Thymosin alpha 1 stimulates cell proliferation by activating ERK1/2 and JNK and increasing cytokine secretion in human pancreatic cancer cells

Abstract

Background: Thymosin alpha 1 (Thyα1) is the biologically active cleavage product of prothymosin alpha (PTalpha), which belongs to a larger family known as thymosins. Thyα1 and PTalpha have been shown to have significant immunostimulatory properties and play important roles in cancer. The objective of this study was to investigate the expression and functions of Thyα1 in human pancreatic cancer cells, and the molecular mechanisms involved in the Thyα1 pathway. Methods: Human pancreatic cancer cell lines (Panc-1, Panc 03.27, ASPC-1, and PL45) and human normal pancreatic ductal epithelia (HPDE) cells were used. The mRNA level of Thyα1 was determined by real time RT-PCR. Cell proliferation in response to synthetic human Thyα1 peptide was performed by[3H]thymidine incorporation assay. Phosphorylation of ERK1/2 and JNK and cytokine secretion profiles in pancreatic cancer cells after treatment with Thyα1 peptide were assessed by using Bio-Plex phosphoprotein and cytokine assays, respectively. Results: Panc-1, Panc 03.27, ASPC-1, and PL45 cells over-expressed the mRNA of Thyα1, which represented 187%, 141%, 214% and 152% of these mRNA levels in HPDE cells, respectively. In response to synthetic Thyα1 treatment,[3H]thymidine incorporation in Panc-1 cells was significantly increased by 33% as compared to that in untreated cells (n=5, P<0.05, t-test). ERK1/2 and JNK signaling pathways were found to be involved in the action of Thyα1 since increased phosphorylation of ERK1/2 and JNK was detected at the early stage of Thyα1 treatment in Panc-1 cells. Furthermore, Thyα1 increased the secretion of multiple cytokines including IL-8, IL-10, TNF-α, IL-13, and IL-17 in Panc-1 cells. Conclusions: These data demonstrated that Thyα1 was upregulated in pancreatic cancer cells, and that exogenous Thyα1 significantly increased pancreatic cancer cell proliferation with activation of ERK1/2 and JNK MAPKs and secretion of unique cytokines. This study suggests a new role of Thyα1 in pancreatic cancer pathogenesis; therefore, it could be considered as a potential therapeutic target for the treatment of pancreatic cancer.