Cell polarity opposes Jak-STAT mediated Escargot activation that drives intratumor heterogeneity in a Drosophila tumor model

In proliferating neoplasms, microenvironment-derived selective pressures promote tumor heterogeneity by imparting diverse capacities for growth, differentiation and invasion. However, what makes a tumor cell respond to signaling cues differently from a normal cell is not well understood. In the Drosophila ovarian follicle cells, apicobasal-polarity loss induces heterogenous epithelial multilayering. When exacerbated by oncogenic-Notch expression, this multilayer displays an increased consistency in the occurrence of morphologically distinguishable cells adjacent to the polar follicle cells. Polar cells release the Jak-STAT ligand Unpaired (Upd), in response to which, neighboring polarity-deficient cells exhibit a precursor-like transcriptomic state. These cells activate the Snail-family transcription factor Escargot (Esg), among several regulons that we identify using single-cell transcriptomics. We also ascertain a similar relationship between Upd and Esg in normally-developing ovaries, where establishment of polarity determines early follicular differentiation. Overall, our results indicate that epithelial-cell polarity acts as a gatekeeper against microenvironmental selective pressures that drive heterogeneity. Overall design: Whole-tissue RNA-Seq (2 replicates per genotype; 2 time-points - 24h and 96h) of tjTS>GFP (Control) and tjTS>lglRNAi, tjTS>NICD, tjTS>Upd, tjTS>Upd+lglRNAi and tjTS>NICD+lglRNAi (Samples) and single-cell RNA-Seq (1 replicate; 1 time-point - 72h) of w1118 cells (Control) of the Drosophila ovary and tjTS>lglRNAi, tjTS>Upd+lglRNAi and tjTS>NICD+lglRNAi cells (Samples) of the Drosophila ovary. Single-cell RNA-Seq: 10x Genomics CHROMIUM Single Cell 3' Solution V2 Chemistry and Sequencing platform: Illumina NovaSeq 6000.