Cell Growth Arrest Research Articles

EGFR inhibition augments the therapeutic efficacy of the NAT10 inhibitor Remodelin in Colorectal cancer.

Colorectal cancer (CRC) is the second leading cause of cancer-related death worldwide, and treatment options for advanced CRC are limited. The regulatory mechanisms of aberrant NAT10-mediated N4-acetylcytidine (ac4C) modifications in cancer progression remains poorly understood. Consequently, an integrated transcriptomic analysis is necessary to fully elucidate the role of NAT10-mediated ac4C modifications in CRC progression. NAT10 expression levels were analyzed in CRC samples and compared with those in corresponding normal tissues. The potential mechanisms of NAT10 in CRC were investigated using RNA sequencing, RNA immunoprecipitation sequencing, and acetylated RNA immunoprecipitation sequencing. Additional in vivo and in vitro experiments, including CCK-8 assays, colony formation and mouse xenograft models, were conducted to explore the biological role of NAT10-mediated ac4C modifications. We also evaluated and optimized a potential treatment strategy targeting NAT10. We found that NAT10 is highly expressed in CRC samples and plays a pro-oncogenic role. NAT10 knockdown led to PI3K-AKT pathway inactivation, thereby inhibiting CRC progression. However, treatment with the NAT10 inhibitor Remodelin induced only a limited and reversible growth arrest in CRC cells. Further epigenetic and transcriptomic analysis revealed that NAT10 enhances the stability of ERRFI1 mRNA by binding to its coding sequence region in an ac4C-dependent manner. NAT10 knockdown decreased ERRFI1 expression, which subsequently activated the EGFR pathway and counteracted the inhibitory effects on CRC. Based on these findings, we demonstrated that dual inhibition of NAT10 and EGFR using Remodelin and the EGFR-specific monoclonal antibody cetuximab resulted in improved therapeutic efficacy compared to either drug alone. Moreover, we observed that 5-Fluorouracil promoted the interaction between NAT10 and UBR5, which increased the ubiquitin-mediated degradation of NAT10, leading to ERRFI1 downregulation and EGFR reactivation. Triple therapy with Remodelin, cetuximab, and 5-Fluorouracil enhanced tumor regression in xenograft mouse models of CRC with wild-type KRAS, NRAS and BRAF. Our study elucidated the mechanism underlying 5-Fu-induced NAT10 downregulation, revealing that NAT10 inhibition destabilizes ERRFI1 mRNA through ac4C modifications, subsequently resulting in EGFR reactivation. A triple therapy regimen of Remodelin, cetuximab, and 5-Fu showed potential as a treatment strategy for CRC with wild-type KRAS, NRAS and BRAF.

3-Hydroxyanthranic acid inhibits growth of oral squamous carcinoma cells through growth arrest and DNA damage inducible alpha.

The specific role of 3-hydroxyanthranilic acid(3-HAA) in oral squamous cell carcinoma (OSCC) remains unclear. This study investigated the roles of 3-HAA in OSCC and the underlying mechanism. The effects of 3-HAA on OSCC were examined using CCK-8, colony formation, EdU incorporation assays and xenograft mouse model. The underlying mechanisms were investigated with RNA-seq, apoptosis array and cell cycle array. Short hairpin RNAs (shRNAs) were used to knockdown the expression of growth arrest and DNA damage inducible alpha (GADD45A) in OSCC cells. CCK-8 and xenograft mouse model were employed to elucidate the role of GADD45A. The binding sites between GADD45A and Yin Yang 1(YY1) were determined using luciferase reporter assay. 3-HAA was selectively down-regulated in OSCC patients and the decreasing level intensified with pathological progression. Higher expression of kynurenine 3-monooxygenase (KMO) and kynureninase (KYNU), which can increase the content of 3-HAA, was associated with poorer prognosis of OSCC patients. Exogenous 3-HAA hampered growth of OSCC cells both in vitro and in vivo. 3-HAA induced growth arrest, G2/M-phase arrest, and apoptosis of OSCC cells. RNA-seq indicated that 3-HAA significantly increased GADD45A expression. 3-HAA promoted transcription of GADD45A by transcription factor YY1. Knockdown of GADD45A significantly reversed 3-HAA-induced growth inhibition of OSCC cells in vivo and in vitro. 3-HAA induced apoptosis and cell cycle arrest of OSCC cells via GADD45A, indicating that 3-HAA and GADD45A are potential therapeutic targets for OSCC.

