Bortezomib and obatoclax for dual blockade of protein degradation pathways show synergistic anti-tumor effect in human acute T lymphoblastic leukemia cells / 南方医科大学学报

OBJECTIVE@#To explore whether bortezomib and a Bcl-2 inhibitor exhibit synergistic anti-tumor effect in human acute T lymphoblastic leukemia cells.@*METHODS@#MTT assay was used to determine the cytotoxicity of bortezomib in the absence or presence of Bcl-2 inhibitors (obatoclax, AT-101 and ABT-199) in Jurkat cells. The effects of drug treatment on the expression of Bcl-2 family proteins, LC3B, p62, ubiquitin, BiP/Grp78, p-JNK, p-p38 and CHOP proteins were examined by Western blotting. Flow cytometry was used to determine the effects of bortezomib and Bcl-2 inhibitors (obatoclax, AT-101 and ABT-199) on cell apoptosis. Quantitative real-time PCR was used to measure the mRNA expression levels of the key regulatory factors of unfolded protein reaction (UPR). A zebrafish xenograft model was used to study the anti-tumor effect of bortezomib, obatoclax and their combination in vivo.@*RESULTS@#Bortezomib or Bcl-2 inhibitors alone inhibited the cell viability of Jurkat cells, but only obatoclax and bortezomib showed synergistic cytotoxicity and pro-apoptotic effect. Obatoclax, rather than AT-101 and ABT- 199, blocked autophagic flux in the cells evidenced by concomitant accumulation of LC3B-Ⅱ and p62. Both bortezomib and obatoclax alone caused accumulation of polyubiquinated proteins, and their combination showed a synergistic effect, which was consistent with their synergistic cytotoxicity. The dual blockade of proteasome and autophagy by the combination of bortezomib and obatoclax triggered unfolded protein response followed by cell apoptosis. Preventing UPS dysfunction by tauroursodeoxycholic acid (TUDCA) significantly attenuated the cytotoxicity and pro-apoptotic effect of bortezomib in combination with obatoclax. In zebrafish xenograft models, bortezomib combined with obatoclax significantly decreased tumor foci formation.@*CONCLUSIONS@#Bortezomib and obatoclax for dual blockade of protein degradation pathways show synergistic anti-tumor effect in human acute T lymphoblastic leukemia cells.

CispIatin inhibits survivaI of human esophageaI squamous carcinoma ceIIs via p53 activation / 中国药科大学学报

To study the mechanisms whereby cisplatin suppresses survival of human esophageal squamous cell carcinoma cells.The cytotoxicity of cisplatin in cisplatin-resistant cell line EC109 /CDDP and its parental cell line EC109 was measured by cell viability assay.Western blotting was used to investigate the protein expression of to-tal p53 and phosphorylated p53 at Ser15.Colony formation assay was employed to evaluate the ability of cells to recover from treatments and form colonies.The results indicated that EC109 /CDDP cells were more resistant to cisplatin-induced cytotoxicity than EC109 cells,with the IC50 values of (20.4 ±4.4)μmol /L and (5.7 ±0.1 )μmol /L,respectively.Although cisplatin did not alter the total protein level of p53,it obviously increased the phosphorylation of p53 at Ser15.Cisplatin inhibited survival of both EC109 /CDDP and EC109.Notably,inhibition of p53 by Pifithrin-αsignificantly promoted recovery of cisplatin-treated EC109 and EC109 /CDDP cells to differ-ent degrees.In this respect,p53 protein was found to be activated in response to cisplatin treatment in both EC109 /CDDP and EC109,which may contribute to the cytotoxic effect of cisplatin.