P2.06-31 Inhibition of Heat Shock Protein 70 Function Suppresses Proliferation in Mesothelioma Cells

Although Therapies for mesothelioma have been developed, their efficacy remains limited. Newer therapies based on improved molecular understanding of mesothelioma are needed. We have previously found that proliferation of mesothelioma cell lines is suppressed by transfecting small interfering RNA (siRNA) of dishevelled-3 (Dvl-3), an intermediator of Wnt signaling. Furthermore, when analysis of various mesothelioma cell lines using two-dimensional gel electrophoresis assay was conducted, heat shock protein 70 (HSP70) expression was commonly suppressed after transfection of Dvl-3 siRNA. To clarify the effect of inhibiting HSP70 function in mesothelioma cell lines, a small molecular compound VER-155008, adenosine-derived inhibitor of HSP70, was treated to cells, and its effects were evaluated. VER-155008 is adopted in various researches including Alzheimer’s disease, infectious diseases and so on, and other reports showed that it inhibits the function of HSP70 without altering the expression of HSP70. Mesothelioma MSTO-211H (211H), NCI-H2452 (H2452) and NCI-H28 (H28) cell lines were cultured with VER-155008 for the following analyses. The expression of HSP70 was confirmed using Western blotting. Cell viability was estimated using Cell Counting Kit-8 at 24, 48 and 72 h after adding 0.5–40 μM VER-155008 while mesothelioma cell lines were cultured on 96-well plates at 500-1000 cells/well. Colony formation and cell cycle analysis was conducted, after mesothelioma cell lines were cultured with 1–20 μM VER-155008 on 35-mm dishes. Furthermore, to estimate the synergistic effect with other anticancer drugs on cell growth, mesothelioma cell lines were cultured with VER-155008 and 0.5-5 μM cisplatin or gefitinib HSP70 protein was expressed in mesothelioma cells: 211H, H2452 and H28. Its expression was not altered by VER-155008 in these cells. VER-155008 dose-dependently suppressed mesothelioma cell growth. The colony formation was significantly suppressed with VER-155008 at 20 μM. The proportion of cell counts in G1 phase significantly increased in 211H and H28 cells. Cisplatin or gefitinib did not show synergistic growth suppression after 48 h of treatment with VER-155008. These results suggest that VER-155008 have ability to suppress mesothelioma proliferation with G1 arrest through inhibition of HSP70 function. Furthermore, we will elucidate HSP70 function and its relationship with other mechanisms for proliferation and surviving including signal transduction and autophagy in mesothelioma.