Phytosomes Loaded with Mastoparan-M Represent a Novel Strategy for Breast Cancer Treatment.

Mastoparan-M (Mast-M) has cytotoxic effects on various tumor cells in vitro, including liver cancer and colorectal cancer. However, the anti-tumor mechanism of Mast-M remains unclear and its potential for anti-tumor therapy has not been investigated. Herein, we aimed to develop a novel phytosome formulation loaded with Mast-M and evaluate its efficacy against breast cancer both in vitro and in vivo. Furthermore, we investigated the underlying anti-tumor mechanisms of Mast-M. The synthesis of Phy-Mast-M involved a co-solvent technique, followed by solvent evaporation. Its anti-tumor mechanism was investigated using CCK-8, clone formation, and apoptosis assays. Subsequently, the biodistribution and anti-tumor efficacy of Phy-Mast-M were assessed in vivo using the 4T1 tumor-bearing mouse model. Finally, the safety of Phy-Mast-M was evaluated in vivo. The prepared Phy-Mast-M demonstrated an exceptional monodisperse size distribution (125.67 ± 45.79 nm), and exhibited excellent stability under different physiological conditions. Phy-Mast-M could inhibit 4T1 cells growth through multiple channels, including arresting cell growth cycle and disturbing mitochondrial membrane integrity. Phy-Mast-M proved significantly higher accumulation at tumor sites in a tumor-bearing mouse model as compared to free Mast-M. Moreover, in vivo anti-tumor studies demonstrated that Phy-Mast-M exhibited superior curative inhibitory effects on tumor growth and favorable biocompatibility. Phy-Mast-M demonstrates significant anti-tumor activity both in vitro and in vivo. Moreover, its potential for clinical translation suggests promising prospects for cancer therapy, offering more drug options for breast cancer patients.

Investigating the effects of stereotactic body radiation therapy on pancreatic tumor hypoxia and microvasculature in an orthotopic mouse model using intravital fluorescence microscopy

Despite decades of improvements in cytotoxic therapy, the current standard of care for locally advanced pancreatic cancer (LAPC) provides, on average, only a few months of survival benefit. Stereotactic Body Radiation Therapy (SBRT), a technique that accurately delivers high doses of radiation to tumors in fewer fractions, has emerged as a promising therapy to improve local control of LAPC; however, its effects on the tumor microenvironment and hypoxia remain poorly understood. To explore how SBRT affects pancreatic tumors, we combined an orthotopic mouse model of pancreatic cancer with an intravital microscopy platform to visualize changes to the in vivo tumor microenvironment in real-time. Mice received SBRT (5 × 8 Gy) or were left untreated, and were imaged before and 1, 4, 7, and 14 days after treatment (n = 7/group). A fluorescent human pancreatic cancer cell line (BxPC3-DsRed) engineered to express GFP under hypoxic conditions (driven by hypoxia-inducible factor, HIF) was used to monitor tumor hypoxia. Immunohistochemical staining was also performed on tissues to validate in vivo data. Our findings demonstrate a persistent decrease in pancreatic tumor hypoxia as early as one day after SBRT. This coincided with a decrease in both tumor cell proliferation and cell density in the SBRT group. Reduced demand for oxygen after SBRT (due to cell death and growth arrest from treatment) significantly contributed to reoxygenation of the pancreatic TME. Understanding how this reoxygenation phenomenon occurs in a dose-dependent manner will help improve dosing and fractionation schemes for clinical SBRT.

Antimicrobial photodynamic inactivation of Pseudomonas aeruginosa persister cells and biofilms.

