Involvement of ATM/ATR-p38 MAPK cascade in MNNG induced G1-S arrest

Irradiated tumour cell-derived microparticles upregulate MHC-I expression in cancer cells via DNA double-strand break repair pathway

Radiotherapy (RT) is used for over 50 % of cancer patients and can promote adaptive immunity against tumour antigens. However, the underlying mechanisms remain unclear. Here, we discovered that RT induces the release of irradiated tumour cell-derived microparticles (RT-MPs), which significantly upregulate MHC-I expression on the membranes of non-irradiated cells, enhancing the recognition and killing of these cells by T cells. Mechanistically, RT-MPs induce DNA double-strand breaks (DSB) in tumour cells, activating the ATM/ATR/CHK1-mediated DNA repair signalling pathway, and upregulating MHC-I expression. Inhibition of ATM/ATR/CHK1 reversed RT-MP-induced upregulation of MHC-I. Furthermore, phosphorylation of STAT1/3 following the activation of ATM/ATR/CHK1 is indispensable for the DSB-dependent upregulation of MHC-I. Therefore, our findings reveal the role of RT-MP-induced DSBs and the subsequent DNA repair signalling pathway in MHC-I expression and provide mechanistic insights into the regulation of MHC-I expression after DSBs.

Multiomic analysis identifies CPT1A as a potential therapeutic target in platinum-refractory, high-grade serous ovarian cancer

Resistance to platinum compounds is a major determinant of patient survival in high-grade serous ovarian cancer (HGSOC). To understand mechanisms of platinum resistance and identify potential therapeutic targets in resistant HGSOC, we generated a data resource composed of dynamic (±carboplatin) protein, post-translational modification, and RNA sequencing (RNA-seq) profiles from intra-patient cell line pairs derived from 3 HGSOC patients before and after acquiring platinum resistance. These profiles reveal extensive responses to carboplatin that differ between sensitive and resistant cells. Higher fatty acid oxidation (FAO) pathway expression is associated with platinum resistance, and both pharmacologic inhibition and CRISPR knockout of carnitine palmitoyltransferase 1A (CPT1A), which represents a rate limiting step of FAO, sensitize HGSOC cells to platinum. The results are further validated in patient-derived xenograft models, indicating that CPT1A is a candidate therapeutic target to overcome platinum resistance. All multiomic data can be queried via an intuitive gene-query user interface (https://sites.google.com/view/ptrc-cell-line).

Effect of Acupuncture on the p38 Signaling Pathway in Several Nervous System Diseases: A Systematic Review

Acupuncture is clinically used to treat various diseases and exerts positive local and systemic effects in several nervous system diseases. Advanced molecular and clinical studies have continually attempted to decipher the mechanisms underlying these effects of acupuncture. While a growing understanding of the pathophysiology underlying several nervous system diseases shows it to be related to inflammation and impair cell regeneration after ischemic events, the relationship between the therapeutic mechanism of acupuncture and the p38 MAPK signal pathway has yet to be elucidated. This review discusses the latest advancements in the identification of the effect of acupuncture on the p38 signaling pathway in several nervous system diseases. We electronically searched databases including PubMed, Embase, and the Cochrane Library from their inception to April 2020, using the following keywords alone or in various combinations: "acupuncture", "p38 MAPK pathway", "signaling", "stress response", "inflammation", "immune", "pain", "analgesic", "cerebral ischemic injury", "epilepsy", "Alzheimer's disease", "Parkinson's disease", "dementia", "degenerative", and "homeostasis". Manual acupuncture and electroacupuncture confer positive therapeutic effects by regulating proinflammatory cytokines, ion channels, scaffold proteins, and transcription factors including TRPV1/4, Nav, BDNF, and NADMR1; consequently, p38 regulates various phenomena including cell communication, remodeling, regeneration, and gene expression. In this review article, we found the most common acupoints for the relief of nervous system disorders including GV20, GV14, ST36, ST37, and LI4. Acupuncture exhibits dual regulatory functions of activating or inhibiting different p38 MAPK pathways, contributing to an overall improvement of clinical symptoms and function in several nervous system diseases.

