Oxidative stress-mediated intrinsic apoptosis in human promyelocytic leukemia HL-60 cells induced by organic arsenicals

In vitro and in vivo anticancer activity of novel Rh(III) and Pd(II) complexes with pyrazolopyrimidine derivatives

Six pyrazolopyrimidine rhodium(III) or palladium(II) complexes, [Rh(L1)(H2O)Cl3] (1), [Rh(L2)(CH3OH)Cl3] (2), [Rh(L3)(H2O)Cl3] (3), [Rh2(L4)Cl6]·CH3OH (4), [Rh(L5)(CH3CN)Cl3]·0.5CH3CN (5), and [Pd(L5)Cl2] (6), were synthesized and characterized. These complexes showed high cytotoxicity against six tested cancer cell lines. Most of the complexes showed higher cytotoxicity to T-24 cells in vitro than cisplatin. Mechanism studies indicated that complexes 5 and 6 induced G2/M phase cell cycle arrest through DNA damage, and induced apoptosis via endoplasmic reticulum stress response. In addition, complex 5 also induced cell apoptosis via mitochondrial dysfunction. Complexes 5 and 6 showed low in vivo toxicity and high tumor growth inhibitory activity in mouse tumor models. The inhibitory effect of rhodium complex 5 on tumor growth in vivo was more pronounced than that of palladium complex 6.

Arsenic in medicine: past, present and future

Arsenicals are one of the oldest treatments for a variety of human disorders. Although infamous for its toxicity, arsenic is paradoxically a therapeutic agent that has been used since ancient times for the treatment of multiple diseases. The use of most arsenic-based drugs was abandoned with the discovery of antibiotics in the 1940s, but a few remained in use such as those for the treatment of trypanosomiasis. In the 1970s, arsenic trioxide, the active ingredient in a traditional Chinese medicine, was shown to produce dramatic remission of acute promyelocytic leukemia similar to the effect of all-trans retinoic acid. Since then, there has been a renewed interest in the clinical use of arsenicals. Here the ancient and modern medicinal uses of inorganic and organic arsenicals are reviewed. Included are antimicrobial, antiviral, antiparasitic and anticancer applications. In the face of increasing antibiotic resistance and the emergence of deadly pathogens such as the severe acute respiratory syndrome coronavirus 2, we propose revisiting arsenicals with proven efficacy to combat emerging pathogens. Current advances in science and technology can be employed to design newer arsenical drugs with high therapeutic index. These novel arsenicals can be used in combination with existing drugs or serve as valuable alternatives in the fight against cancer and emerging pathogens. The discovery of the pentavalent arsenic-containing antibiotic arsinothricin, which is effective against multidrug-resistant pathogens, illustrates the future potential of this new class of organoarsenical antibiotics.

125I seed implantation enhances arsenic trioxide-induced apoptosis and anti-angiogenesis in lung cancer xenograft mice

BACKGROUND AND PURPOSE

Arsenic trioxide (ATO) exerts anticancer effects on lung cancer. However, the clinical use of ATO is limited due to its systemic toxicity and resistance of lung cancer cells. The present study aimed to investigate the effects of ATO, alone and in combination with ¹²⁵I seed implantation on tumor growth and proliferation in lung cancer xenograft mice, and investigate the possible molecular mechanisms.

METHODS

The transmission electron microscope observed the tumor ultrastructure of lung cancer xenograft mice. The proliferation index of Ki-67 and the number and morphology of tumor microvessels were detected with immunohistochemical staining. The protein and mRNA expression were examined by western blot and real-time PCR assay.

RESULTS

The in vivo results demonstrated that ATO combined with ¹²⁵I seed significantly inhibited tumor growth and proliferation, as well as promoted apoptosis, and decreased the Ki-67 index and microvessel density in lung cancer xenograft mice. Moreover, ATO combined with ¹²⁵I seed decreased the protein and mRNA expression levels of HIF-1α, VEGF, and BCL-2, and increased those of BAX and P53.