Pseudomonas aeruginosa is a hard-to-treat human pathogen for which new antimicrobial agents are urgently needed. P. aeruginosa is known for forming biofilms, a complex aggregate of bacteria embedded in a self-generated protective matrix that enhance its resistance to antibiotics and the immune system. Within the biofilm, persister cells, sub-populations of slow-growing or growth-arrested cells, are associated with recalcitrance of infections and antibiotic treatment failure. Here, we investigate the influence of the anionic photosensitiser chlorophyllin (CHL)1 exposed to red light alone and in combination with an activator of the mechanosensitive channels butylparaben (BP) on P. aeruginosa growing cells, persister cells, and biofilms. Antimicrobial susceptibility tests were performed using the broth microdilution checkerboard method. Serine hydroxamate (SHX) was used for the induction of persister cells. Under illumination, a combination of CHL (250 µg/ml) and BP (97.12 µg/ml) reduced the number of growing cells and persister cells by 2.2±0.46 log10 and 1.7±0.15 log10, respectively after 30 min of exposure at 79 J/cm2. A higher concentration of BP (194.23 µg/ml) or longer exposure time (60 min at 158 J/cm2) effectively eliminated approximately ≥99.99 % of growing and persister cells. Visual evidence from confocal and TEM images illustrates the influence of CHL and red light, which intensifies when combined with BP. Nevertheless, the addition of BP did not enhance the efficacy of CHL against biofilms; CHL (500 µg/ml) reduced biofilm viability by 2.6 log10 at 791 J/cm2. No toxicity has been observed in darkness. This study highlights the potential antimicrobial effect of CHL against P. aeruginosa.

The aberrantly activated AURKB supports and complements the function of AURKA in CALR mutated cells through regulating the cell growth and differentiation.

Aurora kinase B (AURKB) was reported to assist Aurora kinase A (AURKA) to regulate cellular mitosis. AURKA has been found activated in myeloproliferative neoplasms (MPNs) patients with CALR gene mutation, however, it's unclear whether AURKB displays a compensatory function of AURKA in regulation of CALR mutant cell growth and differentiation. Here, we found that AURKB, similar with AURKA, was aberrantly activated in CALR mutant patients, and displayed a more tolerance to the aurora kinase inhibitor. Inhibition of AURKA decreased cell growth and colony formation, induced cell differentiation and apoptosis, while, this inhibitive degree was further enhanced when AURKB was blocked by incremental inhibitor. Transcriptomic analyses revealed a more significant gene enrichment in cells with knockdown of AURKB than that of AURKA, mainly reflecting in oxidative phosphorylation, mitosis, proliferation and apoptosis signaling pathway. Moreover, downregulation of AURKB enhanced cell growth arrest and apoptosis more obviously than that of AURKA, and additionally promoted cell differentiation and metabolism-oxygen consumption rate (OCR). Otherwise, overexpression of AURKA or AURKB facilitated the cell proliferation of CALR mutant cells, and made cells more sensitive to the aurora kinase inhibitor. These results suggest that activated AURKB not only supports the functions of AURKA in promoting the growth of CALR mutated cells, but also has impeded the differentiation of these cells.

Urinary GADD45G Protein Excretion Is Associated with IgA Nephropathy Progression.

Background: Growth arrest and DNA damage 45G (GADD45G) is a family of proteins involved in DNA damage response and cell growth arrest. In this study, we show evidence that urinary GADD45G protein is associated with the progression of IgA nephropathy. Methods: Patients diagnosed with IgA nephropathy without reversible acute kidney injury at study initiation and with at least one subsequent serum creatinine (SCr) measurement were included. A 50% or greater increase in SCr level was used as an endpoint for the deterioration of renal function. Enzyme-linked immunosorbent assay (ELISA) was performed using a Human GADD45G ELISA kit. Renal biopsy tissues were stained with a monoclonal mouse anti-GADD45G antibody. Results: Forty-five patients whose renal biopsy revealed IgA nephropathy were enrolled. Urinary GADD45G and urinary protein concentrations were 1.26 [0.69-2.20] μg/g creatinine and 0.65 [0.24-1.60] g/g creatinine, respectively. Urinary GADD45G showed significant positive correlations with SCr-slopes and urinary protein. The SCr-slope of the highest tertile group of urinary GADD45G (above 1.95 μg/g creatinine) was significantly higher than that of the lowest tertile group (below 0.90 μg/g). Univariate Cox regression analysis showed that urinary GADD45G was significantly associated with deterioration of renal function. A Kaplan-Meier test showed a significant difference in event-free survival for deterioration of renal function between the highest urinary GADD45G tertile group and other tertile groups. The area under the receiver operating characteristics (ROC) curve indicated urinary GADD45G had a good performance in predicting renal outcome (cut-off point 1.67 μg/g, positive predictive value 36.8%, negative predictive value 100%). Immunohistochemistry showed that GADD45G was expressed across all pathologic grades of IgA nephropathy and mainly detected in the cytoplasm of renal tubules, whereas no staining was noted in normal tissues. Conclusions: Urinary GADD45G excretion was significantly associated with kidney disease progression in patients with IgA nephropathy.

