Targeted FGFR/VEGFR/PDGFR inhibition with dovitinib enhances the effects of nab-paclitaxel in preclinical gastric cancer models

Standard chemotherapy regimens for gastric adenocarcinoma (GAC) have limited efficacy and considerable toxicity profiles. Nab-paclitaxel has shown promising antitumor benefits in previous GAC preclinical studies. Dovitinib inhibits members of the receptor tyrosine kinase family including FGFR, VEGFR and PDGFR, and has exhibited antitumor effects in many solid tumors including GAC. Based on the antimitotic, antistromal and EPR effects of nab-paclitaxel, we investigated augmentation of nab-paclitaxel response by dovitinib in multiple GAC preclinical models. In MKN-45 subcutaneous xenografts, inhibition in tumor growth by nab-paclitaxel and dovitinib was 75% and 76%, respectively. Dovitinib plus nab-paclitaxel had an additive effect on tumor growth inhibition and resulted in tumor regression (85% of its original value). Dovitinib monotherapy resulted in minimal improvement in animal survival (25 days) compared to control (23 days), while nab-paclitaxel monotherapy or dovitinib plus nab-paclitaxel combination therapy led to a clinically significant lifespan extension of 83% (42 days) and 187% (66 days), respectively. IHC analysis of subcutaneous tumors exhibited reduced tumor cell proliferation and tumor vasculature by dovitinib. In vitro studies demonstrated that dovitinib and nab-paclitaxel individually reduced tumor cell proliferation, with an additive effect from combination therapy. Immunoblot analyses of MKN-45 and KATO-III cells revealed that dovitinib decreased phospho-FGFR, phospho-AKT, phospho-ERK, phospho-p70S6K, phospho-4EBP1, Bcl-2 and increased cleaved PARP-1, cleaved-caspase-3, p27, Bax, Bim, with an additive effect from combination therapy. These results demonstrate that the FGFR/VEGFR/PDGFR inhibitor, dovitinib, has the potential to augment the antitumor effects of nab-paclitaxel, with implications for use in the advancement of clinical GAC therapy.

Abstract 2208: Targeted inhibition of FGF/PDGF/VEGF signaling enhances nanoparticle taxane response in preclinical gastric cancer models

Background: Gastric adenocarcinoma (GAC) remains the third most common cause of cancer-related deaths worldwide. Most available systemic chemotherapy options for advanced GAC have limited efficacy. Nab-paclitaxel (NPT), a nanoparticle albumin-bound taxane formulation, has shown significant activity in preclinical GAC studies. Overexpression of multiple growth factors and their receptors such as FGF/FGFR, PDGF/PDGFR and VEGF/VEGFR, promote angiogenesis in several cancers including GAC that leads to tumor progression and metastasis. Dovitinib is a small molecule RTK inhibitor that potentially inhibits the activity of FGFR, PDGFR and VEGFR. We evaluated the antitumor efficacy of dovitinib and its ability to enhance nab-paclitaxel response in preclinical GAC models.

Methods: In vitro cell proliferation and protein expression were measured by WST-1 assay and Immunoblotting. In vivo tumor growth and animal survival studies were performed in NOD/SCID mice using human GAC MKN-45 cells.

Results: Nab-paclitaxel and dovitinib had in vitro growth inhibitory effect on several GAC associated cell lines tested, with additive effects in combination. Immunoblot analysis revealed that dovitinib treatment caused a decrease in the expression of phospho-FGFR, phospho-AKT, phospho-ERK; and an increase in the expression of apoptosis-related proteins cleaved PARP-1 and cleaved caspase-3. Nab-paclitaxel activity correlated with the increased expression of phospho-stathmin. In subcutaneous GAC xenografts, NPT and dovitinib demonstrated inhibition in tumor growth, while NPT+dovitinib had an additive effect. Net tumor growth was 533.7 mm3 in controls, 394.8 mm3 after oxaliplatin, 135.8 mm3 after NPT, 128 mm3 after dovitinib, 98.9 mm3 after oxaliplatin+dovitinib and -41.8 mm3 (tumor regression) after NPT+dovitinib. Tumor tissue analysis revealed that dovitinib reduced tumor vasculature, while nab-paclitaxel reduced tumor cell proliferation. In a peritoneal dissemination model, animal survival compared to controls (23 days) remained unchanged after monotherapy with oxaliplatin (24 days) or dovitinib (25 days) but increased significantly after NPT monotherapy (42 days, a 83% increase). Combination of dovitinib with NPT exhibited a further increase in animal survival (66 days, a 187% increase), while the combination of dovitinib with oxaliplatin had no survival benefit (25 days).

Conclusion: These findings demonstrate that the antitumor effect of nab-paclitaxel can be significantly enhanced by the FGFR/PDGFR/VEGFR pathway inhibitor dovitinib in preclinical GAC models. The data support the clinical relevance of this therapeutic combination for advanced GAC patients.

Citation Format: Niranjan Awasthi, Kate Crawford, Erin Bontrager, Sazzad Hassan, Urs von Holzen, Margaret A. Schwarz, Roderich E. Schwarz. Targeted inhibition of FGF/PDGF/VEGF signaling enhances nanoparticle taxane response in preclinical gastric cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2208.