Molecular Medicine Israel

Activator protein 1 induces programmed death 1 expression in response to tumor progression

PNAS September 4, 2012

Gang Xiao et al.

“Activator protein 1 suppresses antitumor T-cell function via the induction of programmed death 1”

T cells play a critical role in tumor immunosurveillance by eliminating newly transformed somatic cells. However, tumor cell variants can escape from immunological control after immunoediting, leading to tumor progression. Whether and how T cells respond to tumor growth remain unclear. Here, we found that tumor-infiltrating T cells exhibited persistently up-regulated expression of the activator protein 1 (AP-1) subunit c-Fos during tumor progression. The ectopic expression of c-Fos in T cells exacerbated tumor growth, whereas the T-cell–specific deletion of c-Fos reduced tumor malignancy. This unexpected immunosuppressive effect of c-Fos was mediated through the induced expression of immune inhibitory receptor programmed death 1 (PD-1) via the direct binding of c-Fos to the AP-1–binding site in the Pdcd1(gene encoding PD-1) promoter. A knock-in mutation of this binding site abrogated PD-1 induction, augmented antitumor T-cell function and repressed tumor growth. Taken together, these findings indicate that T-cell c-Fos subsequently induces PD-1 expression in response to tumor progression and that disrupting such induction is essential for repression of tumor growth.

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