Human CCR6+ Th17 Lymphocytes Are Highly Sensitive to Radiation-Induced Senescence and Are a Potential Target for Prevention of Radiation-Induced Toxicity

PURPOSE

This study addresses the sensitivity of different peripheral CD4⁺ T-lymphocyte subsets to irradiation (IR) and identifies potential targets for the prevention or treatment of radiation-induced toxicity.

METHODS

This study was performed on peripheral blood mononuclear cells or sorted peripheral memory lymphocytes of CCR6⁺ mucosa-homing Th17/CCR6^negTh and regulatory T subtypes of healthy volunteers. Cells were irradiated with a 2 Gy with or without pharmacologic inhibitors of different signaling pathways. Senescence of irradiated cells was assessed by resistance to apoptosis and determination of various senescence-associated biomarkers (senescence associated b-galactosidase activity, p16Ink4a-, p21Cdkn1a-, gH2A.X-, H2A.J expression). Cytokine production was measured in supernatants of irradiated cells by Luminex technology.

RESULTS

Not all CD4⁺ memory T lymphocyte subsets were equally radiosensitive. High sensitivity of CCR6⁺Th17 lymphocytes to IR-induced senescence was shown by expression of the histone variant H2A.J, higher SA-b-Gal activity, and upregulation of p16^Ink4a and p21^Cdkn1a expression. Lower Annexin V staining and cleaved caspase-3, and higher expression of antiapoptotic genes Bcl-2 and Bcl-xL LF, showed that CCR6⁺Th17 lymphocytes were more resistant to IR-induced apoptosis than CCR6^neg memory Th and regulatory T lymphocytes. After a 2 Gy IR, both CCR6⁺Th17 and CCR6^neg cells acquired a moderate senescence-associated secretory phenotype, but only CCR6⁺Th17 cells secreted interleukin 8 (IL-8) and vascular endothelial growth factor-A (VEGF-A). Pharmacologic targeting of reactive oxygen species (ROS), mitogen-activated protein kinases (MAPKs), and mammalian target of rapamycin (mTOR) signaling pathways prevented the expression of senescent markers and IL-8 and VEGF-A expression by CCR6⁺Th17 cells after IR.

CONCLUSIONS

This study suggests that IR induces senescence of CCR6+Th17 lymphocytes associated with secretion of IL-8 and VEGF-A that may be detrimental to the irradiated tissue. ROS-MAPKs signaling pathways are candidate targets to prevent this CCR6⁺Th17-dependent radiation-induced potential toxicity. Finally, the ratio of circulating H2A.J⁺ senescent CCR6⁺ Th17/CD4⁺ T lymphocytes may be a candidate marker of individual intrinsic radiosensitivity.

Energy adaptive response during parthanatos is enhanced by PD98059 and involves mitochondrial function but not autophagy induction

