Caspase-9 mediates Puma activation in UCN-01-induced apoptosis

Evaluation of the Biological Effect of Non-UV-Activated Bergapten on Selected Human Tumor Cells and the Insight into the Molecular Mechanism of Its Action

There is some evidence that non-photoactivated psoralens may be active against breast and colon tumor cells. Therefore, we evaluated the antiproliferative, proapoptotic, and anti-migrative effect of 5-methoxypsoralen (5-MOP) isolated from Peucedanum tauricum MB fruits in human colorectal adenocarcinoma (HT-29 and SW620), osteosarcoma (Saos-2 and HOS), and multiple myeloma (RPMI8226 and U266). Dose- and cell-line-dependent effects of 5-MOP on viability and proliferation were observed, with the strongest inhibitory effect against Saos-2 and a moderate effect against the HOS, HT-29, and SW620 cells. Multiple myeloma showed low sensitivity. The high viability of human normal cell cultures (HSF and hFOB) in a wide range of 5-MOP concentrations tested (6.25-100 µM) was confirmed. Moreover, the migration of treated Saos-2, SW620, and HT-29 cell lines was impaired, as indicated via a wound healing assay. Flow cytometry analysis conducted on Saos-2 cells revealed the ability of 5-MOP to block the cell cycle in the G2 phase and trigger apoptosis, which was accompanied by a loss of mitochondrial membrane potential, caspases (-9 and -3) activation, the altered expression of the Bax and Bcl-2 proteins, and decreased AKT phosphorylation. This is the first report evaluating the antiproliferative and antimigratory impact of non-UV-activated bergapten on the abovementioned (except for HT-29) tumor cells, which provides new data on the potential role of 5-MOP in inhibiting the growth of various types of therapeutic-resistant cancers.

3-Bromopyruvate overcomes cetuximab resistance in human colorectal cancer cells by inducing autophagy-dependent ferroptosis

Colorectal cancer (CRC) remains a leading cause of cancer-related death worldwide. Cetuximab, in combination with chemotherapy, is effective for treating patients with wild-type KRAS/BRAF metastatic CRC (mCRC). However, intrinsic or acquired drug resistance often limits the use of cetuximab. In this study, we investigated the potential of co-treatment with 3-Bromopyruvate (3-BP) and cetuximab to overcome cetuximab resistance in CRC, both in vitro and in vivo. Our results demonstrated that the co-treatment of 3-BP and cetuximab synergistically induced an antiproliferative effect in both CRC cell lines with intrinsic cetuximab resistance (DLD-1 (KRASG13D/-) and HT29 (BRAFV600E)) and in a cetuximab-resistant cell line derived from Caco-2 with acquired resistance (Caco-2-CR). Further analysis revealed that co-treatment induced ferroptosis, autophagy, and apoptosis. Mechanistically, co-treatment inhibited FOXO3a phosphorylation and degradation and activated the FOXO3a/AMPKα/pBeclin1 and FOXO3a/PUMA pathways, leading to the promotion of ferroptosis, autophagy, and apoptosis in DLD-1 (KRASG13D/-), HT29 (BRAFV600E), and Caco-2-CR cells. In conclusion, our findings suggest that co-treatment with 3-BP and cetuximab could be a promising strategy to overcome cetuximab resistance in human CRC.

Therapeutic Efficacy of Carbon Ion Irradiation Enhanced by 11-MUA-Capped Gold Nanoparticles: An in vitro and in vivo Study

PURPOSE

Gold nanoparticles (AuNPs) are widely studied as radiosensitizers, but their radiosensitization in carbon ion radiotherapy is unsatisfactory. There is a lack of in vivo data on the radiosensitization of AuNPs under carbon ion irradiation. This study focused on the radiosensitization effect of AuNPs in the mouse melanoma cell line B16-F10 in vitro and in vivo.

MATERIALS AND METHODS

11-mercaptoundecanoic acid (11-MUA)-coated gold (Au) nanoparticles (mAuNPs) formulations were prepared and characterized. To verify the radiosensitization effect of mAuNPs, hydroxyl radicals were generated in aqueous solution, and the detection of intracellular reactive oxygen species (ROS) and clone survival were carried out in vitro. The tumor growth rate (TGR) and survival of mice were analyzed to verify the radiosensitization effect of mAuNPs in vivo. The apoptosis of tumor cells was detected, and the expression of key proteins in the apoptosis pathway was verified by immunohistochemistry.

RESULTS

The intracellular ROS level in B16-F10 cells was enhanced by mAuNPs under carbon ion irradiation. The sensitization rate of mAuNPs was 1.22 with a 10% cell survival rate. Compared with irradiation alone, the inhibitory effect of mAuNPs combined with carbon ion irradiation on tumor growth was 1.94-fold higher, the survival time of mice was prolonged by 1.75-fold, and the number of apoptotic cells was increased by 1.43-fold. The ratio of key proteins Bax and Bcl2 in the apoptosis pathway was up-regulated, and the expression of caspase-3, a key executor of the apoptosis pathway, was up-regulated.

