Tanshinone IIA induces apoptosis via inhibition of Wnt/β‑catenin/MGMT signaling in AtT‑20 cells

Pancreatic Neuroendocrine Tumors: Signaling Pathways and Epigenetic Regulation

Pancreatic neuroendocrine tumors (PNETs) are characterized by dysregulated signaling pathways that are crucial for tumor formation and progression. The efficacy of traditional therapies is limited, particularly in the treatment of PNETs at an advanced stage. Epigenetic alterations profoundly impact the activity of signaling pathways in cancer development, offering potential opportunities for drug development. There is currently a lack of extensive research on epigenetic regulation in PNETs. To fill this gap, we first summarize major signaling events that are involved in PNET development. Then, we discuss the epigenetic regulation of these signaling pathways in the context of both PNETs and commonly occurring-and therefore more extensively studied-malignancies. Finally, we will offer a perspective on the future research direction of the PNET epigenome and its potential applications in patient care.

Repurposing synthetic and natural derivatives induces apoptosis in an orthotopic glioma-induced xenograft model by modulating WNT/β-catenin signaling

BACKGROUND

Glioblastomas arise from multistep tumorigenesis of the glial cells. Despite the current state-of-art treatment, tumor recurrence is inevitable. Among the innovations blooming up against glioblastoma, drug repurposing could provide profound premises for treatment enhancement. While considering this strategy, the efficacy of the repurposed drugs as monotherapies were not up to par; hence, the focus has now shifted to investigate the multidrug combinations.

AIM

To investigate the efficacy of a quadruple-combinatorial treatment comprising temozolomide along with chloroquine, naringenin, and phloroglucinol in an orthotopic glioma-induced xenograft model.

METHODS

Antiproliferative effect of the drugs was assessed by immunostaining. The expression profiles of WNT/β-catenin and apoptotic markers were evaluated by qRT-PCR, immunoblotting, and ELISA. Patterns of mitochondrial depolarization was determined by flow cytometry. TUNEL assay was performed to affirm apoptosis induction. In vivo drug detection study was carried out by ESI-Q-TOF MS analysis.

RESULTS

The quadruple-drug treatment had significantly hampered glioma proliferation and had induced apoptosis by modulating the WNT/β-catenin signaling. Interestingly, the induction of apoptosis was associated with mitochondrial depolarization. The quadruple-drug cocktail had breached the blood-brain barrier and was detected in the brain tissue and plasma samples.

CONCLUSION

The quadruple-drug combination served as a promising adjuvant therapy to combat glioblastoma lethality in vivo and can be probed for translation from bench to bedside.

Research progress on the role of the Wnt signaling pathway in pituitary adenoma

Pituitary adenoma (PA) is the third most common central nervous system tumor originating from the anterior pituitary, but its pathogenesis remains unclear. The Wnt signaling pathway is a conserved pathway involved in cell proliferation, Self-renewal of stem cells, and cell differentiation. It is related to the occurrence of various tumors, including PA. This article reviews the latest developments in Wnt pathway inhibitors and pathway-targeted drugs. It discusses the possibility of combining Wnt pathway inhibitors with immunotherapy to provide a theoretical basis for the combined treatment of PA.

Modulating MGMT expression through interfering with cell signaling pathways

Guanine O6-alkylating agents are widely used as first-line chemotherapeutic drugs due to their ability to induce cytotoxic DNA damage. However, a major hurdle in their effectiveness is the emergence of chemoresistance, largely attributed to the DNA repair pathway mediated by O6-methylguanine-DNA methyltransferase (MGMT). MGMT plays an important role in removing the alkyl groups from lethal O6-alkylguanine (O6-AlkylG) adducts formed by chemotherapeutic alkylating agents. By doing so, MGMT enables tumor cells to evade apoptosis and develop drug resistance toward DNA alkylating agents. Although covalent inhibitors of MGMT, such as O6-benzylguanine (O6-BG) and O6-(4-bromothenyl)guanine (O6-4-BTG or lomeguatrib), have been explored in clinical settings, their utility is limited due to severe delayed hematological toxicity observed in most patients when combined with alkylating agents. Therefore, there is an urgent need to identify new targets and unravel the underlying molecular mechanisms and to develop alternative therapeutic strategies that can overcome MGMT-mediated tumor resistance. In this context, the regulation of MGMT expression via interfering the specific cell signaling pathways (e.g., Wnt/β-catenin, NF-κB, Hedgehog, PI3K/AKT/mTOR, JAK/STAT) emerges as a promising strategy for overcoming tumor resistance, and ultimately enhancing the efficacy of DNA alkylating agents in chemotherapy.

