Tilting MYC toward cancer cell death

Directly Suppressing MYC Function with Novel Alkynyl-Substituted Phenylpyrazole Derivatives that Induce Protein Degradation and Perturb MYC/MAX Interaction

Despite being a highly sought-after therapeutic target for human malignancies, myelocytomatosis viral oncogene homologue (MYC) has been considered intractable due to its intrinsically disordered nature, making the discovery of in vivo effective inhibitors that directly block its function challenging. Herein, we report structurally novel alkynyl-substituted phenylpyrazole derivatives directly perturbing MYC function. Among them, compound 37 exhibited superior antiproliferative activities to those of MYCi975 against multiple malignant cell lines. It induced dose-dependent MYC degradation in cells with degradation observed at the concentration as low as 1.0 μM. Meanwhile, its direct suppression of MYC function was confirmed by the capability to inhibit the binding of MYC/MYC-associated protein X (MAX) heterodimer to DNA consensus sequence, induce MYC thermal instability, and disturb MYC/MAX interaction. Moreover, 37 demonstrated enhanced therapeutic efficacy over MYCi975 in a mouse allograft model of prostate cancer. Overall, 37 deserves further development for exploring MYC-targeting cancer therapeutics.

Phosphorylation of USP27X by PIM2 promotes glycolysis and breast cancer progression via deubiquitylation of MYC

Aberrant cell proliferation is a hallmark of cancer, including breast cancer. Here, we show that USP27X is required for cell proliferation and tumorigenesis in breast cancer. We identify a PIM2-USP27X regulator of MYC signaling axis whose activity is an important contributor to the tumor biology of breast cancer. PIM2 phosphorylates USP27X, and promotes its deubiquitylation activity for MYC, which promotes its protein stability and leads to increase HK2-mediated aerobic glycolysis in breast cancer. Moreover, the PIM2-USP27X-MYC axis is also validated in PIM2-knockout mice. Taken together, these findings show a PIM2-USP27X-MYC signaling axis as a new potential target for breast cancer treatment.

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.

Multi-dimensional characterization of apoptosis in the tumor microenvironment and therapeutic relevance in melanoma

PURPOSE

Melanoma is widely utilized as a prominent model for the development of immunotherapy, thought an inadequate immune response can occur. Moreover, the development of apoptosis-related therapies and combinations with other therapeutic strategies is impeded by the limited understanding of apoptosis's role within diverse tumor immune microenvironments (TMEs).

METHODS

Here, we constructed an apoptosis-related tumor microenvironment signature (ATM) and employ multi-dimensional analysis to understand the roles of apoptosis in tumor microenvironment. We further assessed the clinical applications of ATM in nine independent cohorts, and anticipated the impact of ATM on cellular drug response in cultured cells.

RESULTS

Our ATM model exhibits robust performance in survival prediction in multiple melanoma cohorts. Different ATM groups exhibited distinct molecular signatures and biological processes. The low ATM group exhibited significant enrichment in B cell activation-related pathways. What's more, plasma cells showed the lowest ATM score, highlighting their role as pivotal contributors in the ATM model. Mechanistically, the analysis of the interplay between plasma cells and other immune cells elucidated their crucial role in orchestrating an effective anti-tumor immune response. Significantly, the ATM signature exhibited associations with therapeutic efficacy of immune checkpoint blockade and the drug sensitivity of various agents, including FDA-approved and clinically utilized drugs targeting the VEGF signaling pathway. Finally, ATM was associated with tertiary lymphoid structures (TLS), exhibiting stronger patient stratification ability compared to classical "hot tumors".

CONCLUSION

Our findings indicate that ATM is a prognostic factor and is associated with the immune response and drug sensitivity in melanoma.

Ribosomal protein L22 like 1: a promising biomarker for lung adenocarcinoma

No studies have reported the effect of ribosomal protein L22 like 1 (RPL22L1) in lung adenocarcinoma (LUAD). Therefore, we aimed to systematically investigate the role of RPL22L1 in LUAD. The expression of RPL22L1 was analyzed using TCGA, GEO, TIMER, UALCAN databases, and validated by immunohistochemistry (IHC). Gene methylation analysis was performed using the UALCAN, GSCA and MethSurv databases. The immune infiltrates were investigated using the Single Sample Gene Set Enrichment Analysis (ssGSEA), TIMER database, and TISCH database. The results demonstrated that RPL22L1 was up-regulated in LUAD, and verified by IHC. Kaplan-Meier analysis suggested that patients with high RPL22L1 expression had poor prognosis. Multivariate analysis confirmed that RPL22L1 was an independent prognostic factor. Furthermore, RPL22L1 overexpression was associated with hypomethylation, and two CpGs of RPL22L1 were significantly associated with prognosis. Up-regulated RPL22L1 was enriched in MYC targets, E2F targets, G2M checkpoint, mTORC1 signaling, cell cycle, and so on. Moreover, RPL22L1 expression was negatively correlated with immune cell infiltration, and patients with high RPL22L1 expression had lower immune, stromal, and estimate scores. Single-cell analysis suggested that RPL22L1 might have a potential function in the tumor microenvironment (TME) of LUAD. In conclusion, RPL22L1 may be a promising biomarker for LUAD.

