Enhanced Gadd45 expression and delayed G2/M progression are p53-dependent in zinc-supplemented human bronchial epithelial cells

Blue LED light induces cytotoxicity via ROS production and mitochondrial damage in bovine subcutaneous preadipocytes

The purpose of this study was to investigate the effect and mechanism of blue light irradiation on bovine subcutaneous preadipocytes. In this study, preadipocytes were divided into dark group (control) and blue light group. Results show that blue light exposure time-dependently reduced the viability of preadipocytes and induced mitochondrial damage, in accompaniment with the accumulation of intracellular reactive oxygen species (ROS). Meanwhile, blue light caused oxidative stress, as evidenced by the increased MDA level, the reduced T-AOC contents, as well as the decreased activities of antioxidant enzymes. Additionally, blue light treatment induced apoptosis and G2/M phase arrest via Bcl-2/Bax/cleaved caspase-3 pathway and P53/GADD45 pathway, respectively. Protein expressions of LC3-II/LC3-I and P62 were up-regulated under blue light exposure, indicating blue light initiated autophagy but impeded autophagic degradation. Moreover, blue light caused an increase in the secretion of pro-inflammatory factors (TNF-α, IL-1β, and IL-6). Pretreatment with N-acetylcysteine (NAC), a potent ROS scavenger, restored the loss of mitochondrial membrane potential (Δψ) and reduced excess ROS. Additionally, the above negative effects of blue light on cells were alleviated after NAC administration. In conclusion, this study demonstrates blue light induces cellular ROS overproduction and Δψ depolarization, resulting in the decrease of cell viability and the activation of apoptosis, autophagy, and inflammation, providing a reference for the application of blue light in the regulation of fat cells in the future.

Sublethal treatment with plasma-activated medium induces senescence-like growth arrest of A549 cells: involvement of intracellular mobile zinc

Plasma-activated medium (PAM) is a solution produced by exposing a liquid medium to non-thermal atmospheric pressure plasma (NTAPP). A number of reactive molecules, such as reactive oxygen species and reactive nitrogen species, are contained in PAM. Therefore, exposure to high doses of PAM results in cell death. We previously demonstrated that intracellular zinc (Zn²⁺) serves as an important mediator in PAM-induced cell death; however, the effects of sublethal treatment with PAM on cell functions are not fully understood. In the present study, we found that sublethal PAM treatment suppressed cell proliferation and induced senescence-like changes in lung adenocarcinoma A549 cells. Cell cycle analysis revealed that PAM induced cell cycle arrest at the G2/M phase. PAM increased the level of intracellular free Zn²⁺ and the Zn²⁺ chelator TPEN counteracted PAM-induced growth suppression, suggesting that Zn²⁺ functions in PAM-induced growth suppression. In addition, sublethal treatment with PAM induced phosphorylation of ATM kinase, accumulation of p53 protein, and expression of p21 and GADD45A, which are known p53 target genes, in a Zn²⁺-dependent manner. These results suggest that the induction of growth arrest and cellular senescence by sublethal PAM treatment is mediated by Zn²⁺-dependent activation of the ATM/p53 pathway.

Antitumor activity and expression profiles of genes induced by sulforaphane in human melanoma cells

Purpose

Human melanoma is a highly aggressive incurable cancer due to intrinsic cellular resistance to apoptosis, reprogramming, proliferation and survival during tumour progression. Sulforaphane (SFN), an isothiocyanate found in cruciferous vegetables, plays a role in carcinogenesis in many cancer types. However, the cytotoxic molecular mechanisms and gene expression profiles promoted by SFN in human melanoma remain unknown.

Methods

Three different cell lines were used: two human melanoma A375 and 501MEL and human epidermal melanocytes (HEMa). Cell viability and proliferation, cell cycle analysis, cell migration and invasion and protein expression and phosphorylation status of Akt and p53 upon SFN treatment were determined. RNA-seq of A375 was performed at different time points after SFN treatment.

Results

We demonstrated that SFN strongly decreased cell viability and proliferation, induced G₂/M cell cycle arrest, promoted apoptosis through the activation of caspases 3, 8, 9 and hampered migration and invasion abilities in the melanoma cell lines. Remarkably, HEMa cells were not affected by SFN treatment. Transcriptomic analysis revealed regulation of genes involved in response to stress, apoptosis/cell death and metabolic processes. SFN upregulated the expression of pro-apoptotic genes, such as p53, BAX, PUMA, FAS and MDM2; promoted cell cycle inhibition and growth arrest by upregulating EGR1, GADD45B, ATF3 and CDKN1A; and simultaneously acted as a potent inhibitor of genotoxicity by launching the stress-inducible protein network (HMOX1, HSPA1A, HSPA6, SOD1).