Pharmacological inhibition of serine synthesis enhances temozolomide efficacy by decreasing O6-methylguanine DNA methyltransferase (MGMT) expression and reactive oxygen species (ROS)-mediated DNA damage in glioblastoma

Glioblastoma (GBM) is the most malignant primary tumor in the central nervous system of adults. Temozolomide (TMZ), an alkylating agent, is the first-line chemotherapeutic agent for GBM patients. However, its efficacy is often limited by innate or acquired chemoresistance. Cancer cells can rewire their metabolic programming to support rapid growth and sustain cell survival against chemotherapies. An example is the de novo serine synthesis pathway (SSP), one of the main branches from glycolysis that is highly activated in multiple cancers in promoting cancer progression and inducing chemotherapy resistance. However, the roles of SSP in TMZ therapy for GBM patients remain unexplored. In this study, we employed NCT503, a highly selective inhibitor of phosphoglycerate dehydrogenase (PHGDH, the first rate-limiting enzyme of SSP), to study whether inhibition of SSP may enhance TMZ efficacy in MGMT-positive GBMs. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), flowcytometry and colony formation assays demonstrated that NCT503 worked synergistically with TMZ in suppressing GBM cell growth and inducing apoptosis in T98G and U118 cells in vitro. U118 and patient-derived GBM subcutaneous xenograft models showed that combined NCT503 and TMZ treatment inhibited GBM growth and promoted apoptosis more significantly than would each treatment alone in vivo. Mechanistically, we found that NCT503 treatment decreased MGMT expression possibly by modulating the Wnt/β-catenin pathway. Moreover, intracellular levels of reactive oxygen species were elevated especially when NCT503 and TMZ treatments were combined, and the synergistic effects could be partially negated by NAC, a classic scavenger of reactive oxygen species. Taken together, these results suggest that NCT503 may be a promising agent for augmenting TMZ efficacy in the treatment of GBM, especially in TMZ-resistant GBMs with high expression of MGMT.

The interaction of canonical Wnt/β-catenin signaling with protein lysine acetylation

Canonical Wnt/β-catenin signaling is a complex cell-communication mechanism that has a central role in the progression of various cancers. The cellular factors that participate in the regulation of this signaling are still not fully elucidated. Lysine acetylation is a significant protein modification which facilitates reversible regulation of the target protein function dependent on the activity of lysine acetyltransferases (KATs) and the catalytic function of lysine deacetylases (KDACs). Protein lysine acetylation has been classified into histone acetylation and non-histone protein acetylation. Histone acetylation is a kind of epigenetic modification, and it can modulate the transcription of important biological molecules in Wnt/β-catenin signaling. Additionally, as a type of post-translational modification, non-histone acetylation directly alters the function of the core molecules in Wnt/β-catenin signaling. Conversely, this signaling can regulate the expression and function of target molecules based on histone or non-histone protein acetylation. To date, various inhibitors targeting KATs and KDACs have been discovered, and some of these inhibitors exert their anti-tumor activity via blocking Wnt/β-catenin signaling. Here, we discuss the available evidence in understanding the complicated interaction of protein lysine acetylation with Wnt/β-catenin signaling, and lysine acetylation as a new target for cancer therapy via controlling this signaling.

Mechanism of DNA methylation-mediated downregulation of O6-Methylguanine-DNA methyltransferase in cartilage injury of Kashin-Beck Disease

OBJECTIVE

Kashin-Beck Disease (KBD) is an endemic osteoarthropathy, in which excessive apoptosis of chondrocytes occurs. O6-methylguanine-DNA methyltransferase (MGMT), a DNA damage repair gene, plays an important role in apoptosis but the mechanism is unclear in KBD cartilage injury. This study was to investigate the expression and promoter methylation of MGMT in KBD patients and its role in DNA damage and apoptosis of chondrocytes.

METHODS

MGMT mRNA and protein level were detected by quantitative real-time PCR and immunohistochemistry. Demethylation of MGMT was carried out using 5-Aza-2'-deoxycytidine, and the methylation level of MGMT promoter was measured by quantitative methylation specific PCR. Next, shRNA was used to knockdown the expression of MGMT. Cell viability, apoptosis and DNA damage were determined by MTT assay, flow cytometry, Hoechst 33342 staining and alkaline comet assay following T-2 toxin and selenium treatment.

