Rasv12 induces survivin/auroraB pathway conferring tumor cell apoptosis resistance
Résumé
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 Raswt and mutated RasV12 transformed colon carcinoma cells treated with several recombinant interferon combinations were analyzed by flow cytometer and immunoblot. Apoptotic pathways of resistant RasV12 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 Raswt colon carcinoma cell (HT29) apoptosis by caspases and PARP-1 cleavages in contrast to RasV12 mutated colon carcinoma cells (SW480, HT29 clone). However, RasV12 siRNA restored interferon sensitivity of RasV12-HT29 clone to apoptosis. Survivin siRNA increased interferon apoptosis in Raswt cells demonstrating the key role of this protein in cell survival. RasV12 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 RasV12 cells synergized to restore interferon -induced apoptosis. RasV12 cells are less sensitive than Raswt 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.