A MYC inhibitor selectively alters the MYC and MAX cistromes and modulates the epigenomic landscape to regulate target gene expression

Co-targeting BMI1 and MYC to eliminate cancer stem cells in squamous cell carcinoma

Bmi1+ tumor cells act as cancer stem cells (CSCs) driving relapse and therapy resistance in head and neck squamous cell carcinoma (HNSCC). Although BMI1 inhibitors reduce CSCs, combined cisplatin treatment targeting non-stem tumor cells is more effective in eliminating CSCs. Non-stem tumor cells may revert to CSCs post-treatment. However, in vivo evidence and underlying mechanisms remain unclear. Here, we demonstrate that BMI1 inhibitors induce temporary tumor regression followed by relapse. Lineage tracing reveals that keratin 16-marked non-stem tumor cells revert to Bmi1+ CSCs, which drive compensatory tumor growth after BMI1 targeting therapy. Mechanistically, BMI1 inhibitors activate DNA damage/nuclear factor κB (NF-κB) signaling and inflammatory cytokine secretion, subsequently stimulating myelocytomatosis viral oncogene homolog (MYC) expression in non-stem tumor cells to promote the reversion process. Genetic and pharmacological inhibition of MYC synergizes with BMI1 targeting, achieving sustained CSC eradication and relapse prevention. These findings provide insights into CSCs' plasticity and suggest dual BMI1/MYC blockade as an effective HNSCC treatment strategy.

Artesunate enhances the efficacy of enzalutamide in advanced prostate cancer

Prostate cancer (PCa) is one of the leading causes of death among men worldwide. Treatments targeting the androgen receptor pathway remain the standard therapy for PCa patients. Enzalutamide (ENZ), a second-generation androgen receptor inhibitor, was developed to treat castration-resistant prostate cancer. However, while patients initially respond to ENZ, drug resistance typically develops within a few months. Artesunate (ART), a semisynthetic derivative of the Artemisinin plant, is approved for antimalaria treatment. In this study, we conducted an FDA-approved drug screening and identified ART as a potential candidate for overcoming ENZ resistance in PCa. Mechanistically, ART induces the degradation of c-Myc, enhancing the efficacy of ENZ. Additionally, patient dataset analysis revealed that c-Myc plays a significant role in developing ENZ resistance. To summarize, these findings suggest a novel therapeutic strategy for ENZ-resistant prostate cancer.

Targeting senescent stemlike subpopulations in Philadelphia chromosome-like acute lymphoblastic leukemia

ABSTRACT

Philadelphia chromosome-like B-cell acute lymphoblastic leukemia (Ph-like ALL) is driven by genetic alterations that induce constitutive kinase signaling and is associated with chemoresistance and high relapse risk in children and adults. Preclinical studies in the most common CRLF2-rearranged/JAK pathway-activated Ph-like ALL subtype have revealed variable responses to JAK inhibitor-based therapies, suggesting incomplete oncogene addiction and highlighting a need to elucidate alternative biologic dependencies and therapeutic vulnerabilities, whereas the ABL-class Ph-like ALL subtype seems preferentially sensitive to SRC/ABL- or PDGFRB-targeting inhibitors. Which patients may be responsive vs resistant to tyrosine kinase inhibitor (TKI)-based precision medicine approaches remains a critical knowledge gap. Using bulk and single-cell multiomics analyses, we profiled residual cells from CRLF2-rearranged or ABL1-rearranged Ph-like ALL patient-derived xenograft models treated in vivo with targeted inhibitors to identify TKI-resistant subpopulations and potential mechanisms of therapeutic escape. We detected a specific MYC dependency in Ph-like ALL cells and defined a new leukemia cell subpopulation with senescence-associated stem cell-like features regulated by AP-1 transcription factors. This dormant ALL subpopulation was effectively eradicated by dual pharmacologic inhibition of BCL-2 and JAK/STAT or SRC/ABL pathways, a clinically relevant therapeutic strategy. Single cell-derived molecular signatures of this senescence and stem/progenitor-like subpopulation further predicted poor clinical outcomes associated with other high-risk genetic subtypes of childhood B-ALL and thus may have broader prognostic applicability beyond Ph-like ALL.

Inhibition of PSF Activity Overcomes Resistance to Treatment in Cancers Harboring Mutant p53

Mutations in the TP53 tumor suppressor genes are prevalent in aggressive cancers. Pharmacologic reactivation of dysfunctional p53 due to mutations is a promising strategy for treating such cancers. Recently, a multifunctional proline- and glutamine-rich protein, polypyrimidine tract-binding protein-associated splicing factor (PSF), was identified as a key driver of aggressive cancers. PSF promotes the expression of numerous oncogenes by modulating epigenetic and splicing mechanisms. We previously screened a small-molecule library and discovered compound No. 10-3 as a potent PSF inhibitor. Here, we report the discovery of a No. 10-3 analog, 7,8-dimethoxy-4-(4-methoxy-phenyl)-chromen-2-one (C-30), as a potent PSF inhibitor. Compared with No. 10-3, C-30 treatment specifically suppressed the growth and induced apoptosis of mutant p53-bearing and therapy-resistant cancer cells. Interestingly, C-30 activated a set of p53-regulated genes in therapy-resistant cancer cells. A comprehensive analysis of PSF and p53-binding regions demonstrated a higher level of PSF-binding potential in mutant p53-expressing cancer cells around genomic regions identified as p53-binding peaks in p53 wild-type cancer cells. Treatment of mutant p53-expressing cancer cells with C-30 decreases PSF binding around these sites, leading to activated histone acetylation. We further demonstrated that C-30 impaired tumor growth and increased the expression of p53 target genes in vivo. These results suggested that C-30 produces tumor-suppressive effects similar to the functional reactivation of p53, providing a rationale for the inhibition of PSF activity as a promising therapy against treatment-resistant cancer.

