WTAP/IGF2BP3-mediated GBE1 expression accelerates the proliferation and enhances stemness in pancreatic cancer cells via upregulating c-Myc.

BACKGROUND: Pancreatic cancer (PC) is one of the most malignant cancers with highly aggressiveness and poor prognosis. N6-methyladenosine (m6A) have been indicated to be involved in PC development. Glucan Branching Enzyme 1 (GBE1) is mainly involved in cell glycogen metabolism. However, the function of GBE1 and Whether GBE1 occurs m6A modification in PC progression remains to be illustrated. METHODS: The clinical prognosis of GBE1 was analyzed through online platform. The expression of GBE1 was obtained from online platform and then verified in normal and PC cell lines. Lentivirus was used to generated GBE1 stable-overexpression or knockdown PC cells. Cell Counting Kit (CCK-8), colony formation assay, sphere formation assay and flow cytometry assay were conducted to analyze cell proliferation and stemness ability in vitro. Subcutaneous and orthotopic mouse models were used to verify the function of GBE1 in vivo. RNA immunoprecipitation (RIP) assay, RNA stability experiment and western blots were conducted to explore the molecular regulation of GBE1 in PC. RESULTS: GBE1 was significantly upregulated in PC and associated with poor prognosis of PC patients. Functionally, GBE1 overexpression facilitated PC cell proliferation and stemness-like properties, while knockdown of GBE1 attenuated the malignancy of PC cells. Importantly, we found the m6A modification of GBE1 RNA, and WTAP and IGF2BP3 was revealed as the m6A regulators to increase GBE1 mRNA stability and expression. Furthermore, c-Myc was discovered as a downstream gene of GBE1 and functional rescue experiments showed that overexpression of c-Myc could rescue GBE1 knockdown-induced PC cell growth inhibition. CONCLUSIONS: Our study uncovered the oncogenic role of GBE1/c-Myc axis in PC progression and revealed WTAP/IGF2BP3-mediated m6A modification of GBE1, which highlight the potential application of GBE1 in the targeted therapy of PC.

Polyamine and EIF5A hypusination downstream of c-Myc confers targeted therapy resistance in BRAF mutant melanoma.

BACKGROUND: BRAF inhibitors are widely employed in the treatment of melanoma with the BRAF V600E mutation. However, the development of resistance compromises their therapeutic efficacy. Diverse genomic and transcriptomic alterations are found in BRAF inhibitor resistant melanoma, posing a pressing need for convergent, druggable target that reverse therapy resistant tumor with different resistance mechanisms. METHODS: CRISPR-Cas9 screens were performed to identify novel target gene whose inhibition selectively targets A375VR, a BRAF V600E mutant cell line with acquired resistance to vemurafenib. Various in vitro and in vivo assays, including cell competition assay, water soluble tetrazolium (WST) assay, live-dead assay and xenograft assay were performed to confirm synergistic cell death. Liquid Chromatography-Mass Spectrometry analyses quantified polyamine biosynthesis and changes in proteome in vemurafenib resistant melanoma. EIF5A hypusination dependent protein translation and subsequent changes in mitochondrial biogenesis and activity were assayed by O-propargyl-puromycin labeling assay, mitotracker, mitoSOX labeling and seahorse assay. Bioinformatics analyses were used to identify the association of polyamine biosynthesis with BRAF inhibitor resistance and poor prognosis in melanoma patient cohorts. RESULTS: We elucidate the role of polyamine biosynthesis and its regulatory mechanisms in promoting BRAF inhibitor resistance. Leveraging CRISPR-Cas9 screens, we identify AMD1 (S-adenosylmethionine decarboxylase 1), a critical enzyme for polyamine biosynthesis, as a druggable target whose inhibition reduces vemurafenib resistance. Metabolomic and proteomic analyses reveal that polyamine biosynthesis is upregulated in vemurafenib-resistant cancer, resulting in enhanced EIF5A hypusination, translation of mitochondrial proteins and oxidative phosphorylation. We also identify that sustained c-Myc levels in vemurafenib-resistant cancer are responsible for elevated polyamine biosynthesis. Inhibition of polyamine biosynthesis or c-Myc reversed vemurafenib resistance both in vitro cell line models and in vivo in a xenograft model. Polyamine biosynthesis signature is associated with poor prognosis and shorter progression free survival after BRAF/MAPK inhibitor treatment in melanoma cohorts, highlighting the clinical relevance of our findings. CONCLUSIONS: Our findings delineate the molecular mechanisms involving polyamine-EIF5A hypusination-mitochondrial respiration pathway conferring BRAF inhibitor resistance in melanoma. These targets will serve as effective therapeutic targets that can maximize the therapeutic efficacy of existing BRAF inhibitors.