CONCLUSIONS

ATO combined with ¹²⁵I seed significantly inhibited tumor growth and proliferation in lung cancer, which may be accomplished by inhibiting tumor angiogenesis and inducing apoptosis.

A novel organic arsenic derivative MZ2 remodels metabolism and triggers mtROS-mediated apoptosis in acute myeloid leukemia

PURPOSE

Acute myeloid leukemia (AML) is one of the most common neoplasms in adults, and it is difficult to achieve satisfactory results with conventional drugs. Here, we synthesized a novel organic arsenic derivative MZ2 and evaluated its ability to remodel energy metabolism to achieve anti-leukemia.

METHODS

MZ2 was characterized by the average 1-min full mass spectra analysis. Biological methods such as Western blot, qPCR, flow cytometry and confocal microscopy were used to assess the mode and mechanism of MZ2-induced death. The in vivo efficacy of MZ2 was assessed by constructing a patient-derived xenograft (PDX) AML model.

RESULTS

Unlike the precursor organic arsenical Z2, MZ2 can effectively reduce the level of aerobic glycolysis. Our in-depth found that MZ2 inhibited the expression of PDK2 in a dose-dependent manner and did not affect the expression of LDHA, another key enzyme of the glycolytic pathway. MZ2 reconstituted energy metabolism to induce the generation of mitochondrial ROS (mtROS) and then triggerd intrinsic apoptosis pathway. We also assessed whether MZ2 generates autophagy and results showed that MZ2 can induce autophagy of AML cells, which may be associated with the precursor organic arsenic drug. In vivo, MZ2 effectively attenuated leukemia progression in mice, and immunohistochemical results suggested its PDK2 inhibitory effect.

CONCLUSION

In summary, the novel organic arsine derivative MZ2 exhibited excellent anti-tumor effects in acute myeloid leukemia, which may provide a potential strategy for the treatment of acute myeloid leukemia.

Carnosic Acid Suppresses the Development of Oral Squamous Cell Carcinoma via Mitochondrial-Mediated Apoptosis

Oral squamous cell carcinoma (OSCC) predominantly consists of squamous cells and is the tumor with the highest incidence of the head and neck. Carnosic acid (CA), a natural monomer drug obtained from rosemary and salvia, shows various pharmacological effects, including of tumor development. This study aimed to assess for an effect of CA on the development of OSCC and the underlying mechanisms. In CAL27 and SCC9 cells, CA inhibited cell proliferation and migration, increased intracellular levels of reactive oxygen species (ROS) and Ca²⁺, decreased the mitochondrial membrane potential (MMP), and promoted apoptosis. In CAL27- and SCC9-xenotransplanted BALB/c nude mice, CA inhibited the tumor growth without affecting the body weight and tissue morphology. CA upregulated Bax, Bad, cleaved Caspase-3 and -9 levels, and the cleaved PARP1/PARP1 ratio but downregulated Bcl-2 in CA-treated OSCC cells and OSCC cells-xenotransplanted BALB/c nude mice. These results indicate that CA suppresses OSCC at least via the mitochondrial apoptotic pathway and offers this natural compound as a potential therapeutic against OSCC.

Structural Modification of Aminophenylarsenoxides Generates Candidates for Leukemia Treatment via Thioredoxin Reductase Inhibition

Upregulation of the selenoprotein thioredoxin reductase (TrxR) is of pathological significance in maintaining tumor phenotypes. Thus, TrxR inhibitors are promising cancer therapeutic agents. We prepared different amino-substituted phenylarsine oxides and evaluated their cytotoxicity and inhibition of TrxR. Compared with our reported p-substituted molecule (8), the o-substituted molecule (10) shows improved efficacy (nearly a fourfold increase) to kill leukemia HL-60 cells. Although the compounds 8 and 10 display similar potency to inhibit the purified TrxR, the o-substitution 10 exhibits higher potency than the p-substitution 8 to inhibit the cellular TrxR activity. Molecular docking results demonstrate the favorable weak interactions of the o-amino group with the TrxR C-terminal active site. Efficient inhibition of TrxR consequently induces the oxidative stress-mediated apoptosis of cancer cells. Silence of the TrxR expression sensitizes the cells to the arsenic compound treatment, further supporting the critical involvement of TrxR in the cellular actions of compound 10.

