Abstract 2065: Biomarker-targeted novel combination for renal cell carcinoma

Abstract

Abstract INTRODUCTION: The survival of patients with metastatic renal cell carcinoma (mRCC) is < 10% at 5-years, despite treatment. Sorafenib (SF) is a second-line oral treatment which improves overall survival by 12-18%. However, mechanism for SF failure is not known. Hyaluronic acid (HA) promotes cell proliferation, invasion and motility through its receptors CD44 and RHAMM. Hymecromone (HC) is a non−toxic dietary supplement that inhibits HA synthesis and down regulates CD44 and RHAMM mRNA levels. In this study we examined the mechanism of SF resistance and the efficacy of HC+SF combination as a targeted therapy for advanced RCC. METHODS: HAS3 levels were measured in kidney specimens (normal=45; tumor= 86) by qPCR. HAS3 promoter was cloned and effect of SF and HC on HAS3 promoter activity was determined. Response of Vector-only (EV) or HAS3-overexpressing (HAS3) or HAS3-knockdown (HAS3-KO) transfectants of 786-O and Caki-1 cells, primary RCC spheroids and endothelial cells to SF+HC combination was examined in proliferation, apoptosis, motility and invasion assays. Immunoblotting was performed for target analysis. Treatment efficacy was evaluated in the Caki−1 subcutaneous (s.c.) and orthotopic xenograft models. RESULTS: HAS3 levels were 5-10-fold elevated in mRCC patients’ tumors as compared to non-mRCC patients and normal kidney tissues, respectively. HAS3 levels were an independent predictor of metastasis (P=0.043; sensitivity: 85.7%). Combination of SF (5 µM) with HC (20, 40 µg/mL) downregulated (>80%) HAS3 expression, HAS3 promoter activity and HA synthesis in RCC cells. HC+SF combination inhibited RCC cell and primary tumor spheroid proliferation > 90%, motility/invasion (>80%) and induced apoptosis (5-fold). While HAS3 transfectants were resistant to SF+HC treatment, HAS3-KO transfectants were sensitive to SF. HA addition also attenuated the effect of HC+SF observed in EV cells. Endothelial cells co-cultured with HAS3 transfectants were resistant to SF+HC treatment. SF+HC up-regulated apoptosis effectors, but downregulated CD44, RHAMM, and phospho-Met levels in EV but not in HAS3 transfectants. HC (100 or 200 mg/kg) and SF (30 mg/kg) oral combination abrogated Caki-1 tumor growth (>80%), without serum/tissue toxicity. HC+SF treatment decreased HAS3/HA levels, Ki67 index and microvessel density. HAS-overexpressing tumors were resistant to treatment. CONCLUSION: This is the first study to demonstrate that HAS3 overexpression in mRCC contributes to SF failure and that HAS3/HA downregulation is a mechanism to re-sensitize cells to SF. HC+SF is an orally bioavailable and non-toxic combination that may be an effective therapeutic strategy for mRCC. Citation Format: Jiaojiao Wang, Andre R. Jordan, Sarrah S. Lahorewala, Vinata B. Lokeshwar. Biomarker-targeted novel combination for renal cell carcinoma [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 2065.