GNA13 suppresses proliferation of ER+ breast cancer cells via ERα dependent upregulation of the MYC oncogene.

GNA13 (Gα13) is one of two alpha subunit members of the G12/13 family of heterotrimeric G-proteins which mediate signaling downstream of GPCRs. It is known to be essential for embryonic development and vasculogenesis and has been increasingly shown to be involved in mediating several steps of cancer progression. Recent studies found that Gα13 can function as an oncogene and contributes to progression and metastasis of multiple tumor types, including ovarian, head and neck and prostate cancers. In most cases, Gα12 and Gα13, as closely related α-subunits in the subfamily, have similar cellular roles. However, in recent years their differences in signaling and function have started to emerge. We previously identified that Gα13 drives invasion of Triple Negative Breast Cancer (TNBC) cells in vitro. As a highly heterogenous disease with various well-defined molecular subtypes (ER+ /Her2-, ER+ /Her2+, Her2+, TNBC) and subtype associated outcomes, the function(s) of Gα13 beyond TNBC should be explored. Here, we report the finding that low expression of GNA13 is predictive of poorer survival in breast cancer, which challenges the conventional idea of Gα12/13 being universal oncogenes in solid tumors. Consistently, we found that Gα13 suppresses the proliferation in multiple ER+ breast cancer cell lines (MCF-7, ZR-75-1 and T47D). Loss of GNA13 expression drives cell proliferation, soft-agar colony formation and in vivo tumor formation in an orthotopic xenograft model. To evaluate the mechanism of Gα13 action, we performed RNA-sequencing analysis on these cell lines and found that loss of GNA13 results in the upregulation of MYC signaling pathways in ER+ breast cancer cells. Simultaneous silencing of MYC reversed the proliferative effect from the loss of GNA13, validating the role of MYC in Gα13 regulation of proliferation. Further, we found Gα13 regulates the expression of MYC, at both the transcript and protein level in an ERα dependent manner. Taken together, our study provides the first evidence for a tumor suppressive role for Gα13 in breast cancer cells and demonstrates for the first time the direct involvement of Gα13 in ER-dependent regulation of MYC signaling. With a few exceptions, elevated Gα13 levels are generally considered to be oncogenic, similar to Gα12. This study demonstrates an unexpected tumor suppressive role for Gα13 in ER+ breast cancer via regulation of MYC, suggesting that Gα13 can have subtype-dependent tumor suppressive roles in breast cancer.

Positive feedback loop of c-myc/XTP6/NDH2/NF-κB to promote malignant progression in glioblastoma.