Oxidative stress in leukemia and antioxidant treatment

Oxidative stress is caused by the imbalance between the generation of free radicals/reactive oxygen species (ROS) and the antioxidant defense systems, which can activate various transcription factors and affect their transcriptional pathways. Oxidative stress plays an important role in the occurrence and development of leukemia and is closely related to the treatment and prognosis of leukemia. The standard chemotherapy strategies for the pre-treatment of leukemia have many drawbacks. Hence, the usage of antioxidants and oxidants in the treatment of leukemia is being explored and has been preliminarily applied. This article reviews the research progress of oxidative stress and leukemia. In addition, the application of antioxidants treatment in leukemia has been summarized.

A novel dual MEK/PDK1 inhibitor 9za retards the cell cycle at G0/G1 phase and induces mitochondrial apoptosis in non-small cell lung cancer cells

Background

A novel dual MEK/PDK1 inhibitor named 9za has been synthesized by our research team. Preliminary study showed that 9za possessed potent cytotoxicity and proapoptosis in non-small cell lung cancer (NSCLC) cells. Nevertheless, the precise underlying mechanism is vague.

Methods

In this work, we adopted the MTT assay, the Cell Cycle Detection Kit, and the JC-1 staining assay to detect the cell viability, the cell cycle distribution and the mitochondrial membrane potential (MMP), respectively. Cell apoptosis was measured by the morphology observation under a light microscope, Annexin V-FITC/propidium iodide (PI) apoptosis detection and the colorimetric TUNEL assay. Western blot was used to monitor the cell cycle-, apoptosis-related proteins and relevant proteins involved in the signaling pathways.

Results

The MTT assay demonstrated that 9za sharply decreased the viability of NSCLC cells. Cell cycle analysis revealed that low concentrations of 9za arrested the cell cycle at the G₀/G₁ phase , which was further confirmed by the decreased levels of Cyclin D1, cyclin-dependent kinase 4 (CDK4) and cyclin-dependent kinase 6 (CDK6). Additionally, morphological observations, Annexin V-FITC/propidium iodide (PI) apoptosis analysis and TUNEL assays indicated that high concentrations of 9za induced cell apoptosis. Furthermore, the JC-1 staining assay revealed that the mitochondrial membrane potential was downregulated following 9za exposure. Western blot also showed that 9za markedly decreased the expression levels of total Bcl-2, Cytochrome C in the mitochondria and BCL2 associated X (BAX) in the cytoplasm. However, the levels of BAX in the mitochondria, Cytochrome C in the cytoplasm, active caspase-9, active caspase-3 and cleaved–PARP showed the opposite changes. Moreover, the dose-dependent decreased phosphorylation levels of PDK1, protein kinase B (Akt), MEK and extracellular signal regulated kinase 1/2 (ERK1/2) after 9za treatment verified that 9za was indeed a dual MEK/PDK1 inhibitor, as we expected. Compared with a single MEK inhibitor PD0325901 or a single PDK1 inhibitor BX517, the dual MEK/PDK1 inhibitor 9za could strengthen the cytotoxic and proapoptotic effect, indicating that the double blocking of the MEK and PDK1 signaling pathways plays stronger cell growth inhibition and apoptosis induction roles than the single blocking of the MEK or PDK1 signaling pathway in NSCLC cells. Our work elucidated the molecular mechanisms for 9za as a novel drug candidate against NSCLC.

Synthesis, characterization, and antitumor properties of Au(i)–thiourea complexes

The complex Au(i)(3c)2OTf induced the ROS elevation and mitochondria-mediated apoptosis in a synergistic manner.

