Prostaglandin E2 Activates YAP and a Positive-Signaling Loop to Promote Colon Regeneration After Colitis but Also Carcinogenesis in Mice

Abstract

BACKGROUND & AIMS Prostaglandin E2 (PGE2) is mediator of inflammation that regulates tissue regeneration, but its continual activation has been associated with carcinogenesis. Little is known about factors in the PGE2 signaling pathway that contribute to tumor formation. We investigated whether yes associated protein 1 (YAP1), a transcriptional co-activator in the Hippo signaling pathway, mediates PGE2 function. METHODS DLD-1 and SW480 colon cancer cell lines were transfected with vectors expressing transgenes or small hairpin RNAs and incubated with recombinant PGE2, with or without pharmacologic inhibitors of signaling proteins, and analyzed by immunoblot, immunofluorescence, quantitative reverse transcription PCR, transcriptional reporter, and proliferation assays. Dextran sodium sulfate (DSS) was given to induce colitis in C57/BL6 (control) mice, as well as in mice with disruption of the hydroxyprostaglandin dehydrogenase 15 gene (15-PGDH-knockout mice), Yap1 gene (YAP-knockout mice), and double knockout mice. Some mice were also given indomethacin to block PGE2 synthesis. 15-PGDH knockout mice were crossed with mice with intestine-specific disruption of the Salvador family WW domain containing 1 gene (Sav1), which encodes an activator of Hippo signaling. We performed immunohistochemical analyses of colon biopsy samples from 26 patients with colitis-associated cancer and 51 age- and sex-matched patients with colorectal cancer (without colitis). RESULTS Incubation of colon cancer cell lines with PGE2 led to phosphorylation of cAMP responsive element binding protein 1 (CREB1) and increased levels of YAP1 mRNA and protein and YAP1’s transcriptional activity. This led to increased transcription of the prostaglandin-endoperoxide synthase 2 gene (PTGS2 or COX2) and prostaglandin E receptor 4 gene (PTGER4 or EP4). Incubation with PGE2 promoted proliferation of colon cancer cell lines, but not cells with knockdown of YAP1. Control mice developed colitis after administration of DSS, but injection of PGE2 led to colon regeneration in these mice. However, YAP-knockout mice did not regenerate colon tissues and died soon after administration of DSS. 15-PGDH-knockout mice regenerated colon tissues more rapidly than control mice after withdrawal of DSS, and had faster recovery of body weight, colon length, and colitis histology scores. These effects were reversed by injection of indomethacin. SAV1 -knockout or 15-PDGH-knockout mice did not develop spontaneous tumors following colitis induction, but SAV1/15-PDGH double knockout mice developed polyps that eventually progressed to carcinoma in situ. Administration of indomethacin to these mice prevented spontaneous tumor formation. Levels of PGE2 correlated with those of YAP levels in human sporadic colorectal tumors and colitis-associated tumors. Conclusion PGE2 signaling increases expression and transcriptional activities of YAP1, leading to increased expression of COX2 and EP4 to activate a positive signaling loop. This pathway promotes proliferation of colon cancer...

YAP Inhibits the Apoptosis and Migration of Human Rectal Cancer Cells via Suppression of JNK-Drp1-Mitochondrial Fission-HtrA2/Omi Pathways

“…In fact, a growing body of research has suggested that Yap nuclear translocation is unlikely to fully explain the role of Yap in cancer development [50, 51] and that Yap nuclear localization accounts for only a small portion of cancer progression [22]. Additionally, several studies have confirmed that the mRNA levels of Yap (and TAZ) sufciently correlate with target gene expression and are significantly associated with cancer progression [7, 23]. Meanwhile, an increasing number of studies have also shown that Yap has the ability to interact with tumor suppressors in the cytoplasm [52], supporting the idea that excessive expression of Yap is actually a more important factor in tumorigenesis regardless of Yap nuclear localization or cytoplasmic retention [7, 8].…”

“…Additionally, several studies have confirmed that the mRNA levels of Yap (and TAZ) sufciently correlate with target gene expression and are significantly associated with cancer progression [7, 23]. Meanwhile, an increasing number of studies have also shown that Yap has the ability to interact with tumor suppressors in the cytoplasm [52], supporting the idea that excessive expression of Yap is actually a more important factor in tumorigenesis regardless of Yap nuclear localization or cytoplasmic retention [7, 8]. …”

“…These malignancies are ascribed to accumulation of protein alterations, including dissemination of proto-oncogenes and loss or inactivation of tumor suppressor genes, which ultimately lead to tumor evolution and progression [2-6]. Furthermore, the increased survival and invasiveness of tumor cells are typical characteristics of RC [7, 8], suggesting a clinical need to abate excessive RC cell survival and migration.…”

“…These findings hint that Yap may be involved in RC development. Regulation of Yap phosphorylation in more aggressive cancers has been studied extensively, and increased levels of Yap (and TAZ) correlate with cancer progression [7, 23]. Moreover, much of the immunohistochemistry and microarray data from cancer specimens show elevated total Yap abundance rather than focused nuclear localization of Yap [22, 23], suggesting the important role of Yap in the cytoplasm.…”

A comprehensive anticancer molecular study for genistein the promising anticancer drug

“…PTGS2 is a key step in the production of prostaglandin E2 (PGE2) in cancer cells, which plays important roles in modulating motility, proliferation and resistance to apoptosis. 25 This down-regulation was found in ADME, signal transduction, cardiovascular disease and inflammation families.…”