RESULTS

MGMT protein expression and mRNA levels were decreased (p = 0.02, p = 0.007) and promoter methylation was increased (p = 0.008) in KBD patients. Meanwhile, MGMT level was upregulated by 5-Aza-2'-deoxycytidine in chondrocytes (p = 0.0002). DNA damage and apoptosis rates were increased in MGMT-silenced chondrocytes (all p < 0.0001). Furthermore, DNA damage and apoptosis were increseaed in chondrocytes treated with T-2 toxin (all p < 0.0001), but were decreased after selenium treatment (p < 0.0001, p = 0.01). Decreased mRNA level and increased methylation of MGMT were found in T-2 toxin group (p = 0.005, p = 0.002), while selenium reversed it (p = 0.02, p = 0.004).

CONCLUSIONS

MGMT might play a crucial part in the pathogenesis of KBD cartilage injury, which providing a therapeutic target for KBD.

Sodium Tanshinone IIA Sulfonate Attenuates Cigarette Smoke Extract-Induced Mitochondrial Dysfunction, Oxidative Stress, and Apoptosis in Alveolar Epithelial Cells by Enhancing SIRT1 Pathway

Emphysema is one of the most important phenotypes for chronic obstructive pulmonary disease (COPD). Apoptosis in alveolar epithelial cells (AECs) causes the emphysematous alterations in the smokers and patients with COPD. Sirtuin 1 (SIRT1) is able to attenuate mitochondrial dysfunction, oxidative stress, and to modulate apoptosis. It has been shown that sodium tanshinone IIA sulfonate (STS), a water-soluble derivative of tanshinone IIA, protects against cigarette smoke (CS)-induced emphysema/COPD in mice. However, the mechanisms underlying these findings remain unclear. Here, we investigate whether and how STS attenuates AEC apoptosis via a SIRT1-dependent mechanism. We found that STS treatment decreased CS extract (CSE)-induced apoptosis in human alveolar epithelial A549 cells. STS reduced oxidative stress, improved mitochondrial function and mitochondrial membrane potential (ΔΨm), and restored mitochondrial dynamics-related protein expression. Moreover, STS promoted mitophagy, and increased oxidative phosphorylation protein levels (complexes I-IV) in CSE-stimulated A549 cells. The protective effects of STS were associated with SIRT1 upregulation, because SIRT1 inhibition by EX 527 significantly attenuated or abolished the ability of STS to reverse the CSE-induced mitochondrial damage, oxidative stress, and apoptosis in A549 cells. In conclusion, STS ameliorates CSE-induced AEC apoptosis by improving mitochondrial function and reducing oxidative stress via enhancing SIRT1 pathway. These findings provide novel mechanisms underlying the protection of STS against CS-induced COPD.

Targeting interleukin-β by plant-derived natural products: Implications for the treatment of atherosclerotic cardiovascular disease

Inflammation is the main contributing factor to atheroma formation in atherosclerosis. Interleukin-1 beta (IL-1β) is an inflammatory mediator found in endothelial cells and resident leukocytes. Canakinumab is a selective monoclonal antibody against IL-1β which attenuates inflammation and concurrently precipitates fatal infections and sepsis. Natural products derived from medicinal plants, herbal remedy and functional foods are widely used nowadays. Experimental and clinical trial evidence supports that some natural products such as curcumin, resveratrol, and quercetin have potential effects on IL-1β suppression. In this review, we tried to document findings that used medicinal plants and plant-based natural products for treating atherosclerosis and its related diseases through the suppression of IL-1β.

Cir-ITCH inhibits gastric cancer migration, invasion and proliferation by regulating the Wnt/β-catenin pathway

Circular RNAs (circRNAs) are differentially expressed in various tumours, but the expression and regulatory mechanisms of circular RNA ITCH (cir-ITCH) in gastric cancer remain unclear. For this reason, in the present study, we assessed the expression of cir-ITCH and the associated regulatory mechanism of cir-ITCH in gastric cancer. Through RTq-PCR assays, we observed that cir-ITCH expression was attenuated in gastric cancer cell lines and tissues, with cir-ITCH expression in gastric cancer tissues with lymph node metastasis being considerably lower than that observed in gastric cancer tissues without lymph node metastasis. In addition, we demonstrated that cir-ITCH or linear ITCH may be a useful marker for gastric cancer prognosis by Kaplan–Meier survival analysis. We also showed that cir-ITCH overexpression could increase linear ITCH expression through miR-17 via RNA immunoprecipitation (RIP) and luciferase reporter assays. Moreover, in vivo and in vitro experimental results showed that cir-ITCH can act as a tumour suppressor to prevent gastric cancer tumourgenesis by sponging miR-17. The Wnt/β-catenin pathway plays a crucial role during the carcinogenesis of cancers, and we observed that cir-ITCH could negatively regulate Wnt/β-catenin signalling, which could be restored by miR-17. In summary, cir-ITCH was shown to prevent gastric cancer tumourgenesis through the Wnt/β-catenin signalling pathway by sequestering miR-17.