The novel thioredoxin reductase inhibitor A-Z2 triggers intrinsic apoptosis and shows efficacy in the treatment of acute myeloid leukemia

Chemoresistance and high incidence of relapse in acute myeloid leukemia (AML) patients are associated with thioredoxin (Trx) overexpression. Thus, targeting the Trx system has emerged as a promising approach to treating AML. Both arsenicals and azelaic acid (AZA) are thioredoxin reductase (TrxR) inhibitors and possess antileukemic effects. In this study, to exploit agents with higher potency and lower toxicity, we got some organic arsenicals and further synthesized a series of targeted compounds by binding AZA to organic arsenicals, and then screened the most effective one, N-(4-(1, 3, 2-dithiarsinan-2-yl) phenyl)-azelamide (A-Z2). A-Z2 showed a stronger inhibitory effect against TrxR activity and in AML cell lines than did AZA or arsenicals. Additionally, A-Z2 was less toxic to healthy cells compared with traditional chemotherapeutic drugs. A-Z2 induces apoptosis by collapsing of mitochondrial membrane potential, reducing ATP level, releasing of cytochrome c and TNF-α, activating of caspase 9, 8 and 3. Analysis of the mechanism revealed that A-Z2 activates the intrinsic apoptotic pathway by directly selectively targeting TrxR/Trx and indirectly inhibiting NF-κB. A-Z2's better efficacy and safety profile against arsenicals and azelaic acid were also evident in vivo. A-Z2 had better plasma stability and biological activity in rats. A-Z2-treated mice displayed significant symptom relief and prolonged survival in a patient-derived xenograft (PDX) AML model. Herein, our study provides a novel antitumor candidate and approach for treating AML.

LDHA Suppression Altering Metabolism Inhibits Tumor Progress by an Organic Arsenical

Based on the potential therapeutic value in targeting metabolism for the treatment of cancer, an organic arsenical PDT-BIPA was fabricated, which exerted selective anti-cancer activity in vitro and in vivo via targeting lactate dehydrogenase A (LDHA) to remodel the metabolic pathway. In details, the precursor PDT-BIPA directly inhibited the function of LDHA and converted the glycolysis to oxidative phosphorylation causing ROS burst and mitochondrial dysfunction. PDT-BIPA also altered several gene expression, such as HIF-1α and C-myc, to support the metabolic remodeling. All these changes lead to caspase family-dependent cell apoptosis in vivo and in vitro without obvious side effect. Our results provided this organic arsenical precursor as a promising anticancer candidate and suggested metabolism as a target for cancer therapies.

A mitochondria-targeted organic arsenical accelerates mitochondrial metabolic disorder and function injury

Considering the vital role of mitochondria in the anti-cancer mechanism of organic arsenical, the mitochondria-targeted precursor PDT-PAO-TPP was designed and synthesized. PDT-PAO-TPP, as a delocalization lipophilic cation (DLCs) which mainly accumulated in mitochondria, contributed to improve anti-cancer efficacy and selectivity towards NB4 cells. In detail, PDT-PAO-TPP inhibited the activity of PDHC resulting in the suppression of ATP synthesis and thermogenesis disorder. Additionally, the inhibition of respiratory chain complex I and IV by short-time incubation of PDT-PAO-TPP also accelerated the respiration dysfunction and continuous generation of ROS. These results led to the release of cytochrome c and activation of caspase family-dependent apoptosis. Different from the mechanism of PDT-PAO in HL-60 cells, it mainly induced the mitochondrial metabolic disturbance resulting in the intrinsic apoptosis via inhibiting the activity of PDHC in NB4 cells, which also implied that the efficacy exertion of organic arsenical was a complex process involved in many aspects of cellular function. This study systematically clarifies the anti-cancer mechanism of mitochondria-targeted organic arsenical PDT-PAO-TPP and confirms the new target PDHC of organic arsenicals, which further supports the organic arsenical as a promising anticancer drug.

