In recent years, the intricate landscape of cancer biology has increasingly highlighted the pivotal role of epigenetic regulators in tumor development and progression. Among the vast array of epigenetic complexes, the Complex of Proteins Associated with Set1, commonly known as COMPASS, has emerged as a central player influencing cellular differentiation and the specification of cell fate. Notably, within this family, the enhancer-regulating subcomplexes KMT2C–COMPASS and KMT2D–COMPASS have garnered significant attention due to their frequent mutation across a broad spectrum of human cancers, especially those originating from epithelial tissues.
The catalytic subunits of these complexes, histone H3 lysine 4 (H3K4) monomethyltransferases KMT2C (also referred to as MLL3) and KMT2D (also known as MLL4), alongside the H3K27-specific demethylase lysine-specific demethylase 6A (KDM6A or UTX), orchestrate critical epigenetic modifications that regulate enhancer landscapes. These modifications profoundly impact gene expression programs, ultimately directing cell identity and developmental trajectories. Mutations affecting these subunits are among the most recurrent somatic alterations found in tumor genomes, underscoring their fundamental role in maintaining epigenetic homeostasis and preventing malignant transformation.
One of the defining characteristics of KMT2C and KMT2D mutations in cancer is their tissue-specific impact on enhancer function. In normal physiology, these enzymes facilitate the monomethylation of H3K4 at enhancer elements, marking these regions for transcriptional activation. The resultant gene regulatory networks govern key differentiation pathways. When mutations or loss-of-function events occur in KMT2C and KMT2D, the landscape of enhancer activity becomes rewired, which can lead to aberrant transcription programs favoring oncogenesis. Intriguingly, this enhancer dysregulation does not manifest uniformly across different cancer types, highlighting the complexity of their roles in various tissue contexts.
Adding to the complexity is the multifaceted role of KDM6A, which cooperates with KMT2C and KMT2D within the COMPASS complex to remove repressive H3K27 methylation marks. The interplay between adding activating marks and removing repressive ones underlines a finely tuned regulatory system. Loss of KDM6A’s demethylase activity further exacerbates epigenetic derangements in cancer cells, creating a milieu conducive to uncontrolled growth and resistance to normal differentiation cues.
Despite being a focal point of cancer-associated mutations, the direct therapeutic targeting of KMT2C and KMT2D has remained formidable. Their broad roles in essential cellular processes and the heterogeneity of mutations complicate the development of universal inhibitors. Moreover, the context-dependent functions of COMPASS complexes challenge the identification of a one-size-fits-all therapeutic strategy, emphasizing the need for nuanced approaches tailored to specific mutation profiles and tissue types.
Recent advances have unveiled that the mutations in KMT2C– and KMT2D–COMPASS complexes induce vulnerabilities within cancer cells that may be exploited pharmacologically. These vulnerabilities span several cellular processes, ranging from epigenetic deregulation to alterations in metabolic pathways and cell-cycle control mechanisms. Emerging data suggest that metabolic rewiring, driven by enhancer malfunction, renders these cancer cells dependent on specific metabolic substrates or pathways, presenting a window for targeted therapy.
Furthermore, perturbations in cell-cycle regulation and DNA repair mechanisms upon loss or mutation of KMT2C and KMT2D offer additional exploitable targets. Cells bearing COMPASS mutations often exhibit defects in DNA damage response pathways, increasing their susceptibility to genotoxic agents or synthetic lethality approaches. This interplay between epigenetic dysregulation and genome maintenance underscores a complex vulnerability landscape ripe for therapeutic intervention.
Another promising avenue lies in the enhanced immunogenicity observed in tumors harboring COMPASS mutations. Altered enhancer landscapes can lead to aberrant expression of immune modulatory molecules and neoantigens, potentially sensitizing these cancers to immunotherapy. This reprogramming offers a compelling rationale to combine epigenetic and immune-targeted therapies to achieve synergistic anticancer effects.
The quest to harness these vulnerabilities demands comprehensive research into the specific mutation spectrum of KMT2C, KMT2D, and KDM6A across cancer types. Characterizing how different mutation classes—whether missense, truncating, or deletions—affect COMPASS function will be paramount in tailoring therapeutic strategies. Moreover, delineating tissue-specific enhancer dependencies will aid in devising treatment paradigms with precision and minimized off-target consequences.
Study models, both in vitro and in vivo, have begun to shed light on the functional consequences of COMPASS complex disruption. Conditional knockout experiments and CRISPR-mediated gene editing approaches have elucidated key pathways perturbed by KMT2C and KMT2D loss, informing drug discovery pipelines. The integration of epigenomic, transcriptomic, and metabolomic profiling continues to unravel the multidimensional impact of COMPASS dysfunction on cancer biology.
Looking forward, the development of small molecules or biologics that restore enhancer function or compensate for COMPASS deficits holds great promise. Alternatively, synthetic lethality approaches aiming to target pathways unmasked by COMPASS mutations could revolutionize treatment for patients whose tumors harbor these alterations. Seamlessly integrating these approaches with existing chemotherapy, targeted agents, or immunotherapies could redefine the clinical management of multiple cancer types.
In conclusion, the vulnerabilities created by mutation and loss of KMT2C– and KMT2D–COMPASS families represent a paradigm shift in understanding the epigenetic underpinnings of cancer. These complexes sit at the crossroads of chromatin regulation, metabolic adaptation, and immune landscape modulation, offering multiple nodes for therapeutic exploitation. As research unfolds, the intricate enhancer and metabolic rewiring orchestrated by COMPASS dysfunction will likely transform into actionable targets, heralding new eras of personalized oncology therapy.
Subject of Research:
Epigenetic regulatory complexes KMT2C–COMPASS and KMT2D–COMPASS function and their mutation-driven vulnerabilities in cancer.
Article Title:
Enhancer and metabolic rewiring by KMT2C–COMPASS or KMT2D–COMPASS family loss in cancer creates druggable vulnerabilities.
Article References:
Zhao, Z., Shilatifard, A. Enhancer and metabolic rewiring by KMT2C–COMPASS or KMT2D–COMPASS family loss in cancer creates druggable vulnerabilities. Nat Rev Cancer (2026). https://doi.org/10.1038/s41568-026-00919-x
Image Credits: AI Generated
DOI: 10.1038/s41568-026-00919-x
Keywords:
KMT2C, KMT2D, COMPASS complex, epigenetics, enhancer regulation, cancer mutations, metabolic rewiring, DNA repair, immunogenicity, therapeutic vulnerabilities
