Plexin-B3 Regulates Cellular Motility, Invasiveness, and Metastasis in Pancreatic Cancer

Abstract

The Plexins family of proteins are well-characterized transmembrane receptors of semaphorins, axon guidance cue molecules, that mediate the cell attraction or repelling effects for such cues. Plexins and their ligands are involved in numerous cellular activities, such as motility, invasion, and adhesion to the basement membrane. The detachment of cells and the gain in motility and invasion are hallmarks of the cancer metastasis cascade, thus generating interest in exploring the role of plexins in cancer metastasis. Semaphorin–plexin complexes can act as tumor promoters or suppressors, depending upon the cancer type, and are under investigation for therapeutic purposes. Our group has identified Semaphorin-5A (SEMA5A)/Plexin-B3 as an attractive targetable complex for pancreatic cancer (PC) metastasis. However, our understanding of the Plexin-B3 function and pathological expression in PC is limited, and our present study delineates the role of Plexin-B3 in PC malignancy. We examined the pathological expression of Plexin-B3 in PC tumors and metastasis using a human tissue microarray, disease progression model of PDX-Cre-Kras(G12D) (KC) mice, and different metastatic sites obtained from the KrasG12D; Trp53R172H; Pdx1-Cre (KPC) mice model. We observed a higher Plexin-B3 expression in PC tumor cores than the normal pancreas, and different metastatic sites were positive for Plexin-B3 expression. However, in the KC mice model, the Plexin-B3 expression increased initially and then decreased with the disease progression. Next, to evaluate the functional role of Plexin-B3, we utilized T3M-4- and CD18/HPAF-Control and -Plexin B3 knockdown cells for different in vivo and in vitro studies. The knockdown of Plexin-B3 enhanced the in vitro cellular migration, invasiveness, and impaired colony formation in three-dimensional culture, along with an increase in cellular spread and remodeling of the actin filaments. We also observed a higher metastasis in nude mice injected with T3M-4- and CD18/HPAF-shPlexin-B3 cells compared to their respective control cells. Furthermore, we observed a lower number of proliferating Ki-67-positive cells and higher ALDH1-A1-positive cells in the tumors formed by Plexin-B3 knockdown cells compared to tumors formed by the control cells. Together, our data suggest that the loss of Plexin-B3 is associated with the interference of cell division machinery and the induction of stem cell-like characteristics in PC cells.

Glycoproteomics Identifies Plexin-B3 as a Targetable Cell Surface Protein Required for the Growth and Invasion of Triple-Negative Breast Cancer Cells

“…Interestingly, it has been previously reported that PLXNB3 KD in pancreatic cancer negatively impacted cancer tumor growth in vivo while increasing cancer cell migration and metastasis. 58 We therefore conclude that PLXNB3's role is tumor-dependent and may be influenced by ligand interaction. The partner of interaction for PLXNB3 in TNBC is currently unknown.…”

“…Several reports indicate that PLXNB3 signaling is involved in actin cytoskeleton remodeling and cell motility. − We therefore investigated if PLXNB3 downregulation impacts TNBC cell migration. Cancer cells grown as spheroids can invade the extracellular matrix in which they are embedded .…”

Glycoproteomics Identifies Plexin-B3 as Targetable Cell Surface Protein Required for Growth and Invasion of Triple Negative Breast Cancer Cells

“…Prior reports and data mining indicate PLXNB3 is mostly absent from normal tissues, and its expression in adult tissues is restricted primarily to the central nervous system ( Figure 2C and Figures S2A/B ), making PLXNB3 an attractive target for novel therapies. PLXNB3 mutations have been described in breast cancer, pancreatic cancer, melanoma and prostate cancer (Liu et al, 2015; Saxena et al, 2021). In breast cancer, increased PLXNB3 mRNA expression was observed in moderately and poorly differentiated tumors compared to well-differentiated tumors (Malik et al, 2015).…”

“…Several reports indicate PLXNB3 signaling is involved in actin cytoskeleton remodeling and cell motility (Li et al, 2012; Li and Lee, 2010; Saxena et al, 2021). We therefore investigated if PLXNB3 downregulation impacts TNBC cell migration.…”

“…Subsequently we also employed the transwell cell migration assay (Justus et al, 2014) to measure cell motility and invasiveness toward a chemo-attractant gradient (FBS); once again we confirmed that PLXNB3 downregulation negatively impacts TNBC invasion and migration ( Figure S3E ). Interestingly, it has been previously reported that PLXNB3 KD in pancreatic cancer negatively impacted cancer tumor growth in vivo , while increasing cancer cell migration and metastasis (Saxena et al, 2021). We therefore conclude that PLXNB3’s role is tumor dependent and may be influenced by ligand interaction.…”