In vitro modulation of mercury-induced rat liver mitochondria dysfunction

Mercury (Hg) is a toxic environmental pollutant that exerts its cytotoxic effects as cations by targeting mitochondria. In our work, we determined different mitochondrial toxicity factors using specific substrates and inhibitors following the addition of Hg2+ to the mitochondria isolated from Wistar rat liver in vitro. We found that Hg2+ induced marked changes in the mitochondrial ultrastructure accompanied by mitochondrial swelling, mitochondrial membrane potential collapse, mitochondrial membrane fluidity increase and Cytochrome c release. Additionally, the effects of Hg2+ on heat production of mitochondria were investigated using microcalorimetry; simultaneously, the effects on mitochondrial respiration were determined by Clark oxygen-electric methods. Microcalorimetry could provide detailed kinetic and thermodynamic information which demonstrated that Hg2+ had some biotoxicity effect on mitochondria. The inhibition of energy metabolic activities suggested that high concentrations of Hg2+ could induce mitochondrial ATP depletion under MPT and mitochondrial respiration inhibition. These results help us learn more about the toxicity of Hg2+ at the subcellular level.

Mitochondrial morphology and function impaired by dimethyl sulfoxide and dimethyl Formamide

In this work, the effects of two non-ionic, non-hydroxyl organic solvents, dimethyl sulfoxide (DMSO) and dimethyl formamide (DMF) on the morphology and function of isolated rat hepatic mitochondria were investigated and compared. Mitochondrial ultrastructures impaired by DMSO and DMF were clearly observed by transmission electron microscopy. Spectroscopic and polarographic results demonstrated that organic solvents induced mitochondrial swelling, enhanced the permeation to H⁺/K⁺, collapsed the potential inner mitochondrial membrane (IMM), and increased the IMM fluidity. Moreover, with organic solvents addition, the outer mitochondrial membrane (OMM) was broken, accompanied with the release of Cytochrome c, which could activate cell apoptosis signaling pathway. The role of DMSO and DMF in enhancing permeation or transient water pore formation in the mitochondrial phospholipid bilayer might be the main reason for the mitochondrial morphology and function impaired. Mitochondrial dysfunctions induced by the two organic solvents were dose-dependent, but the extents varied. Ethanol (EtOH) showed the highest potential damage on the mitochondrial morphology and functions, followed by DMF and DMSO.

Carbohydrate-conjugated 4-(1,3,2-dithiarsolan-2-yl)aniline as a cytotoxic agent against colorectal cancer

Arsenic trioxide (As₂O₃) has been approved for the treatment of acute promyelocytic leukemia (APL); however, its use in the treatment of solid tumors is limited due to its pharmacokinetic properties. Organic arsenic compounds provide better options for pharmaceutical optimization. p-Aminophenyl arsenoxide (p-APAO), an organic arsenic compound, was found to interact with the promyelocytic leukemia–retinoic acid receptor alpha (PML–RARα) fusion protein in a similar manner to arsenic trioxide. Analogs of p-APAO such as 4-(1,3,2-dithiarsolan-2-yl)aniline (p-APDTAs) were recently found to show improved cytotoxicity toward several solid tumor cell lines with lower toxicity to normal cells. Here, we synthesized a carbohydrate-conjugated 4-(1,3,2-dithiarsolan-2-yl)aniline (p-APDTAs) and showed that it exhibited reduced cytotoxicity to normal cells, suggesting a feasible approach to improve the therapeutic index of arsenic-containing compounds as chemotherapeutic agents.

We synthesized a carbohydrate-conjugated 4-(1,3,2-dithiarsolan-2-yl)aniline. It exhibited reduced cytotoxicity to normal cells, suggesting a feasible approach to improve the therapeutic index of arsenic-containing compounds as chemotherapeutic agents.

