Epithelial to mesenchymal transition (EMT) in human prostate cancer: lessons learned from ARCaP model

Abstract

Androgen refractory cancer of the prostate (ARCaP) cells contain androgen receptor (AR) and synthesize and secrete prostate specific antigen (PSA). We isolated epithelia-like ARCaP(E) from parental ARCaP cells and induced them to undergo epithelial-mesenchymal transition (EMT) by exposing these cells to soluble factors including TGFbeta1 plus EGF, IGF-1, beta2-microglobulin (beta2-m), or a bone microenvironment. The molecular and behavioral characteristics of the resultant ARCaP(M) were characterized extensively in comparison to the parental ARCaP(E) cells. In addition to expressing mesenchymal biomarkers, ARCaP(M) gained 100% incidence of bone metastasis. ARCaP(M) cells express receptor activator of NF-kappaB ligand (RANKL), which was shown to increase tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts in culture, and when metastatic to bone in vivo. We provide evidence that RANKL expression was promoted by increased cell signaling mediated by the activation of Stat3-Snail-LIV-1. RANKL expressed by ARCaP(M) cells is functional both in vitro and in vivo. The lesson we learned from the ARCaP model of EMT is that activation of a specific cell signaling pathway by soluble factors can lead to increased bone turnover, mediated by enhanced RANKL expression by tumor cells, which is implicated in the high incidence of prostate cancer bone colonization. The ARCaP EMT model is highly attractive for developing new therapeutic agents to treat prostate cancer bone metastasis.

Epidermal Growth Factor Promotes Protein Degradation of Epithelial Protein Lost in Neoplasm (EPLIN), a Putative Metastasis Suppressor, during Epithelial-mesenchymal Transition

“…Upon exposure to certain soluble factors or host bone microenvironment, low-invasive and epithelial-like ARCaP E cells undergo EMT and acquire invasive properties (26,27). Western blot analysis showed that both EGFR and neu (HER2/ ErbB2) were highly expressed and phosphorylated in ARCaP E cells and their highly metastatic, mesenchymal-like counterparts ARCaP M cells (Fig.…”

Hypoxia regulates ANXA1 expression to support prostate cancer cell invasion and aggressiveness

“…35 Therefore, we defined by Western Blot analysis the expression profiles of the proteins involved in EMT in normal and hypoxic conditions and their variations following ANXA1 downregulation. Our results showed a significant reversion of EMT process upon ANXA1 knock down in normoxia and hypoxia exposed PCa cells suggested by noteworthy E-cadherin enhancement and vimentin decrease (Fig.…”

Test Article

“…Furthermore, we found that recombinant 2-m protein could phosphorylate the Bcl-xL/Bcl-2-associated death-promoting protein, Bad, at Ser136 and Ser112 via activated PI3K/Akt and ERK signaling pathways in renal carcinoma SN12C cells [33]. Using a robust human prostate cancer EMT progression model, Zhau et al [63] from our group also showed that 2-m stably transfected ARCaP E prostate cancer cells had consistently activated STAT3, Snail, LIV-1, and overexpressed LIV-1 and receptor activator of nuclear factor kappa B ligand (RANKL)…”

“…Previous studies have supported the association of increased EMT with the ability of cancer cells to migrate, invade, and metastasize to the skeleton. 2-m also regulates cancer bone metastasis and confers cancer lethality through EMT by downregulation of E-cadherin and upregulation of N-cadherin, vimentin, and RANKL in solid tumors [34,63].…”