Conclusion

Overall, the data show that SFN cytotoxicity in melanoma derives from complex and concurrent mechanisms during carcinogenesis, which makes it a promising cancer prevention agent.

Electronic supplementary material

The online version of this article (doi:10.1007/s00394-017-1527-7) contains supplementary material, which is available to authorized users.

Circadian genes Per1 and Per2 increase radiosensitivity of glioma in vivo

Per1 and Per2 play a key role in regulating the circadian rhythm in mammals. We report here that although both genes were expressed with a circadian rhythm in glioma and normal brain tissue in rats, their expression profiles differed in the two types of tissue. In addition, high expression of Per1 and Per2 in glioma tissue was associated with increased sensitivity to x-irradiation. No such sensitizing effect was observed in normal tissue. Our results suggest that Per1 and Per2 expression may increase the efficacy of radiotherapy against glioma by promoting apoptosis.

Therapeutic ROS targeting of GADD45γ in the induction of G2/M arrest in primary human colorectal cancer cell lines by cucurbitacin E

Cucurbitacin E (CuE) or α-elaterin is a natural compound previously shown to be an antifeedant as well as a potent chemopreventive agent against several types of cancer. The present study investigated the anticancer effects of CuE on colorectal cancer (CRC) using primary cell lines isolated from five CRC patients in Taiwan, Specifically, we explored the anti-proliferation and cell cycle G2/M arrest induced by CuE in CRC cells. MPM-2 flow cytometry tests show that CuE-treated cells accumulated in metaphase (CuE 2.5-7.5 μM). Results further indicate that CuE produced G2/M arrest as well as the downregulation of CDC2 and cyclin B1 expression and dissociation. Both effects increased proportionally with the dose of CuE; however, the inhibition of proliferation, arrest of mitosis, production of reactive oxygen species (ROS), and loss of mitochondrial membrane potential (ΔΨm) were found to be dependent on the quantity of CuE used to treat the cancer cells. In addition, cell cycle arrest in treated cells coincided with the activation of the gene GADD45(α, β, γ). Incubation with CuE resulted in the binding of GADD45γ to CDC2, which suggests that the delay in CuE-induced mitosis is regulated by the overexpression of GADD45γ. Our findings suggest that, in addition to the known effects on cancer prevention, CuE may have antitumor activities in established CRC.

Inducement of mitosis delay by cucurbitacin E, a novel tetracyclic triterpene from climbing stem of Cucumis melo L., through GADD45γ in human brain malignant glioma (GBM) 8401 cells

Cucurbitacin E (CuE) is a natural compound previously shown to have anti-feedant, antioxidant and antitumor activities as well as a potent chemo-preventive action against cancer. The present study investigates its anti-proliferative property using MTT assay; CuE demonstrated cytotoxic activity against malignant glioma GBM 8401 cells and induced cell cycle G₂/M arrest in these cells. CuE-treated cells accumulated in metaphase (CuE 2.5–10 μM) as determined using MPM-2 by flow cytometry. We attempted to characterize the molecular pathways responsible for cytotoxic effects of CuE in GBM 8401 cells. We studied the genome-wide gene expression profile on microarrays and molecular networks by using pathway analysis tools of bioinformatics. The CuE reduced the expression of 558 genes and elevated the levels of 1354 genes, suggesting an existence of the common pathways involved in induction of G₂/M arrest. We identified the RB (GADD45β and GADD45γ) and the p53 (GADD45α) signaling pathways as the common pathways, serving as key molecules that regulate cell cycle. Results indicate that CuE produced G₂/M arrest as well as the upregulation of GADD45 γ and binding with CDC2. Both effects increased proportionally with the dose of CuE, suggesting that the CuE-induced mitosis delay is regulated by GADD45γ overexpression. Our findings suggest that, in addition to the known effects on cancer prevention, CuE may have antitumor activity in glioma therapy.