Mitochondrial toxicity of organic arsenicals: membrane permeability transition pore opening and respiratory dysfunction

In order to clarify the mitochondrial toxicity mechanism of the organic arsenical MOPIMP (2-methoxy-4-(((4-(oxoarsanyl) phenyl) imino) methyl) phenol), research was carried out at the sub-cell level based on the previous finding that the compound MOPIMP can damage the mitochondria by triggering a burst of ROS. After investigating its influence on isolated mitochondria in vitro, it was demonstrated that a high dose of MOPIMP with short-term exposure can induce mitochondrial swelling, decrease the membrane potential, enhance the permeability of H⁺ and K⁺, and induce membrane lipid peroxidation, indicating that it can result in an MPT process in a ROS-mediated and Ca²⁺-independent manner. Additionally, MPT was also aggravated as a result of impairment of the membrane integrity and membrane fluidity. In addition, short-term incubation between mitochondria and compound MOPIMP promoted the inhibition of respiratory chain complexes I, II, III and IV, as well as damage to the respiration process, which supported the previous finding about the burst of ROS. On the other hand, after long-term exposure by the organic arsenical MOPIMP, mitochondrial metabolic dysfunction was triggered, which was in accordance with perturbation of the respiratory chain complexes as well as the respiration process. This work systematically sheds light on the mitochondrial toxicity mechanism of the organic arsenical MOPIMP, including induction of the MPT process and inhibition of respiratory metabolism, which provides a potential target for organic arsenicals as anti-tumor drugs.

Toxicity of Pb2+ on rat liver mitochondria induced by oxidative stress and mitochondrial permeability transition

Pb2+ exposure in humans occurs mainly through air inhalation, food and water uptake which has been shown to be generally associated with numerous body functions such as the central and peripheral nervous systems, the red blood cells, the kidneys and the liver. It has been reported that the liver is the storage site and an important primary target in Pb2+ toxicity, and the hepatotoxicity of Pb2+ could be resulted from the impairment of the liver mitochondria. In this study, several mitochondrial dysfunctions following the addition of Pb2+ (10-160 μM) were investigated. We found that Pb2+ inhibited the enzyme activities of mitochondrial respiratory complexes and complex III was the major source of Pb2+-induced significant reactive oxygen species (ROS) formation. As a consequence, our results showed that Pb2+ induced significant progress in mitochondrial lipid peroxidation, adenosine triphosphate (ATP) consumption and glutathione (GSH) oxidation. On the other hand, Pb2+ induced marked changes in mitochondrial permeability transition (MPT) accompanied by mitochondrial swelling, mitochondrial membrane potential collapse, mitochondrial membrane fluidity decrease and cytochrome c (Cyt c) release. Additionally, several mitochondrial MPT inhibitors and chelators were utilized to determine the possible interaction sites of Pb2+ on mitochondria. In general, our data supported that the Pb2+-induced liver toxicity was a result of the disruptive effect on the mitochondrial respiratory complexes. This disruptive effect caused oxidative stress and MPT, which led to mitochondrial dysfunctions and even cell death signalling via mitochondrial permeability transition pore (MPTP) opening and Cyt c release.

Dihydroartemisinin Sensitizes Human Lung Adenocarcinoma A549 Cells to Arsenic Trioxide via Apoptosis

Recent studies have shown that arsenic trioxide (ATO) is an effective anti-cancer drug for treatment of acute promyelocytic leukemia and other types of human cancer. However, we have found that lung cancer cells constantly develop a high level of resistance to ATO. In this study, we have explored a possibility of combination of dihydroartemisinin (DHA) and ATO treatments to reduce ATO resistance of lung cancer cells. We determined the combinatory effects of DHA and ATO on cytotoxicity of human lung adenocarcinoma (A549) cells. We showed that co-exposure to DHA and ATO of A549 cells synergistically increased the cytotoxicity and apoptotic cell death in the cells. We found that the synergistic effect of DHA and ATO in promoting apoptosis mainly resulted from increased cellular level of reactive oxygen species (ROS) and DNA damage. ATO alone only exerted moderate growth inhibitory effects on A549 cells. The results indicate that DHA can significantly sensitize ATO-induced cytotoxicity of A549 lung cancer cells through apoptosis mediated by ROS-induced DNA damage. Interestingly, we found that the combinatory treatment of DHA and ATO did not result in significant adverse effects in normal human bronchial epithelial (HBE) cells. Our results further provide evidence for the potential application of combinatory effects of DHA and ATO as a safe therapy for human lung cancer.

