[Expression of DNA excision repair enzymes and lung cancer prognosis]

To study the expression levels of three DNA damage excision repair enzymes: excision repair cross-complementing rodent repair deficiency gene 2 (ERCC2), uracil DNA glycosylase (UDG), and proliferating cell nuclear antigen (PCNA), in different lung tissues and their relationship with lung cancer prognosis.

The expression levels of ERCC2, UDG, and PCNA protein were detected using immunohistochemistry method. Cancer tissues and normal tissues adjacent to the cancer from 61 cases of lung carcinoma, and tissue samples from 18 cases of benign lung disease were studied. The relationship among ERCC2, UDG, and PCNA expression levels with lung cancer development and prognosis were studied using Ridit analysis method.

The expression levels of all three proteins were not significantly different between cancer tissues and a normal tissues adjacent to the cancer (P > 0.05); but significantly different between cancer tissues and benign tissues, and between normal tissues adjacent to the cancer and benign tissues (P < 0.05). ERCC2 and UDG levels were higher in benign tissues than those in cancer and cancer adjacent tissues, while the PCNA level was the opposite. Only the UDG level in cancer adjacent normal tissues showed no significant difference compared to that of benign tissues (P > 0.05). There were no relationship among age, smoke, cancer metastasis, cancer type and ERCC2, UDG, PCNA expression levels. ERCC2 also showed no relationship with degree of malignancy and cancer size, while UDG and PCNA expression levels were correlated with cancer malignancy and cancer size (P < 0.05). Low UDG and high PCNA expression levels were correlated with higher malignancy and larger tumors.

The expression levels of ERCC2, UDG and PCNA were significantly different in benign lung tissues, lung cancer tissues and lung cancer adjacent normal tissues. ERCC2 showed no significant relationship with lung cancer prognosis, while patients with low UDG and high PCNA expressions were more likely to have higher malignancy and larger tumors. UDG and PCNA were possible markers for evaluating lung cancer prognosis.