To investigate the effect and mechanism of Yse-associated protein (YAP) on the drug resistance of cisplatin in the A549/DDP cells of the patients with lung cancer.

MTS was used to detect the 50% inhibitory concentration (IC₅₀) of cisplatin in the lung adenocarcinoma A549 cells and lung adenocarcinoma-resistant cisplatin A549/DDP cells. The expression levels of YAP mRNA and protein in the A549 and A549/DDP cells were detected by quantitative polymerase chain reaction (qPCR) and Western blotting. Western blotting was used to detect the expression level of YAP protein after A549/DDP cells receiving treatment of verteporfin (VP). The A549/DDP cells were designed as the DMSO control group, cisplatin group (DDP group), verteporfin group (VP group), and cisplatin combined with verteporfin group (DDP+ VP group). And MTS was used to detect the cell viability in each treatment group immediately, 24 h, and 48 h after treatment. The changes of mRNA expression of the stem cell markers ALDHA1, CD133, OCT4, NANOG and SOX2 after A549/DDP cells receiving treatment of VP were detected by qPCR.

The IC50 values of cisplatin in the A549 and A549/DDP cells were (4.07±0.03) μg/ml and (23.44±0.98) μg/ml, respectively. YAP was significantly higher in the A549/DDP cells than in the A549 cells (P<0.05). The expression level of YAP protein in the VP-treated A549/DDP cells was significantly lower than that of the DMSO group. Compared with the DDP group, the DDP+ VP group showed a significant decrease in the cell viability 24 h and 48 h after treatment (P<0.05). After treatment with VP, the mRNA expression levels of the stem cell markers ALDHA1, CD133, OCT4, NANOG and SOX2 were significantly lower than those of DMSO group (P<0.05).

YAP may be involved in the cisplatin resistance in the lung cancer cells. Inhibition of YAP can play a role in reversing drug resistance through inhibiting the characteristics of cancer stem cells.