Thymosin ?-NB Is the Human Isoform of Rat Thymosin ?15
Thymosin ?15 is a small actin-binding protein upregulated in highly metastatic rat prostate cancer cells, relative to low metastatic cells. We have previously established an important role for thymosin ?15 as a diagnostic marker in human prostate cancer, with potential as a prognostic indicator. We here review the data supporting increased thymosin ?15 expression in other cancer types, including breast, brain, and lung. Human NB thymosin ? is a ?-thymosin originally found in neuroblastoma. New data demonstrate that NB thymosin ? represents the human homolog of rat thymosin ?15; thus we suggest classification as human thymosin ?15. In addition to the previously described gene, thymosin ?15a, we report the discovery of a new isoform of human thymosin ?15, thymosin ?15b, which is transcribed from an independent gene on human chromosome X. The gene structure of thymosin ?15a and ?15b is conserved and the isoforms show 87% identity across the nucleotide sequence. Across the coding sequence the nucleotide differences are silent, resulting in identical proteins. Other thymosin family members have recently been shown to exert potent clinical effects. The functional data available for thymosin ?15, combined with the tumor expression pattern, suggest that thymosin ?15 may play an important role in tumor development and progression in addition to its value as a biomarker in prostate cancer
thymosin ?15 prostate cancer thymosin nb