Tumors Exploit Interclonal Hedgehog-Wnt Crosstalk to Drive Tumor-Promoting Cell Competition

Intratumoral heterogeneity (ITH) fuels cancer progression, therapy resistance, and relapse. Although single-cell omics offer unprecedented resolution for studying ITH and the dynamic interactions between tumor cells and the microenvironment, the genetic mechanisms underlying interclonal communication between genetically distinct tumor subclones remain poorly understood. Here, we establish in vivo ITH genetic screening models in Drosophila eye epithelium and uncover a novel cell competition mechanism driven by interclonal Hedgehog (Hh)-Wnt crosstalk that amplifies ITH and tumor aggression. We show that Pp1-87B phosphatase depletion in Ras-mutant clones triggers competitive interactions: Pp1-87B-deficient "loser" clones activate Hh signaling, driving their own elimination via JNK-induced apoptosis and Hippo pathway suppression. Simultaneously, these "losers" secrete Wingless (Wg), the Wnt ligand, which activates beta-catenin signaling in neighboring RasV12 "winner" clones. This bidirectional Hh-Wnt signaling rewires "winner" fitness, endowing them with a hyperproliferative, invasion-prone "super-competitor" phenotype that drives tumor progression. Crucially, this crosstalk is conserved in mammals. Depletion of PPP1CA, the human ortholog of Pp1-87B, in KRAS-mutant pancreatic cancer cells recapitulates Hh-Wnt synergy, accelerating neighboring tumor growth in mouse xenograft models. These findings were facilitated by perfoming multi-omics data analysis (bulk RNA-seq and ATAC-seq) of subclones with different genetic backgrounds from Drosophila to mammals.