Intracellular EP2 prostanoid receptor promotes cancer-related phenotypes in PC3 cells

Abstract

Prostaglandin E2 (PGE2) and hypoxia-inducible factor-1α (HIF-1α) affect many mechanisms that have been involved in the pathogenesis of prostate cancer (PC). HIF-1α, which is up-regulated by PGE2 in LNCaP cells and PC3 cells, has been shown to contribute to metastasis and chemo-resistance of castrate-resistant PC (a lethal form of PC) and to promote in PC cells migration, invasion, angiogenesis and chemoresistance. The selective blockade of PGE2-EP2 signaling pathway in PC3 cells results in inhibition of cancer cell proliferation and invasion. PGE2 affects many mechanisms that have been shown to play a role in carcinogenesis such as proliferation, apoptosis, migration, invasion and angiogenesis. Recently, we have found in PC3 cells that most of these PGE2-induced cancer-related features are due to intracellular PGE2 (iPGE2). Here, we aimed to study in PC3 cells the role of iPGE2-intracellular EP2 (iEP2)-HIF-1α signaling in several events linked to PC progression using an experimental approach involving pharmacological inhibition of the prostaglandin uptake transporter and EGFR and pharmacological and genetic modulation of EP2 receptor and HIF-1α. We found that iPGE2 increases HIF-1α expression through iEP2-dependent EGFR transactivation and that inhibition of any of the axis iEP2-EGFR-HIF-1α in cells treated with PGE2 or EP2 agonist results in prevention of the increase in PC3 cell proliferation, adhesion, migration, invasion and angiogenesis in vitro. Of note, PGE2 induced EP2 antagonist-sensitive DNA synthesis in nuclei isolated from PC3 cells, which indicates that they have functional EP2 receptors. These results suggest that PGE2-EP2 dependent intracrine mechanisms involving EGFR and HIF-1α play a role in PC.

Host knockout of E-prostanoid 2 receptors reduces tumor growth and causes major alterations of gene expression in prostaglandin E2-producing tumors

“…Hif1a was 1.83-fold upregulated in the knockout mice, even when the tumors were small. A previous study reported that HIF-1α is upregulated by PGE 2 , contributing to metastasis and chemoresistance, as well as the promotion of prostate cancer cell migration, invasion and angiogenesis (31). Mmps degrade extracellular matrix and facilitate the migration of tumor cells.…”

Intracrine prostaglandin E2 pro‐tumoral actions in prostate epithelial cells originate from non‐canonical pathways

“…The effects of PGE 2 on non‐transformed prostate epithelial cells are currently unknown, despite they may be relevant in non‐malignant proliferative diseases of the prostate associated with chronic inflammation of the prostate such are BPH or proliferative inflammatory atrophy (Bardan, Dumache, Dema, Cumpanas, & Bucuras, ; Thapa & Ghosh, ). Here we found in immortalized, non‐malignant prostate epithelial RWPE‐1 cells that PGE 2 , again through the axis iPGE 2 ‐iEP receptors‐EGFR‐HIF‐1α, inhibits cell adhesion and stimulates cell proliferation, migration and in vitro angiogenesis (i.e., the same effects than in PC3 cells (Fernández‐Martínez & Lucio‐Cazaña, ; Madrigal‐Martínez et al, )). Since iPGE 2 mediates the growth‐stimulating effects of PGE 2 on prostate epithelial cells, regardless they are benign or malign ones, the pharmacological inhibition of PGT could be a novel therapeutic approach to treat prostate proliferative diseases associated with chronic inflammation.…”

“…It is generally accepted that the biological actions of PGE 2 are mediated by plasma membrane G protein‐coupled EP receptors which are located at the cell membrane. However, we have found that PGE 2 has to reach the intracellular compartment and activate a subset of EP receptors, which is located intracellularly, as a prerequisite for being effective in PC3 cells (Fernández‐Martínez & Lucio‐Cazaña, ; Madrigal‐Martínez et al, ). This is a non‐canonical intracrine mechanism of PGE 2 action for which the energetically active influx of PGE 2 (accounting for almost 100% of PGE 2 internalization), is mediated by the prostaglandin transporter (PGT), a member of the organic anion transporter family (Nomura, Lu, Pucci, & Schuster, ; Schuster, ).…”

“…This is a non‐canonical intracrine mechanism of PGE 2 action for which the energetically active influx of PGE 2 (accounting for almost 100% of PGE 2 internalization), is mediated by the prostaglandin transporter (PGT), a member of the organic anion transporter family (Nomura, Lu, Pucci, & Schuster, ; Schuster, ). Once PGE 2 is internalized in PC3 cells and becomes intracellular PGE 2 (iPGE 2 ), it inhibits cell adhesion and stimulates cell proliferation, migration and in vitro angiogenesis (Fernández‐Martínez & Lucio‐Cazaña, ; Madrigal‐Martínez et al, ). The mechanism involves transactivation of epidermal growth factor‐receptor (EGFR) by iEP, leading to increased expression and activity of hypoxia‐inducible factor‐1α (HIF‐1α) (Fernández‐Martínez & Lucio‐Cazaña, ).…”

“…Once PGE 2 is internalized in PC3 cells and becomes intracellular PGE 2 (iPGE 2 ), it inhibits cell adhesion and stimulates cell proliferation, migration and in vitro angiogenesis (Fernández‐Martínez & Lucio‐Cazaña, ; Madrigal‐Martínez et al, ). The mechanism involves transactivation of epidermal growth factor‐receptor (EGFR) by iEP, leading to increased expression and activity of hypoxia‐inducible factor‐1α (HIF‐1α) (Fernández‐Martínez & Lucio‐Cazaña, ).…”