Integrated omics-analysis reveals Wnt-mediated NAD⁺ metabolic reprogramming in cancer stem-like cells

Abnormal tumor cell metabolism is a consequence of alterations in signaling pathways that provide critical selective advantage to cancer cells. However, a systematic characterization of the metabolic and signaling pathways altered in cancer stem-like cells (CSCs) is currently lacking. Using nuclear magnetic resonance and mass spectrometry, we profiled the whole-cell metabolites of a pair of parental (P- 231) and stem-like cancer cells (S-231), and then integrated with whole transcriptome profiles. We identified elevated NAAD⁺ in S-231 along with a coordinated increased expression of genes in Wnt/calcium signaling pathway, reflecting the correlation between metabolic reprogramming and altered signaling pathways. The expression of CD38 and ALP, upstream NAAD⁺ regulatory enzymes, was oppositely regulated between P- and S-231; high CD38 strongly correlated with NAADP in P-231 while high ALP with NAAD⁺ levels in S-231. Antagonizing Wnt activity by dnTCF4 transfection reversed the levels of NAAD⁺ and ALP expression in S-231. Of note, elevated NAAD⁺ caused a decrease of cytosolic Ca²⁺ levels preventing calcium-induced apoptosis in nutrient-deprived conditions. Reprograming of NAD⁺ metabolic pathway instigated by Wnt signaling prevented cytosolic Ca²⁺ overload thereby inhibiting calcium-induced apoptosis in S-231. These results suggest that "oncometabolites" resulting from cross talk between the deranged core cancer signaling pathway and metabolic network provide a selective advantage to CSCs.