Recent Advances in Pineoblastoma Research: Molecular Classification, Modelling and Targetable Vulnerabilities

Pineoblastoma (PB) is a rare yet lethal pediatric brain cancer of the pineal gland, a small endocrine organ that secretes melatonin to regulate the circadian rhythm. For PB patients ≤5 years of age, the overall survival rate is approximately 15%; metastatic PB is incurable. Standard treatment, including surgical resection, radiation, and systemic chemotherapy, improves survival but compromises neurocognitive function. A better understanding of the disease and the generation of preclinical models may enable re-evaluation of previous clinical trials, development of precision therapeutic strategies and improve patient outcome. Over the past 5 years, PB has been recognized to include several major subtypes driven by (i) loss of microRNA processing factors DICER and DROSHA characterized by a relatively good prognosis; (ii) loss of the retinoblastoma tumor suppressor RB1; and (iii) amplification or induction of the cMYC protooncogene, with the latter two subtypes exhibiting exceedingly poor prognosis. Recently, mouse models for the major PB subtypes (RB1-, DICER1- and DROSHA-) except MYC- have been established. This progress, including better understanding of the disease, cell of origin, tumor progression, role of autophagy, and targetable vulnerabilities, holds promise for novel therapeutic strategies to combat each subtype of this lethal childhood malignancy.

MYC in cancer: from undruggable target to clinical trials

MYC is among the most infamous oncogenes in cancer. A notable feature that distinguishes it from other common oncogenes is that its deregulation is not usually due to direct mutation, but instead to its relentless activation by other oncogenic lesions. These signalling pathways funnel through MYC to execute the transcriptional programmes that eventually lead to the uncontrolled proliferation of cancer cells. Indeed, deregulated MYC activity may be linked to most - if not all - human cancers. Despite this unquestionable role of MYC in tumour development and maintenance, no MYC inhibitor has yet been approved for clinical use. The main reason is that MYC has long fallen into the category of 'undruggable' or 'difficult-to-drug' targets, mainly because of its intrinsically disordered structure, which is not amenable to traditional drug development strategies. However, in recent years, attempts to develop MYC inhibitors have multiplied, and the first clinical trials have been testing their efficacy in patients. We are finally reaching the point at which its inhibition seems clinically viable. This Review provides an overview of the various strategies to inhibit MYC, focusing on the most recently described inhibitors and those that have reached clinical trials.

Transcriptional regulation by MYC: an emerging new model

The transcription factor MYC has long been recognized for its pivotal role in transcriptional regulation of genes fundamental for cellular processes such as cell cycle, apoptosis, and metabolism. Dysregulation of MYC activity is implicated in various diseases, most notably cancer, where MYC drives uncontrolled cell proliferation and growth. Despite its significant role in cancer biology, targeting MYC for therapeutic purposes has been challenging due to its highly disordered protein structure. Hence, recent research efforts have focused on identifying the transcriptional mechanisms underlying MYC function to identify alternative strategies for intervention. This review summarizes recent advances in our understanding of how MYC orchestrates context-dependent and -independent gene-regulatory activities in cancer. Based on recent insights into the gene-regulatory function of MYC at enhancers, we propose an extension of the gene-specific affinity model. In this revised model, MYC enhancer activity drives context-specific gene programs that are distinct from the ubiquitously activated set of core MYC target genes driven by MYC promoter binding. The increased MYC enhancer activity in cancer and the distinct function of MYC at these regions compared to promoters may provide an opportunity for designing therapeutic approaches selectively targeting MYC enhancer activity in cancer cells.

Chromatin accessibility: biological functions, molecular mechanisms and therapeutic application

The dynamic regulation of chromatin accessibility is one of the prominent characteristics of eukaryotic genome. The inaccessible regions are mainly located in heterochromatin, which is multilevel compressed and access restricted. The remaining accessible loci are generally located in the euchromatin, which have less nucleosome occupancy and higher regulatory activity. The opening of chromatin is the most important prerequisite for DNA transcription, replication, and damage repair, which is regulated by genetic, epigenetic, environmental, and other factors, playing a vital role in multiple biological progresses. Currently, based on the susceptibility difference of occupied or free DNA to enzymatic cleavage, solubility, methylation, and transposition, there are many methods to detect chromatin accessibility both in bulk and single-cell level. Through combining with high-throughput sequencing, the genome-wide chromatin accessibility landscape of many tissues and cells types also have been constructed. The chromatin accessibility feature is distinct in different tissues and biological states. Research on the regulation network of chromatin accessibility is crucial for uncovering the secret of various biological processes. In this review, we comprehensively introduced the major functions and mechanisms of chromatin accessibility variation in different physiological and pathological processes, meanwhile, the targeted therapies based on chromatin dynamics regulation are also summarized.