MYC-Targeting Inhibitors Generated from a Stereodiversified Bicyclic Peptide Library

Here, we present the second generation of our bicyclic peptide library (NTB), featuring a stereodiversified structure and a simplified construction strategy. We utilized a tandem ring-opening metathesis and ring-closing metathesis reaction (ROM-RCM) to cyclize the linear peptide library in a single step, representing the first reported instance of this reaction being applied to the preparation of macrocyclic peptides. Moreover, the resulting bicyclic peptide can be easily linearized for MS/MS sequencing with a one-step deallylation process. We employed this library to screen against the E363-R378 epitope of MYC and identified several MYC-targeting bicyclic peptides. Subsequent in vitro cell studies demonstrated that one candidate, NT-B2R, effectively suppressed MYC transcription activities and cell proliferation.

NEK8 regulates colorectal cancer progression via phosphorylating MYC

Radiotherapy and chemotherapy remain the mainstay of treatment for colorectal cancer (CRC), although their efficacy is limited. A detailed understanding of the molecular mechanisms underlying CRC progression could lead to the development of new therapeutic strategies. Although it has been established that MYC signaling is dysregulated in various human cancers, direct targeting MYC remains challenging due to its "undruggable" protein structure. Post-translational modification of proteins can affect their stability, activation, and subcellular localization. Hence, targeting the post-translational modification of MYC represents a promising approach to disrupting MYC signaling. Herein, we revealed that NEK8 positively regulates CRC progression by phosphorylating c-MYC protein at serine 405, which exhibited enhanced stability via polyubiquitination. Our findings shed light on the role of NEK8/MYC signaling in CRC progression, offering a novel and helpful target for colorectal cancer treatment. Video Abstract.

RUNX3 inactivates oncogenic MYC through disruption of MYC/MAX complex and subsequent recruitment of GSK3β-FBXW7 cascade

MYC is one of the most commonly dysregulated proto-oncogenes in cancer. MYC promotes cancer initiation and maintenance by regulating multiple biological processes, such as proliferation and stem cell function. Here, we show that developmental regulator RUNX3 targets MYC protein for rapid degradation through the glycogen synthase kinase-3 beta-F-box/WD repeat-containing protein 7 (GSK3β-FBXW7) proteolytic pathway. The evolutionarily conserved Runt domain of RUNX3 interacts directly with the basic helix-loop-helix leucine zipper of MYC, resulting in the disruption of MYC/MAX and MYC/MIZ-1 interactions, enhanced GSK3β-mediated phosphorylation of MYC protein at threonine-58 and its subsequent degradation via the ubiquitin-proteasomal pathway. We therefore uncover a previously unknown mode of MYC destabilization by RUNX3 and provide an explanation as to why RUNX3 inhibits early-stage cancer development in gastrointestinal and lung mouse cancer models.

Breast cancer sub-types display heterogeneity in gene amplification and mRNA expression of the anti-apoptotic members of BCL2 family

BACKGROUND

Progress in therapies and improved outcomes in recent decades have followed a better understanding of breast cancers pathogenesis and their heterogeneity but new treatments are needed especially for metastatic disease which remains incurable. Inhibition of apoptosis is a hallmark characteristic of cancer and can be targeted for therapy.

METHODS

The five anti-apoptotic members of the BCL2 family are at the core of apoptosis execution and are involved in apoptosis evasion of transformed cells. Genetic lesions as well as mRNA regulation of these members in breast cancer and its sub-types and implications for survival outcomes were investigated using data from various publicly available databases.

