Human WDR5 promotes breast cancer growth and metastasis via KMT2-independent translation regulation

KMT2C and KMT2D aberrations in breast cancer

KMT2C and KMT2D are histone lysine methyltransferases responsible for the monomethylation of histone 3 lysine 4 (H3K4) residues at gene enhancer sites. KMT2C/D are the most frequently mutated histone methyltransferases (HMTs) in breast cancer, occurring at frequencies of 10-20% collectively. Frequent damaging and truncating somatic mutations indicate a tumour-suppressive role of KMT2C/D in breast oncogenesis. Recent studies using cell lines and mouse models to replicate KMT2C/D loss show that these genes contribute to oestrogen receptor (ER)-driven transcription in ER+ breast cancers through the priming of gene enhancer regions. This review provides an overview of the functions of KMT2C/D and outlines the recent clinical and experimental evidence of the roles of KMT2C and KMT2D in breast cancer development.

Ribosome subunit attrition and activation of the p53-MDM4 axis dominate the response of MLL-rearranged cancer cells to WDR5 WIN site inhibition

The chromatin-associated protein WD Repeat Domain 5 (WDR5) is a promising target for cancer drug discovery, with most efforts blocking an arginine-binding cavity on the protein called the 'WIN' site that tethers WDR5 to chromatin. WIN site inhibitors (WINi) are active against multiple cancer cell types in vitro, the most notable of which are those derived from MLL-rearranged (MLLr) leukemias. Peptidomimetic WINi were originally proposed to inhibit MLLr cells via dysregulation of genes connected to hematopoietic stem cell expansion. Our discovery and interrogation of small-molecule WINi, however, revealed that they act in MLLr cell lines to suppress ribosome protein gene (RPG) transcription, induce nucleolar stress, and activate p53. Because there is no precedent for an anticancer strategy that specifically targets RPG expression, we took an integrated multi-omics approach to further interrogate the mechanism of action of WINi in human MLLr cancer cells. We show that WINi induce depletion of the stock of ribosomes, accompanied by a broad yet modest translational choke and changes in alternative mRNA splicing that inactivate the p53 antagonist MDM4. We also show that WINi are synergistic with agents including venetoclax and BET-bromodomain inhibitors. Together, these studies reinforce the concept that WINi are a novel type of ribosome-directed anticancer therapy and provide a resource to support their clinical implementation in MLLr leukemias and other malignancies.

Exploring promising natural compounds for breast cancer treatment: in silico molecular docking targeting WDR5-MYC protein interaction

Cancer is an aberrant differentiation of normal cells, characterized by uncontrolled growth and the potential to acquire invasive and aggressive properties that ultimately lead to metastasis. In the realm of scientific exploration, a multitude of pathways has been investigated and targeted by researchers, among which one specific pathway is recognized as WDR5-MYC. Continuous investigations and research show that WDR5-MYC is a therapeutic target protein. Hence, the discovery of naturally occurring compounds with anticancer properties has been suggested as a rapid and efficient alternative for the development of anticancerous therapeutics. A virtual screening approach was used to identify the most potent compounds from the NP-lib database at the MTiOpenScreen webserver against WDR5-MYC. This process yielded a total of 304 identified compounds. Subsequently, after screening, four potent compounds, namely Estrone (ZINC000003869899), Ethyl-1,2-benzanthracene (ZINC000003157052), Strychnine (ZINC000000119434) and 7H-DIBENZO [C, G] CARBAZOLE (ZINC000001562130), along with a cocrystallized 5-[4-(trifluoromethyl) phenyl]-1H-tetrazole inhibitor (QBP) as a reference ligand, were considered for stringent molecular docking. Thus, each compound exhibited significant docking energy between -8.2 and -7.7 kcal/mol and molecular contacts with essential residue Asn225, Lys250, Ser267 and Lys272 in the active pocket of WDR5-MYC against the QBP inhibitor (the native ligand QBP serves as a reference in the comparative analysis of docked complexes). The results support the potent compounds for drug-likeness and strong binding affinity with WDR5-MYC protein. Further, the stability of the selected compounds was predicted by molecular dynamics simulation (100 ns) contributed by intermolecular hydrogen bonds and hydrophobic interactions. This demonstrates the potential of the selected compounds to be used against breast cancer treatment.Communicated by Ramaswamy H. Sarma.

