PT  - JOURNAL ARTICLE
AU  - Maalavika Pillai
AU  - Gouri Rajaram
AU  - Pradipti Thakur
AU  - Nilay Agarwal
AU  - Srinath Muralidharan
AU  - Ankita Ray
AU  - Jason A Somarelli
AU  - Mohit Kumar Jolly
TI  - Mapping phenotypic heterogeneity in melanoma onto the epithelial-hybrid-mesenchymal axis
AID  - 10.1101/2022.04.05.485702
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.04.05.485702
4099  - http://biorxiv.org/content/early/2022/04/08/2022.04.05.485702.short
4100  - http://biorxiv.org/content/early/2022/04/08/2022.04.05.485702.full
AB  - Epithelial to mesenchymal transition (EMT) is a well-studied hallmark of epithelial-like cancers that is characterized by loss of epithelial markers and gain of mesenchymal markers. Interestingly, melanoma, which is derived from melanocytes of the skin, also undergo phenotypic plasticity toward mesenchymal-like phenotypes under the influence of various micro-environmental cues. Our study connects EMT to the phenomenon of de-differentiation (i.e., transition from proliferative to more invasive phenotypes) observed in melanoma cells during drug treatment. By analyzing 78 publicly available transcriptomic melanoma datasets, we found that de-differentiation in melanoma is accompanied by upregulation of mesenchymal genes, but not necessarily a concomitant loss of an epithelial program, suggesting a more “one-dimensional” EMT that leads to a hybrid epithelial/ mesenchymal phenotype. Samples lying in the hybrid epithelial/mesenchymal phenotype also correspond to the intermediate phenotypes in melanoma along the proliferative-invasive axis - neural crest and transitory ones. Interestingly, as melanoma cells progress along the invasive axis, the mesenchymal signature does not increase monotonically. Instead, we observe a peak in mesenchymal scores followed by a decline, as cells further de-differentiate. This biphasic response recapitulates the dynamics of melanocyte development, suggesting close interactions among genes controlling differentiation and mesenchymal programs in melanocytes. Similar trends were noted for metabolic changes often associated with EMT in carcinomas in which progression along mesenchymal axis correlates with the downregulation of oxidative phosphorylation, while largely maintaining glycolytic capacity. Overall, these results provide an explanation for how EMT and dedifferentiation axes overlap with respect to their transcriptional and metabolic programs in melanoma.Competing Interest StatementThe authors have declared no competing interest.