Recovery of chicken growth plate by TanshinoneⅡA through wnt/β-catenin pathway in thiram-induced Tibial Dyschondroplasia

Tibial Dyschondroplasia (TD), a metabolic disease of fast growing poultry birds that effects the growth of bone and cartilage, is characterized by anorexia, mental depression and lameness. Wnt/β-catenin pathway can mediate the occurrence of TD, and previous study showed the therapeutic effect of TanshinoneⅡA to TD Broilers. However there is no report about the effect of TanshinoneⅡA treating TD broiler chicken through wnt/β-catenin pathway. The objective of this study was to explore the potential mechanism of how Tanshinone II A treats TD. Hematoxylin and eosin staining was used to study histologic pathology of growth plates. Key gene expressions were tested by western blot and reverse transcription quantitative real-time PCR. Results compared with control groups, showed the TD broilers' growth plate performed significantly better by treating with TanshinoneⅡA. After chickens treated by TanshinoneⅡA, the gene and protein expression of WNT5α and BMP-2 were increased (P < 0.05), but the β-catenin were decreased (P < 0.05), which are all key genes expressed in wnt/β-catenin pathway. Therefore, TanshinoneⅡA can potentially treat TD by affecting the expression of genes in wnt/β-catenin pathway and it has availability to use as treatment for TD broilers.

20(S)-ginsenoside-Rg3 reverses temozolomide resistance and restrains epithelial-mesenchymal transition progression in glioblastoma

Glioblastoma multiforme (GBM) is one of the most malignant human intracranial tumors. Temozolomide (TMZ) is the primary alkylating agent for GBM patients. However, many GBM patients are resistant to TMZ. Therefore, patients with GBM urgently need more effective therapeutic options. 20(S)‐ginsenoside‐Rg3 (20(S)‐Rg3) is a natural chemical with anti‐tumor effects, but at present there is little understanding of its functional mechanism. Several research reports have demonstrated that O⁶‐methylguanine DNA‐methyltransferase (MGMT) repairs damaged DNA and contributes to TMZ resistance in gliomas. In addition, recent studies have shown that MGMT gene expression could be regulated by the Wnt/β‐catenin pathway. However, whether 20(S)‐Rg3 inhibits MGMT expression and augments chemosensitivity to Temozolomide (TMZ) in glioma cells remains unclear. In this study, we explored the modulating effects of 20(S)‐Rg3 on MGMT. We used glioma cell lines, primary cell strain (including T98G, U118 and GBM‐XX; all of them are MGMT‐positive glioma cell lines) and xenograft glioma models to examine whether 20(S)‐Rg3 increased the sensitivity to TMZ and to reveal the underlying mechanisms. We found that the MGMT expression was effectively downregulated by 20(S)‐Rg3 via the Wnt/β‐catenin pathway in glioma cell lines, and TMZ resistance was significantly reversed by 20(S)‐Rg3. Meanwhile, 20(S)‐Rg3 shows no obvious cytotoxicity at its effective dose and is well tolerated in vivo. In addition, we found that 20(S)‐Rg3 significantly restrains the epithelial‐mesenchymal transition (EMT) progression of glioma cells. Taken together, these results indicate that 20(S)‐Rg3 may be a novel agent to use in treatment of GBM, especially in TMZ‐resistant GBM with high MGMT expression.

Unmethylated promoter DNA correlates with p53 expression and apoptotic levels only in Vitamin B9 and B12 deficient megaloblastic anemia but not in non-megaloblastic anemia controls

Cyanocobalamin (Vitamin B12, VB12) and Folic acid (Vitamin B9, VB9) deficiency leads to anemia in women. We have recently shown low VB12 and VB9 levels in the serum of megaloblastic anemia (MBA) patients. Further, our study demonstrated elevated homocysteine and p53, respectively, in the serum and bone marrow aspirates of MBA patients but not in non-MBA subjects. However, it is unknown whether any gender specific variation in VB12 and VB9 level exists in MBA and non-MBA patients? In addition, it is unclear whether low VB12 and VB9 has a role in the regulation of p53 expression in MBA patients? And whether elevated p53 is functionally active? If so, does bone marrow aspirates of MBA patients show elevated apoptosis. Hence, we have analyzed VB12 and VB9 levels in MBA patients and compared with non-MBA subjects. Next, methylation status of p53 promoter was determined and correlated with p53 expression. Furthermore, the level of apoptosis in bone marrow aspirate paraffin blocks was estimated using TUNEL staining. In conclusion, low VB12 and VB9 in male and female patients directly correlate with p53 promoter unmethylation status, but, inversely correlate with p53 protein expression and its activity, only in MBA cases but not in non-MBA controls.