MYC degradation

Targeting MYC: Multidimensional regulation and therapeutic strategies in oncology

MYC is dysregulated in approximately 70% of human cancers, strongly suggesting its essential function in cancer. MYC regulates many biological processes, such as cell cycle, metabolism, cellular senescence, apoptosis, angiogenesis, and immune escape. MYC plays a central role in carcinogenesis and is a key regulator of tumor development and drug resistance. Therefore, MYC is one of the most alluring therapeutic targets for developing cancer drugs. Although the search for direct inhibitors of MYC is challenging, MYC cannot simply be assumed to be undruggable. Targeting the MYC-MAX complex has been an effective method for directly targeting MYC. Alternatively, indirect targeting of MYC represents a more pragmatic therapeutic approach, mainly including inhibition of the transcriptional or translational processes of MYC, destabilization of the MYC protein, and blocking genes that are synthetically lethal with MYC overexpression. In this review, we delineate the multifaceted roles of MYC in cancer progression, highlighting a spectrum of therapeutic strategies and inhibitors for cancer therapy that target MYC, either directly or indirectly.

MYC amplification sensitizes TNBC to CHK1 inhibitors

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, for which effective therapy is urgently needed. We demonstrated that MYC overexpression was associated with TNBC subtype and promoted the cell proliferation, invasion and migration in TNBC cells. Moreover, MYC overexpression induced replication stress and DNA damage in TNBC cells. Our subsequent results revealed that the novel second-generation CHK1 inhibitor, prexasertib, exhibited a more pronounced inhibitory effect in MYC-overexpressed TNBC cells compared to other DNA damage repair inhibitors, including ATR, WEE1, and PARP inhibitors. Prexasertib induced synergistic lethality with MYC-overexpressed TNBC cells by generating excessive DNA damage. Intriguingly, RNA-seq analysis identified an increase in MYC levels and activation of MYC-related pathways following prexasertib treatment, while western blot results showed that prexasertib led to MYC protein degradation independent of proteasome pathway. In addition, MYC overexpression was associated with an immunosuppressive microenvironment and high PD-L1 expression. Prexasertib activated cGAS-STING pathway by inducing DNA damage. Therefore, combination of prexasertib and immune checkpoint inhibitors will be a potential therapeutic strategy for MYC-overexpressed TNBC. In conclusion, our findings demonstrated that MYC overexpression characterizes an aggressive TNBC subtype, enabling synergistic lethality with CHK1 inhibitors. CHK1 inhibitors will be a potential therapeutic strategy in TNBC patients with MYC overexpression.

From non-coding RNAs to cancer regulators: The fascinating world of micropeptides

Micropeptides are commonly identified as peptides encoded by non-coding RNAs (ncRNAs). In the short open reading frame (sORF) of ncRNAs, there is a base sequence encoding functional micropeptides, which is of great significance in the biological field. Recently, micropeptides regulate diverse processes, including mitochondrial metabolism, calcium transport, mRNA splicing, signal transduction, myocyte fusion, and cellular senescence, regulating the homeostasis of the internal environment and cancer's incidence and progression. Especially, the study of micropeptides in cancer about the potential regulatory mechanism will be conducive to further understanding of the process of cancer initiation and development. More and more research shows micropeptides have been confirmed to play an essential role in the emergence of multiple kinds of cancers, including Breast cancer, Colon cancer, Colorectal cancer, Glioma, Glioblastoma, and Liver cancer. This review presents a comprehensive synthesis of the latest advancements in our understanding of the biological roles of micropeptides in cancer cells, with a particular focus on the regulatory networks involving micropeptides in oncogenesis. The new mode of action of micropeptides provides innovative ideas for cancer diagnosis and treatment. Moreover, we explored the significant capacity of micropeptides as diagnostic biomarkers and targets for anti-cancer therapies in cancer clinical settings, highlighting their role in the development of innovative micropeptide-based diagnostic tools and anti-cancer therapeutics.

The ubiquitin ligase NKLAM promotes apoptosis and suppression of cell growth

Natural Killer Lytic Associated Molecule (NKLAM), also known as RNF19b, is a member of the RING-in between-RING-RING (RBR) E3 ubiquitin ligase family and plays a pivotal role in immune regulation. We identified a critical cysteine residue at position 301 essential for NKLAM's ubiquitin ligase function. Site-directed mutagenesis of this residue to serine or alanine abrogated the ligase activity of NKLAM. Utilizing inducible expression systems in two different cell lines, HEK293 embryonic kidney cells and K562 myeloid leukemia cells, we demonstrated that wild-type (WT) NKLAM, but not the catalytically inactive NKLAM alanine mutant (C301A), inhibited cellular proliferation, as evidenced by reduced cell numbers and decreased metabolic activity. Moreover, NKLAM expression led to a significant decrease in the abundance and stability of the proto-oncogene c-Myc, a key regulator of proliferation. NKLAM facilitated the proteasomal degradation of c-Myc, with a reduction in c-Myc half-life from 27 minutes to 12 minutes and restoration of c-Myc levels upon proteasome inhibition. Notably, prolonged NKLAM expression induced apoptosis, measured by annexin-V staining and caspase activation. Strikingly, the serine mutant, C301S, while lacking ubiquitin ligase activity, induced apoptosis comparable to WT NKLAM, highlighting an alternative pathway for NKLAM-mediated inhibition of cellular homeostasis. Our findings indicate that NKLAM is a cytolytic protein with multifaceted roles in cellular proliferation and apoptosis.

Squamocin Suppresses Tumor Growth through Triggering an Endoplasmic Reticulum Stress-Associated Degradation of EZH2/MYC Axis

Despite substantial advances in the antitumor effects of annonaceous acetogenins (ACGs), the absence of a defined biological action mechanism remains a major barrier to their clinical application. Here, it is found that squamocin effectively depletes both EZH2 and MYC in multiple cancer cell lines, including head and neck squamous cell carcinoma, and gastric and colorectal cancer, demonstrating potent efficacy in suppressing these in vivo tumor models. Through the combination of surface plasmon resonance (SPR), differential scanning fluorimetry (DSF), and cellular thermal shift assay (CETSA), heat shock protein 90α (HSP90α) is identified as the direct binding target of squamocin. Mechanistically, squamocin disrupts mitochondrial respiratory Complex I function, reduces ATP production, and impairs HSP90α function, provoking endoplasmic reticulum (ER) stress and the unfolded protein response (UPR). These intrinsic events within tumor cells enhance ER stress-associated ubiquitylation and degradation by triggering ubiquitin via the E1 activase UBA6, facilitating ubiquitin transferring to E2 conjugate UBE2Z and increasing the activities of E3 ligase FBXW7 to degrade both EZH2 and MYC. The findings elucidate the role of squamocin in the degradation of oncoproteins EZH2 and MYC by triggering an ER stress-associated UBA6-UBE2Z-FBXW7 ubiquitin cascade, providing insights that may accelerate therapeutic development targeting tumors driven by the EZH2/MYC axis.

Heterobifunctional proteomimetic polymers for targeted protein degradation

The burgeoning field of targeted protein degradation (TPD) has opened new avenues for modulating the activity of previously undruggable proteins of interest. To date, TPD has been dominated by small molecules containing separate linked domains for protein engagement and recruitment of cellular degradation machinery. The process of identifying active compounds has required tedious optimization and has been successful largely against a limited set of targets with well-defined, suitable docking pockets. Here we present a polymer chemistry approach termed the HYbrid DegRAding Copolymer (HYDRAC) to overcome standing challenges associated with the development of TPD. These copolymers densely display either peptide-based or small molecule-derived degradation inducers and target-binding peptide sequences for the selective degradation of disease-associated proteins. HYDRACs are synthesized in a facile manner, are modular in design, and are highly selective. Using the intrinsically disordered transcription factor MYC as an initial proof-of-concept, difficult to drug protein target, HYDRACs containing a MYC-inhibitory peptide copolymerized with a validated degron, showed robust and selective degradation of the target protein. Treatment of tumor-bearing mice with MYC-targeted HYDRACs showed decreased cell proliferation and increased tumor apoptosis, leading to significantly suppressed tumor growth in vivo . The versatility of the platform was demonstrated by substituting the degron for recruiters of three different E3 ligases (VHL, KEAP1, and CRBN), which all maintained MYC degradation. To demonstrate generalizability, HYDRACs were further designed against a second elusive target of clinical interest, KRAS, by employing a consensus RAS binding motif. RAS-targeted HYDRACs showed degradation in two cell lines harboring separate KRAS alleles, suggesting potential pan-KRAS activity. We envision the HYDRAC platform as a generalizable approach to developing degraders of proteins of interest, greatly expanding the therapeutic armamentarium for TPD.