BACKGROUND: Recent studies have highlighted the significant role of the NF-κB signaling pathway in the initiation and progression of cancer. Furthermore, long noncoding RNAs (lncRNAs) have been identified as pivotal regulators in sustaining the NF-κB signaling pathway's functionality. Despite these findings, the underlying molecular mechanisms through which lncRNAs influence the NF-κB pathway remain largely unexplored. METHODS: Bioinformatic analyses were utilized to investigate the differential expression and prognostic significance of XTP6. The functional roles of XTP6 were further elucidated through both in vitro and in vivo experimental approaches. To estimate the interaction between XTP6 and NDH2, RNA pulldown and RNA Immunoprecipitation (RIP) assays were conducted. The connection between XTP6 and the IκBα promoter was examined using Chromatin Isolation by RNA Purification (ChIRP) assays. Additionally, Chromatin Immunoprecipitation (ChIP) assays were implemented to analyze the binding affinity of c-myc to the XTP6 promoter, providing insights into the regulatory mechanisms at play. RESULTS: XTP6 was remarkedly upregulated in glioblastoma multiforme (GBM) tissues and was connected with adverse prognosis in GBM patients. Our investigations revealed that XTP6 can facilitate the malignant progression of GBM both in vitro and in vivo. Additionally, XTP6 downregulated IκBα expression by recruiting NDH2 to the IκBα promoter, which resulted in elevated levels of H3K27me3, thereby reducing the transcriptional activity of IκBα. Moreover, the progression of GBM was further driven by the c-myc-mediated upregulation of XTP6, establishing a positive feedback loop with IκBα that perpetuated the activation of the NF-κB signaling pathway. Notably, the application of an inhibitor targeting the NF-κB signaling pathway effectively inhibited the continuous activation induced by XTP6, leading to a significant reduction in tumor formation in vivo. CONCLUSION: The results reveal that XTP6 unveils an innovative epigenetic mechanism instrumental in the sustained activation of the NF-κB signaling pathway, suggesting a promising therapeutic target for the treatment of GBM.

KMT2D-mediated H3K4me1 recruits YBX1 to facilitate triple-negative breast cancer progression through epigenetic activation of c-Myc.

BACKGROUND: Lysine methyltransferase 2D (KMT2D) mediates mono-methylation of histone H3 lysine 4 (H3K4me1) in mammals. H3K4me1 mark is involved in establishing an active chromatin structure to promote gene transcription. However, the precise molecular mechanism underlying the KMT2D-mediated H3K4me1 mark modulates gene expression in triple-negative breast cancer (TNBC) progression is unresolved. METHODS AND RESULTS: We recognized Y-box-binding protein 1 (YBX1) as a "reader" of the H3K4me1 mark, and a point mutation of YBX1 (E121A) disrupted this interaction. We found that KMT2D and YBX1 cooperatively promoted cell growth and metastasis of TNBC cells in vitro and in vivo. The expression levels of KMT2D and YBX1 were both upregulated in tumour tissues and correlated with poor prognosis for breast cancer patients. Combined analyses of ChIP-seq and RNA-seq data indicated that YBX1 was co-localized with KMT2D-mediated H3K4me1 in the promoter regions of c-Myc and SENP1, thereby activating their expressions in TNBC cells. Moreover, we demonstrated that YBX1 activated the expressions of c-Myc and SENP1 in a KMT2D-dependent manner. CONCLUSION: Our results suggest that KMT2D-mediated H3K4me1 recruits YBX1 to facilitate TNBC progression through epigenetic activation of c-Myc and SENP1. These results together unveil a crucial interplay between histone mark and gene regulation in TNBC progression, thus providing novel insights into targeting the KMT2D-H3K4me1-YBX1 axis for TNBC treatment. HIGHLIGHTS: YBX1 is a KMT2D-mediated H3K4me1-binding effector protein and mutation of YBX1 (E121A) disrupts its binding to H3K4me1. KMT2D and YBX1 cooperatively promote TNBC proliferation and metastasis by activating c-Myc and SENP1 expression in vitro and in vivo. YBX1 is colocalized with H3K4me1 in the c-Myc and SENP1 promoter regions in TNBC cells and increased YBX1 expression predicts a poor prognosis in breast cancer patients.

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 ß-transducin repeat-containing protein (ß-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 ß-TrCP/c-Myc/HK2 pathway, suggesting its potential as a prognostic biomarker and therapeutic target in CRC.

SAHA/5-AZA Enhances Acetylation and Degradation of mutp53, Upregulates p21 and Downregulates c-Myc and BRCA-1 in Pancreatic Cancer Cells.

