Gender differences in p53 gene mutations, p53, mdm2 protein expressions and mdm2 splicing transcripts in Taiwanese non-small cell lung cancer patients

• Main Authors: Kuan-Ying Yu, 余冠穎
• Other Authors: Huei Lee, Ph. D.
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/67368662140014477149

碩士 === 中山醫學院 === 毒理學研究所 === 88 === Lung cancer is the leading cause of cancer death in Taiwanese women. However, less than 10% of Taiwanese women are smokers, therefore smoking habit can not fully explain the development of female lung cancer in Taiwan. It is well known the p53 gene mutation and alteration of protein function play an important role in lung tumorigenesis. In this study, in order to verify whether gender difference is existed in p53 and mdm2 genes in Lung cancer is the leading cause of cancer death in Taiwanese women. However, less than 10% of Taiwanese women are smokers, therefore smoking habit can not fully explain the development of female lung cancer in Taiwan. It is well known that 53 gene mutation and alteration of protein function play an important role in lung tumorigenesis. In this study, in order to verify whether gender difference is existed in p53 and mdm2 genes in lung cancer development, 149 non-small cell lung cancer patients (NSCLC) including 47 non-smoking female lung cancer patients, 37 non-smoking male lung cancer patients, 64 smoking male lung cancer patients and one smoking female lung cancer patient were collected for p53 mutation, p53 and mdm2 protein expressions and mdm2 splicing transcripts analyzed by PCR/E-SSCP and autosequence , immunohistochemistry and nested RT- PCR, respectively. In p53 mutation assay, two of 48 female (4.2%) and 17 of 101 (16.8%) male lung cancer patients were found to have p53 mutations, showing that the mutation frequency of female lung cancer patients were significantly lower than male. Among non-smoking patients, the gender difference was also observed. These results show that smoking seem to be not influence the p53 mutation frequency in Taiwanese lung cancer. It appears to suggest that environmental or genetic factors may cause p53 mutations. In p53 mutation spectrum, transversion mutation (75%, 6/8) and deletion mutation (46%, 5/11) were predominately in non-smoking and smoking lung cancer patients, respectively. In this study, G→T mutation was frequently found in smoking lung cancer patients (75%, 3/4), not in non-smoking patients. This result is consistent with previous studies and suggests that environmental factors other than smoking may be involved in p53 mutation in non-smoking lung cancer patients. In immunohistochemistry data, we found that a higher frequency of p53 immunostaining negative (70.2, 40/57) was observe in female lung cancer patients compared to male. We also found that the undetectable frequency of mdm2 full length mRNA (mdm2 mRNA) in female lung cancer patients was significantly higher than male. This result strongly suggests that p53 protein can not transactivate mdm2 mRNA expression and p53 immunostaining negative seem to be p53 inactivation, not reflect wild type of p53 protein having short half-life because of no p53 mutations found in the majortiy of female lung cancer patients. In the nested PCR analysis, we found six splicing transcripts exists in lung tumors except detection of mdm2 full length mRNA. 31 of 117 lung tumors (26.5%) were found to have mdm2 splicing transcripts. Among the six splicing transcripts, mdm2-b (707 bp) is the predominate splicing transcript in lung tumors (83.9%, 26/31). Interestingly, male lung cancer patients had four-fold detectable frequency of mdm2 splicing transcripts in female lung cancer patients. The association between mdm2 splicing transcript and smoking status were shown in our study population. This shows that mdm2 splicing transcription in lung cancer may be caused by smoking. In this study, the normal lung tissues from 40 non-cancer controls were also detected mdm2 splicing transcript. Nine of 40 (22.5%) had mdm2 splicing transcripts. This result suggests that mdm2 splicing transcription seem to be not involved in lung tumorigenesis. In order to verify whether gender difference exists in p53/mdm2 and p53/p21 pathways, p53, mdm2, p21 and Rb protein expressions in lung tumors were analyzed by immunohistochemistry. Our results indicated that majority of female lung cancer patients had p53/mdm2 and p53/p21 negative immunostainings, suggesting gender difference in p53/mdm2 and p53/p21 pathways was obseved in lung tumorigenesis. Univarite analysis data showed that p53 positive immunostaining had favor prognosis in male smoking and non-smoking lung cancer patients, but not observed in female lung cancer patients. These results suggest that p53 and mdm2 genes play different roles between the development of male and female lung cancer.