THYMOSIN BETA-15 EXPRESSION IN TUMOR-CELL LINES WITH VARYING METASTATIC POTENTIAL

We previously isolated thymosin beta 15 from highly metastatic Dunning rat prostatic carcinoma cells. Immunohistochemical study of human pro state cancer specimens revealed a general correlation between Gleason grade and thymosin beta 15 expression,,vith high-grade (more malignant ) tumors showing increased staining compared to low-grade tumors. To d etermine whether thymosin beta 15 may be differentially expressed in c ancer cells with different metastatic potential other than in the pros tatic carcinoma cells, we examined thymosin beta 15 mRNA levels in tum or cell lines from different species. We also examined thymosin beta 1 5 protein levels in human breast cancer samples. Thymosin beta 15 was upregulated in the highly metastatic mouse lung and human breast cance r cell lines in comparison to the nonmetastatic counterparts. Immunohi stochemical staining showed the evidence of upregulation of thymosin b eta 15 in malignant human breast carcinomas as compared to benign brea st tumors. The expression of thymosin beta 15 was correlated with the metastatic potential of the mouse lung carcinoma and human breast carc inoma cells in addition to the prostatic carcinomas. Thymosin beta 15 may be a useful marker to predict metastatic potential of certain huma n cancers. (C) 1998 Lippincott-Raven Publishers.