Sialofucosylated podocalyxin is a functional E- and L-selectin ligand expressed by metastatic pancreatic cancer cells

Abstract

<jats:p>Selectin-mediated interactions in the vasculature promote metastatic spread by facilitating circulating tumor cell binding to selectin-expressing host cells. Therefore, identifying the selectin ligand(s) on tumor cells is critical to the prevention of blood-borne metastasis. A current challenge is to distinguish between structures expressed by circulating tumor cells that can bind selectins in vitro from the functional ligands whose depletion suppresses selectin-dependent binding under flow in vivo. Interestingly, podocalyxin (PODXL), which can bind E- and L-selectin, is upregulated in a number of cancers, including those of the breast, colon, and pancreas. In this work, we show that metastatic pancreatic cancer cells overexpress PODXL compared with nonmalignant pancreatic epithelial cells. We further demonstrate via tissue microarray that 69% of pancreatic ductal adenocarcinomas stain positive for PODXL. In cases of focal expression, positive staining is restricted to the invasive front of primary tumors. By combining immunoblot, immunodepletion, short-hairpin RNA-mediated gene silencing, and flow-based adhesion assays, we evaluated the functional role of sialofucosylated PODXL in selectin-mediated adhesion under flow. Our data indicate that sialofucosylated PODXL is a functional E- and L-selectin ligand expressed by metastatic pancreatic cancer cells, as specific depletion of this molecule from the cell surface significantly interferes with selectin-dependent interactions. Cumulatively, these data support a correlation between sialofucosylated PODXL expression and enhanced binding to selectins by metastatic pancreatic cancer cells and offer additional perspective on the upregulation of PODXL in aggressive cancers.</jats:p>

Overexpression of microRNA-5100 decreases the aggressive phenotype of pancreatic cancer cells by targeting PODXL

“…hsu et al reported PODXL-ebP50-ezrin molecular complex enhances the metastatic potential of renal cancer through recruiting RAC1 guanine nucleotide exchange factor, ARhgeF7 (60). Lin et al reported that PODXL promotes invadopodia formation and metastasis through activation of RAC1-Cdc42-cortactin signaling in breast cancer cells (61) and it is thought to regulate cell adhesion through its connections to intracellular proteins and to extracellular ligands (31)(32)(33)(34)(35). In our study, the adhesion capability of MS cells that showed high PODXL expression was remarkably decreased compared with that of low PODXL-expressing cells, as previously reported (31)(32)(33)(34)(35).…”

“…Lin et al reported that PODXL promotes invadopodia formation and metastasis through activation of RAC1-Cdc42-cortactin signaling in breast cancer cells (61) and it is thought to regulate cell adhesion through its connections to intracellular proteins and to extracellular ligands (31)(32)(33)(34)(35). In our study, the adhesion capability of MS cells that showed high PODXL expression was remarkably decreased compared with that of low PODXL-expressing cells, as previously reported (31)(32)(33)(34)(35). In addition, we showed for the first time that PODXL played an important role in pancreatic tumor aggressiveness by promoting cancer cell migration and invasion.…”

“…Recent studies showed that increased expression of PODXL is correlated with poor prognoses in many types of cancer (36)(37)(38)(39)(40)(41). Although the expression of PODXL has been reported to promote anti-adhesion and migration, how PODXL correlates with tumor metastases remains unclear, especially in pancreatic cancer (33). In this study, we identify an anti-metastatic miRNA, miR-5100, that decreases the metastatic ability of pancreatic cancer partially by suppressing expression of PODXL.…”

“…PODXL was initially identified in podocytes of renal glomeruli that are instrumental in kidney development (25,26 expression of PODXL was identified in podocytes, hematopoietic progenitors, vascular endothelia and embryonic stem cells (27)(28)(29)(30) and it was reported to promote anti-adhesive and migratory characteristics of various cancer cells except for pancreatic cancer (31)(32)(33)(34)(35). Recent studies showed that increased expression of PODXL is correlated with poor prognoses in many types of cancer (36)(37)(38)(39)(40)(41).…”

Podocalyxin-Targeting Comparative Glycan Profiling Reveals Difference between Human Embryonic Stem Cells and Embryonal Carcinoma Cells

“…Indeed, podocalyxin is characterized as a heavily glycosylated sialomucin. In recent years, it was reported that sialofucosylated podocalyxin-like protein is a selectin ligand on colon carcinoma or pancreatic cancer cells [57,58]. Therefore, these and the present findings on podocalyxin raise a A) Lectin microarray data were processed by a max-normalization procedure, and the resultant normalized data of representative lectin signals are shown as the formula "log2(hESC/hECC) for each lectin signal.…”