Rathmell, Jeffrey C.

Abstract Tissue-resident memory CD8+ T cells (TRM) share characteristics and core residency gene programs with tumor-infiltrating lymphocytes (TILs). However, the transcriptional, metabolic and epigenetic regulation of TRM and TIL differentiation, maintenance and function are largely undefined. Furthermore, it is unknown whether metabolic and epigenetic manipulations can be employed to promote TRM/TIL functional programs for cancer immunotherapy. Here we report a critical mechanism programming the mitochondrial and epigenetic regulation of TRM/TIL functionality in situ. We find that mouse and human TRM/TIL express the transcription factor BHLHE40 and the BHLHE40-associated gene signature. Bhlhe40 is specifically required for TRM and TIL development and poly-functionality. Local PD-1 signaling inhibits TIL Bhlhe40 expression, and Bhlhe40 is critical for TIL reinvigoration following anti-PD therapy. Mechanistically, Bhlhe40 sustains TRM/TIL mitochondrial fitness for the promotion of a functional epigenetic state. Building on these findings, we also identify an epigenetic and metabolic regimen that promotes TRM/TIL gene signatures associated with tissue residency and poly-functionality through in vitro T cell screening. Strikingly, this regimen empowers the anti-tumor activity of CD8+ T cells and possesses therapeutic potential even at an advanced tumor stage in mouse models. Our results provide mechanistic insights on the local regulation of TRM and TIL function, and offer a viable strategy for developing novel immunotherapeutic means for cancer.

Osteoporosis and age-related bone loss are important public health concerns. Therefore, there is a high level of interest in the development of medical interventions and lifestyle changes that reduce the incidence of osteoporosis and age-related bone loss. Decreased bone mineral density is associated with high cholesterol, and patients on statins have increased bone mineral densities, strongly implicating cholesterol as a negative regulator of bone homeostasis. In this study, using both molecular and pharmacological approaches, we have been able to demonstrate that the primary cholesterol metabolite, 27-hydroxycholesterol, through its actions on both estrogen receptors and liver X receptors, decreases osteoblast differentiation and enhances osteoclastogenesis, resulting in increased bone resorbtion in mice. Induction of the short heterodimer partner protein by estrogens in osteoblasts can attenuate the liver X receptor-mediated actions of 27-hydroxycholesterol in bone. These data establish a mechanistic link between cholesterol and bone quality, highlight an unexpected target of estrogens in osteoblasts, and define a signaling axis, the therapeutic exploitation of which is likely to yield novel antiosteoporotic drugs.