Compromised epigenetic robustness in cancer: fueling evolution, exposing weakness.

The complex network of proteins that regulate chromatin and DNA methylation landscapes is often disrupted in cancer. Clonal and subclonal mutations targeting a wide range of molecular functions are frequently observed across cancer types, and emerging evidence suggests that loss of robust epigenetic control promotes both cancer initiation and evolution, independently of context-specific effects. Here, we review how diverse genetic alterations that destabilize the epigenetic regulatory network (ERN) may converge into common phenotypes.

Cancer Evolution: A Multifaceted Affair.

Unlabelled: Cancer cells adapt and survive through the acquisition and selection of molecular modifications. This process defines cancer evolution. Building on a theoretical framework based on heritable genetic changes has provided insights into the mechanisms supporting cancer evolution.

H4K16ac activates the transcription of transposable elements and contributes to their cis-regulatory function.

Mammalian genomes harbor abundant transposable elements (TEs) and their remnants, with numerous epigenetic repression mechanisms enacted to silence TE transcription. However, TEs are upregulated during early development, neuronal lineage, and cancers, although the epigenetic factors contributing to the transcription of TEs have yet to be fully elucidated. Here, we demonstrate that the male-specific lethal (MSL)-complex-mediated histone H4 acetylation at lysine 16 (H4K16ac) is enriched at TEs in human embryonic stem cells (hESCs) and cancer cells.

CRISPR-based large-scale modeling of loss-of-function mutations to investigate mechanisms of stress resistance in cancer.

Dissecting mechanisms driving subclone expansion in primary cancers has been challenging. Here, we present a protocol to systematically disrupt entire gene networks and assess the functional impact of this perturbation on cancer cell fitness. By combining arrayed CRISPR libraries and high-content microscopy, we describe steps to identify classes of genes whose inactivation promotes resistance to environmental challenges faced by cancer cells during tumor growth or upon therapy.

Selective advantage of epigenetically disrupted cancer cells via phenotypic inertia.

The evolution of established cancers is driven by selection of cells with enhanced fitness. Subclonal mutations in numerous epigenetic regulator genes are common across cancer types, yet their functional impact has been unclear. Here, we show that disruption of the epigenetic regulatory network increases the tolerance of cancer cells to unfavorable environments experienced within growing tumors by promoting the emergence of stress-resistant subpopulations.