Abstract 5214: HYAL4 splice variant induces treatment-resistance in advanced bladder cancer
Authors: Aguilar Karina , Panda Sunita , Van Der Eerden Joshua , Lopez Luis , Terris Martha , Santamaria Pablo , Lokeshwar Bal , Lokeshwar Vinata B. 
Published: March 2024

Introduction and Objective: Precision-based treatment approaches could improve the prognosis of patients with bladder cancer (BC). We recently discovered a first-in-class human Chondroitinase (Chase) that degrades chondroitin sulfate. This Chase is a splice variant of HYAL4 (V1) and promotes a malignant phenotype and chemoresistance in BC cells. We evaluated V1/Chase expression and functions in BC and inhibitors to overcome V1/Chase-mediated Gemcitabine (Gem) resistance.

Methods: Cohort 1: 653 voided urine specimens (BC, 160; non-BC, 493); cohort 2: 40 cystectomy specimens from MIBC patients who received adjuvant Gemcitabine plus cisplatin (G+C) treatment. Gene expression was measured by q-PCR and urine was assayed by the Chase test. V1 was expressed in BC cell lines or silenced and the transfectants were analyzed for sensitivity to Gem and Cisplatin. The mechanism of Gem resistance was evaluated in preclinical in vitro and in vivo models.

Results: In cohort 1, Chase levels were 7-10-fold elevated in patients with BC compared to patients with benign genitourinary conditions, history of BC, or other cancers. Chase test detected BC with 94.4% and 87.4% specificity. Chase test had 84% accuracy in correctly diagnosing the cases with atypical cytology inference. Stem cell marker CD44 was the major substrate of Chase in BC cells. V1’s Chase activity induced CD44 cleavage and shedding. Intracellularly, CD44 cleavage induced JAK2/Stat3 pathway and subsequently upregulation of cytidine deaminase. CDA induces Gem metabolism and efflux of dFdU, an inactive Gem metabolite. HPLC analysis showed, V1 transfectants have increased levels of dFdU and higher efflux. STAT3 and CDA inhibitors synergistically re-sensitized V1-expressing cells to Gem. In cohort 2, V1, p-JAK2 and CDA expression predicted failure to G+C treatment (P&lt;0.0001). JAK2, STAT3 and CDA inhibitors synergistically re-sensitized V1-expressing cells to Gem. V1-induced muscle invasive tumors that were metastatic. While V1-expressing tumors were resistant, combination of Gem with a CDA or JAK-2 inhibitor abrogated V1 tumor growth with minimal toxicity.

Conclusion: V1/Chase is a potential diagnostic and prognostic biomarker for bladder cancer and drives muscle-invasion, metastasis, and Gem resistance in BC. Inhibitors of the Chase signaling pathway overcome V1-induced Gem resistance, suggesting a precision-based treatment approach to improve treatment response.

Support: 1R01CA227277-05A1; 1R01CA283699-01

Citation Format: Karina Aguilar, Sunita Panda, Joshua Van Der Eerden, Luis Lopez, Martha Terris, Pablo Santamaria, Bal Lokeshwar, Vinata B. Lokeshwar. HYAL4 splice variant induces treatment-resistance in advanced bladder cancer [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 5214.