| dc.description.abstract | In addition to their role in bioenergetic homeostasis, mitochondria are increasingly appreciated as regulators of hematopoietic cell fate and function. Here, we demonstrate the role of ATP citrate lyase (ACLY) on murine hematopoietic stem cell fate and the role of mitochondrial membrane potential on T-cell function and clonal expansion in clear cell renal cell carcinoma (ccRCC) patients treated with α-PD-1/α-CTLA-4 immune checkpoint blockade (ICB).
We demonstrate that ATP citrate lyase (Acly), which metabolizes mitochondrially-derived citrate to generate cytosolic acetyl-CoA and is of clinical interest, can regulate chromatin accessibility to limit myeloid differentiation. Acly was tested for a role in hematopoiesis by small-molecule inhibition or genetic deletion in lineage-depleted, c-Kit-enriched hematopoietic stem and progenitor cells from Mus musculus. Treatments increased the abundance of cell populations that expressed the myeloid integrin CD11b and other markers of myeloid differentiation. Acly-inhibited HSPCs revealed greater macrophage differentiation-related gene expression likely facilitated by greater Cebpe expression and increased chromatin accessibility at myeloid lineage genes such as CD11b, CD11c, and IRF8. This effect of Acly deficiency was accompanied by altered mitochondrial mass, membrane potential, and reactive oxygen species production. The bias to myeloid differentiation was reversed with supplementation of exogenous acetate to support alternate compensatory pathways to produce acetyl-CoA. Acly inhibition thus can promote myelopoiesis through deprivation of acetyl-CoA and altered histone acetylome to regulate C/EBP transcription factor family activity for myeloid differentiation.
We also present evidence that mitochondrial membrane potential (ΔΨm) regulates ccRCC patient T-cell responses to α-PD-1/α-CTLA-4 ICB. Through single-cell RNA-seq and single-cell V(D)J-seq analysis of four patients’ T-cells, we demonstrate that low ΔΨm T-cell responses are more clonal and differentially express genes associated with cytotoxic CD8+ T-cells. Furthermore, greater repertoire similarity between tumor T-cells and ΔΨm low peripheral T-cells appear to correlate with positive response to ICB. Finally, we document a population of peripheral T-cells that share TCR CDR3 sequences with tumor T-cells with lower than average ΔΨm. These preliminary data indicate that low ΔΨm T-cells may confer positive outcomes to ICB in ccRCC patients. Collectively, these projects demonstrate the guiding role of mitochondrial metabolism in regulating hematopoietic cell fate and function. | |
