Aberrant Methylation of p16 Tumor Suppressor Gene and Death-Associated Protein Kinase in Non-Small Cell Lung Carcinoma

비소세포폐암 조직에서 p16 종양억제유전자와 Death-Associated Protein Kinase의 Aberrant Methylation의 양상

Background : The $p16^{INK4a}$ (p16) twnor suppressor gene is frequently inactivated in hwnan non-small cell lung cancers (NSCLCs), predominantly through homozygous deletion or in association with aberrant promotor hypermethylation. Death-associated protein kinase (DAPK) gene influences interferon $\gamma$-induced apoptotic cell death and has important role in metastasis of lung cancer in animal model. Hypermethylation of promoter region of DAP kinase gene may suppress the expression of this gene. Methods : This study was performed to investigate the aberrant methylation of p16 or DAP kinase in 35 resected primary NSCLCs by methylation-specific PCR (MSP), and demonstrated frequency, diagnostic value and clinical implication of aberrant methylation of two genes. Results : Thirty-two cases were male patients, and 3 cases were female patients with an average age was 57. $8{\pm}10.5$ years. The histologic types of lung cancer were 22 of squamous cell carcinoma, 12 of adenocarcinoma, 1 of large cell carcinoma. Pathologic stages were 11 cases of stage I (1 IA, 10 IB), 13 cases of stage II (1 IIA, 12 IIB), and 11 cases of stage III (9 IIIA, 2 IIIB). Regarding for the cancer tissue, p16 aberrant methylation was noted in 13 case of 33 cases (39.4%), DAP kinase in 21 cases of 35 cases (60%). Age over 55 year was associated with p16 aberrant methylation significantly (p<0.05). Methylation status of two genes was not different by smoking history, histologic type, size of tumor, lymph node metastasis and disease progression of lung cancer. There was no correlation between p16 and DAP kinase hypermethylation. Conclusion: This investigation demonstrates that aberrant methylation of p16 tumor suppressor gene or DAP kinase showed relatively high frequency (74.3%) in NSCLCs, and that these genes could be a biologic marker for early detection of lung cancer.

배 경 : p16 종양 억제 유전자 promoter의 aberrant methylation에 의한 불활성화가 비소세포 폐암이 발병하는 초기단계에 영향을 미치는 것으로 추측되며, DAP kinase 유전자 promoter의 hypermethylation은 유전자의 발현을 억제하여 폐암의 전이에 중요한 역할을 한다고 알려져 있다. 방 법 : 본 연구는 비소세포 폐암으로 근치적 절제술을 받은 환자 중에서 총 35 예를 대상으로 MSP률 이용하여 p16 유전자와 DAP kinase의 비정상적인 methylation의 양상을 조사하여, 폐암에서 두 유전자의 메틸화 빈도, 진단적 응용의 가능성 빛 임상적 유용성을 알고자 하였다. 결 과 : 전체 대상 35예중 p16 유전자의 aberrant methylation은 33예중 13예(39.4%)에서, DAP kinase 유전자 hypermethylation은 35예중 21예(60%)에서 확인할 수 있었다. 55 세 이상에서 p16의 aberrant methylation은 유의하게 증가되어 있었으며, DAP kinase는 병기의 진행도에 따라 발현 빈도가 증가하였으나, 통계학적 의미는 없었다. 또한 p16 유전자와 DAP kinase 유전자간의 메틸화 양상에서도 연관성은 관찰할 수 없었다. 결 론 : p16과 DAP kinase 유전자중 하나라도 비정상적인 메틸화가 발견된 경우는 전체 대상의 74.3% 로 비교적 높은 빈도로 관찰되어 폐암의 조기 진단을 위한 분자 생물학적 방법으로 이용될 수 있을 것으로 사료된다.