Parthanatos is a programmed necrotic demise characteristic of ATP (adenosine triphosphate) consumption due to NAD+ (nicotinamide adenine dinucleotide) depletion by poly(ADP-ribose) polymerase 1 (PARP1)-dependent poly(ADP-ribosyl)ation on target proteins. However, how the bioenergetics is adaptively regulated during parthanatos, especially under the condition of macroautophagy deficiency, remains poorly characterized. Here, we demonstrated that the parthanatic inducer N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) triggered ATP depletion followed by recovery in mouse embryonic fibroblasts (MEFs). Notably, Atg5-/- MEFs showed great susceptibility to MNNG with disabled ATP-producing capacity. Moreover, the differential energy-adaptive responses in wild-type (WT) and Atg5-/- MEFs were unequivocally worsened by inhibition ofAMP-activated protein kinase (AMPK), sirtuin 1 (SIRT1), and mitochondrial activity. Importantly, Atg5-/- MEFs disclosed diminished SIRT1 and mitochondrial activity essential to the energy restoration during parthanatos. Strikingly, however, parthanatos cannot be exasperated by bafilomycin A1 and MNNG neither provokes microtubule-associated protein 1A/1B-light chain 3 (LC3) lipidation and p62 elimination, suggesting that parthanatos does not induce autophagic flux. Intriguingly, we reported unexpectedly that PD98059, even at low concentration insufficient to inhibit MEK, can promote mitochondrial activity and facilitate energy-restoring process during parthanatos, without modulating DNA damage responses as evidenced by PARP1 activity, p53 expression, and gammaH2AX (H2A histone family, member X (H2AX), phosphorylated on Serine 139) induction. Therefore, we propose that Atg5 deficiency confers an infirmity to overcome the energy crisis during parthanatos and further underscore the deficits in mitochondrial quality control, but not incapability of autophagy induction, that explain the vulnerability in Atg5-deficient cells. Collectively, our results provide a comprehensive energy perspective for an improved treatment to alleviate parthanatos-related tissue necrosis and disease progression and also provide a future direction for drug development on the basis of PD98059 as an efficacious compound against parthanatos.

MicroRNA-181a functions as an oncomir in gastric cancer by targeting the tumour suppressor gene ATM

Based on our previous experiments, this study is to further investigate the functional significance of miR-181a and its target gene in gastric cancer. Expression of miR-181a was detected by qRT-PCR in three normal gastric tissues and three human gastric cancer cell lines (SGC-7901, MGC-803, and BGC-823 cells). After transfection with miR-181a inhibitor, proliferation, apoptosis, migration, and invasion of the SGC-7901 cells were evaluated. Ataxia-telangiectasia mutation (ATM) was predicted as a target gene of miR-181a with bioinformatics analysis, and was verified by lucifersae reporter assay. Expression of ATM protein in HEK293T cells and tissues was measured by Western Blot. Expression of ATM mRNA in HEK293T cells was measured by RT-PCR. Compared with three non-tumour tissues, the expression of miR-181a in three gastric cancer cells was significantly increased by 26.68, 14.83 and 14.96 folds; Compared with Negative Control(NC) and blank groups, transfection of miR-181a inhibitor led to inhibition of SGC7901 cell proliferation, invasion, and migration as well as promotion of apoptosis. A luciferase reporter assay demonstrated that ATM was a direct target of miR-181a, miR-181a mimics transfection down regulated ATM mRNA and protein expression. There was inverse correlation between miR-181a and ATM protein expression in gastric cancer and normal gastric tissues. Our study demonstrates that over-expression of miR-181a might be involved in development of gastric cancer by promoting proliferation and inhibiting apoptosis probably through directly targeting ATM. miR-181a modulation may be a potential strategy for the development of miRNA-based therapy of gastric cancer.

Reactive oxygen species mediate Epstein-Barr virus reactivation by N-methyl-N'-nitro-N-nitrosoguanidine

N-nitroso compounds (NOCs) and Epstein-Barr virus (EBV) reactivation have been suggested to play a role in the development of nasopharyngeal carcinoma (NPC). Although chemicals have been shown to be a risk factor contributing to the carcinogenesis of NPC, the underlying mechanism is not fully understood. We demonstrated recently that N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) enhances the genomic instability and tumorigenicity of NPC cells via induction of EBV reactivation. However, the mechanisms that trigger EBV reactivation from latency remain unclear. Here, we address the role of ROS in induction of EBV reactivation under MNNG treatment. EBV reactivation was induced in over 70% of EBV-positive NA cells and the promoter of Rta (Rp) was activated after MNNG treatment. Inhibitor experiments revealed ATM, p38 MAPK and JNK were activated by ROS and involved in MNNG-induced EBV reactivation. Significantly, ROS scavengers N-acetyl-L-cysteine (NAC), catalase and reduced glutathione inhibited EBV reactivation under MNNG and H₂O₂ treatment, suggesting ROS mediate EBV reactivation. The p53 was essential for EBV reactivation and the Rp activation by MNNG. Moreover, the p53 was phosphorylated, translocated into nucleus, and bound to Rp following ROS stimulation. The results suggest ROS play an important role in initiation of EBV reactivation by MNNG through a p53-dependent mechanism. Our findings demonstrate novel signaling mechanisms used by NOCs to induce EBV reactivation and provide a novel insight into NOCs link the EBV reactivation in the contribution to the development of NPC. Notably, this study indicates that antioxidants might be effective for inhibiting N-nitroso compound-induced EBV reactivation and therefore could be promising preventive and therapeutic agents for EBV reactivation-associated malignancies.