Protective roles of Gadd45 and MDM2 in blueberry anthocyanins mediated DNA repair of fragmented and non-fragmented DNA damage in UV-irradiated HepG2 cells

Growth Arrest and DNA Damage-inducible 45 (Gadd45) and MDM2 proteins, together with p21 and p53, play important roles in cell cycle checkpoints, DNA repair, and genome integrity maintenance. Gadd45 and MDM2 were activated and transcribed instantly by UV irradiation, whereas blueberry anthocyanins (BA) decreased the gene and protein expression levels in HepG2 cells for up to 24 h, and gradually restored the UV-induced fragmented and non-fragmented DNA damage of the nucleus at a time point of 12 h. Nevertheless, UV-irradiated HepG2 cell arrests occurred mainly in the G1 phase, which indicated G1 as a checkpoint. The proteins, p21 and p53, retain cellular integrity, suppressing the oncogenic transformation by interruption of the G1 phase of the cellular cycle, giving time for repairing the damage to DNA, or apoptosis induction if the damage is too severe to be repaired, while MDM2 and Gadd45 concomitantly ensure the presence of p53 and p21. Thus, we conclude that repair, together with Gadd45 and MDM2 genes, were involved in light and dark reaction mechanisms, however, BA could interfere and assist the repair through restoration, although further studies of the complex of the gene cascades triggered and responded to in BA-assisted DNA repair are needed.

Sulforaphane induced cell cycle arrest in the G2/M phase via the blockade of cyclin B1/CDC2 in human ovarian cancer cells

Background

Malignant tumors are the single most common cause of death and the mortality rate of ovarian cancer is the highest among gynecological disorders. The excision of benign tumors is generally followed by complete recovery; however, the activity of cancer cells often results in rapid proliferation even after the tumor has been excised completely. Thus, clinical treatment must be supplemented by auxiliary chemotherapy or radiotherapy. Sulforaphane (SFN) is an extract from the mustard family recognized for its anti-oxidation abilities, phase 2 enzyme induction, and anti-tumor activity.

Methods

This study investigated the cell cycle arrest in G2/M by SFN and the expression of cyclin B1, Cdc2, and the cyclin B1/CDC2 complex in PA-1 cells using western blotting and co-IP western blotting.

Results

This study investigated the anticancer effects of dietary isothiocyanate SFN on ovarian cancer, using cancer cells line PA-1. SFN-treated cells accumulated in metaphase by CDC2 down-regulation and dissociation of the cyclin B1/CDC2 complex.

Conclusion

Our findings suggest that, in addition to the known effects on cancer prevention, SFN may also provide antitumor activity in established ovarian cancer.

GADD45 proteins: central players in tumorigenesis

The Growth Arrest and DNA Damage-inducible 45 (GADD45) proteins have been implicated in regulation of many cellular functions including DNA repair, cell cycle control, senescence and genotoxic stress. However, the pro-apoptotic activities have also positioned GADD45 as an essential player in oncogenesis. Emerging functional evidence implies that GADD45 proteins serve as tumor suppressors in response to diverse stimuli, connecting multiple cell signaling modules. Defects in the GADD45 pathway can be related to the initiation and progression of malignancies. Moreover, induction of GADD45 expression is an essential step for mediating anti-cancer activity of multiple chemotherapeutic drugs and the absence of GADD45 might abrogate their effects in cancer cells. In this review, we present a comprehensive discussion of the functions of GADD45 proteins, linking their regulation to effectors of cell cycle arrest, DNA repair and apoptosis. The ramifications regarding their roles as essential and central players in tumor growth suppression are also examined. We also extensively review recent literature to clarify how different chemotherapeutic drugs induce GADD45 gene expression and how its up-regulation and interaction with different molecular partners may benefit cancer chemotherapy and facilitate novel drug discovery.

The circadian gene expression of Per1 and Per2 and their influence on radiotherapeutic sensitivity of glioma in vitro

Per2 plays a key role in regulating the circadian rhythm in mammals. However, the circadian clock gene expression of Per1 and Per2 and its influence on radiotherapeutic sensitivity of C6 glioma cells in vitro have not been explored. Aim: To investigate the rhythm expression of circadian gene Per1 and Per2, and examine the influence on radiotherapeutic sensitivity of two important clock genes in C6 glioma cells. Materials & methods: The cultured C6 glioma cells and NIH3T3 cells were stimulated by phorbol 12-myristate 13-acetate (PMA). The expression of Per1 and Per2 at the indicated times were examined with a method for the absolute quantification of cDNA using real-time PCR. The cultured cell were given x-irradiation at the indicated times and the cell-cycle, apoptosis and proliferation were examined by flow cytometry. Results: We report here that PMA treatment of C6 rat glioma cells induces circadian expression of Per2, and that during periods of high expression, cells are blocked at the G2/M transition and are more sensitive to x-irradiation. PMA treatment of NIH3T3 cells induced circadian expression of Per1 and Per2, but high Per expression did not block the cell cycle or render the cells more sensitive to irradiation. Conclusion: Our results suggest that Per2 expression may increase the efficacy of radiotherapy against glioma.