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

Abstract

Melanoma remains the deadliest form of skin cancer. Because elevated expression of splicing proteins Heterogeneous Nuclear Ribonucleoproteins H1 and H2 (H1/H2) correlates with poor prognosis, we patented small-molecule H1/H2 inhibitors, 2155-14 and 2155-18. Preliminary in vitro and in vivo data suggest that treating melanoma cells with 2155-14 and 2155-18 triggers aberrant double-stranded RNA accumulation, upregulates interferon signaling, and increases the number of intratumoral immune cells. We hypothesize that these immune effects are mediated by changes in the properties of melanoma-derived exosomes due to H1/H2 inhibition. Exosomes were isolated from human melanoma cells exposed or not to H1/H2 inhibitors using sequential centrifugation and fast protein liquid chromatography.

Purified exosomes were incubated with peripheral blood mononuclear cells (PBMCs). Flow cytometry assessed immune cell activation markers, proliferation, apoptosis, and Th1/Th2 cytokine profiles. Our goal is to determine whether melanoma-derived exosomes following H1/H2 inhibition exhibit immunostimulatory or immunosuppressive effects on selected immune cells. Melanoma exosomes incubated with ex vivo stimulated PBMCs reduced natural killer (NK) cell activation 1.42-fold and B cell activation 1.41-1.84-fold (based on expression of two activation markers) compared with stimulated PBMCs alone. However, exosomes isolated from H1/H2-treated melanoma cells did not suppress expression of activation markers in B and NK cells. These changes suggest that while melanoma exosomes suppress the anti-tumor immune response, H1/H2 inhibition reverses the immunosuppressive properties of melanoma cells.

DISCUSSION: Our work using PBMCs to determine immunomodulatory properties of exosomes will define their roles in observed stimulation of anti-melanoma immune responses due to H1/H2 inhibition.