Podocalyxin-like 1 promotes invadopodia formation and metastasis through activation of Rac1/Cdc42/cortactin signaling in breast cancer cells

Abstract

Metastatic disease is the leading cause of cancer mortality. Identifying biomarkers and regulatory mechanisms is important toward developing diagnostic and therapeutic tools against metastatic cancer. In this study, we demonstrated that podocalyxin-like 1 (PODXL) is overexpressed in breast tumor cells and increased in lymph node metastatic cancer. Mechanistically, we found that the expression of PODXL was associated with cell motility and invasiveness. Suppression of PODXL in MDA-MB-231 cells reduced lamellipodia formation and focal adhesion kinase (FAK) and paxillin phosphorylation. PODXL knockdown reduced the formation of invadopodia, such as inhibiting the colocalization of F-actin with cortactin and suppressing phosphorylation of cortactin and neural Wiskott-Aldrich syndrome protein. Conversely, overexpression of PODXL in MCF7 cells induced F-actin/cortactin colocalization and enhanced invadopodia formation and activation. Invadopodia activity and tumor invasion in PODXL-knockdown cells are similar to that in cortactin-knockdown cells. We further found that the DTHL motif in PODXL is crucial for regulating cortactin phosphorylation and Rac1/Cdc42 activation. Inhibition of Rac1/Cdc42 impeded PODXL-mediated cortactin activation and FAK and paxillin phosphorylation. Moreover, inhibition of PODXL in MDA-MB-231 cells significantly suppressed tumor colonization in the lungs and distant metastases, similar to those in cortactin-knockdown cells. These findings show that overexpression of PODXL enhanced invadopodia formation and tumor metastasis by inducing Rac1/Cdc42/cortactin signaling network.

miR-142 acts as a tumor suppressor in osteosarcoma cell lines by targeting Rac1

“…It was reported that lower miR-142 expression in hepatocellular carcinoma was significantly associated with poor survival (17). Rac1 expression is frequently upregulated in several types of cancers, including hepatic cancer (14) and breast cancer (20). In line with previous studies, in the present study, we also found that miR-142 was downregulated, while Rac1 was upregulated in 6 osteosarcoma tissue samples compared with the paired normal bone tissues.…”

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).…”

Rac1 is correlated with aggressiveness and a potential therapeutic target for gastric cancer

“…Studies from diverse types of cancers have suggested the essential role of Rac1 in regulating tumor metastasis. Rac1 can be activated by multiple upstream signals and induce invadopodia formation and cause metastasis in breast cancer (15). Activated Rac1 promotes the assembly of cell surface integrin protein molecules in the surface of the head of the cells and passes regulative signals to the actin cytoskeleton, thus, inducing actin filaments to aggregate in the plasma membrane and form sheets of pseudopodia, leading to cell membrane multipolarization, which eventually affects the movement of cell migration.…”

“…Although Rac1 as a cytoskeleton organizer has been documented well, more and more recent findings provoked broad functions of Rac1 in human cancers. Rac1 regulates a diverse spectrum of cellular functions including tumorigenesis (11), angiogenesis (12,13) and metastasis (11,14,15). Overexpression of Rac1 occurs in several different types of tumors including breast (16,17), colon (18), bladder (19), and gastric cancer (20,21).…”

“…Overexpression of Rac1 occurs in several different types of tumors including breast (16,17), colon (18), bladder (19), and gastric cancer (20,21). Rac1 overexpression was observed in metastatic gastric (21), breast (15), prostate (22), bladder upper urinary tract cancer (19). Rac1 promoted prostate cancer progression and recurrence upon activation by VAV3, a GEF for Rac1 activation (14).…”