RESULTS

Genes encoding for anti-apoptotic BCL2 proteins are rarely mutated in breast cancer and copy number alterations are observed only in MCL1 gene which is amplified in a minority of breast cancer ranging from 1.6% to 18.7% in breast cancers. Over-expression of BCL2, BCL-X and MCL1 is observed in luminal A cancers, while cases of luminal B and basal breast cancers display mRNA up-regulation of BCL-X and MCL1, respectively. Basal cancers possess also more frequently than other sub-sets MCL1 amplifications. Survival outcomes are not significantly different in cancers with higher expression of anti-apoptotic BCL2 mRNAs.

CONCLUSION

Therapeutic targeting of the apoptotic process in breast cancer sub-types will be improved by a detailed understanding of the core players in the process, including anti-apoptotic BCL2 family proteins. A sub-set of breast cancers harbor amplifications of MCL1 and dysregulations of expression of most family members that could affect the sensitivity to their inhibition by altering the cell's apoptotic threshold.

RPS24 Is Associated with a Poor Prognosis and Immune Infiltration in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common type of primary liver malignancy, with increased mortality and morbidity. Accumulating evidence suggested that 40S ribosomal protein S24 (RPS24) is related to malignant outcomes and progression. However, the role of RPS24 remains unclear in HCC. The mRNA and protein expression pattern of RPS24 in HCC was explored and confirmed based on the bioinformatics analysis and histological examination. The correlation between RPS24 expression and clinicopathological features, diagnostic value, prognosis, methylation status, and survival were evaluated. Then, we divided the HCC cohort into two groups based on the expression of RPS24, and performed the functional enrichment and immune cells infiltration analysis of RPS24. Furthermore, in vivo and in vitro experiments were performed to investigate the effect of RPS24 on HCC cells. RPS24 was observed to be elevated in HCC samples. RPS24 overexpression or RPS24 promoter methylation contributed to an unfavorable prognosis for HCC patients. The genes in the high RPS24 expression group were mainly enriched in DNA replication, cell cycle E2F targets, and the G2M checkpoint pathway. Moreover, the expression level of RPS24 was significantly related to immune infiltration and immunotherapy response. Our experiments also demonstrated that RPS24 knockdown suppressed the growth of HCC cells and tumor proliferation of the xenograft model. Therefore, RPS24 can be a potential adverse biomarker of HCC prognosis acting through facilitating cell proliferation and the formation of an immunosuppressive microenvironment in HCC. Targeting RPS24 may offer a promising therapeutic option for HCC management.

Cell senescence-associated genes predict the malignant characteristics of glioblastoma

BACKGROUND

Glioblastoma (GBM) is the most malignant, aggressive and recurrent primary brain tumor. Cell senescence can cause irreversible cessation of cell division in normally proliferating cells. According to studies, senescence is a primary anti-tumor mechanism that may be seen in a variety of tumor types. It halts the growth and spread of tumors. Tumor suppressive functions held by cellular senescence provide new directions and pathways to promote cancer therapy.

METHODS

We comprehensively analyzed the cell senescence-associated genes expression patterns. The potential molecular subtypes were acquired based on unsupervised cluster analysis. The tumor immune microenvironment (TME) variations, immune cell infiltration, and stemness index between 3 subtypes were analyzed. To identify genes linked with GBM prognosis and build a risk score model, we used weighted gene co-expression network analysis (WGCNA), univariate Cox regression, Least absolute shrinkage and selection operator regression (LASSO), and multivariate Cox regression analysis. And the correlation between risk scores and clinical traits, TME, GBM subtypes, as well as immunotherapy responses were estimated. Immunohistochemistry (IHC) and cellular experiments were performed to evaluate the expression and function of representative genes. Then the 2 risk scoring models were constructed based on the same method of calculation whose samples were acquired from the CGGA dataset and TCGA datasets to verify the rationality and the reliability of the risk scoring model. Finally, we conducted a pan-cancer analysis of the risk score, assessed drug sensitivity based on risk scores, and analyzed the pathways of sensitive drug action.

RESULTS

The 3 potential molecular subtypes were acquired based on cell senescence-associated genes expression. The Log-rank test showed the difference in GBM patient survival between 3 potential molecular subtypes (P = 0.0027). Then, 11 cell senescence-associated genes were obtained to construct a risk-scoring model, which was systematically randomized to distinguish the train set (n = 293) and the test set (n = 292). The Kaplan-Meier (K-M) analyses indicated that the high-risk score in the train set (P < 0.0001), as well as the test set (P = 0.0053), corresponded with poorer survival. In addition, the high-risk score group showed a poor response to immunotherapy. The reliability and credibility of the risk scoring model were confirmed according to the CGGA dataset, TCGA datasets, and Pan-cancer analysis. According to drug sensitivity analysis, it was discovered that LJI308, a potent selective inhibitor of RSK pathways, has the highest drug sensitivity. Moreover, the GBM patients with higher risk scores may potentially be more beneficial from drugs that target cell cycle, mitosis, microtubule, DNA replication and apoptosis regulation signaling.

