MYC/MIZ1 suppression of lysosomal protein degradation drives immune evasion in pancreatic ductal adenocarcinoma
The MYC oncoprotein promotes immune evasion of pancreatic ductal adenocarcinoma (PDAC), but the underlying molecular mechanisms are not fully understood. Here we show that MYC protects PDAC tumors from CD4+ T cell-dependent elimination. Single cell sequencing shows that MYC suppression in tumor cells increases amino acid availability and broadly activates amino acid-responsive gene expression programs in immune cell populations. This occurs because MYC-driven uptake depletes free amino acids from tumor interstitial fluid and plasma, while MYC compromises macropinocytosis and autophagy, both of which depend on lysosomal protein degradation. MYC engages the POZ/BTB transcription factor MIZ1 to suppress lysosomal genes regulated by the TFE3/TFEB/MITF network or by free MIZ1, thereby inhibiting lysosomal protein degradation. An orthogonal genetic model enabling transient, selective inhibition of amino acid uptake in tumor cells recapitulates the effects of MYC depletion on amino acid levels in the tumor microenvironment and induces complete, CD4+ T cell-dependent tumor eradication with long-term survival. We propose that MYC-mediated, cell-autonomous disruption of lysosome function coupled to non-cell-autonomous protection from immune clearance allows MYC-low cells to benefit from MYC-high neighbors, such that intratumoral heterogeneity in MYC expression confers a selective advantage to the entire tumor. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/740267v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@140d2ccorg.highwire.dtl.DTLVardef@cf5f1borg.highwire.dtl.DTLVardef@6d132aorg.highwire.dtl.DTLVardef@10535e6_HPS_FORMAT_FIGEXP M_FIG C_FIG