protein in cell survival. Ras V12 mutation in HT29 clone neutralized the interferon effect on Survivin suppression and maintained high level of phospho-Aurora-B/Histone H3, which protected cells from apoptosis. SiRNA strategy against both Aurora-B and Survivin in Ras V12 cells synergized to restore interferon -induced apoptosis. Ras V12 cells are less sensitive than Ras wt cells to interferon induced cell apoptosis due to a Survivin/Aurora-B survival alternative pathway. Taken together, these results may provide interest in siRNA-therapeutic strategy and diagnostic relevance for therapy.