CONCLUSION

We identified potential associations between clinical characteristics, TME, stemness, subtypes, and immunotherapy, and we clarified the therapeutic usefulness of cell senescence-associated genes.

Stabilization of the c-Myc Protein via the Modulation of Threonine 58 and Serine 62 Phosphorylation by the Disulfiram/Copper Complex in Oral Cancer Cells

MYC has a short half-life that is tightly regulated through phosphorylation and proteasomal degradation. Many studies have claimed that treatment with disulfiram (DSF) with or without copper ions can cause cancer cell death in a reactive oxygen species (ROS)-dependent manner in cancer cells. Our previous study showed that the levels of c-Myc protein and the phosphorylation of threonine 58 (T58) and serine 62 (S62) increased in DSF-Cu-complex-treated oral epidermoid carcinoma Meng-1 (OECM-1) cells. These abovementioned patterns were suppressed by pretreatment with an ROS scavenger, N-acetyl cysteine. The overexpression of c-Myc failed to induce hypoxia-inducible factor 1α protein expression, which was stabilized by the DSF-Cu complex. In this study, we further examined the regulatory mechanism behind the induction of the c-Myc of the DSF-Cu complex in an OECM-1 cell compared with a Smulow–Glickman (SG) human normal gingival epithelial cell. Our data showed that the downregulation of c-Myc truncated nick and p62 and the induction of the ratio of H3P/H3 and p-ERK/ERK might not be involved in the increase in the amount of c-Myc via the DSF/copper complexes in OECM-1 cells. Combined with the inhibitors for various signaling pathways and cycloheximde treatment, the increase in the amount of c-Myc with the DSF/copper complexes might be mediated through the increase in the stabilities of c-Myc (T58) and c-Myc (S62) proteins in OECM-1 cells. In SG cells, only the c-Myc (T58) protein was stabilized by the DSF-Cu (I and II) complexes. Hence, our findings could provide novel regulatory insights into the phosphorylation-dependent stability of c-Myc in DSF/copper-complex-treated oral squamous cell carcinoma.

Decreased CD11c-positive dendritic cells in the tumor microenvironment predict double-hit/triple-hit genotype and survival in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma and is a potentially curable disease. However, it is heterogenous, and the prognosis is poor if the tumor cells harbor fusions involving MYC and BCL2 or MYC and BCL6 (double-hit [DH] lymphoma), or fusions involving all three genes (triple-hit [TH] lymphoma). Fluorescence in situ hybridization is currently the gold standard for confirming the presence of DH/TH genotypes. However, the test is laborious and not readily available in some laboratories. Germinal center B (GCB) signatures and dual expression of MYC and BCL2 are commonly used as initial screening markers (traditional model) in clinical practice. Our study proposes immunohistochemical markers for more conveniently and accessibly screening DH/TH genotypes in DLBCL. We retrospectively reviewed the clinical and pathological parameters of patients with DLBCL. We assessed the proliferative index, apoptotic index, and tumor microenvironment (TME), with regard to T cells and CD11c(+) dendritic cells, in formalin-fixed paraffin-embedded tissue. We then generated a decision tree as a screening algorithm to predict DH/TH genotypes and employed decision curve analysis to demonstrate the superiority of this new model in prediction. We also assessed the prognostic significance of related parameters. Our study revealed that GCB subtypes, a Ki67 proliferative index higher than 70%, and BCL2 expression were significantly associated with DH/TH genotypes. Decreased CD11c(+) dendritic cells in the TME indicated additional risk. Our proposed screening algorithm outperformed a traditional model in screening for the DH/TH genotypes. In addition, decreased CD11c(+) dendritic cells in the DLBCL TME were an independent unfavorable prognosticator. In conclusion, we provide a convenient, well-performing model that predicts DH/TH genotypes in DLBCL. The prognostic significance of CD11c(+) dendritic cells in the TME might influence the classification and development of immunotherapy for DLBCL in the future.

Sex, life, and death in MYC-driven lymphomagenesis

Gong et al. (2021) demonstrate that MYC-induced proteotoxic stress could be relieved by inactivating RNA helicase DDX3X for tumor initiation, and in male MYC-driven lymphomas, the homologous helicase DDX3Y, encoded on the Y chromosome, is subsequently induced for disease progression.