Melphalan-induced apoptosis of EBV-transformed B cells through upregulation of TAp73 and XAF1 and nuclear import of XPA

Melphalan (Mel) is widely used to treat patients with hematologic cancer, including multiple myeloma, but its mechanism of action in EBV-transformed B cells is poorly described. In this study, we demonstrate a novel mechanism by which transcriptionally active p73 (TAp73) induces translocation of X-linked inhibitor of apoptosis protein-associated factor 1 (XAF1) and xeroderma pigmentosum group A (XPA) during apoptosis caused by Mel treatment. We observed that Mel induced significant generation of reactive oxygen species (ROS) and subsequent apoptosis, as well as an early phosphorylation of p38 MAPK that preceded expression of the mitochondria membrane potential disruption-related molecules and the cleavage of caspases. In particular, Mel led to upregulation of TAp73, XAF1, and Puma and induced XPA nuclear import and translocation of Bax into mitochondria. Mel-induced apoptosis was inhibited by pretreatment with the ROS scavenger 4-amino-2,4-pyrrolidine-dicarboxylic acid (APDC) and the p38 MAPK inhibitor SB203580. We supposed that ROS generation might be the first event in Mel-induced apoptosis, because APDC blocked the increase in ROS, p38 MAPK, and TAp73, but SB203580 did not block ROS generation. Moreover, Mel elicited activation of ATR, and APDC inhibited phosphorylation of ATR but not SB203580. APDC and SB203580 completely blocked XPA and Bax translocation. We conclude that Mel promotes TAp73-mediated XAF1 and Puma expression via ROS generation and ATR/p38 MAPK pathway activation, thereby triggering apoptosis. Our results provide evidence of a novel alternate regulatory mechanism of TAp73 and reveal that Mel may be a therapeutic drug for curing EBV-related malignancies.

Digalloylresveratrol, a novel resveratrol analog inhibits the growth of human pancreatic cancer cells

Digalloylresveratrol (DIG) is a recently synthesized substance aimed to combine the effects of the natural polyphenolic compounds gallic acid and resveratrol, which both are excellent free radical scavengers with anticancer activity. In this study, we investigated the effects of DIG in the human AsPC-1 and BxPC-3 pancreatic adenocarcinoma cell lines. Treatment with DIG dose-dependently attenuated cells in the S phase of the cell cycle and led to a significant depletion of the dATP pool in AsPC-1 cells. The incorporation of (14)C-cytidine into nascent DNA of tumor cells was significantly inhibited at all DIG concentrations due to inhibition of ribonucleotide reductase, a key enzyme of DNA synthesis in tumor cells. Furthermore, Erk1/2 became inactivated and moderated p38 phosphorylation reflecting increased replication stress. DIG also activated ATM and Chk2, and induced the phosphorylation and proteasomal degradation of the proto-oncogene Cdc25A, which contributed to cell cycle attenuation. Taken together, DIG is an excellent free radical scavenger, strongly inhibits RR in situ activity, cell cycle progression, and colony formation in AsPC-1 and BxPC-3 cells thus warranting further investigations.