Engineered uterine primary myometrial cells with high-mobility group AT-hook 2 overexpression display a leiomyoma-like transcriptional and epigenomic phenotype

OBJECTIVE

To determine if engineered high-mobility group AT-hook 2 (HMGA2) overexpressing uterine primary myometrial cells recapitulate the transcriptional and epigenomic features of HMGA2-subtype leiomyomas.

DESIGN

Isolated primary, "normal" myometrial cells from three patients were engineered to overexpress HMGA2 to determine how HMGA2 establishes transcriptomic and epigenomic features of HMGA2-overexpressing leiomyoma.

SETTING

Academic research laboratory.

PATIENT(S)

Primary myometrial cells were isolated from normal myometrium obtained from three patients undergoing hysterectomy.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

Determined genome-wide transcriptomic and epigenomic features of engineered HMGA2-overexpressing uterine primary myometrial cells.

RESULT(S)

Engineered HMGA2-V5-overexpressing primary myometrial cells approximated the HMGA2 expression level observed in HMGA2-overexpression subtype leiomyoma. High-mobility group AT-hook 2-V5 expression resulted in differential expression of 1,612 genes (false discovery rate [FDR] < 0.05) that were found to be enriched in pathways associated with leiomyoma formation, including extracellular matrix organization. Comparative gene expression analysis between HMGA2-V5 engineered primary cells and HMGA2-overexpression subtype leiomyoma revealed significant overlap of differentially expressed genes. Mechanistically, HMGA2-V5 overexpression resulted in 41,323 regions with differential H3K27ac deposition (FDR < 0.05) and 205,605 regions of altered chromatin accessibility (FDR < 0.05). Transcription factor binding site analysis implicated the AP-1 family of transcription factors.

CONCLUSION(S)

High-mobility group AT-hook 2 overexpression induces leiomyoma-like transcriptomic and epigenomic modulations in myometrial cells.

Asparagine Dependency Is a Targetable Metabolic Vulnerability in TP53-Altered Castration-Resistant Prostate Cancer

TP53 tumor suppressor is frequently altered in lethal, castration-resistant prostate cancer (CRPC). However, to date there are no effective treatments that specifically target TP53 alterations. Using transcriptomic and metabolomic analyses, we have shown here that TP53-altered prostate cancer exhibits an increased dependency on asparagine (Asn) and overexpresses Asn synthetase (ASNS), the enzyme catalyzing the synthesis of Asn. Mechanistically, the loss or mutation of TP53 transcriptionally activated ASNS expression, directly and via mTORC1-mediated ATF4 induction, driving de novo Asn biosynthesis to support CRPC growth. TP53-altered CRPC cells were sensitive to Asn restriction by knockdown of ASNS or L-asparaginase treatment to deplete the intracellular and extracellular sources of Asn, respectively, and cell viability was rescued by Asn addition. Notably, pharmacological inhibition of intracellular Asn biosynthesis using a glutaminase inhibitor and depletion of extracellular Asn with L-asparaginase significantly reduced Asn production and effectively impaired CRPC growth. This study highlights the significance of ASNS-mediated metabolic adaptation as a synthetic vulnerability in CRPC with TP53 alterations, providing a rationale for targeting Asn production to treat these lethal prostate cancers. Significance: TP53-mutated castration-resistant prostate cancer is dependent on asparagine biosynthesis due to upregulation of ASNS and can be therapeutically targeted by approaches that deplete intracellular and extracellular asparagine.

GRP78 inhibitor YUM70 upregulates 4E-BP1 and suppresses c-MYC expression and viability of oncogenic c-MYC tumors

The 78-kDa glucose regulated protein (GRP78) commonly upregulated in a wide variety of tumors is an important prognostic marker and a promising target for suppressing tumorigenesis and treatment resistance. While GRP78 is well established as a major endoplasmic reticulum (ER) chaperone with anti-apoptotic properties and a master regulator of the unfolded protein response, its new role as a regulator of oncoprotein expression is just emerging. MYC is dysregulated in about 70 % of human cancers and is the most commonly activated oncoprotein. However, despite recent advances, therapeutic targeting of MYC remains challenging. Here we identify GRP78 as a new target for suppression of MYC expression. Using multiple MYC-dependent cancer models including head and neck squamous cell carcinoma and their cisplatin-resistant clones, breast and pancreatic adenocarcinoma, our studies revealed that GRP78 knockdown by siRNA or inhibition of its activity by small molecule inhibitors (YUM70 or HA15) reduced c-MYC expression, leading to onset of apoptosis and loss of cell viability. This was observed in 2D cell culture, 3D spheroid and in xenograft models. Mechanistically, we determined that the suppression of c-MYC is at the post-transcriptional level and that YUM70 and HA15 treatment potently upregulated the eukaryotic translation inhibitor 4E-BP1, which targets eIF4E critical for c-MYC translation initiation. Furthermore, knock-down of 4E-BP1 via siRNA rescued YUM70-mediated c-MYC suppression. As YUM70 is also capable of suppressing N-MYC expression, this study offers a new approach to suppress MYC protein expression through knockdown or inhibition of GRP78.

