Thymosin β15 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 prostate 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 determine whether thymosin beta 15 may be differentially expressed in cancer cells with different metastatic potential other than in the prostatic carcinoma cells, we examined thymosin beta 15 mRNA levels in tumor cell lines from different species. We also examined thymosin beta 15 protein levels in human breast cancer samples. Thymosin beta 15 was upregulated in the highly metastatic mouse lung and human breast cancer cell lines in comparison to the nonmetastatic counterparts. Immunohistochemical staining showed the evidence of upregulation of thymosin beta 15 in malignant human breast carcinomas as compared to benign breast tumors. The expression of thymosin beta 15 was correlated with the metastatic potential of the mouse lung carcinoma and human breast carcinoma cells in addition to the prostatic carcinomas. Thymosin beta 15 may be a useful marker to predict metastatic potential of certain human cancers. (C) 1998 Lippincott-Raven Publishers.