Antiviral signaling of a type III CRISPR-associated deaminase.

Prokaryotes have evolved diverse defense strategies against viral infection, such as foreign nucleic acid degradation by CRISPR-Cas systems and DNA/RNA synthesis inhibition via nucleotide pool depletion. Here, we report an antiviral mechanism of type III CRISPR-Cas-regulated ATP depletion, where ATP is converted into ITP by CRISPR-Cas-associated adenosine deaminase (CAAD) upon activation by either cA4 or cA6, followed by hydrolysis into IMP by Nudix hydrolase, ultimately resulting in cell growth arrest. The cryo-electron microscopy structures of CAAD in its apo and activated forms, together with biochemical evidence, revealed how cA4/cA6 binds to the CARF domain and abrogates CAAD autoinhibition, inducing substantial conformational changes that reshape the structure of CAAD and induce its deaminase activity. Our results reveal the mechanism of a CRISPR-Cas-regulated ATP depletion antiviral strategy.

TNIP1 Knockdown Induces the Growth Arrest and Apoptosis of Breast Cancer Cells by Activating the NF-κB Pathway

TNIP1 Knockdown Induces the Growth Arrest and Apoptosis of Breast Cancer Cells by Activating the NF-κB Pathway

PTPMT1 inhibition induces apoptosis and growth arrest of human SCLC cells by disrupting mitochondrial metabolism.

Many cancer cells exhibit aberrant metabolic reprogramming through abnormal mitochondrial respiration. Protein tyrosine phosphatase mitochondrial 1 (PTPMT1) is a protein tyrosine phosphatase localized to the mitochondria and linked to mitochondrial respiration. However, the expression and role of PTPMT1 in regulating the biological characteristics of small cell lung cancer (SCLC) has not yet been explored. The aim of this study was to evaluate the role of PTPMT1 on SCLC cell survival and mitochondrial function. SCLC and adjacent normal tissues were obtained from surgery. The expression level of PTPMT1 in the SCLC tissues and cell lines was determined by immunohistochemical staining, western blot, and quantitative real-time polymerase chain reaction (qRT-PCR). PTPMT1 knockdown was induced by lentivirus-mediated short-hairpin RNA (shRNA) transduction and PTPMT1 inhibition (alexidine dihydrochloride). The biological characteristics of the cells were measured by cell counting kit 8 (CCK-8), colony formation assay, and cell migration assay. The mitochondrial function of the cells was measured by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide (JC-1) staining. The H69 cells were treated with alexidine dihydrochloride, after which transcriptome sequencing and an untargeted metabolomic analysis were performed. The transcriptome differentially expressed genes were measured by qRT-PCR. PTPMT1 was upregulated in the SCLC tissues compared to the adjacent normal tissues. PTPMT1 inhibition by lentiviral shRNA transduction or specific inhibition resulted in significant growth arrest and apoptosis. The transcriptome sequencing analysis revealed that pathways related to the respiration chain and mitochondrial member protein were disrupted. Several mitochondrial metabolism-related genes, such as FGF21, GDF-15, APLN, and MT-DN6, were dysregulated. Further, PTPMT1 inhibition was found to downregulate Glut expression and disturb mitochondrial function. PTPMT1 was shown to play a critical role in the survival and growth of SCLC cells, and may become a potential therapeutic target.

