ABSTRACT
Objective To identify the expression of DLK1 protein in different types of renal cell carcinomas and its correlations with pathological characteristics and metastasis. Methods Immunohistochemistry analysis was performed to evaluate the expression of DLK1 protein in 94 cases of primary clear cell renal cell carcinoma, 76 cases of papillary renal cell carcinoma, 45 cases of chromophobe renal cell carcinoma, 71 cases of distal metastatic and 24 cases of lymph node metastatic clear cell renal cell carcinoma, as well as 18 cases of normal renal tissue. The correlations of DLK1 protein expression with pathological characteristics were analyzed. Results DLK1 protein was expressed in proximal and distal renal tubular epithelial cells in all the normal renal cases. In contrast, DLK1 protein expression was lower in different types of renal cell carcinoma. The low or negative expression of DLK1 protein in clear cell renal cell carcinoma, papillary renal cell carcinoma and chromophobe renal cell carcinoma was 33.0% (31/94), 27.6% (21/76) and 33.3% (15/45), respectively. Compared to normal renal tissue, DLK1 protein expression was significantly down-regulated in renal cell carcinomas (P＞0.05), whereas there was no significant difference on DLK1 protein expressions among the different types (P＞0.05) of renal cell carcinomas. DLK1 protein expression was not correlated with sex (60 male and 34 female cases), age (≥55, 50 cases and 55, 44 cases), grade (41 cases in grade I, 9 cases in grade II, 21 cases in grade III and 23 cases in grade Ⅳ respectively) and lymph node metastasis (76 cases with and 18 cases without lymph node metastasis) in clear cell renal cell carcinoma (P＞0.05). There was also no significant difference among primary, lymph node and distal metastatic lesions of clear cell carcinoma (P＞0.05). Conclusions DLK1 protein expression is commonly down-regulated in different types of renal cell carcinomas. Down-regulation of DLK1 protein expression is not associated with pathological characteristics and metastasis in clear cell renal cell carcinoma.