Ribosome subunit attrition and activation of the p53-MDM4 axis dominate the response of MLL-rearranged cancer cells to WDR5 WIN site inhibition

The chromatin-associated protein WD Repeat Domain 5 (WDR5) is a promising target for cancer drug discovery, with most efforts blocking an arginine-binding cavity on the protein called the "WIN" site that tethers WDR5 to chromatin. WIN site inhibitors (WINi) are active against multiple cancer cell types in vitro, the most notable of which are those derived from MLL-rearranged (MLLr) leukemias. Peptidomimetic WINi were originally proposed to inhibit MLLr cells via dysregulation of genes connected to hematopoietic stem cell expansion. Our discovery and interrogation of small molecule WIN site inhibitors, however, revealed that they act in MLLr cell lines to suppress ribosome protein gene (RPG) transcription, induce nucleolar stress, and activate p53. Because there is no precedent for an anti-cancer strategy that specifically targets RPG expression, we took an integrated multi-omics approach to further interrogate the mechanism of action of WINi in MLLr cancer cells. We show that WINi induce depletion of the stock of ribosomes, accompanied by a broad yet modest translational choke and changes in alternative mRNA splicing that inactivate the p53 antagonist MDM4. We also show that WINi are synergistic with agents including venetoclax and BET-bromodomain inhibitors. Together, these studies reinforce the concept that WINi are a novel type of ribosome-directed anti-cancer therapy and provide a resource to support their clinical implementation in MLLr leukemias and other malignancies.

WD Repeat Domain 5 Inhibitors for Cancer Therapy: Not What You Think

WDR5 is a conserved nuclear protein that scaffolds the assembly of epigenetic regulatory complexes and moonlights in functions ranging from recruiting MYC oncoproteins to chromatin to facilitating the integrity of mitosis. It is also a high-value target for anti-cancer therapies, with small molecule WDR5 inhibitors and degraders undergoing extensive preclinical assessment. WDR5 inhibitors were originally conceived as epigenetic modulators, proposed to inhibit cancer cells by reversing oncogenic patterns of histone H3 lysine 4 methylation-a notion that persists to this day. This premise, however, does not withstand contemporary inspection and establishes expectations for the mechanisms and utility of WDR5 inhibitors that can likely never be met. Here, we highlight salient misconceptions regarding WDR5 inhibitors as epigenetic modulators and provide a unified model for their action as a ribosome-directed anti-cancer therapy that helps focus understanding of when and how the tumor-inhibiting properties of these agents can best be understood and exploited.

Discovery of Potent and Selective WDR5 Proteolysis Targeting Chimeras as Potential Therapeutics for Pancreatic Cancer

As a core chromatin-regulatory scaffolding protein, WDR5 mediates numerous protein-protein interactions (PPIs) with other partner oncoproteins. However, small-molecule inhibitors that block these PPIs exert limited cell-killing effects. Here, we report structure-activity relationship studies in pancreatic ductal adenocarcinoma (PDAC) cells that led to the discovery of several WDR5 proteolysis-targeting chimer (PROTAC) degraders, including 11 (MS132), a highly potent and selective von Hippel-Lindau (VHL)-recruiting WDR5 degrader, which displayed positive binding cooperativity between WDR5 and VHL, effectively inhibited proliferation in PDAC cells, and was bioavailable in mice and 25, a cereblon (CRBN)-recruiting WDR5 degrader, which selectively degraded WDR5 over the CRBN neo-substrate IKZF1. Furthermore, by conducting site-directed mutagenesis studies, we determined that WDR5 K296, but not K32, was involved in the PROTAC-induced WDR5 degradation. Collectively, these studies resulted in a highly effective WDR5 degrader, which could be a potential therapeutic for pancreatic cancer and several potentially useful tool compounds.

