Geometric regulation of histone state directs melanoma reprogramming

Junmin Lee,Christopher H Seward,Hetvi Gandhi,Thomas G Molley,Jia-Lin Yang,Amr A Abdeen,Xiaochun Wang,Huimin Zhang,Kristopher A Kilian,Katharina Gaus

doi:10.1038/s42003-020-1067-1

Abstract

Malignant melanoma displays a high degree of cellular plasticity during disease progression. Signals in the tumor microenvironment are believed to influence melanoma plasticity through changes in the epigenetic state to guide dynamic differentiation and de-differentiation. Here we uncover a relationship between geometric features at perimeter regions of melanoma aggregates, and reprogramming to a stem cell-like state through histone marks H3K4Me2 and H3K9Ac. Using an in vitro tumor microengineering approach, we find spatial enrichment of these histone modifications with concurrent expression of stemness markers. The epigenetic modifier PRDM14 overlaps with H3K9Ac and shows elevated expression in cells along regions of perimeter curvature. siRNA knockdown of PRDM14 abolishes the MIC phenotype suggesting a role in regulating melanoma heterogeneity. Our results suggest mechanotransduction at the periphery of melanoma aggregates may orchestrate the activity of epigenetic modifiers to regulate histone state, cellular plasticity, and tumorigenicity.

Highlights

Malignant melanoma displays a high degree of cellular plasticity during disease progression
To classify histones linked to epigenetic reprogramming from melanoma to the melanoma-initiating cells (MICs) state, we employed microengineered hydrogels that we previously demonstrated will coordinate enhancement of the MIC phenotype with spatial control (Supplementary Fig. 1)
To understand how geometric cues at the perimeter of microaggregates of melanoma cells will influence histone state, we characterized a panel of histone marks that are implicated in controlling oncogenic gene activation

Summary

Introduction

Malignant melanoma displays a high degree of cellular plasticity during disease progression. Microenvironment-mediated epigenetic regulation of cancer-related gene expression through DNA methylation, histone modification, and chromatin compartments is believed to take part in a broad spectrum of cancer behaviors ranging from initiation to phenotypic alteration[4]. Conversion to a stem cell-like state has been guided by microenvironment-mediated epigenetic regulation of gene expression including factors such as pH10, radiation[11], stiffness[12], hypoxia[13], and interfacial stress[14]. These microenvironment parameters are not mutually exclusive and likely integrate in a context-dependent fashion during progression to guide tumor heterogeneity underlying progression. Our use of microengineering based on soft lithography allows us to mimic aspects of the tumor microenvironment, effectively deconstructing the biophysical cues of stiffness and geometry to probe how these parameters provide a context to facilitate epigenetic reprogramming to a stem cell-like tumorigenic state

Methods

Results

Conclusion