2ⁿᵈ Edition of the Cancer R&D World Conference 2026

Abstract

Background: Immune checkpoint inhibitors (ICIs) have revolutionized melanoma treatment, yet about 55% of patients exhibit innate resistance. To address this, we proposed combining novel melanoma leads 2155-14 and 2155-18 with ICIs to enhance efficacy and immunogenicity. We previously demonstrated that downregulating hnRNP H1/H2 with 2155-14 and 2155-18 induces ER stress, autophagy, apoptosis, type I IFN signaling, and triggers both innate and adaptive immune responses in vivo. However, the mechanisms by which these compounds induce cell death in melanoma cells remain unclear. This presentation focuses on understanding the pathways targeted by 2155-14 and 2155-18 and their immunomodulatory effects in vitro, providing insights for potential combination with ICIs to overcome innate resistance.

Methods: To determine compounds’ mechanism of action, we performed immunocytochemistry and immunohistochemistry across multiple cell types, including BRAF-mutant, NRAS-mutant, and triple wild-type melanoma, prostate cancer, and embryonic kidney cells, to examine double-stranded RNA (dsRNA) expression. Western blotting probed common pattern recognition receptors (PRRs), including the OAS family, MDA5, and RIG-I, and protein kinase R (PKR), to determine whether dsRNA accumulation induced by the compounds activates or upregulates dsRNA sensors. Finally, we used multiplex cytokine assays to assess immune responses following treatment.

Results: Both 2155-14 and 2155-18 significantly induced dsRNA accumulation through hnRNP H1/H2 downregulation, disrupting normal splicing of pre-mRNA. This increased dsRNA accumulation mimicked a viral infection, upregulating OAS-family and PKR dsRNA sensors, ultimately leading to cell cycle arrest, apoptosis, and NF-κB activation, increased cytokine production, and triggered innate and adaptive immune responses in vivo.

Conclusions: Treatment with spliceosomal modulators induces signaling via multiple pathways, ultimately resulting in pro-inflammatory cytokine and interleukin signaling and melanoma cell death.