c-Met inhibitors attenuate tumor growth of small cell hypercalcemic ovarian carcinoma (SCCOHT) populations

// Anna Otte 1 , Finn Rauprich 1 , Juliane von der Ohe 1 , Yuanyuan Yang 1 , Friedrich Kommoss 2 , Friedrich Feuerhake 3 , Peter Hillemanns 1 , Ralf Hass 1 1 Biochemistry and Tumor Biology Laboratory, Department of Obstetrics and Gynecology, Hannover Medical School, Hannover, Germany 2 Synlab MVZ Pathologie Mannheim GmbH, Referral Center for Gynecopathology, Mannheim, Germany 3 Institute for Pathology, Hannover Medical School, Hannover, Germany Correspondence to: Ralf Hass, e-mail: hass.ralf@mh-hannover.de Keywords: SCCOHT, small cell ovarian cancer, c-Met inhibitor, foretinib, tumor growth Received: February 16, 2015      Accepted: August 12, 2015      Published: September 30, 2015 ABSTRACT A cellular model (SCCOHT-1) of the aggressive small cell hypercalcemic ovarian carcinoma demonstrated constitutive chemokine and growth factor production including HGF. A simultaneous presence of c-Met in 41% SCCOHT-1 cells suggested an autocrine growth mechanism. Expression of c-Met was also observed at low levels in the corresponding BIN-67 cell line (6.5%) and at high levels in ovarian adenocarcinoma cells (NIH:OVCAR-3 (84.4%) and SK-OV-3 (99.3%)). Immunohistochemistry of c-Met expression in SCCOHT tumors revealed a heterogeneous distribution between undetectable levels and 80%. Further characterization of SCCOHT-1 and BIN-67 cells by cell surface markers including CD90 and EpCAM demonstrated similar patterns with differences to the ovarian adenocarcinoma cells. HGF stimulation of SCCOHT-1 cells was associated with c-Met phosphorylation at Tyr 1349 and downstream Thr 202 /Tyr 204 phosphorylation of p44/42 MAP kinase. This HGF-induced signaling cascade was abolished by the c-Met inhibitor foretinib. Cell cycle analysis after foretinib treatment demonstrated enhanced G2 accumulation and increasing apoptosis within 72 h. Moreover, the IC 50 of foretinib revealed 12.4 nM in SCCOHT-1 cells compared to 411 nM and 481 nM in NIH:OVCAR-3 and SK-OV-3 cells, respectively, suggesting potential therapeutic effects. Indeed, SCCOHT-1 and BIN-67 tumor xenografts in NOD scid mice exhibited an approximately 10-fold and 5-fold reduced tumor size following systemic application of foretinib, respectively. Furthermore, foretinib-treated tumors revealed a significantly reduced vascularization and little if any c-Met-mediated signal transduction. Similar findings of reduced proliferative capacity and declined tumor size were observed after siRNA-mediated c-Met knock-down in SCCOHT-1 cells demonstrating that in vivo inhibition of these pathways contributed to an attenuation of SCCOHT tumor growth.