[Effects of exogenous wild type p53 on malignant growth of human lung cancer cell line]

To study the effects of exogenous wild type p53 suppressor gene on malignant growths of human lung cancer cell line with mutant type p53 gene.

Four human lung cancer cell line were screened for mutations in the exon 5 through exon 8 of the p53 tumor suppressor gene with immunohistochemistry, polymerase chain reaction (PCR)/single strand conformation polymorphism (SSCP) and DNA sequence analysis. The recombinent plasmid PZIPneoSV-p53 was constructed, which express wild type p53 gene. A transfected cell line, 801-D-p53, was obtained after transferred the plasmid into 801-D cell line by gene gun mediated and selected by G418. The exogenous p53 in the transfected cell line 801-D-p53 were inspected with PCR, and the alteration of growths of the transfected cell line in vitro and in vivo was observed.

The point mutation were CGG to CTT transversion at codon 248 in exon 7 was found in human lung cancer cell line 801-D by PCR-SSCP and DNA sequence analysis and nuclear accumulation of the p53 protein was observed. The neo gene and exogenous wild type p53 gene were detected in the transfected cell line 801-D-p53. The cell growth experiment in vitro showed that the parent cell line 801-D growth was very fast, from 1 x 10(5)/ml to 2.5 x 10(5)/ml within 6 days, the transfected PZIP-neo-SV cell line (plasmid without p53) growth as fast as 801-D, but the transfected cell line 801-D-p53 growth was inhibited seriously. The clonogenic formation rate of the parent cell line 801-D, transfected cell line 801-D-PZIP and the transfected cell line 801-D-p53 were 11.2%, 11.4% and 0.46% respectively. The clononogenic formation inhibition rate of the transfected 801-D-p53 was 96% comparing with the parent 801-D cell line. In the experiment of xenogenic tumor transplantation, each cell line was injected subcutaneously into four mice and the growth of xenogenic tumor transplant in nude mice was observed. xenograft growth in all 4 mice in both 801-D and 801-D-PZIP groups, but only 1 xenograft growth among 4 mice of 801-D-p53 group during 2 months. The average volume of xenogenic tumor transplant of 801-D and 801-D-PZIP groups were 6.500 cm3 and 2.231 cm3 respectively and the only xenograft volume of 801-D-p53 group was 0.940 cm3. The tumorigenicity of 801-D-p53 in nude mice was significantly suppressed.

Exogenous wild type p53 gene may stably exist in the human lung cancer cell line with mutant type p53 after plasmid transfection and suppressed the malignant growth of the transfected cell line 801-D-p53 in vitro and in vivo. These results indicate that the recombinent plasmid expressing wile type p53 may be useful for gene therapy of human lung cancer.