Abstract 3283: Role of HA, HAS3, UGT1A9 in metastatic renal cell carcinoma and sorafenib resistance
Authors: Sharma Anuj Kumar , Aguilar Karina , Panda Chandramukhi S. , Lokeshwar Vinata B. 
Published: March 2024

Introduction: Despite numerous available treatments, metastatic renal cell carcinoma (mRCC) remains highly lethal, with over 90% of patients succumbing within 5 years. Sorafenib (SF), a second-line treatment for mRCC, exhibits modest efficacy, and the underlying molecular basis for its failure is elusive. Hyaluronic acid (HA), implicated in promoting cell proliferation, invasion, and motility through CD44 and RHAMM receptors, represents a potential player in SF resistance. Hymecromone (HC), a non-toxic dietary supplement, is known to inhibit HA synthesis and downregulate CD44 and RHAMM mRNA levels. This study investigates the elusive mechanisms of SF resistance and evaluates the effectiveness of the HC+SF combination as a targeted therapy for advanced RCC, providing insights into a novel and potentially impactful treatment approach.

Methods: HA levels were measured in normal and tumor kidney specimens using ELISA-like assay and IHC. Similarly, HAS3 and UGT1A9 (A9) levels and SF glucuronidation were measured by qPCR and a glucuronidation assay using tumor microsomes. Response to SF+HC combination was examined in A9 and HAS3 knockdown and overexpression cell lines (transfectants) and primary RCC spheroids by proliferation, apoptosis, motility, and invasion assays. Target analysis was performed by immunoblot. Treatment efficacy was evaluated in subcutaneous and orthotopic xenograft mouse models, with bioluminescence imaging.

Results: SF failure in mRCC was linked due to its glucuronidation and inactivation by A9. Tumor microsomes from patients who developed mRCC glucuronidated SF 5-fold higher than from non-mRCC patients. A9 levels were elevated (8-10 folds) in mRCC patients’ tumor along with HA and HAS3 (5-10 folds) as compared to non-mRCC patients and normal kidney tissues. HC treatment downregulated A9 promoter activity and inhibited SF-glucuronidation in RCC cells. SF (5uM) and HC (20, 40ug/ml) combination inhibited RCC cell and primary tumor spheroid proliferation (&gt;90%), motility/invasion (&gt;80%), and induced apoptosis (5-fold) and downregulated HAS3 expression (&gt;80%), and HA synthesis in RCC cells. While A9 and HAS3 transfectants both were resistant to SF+HC treatment, A9 and HAS3 - KO transfectants were sensitive to SF. Endothelial cells co-cultured with either A9 or HAS3 transfectants were resistant to SF+HC treatment. SF+HC upregulated apoptosis effectors, but downregulated CD44, RHAMM, and phospho-Met levels in EV but not in A9 or HAS3 transfectants. HC (100 or 200mg/kg) and SF (30mg/kg) oral combination abrogated Caki-1 tumor growth (&gt;80%), without serum/tissue toxicity. HC+SF treatment decreased A9, HA and HAS3 levels, Ki67 index and microvessel density. Both A9 and HAS3 overexpressing tumors were resistant to treatment.

Conclusion: This study demonstrates the mechanism of SF failure in mRCC and proposes a safe, oral adjunct combination for effective treatment.

Citation Format: Anuj Kumar Sharma, Karina Aguilar, Chandramukhi S. Panda, Vinata B. Lokeshwar. Role of HA, HAS3, UGT1A9 in metastatic renal cell carcinoma and sorafenib resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3283.