CONCLUSION

In in vivo and in vitro experiments, mAuNPs showed radiosensitivity to carbon ion irradiation. The sensitization effect of mAuNPs on mice tumor may be achieved by activating the mitochondrial apoptosis pathway and increasing tumor tissue apoptosis. To our best knowledge, the present study is the first in vivo evidence for radiosensitization of mAuNPs in tumor-bearing mice exposed to carbon ion irradiation.

Molecular mechanisms underlying antitumor activity of camel whey protein against multiple myeloma cells

Treating drug-resistant cancer cells is a clinical challenge and it is also vital to screen for new cancer drugs. Multiple myeloma (MM) is a plasma cell clonal cancer that, despite many experimental therapeutics, remains incurable. In this study, two MM cell line lines U266 and RPMI 8226 were used to determine the impact of camel whey protein (CWP). The CWP IC₅₀ was calculated by MTT examination, while the flow cytometry analysis was used to investigate the chemotaxis responses of MM cells in relation to CXCL12 and the pro-apoptotic effect of CHP. MM cells were treated with CWP and Western blot analysis was used to determine the underlying molecular mechanisms. Dose and time based on the impact of CWP on the cell viability of MM cells with IC₅₀ of 50 μg/ml, without affecting the viability of normal healthy PBMCs. CWP reduced chemotaxis of MM cells significantly from the CXC chemokine ligand 12 (CXCL12). Using Western blot analysis, we found that CWP decreased the activation of AKT, mTOR, PLCβ3, NFαB and ERK, which was mechanistically mediated by CXCL12/CXCR4. In both U266 and RPMI 8226, CWP induced apoptosis by upregulating cytochrome C expression. In addition, CWP mediated the growth arrest of MM cells by robustly decreasing the expression of the anti-apoptotic Bcl-2 family members Bcl-2, Bcl-XL and Mcl-1. Conversely, the expression of pro-apoptotic Bcl-2 family members Bak, Bax and Bim was increased after treatment with CWP. Our data indicates CWP's therapeutic potential for MM cells.

Challenges and Therapeutic Opportunities of Autophagy in Cancer Therapy

Simple Summary

Autophagy is a physiological process characterized by the degradation of the cell components through lysosomes due to stimuli/stress. In this study, we review the challenges and therapeutic opportunities that autophagy presents in the treatment of cancer. We discussed the results of several studies that evaluated autophagy as a therapeutic strategy in cancer, both through the modulation of therapeutic resistance and the death of cancer cells. Moreover, we discussed the role of autophagy in the biology of cancer stem cells and the inhibition of this process as a strategy to overcome resistance and progression of cancer stem cells.

Abstract

Autophagy is a physiological cellular process that is crucial for development and can occurs in response to nutrient deprivation or metabolic disorders. Interestingly, autophagy plays a dual role in cancer cells—while in some situations, it has a cytoprotective effect that causes chemotherapy resistance, in others, it has a cytotoxic effect in which some compounds induce autophagy-mediated cell death. In this review, we summarize strategies aimed at autophagy for the treatment of cancer, including studies of drugs that can modulate autophagy-mediated resistance, and/or drugs that cause autophagy-mediated cancer cell death. In addition, the role of autophagy in the biology of cancer stem cells has also been discussed.

1, 6-O, O-Diacetylbritannilactone from Inula britannica Induces Anti-Tumor Effect on Oral Squamous Cell Carcinoma via miR-1247-3p/LXRα/ABCA1 Signaling

Introduction

Oral squamous cell carcinoma (OSCC) is the most prevalent malignancy affecting the oral cavity and is associated with severe morbidity and high mortality. 1, 6-O, O-Diacetylbritannilactone (OODBL) isolated from the medicinal herb of Inula britannica has various biological activities such as anti-inflammation and anti-cancer. However, the effect of OODBL on OSCC progression remains unclear. Here, we were interested in the function of OODBL in the development of OSCC.

Methods

The effect of OODBL on OSCC progression was analyzed by MTT assays, colony formation assays, transwell assays, apoptosis analysis, cell cycle analysis, and in vivo tumorigenicity analysis. The mechanism investigation was performed by qPCR assays, Western blot analysis, and luciferase reporter gene assays.

Results

We found that OODBL inhibits the proliferation of OSCC cells in vitro. Moreover, the migration and invasion were attenuated by OODBL treatment in the OSCC cells. OODBL arrested cells at the G0/G1 phase and induced cell apoptosis. OODBL was able to up-regulate the expression of LXRα, ABCA1, and ABCG1 in the system. In addition, OODBL activated LXRα/ABCA1 signaling by targeting miR-1247-3p. Furthermore, the expression levels of cytochrome c in the cytoplasm, cleaved caspase-9, and cleaved caspase-3 were dose-dependently reduced by OODBL. Besides, OODBL increased the expression ratio of Bax to Bcl-2. Moreover, OODBL repressed tumor growth of OSCC cells in vivo.