Epigenetic changes are common in cancer and include aberrant DNA methylation and histone modifications, including both acetylation or methylation. DNA methylation in the promoter regions and histone deacetylation are usually accompanied by gene silencing, and may lead to the suppression of tumor suppressors in cancer cells. An interaction between epigenetic pathways has been reported that could be exploited to more efficiently target aggressive cancer cells, particularly those against which current treatments usually fail, such as pancreatic cancer. In this study, we explored the possibility to combine the DNA demethylating agent 5-AZA with HDAC inhibitor SAHA to treat pancreatic cancer cell lines, focusing on the acetylation of mutp53 and the consequences on its stability, as well as on the interaction of this protein with c-myc and BRCA-1, key molecules in cancer survival. The results obtained suggest that SAHA/5-AZA combination was more effective than single treatments to promote the degradation of mutp53, to upregulate p21 and downregulate c-Myc and BRCA-1, thus increasing DNA damage and cytotoxicity in pancreatic cancer cells.

Metabolic Reprogramming Is an Initial Step in Pancreatic Carcinogenesis That Can Be Targeted to Inhibit Acinar-to-Ductal Metaplasia.

Metabolic reprogramming is a hallmark of cancer and is crucial for cancer progression, making it an attractive therapeutic target. Understanding the role of metabolic reprogramming in cancer initiation could help identify prevention strategies. To address this, we investigated metabolism during acinar-to-ductal metaplasia (ADM), the first step of pancreatic carcinogenesis. Glycolytic markers were elevated in ADM lesions compared with normal tissue from human samples. Comprehensive metabolic assessment in three mouse models with pancreas-specific activation of KRAS, PI3K, or MEK1 using Seahorse measurements, nuclear magnetic resonance metabolome analysis, mass spectrometry, isotope tracing, and RNA sequencing analysis revealed a switch from oxidative phosphorylation to glycolysis in ADM. Blocking the metabolic switch attenuated ADM formation. Furthermore, mitochondrial metabolism was required for de novo synthesis of serine and glutathione (GSH) but not for ATP production. MYC mediated the increase in GSH intermediates in ADM, and inhibition of GSH synthesis suppressed ADM development. This study thus identifies metabolic changes and vulnerabilities in the early stages of pancreatic carcinogenesis. Significance: Metabolic reprogramming from oxidative phosphorylation to glycolysis mediated by MYC plays a crucial role in the development of pancreatic cancer, revealing a mechanism driving tumorigenesis and potential therapeutic targets. See related commentary by Storz, p. 2225.

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

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

Targeting specific DNA G-quadruplexes with CRISPR-guided G-quadruplex-binding proteins and ligands.

Despite the demonstrated importance of DNA G-quadruplexes (G4s) in health and disease, technologies to readily manipulate specific G4 folding for functional analysis and therapeutic purposes are lacking. Here we employ G4-stabilizing protein/ligand in conjunction with CRISPR to selectively facilitate single or multiple targeted G4 folding within specific genomic loci. We demonstrate that fusion of nucleolin with a catalytically inactive Cas9 can specifically stabilize G4s in the promoter of oncogene MYC and muscle-associated gene Itga7 as well as telomere G4s, leading to cell proliferation arrest, inhibition of myoblast differentiation and cell senescence, respectively. Furthermore, CRISPR can confer intra-G4 selectivity to G4-binding compounds pyridodicarboxamide and pyridostatin. Compared with traditional G4 ligands, CRISPR-guided biotin-conjugated pyridodicarboxamide enables a more precise investigation into the biological functionality of de novo G4s. Our study provides insights that will enhance understanding of G4 functions and therapeutic interventions.

Dual inhibition of SUMOylation and MEK conquers MYC-expressing KRAS-mutant cancers by accumulating DNA damage.

