Elevated expression of calcium-binding protein p9Ka is associated with increasing malignant characteristics of rat prostate carcinoma cells.

Northern and Western blotting techniques were used to study expression of the mRNA and corresponding protein product of the S100-related calcium-binding molecule p9Ka in 6 different metastatic cell lines of the Dunning R3327 rat prostate cancer model. In cells with the lowest metastatic capability (G cells), p9Ka mRNA was barely detectable. In 2 weakly metastatic cell lines (AT-1 and AT-2), p9Ka transcript amounts were, respectively, 6.29 +/- 0.74 and 5.55 +/- 1.11 times that detected in the G cells. In 3 highly metastatic cell lines (AT-3, MAT-LyLu and MAT-Lu), the amounts of p9Ka mRNA were, respectively, 12.85 +/- 2.82, 13.06 +/- 1.69 and 11.62 +/- 1.81 times that expressed in the G cells. Western blot analyses detected no p9Ka protein in the G cells. The amounts of p9Ka protein expressed by tumour cells of intermediate metastatic capability (AT-1 and AT-2) were 3.4 +/- 1.3 microg and 3.3 +/- 1.4 microg, respectively, per 1 x 10(6) cells. The amounts of p9Ka protein expressed by the tumour cells of highest metastatic capability (AT-3, MAT-LyLu and MAT-Lu) were 8.3 +/- 1.1 microg, 8.7 +/- 1.6 microg and 9.6 +/- 1.7 microg, respectively, per 1 x 10(6) cells. Our data reveal a direct association between the elevated expression of mRNA and the p9Ka protein amounts and the increased metastatic capability of individual prostatic cancer cell lines. We suggest that calcium-binding protein p9Ka may play an important role in the metastatic behaviour of rat prostate cancer.