Arsenic trioxide exposure impairs testicular morphology in adult male mice and consequent fetus viability

The acute promyelocytic leukemia (APL) is a rare disease, affecting 0.1/100,000 individuals globally. Despite significant advances in APL therapy, some patients still experience relapsed disease. Currently, arsenic trioxide (As₂O₃) was found to be effective in relapsed APL treatment and considered as standard treatment for these cases. However, it has been shown that exposure to As₂O₃ may exert adverse effects on the male reproductive system since this substance might also induce apoptosis of other important cell types including stem cells. Studies demonstrated that treatment with this metallic substance decreased plasma levels of testosterone and interfered with sperm parameters such as concentration, motility, and viability. In addition, As₂O₃ was found to produce significant damage to spermatocytes, which may be associated with testicular toxicity and consequent inhibition of spermatogenesis. The aim of this study was to determine sub-chronic treatment effects of As₂O₃ on sperm and testicular morphology, androgen receptor (AR) immunoreactivity in testes and epididymis, in addition to evaluation of fertility parameters in adult male mice. Thirty adult Swiss mice were divided into three experimental groups: control; received distilled water (vehicle) while treated received 0.3 or 3 mg/kg/day As₂O₃ subcutaneously, for 5 days per week, followed by 2 days of interruption, for 5 weeks. Results showed that As₂O₃ (1) decreased spermatozoa number, (2) produced seminiferous epithelium degeneration and exfoliation of germ cells tubule lumen (3) altered nucleus/cytoplasm proportion of Leydig cells and (4) reduced AR immunoreactivity in both Leydig and epithelial epididymal cells. Further, fetal viability tests demonstrated an increase in post-implantation loss in females that were mated with As₂O₃-treated males. Data indicate that As₂O₃ exposure altered the spermatogenic process and subsequently fetal viability.

miR-155 mediates arsenic trioxide resistance by activating Nrf2 and suppressing apoptosis in lung cancer cells

Arsenic trioxide (ATO) resistance is a challenging problem in chemotherapy. However, the underlying mechanisms remain to be elucidated. In this study, we identified a high level of expression of miR-155 in a human lung adenocarcinoma A549R cell line that is highly resistant to ATO. We showed that the high level of miR-155 was associated with increased levels of cell survival, colony formation, cell migration and decreased cellular apoptosis, and this was mediated by high levels of Nrf2, NAD(P)H quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1) and a high ratio of Bcl-2/Bax. Overexpression of the miR-155 mimic in A549R cells resulted in increased levels of colony formation and cell migration as well as reduced apoptosis along with increased Nrf2, NQO1 and HO-1. In contrast, silencing of miR-155 expression with its inhibitor in the cells, significantly decreased the cellular levels of Nrf2, NQO1 and HO-1 as well as the ratio of Bcl-2/Bax. This subsequently reduced the level of colony formation and cell migration facilitating ATO-induced apoptosis. Our results indicate that miR-155 mediated ATO resistance by upregulating the Nrf2 signaling pathway, but downregulating cellular apoptosis in lung cancer cells. Our study provides new insights into miR-155-mediated ATO resistance in lung cancer cells.

Chaetocin induces cell cycle arrest and apoptosis by regulating the ROS-mediated ASK-1/JNK signaling pathways

The present study demonstrated that chaetocin, a natural small-molecule product produced by Chaetomium fungal species and a potential anticancer agent, inhibited the viability and invasive ability of the human intrahepatic cholangio-carcinoma cell line CCLP-1 in vivo and in vitro as revealed by CCK-8 and Transwell invasion assays and mouse xenograft tumor experiments. As determined using flow cytometry and intracellular ROS assays, chaetocin was found to induce cell cycle arrest and oxidative stress, leading to CCLP-1 cell apoptosis. Cell apoptosis can be initiated via different apoptotic signaling pathways under oxidative stress. As determined by western blot analysis, expression levels of the apoptosis signal-regulating kinase 1 (ASK-1) signalosome and its downstream c-Jun N-terminal kinase (JNK) signaling pathway were increased under oxidative stress stimulation. These findings indicate that chaetocin arrests the cell cycle and induces apoptosis by regulating the reactive oxygen species-mediated ASK-1/JNK signaling pathways.