BACKGROUND: KRAS mutations frequently occur in cancers, particularly pancreatic ductal adenocarcinoma, colorectal cancer, and non-small cell lung cancer. Although KRASG12C inhibitors have recently been approved, effective precision therapies have not yet been established for all KRAS-mutant cancers. Many treatments for KRAS-mutant cancers, including epigenome-targeted drugs, are currently under investigation. Small ubiquitin-like modifier (SUMO) proteins are a family of small proteins covalently attached to and detached from other proteins in cells via the processes called SUMOylation and de-SUMOylation. We assessed whether SUMOylation inhibition was effective in KRAS-mutant cancer cells. METHODS: The efficacy of the first-in-class SUMO-activating enzyme E inhibitor TAK-981 (subasumstat) was assessed in multiple human and mouse KRAS-mutated cancer cell lines. A gene expression assay using a TaqMan array was used to identify biomarkers of TAK-981 efficacy. The biological roles of SUMOylation inhibition and subsequent regulatory mechanisms were investigated using immunoblot analysis, immunofluorescence assays, and mouse models. RESULTS: We discovered that TAK-981 downregulated the expression of the currently undruggable MYC and effectively suppressed the growth of MYC-expressing KRAS-mutant cancers across different tissue types. Moreover, TAK-981-resistant cells were sensitized to SUMOylation inhibition via MYC-overexpression. TAK-981 induced proteasomal degradation of MYC by altering the balance between SUMOylation and ubiquitination and promoting the binding of MYC and Fbxw7, a key factor in the ubiquitin-proteasome system. The efficacy of TAK-981 monotherapy in immunocompetent and immunodeficient mouse models using a mouse-derived CMT167 cell line was significant but modest. Since MAPK inhibition of the KRAS downstream pathway is crucial in KRAS-mutant cancer, we expected that co-inhibition of SUMOylation and MEK might be a good option. Surprisingly, combination treatment with TAK-981 and trametinib dramatically induced apoptosis in multiple cell lines and gene-engineered mouse-derived organoids. Moreover, combination therapy resulted in long-term tumor regression in mouse models using cell lines of different tissue types. Finally, we revealed that combination therapy complementally inhibited Rad51 and BRCA1 and accumulated DNA damage. CONCLUSIONS: We found that MYC downregulation occurred via SUMOylation inhibition in KRAS-mutant cancer cells. Our findings indicate that dual inhibition of SUMOylation and MEK may be a promising treatment for MYC-expressing KRAS-mutant cancers by enhancing DNA damage accumulation.

Upregulation of the long noncoding RNA GJA9-MYCBP and PVT1 is a potential diagnostic biomarker for acute lymphoblastic leukemia.

BACKGROUND: Acute lymphoblastic leukemia (ALL) is the most common type of blood cancer in children. Aberrant expression of long noncoding RNAs (lncRNAs) may set stages for ALL development. LncRNAs are emerging as a novel diagnostic and prognostic biomarker for ALL. Herein, we aimed to evaluate the expression of lncRNA GJA9-MYCBP and PVT1 in blood samples of ALL and healthy individuals. METHODS: As a case-control study, 40 pairs of ALL and healthy individual samples were used. The expression of MYC and each candidate lncRNA was measured using quantitative real-time PCR. Any possible association between the expression of putative noncoding RNAs and clinicopathological characteristics was also evaluated. RESULTS: LncRNA GJA9-MYCBP and PVT1 were significantly upregulated in ALL samples compared with healthy ones. Similarly, mRNA levels of MYC were increased in ALL samples than control ones. Receiver operating characteristic curve analysis indicated a satisfactory diagnostic efficacy (p-value <.0001), suggesting that lncRNA GJA9-MYCBP and PVT1 may serve as a diagnostic biomarker for ALL. Linear regression analysis unveiled positive correlations between the expression level of MYC and lncRNA GJA9-MYCBP and PVT1 in ALL patients (p-values <.01). CONCLUSIONS: In this study, we provided approval for the clinical diagnostic significance of lncRNA GJA9-MYCBP and PVT1that their upregulations may be a diagnostic biomarker for ALL.

[Clinicopathological characteristics of angioimmunoblastic T-cell lymphoma with B-cell proliferation or neoplasms].