Disrupting prostate cancer research: Challenge accepted; report from the 2023 Coffey-Holden Prostate Cancer Academy Meeting

INTRODUCTION

The 2023 Coffey-Holden Prostate Cancer Academy (CHPCA) Meeting, themed "Disrupting Prostate Cancer Research: Challenge Accepted," was convened at the University of California, Los Angeles, Luskin Conference Center, in Los Angeles, CA, from June 22 to 25, 2023.

METHODS

The 2023 marked the 10th Annual CHPCA Meeting, a discussion-oriented scientific think-tank conference convened annually by the Prostate Cancer Foundation, which centers on innovative and emerging research topics deemed pivotal for advancing critical unmet needs in prostate cancer research and clinical care. The 2023 CHPCA Meeting was attended by 81 academic investigators and included 40 talks across 8 sessions.

RESULTS

The central topic areas covered at the meeting included: targeting transcription factor neo-enhancesomes in cancer, AR as a pro-differentiation and oncogenic transcription factor, why few are cured with androgen deprivation therapy and how to change dogma to cure metastatic prostate cancer without castration, reducing prostate cancer morbidity and mortality with genetics, opportunities for radiation to enhance therapeutic benefit in oligometastatic prostate cancer, novel immunotherapeutic approaches, and the new era of artificial intelligence-driven precision medicine.

DISCUSSION

This article provides an overview of the scientific presentations delivered at the 2023 CHPCA Meeting, such that this knowledge can help in facilitating the advancement of prostate cancer research worldwide.

MYC Binding Near Transcriptional End Sites Regulates Basal Gene Expression, Read-Through Transcription and Intragenic Contacts

The MYC oncoprotein regulates numerous genes involved in cellular processes such as cell cycle and mitochondrial and ribosomal structure and function. This requires heterodimerization with its partner, MAX, and binding to specific promoter and enhancer elements. Here, we show that MYC and MAX also bind near transcriptional end sites (TESs) of over one-sixth of all annotated genes. These interactions are dose-dependent, evolutionarily conserved, stabilize the normally short-lived MYC protein and regulate expression both in concert with and independent of MYC's binding elsewhere. MYC's TES binding occurs in association with other transcription factors, alters the chromatin landscape, increases nuclease susceptibility and can alter transcriptional read-through, particularly in response to certain stresses. MYC-bound TESs can directly contact promoters and may fine-tune gene expression in response to both physiologic and pathologic stimuli. Collectively, these findings support a previously unrecognized role for MYC in regulating transcription and its read-through via direct intragenic contacts between TESs and promoters.

Transcription Factors in Prostate Cancer: Insights for Disease Development and Diagnostic and Therapeutic Approaches

Transcription factors (TFs) are proteins essential for the regulation of gene expression, and they regulate the genes involved in different cellular processes, such as proliferation, differentiation, survival, and apoptosis. Although their expression is essential in normal physiological conditions, abnormal regulation of TFs plays critical role in several diseases, including cancer. In prostate cancer, the most common malignancy in men, TFs are known to play crucial roles in the initiation, progression, and resistance to therapy of the disease. Understanding the interplay between these TFs and their downstream targets provides insights into the molecular basis of prostate cancer pathogenesis. In this review, we discuss the involvement of key TFs, including the E26 Transformation-Specific (ETS) Family (ERG and SPDEF), NF-κB, Activating Protein-1 (AP-1), MYC, and androgen receptor (AR), in prostate cancer while focusing on the molecular mechanisms involved in prostate cancer development. We also discuss emerging diagnostic strategies, early detection, and risk stratification using TFs. Furthermore, we explore the development of therapeutic interventions targeting TF pathways, including the use of small molecule inhibitors, gene therapies, and immunotherapies, aimed at disrupting oncogenic TF signaling and improving patient outcomes. Understanding the complex regulation of TFs in prostate cancer provides valuable insights into disease biology, which ultimately may lead to advancing precision approaches for patients.

Development, synthesis and validation of improved c-Myc/Max inhibitors

The pathophysiological foundations of various diseases are often subject to alteration through the utilization of small compounds, rendering them invaluable tools for the exploration and advancement of novel therapeutic strategies. Within the scope of this study, we meticulously curated a diverse library of novel small compounds meticulously designed to specifically target the c-Myc/Max complex. We conducted in vitro examinations of novel c-Myc inhibitors across a spectrum of cancer cell lines, including PANC1 (pancreatic adenocarcinoma), MCF7 (breast carcinoma), DU-145 (prostate carcinoma), and A549 (lung cancer). The initial analysis involved a 25 μM dose, which enabled the identification of potent anticancer compounds effective against a variety of tumour types. We identified c-Myc inhibitors with remarkable potency, featuring IC50 values as low as 1.6 μM and up to 40 times more effective than the reference molecule in diminishing cancer cell viability. Notably, c-Myc-i7 exhibited exceptional selectivity, displaying 37-fold and 59-fold preference for targeting prostate and breast cancers, respectively, over healthy cells. Additionally, we constructed drug-likeness models. This study underscores the potential for in vitro investigations of various tumour types using novel c-Myc inhibitors to yield ground-breaking and efficacious anticancer compounds.

