Differential roles of mitogenic pathways in angiogenesis induced by PTHrP employing in vitro and in vivo models of colorectal cancer

NOVOA DIAZ, BELEN; CALVO, NATALIA; MARTÍN, MA. JULIA; CARRIERE, PEDRO; GENTILI, CLAUDIA

Mar del Plata

Congreso; LXIII reunion Anual De la Sociedad Argentina de Investigación Clínica; 2018

Parathyroid Hormone-related Peptide (PTHrP) is involved in various human cancers such as colorectal cancer where angiogenesis plays a critical role. In previous studies we observed that PTHrP stimulates the production of VEGF in Caco-2 and HCT 116 colon cancer cells which acts promoting the angiogenesis. The objective of the present work was to gain insight into the signaling events that link PTHrP to tumor angiogenesis studying the possible role of ERK1/2 MAPK and PI3K/AKT. qPCR assay and the use of the corresponding inhibitors revealed that PTHrP increases mRNA levels of the angiogenic factors VEGF, HIF-1α and MMP-9 in Caco-2 and HCT 116 cell lines via ERK1/2 and PI3K/AKT signaling pathways. Then, to determine if ERK1/2 and AKT mediate the angiogenic potential of colon cancer cells induced by PTHrP, we employed conditioned media from Caco-2 or HCT116 cells pretreated with the corresponding inhibitors, following with the incubation with the hormone. The inhibition of ERK1/2 and PI3K/AKT signaling pathways in colon cancer cells abrogated the stimulatory effects of Caco-2 and HCT 116 cells induced by PTHrP on endothelial HMEC-1 cell migration. According to the results obtained in vitro, we showed increased protein and mRNA levels of VEGF in nude mice xenografts of HCT116 cells by immunohistochemistry and qPCR analysis, respectively. Furthermore, we also observed that the localization of VEGF was near the nuclear membrane and cytoplasmic, suggesting also the possible involvement of this factor in an intracrine signaling. As previous studies revealed that PTHrP activates ERK 1/2 but not AKT in the in vivo model, these findings suggest that ERK1/2 is involved in tumor angiogenesis induced by PTHrP, while AKT may not participate in this process. This study clearly illustrate different responses according to the model used, reinforcing the importance of the use of in vivo models.