PDCD11 Stabilizes C‐MYC Oncoprotein by Hindering C‐MYC‐SKP2 Negative Feedback Loop to Facilitate Progression of p53‐Mutant Breast and Colon Malignancies

C‐MYC is a proto‐oncoprotein whose dysregulation triggers tumorigenesis and tumor progression in ≈70% of cancer cases. It is presently demonstrated that aberrantly upregulated MYC is caused by the overexpressed and “extra‐nucleolar” PDCD11 in p53‐mutant breast and colon cancer cells, which is highly correlated to tumor progression, metastasis, and recurrence. In the nucleoplasm, PDCD11 binds to the TAD of C‐MYC to prevent SKP2, a transcriptional target of C‐MYC as well as one of the major E3 ligase components targeting C‐MYC, from interacting with and ubiquitinating C‐MYC in feedback. The ensuing stabilized C‐MYC activates downstream signaling to facilitate the cellular G1/S transition, proliferation, and migration. PDCD11 silencing restores SKP2‐mediated C‐MYC degradation, thereby remarkably suppressing tumor growth and metastasis in nude mice. These findings highlight PDCD11 as a novel C‐MYC partner and thereby offer a potential therapeutic rationale to challenge PDCD11‐mediated “pro‐stabilization” effect on C‐MYC, a widely considered “undruggable” target, to combat C‐MYC‐driven malignancies with p53 mutation.

Sialylated IgG-activated integrin β4-Src-Erk axis stabilizes c-Myc in a p300 lysine acetyltransferase-dependent manner to promote colorectal cancer liver metastasis

BACKGROUND

Liver metastasis is a leading cause of colorectal cancer mortality. Therefore, the underlying mechanism and potential therapeutic target of colorectal cancer liver metastasis urge to be found. Mounting evidence indicates that cancer-derived sialylated IgG promotes tumor formation and progression. However, the role of sialylated IgG in colorectal cancer liver metastasis remains undefined.

MATERIALS AND METHODS

Analysis of sialylated IgG in paired tumor tissues and adjacent normal tissues from 65 colorectal cancer patients was performed using immunohistochemical staining. Functional assays of sialylated IgG were explored in vitro and in vivo. The downstream target of sialylated IgG was investigated by performing gene-set enrichment analysis, ubiquitination assay, cycloheximide chase assay, acetylation assay and co-immunoprecipitation.

RESULTS

Here, our investigation reveals that sialylated IgG is significantly upregulated in colorectal cancer and that the increase of IgG is positively associated with liver metastasis and poor overall survival in colorectal cancer patients. Sialylated IgG promotes colorectal cancer cell migration, invasion and liver metastasis. Notably, anti-sialylated IgG antibody effectively blocks colorectal cancer liver metastasis in mouse models. Mechanistically, sialylated IgG upregulates c-Myc protein level by decreasing c-Myc ubiquitination. Moreover, we find that p300/CBP can stabilize c-Myc by reducing c-Myc ubiquitination. Overexpression of p300/CBP protects c-Myc protein level from sialylated IgG-knockdown in a lysine acetyltransferase activity-dependent manner. Furthermore, sialylated IgG upregulates p300 protein level through integrin β4-FAK-Src-Erk signaling.

CONCLUSION

Collectively, these results indicate that a novel sialylated IgG-integrin β4-FAK-Src-Erk-p300-c-Myc signaling pathway promotes colorectal cancer liver metastasis, thus providing potential therapeutic targets for colorectal cancer liver metastasis.

E2F1 activates USP19 to affect the stability of c-Myc to facilitate the progression of hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the most common malignant tumor worldwide with a high mortality rate. Herein, this study aims to explore the molecular mechanisms of E2F transcription factor 1 (E2F1), ubiquitin specific peptidase 19 (USP19) and c-Myc in regulating HCC progression.

METHODS

RT-qPCR and western blotting were utilized to assess mRNA and protein expression, respectively. The behavior of cells was examined through Methylthiazolyldiphenyl-tetrazolium bromide (MTT), flow cytometry, transwell, and cell sphere formation assays. Glycolysis-related indicators were detected by kits. The interaction between USP19 and c-Myc was measured by co-immunoprecipitation (Co-IP). Dual-luciferase reporter assay and Chromatin Immunoprecipitation (ChIP) assays were used to assess the binding of E2F1 and USP19 promoter. A mouse xenograft model was established for the purpose of analysis in vivo.

RESULTS

High level of c-Myc was observed in HCC tissues and cells. Silencing c-Myc results in the suppression of cell migration, invasion, proliferation, and glycolysis or promotion of apoptosis. USP19 directly bound to c-Myc, and maintained its stability by removing ubiquitination on c-Myc. Overexpression of c-Myc in HCC cells rescued the anti-tumor effect of USP19 deletion. E2F1 promoted USP19 transcription, and increased USP19 expression counteracts the effects of E2F1 depletion on cell behaviors. In vivo, USP19 knockdown controlled HCC growth by modulating c-Myc.

CONCLUSION

E2F1 activated USP19 transcription, thereby stabilizing c-Myc via deubiquitination and accelerating HCC progression.

Cryo-EM structures reveal the PP2A-B55α and Eya3 interaction that can be disrupted by a peptide inhibitor

We have previously shown that Eya3 recruits PP2A-B55α to dephosphorylate pT58 on Myc, increasing Myc stability and enhancing primary tumor growth of triple-negative breast cancer (TNBC). However, the molecular details of how Eya3 recruits PP2A-B55α remain unclear. Here we determined the cryo-EM structures of PP2A-B55α bound with Eya3, with an inhibitory peptide B55i, and in its unbound state. These studies demonstrate that Eya3 binds B55α through an extended peptide in the NTD of Eya3. The Eya3 peptide and other PP2A-B55α substrates and protein/peptide inhibitors including B55i bind to a similar area on the B55α surface but the molecular details of the binding differ. We further demonstrated that the B55i peptide inhibits the B55α and Eya3 interaction in vitro. B55i peptide expressed on a plasmid increases pT58 and decreases Myc protein level in TNBC cells, suggesting the potential of B55i or similar peptides as therapies for TNBC.

DLGAP5 enhances bladder cancer chemoresistance by regulating glycolysis through MYC stabilization

Rationale: Bladder cancer (BLCA), one of the most lethal urological tumors, exhibits high rates of recurrence and chemoresistance, particularly to gemcitabine (GEM). Understanding the mechanisms of GEM resistance is crucial for improving therapeutic outcomes. Our study investigates the role of DLGAP5 in promoting GEM resistance through modulation of glycolysis and MYC protein stability in BLCA cells. Methods: We utilized various BLCA cell lines and clinical tissue samples to analyze the impact of DLGAP5 on GEM resistance. Through biochemical assays, protein interaction studies, and gene expression analyses, we examined how DLGAP5 interacts with USP11 and MYC, assessed the effects on MYC deubiquitination and stability. The influence of these interactions on glycolytic activity and GEM resistance was also evaluated via mouse subcutaneous xenograft model and spontaneous BLCA model. Results: Our findings indicate that DLGAP5 enhances GEM resistance by stabilizing MYC protein via deubiquitination, a process mediated by USP11. DLGAP5 was found to facilitate the interaction between USP11 and MYC, promoting MYC-driven transcription of DLGAP5 itself, thereby creating a positive feedback loop. This loop leads to sustained MYC accumulation and increased glycolytic activity, contributing to GEM resistance in BLCA cells. Conclusion: The study highlights the critical role of DLGAP5 in regulating MYC protein stability and suggests that disrupting the DLGAP5-USP11-MYC axis may provide a novel therapeutic approach to overcome GEM resistance in BLCA. DLGAP5 represents a potential target for therapeutic intervention aimed at mitigating chemoresistance in bladder cancer BLCA.

Dynamic Multilevel Regulation of EGFR, KRAS, and MYC Oncogenes: Driving Cancer Cell Proliferation Through (Epi)Genetic and Post-Transcriptional/Translational Pathways

The epidermal growth factor receptor (EGFR) regulates gene expression through two primary mechanisms: as a growth factor in the nucleus, where it translocates upon binding its ligand, or via its intrinsic tyrosine kinase activity in the cytosol, where it modulates key signaling pathways such as RAS/MYC, PI3K, PLCγ, and STAT3. During tumorigenesis, these pathways become deregulated, leading to uncontrolled proliferation, enhanced migratory and metastatic capabilities, evasion of programmed cell death, and resistance to chemotherapy or radiotherapy. The RAS and MYC oncogenes are pivotal in tumorigenesis, driving processes such as resistance to apoptosis, replicative immortality, cellular invasion and metastasis, and metabolic reprogramming. These oncogenes are subject to regulation by a range of epigenetic and post-transcriptional modifications. This review focuses on the deregulation of EGFR, RAS, and MYC expression caused by (epi)genetic alterations and post-translational modifications. It also explores the therapeutic potential of targeting these regulatory proteins, emphasizing the importance of phenotyping neoplastic tissues to inform the treatment of cancer.

