الفهرس | Only 14 pages are availabe for public view |
Abstract Summary Lung cancer is one of the deadliest cancers worldwide, with the highest incidence and mortality amongst all cancers. While the prognosis of lung cancer is generally grim, with 5-years survival rates of only 15%, there is hope, and evidence, that early detection of lung cancer can reduce mortality. Lung cancer can be classified into two major groups: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). The latter group is further divided into subtypes of squamous cell carcinoma, large cell carcinoma and adenocarcinoma. Among these three, adenocarcinoma is the most common subtype and has a high mortality rate. The methylation of tumor suppressor genes has been investigated in all kinds of cancer. Identification of tumor specific epigenetic alterations can be used as a molecular marker of malignancy, which can lead to better diagnosis, prognosis and therapy. Therefore, the aim of this study was to evaluate the association between gene hypermethylation and expression of fragile histidine triad (FHIT), glutathione S-transferase P1 (GSTP1) and p16 tumor suppressor genes and various clinicopathologic characteristics in primary non-small cell lung carcinomas (NSCLC). Summary - ١٥٤ - This study was conducted on 28 primary untreated NSCLC patients and 28 corresponding adjacent apparently normal tissue specimens. The patients were comprised of 20 males and 8 females who ranged in age from 32–68 years (median, 53 years) at the time of diagnosis. The morphological classification of the carcinomas was conducted according to the WHO specifications. Of the carcinomas, 16 were adenocarcinomas, 9 were squamous carcinomas, and 3 were large cell carcinomas. All patients were staged at the time of their surgery according to the guidelines of the American Joint Committee on Cancer. Five patients had Stage I, 11 patients had Stage II, and 12 patients had Stage III. The methylation status of the FHIT, GSTP1 and p16 promoters by MSP, and the expression levels of these genes as mRNA using a realtime PCR assay with SYBR -Green I were analyzed in all tissue sections (NSCLC & Control). The results presented in this study revealed that: • The promoter methylation of the FHIT gene was 53.57% (15/28) and 3.57% (1/28) in NSCLC and control groups; respectively, while that for the GSTP1 gene was 25% (7/28) and 0% (0/28) in NSCLC and control groups; respectively, however, the frequency for p16 gene promoter methylation was 0% (0/28) in both groups. Summary - ١٥٥ - • There were a significant statistical association between promoter methylation of the FHIT and GSTP1 genes and lung cancer risk as results of Relative Risk Ratio (RRR) showed that the risk of FHIT hypermethylation increased among patients with NSCLC by 2.88 while the risk of GSTP1 hypermethylation increased among patients with NSCLC by 2.33. • FHIT methylation occurred in 13 out of 20 men (65%) and 2 out of 8 women (25%) while GSTP1 promoter methylation in both males and females was 25% (5/20 and 2/8; respectively). Hypermethylation of the FHIT & GSTP1 gene promoters had no correlation with gender (p > 0.05). • The percentage of smoking patients with FHIT promoter methylation was 68.42% (13/19) and that for nonsmokers was 22.22% (2/9), while the percentage of smoking patients with GSTP1 methylation was 26.32% (5/19), similar to nonsmoking patients (22.22%), i.e. percentages of nonsmoking patients with FHIT & GSTP1 methylation were the same. Hypermethylation of FHIT gene promoter had a significant correlation with smoking habit (p <0.05) but there was no correlation between GSTP1 promoter hypermethylation and smoking habit (p > 0.05), table 5. • FHIT methylation occurred more frequently in squamous cell carcinomas (77.78%) than in adenocarcinomas Summary - ١٥٦ - (43.75%) and large cell carcinoma (33.33%) while GSTP1 methylation occurred more frequently in large cell carcinoma (33.33%) than in adenocarcinomas (25%) and squamous cell carcinomas (22.22%), however, these differing results were not statistically significant (p > 0.05). • FHIT promoter methylation in stage I was 0% (0/5), in stage II was 27.27% (3/11), and in stage III was 100% (12/12) while GSTP1 methylation in stage I was 20% (1/5), in stage II was 36.36% (4/11) and in stage III was 16.67% (2/12). Hypermethylation of FHIT gene had a highly significant correlation with pathologic staging (p < 0.01) but there was no correlation between GSTP1 hypermethylation and pathologic staging (p > 0.05). • About 10.71% (3/28) of the NSCLC patients had methylation of both gene promotors, while 57.14% (16/28) of NSCLC patients had methylation of at least one of the two gene promoters, and 32.14% (9/28) of NSCLC patients had no methylation of any of the two gene promoters. • Data obtained from qPCR analysis revealed that the expression level of FHIT mRNA was downregulated in 53.57% (15/28) of NSCLC tissues and that of GSTP1 mRNA was downregulated in 21.43% (6/28) of NSCLC tissues while that of p16 mRNA was upregulated in 75% (21/28) of NSCLC tissues. Summary - ١٥٧ - In conclusion, the results of the current study suggest that methylation of FHIT is a useful biomarker of biologically aggressive disease in patients with NSCLC. FHIT methylation may play a role in lung cancer’s later metastatic stage while GSTP1 methylation may play a role in the early pathogenesis of lung cancer rather than in its later metastatic stage. |