Multiomics integration unveils a shifted balance in the sphingosine-1 phosphate/ceramide rheostat fueled by macrophage immunosuppression in metastatic colorectal cancer

Background Thirty years ago, a S1P/ceramide “sphingosine rheostat” model was proposed based on ceramide's pro-apoptotic vs . sphingosine-1 phosphate (S1P) pro-survival role, where in cancer, the rheostat tilts towards enhanced synthesis of S1P from ceramides, increasing the ratio. Human tumor data supporting the hypothesis, however, are very limited. Objective To leverage quantitative multi-omics to explore the balance in the synthesis of lipids within the S1P/Ceramide metabolic pathway in a large set (n = 629) of human colorectal cancers (CRC). Design Quantitative LC-MS/MS analysis was performed on 525 primary and 104 metastatic CRC (mCRC). An integrative multi-omics analysis combining quantitative lipidomics with whole transcriptomics, quantitative RT-PCR of selected genes and clinical data was completed. Results We demonstrated that mCRC versus primary specimens are relatively enriched in S1P and sphinganine-1-P (Sa1P), whereas the long chain ceramides (24:1) are relatively decreased. Gene-expression analysis of a large (n = 2200) CRC patient dataset and qRT-PCR of CRC revealed that S1P/Sa1P-synthesizing enzymes and their receptors are enriched in mCRC and are linked to poor prognosis. scRNA-seq analysis showed that their expression prevailed in myeloid cells. Finally, a three-gene S1P macrophage-associated signature correlated with stage and patient survival. Conclusion Our findings define an imbalance in the synthesis of S1P/Ceramide linked to poor prognosis and cancer progression, and attributable to proinflammatory macrophages in the tumor microenvironment, validating the sphingosine rheostat hypothesis in mCRC.