Suppression of c‐Myc enhances p21 WAF1/CIP1 ‐mediated G1 cell cycle arrest through the modulation of ERK phosphorylation by ascochlorin

Anti-Cancer Roles of Probiotic-Derived P8 Protein in Colorectal Cancer Cell Line DLD-1

A novel probiotics-derived protein, P8, suppresses the growth of colorectal cancer (CRC). P8 can penetrate the cell membrane via endocytosis and cause cell cycle arrest in DLD-1 cells through down-regulation of CDK1/Cyclin B1. However, neither the protein involved in the endocytosis of P8 nor the cell cycle arrest targets of P8 are known. We identified two P8-interacting target proteins [importin subunit alpha-4 (KPNA3) and glycogen synthase kinase-3 beta (GSK3β)] using P8 as a bait in pull-down assays of DLD-1 cell lysates. Endocytosed P8 in the cytosol was found to bind specifically to GSK3β, preventing its inactivation by protein kinases AKT/CK1ε/PKA. The subsequent activation of GSK3β led to strong phosphorylation (S^33,37/T⁴¹) of β-catenin, resulting in its subsequent degradation. P8 in the cytosol was also found to be translocated into the nucleus by KPNA3 and importin. In the nucleus, after its release, P8 binds directly to the intron regions of the GSK3β gene, leading to dysregulation of GSK3β transcription. GSK3β is a key protein kinase in Wnt signaling, which controls cell proliferation during CRC development. P8 can result in a cell cycle arrest morphology in CRC cells, even when they are in the Wnt ON signaling state.

The Novel Oral BET-CBP/p300 Dual Inhibitor NEO2734 Is Highly Effective in Eradicating Acute Myeloid Leukemia Blasts and Stem/Progenitor Cells

Acute myeloid leukemia (AML) is a disease characterized by transcriptional dysregulation that results in a block in differentiation and aberrant self-renewal. Inhibitors directed to epigenetic modifiers, aiming at transcriptional reprogramming of AML cells, are currently in clinical trials for AML patients. Several of these inhibitors target bromodomain and extraterminal domain (BET) proteins, cyclic AMP response binding protein-binding protein (CBP), and the E1A-interacting protein of 300 kDa (p300), affecting histone acetylation. Unfortunately, single epigenetic inhibitors showed limited efficacy due to appearance of resistance and lack of effective eradication of leukemic stem cells. Here, we describe the efficacy of 2 novel, orally available inhibitors targeting both the BET and CBP/p300 proteins, NEO1132 and NEO2734, in primary AML. NEO2734 and NEO1132 efficiently reduced the viability of AML cell lines and primary AML cells by inducing apoptosis. Importantly, both NEO drugs eliminated leukemic stem/progenitor cells from AML patient samples, and NEO2734 increased the effectiveness of combination chemotherapy treatment in an in vivo AML patient-derived mouse model. Thus, dual inhibition of BET and CBP/p300 using NEO2734 is a promising therapeutic strategy for AML patients, making it a focus for clinical translation.

MicroRNA-124-3p suppresses PD-L1 expression and inhibits tumorigenesis of colorectal cancer cells via modulating STAT3 signaling

Programmed death ligand 1 (PD-L1) plays a significant role in colorectal tumorigenesis through induction of regulatory T cells (Tregs) and suppression of antitumor immunity. Furthermore, microRNAs (miRNAs) as the posttranscriptional regulators of gene expression show considerable promise as a therapeutic target for colorectal cancer (CRC) treatment. Considering this, in vitro effects of miRNA-124 (miR-124-3p) on CRC cell tumorigenesis and Tregs differentiation via targeting PD-L1 were investigated in the current study. Functional analysis showed that miR-124 is significantly downregulated in CRC tissues as compared with marginal normal samples (p < .0001), and its downregulation was negatively correlated with PD-L1 expression. Moreover, a specific region in PD-L1 3'-untranslated region was predicted as the miR-124 target and validated using the luciferase assay. Further investigation showed that transfection of HT29 and SW480 cells with miR-124 mimics significantly reduced PD-L1 mRNA, protein, and cell surface expression, and inhibited Tregs in coculture models via modulating interleukin [IL]-10, IL-2, tumor necrosis factor α, transforming growth factor beta, and interferon gamma expression levels. Besides, miR-124 overexpression decreased CRC cell proliferation and arrested cell cycle at the G1 phase through downregulation of c-Myc and induced apoptosis in CRC cells via upregulation of both intrinsic and extrinsic pathways. Also, miR-124 exogenous overexpression could reduce colony and spheroid formation ability of CRC cells via downregulating CD44 mRNA expression. miR-124 also diminished MMP-9 expression and subsequently suppressed cell migration and invasion. We also illustrated that STAT3 signaling was repressed by miR-124 in CRC cells. Taken together, our findings imply that considering the involvement of miR-124 in the regulation of PD-L1 through colorectal tumorigenesis and its remarkable antitumor effects, this miRNA could be regarded as the promising target for the development of therapeutic approaches for colorectal cancer.