Epigenetic markers and therapeutic targets for metastasis

The last few years have seen an increasing number of discoveries which collectively demonstrate that histone and DNA modifying enzyme modulate different stages of metastasis. Moreover, epigenomic alterations can now be measured at multiple scales of analysis and are detectable in human tumors or liquid biopsies. Malignant cell clones with a proclivity for relapse in certain organs may arise in the primary tumor as a consequence of epigenomic alterations which cause a loss in lineage integrity. These alterations may occur due to genetic aberrations acquired during tumor progression or concomitant to therapeutic response. Moreover, evolution of the stroma can also alter the epigenome of cancer cells. In this review, we highlight current knowledge with a particular emphasis on leveraging chromatin and DNA modifying mechanisms as biomarkers of disseminated disease and as therapeutic targets to treat metastatic cancers.

Collagen-induced DDR1 upregulates CXCL5 to promote neutrophil extracellular traps formation and Treg infiltration in breast cancer

Neutrophil extracellular traps (NETs) have been implicated in many cancers, but the regulatory mechanisms in the context of breast cancer have not been thoroughly discussed. This study proposed a mechanism based on collagen-activated DDR1/CXCL5 for NET formation in breast cancer. Through TCGA and GEO-based bioinformatics analysis, we examined the DDR1 expression and the correlation of CXCL5 with immune cell infiltration in breast cancer. It was found that high DDR1 expression was correlated with poor prognosis of patients with breast cancer, and CXCL5 was positively correlated with neutrophil and Treg infiltration. Expression of DDR1 and CXCL5 was determined in collagen-treated breast cancer cells, the malignant phenotypes of which were evaluated by ectopic expression and knockdown methods. Collagen-activated DDR1 upregulated CXCL5 expression, resulting in augmented malignant phenotypes of breast cancer cells in vitro. The formation of NETs caused promotion in the differentiation and immune infiltration of Tregs in breast cancer. A in situ breast cancer mouse model was constructed, where NET formation and lung metastasis of breast cancer cells were observed. The differentiation of CD4+ T cells isolated from the mouse model was induced into Tregs, followed by Treg infiltration assessment. It was further confirmed in vivo that DDR1/CXCL5 induced the formation of NETs to promote immune infiltration of Tregs, driving tumor growth and metastasis. Accordingly, our results provided new mechanistic insights for an understanding of the role of collagen-mediated DDR1/CXCL5 in formation of NETs and Treg infiltration, revealing potential targets for therapeutic intervention of breast cancer.

PROTACs in Epigenetic Cancer Therapy: Current Status and Future Opportunities

The epigenetic regulation of gene functions has been proven to be strongly associated with the development and progression of cancer. Reprogramming the cancer epigenome landscape is one of the most promising target therapies in both treatments and in reversing drug resistance. Proteolytic targeted chimeras (PROTACs) are an emerging therapeutic modality for selective degradation via the native ubiquitin-proteasome system. Rapid advances in PROTACs have facilitated the exploration of targeting epigenetic proteins, a lot of PROTAC degraders have already been designed in the field of epigenetic cancer therapy, and PROTACs targeting epigenetic proteins can better exploit target druggability and improve the mechanistic understanding of the epigenetic regulation of cancer. Thus, this review focuses on the progress made in the development of PROTAC degraders and PROTAC drugs targeting epigenetics in cancer and discusses challenges and future opportunities for the field.

Human WDR5 promotes breast cancer growth and metastasis via KMT2-independent translation regulation

Metastatic breast cancer remains a major cause of cancer-related deaths in women, and there are few effective therapies against this advanced disease. Emerging evidence suggests that key steps of tumor progression and metastasis are controlled by reversible epigenetic mechanisms. Using an in vivo genetic screen, we identified WDR5 as an actionable epigenetic regulator that is required for metastatic progression in models of triple-negative breast cancer. We found that knockdown of WDR5 in breast cancer cells independently impaired their tumorigenic as well as metastatic capabilities. Mechanistically, WDR5 promotes cell growth by increasing ribosomal gene expression and translation efficiency in a KMT2-independent manner. Consistently, pharmacological inhibition or degradation of WDR5 impedes cellular translation rate and the clonogenic ability of breast cancer cells. Furthermore, a combination of WDR5 targeting with mTOR inhibitors leads to potent suppression of translation and proliferation of breast cancer cells. These results reveal novel therapeutic strategies to treat metastatic breast cancer.