OBJECTIVETo study the effect of extraneous p53 gene with deletion of c-terminal 356 - 393 amino acids on inhibition of malignant phenotype of human lung cancer cell line.

METHODSRecombinant plasmid pEGFP-p53 (del) with codon deletion of c-terminal 37 amino acids from 393 to 356 region and pEGFP-p53 (wild type) were constructed. The human lung cancer cell line 801D served as a receipt cell had p53 deletion and mutation at 248 codon. 801D cells, having been transfected by pEGFP-p53 (wild type), pEGFP-p53 (del) or pEGFP, were selected by G418. Growing transfected cells were cloned respectively by method of dilution. Presence of extraneous gene was detected by PCR, their expression in cells was examined by fluorescence microscopy. Cloning efficiency was in vitro tested to examine the cellular proliferating ability. The xenograft in nude mice was performed and xenograft tumors were weighed one month later. Expression of GFP in tumor and transplanted cellular mass were detected by blot slices.

RESULTSpEGFP-p53 (del)-801D, pEGFP-p53-801D and pEGFP-801D were established. Extraneous p53 gene and expression of GFP were found in pEGFP-p53 (del)-801D and pEGFP-p53-801D. Inhibitory rate of colony was 99.6% for pEGFP-p53 (del)-801D and 81.0% for pEGFP-p53-801D. Inhibition of malignant proliferation of extraneous p53 (del) was higher than that of p53 (wild type) (P < 0.01). Even when inhibition of malignant proliferation extraneous pEGFP-p53 (del) was obvious, 0.2% colonies were formed, extraneous p53 and expression of GFP were observed. Animal test showed that tumor on the nude mice was positive (4/4, 4/4) in the control group (801D and pEGFP-801D), but negative (0/4, 0/4) in the experiment group [pEGFP-p53 (del) 801D and pEGFP-p53 (wild type) 801D]. Expression of GFP in the cells of cellular mass transplanted by pEGFP-p53 (del) 801D or pEGFP-p53 (wild type) 801D was observed.

CONCLUSIONIn vitro inhibitory effect of extraneous p53 gene with deletion of C-terminal 356 - 393 amino acids on malignant growth of lung cancer cell with p53 mutation or deletion at 248 codon is marked. Inhibitory action of p53 on malignant proliferation of cancer cells is heterogeneous.