Vasculogenic Mimicry in Prostate Cancer: The Roles of EphA2 and PI3K

Abstract

BACKGROUND. Aggressive tumor cells can form perfusable networks that mimic normal vasculature and enhance tumor growth and metastasis. A number of molecular players have been implicated in such vasculogenic mimicry, among them the receptor tyrosine kinase EphA2, which is aberrantly expressed in aggressive tumors. Here we study the role and regulation of EphA2 in vasculogenic mimicry in prostate cancer where this phenomenon is still poorly understood.METHODS. Vasculogenic mimicry was characterized by tubules whose cellular lining was negative for the endothelial cell marker CD34 but positive for periodic acid-Schiff staining, and/or contained red blood cells. Vasculogenic mimicry was assessed in 92 clinical samples of prostate cancer and analyzed in more detail in three prostate cancer cell lines kept in three-dimensional culture. Tissue samples and cell lines were also assessed for total and phosphorylated levels of EphA2 and its potential regulator, Phosphoinositide 3-Kinase (PI3K). In addition, the role of EphA2 in vasculogenic mimicry and in cell migration and invasion were investigated by manipulating the levels of EphA2 through specific siRNAs. Furthermore, the role of PI3K in vasculogenic mimicry and in regulating EphA2 was tested by application of an inhibitor, LY294002.RESULTS. Immunohistochemistry of prostate cancers showed a significant correlation between vasculogenic mimicry and high expression levels of EphA2, high Gleason scores, advanced TNM stage, and the presence of lymph node and distant metastases. Likewise, two prostate cancer cell lines (PC3 and DU-145) formed vasculogenic networks on Matrigel and expressed high EphA2 levels, while one line (LNCaP) showed no vasculogenic networks and lower EphA2 levels. Specific silencing of EphA2 in PC3 and DU-145 cells decreased vasculogenic mimicry as well as cell migration and invasion. Furthermore, high expression levels of PI3K and EphA2 phosphorylation at Ser897 significantly correlated with the presence of vasculogenic mimicry and in vitro inhibition of PI3K by LY294002 disrupted vasculogenic mimicry, potentially through a reduction of EphA2 phosphorylation at Ser897.CONCLUSIONS. The expression levels of PI3K and EphA2 are positively correlated with vasculogenic mimicry both in vivo and in vitro. Moreover, phosphorylation levels of EphA2 regulated by PI3K are also significantly associated with vasculogenic mimicry in vivo. Based on its functional implication in vasculogenic mimicry in vitro, EphA2 signaling may be a potential therapeutic target in advanced prostate cancer.

Vasculogenic mimicry in bladder cancer and its association with the aberrant expression of ZEB1

“…In addition, VM is found in many solid tumors, including but not limited to the cancer mentioned above: Melanoma, hepatocellular carcinoma, colorectal and prostate cancer (4,6,8,10). Furthermore, there is a strong correlation between VM and malignant features of cancer, such as advanced stage or grade, poor differentiation and short overall survival.…”

“…The phenomenon has been observed in many tumor types, including hepatocellular carcinoma, breast, colorectal and prostate cancer (5)(6)(7)(8). Numerous studies (8)(9)(10) have shown that the existence of VM is closely related to the invasion, metastasis and poor prognosis of malignant tumors, which is significant in the clinic. At present, the literature about VM in bladder cancer, particularly its molecular mechanism, is very limited.…”

ZEB1‐mediated vasculogenic mimicry formation associates with epithelial–mesenchymal transition and cancer stem cell phenotypes in prostate cancer

“…The Src inhibitor PP2 was purchased from MedChemExpress (Trenton, NJ, USA) and dissolved in dimethyl sulfoxide (DMSO) and then used to treat cells at concentrations between 0 and 20 μmol/L, while cells treated with DMSO alone were used as controls …”

“…This assay was performed to assess the capacity of tumour cells to form VM as described previously . Briefly, we first coated 96‐well plates with growth factor‐reduced Matrigel (BD Biosciences, Bedford, MA) at 50 μL/well.…”

“…VM formation has been linked to an unfavourable outcome of various human cancers . In PCa, high levels of tumour tissue VM are associated with higher tumour Gleason score, TNM and metastasis . Thus, this study investigated the role and the potential contribution of ZEB1 in VM formation, EMT and CSC phenotypes in PCa tissues and the underlying molecular events in vitro.…”