Expression of the matrix Gla protein in urogenital malignancies

Matrix Gla protein (MGP), is a vitamin-K-dependent protein which is synthesized in a variety of tissues such as lung, heart, kidney, cartilage and bone. The function of MGP in these tissues is unclear. We have previously reported elevated MGP mRNA levels in a breast-cancer cell line, 600PEI, as compared to normal breast epithelium. Here we describe high MGP expression in primary renal-cell carcinomas, prostate carcinomas and testicular germ-cell tumors, as determined by Northern analysis. MGP was over-expressed in 21 out of 28 patients with renal-cell carcinoma, and in 16 out of 29 patients with testicular germ-cell tumors, as compared to matched normal tissues. For the renal-cell carcinomas, a statistically significant inverse correlation was observed between the level of MGP expression and tumor size, lymph-node metastasis and tumor grade. MGP was also highly expressed in 13 primary prostatic carcinomas as compared to prostate cell lines derived from metastatic tumors, and to lymph-node metastasis. Our findings indicate that the loss of MGP expression may be associated wih tumor progression and metastasis.