Radiotherapy-Induced Astrocyte Senescence Promotes an Immunosuppressive Microenvironment in Glioblastoma to Facilitate Tumor Regrowth

Accumulating evidence suggests that changes in the tumor microenvironment caused by radiotherapy are closely related to the recurrence of glioma. However, the mechanisms by which such radiation-induced changes are involved in tumor regrowth have not yet been fully investigated. In the present study, how cranial irradiation-induced senescence in non-neoplastic brain cells contributes to glioma progression is explored. It is observed that senescent brain cells facilitated tumor regrowth by enhancing the peripheral recruitment of myeloid inflammatory cells in glioblastoma. Further, it is identified that astrocytes are one of the most susceptible senescent populations and that they promoted chemokine secretion in glioma cells via the senescence-associated secretory phenotype. By using senolytic agents after radiotherapy to eliminate these senescent cells substantially prolonged survival time in preclinical models. The findings suggest the tumor-promoting role of senescent astrocytes in the irradiated glioma microenvironment and emphasize the translational relevance of senolytic agents for enhancing the efficacy of radiotherapy in gliomas.

Mechanism-centric regulatory network identifies NME2 and MYC programs as markers of Enzalutamide resistance in CRPC

Heterogeneous response to Enzalutamide, a second-generation androgen receptor signaling inhibitor, is a central problem in castration-resistant prostate cancer (CRPC) management. Genome-wide systems investigation of mechanisms that govern Enzalutamide resistance promise to elucidate markers of heterogeneous treatment response and salvage therapies for CRPC patients. Focusing on the de novo role of MYC as a marker of Enzalutamide resistance, here we reconstruct a CRPC-specific mechanism-centric regulatory network, connecting molecular pathways with their upstream transcriptional regulatory programs. Mining this network with signatures of Enzalutamide response identifies NME2 as an upstream regulatory partner of MYC in CRPC and demonstrates that NME2-MYC increased activities can predict patients at risk of resistance to Enzalutamide, independent of co-variates. Furthermore, our experimental investigations demonstrate that targeting MYC and its partner NME2 is beneficial in Enzalutamide-resistant conditions and could provide an effective strategy for patients at risk of Enzalutamide resistance and/or for patients who failed Enzalutamide treatment.

Oncogenic role of FOXM1 in human prostate cancer (Review)

Prostate cancer is the leading cause of cancer‑related mortality among men worldwide. In particular, castration‑resistant prostate cancer presents a formidable clinical challenge and emphasizes the need to develop novel therapeutic strategies. Forkhead box M1 (FOXM1) is a multifaceted transcription factor that is implicated in the acquisition of the multiple cancer hallmark capabilities in prostate cancer cells, including sustaining proliferative signaling, resisting cell death and the activation of invasion and metastasis. Elevated FOXM1 expression is frequently observed in prostate cancer, and in particular, FOXM1 overexpression is closely associated with poor clinical outcomes in patients with prostate cancer. In the present review, recent advances in the understanding of the oncogenic role of deregulated FOXM1 expression in prostate cancer were highlighted. In addition, the molecular mechanisms by which FOXM1 regulates prostate cancer development and progression were described, thereby providing knowledge and a conceptual framework for FOXM1. The present review also provided valuable insight into the inherent challenges associated with translating biomedical knowledge into effective therapeutic strategies for prostate cancer.

Pharmacological inhibition of MYC to mitigate chemoresistance in preclinical models of squamous cell carcinoma

Rationale: Cisplatin-based chemotherapy is the first-line treatment for late-stage head and neck squamous cell carcinoma (HNSCC). However, resistance to cisplatin has become a major obstacle for effective therapy. Cancer stem cells (CSCs) are critical for tumor initiation, growth, metastasis, and chemoresistance. How to effectively eliminate CSCs and overcome chemoresistance remains a key challenge. Herein, we confirmed that MYC plays critical roles in chemoresistance, and explored targeting MYC to overcome cisplatin resistance in preclinical models. Methods: The roles of MYC in HNSCC cisplatin resistance and cancer stemness were tested in vitro and in vivo. The combined therapeutic efficiency of MYC targeting using the small molecule MYC inhibitor MYCi975 and cisplatin was assessed in a 4‑nitroquinoline 1-oxide-induced model and in a patient-derived xenograft model. Results: MYC was highly-expressed in cisplatin-resistant HNSCC. Targeting MYC using MYCi975 eliminated CSCs, prevented metastasis, and overcame cisplatin resistance. MYCi975 also induced tumor cell-intrinsic immune responses, and promoted CD8+ T cell infiltration. Mechanistically, MYCi975 induced the DNA damage response and activated the cGAS-STING-IRF3 signaling pathway to increase CD8+ T cell-recruiting chemokines. Conclusions: Our findings suggested that targeting MYC might eliminate CSCs, prevent metastasis, and activate antitumor immunity to overcome cisplatin resistance in HNSCC.

