CysLT₁ antagonist, 1,4-dihydroxy quininib, alters the secretion of inflammatory mediators from primary uveal melanoma explants and reduces ATP5B expression in a metastatic xenograft model.

Abstract

Purpose : Uveal melanoma (UM) is a rare, but often lethal, ocular cancer which metastasises to the liver in up to 50% of patients. There are no effective therapies available to treat metastatic UM and as few as 8% of patients survive beyond two years. We previously identified that high expression of CysLT₁ is associated with poor UM patient outcomes in a UK cohort, and that CysLT₁ antagonists alter the tumorigenic properties of UM cell lines in vitro. This preclinical in vivo and ex vivo research further evaluates the clinical relevance and therapeutic potential of CysLT receptors in UM.

Methods : Immunohistochemical staining was conducted on an independent, primary UM patient cohort from Spain (n=68) to analyse expression of CysLT receptors and their relationship to matched survival data. Primary UM tumours (n=11) were grown as explant cultures and treated with 20 μM 1,4-dihydroxy quininib or vehicle. Following 72 hours of treatment, tumour conditioned media was analysed by ELISA and the secretion of factors was correlated to clinical data. An orthotopic cell line-derived xenograft model of metastatic UM was generated in female athymic Nude-Foxn1nu mice using OMM2.5 metastatic UM cells. 1,4-dihydroxy quininib was administered intraperitoneally at a dose of 25 mg/kg every 3 days, for 3 weeks (n=8). Upon sacrifice, tumour weight was compared to vehicle (n=9) and Dacarbazine (80 mg/kg)(n=8) treated mice and tumours were assessed by immunohistochemistry and digital pathology analysis.

Results : We confirmed that high expression of CysLT₁ in primary UM is significantly associated with reduced survival in an independent, validation cohort (p=0.01). Treatment of ex vivo explants derived with 1,4-dihydroxy quininib significantly alters the secretion of IL-13, IL-2 and TNF-α. In an orthotopic xenograft model of metastatic UM, treatment with 1,4-dihydroxy quininib did not significantly decrease tumour weight versus vehicle (p=0.81) but did significantly decreases ATP5B (p=0.03), a marker of oxidative phosphorylation, versus vehicle, mimicking our published in vitro data.

Conclusions : These preclinical data strengthen the importance of CysLT signalling in UM. Our findings suggest that high expression of CysLT₁ in UM could act as a biomarker for poor prognosis and that antagonism of CysLT₁ may be of therapeutic interest in UM.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.