Piwi-interacting RNAs play a role in vitamin C-mediated effects on endothelial aging

The underlying mechanisms that mediate the effects of vitamin C on endothelial cell aging are widely unknown. To investigate whether Piwi-interacting RNAs (piRNAs) are involved in this process, an endothelial aging model was induced in vitro using H₂O₂ in human umbilical vein endothelial cells (HUVECs) and then treated with vitamin C (VC). Untreated HUVECs without H₂O₂ exposure were used to serve as the negative control group. Cell cycle, cell viability, and aging-associated protein expression were assessed, and RNA sequencing was performed to reveal the piRNA profile. Functional and regulatory networks of the different piRNA target genes were predicted by the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment and Gene Ontology (GO) analysis. H₂O₂ induced G1 phase cell arrest, decreased cell viability, and upregulated the senescence marker p16 in HUVECs. We found that VC treatment inhibited G1 phase cell arrest, increased the number of cells in the S and G2/M phases, increased cell viability, and decreased p16 expression. The piRNA expression profiles revealed that a large proportion of piRNAs that were differentially expressed in H₂O₂-treated HUVECs were partly normalized by VC. Furthermore, a number of piRNAs associated with the response to VC in H₂O₂-treated HUVECs were linked with senescence and cell cycle-related pathways and networks. These results indicate that the ability of VC to attenuate H₂O₂-mediated endothelial cell senescence may be associated with changes in expression of piRNAs that are linked to the cell cycle.

The Role of the Cyclin Dependent Kinase Inhibitor p21cip1/waf1 in Targeting Cancer: Molecular Mechanisms and Novel Therapeutics

p21^cip1/waf1 mediates various biological activities by sensing and responding to multiple stimuli, via p53-dependent and independent pathways. p21 is known to act as a tumor suppressor mainly by inhibiting cell cycle progression and allowing DNA repair. Significant advances have been made in elucidating the potential role of p21 in promoting tumorigenesis. Here, we discuss the involvement of p21 in multiple signaling pathways, its dual role in cancer, and the importance of understanding its paradoxical functions for effectively designing therapeutic strategies that could selectively inhibit its oncogenic activities, override resistance to therapy and yet preserve its tumor suppressive functions.

Ascochlorin induces caspase-independent necroptosis in LPS-stimulated RAW 264.7 macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Plant-specific fungus of natural compound of Ascochyta viciae has traditionally been used in the treatment of sleeping sickness and tumors. The anti-tumor activities of the compounds obtained from Pisum sativum L were evaluated in this study.

AIM OF THE STUDY

In this study, during the prolonged incubation, treatment of the LPS-stimulated tumor-like macrophage RAW 264.7 cells with ASC exhibited the shift of anti-inflammatory behavior to a type of necroptotic cell death named necroptosis.

MATERIALS AND METHODS

Ascochlorin (ASC) purified from plant-specific fungus Ascochyta viciae is a natural compound with the trimethyl oxocyclohexyl structure and an anti-cancer and antibiotic agent. The fungus contributes to the Ascochyta blight disease complex of pea (Pisum sativum L). RAW 264.7 cells have been stimulated with LPS and treated with ASC. Cell viability of the LPS-treated RAW 264.7 cells and bone marrow-derived macrophage (BMDM) cells were examined. Flow cytometry analysis with 7AAD and Annexin V was examined for the apoptotic or necroptosis/late-apoptosis. Cleaved caspase-3, -7 and -8 as well as cleaved PARP were assessed with a caspase inhibitor, z-VAD-fmk. LPS-responsible human leukemic U937 and colon cancer SW480 and HT-29 cells were also examined for the cell viabilities.

