Malignant mesothelioma is an aggressive
tumor arising from mesothelial cells of serous membranes, and forms spheroid-like cell aggregates in pleural and peritoneal effusions. We examined the levels of anoikis, apoptosis induced by the detachment of cells from the extracellur matrix, in
suspension culture in the human
mesothelioma cell line NCI-H2052. NCI-H2052 cells were adherent in conventional monolayer cultures, but were found to form spheroids in
suspension cultures using dishes with ultra-low cell binding capacity. NCI-H2052 cells proliferated in both cultures, but the proliferation rate was markedly lower in
suspension cultures than in monolayer cultures. In addition, NCI-H2052 cells in
suspension cultures showed little apoptosis, suggesting that the
suspension culture induces anoikis resistance. Western blot analysis revealed that
suspension cultures induced activation of
Src family kinases (SFK) after spheroid formation.
Dasatinib, an inhibitor of multi-
tyrosine kinases including SFK, abolished anoikis resistance in
suspension cultures, indicating that SFK activated by spheroid formation are responsible for anoikis resistance.
Cisplatin induced apoptosis in NCI-H2052 cells, but the apoptotic rate was significantly lower in
suspension cultures than in monolayer cultures, suggesting that spheroid formation is involved in
cisplatin resistance. Furthermore, a combination of
dasatinib and
cisplatin induced apoptosis more significantly than either alone in
suspension cultures. These results suggest that spheroid formation induces resistance to anoikis and to
cisplatin through SFK activation and that
dasatinib facilitates
cisplatin-induced apoptosis in human
mesothelioma cells.