MYC-driven increases in mitochondrial DNA copy number occur early and persist throughout prostatic cancer progression

Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type-specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by 2 orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.

Deep-Learning Terahertz Single-Cell Metabolic Viability Study

Cell viability assessment is critical, yet existing assessments are not accurate enough. We report a cell viability evaluation method based on the metabolic ability of a single cell. Without culture medium, we measured the absorption of cells to terahertz laser beams, which could target a single cell. The cell viability was assessed with a convolution neural classification network based on cell morphology. We established a cell viability assessment model based on the THz-AS (terahertz-absorption spectrum) results as y = a = (x - b)c, where x is the terahertz absorbance and y is the cell viability, and a, b, and c are the fitting parameters of the model. Under water stress the changes in terahertz absorbance of cells corresponded one-to-one with the apoptosis process, and we propose a cell 0 viability definition as terahertz absorbance remains unchanged based on the cell metabolic mechanism. Compared with typical methods, our method is accurate, label-free, contact-free, and almost interference-free and could help visualize the cell apoptosis process for broad applications including drug screening.

MYC function and regulation in physiological perspective

MYC, a key member of the Myc-proto-oncogene family, is a universal transcription amplifier that regulates almost every physiological process in a cell including cell cycle, proliferation, metabolism, differentiation, and apoptosis. MYC interacts with several cofactors, chromatin modifiers, and regulators to direct gene expression. MYC levels are tightly regulated, and deregulation of MYC has been associated with numerous diseases including cancer. Understanding the comprehensive biology of MYC under physiological conditions is an utmost necessity to demark biological functions of MYC from its pathological functions. Here we review the recent advances in biological mechanisms, functions, and regulation of MYC. We also emphasize the role of MYC as a global transcription amplifier.

Design and Characterization of pMyc/pMax Peptide-Coupled Gold Nanosystems for Targeting Myc in Prostate Cancer Cell Lines

Myc and Max are essential proteins in the development of prostate cancer. They act by dimerizing and binding to E-box sequences. Disrupting the Myc:Max heterodimer interaction or its binding to E-box sequences to interrupt gene transcription represent promising strategies for treating cancer. We designed novel pMyc and pMax peptides from reference sequences, and we evaluated their ability to bind specifically to E-box sequences using an electrophoretic mobility shift assay (EMSA). Then, we assembled nanosystems (NSs) by coupling pMyc and pMax peptides to AuNPs, and determined peptide conjugation using UV-Vis spectroscopy. After that, we characterized the NS to obtain the nanoparticle's size, hydrodynamic diameter, and zeta potential. Finally, we evaluated hemocompatibility and cytotoxic effects in three different prostate adenocarcinoma cell lines (LNCaP, PC-3, and DU145) and a non-cancerous cell line (Vero CCL-81). EMSA results suggests peptide-nucleic acid interactions between the pMyc:pMax dimer and the E-box. The hemolysis test showed little hemolytic activity for the NS at the concentrations (5, 0.5, and 0.05 ng/µL) we evaluated. Cell viability assays showed NS cytotoxicity. Overall, results suggest that the NS with pMyc and pMax peptides might be suitable for further research regarding Myc-driven prostate adenocarcinomas.

In vivo screening characterizes chromatin factor functions during normal and malignant hematopoiesis

Cellular differentiation requires extensive alterations in chromatin structure and function, which is elicited by the coordinated action of chromatin and transcription factors. By contrast with transcription factors, the roles of chromatin factors in differentiation have not been systematically characterized. Here, we combine bulk ex vivo and single-cell in vivo CRISPR screens to characterize the role of chromatin factor families in hematopoiesis. We uncover marked lineage specificities for 142 chromatin factors, revealing functional diversity among related chromatin factors (i.e. barrier-to-autointegration factor subcomplexes) as well as shared roles for unrelated repressive complexes that restrain excessive myeloid differentiation. Using epigenetic profiling, we identify functional interactions between lineage-determining transcription factors and several chromatin factors that explain their lineage dependencies. Studying chromatin factor functions in leukemia, we show that leukemia cells engage homeostatic chromatin factor functions to block differentiation, generating specific chromatin factor-transcription factor interactions that might be therapeutically targeted. Together, our work elucidates the lineage-determining properties of chromatin factors across normal and malignant hematopoiesis.

E-box binding transcription factors in cancer

E-boxes are important regulatory elements in the eukaryotic genome. Transcription factors can bind to E-boxes through their basic helix-loop-helix or zinc finger domain to regulate gene transcription. E-box-binding transcription factors (EBTFs) are important regulators of development and essential for physiological activities of the cell. The fundamental role of EBTFs in cancer has been highlighted by studies on the canonical oncogene MYC, yet many EBTFs exhibit common features, implying the existence of shared molecular principles of how they are involved in tumorigenesis. A comprehensive analysis of TFs that share the basic function of binding to E-boxes has been lacking. Here, we review the structure of EBTFs, their common features in regulating transcription, their physiological functions, and their mutual regulation. We also discuss their converging functions in cancer biology, their potential to be targeted as a regulatory network, and recent progress in drug development targeting these factors in cancer therapy.