In vitro studies of the combination between berberine chloride and a Copper(II) complex against Triple negative breast cancer

In this study, the copper(II) complex [Cu(chromoneTSC)Cl2]•0·.5H2O•0.0625C2H5OH (where chromoneTSC = (E)-N-Ethyl-2-((4-oxo-4H-chromen-3-yl)methylene)-hydrazinecarbothioamide) was synthesized and characterized; then used to carry out in vitro studies in combination with berberine chloride (BBC). The ligand and complex were characterized by elemental analysis, FTIR and NMR (1H and 13C) spectroscopy, and conductivity measurements. The cytotoxic effect was analyzed by using the CCK-8 viability assay in cancer MDA-MB-231 VIM RFP and non-cancer MCF-10A cell lines. The IC50 values for the complex and BBC were 21.2 ± 1.6 and 48.3 ± 2.4 μM, respectively at 24 h incubation, while the IC50 value of the combination treatment was 9.3 ± 1.5 in cancer cells. The co-treatment group significantly increased the number of cells in G2 phase, indicating the growth arrest of cancer cells. Moreover, the combination group showed induction of both intrinsic and extrinsic apoptotic pathways. There was also a study on the effect of the combination treatment on receptor-interacting serine/threonine-protein kinase 3 (RIPK3) and mixed lineage kinase domain-like pseudokinase (MLKL) as biomarkers of necroptosis. The results showed activation of necroptosis after treatment with the combination of the copper complex and BBC via the activation of RIPK3–MLKL pathway.

Fungal lectins show differential antiproliferative activity against cancer cell lines.

Glycosylation patterns represent an important signature of cancer cells that can be decoded by glycan-binding proteins, i.e., lectins. Fungal lectins have unique properties and diverse structural and glycan-recognition features. In this study, the bioactivities of 22 fungal proteins against nine cancer cell lines were analyzed, and cell phenotypes were assessed with live cell imaging providing mechanistic insights. Eight fungal lectins showed antiproliferative activity, which depended on glycan binding and led to different downstream effects. The β-galactoside-binding chimerolectins Marasmius oreades agglutinin (MOA) and Laetiporus sulphureus lectin (LSL) showed indiscriminate antiproliferative activities with different modes of action, whereas the non-chimeric β-galactoside-binding lectin Agrocybe aegerita galectin (AAG) showed differential antiproliferative activity. Other β-galactoside-binding lectins exerted no effects. Fucose-binding lectins showed differential and strong antiproliferative activities, of which Aleuria aurantia lectin (AAL) exerted the strongest effects. Weaker anddifferential antiproliferative activities were observed with the Galβ1-3GalNAc-binding actinoporin-like lectins Xerocomus chrysenteron lectin (XCL), Sordaria macrospora transcript associated with perithecial development (TAP1), and Agaricus bisporus lectin (ABL). The different downstream effects of lectins, likely influenced by the targeted glycoligands, show that fungal lectins are valuable tools for identifying new therapeutic targets that can induce cancer cell death or growth arrest via different mechanisms.

CARF regulates the alternative splicing and piwi/piRNA complexes during mouse spermatogenesis through PABPC1.

ADP-ribosylation factor collaborator (CARF), which is also known as CDKN2AIP, was first recognized as an ADP-ribosylation factor-interacting protein that participates in the activation of the ARF-p53-p21 (WAF1) signaling pathway under different conditions, such as oxidative and oncogenic stresses. The activation of this pathway often leads to cell growth arrest and apoptosis as well as senescence. Previous studies revealed that CARF, an RNA-binding protein, is critical for maintaining stem cell pluripotency and somatic differentiation. Nevertheless, its involvement in spermatogenesis has not been well examined. In this study, we show that male mice deficient in Carf expression present impaired spermatogenesis and fertility. IP-MS and RNA-seq analyses reveal that CARF/ Carf interacts with multiple key splicing factors, such as PABPC1, and directly targets 356 different types of mRNAs in spermatocytes. Carf-associated mRNAs display aberrant splicing patterns when Carf expression is deficient. In addition, our results demonstrate that PIWIL1 expression and localization are altered in the Carf -/ - mouse model through the downregulation of PABPC1, which further affects the ratio of pachytene-piRNA. Our study suggests that CARF is critical for regulating alternative splicing in mammalian spermatogenesis and determining infertility in male mice.