Objective: To investigate the clinical, pathological and immunophenotypic features, and differential diagnosis of angioimmunoblastic T-cell lymphoma (AITL) with B-cell proliferation or neoplasms. Methods: Eight qualified cases were collected from the Department of Pathology, the First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China from January 2019 to July 2023. One case was diagnosed with AITL and diffuse large B-cell lymphoma (DLBCL) and the other seven cases were diagnosed with AITL and B-cell proliferation. Clinical characteristics and pathological morphology were summarized. Immunohistochemical analysis, fluorescence in situ hybridization and gene rearrangement detection were performed. Results: The patients' average age was 58 years. Five of them were male. Biopsies of the enlarged cervical lymph nodes showed structural destruction and exhibited various histologic patterns. Some cases revealed Burkitt-like morphology, a moderate tumor volume and slightly irregular nuclei. Some cases showed prominent nucleoli. High endothelial venules and expanded follicular dendritic cells were detected. Tumor cells derived from T-follicular helper (TFH) cells were positive for two or more TFH biomarkers. Nodular or diffuse patchy proliferation of B cells was noted around the tumor tissue, which was initially considered as B-cell lymphoma. All of the 8 cases showed monoclonal rearrangements of the T-cell receptor genes while 5 of them also showed clonal rearrangements of the Ig genes. Seven of the 8 cases were subject to the detection of C-MYC gene breakage and were all negative. EBV-positive cells were seen in 6 cases. Neoplastic B cells were positive for C-MYC (>40%), while proliferative B cells were negative for C-MYC (<40%). Conclusions: The histological morphology of AITL with B-cell proliferation or lymphoma may be different from AITL. An integrated analysis, incorporating clinical, morphologic, immunophenotypic, and molecular assessment, helps reach an accurate diagnosis. This group of cases demonstrated the clinical and pathological characteristics of AITL accompanied by B-cell proliferation and B-cell lymphoma. The findings suggest that C-MYC maybe a feasible indicator for distinguishing B-cell proliferation from B-cell lymphoma, and provide a simple and feasible immunohistochemical marker for the diagnosis and research of composite lymphoma.

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.

Mechanical stress during confined migration causes aberrant mitoses and c-MYC amplification.

Confined cell migration hampers genome integrity and activates the ATR and ATM mechano-transduction pathways. We investigated whether the mechanical stress generated by metastatic interstitial migration contributes to the enhanced chromosomal instability observed in metastatic tumor cells. We employed live cell imaging, micro-fluidic approaches, and scRNA-seq to follow the fate of tumor cells experiencing confined migration. We found that, despite functional ATR, ATM, and spindle assembly checkpoint (SAC) pathways, tumor cells dividing across constriction frequently exhibited altered spindle pole organization, chromosome mis-segregations, micronuclei formation, chromosome fragility, high gene copy number variation, and transcriptional de-regulation and up-regulation of c-MYC oncogenic transcriptional signature via c-MYC locus amplifications. In vivo tumor settings showed that malignant cells populating metastatic foci or infiltrating the interstitial stroma gave rise to cells expressing high levels of c-MYC. Altogether, our data suggest that mechanical stress during metastatic migration contributes to override the checkpoint controls and boosts genotoxic and oncogenic events. Our findings may explain why cancer aneuploidy often does not correlate with mutations in SAC genes and why c-MYC amplification is strongly linked to metastatic tumors.

Depletion of lipid storage droplet-1 delays endoreplication progression and induces cell death in Drosophila salivary gland.

Perilipins are evolutionarily conserved from insects to mammals. Drosophila lipid storage droplet-1 (LSD-1) is a lipid storage droplet membrane surface-binding protein family member and a counterpart to mammalian perilipin 1 and is known to play a role in lipolysis. However, the function of LSD-1 during specific tissue development remains under investigation. This study demonstrated the role of LSD-1 in salivary gland development. Knockdown of Lsd-1 in the salivary gland was established using the GAL4/UAS system. The third-instar larvae of knockdown flies had small salivary glands containing cells with smaller nuclei. The null mutant Drosophila also showed the same phenotype. The depletion of LSD-1 expression induced a delay of endoreplication due to decreasing CycE expression and increasing DNA damage. Lsd-1 genetically interacted with Myc in the third-instar larvae. These results demonstrate that LSD-1 is involved in cell cycle and cell death programs in the salivary gland, providing novel insight into the effects of LSD-1 in regulating salivary gland development and the interaction between LSD-1 and Myc.

Extrachromosomal circular DNA promotes prostate cancer progression through the FAM84B/CDKN1B/MYC/WWP1 axis.