FOXM1: A small fox that makes more tracks for cancer progression and metastasis

Transcription factors (TFs) are indispensable for the modulation of various signaling pathways associated with normal cell homeostasis and disease conditions. Among cancer-related TFs, FOXM1 is a critical molecule that regulates multiple aspects of cancer cells, including growth, metastasis, recurrence, and stem cell features. FOXM1 also impact the outcomes of targeted therapies, chemotherapies, and immune checkpoint inhibitors (ICIs) in various cancer types. Recent advances in cancer research strengthen the cancer-specific role of FOXM1, providing a rationale to target FOXM1 for developing targeted therapies. This review compiles the recent studies describing the pivotal role of FOXM1 in promoting metastasis of various cancer types. It also implicates the contribution of FOXM1 in the modulation of chemotherapeutic resistance, antitumor immune response/immunotherapies, and the potential of small molecule inhibitors of FOXM1.

Discovery and Structure-Based Design of Inhibitors of the WD Repeat-Containing Protein 5 (WDR5)-MYC Interaction

WDR5 is a critical chromatin cofactor of MYC. WDR5 interacts with MYC through the WBM pocket and is hypothesized to anchor MYC to chromatin through its WIN site. Blocking the interaction of WDR5 and MYC impairs the recruitment of MYC to its target genes and disrupts the oncogenic function of MYC in cancer development, thus providing a promising strategy for the treatment of MYC-dysregulated cancers. Here, we describe the discovery of novel WDR5 WBM pocket antagonists containing a 1-phenyl dihydropyridazinone 3-carboxamide core that was identified from high-throughput screening and subsequent structure-based design. The leading compounds showed sub-micromolar inhibition in the biochemical assay. Among them, compound 12 can disrupt WDR5-MYC interaction in cells and reduce MYC target gene expression. Our work provides useful probes to study WDR5-MYC interaction and its function in cancers, which can also be used as the starting point for further optimization toward drug-like small molecules.

Identification of small-molecule inhibitors against the interaction of RNA-binding protein PSF and its target RNA for cancer treatment

Diverse cellular activities are modulated through a variety of RNAs, including long noncoding RNAs (lncRNAs), by binding to certain proteins. The inhibition of oncogenic proteins or RNAs is expected to suppress cancer cell proliferation. We have previously demonstrated that PSF interaction with its target RNAs, such as androgen-induced lncRNA CTBP1-AS, is critical for hormone therapy resistance in prostate and breast cancers. However, the action of protein-RNA interactions remains almost undruggable to date. High-throughput screening (HTS) has facilitated the discovery of drugs for protein-protein interactions. In the present study, we developed an in vitro alpha assay using Flag peptide-conjugated lncRNA, CTBP1-AS, and PSF. We then constructed an effective HTS screening system to explore small compounds that inhibit PSF-RNA interactions. Thirty-six compounds were identified and dose-dependently inhibited PSF-RNA interaction in vitro. Moreover, chemical optimization of these lead compounds and evaluation of cancer cell proliferation revealed two promising compounds, N-3 and C-65. These compounds induced apoptosis and inhibited cell growth in prostate and breast cancer cells. By inhibiting PSF-RNA interaction, N-3 and C-65 up-regulated signals that are repressed by PSF, such as the cell cycle signals by p53 and p27. Furthermore, using a mouse xenograft model for hormone therapy-resistant prostate cancer, we revealed that N-3 and C-65 can significantly suppress tumor growth and downstream target gene expression, such as the androgen receptor (AR). Thus, our findings highlight a therapeutic strategy through the development of inhibitors for RNA-binding events in advanced cancers.

Targeting Myc-driven stress addiction in colorectal cancer

MYC is a proto-oncogene that encodes a powerful regulator of transcription and cellular programs essential for normal development, as well as the growth and survival of various types of cancer cells. MYC rearrangement and amplification is a common cause of hematologic malignancies. In epithelial cancers such as colorectal cancer, genetic alterations in MYC are rare. Activation of Wnt, ERK/MAPK, and PI3K/mTOR pathways dramatically increases Myc levels through enhanced transcription, translation, and protein stability. Elevated Myc promotes stress adaptation, metabolic reprogramming, and immune evasion to drive cancer development and therapeutic resistance through broad changes in transcriptional and translational landscapes. Despite intense interest and effort, Myc remains a difficult drug target. Deregulation of Myc and its targets has profound effects that vary depending on the type of cancer and the context. Here, we summarize recent advances in the mechanistic understanding of Myc-driven oncogenesis centered around mRNA translation and proteostress. Promising strategies and agents under development to target Myc are also discussed with a focus on colorectal cancer.

