Harnessing Myeloid Olfactory Receptors to Reprogram Tumor Immunity

PROJECT SUMMARY Melanoma, an aggressive skin cancer whose incidence continues to rise, with only 30-50% of patients experiencing durable responses to current immune-checkpoint inhibitors. Central to melanoma progression and immune evasion are monocytes and tumor-associated macrophages (TAMs), innate immune cells capable of shifting between anti- and pro-tumorigenic states based on environmental signals. However, the molecular mechanisms governing how these immune cells sense and respond to tumor-derived metabolic cues remain incompletely understood. Recently, we discovered an unexpected sensory mechanism in these myeloid cells involving olfactory receptors (ORs), a family traditionally recognized for their role in smell perception. Our data show that the Olfr2 (human ortholog OR6A2) is functionally expressed in TAMs and circulating monocytes. Activation of Olfr2 by its aldehyde ligand, octanal, an eight-carbon metabolite produced through lipid peroxidation, initiates a signaling cascade ultimately enhancing pro-inflammatory cytokine secretion. Preliminary studies in the B16-F10 melanoma model indicate that loss of Olfr2 exacerbates tumor growth, reduces the recruitment and activation of pro-inflammatory CD64hi macrophages, diminishes intratumoral CD8+ T-cell infiltration, and decreases critical cytokines (IL-1β, CCL2, CXCL9) involved in anti-tumor immunity. Elevated OR6A2 expression in human melanoma correlates positively with progression-free survival following Immune checkpoint blockade. However, not all ORs are protective; some, like Olfr78 and its human ortholog OR51E2 expressed in TAMs, may promote tumor progression. We hypothesize that ORs function broadly as metabolitesensing molecular switches in myeloid cells, decoding tumor-derived metabolites that orchestrate TAM polarization, influence T-cell function, and ultimately determine tumor progression and therapeutic responsiveness. To test this hypothesis, our proposal will employ an integrative strategy: (1) generate the first comprehensive single-cell and spatially resolved “immune-OR signature” of melanoma TAMs and matched peripheral blood monocytes from patients at different disease stages and ICI treatment responses and address their predictive value; (2) Confirm mouse and human preclinical potential and mechanistically dissect how tumorderived metabolites engage discovered ORs to modulate TAMs activation, and adaptive anti-tumor response’s; and (3) validate pharmacologically whether activating protective OR signaling and/or inhibiting suppressive OR pathways synergizes effectively with anti-PD-1 checkpoint therapy to convert immunologically cold tumors into immune-responsive states. Animal models are necessary to study melanoma progression and immunotherapy response within the complex tumor-immune microenvironment. Genetically defined and syngeneic mouse models will enable evaluation of ORs function, antitumor immunity, tumor growth, and response to anti-PD-1 therapy. This work will establish ORs as novel immune-metabolic sensors and potential biomarkers and therapeutic targets for improving immunotherapy in melanoma, aligning with the New Innovator Award’s vision.