title: [Effects of p53 gene on drug resistance in human lung cancer cell lines.].
abstract: BACKGROUND
  Drug resistance of lung cancer cells is one of main factors which affect the outcome of chemotherapy. It has been reported that abnormal p53 gene is well assosiated with chemotherapy resistance of tumor cells. The aim of this study is to evaluate the effects of p53 gene on drug resistance in human lung cancer cell lines, so as to provide foundation of choosing individual chemotherapy drugs in clinical treatment.
  
  
  METHODS
  The expression vectors which contain p53cDNA and p53 antisense cDNA respectively were constructed and were confirmed by sequencing. Transfected the 801D, a human lung cancer cell line with recombined plasmids by lipofectin mediating. Several kinds of monoclone cell lines, pEGFP-801D,pEGFP-sense p53-801D(including sense p53,pEGFP-p53(RS)-801D),pEGFP-antisense p53-801D(including antisense p53,pEGFP-p53(AS)-801D),which contained p53 of different status were obtained. Green fluorescence was observed through fluorescence microscopy. The extraneous gene was detected by PCR. MTT assay was taken to determine the drug resistance of each cell line to chemotherapy agents. Cell cycle and apoptosis induced by antitumor drugs were examined by flow cytometer.
  
  
  RESULTS
  Extraneous sense p53 and antisense p53 were proved to be linked to plasmid respectively by sequencing.Green fluorescence was found in transfected cell lines. The IC50 of pEGFP-p53(AS)-801D cell line(0.26+/-0.09 mug/mL) to Cisplatin(DDP) decreased markedly compared with 801D(0.55+/-0.19 mug/mL,P<0.05)and pEGFP-801D(0.77+/-0.13mug/mL,P<0.05). The IC50 value of pEGFP-p53(RS)-801D to DDP is 0.43+/-0.25 mug/mL,which is significantly lower than that of pEGFP-801D(P =0.000)but higher than that of pEGFP-p53(AS)-801D(P <0.05). pEGFP-p53(RS)-801D cell line showed a notably smaller value of IC50(2.34+/-0.43 ng/mL) to Paclitaxel(TAX) than 801D(8.40+/-1.50 ng/mL, P <0.05)did. The IC50 value of pEGFPp53(RS)-801D is lower than that of pEGFP-801D(6.41+/-1.98 ng/mL),but not markedly. The IC50 of pEGFP-p53(RS)-801D cell line to 5-Fluorouracil(5FU) is 2.08+/-0.18 mug/mL, which is obviously lower than that of 801D(4.90+/-1.12 mug/mL,P <0.05) and pEGFP-801D(3.41+/-0.86 mug/mL,P <0.05). By the assay of flow cytometer, G2 phase arrest was observed when pEGFP-p53(AS)-801D was treated with DDP. TAX induced G2 phase arrest in pEGFP-p53(RS)-801D. A increased S phase proportion was induced by 5FU in pEGFP-p53(RS)-801D. The cell lines experienced apoptosis and necrosis when they were treated with either DDP or TAX.
  
  
  CONCLUSIONS
  p53 gene of different status have different effects on resistance of chemotherapy agents in lung cancer cell lines. p53 mutation and deletion are related to drug resistance of DDP. p53 deletion connects with chemoresistance of TAX and 5FU. Neither p53 mutation nor p53 deletion is associated with drug resistance of Navelbine(NVB) and Gemcitabine(GEM). It is helpful to choose sensitive drugs according to the p53 status of patients for enhancing the efficiency of chemotherapy.
authors: Department of Medical Oncology, Beijing Thoracic Tumor and Tuberculosis Hospital, Beijing 101100, China. taohong2000@126.com.
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