The role of ROS toxicity in spontaneous aneuploidy in cultured cells

It is well known that the karyotype of animal cells cultured in vitro tends to become aneuploid as the culture ages. Aneuploidy can cause genetic instability, alter the biological properties of cells, and affect their application in genetic studies and cell engineering. Understanding the causes and mechanisms of aneuploidy is primary to control its occurrence in cultured cells, and is also helpful to understand the mechanisms of tumorigenesis because aneuploidy is a hallmark of tumor cells. This review underscores the potential role of reactive oxygen species (ROS) toxicity in spontaneous aneuploidy of cultured cells. The underlying mechanisms and possible sources of ROS are also discussed.

Involvement of G1/S checkpoint regulators during photodynamic-therapy-mediated cell cycle arrest in human colon carcinoma SW480 cells

AIM: To investigate the involvement of G₁/S regulators during ALA-PDT-mediated cell cycle arrest.

METHODS: Colon carcinoma SW480 cells were treated with 1 mmol/L ALA and 6 h later irradiated with 9 J/cm² 631 nm light from a laser. The analysis of cell cycle arrest by ALA-PDT was performed by flow cytometry. The effect of ALA-PDT on G₁/S cell cycle regulators Chk2, CyclinD1 and P21WAF1/Cip1/Sdi1 was examined by using immunocytochemical technique.

RESULTS: ALA-PDT resulted in G₀-G₁ phase arrest of the tumor cell cycle in post-PDT in a time-dependent manner. Immunocytochemical analysis revealed that PDT resulted in an induction of G₁/S checkpoint regulation factors such as Chk2 and P21WAF1/Cip1/Sdi1, and a down-regulation of CyclinD1 in a time-dependent manner.

CONCLUSION: ALA-PDT causes G₀-G₁ phase arrest of SW480 cell cycle in post-PDT earlier period; PDT-mediated induction of G₁/S checkpoint regulators Chk2 and P21WAF1/Cip1/Sdi1 results in the imposition of artificial checkpoint at G₁-S checkpoint thereby leading to an arrest of cells in G₀-G₁ phase of the cell cycle through inhibition in cyclinD1 in a time-dependent manner.

MAPK signal transduction and apoptosis of human gastric carcinoma cells induced by liposomes of survivin antisense oligonucleotide

AIM: To study the relation of mitogen-activated protein kinase (MAPK) signal transduction and apoptosis of human gastric carcinoma cells HS-746T induced by liposomes of survivin antisense oligonucleotide (ASODN).

METHODS: Survivin ASODN was designed and synthesised to transfect human gastric carcinoma cells HS-746T. The cultured cells were divided into 6 groups: vacuity control group, liposome and sense oligonucleotide (SODN) group, 100, 200 and 400 nmoL/L ASODN group and P38MAPK, extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor groups. Apoptotic index (AI) and proliferative index (PI) were examined by flow cytometry after transfection 2, 4, 8, 12, 24 and 48 h. RT-PCR, immunocytochemical stain, Western blot, immuno-precipitation and kinase activity assay were used to detect protein expression and activity of P38MAPK, ERK1/2, survivin and survivin mRNA after transfection.

RESULTS: Expression of ERK1/2 and P38MAPK has not significantly different among vacuity control group, liposomes group and SODN group. The apoptotic cells increased in anisoconcentration survivin ASODN groups and AI was higher than that of other control group. Apoptotic cells decreased in P38MAPK inhibitor group while increased in ERK1/2. The protein and mRNA expression of survivin decreased when transfection concentration was increased. The phosphorylated and nonphosphorylated ERK1/ 2 showed a dose-and time-dependent decrease whereas protein level of p38MAPK remained unchanged, but activity increased.

CONCLUSION: Survivin ASODN can induce apoptosis of human gastric carcinoma cells in vitro though MAPK signal transduction including activating apoptosis-related signal P38MAPK and suppressing proliferation-related signal ERK1/2.