Dual specific STAT3/5 degraders effectively block acute myeloid leukemia and natural killer/T cell lymphoma.

The transcription factors STAT3, STAT5A, and STAT5B steer hematopoiesis and immunity, but their enhanced expression and activation promote acute myeloid leukemia (AML) or natural killer/T cell lymphoma (NKCL). Current therapeutic strategies focus on blocking upstream tyrosine kinases to inhibit STAT3/5, but these kinase blockers are not selective against STAT3/5 activation and frequent resistance causes relapse, emphasizing the need for targeted drugs. We evaluated the efficacy of JPX-0700 and JPX-0750 as dual STAT3/5 binding inhibitors promoting protein degradation. JPX-0700/-0750 decreased the mRNA and protein levels of STAT3/5 targets involved in cancer survival, metabolism, and cell cycle progression, exhibiting nanomolar to low micromolar efficacy. They induced cell death and growth arrest in both AML/NKCL cell lines and primary AML patient blasts. We found that both AML/NKCL cells hijack STAT3/5 signaling through either upstream activating mutations in kinases, activating mutations in STAT3, mutational loss of negative STAT regulators, or genetic gains in anti-apoptotic, pro-proliferative, or epigenetic-modifying STAT3/5 targets. This emphasizes a vicious cycle for proliferation and survival through STAT3/5. Both JPX-0700/-0750 treatment reduced leukemic cell growth in human AML or NKCL xenograft mouse models significantly, being well tolerated by mice. Synergistic cell death was induced upon combinatorial use with approved chemotherapeutics in AML/NKCL cells.

Analysis of cell lysis for improved understanding between the shake tube and stirred tank reactor perfusion CHO cell cultures.

Shake tubes (ST) are widely employed to assist the development of the stirred tank reactor (STR) perfusion cell culture. However, cell lysis may be frequently underrestimated and lead to culture performance discrepency between these systems, rendering the ST model ineffective in designing the STR perfusion cultures. In this study, perfusion culture performance bewteen the STR and ST was investigated under various conditions with the analysis of cell lysis. Comparable performance was observed bewteen the two systems at low perfusion rates ( ≤1.0 VVD), except that the specific productivity ( ) of the STR was decreased at =0.5 VVD, which was related to product degradation by cell lysis. In contrast, significant differences in cell maintenance, metabolism, and were found at =2.0 VVD. By the analysis of the authentic cell growth and death kinetics, it was found that cell growth arrest, potentially due to the limited availability of oxygen, led to the stable cell maintenance at VCD≈90 × 106 cells/ml and altered cellular metabolism for the ST, while the continuous decline of VCD and in the STR were related to excessive cell death, subsequently ascribed to the harmful hydrodynamic stress conditions. We further demonstrated that cell lysis accounted for 57.62-76.29% of the total generated biomass in both the reactors and significantly impacted the estimation of process descriptors crucial for understanding the true cellular states. With cell lysis in sight, cell performance can therefore be accurately described and this knowledge can be further leveraged to expedite process development for the perfusion cell culture processes.

Effect of gedunin on cell proliferation and apoptosis in skin melanoma cells A431 via the PI3K/JNK signaling pathway.