BACKGROUND: Extrachromosomal circular DNA (eccDNA), a kind of circular DNA that originates from chromosomes, carries complete gene information, particularly the oncogenic genes. This study aimed to examine the contributions of FAM84B induced by eccDNA to prostate cancer (PCa) development and the biomolecules involved. METHODS: The presence of eccDNA in PCa cells and the FAM84B transcripts that eccDNA carries were verified by outward and inward PCR. The effect of inhibition of eccDNA synthesis on FAM84B expression in PCa cells was analyzed by knocking down Lig3. The impact of FAM84B on the growth and metastases of PCa cells was verified by Cell Counting Kit-8 (CCK8), EdU, transwell assays, and a xenograft mouse model. Chromatin immunoprecipitation quantitative PCR (ChIP-qPCR) and dual-luciferase reporter assays were carried out to examine the effect of FAM84B/MYC on WWP1 transcription, and a co-immunoprecipitation (Co-IP) assay was conducted to verify the modification of CDKN1B by WWP1. The function of this molecular axis in PCa was explored by rescue assays. RESULTS: The inhibited eccDNA synthesis significantly downregulated FAM84B in PCa cells, thereby attenuating the growth and metastasis of PCa. FAM84B promoted the transcription of WWP1 by MYC by activating the expression of MYC coterminous with the 8q24.21 gene desert in a beta catenin-dependent approach. WWP1 transcription promoted by MYC facilitated the ubiquitination and degradation of CDKN1B protein and inversely attenuated the repressive effect of CDKN1B on MYC expression. Exogenous overexpression of CDKN1B blocked FAM84B-activated MYC/WWP1 expression, thereby inhibiting PCa progression. CONCLUSIONS: FAM84B promoted by eccDNA mediates degradation of CDKN1B via MYC/WWP1, thereby accelerating PCa progression.

C-MYC-activated lncRNA SNHG20 accelerates the proliferation of diffuse large B cell lymphoma via USP14-mediated deubiquitination of ß-catenin.

BACKGROUND: Long noncoding RNAs (lncRNAs) are implicated in the initiation and progression of diffuse large B-cell lymphoma (DLBCL). Small nucleolar RNA host gene 20 (SNHG20) has been recognized as a critical lncRNA in multiple human cancers. However, the role of SNHG20 and its underlying mechanism in DLBCL are still unclear. METHODS: The expression levels of SNHG20, c-MYC, ß-catenin, and ubiquitin-specific peptidase 14 (USP14) were measured by reverse transcription-quantitative polymerase chain reaction (RT‒qPCR) and immunoblotting. Cell Counting Kit-8 (CCK-8), 5-Ethynyl-2'-deoxyuridine (EdU) incorporation, and flow cytometry assays were used to assess the proliferation and apoptosis of DLBCL cells. The transcriptional regulation of SNHG20 by c-MYC was confirmed by a luciferase reporter assay and RNA immunoprecipitation. The interaction between USP14 and ß-catenin was demonstrated using coimmunoprecipitation. A subcutaneous xenograft model was constructed to determine the role of SNHG20 in vivo. RESULTS: In the present study, we found that SNHG20 expression was upregulated in DLBCL cell lines and tissues compared to their normal counterparts. SNHG20 knockdown prominently reduced the proliferation and induced the apoptosis of U2932 and OCI-LY3 cells. However, SNHG20 overexpression increased the proliferation and apoptosis resistance of DLBCL cells. Mechanistically, the expression of SNHG20 was positively regulated by c-MYC in DLBCL cells. C-MYC directly bound to the promoter of SNHG20 to activate its transcription. SNHG20 was expressed mainly in the cytosol in DLBCL cells. SNHG20 silencing did not impact USP14 expression but markedly decreased the level of ß-catenin, the substrate of USP14, in DLBCL cells. USP14 overexpression increased the ß-catenin level, and this increase was attenuated by SNHG20 knockdown. Treatment with the proteasome inhibitor MG132 abolished SNHG20 knockdown-induced ß-catenin downregulation. Moreover, SNHG20 silencing reduced the half-life but increased the ubiquitination of ß-catenin in DLBCL cells. SNHG20 knockdown weakened the interaction between both endogenous and exogenous USP14 and ß-catenin. In turn, SNHG20 overexpression increased the c-MYC level, and this increase was attenuated by ß-catenin knockdown. Importantly, ß-catenin knockdown attenuated the SNHG20-mediated increase in DLBCL cell proliferation in vitro and tumour growth in vivo. CONCLUSIONS: Taken together, our results suggested that c-MYC-activated SNHG20 accelerated the proliferation and increased the apoptosis resistance of DLBCL cells via USP14-mediated deubiquitination of ß-catenin. The c-MYC/SNHG20 positive feedback loop may be a new target for anti-DLBCL treatment.

