Study On The Negative Expressions And Clinical Significances Of P14～(ARF) And P16～(INK4a) Proteins In Lung Cancer

Background and Objective Lung cancer continues to be the most common fatal malignancy of men and women. The development and progression of lung cancer is a multistep process characterized by the accumulation of numerous genetic and epigenetic alterations. A number of biological and predictive markers of lung cancer have been selected recently. Tumor suppressor gene INK4a/ARF is located on the short arm of chromosome 9p and encodes two proteins, p16INK4a and p14ARF, through the use of independent first exons and shared exons 2 and 3. p16INK4a is a cyclin-dependent kinase inhibitor, whereas p14ARF regulates the cell cycle through a p53 and MDM2-dependent pathway. Aberrant expression of p14ARF or p16INK4a protein has been reported in various malignancies. Our aim was to investigate the association of p14ARF and p16INK4a co-expression in resected lung carcinoma and evaluated their correlation with clinocopathologic features and clinical stages.Methods Sections were obtained from 10%-formalin-fixed and paraffin-embedded tissues, including 103 non-small cell lung cancer(NSCLC) samples, 25 small cell lung cancers(SCLC) samples, 37 metastatic lymph node lesions of NSCLC and 20 benign masses of lung. In order to evaluate the express levels of p14ARF and p16INK4a in these tissue slides, the expression of p14ARF and p16INK4a proteins was detected by immunohistochemistry. They were reacted with a rabbit anti-human p14ARF polyclonal antibody or a mouse anti-human p16INK4a monoclonal antibody. Cells showing p14ARF and p16INK4a staining patterns of (-) and (+/-) were considered to be negative, and (+~+++) to be positive. The data were analyzed by the χ2 test, Fisher's exact test and Pearson's correlation test. The values were considered significant at p<0.05.Results (1) The negative expression of p14ARF was detected in 73 (70.87%) of 103 NSCLC cases. 30 cases showed positive immunohistochemical result. While the negative expression of p16INK4a was detected in 45 (43.69%) of 103 NSCLC cases. 58 cases showed positive immunohistochemical result. The difference was significant for the negative rates of p14ARF and p16INK4a expressions (p<0.01). (2) In 103 NSCLC, 35(33.98%) cases showed simultaneous loss in both proteins, 10 (9.7%) cases showed positive expression of p14ARF and negative expression of p16INK4a, 38 (36.89%) cases showed negative expression of p14ARF and positive expression of p16INK4a, the negative rates of p14ARF and/or p16INK4a expressions was 80.58%, whereas there was no significant relationship between p14ARFor p16INK4a expression and lymph node metastasis (p>0.05). (3) The negative rates of p14ARF expression in squamous cell carcinoma, adenocarcinoma and bronchioloalveolar carcinoma were 88.24% (30/34), 72.73% (24/33) and 52.78% (19/36) respectively, and the significant difference was observed between the three groups (p<0.01). The negative rates of p16INK4a expressions in the three groups were 58.82%(20/34), 39.39%(13/33) and 33.33%(10/36) respectively, and the significant difference was observed between the groups of squamous cell carcinoma and bronchioloalveolar carcinoma. The negative rates of p14ARF and p16INK4a co-expressions in squamous cell carcinoma, adenocarcinoma and bronchioloalveolar carcinoma were 55.88%(19/34), 27.27%(9/33) and 19.44%(7/36) respectively, and the squamous cell carcinoma group was significantly higher than the others (p<0.01). (4) In 37 metastatic lymph node lesions of NSCLC, 75.68% (28/37) and 48.65% (18/37) of the samples displayed p14ARF and p16INK4a negative expressions. There was significant difference in the negative rates of p14ARF and p16INK4a expressions (p<0.05), in agreement with the difference in primary lesions of NSCLC. (5) Of the 65 samples analyzed from NSCLC patients, the negative rates of p14ARF and p16INK4a expressions were 54.05% (20/37) and 35.14% (13/37) in the groups of clinical stageⅠ～Ⅱ respectively, the negative rates of p14ARF and p16INK4a expressions were 78.57% (22/28) and 60.71% (17/28) in the groups of clinical stageⅢ～Ⅳ respectively. Eith...