Rocaglamide reprograms glucose metabolism in erythroleukemic cells via c-MYC transcriptional regulation of TXNIP and HK2

ETHNOPHARMACOLOGICAL RELEVANCE

The theory of traditional Chinese medicine (TCM) views leukemia as an imbalance between cell growth and death mainly caused by blood stasis. Medicinal plants Aglaia Lour. (family Meliaceae) are traditionally used as folk medicine in China. It possesses the effects of removing blood stasis and swelling for treatment of cancer. Rocaglamide (RocA) is the main active phytochemical component of the genus Aglaia Lour. Possessing highly anti-leukemia properties. However, the molecular mechanisms by which RocA exerts its anti-growth effect on erythroleukemia cells are largely unknown.

AIM OF THE STUDY

This study aimed to explore the underlying mechanism and glucose metabolism regulation effects of RocA responsible for its anti-erythroleukemia activity.

MATERIALS AND METHODS

Human erythroleukemic cells were tested for glucose metabolism and treated with glucose deprivation and RocA. MTT assay, cell cycle and apoptosis were used to elucidate growth inhibition. Glucose uptake, glucose consumption and lactate production were evaluated for identification of glucose metabolism. Luciferase assay and ChIP were used to examine the transcriptional activity of c-MYC on the conserved E-boxes binding of the TXNIP (thioredoxin-interacting protein) and HK2 (hexokinase 2) genes. siRNA, shRNA and exogenous transfection were employed to elucidate the effects of TXNIP and HK2 on glucose metabolism.

RESULTS

We find that glucose deprivation results in growth inhibition, cell cycle arrest and extensive apoptosis in erythroleukemic cells accompanied by downregulation of c-MYC and HK2, responsible for glucose metabolism. The similar results emerged in RocA treated erythroleukemic cells in presence of glucose. RocA is shown to decrease glucose uptake, glucose consumption and lactate production. Mechanistically, RocA dramatically increases TXNIP expression through interference with c-MYC binding to the promoter of the TXNIP gene. RocA also represses c-MYC transcriptional recognition of conserved E-boxes in the HK2 first intron, resulting in HK2 loss. These results implicate c-MYC as an important regulator of TXNIP and HK2 after RocA treatment. TXNIP overexpression or knockdown of HK2 suppresses the proliferation of erythroleukemic cells. Ectopic TXNIP expression restricts glucose uptake and HK2 suppression decreases glucose utilization. Further, our data suggests that loss of HK2 weakens the RocA-driven inhibition effects. We propose repression of c-MYC or the binding by RocA upregulates TXNIP and downregulates HK2, possibly contributes to growth inhibition in human erythroleukemic cells.

CONCLUSIONS

This study uncovers molecular mechanism of RocA against leukemic cells proliferation, linking the anti-erythroleukemia properties of RocA to glucose metabolism.

Reversible downregulation of MYC in a spheroid model of metastatic epithelial ovarian cancer

Upon detachment from the primary tumour, epithelial ovarian cancer cells can form multicellular aggregates, also referred to as spheroids, that have the capacity to establish metastases at distant sites. These structures exhibit numerous adaptations that may facilitate metastatic transit and promote tumorigenic potential. One such adaptation is the acquisition of dormancy, characterized by decreased proliferation and molecular features of quiescence. One of the most frequently dysregulated genes in cancer is MYC, which encodes a transcription factor that promotes cell proliferation. In this study, we demonstrate that MYC protein abundance and associated gene expression is significantly decreased in EOC spheroids compared to adherent cells. This downregulation occurs rapidly upon cell detachment and is proteasome-dependent. Moreover, MYC protein abundance and associated gene expression is restored upon spheroid reattachment to an adherent culture surface. Overall, our findings suggest that suppression of MYC activity is a common feature of EOC spheroids and may contribute to the reversible acquisition of dormancy.

FAM49B drives colorectal cancer progression by stabilizing c-Myc through NEK9 phosphorylation

Colorectal cancer (CRC) ranks as the third most prevalent cancer globally and is the second leading cause of cancer mortality. FAM49B, a member of the FAM49 gene family, is a recently identified, evolutionarily conserved gene. Emerging studies indicate that FAM49B plays a role in various cancers, though its specific mechanism in CRC remains largely unexplored. In this study, we observed that FAM49B was abnormally expressed in CRC tissues and cell lines, with elevated expression correlating with poor patient prognosis. FAM49B knockdown markedly suppressed CRC cell proliferation by arresting the cell cycle and reducing cell migration and invasion. Single-cell RNA-seq (ScRNA-seq) analysis revealed that high FAM49B expression in malignant epithelial cell clusters was strongly linked to c-Myc oncogene activation. Further, FAM49B knockdown significantly reduced c-Myc expression by enhancing its K48 ubiquitination. We identified NEK9 as a direct interacting partner of FAM49B, with FAM49B knockdown inhibiting NEK9-Thr210 phosphorylation. Similarly, high NEK9 expression was linked to unfavorable prognosis in CRC. In FAM49B-overexpressing CRC cells, NEK9 knockdown significantly suppressed c-Myc expression, c-Myc-ser62 phosphorylation, and reduced cell proliferation, migration, and invasion. Thus, directly targeting the FAM49B/NEK9/c-Myc pathway presents a promising therapeutic approach for c-Myc positive CRC patients.

Transposable element exonization generates a reservoir of evolving and functional protein isoforms

Alternative splicing enhances protein diversity in different ways, including through exonization of transposable elements (TEs). Recent transcriptomic analyses identified thousands of unannotated spliced transcripts with exonizing TEs, but their contribution to the proteome and biological relevance remains unclear. Here, we use transcriptome assembly, ribosome profiling, and proteomics to describe a population of 1,227 unannotated TE exonizing isoforms generated by mRNA splicing and recurrent in human populations. Despite being shorter and lowly expressed, these isoforms are shared between individuals and efficiently translated. Functional analyses show stable expression, specific cellular localization, and, in some cases, modified functions. Exonized TEs are rich in ancient genes, whereas the involved splice sites are recent and can be evolutionarily conserved. In addition, exonized TEs contribute to the secondary structure of the emerging isoforms, supporting their functional relevance. We conclude that TE-spliced isoforms represent a diversity reservoir of functional proteins on which natural selection can act.

The Functional Interaction Between Epstein-Barr Virus and MYC in the Pathogenesis of Burkitt Lymphoma

The Epstein-Barr virus (EBV) is associated with a wide range of diseases, malignant and non-malignant. EBV was, in fact, the first virus described with cell transformation capacity, discovered by Epstein in 1964 in lymphoma samples from African children. Since then, EBV has been associated with several human tumors including nasopharyngeal carcinoma, gastric carcinoma, T-cell lymphoma, Hodgkin lymphoma, diffuse large B cell lymphoma, and Burkitt lymphoma among others. The molecular hallmark of Burkitt lymphoma (BL) is a chromosomal translocation that involves the MYC gene and immunoglobulin loci, resulting in the deregulated expression of MYC, an oncogenic transcription factor that appears deregulated in about half of human tumors. The role of MYC in lymphoma is well established, as MYC overexpression drives B cell proliferation through multiple mechanisms, foremost, the stimulation of the cell cycle. Indeed, MYC is found overexpressed or deregulated in several non-Hodgkin lymphomas. Most endemic and many sporadic BLs are associated with EBV infection. While some mechanisms by which EBV can contribute to BL have been reported, the mechanism that links MYC translocation and EBV infection in BL is still under debate. Here, we review the main EBV-associated diseases, with a special focus on BL, and we discuss the interaction of EBV and MYC translocation during B cell malignant transformation in BL.

Anticancer potential of active alkaloids and synthetic analogs derived from marine invertebrates

In recent years, the number of cancers has soared, becoming one of the leading causes of human death. At the same time, marine anticancer substances have been the focus of marine drug research. Marine alkaloids derived from marine invertebrates like sponges are an important class of secondary metabolites, which have good bioactivities of blocking the cancer cell cycle, inducing autophagy and apoptosis of cancer cells, inhibiting cancer cell invasion and proliferation. They show potential as anticancer drug candidates. Therefore, in this review, we focus on the detailed introduction of bioactive alkaloids and their synthetic analogs from marine invertebrates, such as 4-chloro fascapysin and other 41 kinds of marine alkaloids or marine alkaloid synthetic analogs. They have significant anticancer activities on breast cancer, cervical cancer, colorectal cancer, prostate cancer, lung cancer, liver cancer, and so on. It provides new candidate compounds for anticancer drug research and provides a reference basis for marine drug resources research.

TRIM40 interacts with ROCK1 directly and inhibits colorectal cancer cell proliferation through the c-Myc/p21 axis

BACKGROUND

Colorectal cancer (CRC) is the most common malignancy of the digestive tract, and to date, morbidity and mortality rates remain high. While existing therapeutic methods have achieved certain effective outcomes, there are still many problems in treating this disease. Therefore, it is still urgent to constantly find new therapeutic targets in CRC that could lead to new therapeutics.

