Role of GLRX3 as a novel secretory biomarker of pancreatic cancer based on pancreatic cancer stem cell characteristics

Abstract

Pancreatic cancer is one of the most lethal diseases, which is difficult to diagnose and resistant to conventional treatment such as chemotherapy and radiotherapy. Cancer stem cells (CSCs) are implicated in carcinogenesis, cancer progression and recurrence. Several biomarkers for pancreatic CSCs were described but their function and mechanism were unclear. To find secretory biomarkers, pancreatic CSCs were enriched using sphere culture method. And secretome from culture medium of spheres and control adherent cells was analyzed by two-dimensional gel electrophoresis and MALDI-TOF. Total 200 spots were differentially expressed between spheres and adherent cells by at least 2 fold, and up-regulated 55 spots were identified. Proteins known to be associated with cancer or CSCs such as HSP90AB1, ALDH, vimentin, and AKR were up-regulated in spheres and the expression was confirmed by western blot. Among up-regulated proteins, GLRX3 was selected for the new pancreatic CSCs marker. The overexpression of GLRX3 was confirmed in two individual CSCs populations, spheres and CD24+/CD44+/ESA+ cells. The overexpression of GLRX3 was demonstrated in pancreatic cancer patient tissues, blood and cell lines. The role of GLRX3 in pancreatic carcinogenesis and CSCs properties was assayed by shRNA transfection in pancreatic cancer cell lines. Compared to the control cells, knockdown of GLRX3 decreased in vitro proliferation, migration, clonogenicity, and sphere formation. In addition, knockdown of GLRX3 reduced tumor formation and growth in SCID mice. Furthermore GLRX3 regulated chemosensitivity to gemcitabine via Met/PI3K/AKT signaling. This study reveals that secretory protein GLRX3 may be a useful prognostic marker and inhibition of endogenous GLRX3 may be a new therapeutic strategy for pancreatic CSCs.