Tim-3 and TIGIT mark Natural Killer cells susceptible to effector dysfunction in human bladder cancer

Abstract

Abstract Natural Killer cell (NK) effector functions are diminished during cancer but the phenotype and mediators of this process are unclear. In contrast, dysfunctional T cells express markers of “exhaustion” (e.g. CTLA-4 and PD-1), and inhibition of signaling through these molecules has improved clinical outcome in multiple tumors. Our data from 100+ patients with bladder cancer (BC) suggests that NK undergo an analogous process of exhaustion marked by up-regulation of Tim-3 and TIGIT in both the periphery and tumor. Tim-3 and TIGIT are induced on both immature and mature NK subsets suggesting implications for normal NK maturation. The magnitude of Tim-3 expression in both tissues is tuned to the invasiveness of the primary tumor, while TIGIT is not, making Tim-3 function as a rheostat for primary tumor invasiveness. Both molecules are expressed at equivalent frequencies in both tissues independent of the magnitude of overall expression but define NK with different effector functions. Peripheral NK from BC patients are functionally comparable to NK from healthy donors in their ability to produce IFNγ and degranulate in response to target cells, while tumor NK are refractory to both stimuli. NK from tumors are not terminally exhausted as they make IFNγ, TNFa, and degranulate after “resting” ex vivo prior to stimulation. Blockade of Tim-3, but not TIGIT, enhances effector function in peripheral NK from BC patients, but is ineffective for NK in tumor tissue implicating tumor-specific factors in mediating NK dysfunction. Tim-3 blockade was most efficient in NK from BC patients after activation with IL-15 suggesting specific inflammatory cues affect responsiveness to checkpoint blockade. Ongoing work will develop strategies to reverse NK exhaustion.