METHODS

Immunohistochemistry, Real-time PCR and Western Blot were employed to measure mRNA and protein levels of the target protein, respectively. The proliferation ability of CRC cells was evaluated using ATP assay, Soft agar assay, and nude mouse subcutaneous tumorigenesis assay. Protein Degradation Assay was conducted to determine protein degradation rate, while Ubiquitination assay was used to assess the ubiquitination modification level of target proteins. Immunoprecipitation assay was used to study protein interactions, and pull-down assay was employed to investigate direct interactions between proteins.

RESULTS

TRIM40 was significantly down-regulated in CRC tissues, with its expression levels positively correlating with disease prognosis. Using both in vitro and in vivo approaches, it was demonstrated that TRIM40 could significantly inhibit the proliferation of CRC cells. Molecular mechanism studies showed that TRIM40 directly binds to and ubiquitinates ROCK1 protein, accelerating its degradation and subsequently reducing the stability of c-Myc protein. This cascade of events results in the release of transcriptional inhibition of p21 by c-Myc, leading to increased p21 expression and G0/G1 phase arrest in CRC cells.

CONCLUSION

This research suggests that TRIM40 could be a valuable therapeutic target for the treatment of CRC.

Acidity suppresses CD8 + T-cell function by perturbing IL-2, mTORC1, and c-Myc signaling

CD8 + T cells have critical roles in tumor control, but a range of factors in their microenvironment such as low pH can suppress their function. Here, we demonstrate that acidity restricts T-cell expansion mainly through impairing IL-2 responsiveness, lowers cytokine secretion upon re-activation, and reduces the cytolytic capacity of CD8 + T cells expressing low-affinity TCR. We further find decreased mTORC1 signaling activity and c-Myc levels at low pH. Mechanistically, nuclear/cytoplasmic acidification is linked to mTORC1 suppression in a Rheb-, Akt/TSC2/PRAS40-, GATOR1- and Lkb1/AMPK-independent manner, while c-Myc levels drop due to both decreased transcription and higher levels of proteasome-mediated degradation. In addition, lower intracellular levels of glutamine, glutamate, and aspartate, as well as elevated proline levels are observed with no apparent impact on mTORC1 signaling or c-Myc levels. Overall, we suggest that, due to the broad impact of acidity on CD8 + T cells, multiple interventions will be required to restore T-cell function unless intracellular pH is effectively controlled.

The FGF/FGFR/c-Myc axis as a promising therapeutic target in multiple myeloma

Among blood cancers, multiple myeloma (MM) represents the second most common neoplasm and is characterized by the accumulation and proliferation of monoclonal plasma cells within the bone marrow. Despite the last few decades being characterized by the development of different therapeutic strategies against MM, at present such disease is still considered incurable. Although MM is highly heterogeneous in terms of genetic and molecular subtypes, about 67% of MM cases are associated with abnormal activity of the transcription factor c-Myc, which has so far revealed a protein extremely difficult to target. We have recently demonstrated that activation of fibroblast growth factor (FGF) signaling protects MM cells from oxidative stress-induced apoptosis by stabilizing the oncoprotein c-Myc. Accordingly, secretion of FGF ligands and autocrine activation of FGF receptors (FGFR) is observed in MM cells and FGFR3 genomic alterations represent some 15-20% MM cases and are associated with poor outcome. Thus, FGF/FGFR blockade may represent a promising strategy to indirectly target c-Myc in MM. On this basis, the present review aims at providing an overview of recently explored connections between the FGF/FGFR system and c-Myc oncoprotein, sustaining the therapeutic potential of targeting the FGF/FGFR/c-Myc axis in MM by using inhibitors targeting FGF ligands or FGF receptors. Importantly, the provided findings may represent the rationale for using FDA approved FGFR TK inhibitors (i.e. Pemigatinib, Futibatinib, Erdafitinib) for the treatment of MM patients presenting with an aberrant activation of this axis.

ADAMTS4 exacerbates lung cancer progression via regulating c-Myc protein stability and activating MAPK signaling pathway

BACKGROUND

Lung cancer is one of the most frequent cancers and the leading cause of cancer-related deaths worldwide with poor prognosis. A disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4) is crucial in the regulation of the extracellular matrix (ECM), impacting its formation, homeostasis and remodeling, and has been linked to cancer progression. However, the specific involvement of ADAMTS4 in the development of lung cancer remains unclear.

METHODS

ADAMTS4 expression was identified in human lung cancer samples by immunohistochemical (IHC) staining and the correlation of ADAMTS4 with clinical outcome was determined. The functional impact of ADAMTS4 on malignant phenotypes of lung cancer cells was explored both in vitro and in vivo. The mechanisms underlying ADAMTS4-mediated lung cancer progression were explored by ubiquitination-related assays.

RESULTS

Our study revealed a significant upregulation of ADAMTS4 at the protein level in lung cancer tissues compared to para-carcinoma normal tissues. High ADAMTS4 expression inversely correlated with the prognosis of lung cancer patients. Knockdown of ADAMTS4 inhibited the proliferation and migration of lung cancer cells, as well as the tubule formation of HUVECs, while ADAMTS4 overexpression exerted opposite effects. Mechanistically, we found that ADAMTS4 stabilized c-Myc by inhibiting its ubiquitination, thereby promoting the in vitro and in vivo growth of lung cancer cells and inducing HUVECs tubule formation in lung cancer. In addition, our results suggested that ADAMTS4 overexpression activated MAPK signaling pathway.

CONCLUSIONS

We highlighted the promoting role of ADAMTS4 in lung cancer progression and proposed ADAMTS4 as a promising therapeutic target for lung cancer patients.

Growth Signaling Networks Orchestrate Cancer Metabolic Networks

Normal cells grow and divide only when instructed to by signaling pathways stimulated by exogenous growth factors. A nearly ubiquitous feature of cancer cells is their capacity to grow independent of such signals, in an uncontrolled, cell-intrinsic manner. This property arises due to the frequent oncogenic activation of core growth factor signaling pathway components, including receptor tyrosine kinases, PI3K-AKT, RAS-RAF, mTORC1, and MYC, leading to the aberrant propagation of pro-growth signals independent of exogenous growth factors. The growth of both normal and cancer cells requires the acquisition of nutrients and their anabolic conversion to the primary macromolecules underlying biomass production (protein, nucleic acids, and lipids). The core growth factor signaling pathways exert tight regulation of these metabolic processes and the oncogenic activation of these pathways drive the key metabolic properties of cancer cells and tumors. Here, we review the molecular mechanisms through which these growth signaling pathways control and coordinate cancer metabolism.

Aurora B facilitates cholangiocarcinoma progression by stabilizing c-Myc

BACKGROUND

Cholangiocarcinoma (CCA), a malignancy that arises from biliary epithelial cells, has a dismal prognosis, and few targeted therapies are available. Aurora B, a key mitotic regulator, has been reported to be involved in the progression of various tumors, yet its role in CCA is still unclarified.

METHODS

Human CCA tissues and murine spontaneous CCA models were used to assess Aurora B expression in CCA. A loss-of-function model was constructed in CCA cells to determine the role of Aurora B in CCA progression. Subcutaneous and liver orthotopic xenograft models were used to assess the therapeutic potential of Aurora B inhibitors in CCA.

RESULTS

In murine spontaneous CCA models, Aurora B was significantly upregulated. Elevated Aurora B expression was also observed in 62.3% of human specimens in our validation cohort (143 CCA specimens), and high Aurora B expression was positively correlated with pathological parameters of tumors and poor survival. Knockdown of Aurora B by siRNA and heteroduplex oligonucleotide (HDO) or an Aurora B kinase inhibitor (AZD1152) significantly suppressed CCA progression via G2/M arrest induction. An interaction between Aurora B and c-Myc was found in CCA cells. Targeting Aurora B significantly reduced this interaction and accelerated the proteasomal degradation of c-Myc, suggesting that Aurora B promoted the malignant properties of CCA by stabilizing c-Myc. Furthermore, sequential application of AZD1152 or Aurora B HDO drastically improved the efficacy of gemcitabine in CCA.

CONCLUSIONS

Aurora B plays an essential role in CCA progression by modulating c-Myc stability and represents a new target for treatment and chemosensitization in CCA.

CLK3 promotes tumor proliferation by activating MYC signaling

Colorectal cancer (CRC) ranks among the leading causes of cancer-related mortality worldwide, posing a significant public health challenge. Despite advancements in treatment strategies, prognosis for advanced CRC remains poor. Here, we investigate the role of CLK3 and its interaction with the c-Myc signaling pathway in CRC progression. Our study reveals significant overexpression of CLK3 in CRC tumor tissues, correlating with disease advancement, and demonstrates that CLK3 promotes CRC cell proliferation, mediated by its activation of MYC signaling through upregulation of c-MYC expression. In vivo experiments confirm the oncogenic role of CLK3, with its loss resulting in decreased tumor growth and c-MYC expression. These findings highlight CLK3 as a potential therapeutic target in CRC, offering insights into novel treatment strategies.

