This process has been particularly noted in the BxPC3 pancreatic cancer cell line, which has been reported to exhibit a high level of APP cleavage; however, the accompanying expression and cleavage of APLP2 in this cell line was not examined (24). Proteolysis of APLP2 or APP can be accomplished by the ��-site APP cleaving enzyme 1 (BACE1) or BACE2 (22,23,25). Tofacitinib IC50 In the context of Alzheimer��s disease, BACE1 and BACE2 cleavage of APP has been well characterized, and both conserved and unique cleavage sites on APP have been demonstrated for the two BACE proteins (26�C28). Recently, one BACE1 cleavage site in APLP2 was identified (23); however, BACE2 cut site(s) in APLP2 remain(s) unknown.

Both BACE proteins have been reported in pancreatic tissue, but reports differ on BACE1 and BACE2 expression and activity in pancreatic ductal and acinar cells (22,23,27,29�C32), which are cell types proposed to give rise to pancreatic cancer (33). In our current studies, we have identified increased APLP2 in human pancreatic cancer tissues, as compared to normal pancreatic tissues, and have investigated the forms of APLP2 expressed in pancreatic cancer cell lines. We observed high molecular mass APLP2, at the molecular mass previously shown to be modified by glycosaminoglycans (GAG) (20,34,35), in the majority of pancreatic cancer cell lines, as well as full-length APLP2 without GAG modification and 12�C15 kDa C-terminal fragments generated from secretase cleavage (22,23) in all these cell lines.

C-terminal fragments of APP were only abundantly observed in the BxPC3 cell line in our panel of pancreatic cancer cell lines, suggesting that cleavage of APLP2, rather than APP, is a consistent molecular feature of pancreatic cancer cell lines. Furthermore, we have shown that transformation of pancreatic ductal cells by transfected oncogenes induces an increase in APLP2 expression, with particular enhancement in the expression of the APLP2 C-terminal fragments. Downregulation of APLP2 and/or APP in the pancreatic cancer S2-013 cell line, which displays representatively low expression of APP C-terminal fragments, decreased cell proliferation, suggesting a role for both family members in the growth of pancreatic cancer cell lines. Finally, treatment with inhibitors of ��-secretases, enzymes that cleave APLP2 or APP to release C-terminal fragments, decreased the growth and viability of the pancreatic cancer cell line S2-013 but not of a non-transformed GSK-3 pancreatic ductal cell line. Overall, these studies suggest that APLP2 undergoes extensive modification and cleavage in pancreatic cancer cell lines, APLP2 (and APP) facilitate pancreatic cancer cell growth, and treatments that block APLP2 cleavage can diminish the growth of pancreatic cancer cells.