A unique subset of glycolytic tumor propagating cells drives squamous cell carcinoma

Head and Neck Squamous Cell Carcinoma (HNSCC) remains among the most aggressive human cancers. Tumor progression and aggressiveness in SCC are largely driven by Tumor Propagating Cells (TPCs). Aerobic glycolysis, also known as the Warburg Effect, represents a characteristic of many cancers, yet whether this adaptation is functionally important in SCC, and at which stage, remains poorly understood. Here, we show that the NAD+-dependent histone deacetylase Sirtuin 6 (SIRT6) is a robust tumor suppressor in SCC, acting as a modulator of glycolysis in these tumors. Remarkably, rather than a late adaptation, we find enhanced glycolysis specifically in TPCs. More importantly, using single cell RNA sequencing of TPCs, we identify a subset of TPCs with higher glycolysis and enhanced pentose phosphate pathway and glutathione metabolism, characteristics that are strongly associated with a better antioxidant response. Altogether, our studies uncover enhanced glycolysis as a main driver in SCC, and, more importantly, identify a subset of TPCs as the cell-of-origin for the Warburg effect, defining metabolism as a key feature of intra-tumor heterogeneity. Overall design: We examined 284 tumor propagating cells (TPCs) from two wild type (WT) and two Sirt6-/- mice using the Smart-seq2 protocol for single-cell transcriptomics.