RESUMO
Suppression of the activity of pro-apoptotic Bcl-2-family proteins frequently confers chemoresistance to many human cancer cells. Using subcellular fractionation, the ER calcium (Ca(++)) channel inhibitor dantrolene and small interfering RNA (siRNA) against Bax or Bak, we show that the new synthetic bichalcone analog TSWU-CD4 induces apoptosis in human cancer cells by releasing endoplasmic reticulum (ER)-stored Ca(++) through ER/mitochondrial oligomerization of Bax/Bak. Blockade of the protein kinase RNA-like ER kinase or the unfolded protein response regulator glucose-regulated protein 78 expression by siRNA not only suppressed oligomeric Bax/Bak-mediated pro-caspase-12 cleavage and apoptosis but also resulted in an inhibition of Bcl-2 downregulation induced by TSWU-CD4. Induction of the ER oligomerization of Bax/Bak and apoptosis by TSWU-CD4 were suppressed by Bcl-2 overexpression. Inhibition of lipid raft-associated phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling by TSWU-CD4 induced ER stress- and oligomeric Bax/Bak-mediated apoptosis, which were substantially reversed by overexpression of the wt PI3K p85α subunit. Taken together, these results suggest that suppression of lipid raft-associated PI3K/Akt signaling is required for the ER stress-mediated apoptotic activity of Bax/Bak, which is responsible for the ability of TSWU-CD4-treated cancer cells to exit the ER-mitochondrial apoptotic cell death pathway.
Assuntos
Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Chalconas/farmacologia , Estresse do Retículo Endoplasmático/efeitos dos fármacos , Fosfatidilinositol 3-Quinases/metabolismo , Piperazinas/farmacologia , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteína Killer-Antagonista Homóloga a bcl-2/metabolismo , Proteína X Associada a bcl-2/metabolismo , Cálcio/metabolismo , Bloqueadores dos Canais de Cálcio/farmacologia , Caspase 12/metabolismo , Linhagem Celular , Dantroleno/farmacologia , Chaperona BiP do Retículo Endoplasmático , Proteínas de Choque Térmico/metabolismo , Humanos , Mitocôndrias/metabolismo , Inibidores de Fosfoinositídeo-3 Quinase , Multimerização Proteica , Proteínas Proto-Oncogênicas c-akt/antagonistas & inibidores , Transdução de Sinais , eIF-2 Quinase/metabolismoRESUMO
The chalcone basic skeleton is a unique template which is associated with widespread biological activities. In the present study, a series of novel bichalcones linked with a 1,4-dimethylenepiperazine moiety was prepared through Mannich reaction and Clasien-Schmidt condensation. The synthetic analogs 2-16 were subjected into the cytotoxicity examinations using a panel of 25 human tumor cell lines. Among the tested compounds, 3 and 4 which possessed the 3-pyridyl and phenyl groups as the substructure, respectively, displayed significant cytotoxicity against all the tumor cell lines. The results suggested that these bichalcones were potential to be the anticancer lead drugs.
