The aged tumor microenvironment limits T cell control of cancer.

The etiology and effect of age-related immune dysfunction in cancer is not completely understood. Here we show that limited priming of CD8(+) T cells in the aged tumor microenvironment (TME) outweighs cell-intrinsic defects in limiting tumor control. Increased tumor growth in aging is associated with reduced CD8(+) T cell infiltration and function. Transfer of T cells from young mice does not restore tumor control in aged mice owing to rapid induction of T cell dysfunction. Cell-extrinsic signals in the aged TME drive a tumor-infiltrating age-associated dysfunctional (T(TAD)) cell state that is functionally, transcriptionally and epigenetically distinct from canonical T cell exhaustion. Altered natural killer cell-dendritic cell-CD8(+) T cell cross-talk in aged tumors impairs T cell priming by conventional type 1 dendritic cells and promotes T(TAD) cell formation. Aged mice are thereby unable to benefit from therapeutic tumor vaccination. Critically, myeloid-targeted therapy to reinvigorate conventional type 1 dendritic cells can improve tumor control and restore CD8(+) T cell immunity in aging.