Chronic stress promotes tumor immune evasion via the suppression of MHC-I expression and the upregulation of PD-L1.

Chronic stress induces cancer initiation and progression via regulation of diverse cancer risk factors including immune evasion. Our previous research demonstrated that β-adrenergic blockade with propranolol almost completely reversed the accelerated tumor growth induced by chronic restraint stress, but the underlying mechanism of immune escape remains largely unknown. In the present study, a chronic restraint stress paradigm was applied to the H22 hepatocellular carcinoma (HCC) bearing mice to mimic the psychological stress. We observed that chronic restraint stress significantly promoted HCC growth and tumor escape from T cell surveillance. Chronic restraint stress reduced intratumor MHC-I expression and enhanced PD-L1 expression, whereas propranolol rectified the changes of MHC-I and PD-L1. Under chronic stress, the activated MAPK pathway suppressed MHC-I production by inactivating STAT1/IRF1 signaling pathway, and promoted PD-L1 translation by elevating eIF2α phosphorylation. These findings support the crucial role of β-adrenergic signaling cascade in the tumor escape from T cell surveillance under chronic restraint stress.