ARMCX1 inhibits lung adenocarcinoma progression by recruiting FBXW7 for c-Myc degradation

BACKGROUND

Armadillo Repeat Containing X-Linked 1 (ARMCX1), a member of the ARM Repeat X-linked protein family, exerts inhibitory function in various tumors. However, its biological role in lung adenocarcinoma (LUAD) and the underlying molecular mechanisms require further exploration.

METHODS

LUAD tissue microarrays and bioinformatic databases were used to evaluate the relationship between ARMCX1 and clinicopathological features. The influence of ARMCX1 on LUAD cell proliferation, migration, and invasion in vitro was determined by colony formation, CCK-8, EdU incorporation, cell cycle, wound healing, and Transwell assays. The impact of ARMCX1 on LUAD cell growth and metastasis in vivo was determined by subcutaneously transplanted tumor and pulmonary metastasis assays. Western blot, immunoprecipitation, immunofluorescence, cycloheximide, and proteasome inhibitor assays were finally conducted to explore the potential underlying molecular mechanisms.

RESULTS

ARMCX1 expression was downregulated in clinical LUAD samples due to which patient prognoses were poor. Functional experiments indicated that ARMCX1 overexpression inhibited the growth and metastasis of LUAD cells in vitro and in vivo. The molecular mechanism suggested that ARMCX1 recruits the E3 ubiquitin ligase FBXW7 for mediating ubiquitinated degradation of c-Myc, suppressing its nuclear accumulation, and ultimately inactivating cell cycle and epithelial-mesenchymal transition (EMT) signals.

CONCLUSION

ARMCX1 inhibits LUAD cell proliferation and metastasis by interacting with c-Myc and enhancing its ubiquitination and degradation. Consequently, it can act as a tumor suppressor in this disease. These results suggest that ARMCX1 is a potential target in the treatment of LUAD.

The OGT-c-Myc-PDK2 axis rewires the TCA cycle and promotes colorectal tumor growth

Deregulated glucose metabolism termed the "Warburg effect" is a fundamental feature of cancers, including the colorectal cancer. This is typically characterized with an increased rate of glycolysis, and a concomitant reduced rate of the tricarboxylic acid (TCA) cycle metabolism as compared to the normal cells. How the TCA cycle is manipulated in cancer cells remains unknown. Here, we show that O-linked N-acetylglucosamine (O-GlcNAc) regulates the TCA cycle in colorectal cancer cells. Depletion of OGT, the sole transferase of O-GlcNAc, significantly increases the TCA cycle metabolism in colorectal cancer cells. Mechanistically, OGT-catalyzed O-GlcNAc modification of c-Myc at serine 415 (S415) increases c-Myc stability, which transcriptionally upregulates the expression of pyruvate dehydrogenase kinase 2 (PDK2). PDK2 phosphorylates pyruvate dehydrogenase (PDH) to inhibit the activity of mitochondrial pyruvate dehydrogenase complex, which reduces mitochondrial pyruvate metabolism, suppresses reactive oxygen species production, and promotes xenograft tumor growth. Furthermore, c-Myc S415 glycosylation levels positively correlate with PDK2 expression levels in clinical colorectal tumor tissues. This study highlights the OGT-c-Myc-PDK2 axis as a key mechanism linking oncoprotein activation with deregulated glucose metabolism in colorectal cancer.

Regulation of MYC by CARD14 in human epithelium is a determinant of epidermal homeostasis and disease

Caspase recruitment domain family member 14 (CARD14) and its variants are associated with both atopic dermatitis (AD) and psoriasis, but their mechanistic impact on skin barrier homeostasis is largely unknown. CARD14 is known to signal via NF-κB; however, CARD14-NF-κB signaling does not fully explain the heterogeneity of CARD14-driven disease. Here, we describe a direct interaction between CARD14 and MYC and show that CARD14 signals through MYC in keratinocytes to coordinate skin barrier homeostasis. CARD14 directly binds MYC and influences barrier formation in an MYC-dependent fashion, and this mechanism is undermined by disease-associated CARD14 variants. These studies establish a paradigm that CARD14 activation regulates skin barrier function by two distinct mechanisms, including activating NF-κB to bolster the antimicrobial (chemical) barrier and stimulating MYC to bolster the physical barrier. Finally, we show that CARD14-dependent MYC signaling occurs in other epithelia, expanding the impact of our findings beyond the skin.

ZNF300 promotes proliferation and migration of hepatocellular carcinoma by upregulating c-MYC gene expression

BACKGROUND

Hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the liver. Currently, the treatments of HCC are limited to surgical resection and liver transplantation, and there is no effective systemic therapy.

OBJECTIVES

To investigate the regulatory mechanism of zinc finger protein 300 (ZNF300) in hepatocellular carcinoma (HCC).

METHODS

The expressions of ZNF300 in HCC tissue samples and HCC cell lines (Hep3B, Huh7, SNU-387) were detected. ZNF300 overexpression vector (ZNF300) or shRNAZNF300 (shZNF300) was transfected into HCC cells to increase or inhibit ZNF300 expression. 5-Ethynyl-2'-deoxyuridine assay (EdU), cell counting kit-8 assay (CCK-8) and transwell invasion assay were conducted to evaluate the proliferation, viability, migration, and invasion of HCC cells respectively. The expressions of tumor migration and invasion related proteins (matrix metallopeptidase 2 (MMP-2) and MMP-9), c-MYC, and MAPK/ERK signaling pathway related molecules (p-ERK1/2, ERK1/2, p-P38, P38) were determined by western blotting. Hep3B cells transfected with shZNF300 were subcutaneously injected into nude mice to perform tumor xenograft experiment. Tumor volume and weight were measured.

RESULTS

ZNF300 was upregulated in HCC tissues and cells. The expressions of MMP-2 and MMP-9 were increased in HCC cells after transfecting with ZNF300 but reduced in HCC cells transfected with shZNF300. Downregulation of ZNF300 inhibited HCC cell proliferation, migration, and invasion, while overexpression of ZNF300 showed the opposite effects. Moreover, the expressions of c-MYC and MAPK/ERK signaling pathway related molecules were increased after overexpression of ZNF300 but reduced after downregulating ZNF300. In tumor xenograft experiment, downregulation of ZNF300 reduced tumor volume and weight.

CONCLUSION

The present study proved that downregulation of ZNF300 inhibited HCC growth by reducing c-MYC expression and MAPK/ERK signaling pathway.

CDC7 inhibition impairs neuroendocrine transformation in lung and prostate tumors through MYC degradation

Neuroendocrine (NE) transformation is a mechanism of resistance to targeted therapy in lung and prostate adenocarcinomas leading to poor prognosis. Up to date, even if patients at high risk of transformation can be identified by the occurrence of Tumor Protein P53 (TP53) and Retinoblastoma Transcriptional Corepressor 1 (RB1) mutations in their tumors, no therapeutic strategies are available to prevent or delay histological transformation. Upregulation of the cell cycle kinase Cell Division Cycle 7 (CDC7) occurred in tumors during the initial steps of NE transformation, already after TP53/RB1 co-inactivation, leading to induced sensitivity to the CDC7 inhibitor simurosertib. CDC7 inhibition suppressed NE transdifferentiation and extended response to targeted therapy in in vivo models of NE transformation by inducing the proteasome-mediated degradation of the MYC Proto-Oncogen (MYC), implicated in stemness and histological transformation. Ectopic overexpression of a degradation-resistant MYC isoform reestablished the NE transformation phenotype observed on targeted therapy, even in the presence of simurosertib. CDC7 inhibition also markedly extended response to standard cytotoxics (cisplatin, irinotecan) in lung and prostate small cell carcinoma models. These results nominate CDC7 inhibition as a therapeutic strategy to constrain lineage plasticity, as well as to effectively treat NE tumors de novo or after transformation. As simurosertib clinical efficacy trials are ongoing, this concept could be readily translated for patients at risk of transformation.

The roles of FGFR3 and c-MYC in urothelial bladder cancer

Bladder cancer is one of the most frequently occurring cancers worldwide. At diagnosis, 75% of urothelial bladder cancer cases have non-muscle invasive bladder cancer while 25% have muscle invasive or metastatic disease. Aberrantly activated fibroblast growth factor receptor (FGFR)-3 has been implicated in the pathogenesis of bladder cancer. Activating mutations of FGFR3 are observed in around 70% of NMIBC cases and ~ 15% of MIBCs. Activated FGFR3 leads to ligand-independent receptor dimerization and activation of downstream signaling pathways that promote cell proliferation and survival. FGFR3 is an important therapeutic target in bladder cancer, and clinical studies have shown the benefit of FGFR inhibitors in a subset of bladder cancer patients. c-MYC is a well-known major driver of carcinogenesis and is one of the most commonly deregulated oncogenes identified in human cancers. Studies have shown that the antitumor effects of FGFR inhibition in FGFR3 dependent bladder cancer cells and other FGFR dependent cancers may be mediated through c-MYC, a key downstream effector of activated FGFR that is involved tumorigenesis. This review will summarize the current general understanding of FGFR signaling and MYC alterations in cancer, and the role of FGFR3 and MYC dysregulation in the pathogenesis of urothelial bladder cancer with the possible therapeutic implications.

