Oncogenic RAS Signaling Promotes Tumor Immunoresistance by Stabilizing PD-L1 mRNA.
de Carné Trécesson, S
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The immunosuppressive protein PD-L1 is upregulated in many cancers and contributes to evasion of the host immune system. The relative importance of the tumor microenvironment and cancer cell-intrinsic signaling in the regulation of PD-L1 expression remains unclear. We report that oncogenic RAS signaling can upregulate tumor cell PD-L1 expression through a mechanism involving increases in PD-L1 mRNA stability via modulation of the AU-rich element-binding protein tristetraprolin (TTP). TTP negatively regulates PD-L1 expression through AU-rich elements in the 3' UTR of PD-L1 mRNA. MEK signaling downstream of RAS leads to phosphorylation and inhibition of TTP by the kinase MK2. In human lung and colorectal tumors, RAS pathway activation is associated with elevated PD-L1 expression. In vivo, restoration of TTP expression enhances anti-tumor immunity dependent on degradation of PD-L1 mRNA. We demonstrate that RAS can drive cell-intrinsic PD-L1 expression, thus presenting therapeutic opportunities to reverse the innately immunoresistant phenotype of RAS mutant cancers.
The Institute of Cancer Research (Grant ID: Unspecified)
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Cell Line, Tumor
Gene Expression Regulation, Neoplastic
Intracellular Signaling Peptides and Proteins
MAP Kinase Kinase Kinases
Mice, Inbred BALB C
Mice, Inbred C57BL
Proto-Oncogene Proteins p21(ras)
Lung Cancer Group
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Immunity, 2017, 47 (6), pp. 1083 - 1099.e6