Melanoma is an aggressive skin malignancy with rapid metastasis and high morbidity. Gedunin (GN) is a tetranortriterpenoid belonging to the Meliaceae family, described for its anticancer, antiproliferative and apoptotic properties. In the present study, we investigated the effect of GN on A431 melanoma cell proliferation and apoptosis. The inflammatory proteins (tumor necrosis factor alpha (TNF-α), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), cycloxygenase 2 (COX-2), inducible nitric oxide synthase (iNOS), and interleukin 6 (IL-6)) apoptosis-related proteins, such as Bax, Bcl-2 and caspase-3, and alterations in the PI3K/JNK and p38 pathways in A431 cells after GN treatment were examined. The cytotoxicity assay and cell apoptosis of GN activity on A431 cells were assessed using MTT assay, acridine orange/ethidium bromide (AO/EB), DAPI (4',6-diamidino-2-phenylindole), propidium iodide (PI), enzyme-linked immunosorbent assay (ELISA), reverse transcription polymerase chain reaction (RT-PCR) and western blot analyses. The findings demonstrated that GN (10 and 15 μM/mL) inhibits the growth of melanoma cells, triggers apoptosis by enhancing Bax and caspase, and reduces Bcl-2, cyclin-D1, c-myc, and survivin in a concentration-reliant manner. Additionally, GN attenuated the protein expression of inflammatory proteins (TNF-α, NF-κB, COX-2, iNOS, and IL-6) and the cell proliferative PI3K/JNK/p38 signaling pathway. Due to the imbalance in the Bax/Bcl-2 ratio, apoptosis is promoted, and the caspase cascade and Cyt-c are activated. This led us to conclude that GN treatment inhibited Bcl-2, cyclin-D1, c-myc, and survivin activity through the TNF-α/NF-κB and PI3K/JNK/p38 signaling pathways, further preventing the proliferation and stimulation of apoptosis, which contributes to growth arrest in melanoma cells. Gedunin has been shown to promote melanoma cell death in vitro, suggesting that it could be used as a future treatment for malignant melanoma. Our findings suggested that GN might be applied as a preventative measure in the management of skin melanoma cells.

DDDR-39. PI3 KINASE AND CHECKPOINT INHIBITION: A POTENTIALLY NOVEL THERAPEUTIC STRATEGY FOR GLIOBLASTOMA (GBM)

Abstract Glioblastoma is the most common and aggressive malignant brain tumor with a median survival of less than 2 years, highlighting the need for more effective therapeutics. Dual pathway synergism between PI3K inhibitors and check-point inhibitors is a promising therapeutic avenue that has not been explored. Based on this possibility, we hypothesized that the combination of PI3K and checkpoint inhibitors will improve survival in our native glioblastoma mouse model. Treatment with GCT-007, a small molecule PI3K inhibitor, induces growth arrest of GBM cells that is accompanied by increases in the cell surface expression of molecules targeted by the immune system and immunotherapy drugs, including MHC Class II and PD-L1. Treatment of mouse GL261 and human U251 GBM cell lines with GCT-007 caused growth arrest, increased the cell surface expression of PD-L1 and MHC class II, and synergized with radiation to cause growth arrest and cell death. We compared GCT-007 to Paxalisib in our in vitro studies and observed that GCT-007 outperformed Paxalisib at increasing MHC class II and PD-L1 expression on the tumor cells at equivalent doses. We then performed in vivo animal studies using our native mouse GBM model. We treated mice orally with GCT-007 and observed a significantly prolonged survival compared to placebo. Mice treated with anti-PD1 resulted in a sexually dimorphic response consisting of prolonged remission of all female mice, now surviving beyond 1 year, but no improvement in the survival of male mice compared to placebo. Adding GCT-007 to anti-PD1 did not alter the prolonged remission outcome in female mice, it did result in prolonged remission of 25% of the male mice, now beyond 1 year. In conclusion, these results indicate that GCT-007 treatment alone improves survival in our native GBM mouse model and it may also improve the response to immune checkpoint inhibitor therapy in at least a fraction of GBM tumors. These data warrant further investigation as a potentially novel therapeutic approach to GBM.

Epstein-Barr Virus Latent Membrane Protein 1 Subverts IMPDH pathways to drive B-cell oncometabolism.

Altered metabolism is a hallmark of cancer, yet much remains to be learned about how EBV rewires host cell metabolism to support multiple malignancies. While the oncogene LMP1 is the only EBV-encoded gene that is sufficient to transform murine B-cells and rodent fibroblasts, knowledge has remained incomplete about how LMP1 alters host cell oncometabolism to aberrantly drive infected B-cell growth and survival. Likewise, it has remained unknown whether LMP1 expression creates metabolic vulnerabilities that can be targeted by small molecule approaches to trigger EBV-transformed B-cell programmed cell death. We therefore used metabolomic profiling to define how LMP1 signaling remodels the B-cell metabolome. We found that LMP1 upregulated purine nucleotide biosynthesis, likely to meet increased demand. Consequently, LMP1 expression sensitized Burkitt B-cells to growth arrest upon inosine monophosphate dehydrogenase blockade. Thus, while LMP1 itself may not be a therapeutic target, its signaling induces dependence on downstream druggable host cell nucleotide metabolism enzymes, suggesting rational therapeutic approaches.