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.

The ubiquitin-like protein UBTD1 promotes colorectal cancer progression by stabilizing c-Myc to upregulate glycolysis

Dysfunction of the ubiquitin-proteasome system (UPS) is involved in the pathogenesis of various malignancies including colorectal cancer (CRC). Ubiquitin domain containing 1 (UBTD1), a ubiquitin-like protein, regulates UPS-mediated protein degradation and tumor progression in some cancer types. However, the biological function and mechanism of UBTD1 are far from being well elucidated, and its role in CRC has not been explored yet. In our study, we analyzed CRC patients' clinical information and UBTD1 expression data, and found that the expression of UBTD1 in cancer tissue was significantly higher than that in adjacent normal tissue. Higher UBTD1 expression was significantly associated with poorer survival and more lymph node metastasis. Overexpression of UBTD1 could facilitate, while knockdown could inhibit CRC cell proliferation and migration, respectively. RNA-seq and proteomics indicated that c-Myc is an important downstream target of UBTD1. Metabolomics showed the products of the glycolysis pathway were significantly increased in UBTD1 overexpression cells. In vitro, we verified UBTD1 upregulating c-Myc protein and promoting CRC cell proliferation and migration via regulating c-Myc. UBTD1 promoted CRC cells' glycolysis, evidenced by the increased lactate production and glucose uptake following UBTD1 overexpression. Mechanistically, UBTD1 prolonged the half-life of the c-Myc protein by binding to E3 ligase β-transducin repeat-containing protein (β-TrCP), thereby upregulated the expression of glycolysis rate-limiting enzyme hexokinase II (HK2), and enhanced glycolysis and promoted CRC progression. In conclusion, our study revealed that UBTD1 promotes CRC progression by upregulating glycolysis via the β-TrCP/c-Myc/HK2 pathway, suggesting its potential as a prognostic biomarker and therapeutic target in CRC.

A positive feedback loop between PFKP and c-Myc drives head and neck squamous cell carcinoma progression

BACKGROUND

The aberrant expression of phosphofructokinase-platelet (PFKP) plays a crucial role in the development of various human cancers by modifying diverse biological functions. However, the precise molecular mechanisms underlying the role of PFKP in head and neck squamous cell carcinoma (HNSCC) are not fully elucidated.

METHODS

We assessed the expression levels of PFKP and c-Myc in tumor and adjacent normal tissues from 120 HNSCC patients. A series of in vitro and in vivo experiments were performed to explore the impact of the feedback loop between PFKP and c-Myc on HNSCC progression. Additionally, we explored the therapeutic effects of targeting PFKP and c-Myc in HNSCC using Patient-Derived Organoids (PDO), Cell Line-Derived Xenografts, and Patients-Derived Xenografts.

RESULTS

Our findings indicated that PFKP is frequently upregulated in HNSCC tissues and cell lines, correlating with poor prognosis. Our in vitro and in vivo experiments demonstrate that elevated PFKP facilitates cell proliferation, angiogenesis, and metastasis in HNSCC. Mechanistically, PFKP increases the ERK-mediated stability of c-Myc, thereby driving progression of HNSCC. Moreover, c-Myc stimulates PFKP expression at the transcriptional level, thus forming a positive feedback loop between PFKP and c-Myc. Additionally, our multiple models demonstrate that co-targeting PFKP and c-Myc triggers synergistic anti-tumor effects in HNSCC.

CONCLUSION

Our study demonstrates the critical role of the PFKP/c-Myc positive feedback loop in driving HNSCC progression and suggests that simultaneously targeting PFKP and c-Myc may be a novel and effective therapeutic strategy for HNSCC.

Human SIRT5 variants with reduced stability and activity do not cause neuropathology in mice

SIRT5 is a sirtuin deacylase that removes negatively charged lysine modifications, in the mitochondrial matrix and elsewhere in the cell. In benign cells and mouse models, under basal conditions, the phenotypes of SIRT5 deficiency are quite subtle. Here, we identify two homozygous SIRT5 variants in patients suspected to have mitochondrial disease. Both variants, P114T and L128V, are associated with reduced SIRT5 protein stability and impaired biochemical activity, with no evidence of neomorphic or dominant negative properties. The crystal structure of the P114T enzyme was solved and shows only subtle deviations from wild-type. Via CRISPR-Cas9, we generated a mouse model that recapitulates the human P114T mutation; homozygotes show reduced SIRT5 levels and activity, but no obvious metabolic abnormalities, neuropathology, or other gross phenotypes. We conclude that these human SIRT5 variants most likely represent severe hypomorphs, but are likely not by themselves the primary pathogenic cause of the neuropathology observed in the patients.

Negative Regulation of CPSF6 Suppresses the Warburg Effect and Angiogenesis Leading to Tumor Progression Via c-Myc Signaling Network: Potential Therapeutic Target for Liver Cancer Therapy

In this study, we explored the oncogenic mechanism of cleavage and polyadenylation-specific factor 6 (CPSF6) in hepatocellular carcinoma (HCC). CPSF6 was overexpressed in HCC tissues with poor survival rates compared to normal tissues. Hence, CPSF6 depletion suppressed cell viability and colony formation, induced apoptosis via PARP cleavage, and increased the sub-G1 population of Hep3B and Huh7 cells. In addition, CPSF6 enhanced the stability of c-Myc via their binding through nuclear co-localization by binding to c-Myc at the site of 258-360. Furthermore, c-Myc degradation by CPSF6 depletion was disturbed by FBW7 depletion or treatment with the proteasomal inhibitor MG132. Additionally, CPSF6 depletion suppressed the Warburg effect by inhibiting glucose, HK2, PKM2, LDH, and lactate; showed a synergistic effect with Sorafenib in Hep3B cells; and inhibited angiogenesis by tube formation and CAM assays, along with decreased expression and production of vascular endothelial growth factor (VEGF). Notably, CPSF6 depletion attenuated PD-L1 expression and increased Granzyme B levels, along with an increase in the percentage of CD4/CD8 cells in the splenocytes of BALB/c nude mice bearing Hep3B cells. Consistently, immunohistochemistry showed that CPSF6 depletion reduced the growth of Hep3B cells in BALB/c mice in orthotopic and xenograft tumor models by inhibiting tumor microenvironment-associated proteins. Overall, these findings suggest that CPSF6 enhances the Warburg effect for immune escape and angiogenesis, leading to cancer progression via c-Myc, mediated by the HK, PD-L1, and VEGF networks, with synergistic potential with sorafenib as a molecular target for liver cancer therapy.

The Selective SIRT3 Inhibitor 3-TYP Represses Primary Myeloma Growth by Reducing c-Myc Stability

Multiple myeloma is a hematological cancer that can be treated but remains incurable. With the advancement of science and technology, more drugs have been developed for myeloma chemotherapy that greatly improve the quality of life of patients. However, relapse remains a serious problem puzzling patients and doctors. Thus, developing more highly active and specific inhibitors is urgent for myeloma-targeted therapy. In this study, we identified the SIRT3 inhibitor 3-TYP (3-(1H-1,2,3-triazol-4-yl) pyridine) after screening a histone modification compound library, which showed high cytotoxicity and induced DNA damage in myeloma cells. Furthermore, the inhibitory effect of 3-TYP in our xenograft tumor studies also confirmed that compound 3-TYP could inhibit primary myeloma growth by reducing c-Myc protein stability by decreasing c-Myc Ser62 phosphorylation levels. Taken together, the results of our study identified 3-TYP as a novel c-Myc inhibitor, which could be a potential chemotherapeutic agent to target multiple myeloma.

