Kras activity-linked glycolysis and immunosuppression in metastatic pancreatic cancer

Background: KRAS mutations act as a driver of pancreatic ductal adenocarcinoma (PDAC), involving ERK-dependent gene transcription. Inhibition of mutated KRAS activity suppresses glycolysis and reshapes the poor immune profile in murine PDAC. Identification of these relationships in human PDAC is useful for realizing pivotal drivers of metabolic and immune dependency. Recently identified PDAC siKRAS KRASi iKras gene sets enable the creation of a precise KRAS signature score for KRAS activity. Using liver metastasis (LM)-derived transcriptome data, we evaluated the effect of KRAS signature score on clinical outcomes and the molecular features of metastatic PDAC. Methods: Comprehensive mRNA expression on cDNA microarray and 435 protein expressions on reverse-phased protein array (RPPA) were measured using needle-biopsied samples from treatment-naïve LM of PDAC. KRAS signature score was calculated in each sample. A KRAS-related gene module was determined based on the relationship between KRAS signature score and module eigengene from weighted co-expression network analysis. Hierarchical clustering of RPPA data generated KRAS-related subtypes, in which a KRAS-related protein was selected from the molecule encoded by the genes of KRAS-related gene modules. Results: KRAS signature score in LMs was calculated in 77 patients (Male: 65%; median age: 66 years). Patients with high KRAS signature score tumors (n=38) showed poor overall survival as compared to those with low KRAS signature score tumors (n=39; hazard ratio: 1.895 [95% confidential interval: 1.123 to 3.198]). KRAS mutated LMs (90.9%) were related to high KRAS signature scores (P=0.004). DUSP4 mRNA expression, an ERK-dependent negative feedback gene for ERK dephosphorylation, increased in tumors with high KRAS signature scores (P=0.017) and with KRAS mutation (P<0.001). Thirty-seven proteins were identified as KRAS-related UP proteins, including those involved in the glycolysis pathway and a lactate transporter, MCT4. The gene up-regulation of glycolysis and lactate-efflux pathway was found in HK2 (P=0.132), Eno1, 2 (P<0.001, P=0.016), PKM (P<0.001), LDHA (P<0.001), and MCT4 (P<0.001). ZAP-70, a cytosolic tyrosine kinase essential for T cell receptor signaling, was present in nine KRAS-related DOWN proteins. The gene down-regulation of the immune profile was found in CD4 (P<0.001), CD8A (P<0.001), CD8B (P=0.013), and ZAP-70 (P<0.001). Conclusion: KRAS up-regulated tumors showed elevation of glycolytic molecules and immunosuppression in LM of pancreatic cancer. KRAS activity might drive metabolic and immunological aggravation, leading to a poor prognosis.