[Exogenous PTEN enhances apoptosis in pancreas cancer cell line ASPC-1 induced by hypoxia]

To investigate the effect of exogenous phosphatase and tensin homologue deleted on chromosome ten (PTEN) on cell cycle, the expression of vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR) proteins, and cellular proliferation ability in human pancreas cancer cell line (ASPC-1) exposed to normal oxygen or hypoxia 1% for 24 h were determined.

ASPC-1 cells were transfected in vitro with an eukaryotic expression plasmid (pEAK8) containing PTEN or not by lipofectin. Positive cell clones were selected, amplified and named ASPC-1-pEAK8-PTEN or ASPC-1-pEAK8 cells. RT-PCR and Western blot were used to determine the target gene expression. PTEN, VEGF and EGFR proteins were assessed by Western blot assay. Cell cycle and the induction of apoptosis were detected by flow cytometry. The tumor growth ability in vivo was assessed in nude mice, and cologenic survival ability was assayed under normal oxygen or hypoxia condition.

The expression of PTEN mRNA and protein in ASPC-1-pEAK8-PTEN cells were significantly higher than that in ASPC-1-pEAK8 or ASPC-1 cells. The expression of VEGF protein in ASPC-1-pEAK8-PTEN cells decreased by 23.4%, but EGFR showed no change. The plating efficiency was decreased by 28.0% (F = 4.283, P < 0.05) under normal oxygen condition, compared with those in ASPC-1 cells. The tumor volume in nude mice with ASPC-1-pEAK8-PTEN were significantly different compared to those with ASPC-1 5 weeks after implantation (t = 4.834, P < 0.01). The tumor inhibitory rate was 42.4% in ASPC-1-pEAK8-PTEN group. The expressions of VEGF and EGFR were decreased by 31.4% and 25.0%, respectively. In comparison with ASPC-1 cells, the plating efficiency of ASPC-1-pEAK8-PTEN cells was decreased by 33.2% (F = 9.152, P < 0.01) under hypoxic condition. The cellular apoptosis 8 h after hypoxia and G(2)/M blockage in ASPC-1-pEAK8-PTEN cells were remarkably higher than those in ASPC-1 cells.

Exogenous PTEN can block ASPC-1 cell cycle at the G(2)/M phase, enhance the cell apoptosis induced by hypoxia, inhibit the expression of VEGF and EGFR proteins under hypoxic condition, and inhibit the proliferation and growth of ASPC-1 cells.