CRL2KLHDC3 and CRL1Fbxw7 cooperatively mediate c-Myc degradation

c-Myc is a proto-oncoprotein that regulates various cellular processes and whose abnormal expression leads to tumorigenesis. c-Myc protein stability has been shown to be predominantly controlled by the ubiquitin ligase (E3) CRL1Fbxw7 in a manner dependent on glycogen synthase kinase 3 (GSK3)-mediated phosphorylation. Here we show that, in some types of cancer cells, c-Myc degradation is largely insensitive to the GSK3 inhibitor (GSK3i) CHIR99021, suggesting the existence of an E3 other than CRL1Fbxw7 for c-Myc degradation. Mass spectrometry identified CRL2KLHDC3 as such an E3. In GSK3i-insensitive cancer cells, combined depletion of Fbxw7 and KLHDC3 resulted in marked stabilization of c-Myc, suggestive of a cooperative action of Fbxw7 and KLHDC3. Furthermore, transplantation of such cells deficient in both Fbxw7 and KLHDC3 into immunodeficient mice gave rise to larger tumors compared with those formed by cells lacking only Fbxw7. GSK3i-insensitive pancreatic cancer cells expressed lower levels of SHISA2, a negative regulator of the Wnt signaling pathway, than did GSK3i-sensitive cells. KLHDC3 mRNA abundance was associated with prognosis in pancreatic cancer patients with a low level of SHISA2 gene expression. These results suggest that KLHDC3 cooperates with Fbxw7 to promote c-Myc degradation in a subset of cancer cells with low GSK3 activity.

A novel protein FNDC3B-267aa encoded by circ0003692 inhibits gastric cancer metastasis via promoting proteasomal degradation of c-Myc

BACKGROUND

Gastric cancer (GC) ranks fifth in global cancer incidence and third in mortality rate among all cancer types. Circular RNAs (circRNAs) have been extensively demonstrated to regulate multiple malignant biological behaviors in GC. Emerging evidence suggests that several circRNAs derived from FNDC3B play pivotal roles in cancer. However, the role of circFNDC3B in GC remains elusive.

METHODS

We initially screened circFNDC3B with translation potential via bioinformatics algorithm prediction. Subsequently, Sanger sequencing, qRT-PCR, RNase R, RNA-FISH and nuclear-cytoplasmic fractionation assays were explored to assess the identification and localization of circ0003692, a circRNA derived from FNDC3B. qRT-PCR and ISH were performed to quantify expression of circ0003692 in human GC tissues and adjacent normal tissues. The protein-encoding ability of circ0003692 was investigated through dual-luciferase reporter assay and LC/MS. The biological behavior of circ0003692 in GC was confirmed via in vivo and in vitro experiments. Additionally, Co-IP and rescue experiments were performed to elucidate the interaction between the encoded protein and c-Myc.

RESULTS

We found that circ0003692 was significantly downregulated in GC tissues. Circ0003692 had the potential to encode a novel protein FNDC3B-267aa, which was downregulated in GC cells. We verified that FNDC3B-267aa, rather than circ0003692, inhibited GC migration in vitro and in vivo. Mechanistically, FNDC3B-267aa directly interacted with c-Myc and promoted proteasomal degradation of c-Myc, resulting in the downregulation of c-Myc-Snail/Slug axis.

CONCLUSIONS

Our study revealed that the novel protein FNDC3B-267aa encoded by circ0003692 suppressed GC metastasis through binding to c-Myc and enhancing proteasome-mediated degradation of c-Myc. The study offers the potential applications of circ0003692 or FNDC3B-267aa as therapeutic targets for GC.

All eyes on Eya: A unique transcriptional co-activator and phosphatase in cancer

The Eya family of proteins (consisting of Eyas1-4 in mammals) play vital roles in embryogenesis by regulating processes such as proliferation, migration/invasion, cellular survival and pluripotency/plasticity of epithelial and mesenchymal states. Eya proteins carry out such diverse functions through a unique combination of transcriptional co-factor, Tyr phosphatase, and PP2A/B55α-mediated Ser/Thr phosphatase activities. Since their initial discovery, re-expression of Eyas has been observed in numerous tumor types, where they are known to promote tumor progression through a combination of their transcriptional and enzymatic activities. Eya proteins thus reinstate developmental processes during malignancy and represent a compelling class of therapeutic targets for inhibiting tumor progression.

A germline point mutation in the MYC-FBW7 phosphodegron initiates hematopoietic malignancies

Oncogenic activation of MYC in cancers predominantly involves increased transcription rather than coding region mutations. However, MYC-dependent lymphomas frequently acquire point mutations in the MYC phosphodegron, including at threonine 58 (T58), where phosphorylation permits binding via the FBW7 ubiquitin ligase triggering MYC degradation. To understand how T58 phosphorylation functions in normal cell physiology, we introduced an alanine mutation at T58 (T58A) into the endogenous c-Myc locus in the mouse germline. While MYC-T58A mice develop normally, lymphomas and myeloid leukemias emerge in ∼60% of adult homozygous T58A mice. We found that primitive hematopoietic progenitor cells from MYC-T58A mice exhibit aberrant self-renewal normally associated with hematopoietic stem cells (HSCs) and up-regulate a subset of MYC target genes important in maintaining stem/progenitor cell balance. In lymphocytes, genomic occupancy by MYC-T58A was increased at all promoters compared with WT MYC, while genes differentially expressed in a T58A-dependent manner were significantly more proximal to MYC-bound enhancers. MYC-T58A lymphocyte progenitors exhibited metabolic alterations and decreased activation of inflammatory and apoptotic pathways. Our data demonstrate that a single point mutation stabilizing MYC is sufficient to skew target gene expression, producing a profound gain of function in multipotential hematopoietic progenitors associated with self-renewal and initiation of lymphomas and leukemias.

STK16 promoted colorectal cancer progress in a c-MYC signaling-dependent manner

BACKGROUND

Colorectal cancer standed as a global health challenge, ranking third in cancer incidence and second in cancer-related deaths worldwide. A deeper understanding of the intricate mechanisms driving colorectal cancer development was pressing need. STK16 had garnered attention in recent researches, while its involvement in cancer had been minimally explored. c-MYC had emerged as a key player in cancer biology. Due to its complex structure, multifunctionality, and intricate interactions, directly inhibiting the activity of c-MYC proves to be challenging. Hence, current research was directing efforts towards modulating c-MYC expression levels.

METHODS

Immunoblot, Immunohistochemistry and immunoprecipitation assays were conducted to assess the indicated protein expression levels. RT-PCR was performed to detect the corresponding mRNA expression levels. The proliferation, migration, invasion, and colony formation abilities of the specified cancer cells were investigated using CCK8 assays, Brdu assays, transwell assays, and colony formation assays, respectively. Cellular and animal experiments were performed to investigate the correlation between STK16 signaling and c-MYC signaling.

RESULTS

STK16 plays a positive regulatory role in the progression of colorectal cancer. Delving into the molecular mechanisms, we unveiled that STK16 phosphorylated c-MYC at serine 452, a pivotal event hindering the ubiquitin-proteasome pathway degradation of c-MYC. Importantly, colorectal cancer proliferation mediated by STK16 was found to be dependent on the phosphorylation of c-MYC at S452. Furthermore, the researchers demonstrated that STK16 knockout or pharmacological inhibition significantly curtailed colorectal cancer proliferation and c-MYC expression in in vivo animal models.

CONCLUSION

We discovered that STK16 phosphorylates c-MYC at serine 452, hindering its degradation via the ubiquitin-proteasome pathway. STK16 inhibition, either genetically or pharmacologically, effectively curtails cancer growth and c-MYC expression in vivo. These findings highlight STK16 as a potential therapeutic target for colorectal cancer.

The dimeric deubiquitinase USP28 integrates 53BP1 and MYC functions to limit DNA damage

DNA replication is a major source of endogenous DNA damage in tumor cells and a key target of cellular response to genotoxic stress. DNA replication can be deregulated by oncoproteins, such as transcription factor MYC, aberrantly activated in many human cancers. MYC is stringently regulated by the ubiquitin system - for example, ubiquitination controls recruitment of the elongation factor PAF1c, instrumental in MYC activity. Curiously, a key MYC-targeting deubiquitinase USP28 also controls cellular response to DNA damage via the mediator protein 53BP1. USP28 forms stable dimers, but the biological role of USP28 dimerization is unknown. We show here that dimerization limits USP28 activity and restricts recruitment of PAF1c by MYC. Expression of monomeric USP28 stabilizes MYC and promotes PAF1c recruitment, leading to ectopic DNA synthesis and replication-associated DNA damage. USP28 dimerization is stimulated by 53BP1, which selectively binds USP28 dimers. Genotoxic stress diminishes 53BP1-USP28 interaction, promotes disassembly of USP28 dimers and stimulates PAF1c recruitment by MYC. This triggers firing of DNA replication origins during early response to genotoxins and exacerbates DNA damage. We propose that dimerization of USP28 prevents ectopic DNA replication at transcriptionally active chromatin to maintain genome stability.

