[Synergistic effects and mechanisms of combined tumor necrosis factor-related apoptosis-inducing ligand and chemotherapeutic drugs or radiotherapy in killing laryngeal squamous carcinoma cells in vitro].
OBJECTIVE
To determine the sensitivity of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induced apoptosis in Hep-2 cells by means of systematically evaluating the cytotoxicity of TRAIL alone and TRAIL in combination with chemotherapeutic agents (cisplatin, paclitaxel) or radiation in Hep-2 cells in vitro, and whether the synergistic killing effects correlated with the expression level of TRAIL receptors and the activity of caspase-8 or caspase-9.


METHODS
The cytotoxicities of TRAIL, cisplatin and paclitaxel were investigated by cell counting kit-8 (CCK-8) assay. The expression levels of four TRAIL receptors in Hep-2 cells after treated by TRAIL, chemotherapeutic agents or radiation alone and by combined treatments were measured by flow cytometry and Western blotting respectively. The growth inhibition effects of caspase-8 or caspase-9 inhibitor on Hep-2 cells were determined by CCK-8 assay, and the activities of caspase-8, caspase-9 and caspase-3 were measured by Western blotting.


RESULTS
The half maximal inhibitory concentration (IC50) of TRAIL to Hep-2 cells on 24 h was 596.92 microg/L. Cisplatin, paclitaxel and radiation had synergistic inhibitory effects with TRAIL on the growth of Hep-2 cell line. After the activity of caspase-9 was inhibited by Z-LETD-FMK, the inhibition effects of TRAIL, cisplatin and paclitaxel on Hep-2 cells decreased significantly (all P<0.05). The expressions of caspase-8, caspase-9 and the death receptors (DR4 and DR5) increased significantly (all P<0.05) after combined administration.


CONCLUSIONS
Hep-2 cells are resistant to the apoptosis induced by TRAIL and TRAIL can induce the apoptosis of Hep-2 cells through the endogenous apoptotic pathway. The increase of death receptors expression by chemotherapeutic agents or radiation could enhance the sensitivity of Hep-2 cells to TRAIL and the synergistic killing effects.
Zhang
Ming
M
Department of Otorhinolaryngology, Eye Ear Nose and Throat Hospital, Fudan University, Shanghai 200031, China.
Zhou
Liang
L
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy; D045744:Cell Line, Tumor; D006801:Humans; D007822:Laryngeal Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy / Q000628:therapy; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*
D000970:Antineoplastic Agents; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human