RESULTS

Flow cytometry analysis after Annexin V and 7AAD double staining showed that ASC alone induces apoptosis in RAW 264.7 cells, while it induces necroptosis/late-apoptosis in LPS-treated RAW 264.7 cells. 7AAD and Annexin V positive populations were increased in the LPS-treated cells with ASC. Although viability of LPS-treated cells with ASC was decreased, the amounts of cleaved caspase-3, -7 and -8 as well as cleaved PARP were reduced when compared with ASC-treated cells. Upon ASC treatment, the cleaved caspase-8 level was not changed, however, cleaved caspase-3, -7, and PARP were reduced in LPS-stimulated RAW 264.7 cells treated with ASC, claiming a caspase-8 independent necroptosis of ASC. Furthermore, ASC and LPS-cotreated cells which a caspase inhibitor, z-VAD-fmk, was pretreated, showed the decreased cell viability compared with control cells without the inhibitor. Cell viability of RAW 264.7 cells co-treated with ASC and LPS when treated with z-VAD was decreased. In the LPS-responsible human leukemic U937 and colon cancer SW480 and HT-29 cells, cell viabilities were decreased by 10 μM ASC.

CONCLUSION

Prolonged stimulation of ASC with LPS induces the necroptosis in RAW cells. Activated immune cells may share the susceptibility of antitumor agents with the cancer cells.

Icariin promotes wound healing by enhancing the migration and proliferation of keratinocytes via the AKT and ERK signaling pathway

Icariin is a traditional Chinese drug that has long been used to treat various diseases. In the present study, the effect of icariin was investigated on cutaneous wound healing. Using in vitro experiments, it was demonstrated that icariin significantly promoted the migration and proliferation of keratinocytes via the activation of AKT serine/threonine kinase 1 (AKT) and extracellular signal-regulated kinase (ERK). Inhibition of AKT or ERK reversed the effects of icariin on the proliferation and migration of keratinocytes. In addition, icariin inhibited the production of interleukin (IL)-6 and tumor necrosis factor (TNF)-α and induced the production of IL-10. Finally, animal experiments demonstrated that icariin treatment accelerated the wound closure rate. The present findings revealed that icariin may be a promising drug to promote the migration and proliferation of keratinocytes, and to accelerate the healing of skin wounds, through its role in the upregulation of AKT and ERK signaling.

S-allylcysteine suppresses ovarian cancer cell proliferation by DNA methylation through DNMT1

BACKGROUND

The anti-tumor effects of S-allylcysteine (SAC), a water-soluble garlic derivative, on human ovarian cancer cells have been previous studied in vitro and in vivo models but the precise epigenetic molecular mechanisms are still unclear. This study aimed to investigate the epigenetic mechanism of SAC.

METHODS

Human epithelial ovarian cancer cell line A2780 was selected. Cell proliferation and cell cycle was analyzed. DNA methylation, DNA methyltransferase (DNMT) activity, tumor suppressor gene expressions, as well as protein expression were analyzed.

RESULTS

SAC could inhibit the proliferation of A2780 cells in dose- and time-dependent manners (the IC₅₀ was 16.25 mmol/L and 5.25 mmol/L at 48 h and 72 h). Treatment of A2780 cells with SAC resulted in G1/S phase arrest. SAC treatment decreased global DNA methylation levels in A2780 cells in a dose-dependent manner. SAC decreased the levels of 5-methylcytosine, DNMT activity, messenger RNA (mRNA) and protein levels of DNMT1. Additionally, SAC treatment resulted in re-expression of the mRNA and proteins of silenced tumor suppressor gene CDKN1A accompany with reduced cell division control 2 expression.

CONCLUSION

Our data indicated the potential therapeutic effects of SAC on the human ovarian carcinoma cell line A2780 in vitro. The epigenetic mechanism of action of SAC may have important implications for epigenetic therapy.