Apoptotic Effect of Isoimpertorin via Inhibition of c-Myc and SIRT1 Signaling Axis

Though Isoimperatorin from Angelicae dahuricae is known to have antiviral, antidiabetic, anti-inflammatory and antitumor effects, its underlying antitumor mechanism remains elusive so far. Hence, the apoptotic mechanism of Isoimperatorin was explored in hepatocellular carcinomas (HCCs). In this study, Isoimperatorin inhibited the viability of Huh7 and Hep3B HCCs and increased the subG1 apoptotic portion and also abrogated the expression of pro-poly-ADP ribose polymerase (pro-PARP) and pro-caspase 3 in Huh7 and Hep3B cells. Also, Isoimperatorin abrogated the expression of cyclin D1, cyclin E1, CDK2, CDK4, CDK6 and increased p21 as G1 phase arrest-related proteins in Huh7 and Hep3B cells. Interestingly, Isoimperatorin reduced the expression and binding of c-Myc and Sirtuin 1 (SIRT1) by Immunoprecipitation (IP), with a binding score of 0.884 in Huh7 cells. Furthermore, Isoimperatorin suppressed the overexpression of c-Myc by the proteasome inhibitor MG132 and also disturbed cycloheximide-treated c-Myc stability in Huh7 cells. Overall, these findings support the novel evidence that the pivotal role of c-Myc and SIRT1 is critically involved in Isoimperatorin-induced apoptosis in HCCs as potent molecular targets in liver cancer therapy.

First-hit SETBP1 mutations cause a myeloproliferative disorder with bone marrow fibrosis

ABSTRACT

SETBP1 mutations are found in various clonal myeloid disorders. However, it is unclear whether they can initiate leukemia, because SETBP1 mutations typically appear as later events during oncogenesis. To answer this question, we generated a mouse model expressing mutated SETBP1 in hematopoietic tissue: this model showed profound alterations in the differentiation program of hematopoietic progenitors and developed a myeloid neoplasm with megakaryocytic dysplasia, splenomegaly, and bone marrow fibrosis, prompting us to investigate SETBP1 mutations in a cohort of 36 triple-negative primary myelofibrosis (TN-PMF) cases. We identified 2 distinct subgroups, one carrying SETBP1 mutations and the other completely devoid of somatic variants. Clinically, a striking difference in disease aggressiveness was noted, with patients with SETBP1 mutation showing a much worse clinical course. In contrast to myelodysplastic/myeloproliferative neoplasms, in which SETBP1 mutations are mostly found as a late clonal event, single-cell clonal hierarchy reconstruction in 3 patients with TN-PMF from our cohort revealed SETBP1 to be a very early event, suggesting that the phenotype of the different SETBP1+ disorders may be shaped by the opposite hierarchy of the same clonal SETBP1 variants.

AF1q is a universal marker of neuroblastoma that sustains N-Myc expression and drives tumorigenesis

Neuroblastoma is the most common extracranial malignant tumor of childhood, accounting for 15% of all pediatric cancer deaths. Despite significant advances in our understanding of neuroblastoma biology, five-year survival rates for high-risk disease remain less than 50%, highlighting the importance of identifying novel therapeutic targets to combat the disease. MYCN amplification is the most frequent and predictive molecular aberration correlating with poor outcome in neuroblastoma. N-Myc is a short-lived protein primarily due to its rapid proteasomal degradation, a potentially exploitable vulnerability in neuroblastoma. AF1q is an oncoprotein with established roles in leukemia and solid tumor progression. It is normally expressed in brain and sympathetic neurons and has been postulated to play a part in neural differentiation. However, no role for AF1q in tumors of neural origin has been reported. In this study, we found AF1q to be a universal marker of neuroblastoma tumors. Silencing AF1q in neuroblastoma cells caused proteasomal degradation of N-Myc through Ras/ERK and AKT/GSK3β pathways, activated p53 and blocked cell cycle progression, culminating in cell death via the intrinsic apoptotic pathway. Moreover, silencing AF1q attenuated neuroblastoma tumorigenicity in vivo signifying AF1q's importance in neuroblastoma oncogenesis. Our findings reveal AF1q to be a novel regulator of N-Myc and potential therapeutic target in neuroblastoma.

PRODH safeguards human naive pluripotency by limiting mitochondrial oxidative phosphorylation and reactive oxygen species production

Naive human embryonic stem cells (hESCs) that resemble the pre-implantation epiblasts are fueled by a combination of aerobic glycolysis and oxidative phosphorylation, but their mitochondrial regulators are poorly understood. Here we report that, proline dehydrogenase (PRODH), a mitochondria-localized proline metabolism enzyme, is dramatically upregulated in naive hESCs compared to their primed counterparts. The upregulation of PRODH is induced by a reduction in c-Myc expression that is dependent on PD0325901, a MEK inhibitor routinely present in naive hESC culture media. PRODH knockdown in naive hESCs significantly promoted mitochondrial oxidative phosphorylation (mtOXPHOS) and reactive oxygen species (ROS) production that triggered autophagy, DNA damage, and apoptosis. Remarkably, MitoQ, a mitochondria-targeted antioxidant, effectively restored the pluripotency and proliferation of PRODH-knockdown naive hESCs, indicating that PRODH maintains naive pluripotency by preventing excessive ROS production. Concomitantly, PRODH knockdown significantly slowed down the proteolytic degradation of multiple key mitochondrial electron transport chain complex proteins. Thus, we revealed a crucial role of PRODH in limiting mtOXPHOS and ROS production, and thereby safeguarding naive pluripotency of hESCs.

MYC Oncogene: A Druggable Target for Treating Cancers with Natural Products

Various diseases, including cancers, age-associated disorders, and acute liver failure, have been linked to the oncogene, MYC. Animal testing and clinical trials have shown that sustained tumor volume reduction can be achieved when MYC is inactivated, and different combinations of therapeutic agents including MYC inhibitors are currently being developed. In this review, we first provide a summary of the multiple biological functions of the MYC oncoprotein in cancer treatment, highlighting that the equilibrium points of the MYC/MAX, MIZ1/MYC/MAX, and MAD (MNT)/MAX complexes have further potential in cancer treatment that could be used to restrain MYC oncogene expression and its functions in tumorigenesis. We also discuss the multifunctional capacity of MYC in various cellular cancer processes, including its influences on immune response, metabolism, cell cycle, apoptosis, autophagy, pyroptosis, metastasis, angiogenesis, multidrug resistance, and intestinal flora. Moreover, we summarize the MYC therapy patent landscape and emphasize the potential of MYC as a druggable target, using herbal medicine modulators. Finally, we describe pending challenges and future perspectives in biomedical research, involving the development of therapeutic approaches to modulate MYC or its targeted genes. Patients with cancers driven by MYC signaling may benefit from therapies targeting these pathways, which could delay cancerous growth and recover antitumor immune responses.

T cell help induces Myc transcriptional bursts in germinal center B cells during positive selection

Antibody affinity maturation occurs in secondary lymphoid organs within germinal centers (GCs). At these sites, B cells mutate their antibody-encoding genes in the dark zone, followed by preferential selection of the high-affinity variants in the light zone by T cells. The strength of the T cell-derived selection signals is proportional to the B cell receptor affinity and to the magnitude of subsequent Myc expression. However, because the lifetime of Myc mRNA and its corresponding protein is very short, it remains unclear how T cells induce sustained Myc levels in positively selected B cells. Here, by direct visualization of mRNA and active transcription sites in situ, we found that an increase in transcriptional bursts promotes Myc expression during B cell positive selection in GCs. Elevated T cell help signals predominantly enhance the percentage of cells expressing Myc in GCs as opposed to augmenting the quantity of Myc transcripts per individual cell. Visualization of transcription start sites in situ revealed that T cell help promotes an increase in the frequency of transcriptional bursts at the Myc locus in GC B cells located primarily in the LZ apical rim. Thus, the rise in Myc, which governs positive selection of B cells in GCs, reflects an integration of transcriptional activity over time rather than an accumulation of transcripts at a specific time point.

Acetylation of c-Myc at Lysine 148 Protects Neurons After Ischemia

This study focuses on understanding the role of c-Myc, a cancer-associated transcription factor, in the penumbra following ischemic stroke. While its involvement in cell death and survival is recognized, its post-translational modifications, particularly acetylation, remain understudied in ischemia models. Investigating these modifications could have significant clinical implications for controlling c-Myc activity in the central nervous system. Although previous studies on c-Myc acetylation have been limited to non-neuronal cells, our research examines its expression in perifocal cells during stroke recovery to explore regulatory mechanisms via acetylation. We found that in peri-infarct neurons, c-Myc is upregulated with acetylation at K148 but not K323 during the acute phase of stroke, with SIRT2 deacetylase primarily affecting K148 acetylation. Molecular dynamics simulations suggest that lysine 148 plays a crucial role in stabilizing c-Myc spatial structure. Increased acetylation at K148 reduces c-Myc compaction, potentially limiting its nuclear penetration, promoting calpain-mediated cleavage, and decreasing nuclear localization. Additionally, cytoplasmic acetylation at K148 may alter c-Myc's interaction with unidentified proteins, potentially influencing its pro-apoptotic effects and promoting cytoplasmic accumulation. Targeting SIRT2 with selective inhibitors could be a promising avenue for future stroke therapy strategies.