Expression And Significance Of Id-1 In Human OSCC And OLK

Inhibitors of differentiation (Id proteins) or called DNA binding inhibitors belong to a group of helix-loop-helix (HLH) proteins. It lacks the basic domain for DNA binding, and thus functions as a dominant negative regulator of the bHLH (basic helix-loop-helix) transcription factors by forming transcriptionally inactive heterodimers to inhibiting the bHLH from binding to target DNA sequences. Four Id genes (Id-1 through Id-4) are very important for cell fate decisions of growth and differentiation. Their expression is typically high in actively proliferating cells and is down-regulated as a prerequisite for exit from cell cycle and differentiation. The Id family member Id-1 is essential for cell differentiation, proliferation, migration, invasion and angio- -genesis, and the oncogenic role of Id-1 was revealed recently by the finding that Id-1 expression was able to induce cancer cell growth and promote cell survival. In addition, Id-1 protein was frequently overexpressed in over 20 types of cancer, including the breast, cervical as well as prostate cancer, which supported its role in the tumorigenesis of a wide range of tissues and showed its correlations with less differentiated phenotypes, high malignant potential and poor clinical outcome in various kinds of tumors.Our study estimated the expression level of Id-1 in tissue of OSCC, OLK and normal oral mucosa epithelium to investigate the relationship between expression of Id-1 and the clinicopathological parameters in OSCC and OLK.The cytoplasmic localization of Id-1 expression was determined by S-P immunohistochemical technique in the tissue of 46 patients with OSCC and in 31 cases of oral leukoplakia as well as in 11 cases of normal oral mucosa epithelium. The results of Id-1 expression level were compared with that in normal oral mucosa epithelium. Multiple clinicopathological factors such as histological sub-type, TNM classification, gender, age were analyzed according to their relations with the expression of Id-1.The findings from this study may be summarized as follows:1) The positive stain of Id-1 is in the cytoplasm of cells. The positive expression rate of Id-1 in OSCC tissues was 37.0%, which was significantly higher than that in OLK(22.6%) and in normal oral mucosa (0.0%), P＜0.05.2) With respect to the differentiation degree of OSCC, the expression of Id-1 was higher in patients of OSCC with lower differentiated cells than that with more differentiated phenotypes. The expression of Id-1 in OSCC showed negatively correlation with the differentiation degree of OSCC (r_s=-0.346, P=0.018＜α=0.05).3) There were no statistically significant difference (P＞0.05) in the expression of Id-1 between in patients with OSCC ofⅢ+Ⅳstage and that ofⅠ+Ⅱstage (P＞0.05).4) The expression level of Id-1 were higher in patients with lymphatic metastasis of OSCC than those without signs of metastasis. (P＜0.05)5) The expression of Id-1 in OSCC were not associated with patients' gender and age(P＞0.05)6) The positive stain rate of Id-1 of OLK tissues was 22.6%, and the expression level showed different status in OLK with or without dysplasia. The expression rate of Id-1 showed negatively correlation with the differentiation degree of OLK (r_s =-0.365, P=0.043＜α= 0.05)Based on these findings, the increased expression of Id-1 in OSCC versus OLK or normal oral mucosa may indicate that they are proteins correlated to proliferation and plays an important role in the tumorigenesis and progression of OSCC. The expression of Id-1 were associated with histological sub-type (differentiation phenotypes) of OSCC but not with patients' TNM classification, gender and age. (P＞0.05). The expression level of Id-1 in OSCC and OLK showed negatively correlation with their differentiation degree.