[Effect of inhibiting the expression of hSMG-1 on chemosensitivity of human non-small cell lung cancer H1299 cells].

Objective: To investigate the effect of inhibiting the expression of human suppressor of morphogenesis in genitalia-1 (hSMG-1) on chemosensitivity in human lung cancer H1299 cells.

Methods: Specialized small interference RNAs (siRNAs) of hSMG-1 were transfected into H1299 cells. The knockdown effect was evaluated by quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence. After the administration of anti-cancer drugs, the cell viable rate was determined by cell counting kit (CCK-8) and apoptotic rate was measured by Annexin V-FITC PI double staining on flow cytometry. The apoptotic related activated caspase 3 and caspase 9 were determined by colorimetric assay.

Results: The expression of hSMG-1 mRNA was significantly inhibited by hSMG-1 siRNA. And the inhibition rate of (73.8 ± 10.3)% was obtained (P < 0.01). The knockdown effect was further confirmed by immunofluorescence. The inhibition of hSMG-1 enhanced the sensitivity of H1299 cells to gemcitabine and cisplatin. The survival rates significantly decreased when the hSMG-1 siRNA transfected cells were treated with 10.0 mg/L gemcitabine and 10.0 mg/L cisplatin for 48 h respectively (0.51 ± 0.02 vs 0.69 ± 0.01, P < 0.01 and 0.34 ± 0.03 vs 0.48 ± 0.01, P < 0.01;all compared with control siRNA group). Annexin V-FITC PI double staining showed that, under the treatment of anti-cancer drugs, the apoptotic rate of H1299 cells was significantly increased by hSMG-1 knockdown [gemcitabine, (20.9 ± 3.4)% vs (12.0 ± 2.7)%, P < 0.05; cisplatin, (10.2 ± 1.8)% vs (4.5 ± 2.0)%, P < 0.05; all compared with control siRNA group]. Further study showed the inhibition of hSMG-1 up-regulated the activated caspase 3 and caspase 9 in the treated H1299 cells (gemcitabine, 0.1 mg/L, 48 h, caspase 3: 14.4 ± 3.8 vs 2.3 ± 0.4, P < 0.01; caspase 9: 15.5 ± 2.4 vs 4.2 ± 0.9, P < 0.01; cisplatin, 1.0 mg/L, 48 h, caspase 3: 18.8 ± 3.0 vs 6.5 ± 1.5, P < 0.01; caspase 9: 20.3 ± 4.2 vs 8.1 ± 2.0, P < 0.05; all compared with control siRNA group).

Conclusion: The inhibition of hSMG-1 significantly enhances the sensitivity of human lung cancer H1299 cells to gemcitabine and cisplatin through an induction of more apoptotic cells. And the activation of mitochondrial apoptotic pathway is involved.