RSK activation via ERK modulates human colon cancer cells response to PTHrP

Abstract

Parathyroid hormone-related peptide (PTHrP) is associated with several human cancers such as colon carcinoma. This disease is a complex multistep process that involves enhanced cell cycle progression and migration. Recently we obtained evidence that in the human colorectal adenocarcinoma Caco2 cells, exogenous PTHrP increases the proliferation and positively modulates cell cycle progression via ERK1/2, p38 MAPK and PI3K. The purpose of this study was to explore if the serine/threonine kinase RSK, which is involved in the progress of many cancers and it is emerging as a potential therapeutic target, mediates PTHrP effects on cancer colon cells. Western blot analysis revealed that PTHrP increases RSK phosphorylation via ERK1/2 signaling pathway but not through p38 MAPK. By performing subcellular fractionation, we found that the peptide also induces the nuclear localization of activated RSK, where many of its substrates are located. RSK participates in cell proliferation, in the upregulation of cyclin D1 and CDK6 and in the downregulation of p53 induced by PTHrP. Wound healing and transwell filter assays revealed that cell migration increased after PTHrP treatment. In addition, the hormone increases the protein expression of the focal adhesion kinase FAK, a regulator of cell motility. We observed that PTHrP induces cell migration and modulates FAK protein expression through ERK/RSK signaling pathway but not via p38 MAPK pathway. Finally, studies revealed that the hormone activates RSK in xenografts tumor. Taken together, our findings provide new insights into the deregulated cell cycle and migration that is characteristic of tumor intestinal cells.

Potential therapeutic targets for growth arrest of colorectal cancer cells exposed to PTHrP

“…We previously showed that in both, Caco-2 cells and HCT116 cells, PTH1R is expressed and that exogenous PTHrP modulates cell cycle progression and exerts proliferative and protective effects via MAPKs and PI3-kinase/Akt signaling pathways (Calvo et al, 2014;Lezcano et al, 2013;Martín et al, 2014). More recently, we obtained evidence that in both cell lines PTHrP induces cell migration via RSK/ERK1/2 signaling pathway but not through p38 MAPK; also the peptide increases the expression of the active form of RSK in HCT116 tumor xenografts (Calvo et al, 2017). In view of the effects of PTHrP in vivo, the first objective of this work was to evaluate whether the hormone modulates the expression of other molecular markers related to tumorigenic events in CRC tumor xenografts.…”

“…The activation of ERK1/2 signaling is very common in colon cancer and is vital for the growth of CRC cells (Cheruku et al, 2015;Setia et al, 2014), We previously observed that PTHrP stimulates cell proliferation and cell cycle progression through ERK MAPK in tumor intestinal cells (Martín et al, 2014;Calvo et al, 2014). Moreover, our recent studies revealed that PTHrP can promote cell migration through RSK/ERK MAPK in Caco-2 cells and HCT116 cells (Calvo et al, 2017). Since we also detected ERK activation in vivo, then our next goal was to investigate signal transduction pathways through which PTHrP triggers ERK 1/2 MAPK activation in Caco-2 cells and HCT116 cells.…”

“…Mice were administered daily with PTHrP (40 μg/kg in 100ul PBS), or an equal volume of vehicle solution, as control, by intratumoral injection (2 groups in total; each group represents an experimental unit). We selected this dose of the peptide based in previous studies performed by us and by other investigators with PTH and/or PTHrP in rodents (Frolik et al, 1999;Stewart et al, 2000;Zhou et al, 2003;Calvo et al, 2017). The mice were sacrificed and tumors were removed and weighted after 20 days of PTHrP treatment.…”

“…Recently, we obtained evidence that PTHrP induces the activation of RSK in HCT116 tumor xenografts. Since in vitro the peptide activates RSK via ERK1/2 signaling pathway but not through p38 MAPK in HCT116 cell line (Calvo et al, 2017), therefore our first objective was to investigate whether the hormone also modulates the expression of other molecular markers related to tumorigenic events (such as MAPKs) in CRC tumor tissues. Immunohistochemistry analysis of these tumor xenografts showed increased immunoreactivity scores of active ERK 1/2 and total ERK 1/2 in tumors treated with PTHrP respect to the levels observed in tumor treated with PBS, which is the vehicle of the hormone ( Fig.…”

Implication of myeloid differentiation factor 88 inhibitor TJ‐M2010‐5 for therapeutic intervention of hepatocellular carcinoma

“…e). In addition, GSK3β (Ser9) was reported as crucial for promoting cell proliferation and was associated with the Erk/MAPK signaling pathway . Along with the downregulation of the phosphorylation of RSK, the expression of phosphorylated GSK3β was also downregulated by TJ‐M2010‐5 (Fig.…”