RESUMO
Recent studies suggest JAK2 signaling may be a therapeutic target for treatment of gastric cancer (GC). However, the exact roles of JAK2 in gastric carcinogenesis are not very clear. Here, we have targeted JAK2 to be silenced by shRNA and investigated the biological functions and related mechanisms of JAK2 in GC cell SGC7901. In this study, JAK2 is commonly highly expressed in GC tissues as compared to their adjacent normal tissues (n = 75, p < 0.01). Specific down-regulation of JAK2 suppressed cell proliferation and colony-forming units, induced G2/M arrest in SGC7901 cells, but had no significant effect on cell apoptosis in vitro or tumor growth inhibition in vivo. Interestingly, JAK2 silencing-induced activation of ERK1/2, and inactivation of ERK1/2 using the specific ERK inhibitor PD98059 markedly enhanced JAK2 shRNA-induced cell proliferation inhibition, cell cycle arrest and apoptosis. Ultimately, combination of PD98059 and JAK2 shRNA significantly inhibited tumor growth in nude mice. Our results implicate JAK2 silencing-induced cell proliferation inhibition, cell cycle arrest, and ERK1/2 inhibition could enhance apoptosis induced by JAK2 silencing in SGC7901 cells.
Assuntos
Adenocarcinoma/enzimologia , Apoptose , Janus Quinase 2/genética , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Neoplasias Gástricas/enzimologia , Adenocarcinoma/tratamento farmacológico , Adenocarcinoma/patologia , Animais , Linhagem Celular Tumoral , Proliferação de Células , Feminino , Flavonoides/farmacologia , Pontos de Checagem da Fase G2 do Ciclo Celular , Técnicas de Silenciamento de Genes , Humanos , Janus Quinase 2/metabolismo , Sistema de Sinalização das MAP Quinases , Camundongos , Camundongos Nus , Proteína Quinase 1 Ativada por Mitógeno/antagonistas & inibidores , Proteína Quinase 3 Ativada por Mitógeno/antagonistas & inibidores , RNA Interferente Pequeno/genética , Neoplasias Gástricas/tratamento farmacológico , Neoplasias Gástricas/patologia , Carga Tumoral , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Although JAK2 inhibitors can result in antitumor activity against various tumors, some tumors have showed insensitivity or resistance to the inhibitors. To investigate the possible mechanisms underlying responses of gastric cancer (GC) cells to AG490, a specific JAK2 inhibitor, human GC cell lines SGC7901 and AGS were used. AG490 did not significantly induce apoptosis in SGC7901 cells, but it did in AGS cells. Interestingly, in SGC7901 cells, AG490 led to increased nuclear translocation of total JAK2 proteins, accompanied with initial inactivation but later reactivation of JAK2. However, in AGS cells, AG490 led to decreased nuclear localization of total JAK2 proteins, accompanied with sustained inactivation of JAK2. Moreover, silencing of human homolog of Drosophila Hairy and enhancer of split (Hes) 1 with siRNA partly blocked AG490-induced nuclear translocation of JAK2, and enhanced AG490-induced apoptosis in SGC7901 cells. The results collectively suggested that nuclear JAK2 signaling pathway may act as an escape way from JAK2 inhibitors in some GC cells.