Cdk5 disruption attenuates tumor PD L1 expression and promotes antitumor immunity
Cyclin suppresses antitumor immunity Despite the dramatic success of cancer immunotherapy, many types of cancer do not respond. Understanding why could help us to find ways to enhance the overall responsiveness of tumors to immunotherapies. Dorand et al. report that cyclin dependent kinase 5 (Cdk5) an enzyme that is highly expressed by neurons in many brain cancers, may dampen the ability of T cells to reject tumors. In a mouse model of medulloblastoma, if tumors were Cdk5 deficient, T cells were able to remove them. This heightened antitumor immunity correlated with reduced expression of the inhibitory molecule programmed cell death ligand 1 (PD L1) a target of current cancer immunotherapies. Science, this issue p. 399 Cyclin dependent kinase 5 expression by tumors inhibits antitumor immunity in human and mouse medulloblastoma. Cancers often evade immune surveillance by adopting peripheral tissue tolerance mechanisms, such as the expression of programmed cell death ligand 1 (PD L1) the inhibition of which results in potent antitumor immunity. Here, we show that cyclin dependent kinase 5 (Cdk5) a serine threonine kinase that is highly active in postmitotic neurons and in many cancers, allows medulloblastoma (MB) to evade immune elimination. Interferon g (IFN g) induced PD L1 up regulation on MB requires Cdk5, and disruption of Cdk5 expression in a mouse model of MB results in potent CD4+ T cell mediated tumor rejection. Loss of Cdk5 results in persistent expression of the PD L1 transcriptional repressors, the interferon regulatory factors IRF2 and IRF2BP2, which likely leads to reduced PD L1 expression on tumors. Our finding highlights a central role for Cdk5 in immune checkpoint regulation by tumor cells.
Science