A microdeletion event at 19q13.43 in IDH-mutant astrocytomas is strongly correlated with MYC overexpression.

MYC dysregulation is pivotal in the onset and progression of IDH-mutant gliomas, mostly driven by copy-number alterations, regulatory element alterations, or epigenetic changes. Our pilot analysis uncovered instances of relative MYC overexpression without alterations in the proximal MYC network (PMN), prompting a deeper investigation into potential novel oncogenic mechanisms. Analysing comprehensive genomics profiles of 236 "IDH-mutant 1p/19q non-co-deleted" lower-grade gliomas from The Cancer Genome Atlas, we identified somatic genomic alterations within the PMN. In tumours without PMN-alterations but with MYC-overexpression, genes correlated with MYC-overexpression were identified. Our analyses yielded that 86/236 of astrocytomas exhibited no PMN-alterations, a subset of 21/86 displaying relative MYC overexpression. Within this subset, we discovered 42 genes inversely correlated with relative MYC expression, all on 19q. Further analysis pinpointed a minimal common region at 19q13.43, encompassing 15 genes. The inverse correlations of these 15 genes with relative MYC overexpression were re-confirmed using independent scRNAseq data. Further, the micro-deleted astrocytoma subset displayed significantly higher genomic instability compared to WT cases, but lower instability compared to PMN-hit cases. This newly identified 19q micro-deletion represents a potential novel mechanism underlying MYC dysregulation in astrocytomas. Given the prominence of 19q loss in IDH-mutant gliomas, our findings bear significant implications for understanding gliomagenesis.

Gene expression profiling of p53 and c-myc in HTLV-1 positive blood donors in Congo.

OBJECTIVES: The HTLV-1 infection persists for life, remaining as asymptomatic viral reservoirs in most patients, ensuring the chain of transmission, but around 4% develop adult T-cell leukemia/lymphoma (ATLL). HTLV-1 is an oncogenic retrovirus that transforms CD4+ T lymphocytes and deregulates the lymphoproliferative pathways that contribute to the development of ATLL. To achieve cell transformation, most oncogenic retroviruses use proto-oncogene capture transduction, with proviral integration disrupting the expression of tumor suppressors or proto-oncogenes. THE AIM: We conducted this study on the prevalence of HTLV-1 infection in blood donors to expand the HTLV-1 database, assess the risk of transmission via blood products, as well as evaluate the risk of persistent infection or development of neoplastic diseases in HTLV-1 carriers. MATERIALS AND METHODS: This is a cross-sectional study of blood donors of all categories. For this study, 265 blood donors were recruited at the Centre National de Transfusion Sanguine in Brazzaville. After testing for HTLV-1 antibodies by ELISA, proviral DNA was extracted from all ELISA-positive samples for detection by nested PCR, followed by RT qPCR using specific primers p53 and c-myc for gene expression. RESULTS: 20/265 were positive for anti-HTLV-1 antibody, 5 donors were positive for proviral DNA. The prevalence of HTLV-1 was 1.8%. All HTLV-1-positive donors were male (1.8%), with a positive correlation (p = 0.05); the 1.1% of positive donors were regular, with the majority aged between 31 and 45 years (1.5%), and concubine donors were the most frequent (1.1%). All samples showed normal expression of the p53 and c-myc genes. CONCLUSION: The prevalence, though low, remains a serious problem. No abnormal p53 or c-myc gene expression was detected in HTLV-1-positive donors, which could mean that none of the T lymphocytes in these donors had been transformed by HTLV-1.