CBX7 inhibitors affect H3K9 methyltransferase-regulated gene repression in leukemic cells

The epigenome of leukemic cells is dysregulated, and genes required for cell cycle arrest and differentiation may become repressed, which contributes to the accumulation of undifferentiated malignant blood cells.Here we show that the Polycomb group protein CBX7 can interact with H3K9 methyltransferases EHMT1/2 and SETDB1. We aimed to assess whether combined interfering with these H3K9 methyltransferases and CBX7 could derepress target genes and thereby induce growth arrest of leukemic cells. We found that pharmacological inhibition of CBX7 abolishes the interaction of CBX7 with EHMT1/2 and SETDB1 and, subsequently, reduces H3K9 methylation levels which reactivates target gene expression. Reversely, upon pharmacological inhibition of H3K9 methyltransferases, CBX7 can take over gene repression. Finally, we found that combined inhibition of CBX7 and EHMT1/2 or SETDB1 had additive effects on reducing cell growth and inducing differentiation. However, we did not detect changes in epigenetic modifications, nor target gene derepression, after combination treatment. In contrast, CBX7 inhibitors alone did affect both Polycomb-associated H2Aub-mediated gene repression as well as H3K9 methyltransferase activity. Therefore, we suggest that CBX7 is a promising therapeutic target in leukemia, as its inhibition can reactivate Polycomb and H3K9 methyltransferase target gene expression.

Bone marrow stromal cells enhance differentiation of acute myeloid leukemia induced by pyrimidine synthesis inhibitors.

Acute myeloid leukemia (AML) is a heterogeneous group of hematological malignancies characterized by differentiation arrest, high relapse rates, and poor survival. The bone marrow (BM) microenvironment is recognized as a critical mediator of drug resistance and a primary site responsible for AML relapse. Our previous study reported that 5-aminoimidazole-4-carboxamide ribonucleoside (AICAr) induces AML cell differentiation by inhibiting pyrimidine synthesis and activating Checkpoint kinase 1. Although the protective effect of BM stroma on leukemia cells in response to cytotoxic drugs is well-documented, its effect on AML differentiation remains less explored. In this study, we investigated the impact of stromal cell lines and primary mesenchymal stromal cells (MSCs) on AML cell line differentiation triggered by AICAr and brequinar, a known dihydroorotate dehydrogenase (DHODH) inhibitor. Our findings indicate that the mouse MS-5 stromal cell line, known for its cytoprotective effects, does not inhibit AML cell differentiation induced by pyrimidine synthesis inhibitors. Interestingly, AICAr caused morphological changes and growth arrest in MS-5 stromal cells via an AMP-activated protein kinase (AMPK)-dependent pathway. Human stromal cell lines HS-5 and HS-27, as well as primary MSCs isolated from patient bone marrow, were superior in promoting AML differentiation compared with mouse cells in response to AICAr and brequinar, with the inhibitors not significantly affecting the stromal cells themselves. In conclusion, our study highlights the supportive role of human BM MSCs in enhancing the differentiation effects of pyrimidine synthesis inhibitors on AML cells, suggesting that AML treatment strategies focusing on differentiation rather than cell killing may be successful in clinical settings.NEW & NOTEWORTHY This study is the first to demonstrate that human stromal cell lines and primary mesenchymal stromal cells from patients enhance the in vitro differentiation of acute myeloid leukemia (AML) cells induced by pyrimidine synthesis inhibitors, 5-aminoimidazole-4-carboxamide ribonucleoside (AICAr), and brequinar. Furthermore, this is the first report to show that AICAr affects mouse bone marrow stromal cells by activating AMP-activated protein kinase (AMPK) and that human stromal cells are superior to mouse cells for testing the effects of drugs on AML differentiation.