Monitoring ZEO apoptotic potential in 2D and 3D cell cultures and associated spectroscopic evidence on mode of interaction with DNA

Recognizing new anticancer compounds to improve Breast cancer treatment seems crucial. Essential oil of Zataria Multiflora (ZEO) is a secondary metabolite with some biological properties, yet underlying cellular and molecular anticancer properties of ZEO is unclear. GC/MS analysis revealed that carvacrol is the major ingredient of the essential oil. ZEO increasingly suppressed viability in MDA-MB-231, MCF-7 and T47D Breast cancer cells while nontoxic to L929 normal cells in monolayer cell cultures (2D), whereas MDA-MB-231 multicellular spheroids (3D) were more resistant to inhibition. ZEO significantly induced cell apoptosis confirmed by fluorescent staining, flow cytometry analysis and DNA fragmentation in MDA-MB-231 2D and 3D cell cultures. ZEO increased ROS generation and subsequent loss of ΔΨm, caspase 3 activation and DNA damage which consequently caused G1 and G2/M cell cycle arrest in a dose- and time-dependent manner in 2D. S phase arrest occurred in cell spheroids therefore ZEO possible DNA interaction with gDNA was investigated and revealed ZEO binds DNA via intercalation. Altogether, these data corroborate anticancer properties of ZEO and suggest that cell culture format (2D monolayer vs. 3D spheroid) plays a critical role in drug response and provides new insights into the mechanisms underlying ZEO cytotoxicity effect on Breast cancer cells.

Non-Canonical Cell Death Induced by p53

Programmed cell death is a vital biological process for multicellular organisms to maintain cellular homeostasis, which is regulated in a complex manner. Over the past several years, apart from apoptosis, which is the principal mechanism of caspase-dependent cell death, research on non-apoptotic forms of programmed cell death has gained momentum. p53 is a well characterized tumor suppressor that controls cell proliferation and apoptosis and has also been linked to non-apoptotic, non-canonical cell death mechanisms. p53 impacts these non-canonical forms of cell death through transcriptional regulation of its downstream targets, as well as direct interactions with key players involved in these mechanisms, in a cell type- or tissue context-dependent manner. In this review article, we summarize and discuss the involvement of p53 in several non-canonical modes of cell death, including caspase-independent apoptosis (CIA), ferroptosis, necroptosis, autophagic cell death, mitotic catastrophe, paraptosis, and pyroptosis, as well as its role in efferocytosis which is the process of clearing dead or dying cells.

Shikonin induces mitochondria-mediated apoptosis and enhances chemotherapeutic sensitivity of gastric cancer through reactive oxygen species

The prognosis of gastric cancer remains poor due to clinical drug resistance. Novel drugs are urgently needed. Shikonin (SHK), a natural naphthoquinone, has been reported to trigger cell death and overcome drug resistance in anti-tumour therapy. In this study, we investigated the effectiveness and molecular mechanisms of SHK in treatment with gastric cancer. In vitro, SHK suppresses proliferation and triggers cell death of gastric cancer cells but leads minor damage to gastric epithelial cells. SHK induces the generation of intracellular reactive oxygen species (ROS), depolarizes the mitochondrial membrane potential (MMP) and ultimately triggers mitochondria-mediated apoptosis. We confirmed that SHK induces apoptosis of gastric cancer cells not only in a caspase-dependent manner which releases Cytochrome C and triggers the caspase cascade, but also in a caspase-independent manner which mediates the nuclear translocation of apoptosis-inducing factor and Endonuclease G. Furthermore, we demonstrated that SHK enhanced the chemotherapeutic sensitivity of 5-fluorouracil and oxaliplatin in vitro and in vivo. Taken together, our data show that SHK may be a novel therapeutic agent in the clinical treatment of gastric cancer.