Adipocyte-derived β-hydroxybutyrate confers metabolic resilience in multiple myeloma

Multiple myeloma (MM) remains an incurable blood cancer. Obesity is a known risk factor, but how adipocytes promote MM progression is not fully understood. Here, we uncover a metabolic crosstalk between adipocytes and MM cells that promotes MM cell survival under glucose deprivation. We show that glucose restriction activates AMPK, disrupting HSP90-IRF4 binding and rendering IRF4 susceptible to TRIM21-mediated proteasomal degradation. Paradoxically, the same stress stimulates adipocytes to produce β-hydroxybutyrate (β-OHB). MM cells utilize β-OHB through OXCT1-mediated ketolysis, fueling NAT10-dependent acetylation of IRF4 at K87, which restores IRF4-HSP90 binding and sustains tumor cell survival. Genetic ablation of the rate-limiting ketogenic enzyme Hmgcs2 in adipocytes abrogates this protective effect. Importantly, combining an AMPK activator (metformin) with an OXCT1 inhibitor (pimozide) or a NAT10 inhibitor (remodelin) shows synergistic anti-tumor activity in vivo. Our findings position adipocyte-derived β-OHB as a critical metabolic adaptor and highlight a potential combination therapy for MM. Multiple cell populations within the bone tumour microenvironment have been shown to support multiple myeloma (MM). Here, the authors show that under glucose deprived conditions, adipocytes produce β-hydroxybutyrate, which promotes MM cell survival.