MYC-driven increases in mitochondrial DNA copy number occur early and persist throughout prostatic cancer progression

Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by two orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.

In Vivo Modeling of CLL Transformation to Richter Syndrome Reveals Convergent Evolutionary Paths and Therapeutic Vulnerabilities

Transformation to aggressive disease histologies generates formidable clinical challenges across cancers, but biological insights remain few. We modeled the genetic heterogeneity of chronic lymphocytic leukemia (CLL) through multiplexed in vivo CRISPR-Cas9 B-cell editing of recurrent CLL loss-of-function drivers in mice and recapitulated the process of transformation from indolent CLL into large cell lymphoma [i.e., Richter syndrome (RS)]. Evolutionary trajectories of 64 mice carrying diverse combinatorial gene assortments revealed coselection of mutations in Trp53, Mga, and Chd2 and the dual impact of clonal Mga/Chd2 mutations on E2F/MYC and interferon signaling dysregulation. Comparative human and murine RS analyses demonstrated tonic PI3K signaling as a key feature of transformed disease, with constitutive activation of the AKT and S6 kinases, downmodulation of the PTEN phosphatase, and convergent activation of MYC/PI3K transcriptional programs underlying enhanced sensitivity to MYC/mTOR/PI3K inhibition. This robust experimental system presents a unique framework to study lymphoid biology and therapy.

SIGNIFICANCE

Mouse models reflective of the genetic complexity and heterogeneity of human tumors remain few, including those able to recapitulate transformation to aggressive disease histologies. Herein, we model CLL transformation into RS through multiplexed in vivo gene editing, providing key insight into the pathophysiology and therapeutic vulnerabilities of transformed disease. This article is highlighted in the In This Issue feature, p. 101.

Therapeutic Targeting of MYC in Head and Neck Squamous Cell Carcinoma

MYC plays critical roles in tumorigenesis and is considered an attractive cancer therapeutic target. Small molecules that directly target MYC and are well tolerated in vivo represent invaluable anti-cancer therapeutic agents. Here, we aimed to investigate the therapeutic effect of MYC inhibitors in head and neck squamous cell carcinoma (HNSCC). The results showed that pharmacological and genetic inhibition of MYC inhibited HNSCC proliferation and migration. MYC inhibitor 975 (MYCi975), inhibited HNSCC growth in both cell line-derived xenograft and syngeneic murine models. MYC inhibition also induced tumor cell-intrinsic immune responses, and promoted CD8⁺ T cell infiltration. Mechanistically, MYC inhibition increased CD8⁺ T cell-recruiting chemokines by inducing the DNA damage related cGAS-STING pathway. High expression of MYC combined with a low level of infiltrated CD8⁺ T cell in HNSCC correlated with poor prognosis. These results suggested the potential of small-molecule MYC inhibitors as anti-cancer therapeutic agents in HNSCC.

Lessons from Using Genetically Engineered Mouse Models of MYC-Induced Lymphoma

Oncogenic overexpression of MYC leads to the fatal deregulation of signaling pathways, cellular metabolism, and cell growth. MYC rearrangements are found frequently among non-Hodgkin B-cell lymphomas enforcing MYC overexpression. Genetically engineered mouse models (GEMMs) were developed to understand MYC-induced B-cell lymphomagenesis. Here, we highlight the advantages of using Eµ-Myc transgenic mice. We thoroughly compiled the available literature to discuss common challenges when using such mouse models. Furthermore, we give an overview of pathways affected by MYC based on knowledge gained from the use of GEMMs. We identified top regulators of MYC-induced lymphomagenesis, including some candidates that are not pharmacologically targeted yet.

To bind or not to bind: Cistromic reprogramming in prostate cancer

The term “cistrome” refers to the genome-wide location of regulatory elements associated with transcription factor binding-sites. The cistrome of key regulatory factors in prostate cancer etiology are substantially reprogrammed and altered during prostatic transformation and disease progression. For instance, the cistrome of the androgen receptor (AR), a ligand-inducible transcription factor central in normal prostate epithelium biology, is directly impacted and substantially reprogrammed during malignant transformation. Accumulating evidence demonstrates that additional transcription factors that are frequently mutated, or aberrantly expressed in prostate cancer, such as the pioneer transcription factors Forkhead Box A1 (FOXA1), the homeobox protein HOXB13, and the GATA binding protein 2 (GATA2), and the ETS-related gene (ERG), and the MYC proto-oncogene, contribute to the reprogramming of the AR cistrome. In addition, recent findings have highlighted key roles for the SWI/SNF complex and the chromatin-modifying helicase CHD1 in remodeling the epigenome and altering the AR cistrome during disease progression. In this review, we will cover the role of cistromic reprogramming in prostate cancer initiation and progression. Specifically, we will discuss the impact of key prostate cancer regulators, as well as the role of epigenetic and chromatin regulators in relation to the AR cistrome and the transformation of normal prostate epithelium. Given the importance of chromatin-transcription factor dynamics in normal cellular differentiation and cancer, an in-depth assessment of the factors involved in producing these altered cistromes is of great relevance and provides insight into new therapeutic strategies for prostate cancer.