[The significance of p16, cyclin D1 and pRb expression in soft tissue leiomyosarcoma]

To evaluate the significance of p16, cyclin D1 and pRb expression in human soft tissue leiomyosarcoma (LMS) and the relationship among these three proteins.

42 cases of LMS were studied for p16, cyclin D1 and pRb expression with immunohistochemical method.

The total abnormality percentage of p16, cyclin D1 and pRb expression in all 42 cases of LMS was 97.6%. The negative rate of p16 and pRb protein expression was 35.7% and 47.6% respectively, and the overexpression rate of cyclin D1 was 57.1%. Overexpression of cyclin D1 was also noticed in 55% leiomyomas. In the 20 cases of LMS which were pRb negative, 19 cases were moderately or strongly positive and one faintly positive for p16. Contrastly, in the 15 cases of LMS negative to p16, 12 cases were moderately or strongly positive and 3 cases faintly positive for pRb. Higher rates of loss of pRb protein were observed in the low-differentiated group than in the high-differentiated one.

(1) The abnormality of p16-cyclin-pRb pathway is highly related to the pathogenesis of LMS. (2) Loss of p16 or pRb and/or overexpression of cyclin D1 may be involved in the pathogenesis of LMS. (3) There is a negative reciprocity between p16 and pRb protein expression in LMS. (4) Overexpression of cyclin D1 is a common molecular alteration that may occur in the early stage. (5) Expression of pRb is inversely related to the differentiation degree of LMS. (6) The expression of the 3 proteins studied has no relation to tumor location, recurrence, invasion or metastasis.