Involvement of Notch system and PDGFB in Ovarian Cancer Stem Cells sub-population

BECHIS, A.; IRUSTA, G.; PAZOS C; BUCKANOVICH, R.; TESONE, M.

Congreso; LVI Reunión Anual de la Sociedad Argentina de Investigación Clinica; 2016

Ovarian cancer remains one of the most lethal gynecologic cancers, in part due to a regenerative tumor cell sub-population that acquired stem cell properties. Notch and PDGF systems are involved in proliferation, apoptotic and angiogenic processes. To assess the rol of these systems in oncogenic stem cell properties, we incubated two epithelial ovarian cancer cell lines (SKOV3 and HEY1) in the presence of a gamma-secretasa inhibitor, DAPT (20uM), recombinant-PDGFB (10ng/ml), DAPT+rec-PDGFB and in the absence of stimulus (Control). We determined ovarian oncogenic stem cell markers by flow citometry (CD133, CD44 and ALDH activity), and the capability of these cell lines to form spheres. A xenograft model in female SCID mice was developed using SKOV3 cells. During 4 consecutive days, mice received 1.DMSO 20% (Control), 2.A gamma-secretase inhibitor (DBZ, 1mg/ml/d), 3.rec-PDGFB (25ug/ml/d) and 4.DBZ+PDGFB. Animals were sacrificed 2 days post-treatment. The in vitro studies showed a decrease of the stem cell population in both cell lines when incubated with DAPT. The incubation with DAPT, PDGFB, or both, significantly decreased the number of spheres formed by cells. In vivo treatment with DBZ or DBZ+PDGFB significantly decreased tumor weight and growth compared to the control group. No differences were found between Control and PDGFB treatments. Also, DBZ, PDGFB, or DBZ+PDGFB significantly decreased the tumor stem cell pool. Tumor proliferation (Ki67 levels) significantly decreased and cellular apoptosis (cleaved Caspase-3 staining) slightly increased with DBZ and significantly increased with DBZ+PDGFB co-treatment. Also endothelial area increased with DBZ and DBZ+PDGFB co-treatment. In conclusion we demonstrate that Notch system is involved in ovarian cancer stem cell properties and also ovarian tumor stem cell content. The administration of PDGFB cooperates with gamma secretase inhibitor action on tumors intensifying the inhibitor antitumor effect.