Functional inactivation of the O6-methylguanine-DNA methyltransferase (MGMT) gene has been demonstrated as loss of MGMT protein and suggested that it plays an important role in primary human neoplasia, including lung cancer. It has also been reported to be associated with the G : C→A : T transition mutation in the p53 gene of lung cancer. The aims of this study were to investigate the role of MGMT expression loss and its prognostic significance in non-small cell lung carcinomas (NSCLCs), and its correlation with p53 overexpression as well as influence on patient survival.
112 surgically resected NSCLC specimens were reviewed by medical records for their clinicopathologic variables. Their tissue microarray blocks were immunostained with anti-human MGMT and p53 primary antibodies. Correlation between MGMT loss and the clinicopathologic prognostic factors, including p53 overexpression and the single or combined actions of MGMT loss and p53 overexpression on patient survival were statistically analyzed by SPSS15.0.
Reduced or absent MGMT expression was found in 48 of 112 NSCLCs (43%), and significantly associated with nodal metastasis and squamous or undifferentiated cell types. Loss of MGMT expression was correlated with p53 overexpression in adenocarcinomas, but not in overall NSCLCs. Its solitary or combined actions with p53 overexpression did not have influence on patient survival.
Loss of MGMT expression is a relatively common event in NSCLCs and significantly associated with nodal metastasis and p53 overexpression, suggesting that it may play a major role in pulmonary carcinogenesis, and also in disease progression of NSCLCs.
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c-myc, bcl-2 and p53 are known to regulate apoptosis. There has been growing interest in analyzing their contribution to the pathogenesis and prognosis in a variety of human cancers. This study was undertaken to investigate the expression of these proteins in pulmonary adenocarcinomas and to determine their relationship with clinicopathologic parameters and survival.
Archival tumor tissues from 61 patients with adenocarcinoma of lung were analyzed by immunohistochemistry for the expression of c-myc, bcl-2 and p53 proteins. Clinical information was obtained through the computerized retrospect database from the tumor registry.
Of 61 patients, 32 were men and 29 women with the median age 63 years. 4 had stage I disease, 2 had stage II disease and 55 had stage III disease. The expression of c-myc protein was identified in 13% (8/61) tumors, bcl-2 protein was detected in 1.6% tumors (1/61) and p53 was detected in 77% (47/71) tumors. The association of the expression of c-myc, bcl-2 and p53 was not detected. The survival time was longer in patients expressing c-myc protein than in patients without the c-myc protein expression (p=.045). Neither bcl-2 nor p53 showed the correlation to clinicopathologic variables.
Our data suggest the involvement of p53 alteration in the pathogenesis of lung adenocarcinoma. The c-myc expression in some tumors indicates that c-myc alone may not contribute critically to the development and/or the progression of these tumors. It, however, correlated to the survival time, suggesting the c-myc expression as a favorable prognostic factor possibly through the apoptosis pathway.
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