Discussion

Thus, we conclude that OODBL inhibits OSCC progression by modulating miR-1247-3p/LXRα/ABCA1 signaling. Our finding provides new insights into the mechanism by which OODBL exerts potent anti-tumor activity against OSCC. OODBL may be a potential anti-tumor candidate, providing a novel clinical treatment strategy of OSCC.

1-(4-((5-chloro-4-((2-(isopropylsulfonyl)phenyl)amino)pyrimidin-2-yl)amino)-3-methoxyphenyl)-3-(2-(dimethylamino)ethyl)imidazolidin-2-one (ZX-42), a novel ALK inhibitor, induces apoptosis and protective autophagy in H2228 cells

OBJECTIVES

To examine the antiproliferative effects of 1-(4-((5-chloro-4-((2-(isopropylsulfonyl)phenyl)amino)pyrimidin-2-yl)amino)-3-methoxyphenyl)-3-(2-(dimethylamino)ethyl)imidazolidin-2-one (ZX-42) on the echinoderm microtubule-associated protein-4/anaplastic lymphoma kinase fusion gene (EML4-ALK) positive lung cancer cell line H2228 and its underlying mechanism.

METHODS

The MTT assay was used to study the effect of ZX-42 on H2228 cell growth. Propidium iodide (PI) staining and Western blotting were used to investigate the cell cycle changes. ZX-42-induced cell apoptosis was determined using the Annexin V-FITC/PI (AV/PI) apoptotic assay kit, acridine orange/ethidium bromide (AO/EB) and Hoechst 33258 staining, Rhodamine 123 (Rh 123) fluorescence assay and Western blotting. ZX-42-induced reactive oxygen species (ROS) production was examined by ROS assay kit. Transmission electron microscope, monodansylcadaverine (MDC) staining and the AV/PI apoptotic assay kit were used to demonstrate the relationship between autophagy and apoptosis.

KEY FINDINGS

ZX-42 had good cell viability inhibitory effect on H2228 cells. ZX-42 dramatically inhibited ALK and its downstream pathways. ZX-42 also blocked H2228 cell cycle at G1 phase and then induced apoptosis by activating the mitochondrial pathway. Next, ZX-42 induced the production of ROS, and antioxidant N-acetylcysteine (NAC) reduced ROS production and also decreased apoptotic rates. We also found that ZX-42 induced protective autophagy in H2228 cells.

CONCLUSIONS

In summary, ZX-42 is a novel ALK inhibitor that significantly inhibits the cell viability of H2228 cells and ultimately induces apoptosis through the mitochondrial pathway, in which autophagy plays a protective role. Therefore, inhibition of autophagy might enhance the anti-cancer effect of ZX-42.

The regulatory role of HIF-1 in tubular epithelial cells in response to kidney injury

The high sensitivity to changes in oxygen tension makes kidney vulnerable to hypoxia. Both acute kidney injury and chronic kidney disease are almost always accompanied by hypoxia. Tubular epithelial cells (TECs), the dominant intrinsic cells in kidney tissue, are believed to be not only a victim in the pathological process of various kidney diseases, but also a major contributor to kidney damage. Hypoxia inducible factor-1 (HIF-1) is the main regulator of adaptive response of cells to hypoxia. Under various clinical and experimental kidney disease conditions, HIF-1 plays a pivotal role in modulating multiple cellular processes in TECs, including apoptosis, autophagy, inflammation, metabolic pattern alteration, and cell cycle arrest. A comprehensive understanding of the mechanisms by which HIF-1 regulates these cellular processes in TECs may help identify potential therapeutic targets to improve the outcome of acute kidney injury and delay the progression of chronic kidney disease.

Pyrin dephosphorylation is sufficient to trigger inflammasome activation in familial Mediterranean fever patients

Familial Mediterranean fever (FMF) is the most frequent hereditary systemic autoinflammatory syndrome. FMF is usually caused by biallelic mutations in the MEFV gene, encoding Pyrin. Conclusive genetic evidence lacks for about 30% of patients diagnosed with clinical FMF. Pyrin is an inflammasome sensor maintained inactive by two kinases (PKN1/2). The consequences of MEFV mutations on inflammasome activation are still poorly understood. Here, we demonstrate that PKC superfamily inhibitors trigger inflammasome activation in monocytes from FMF patients while they trigger a delayed apoptosis in monocytes from healthy donors. The expression of the pathogenic p.M694V MEFV allele is necessary and sufficient for PKC inhibitors (or mutations precluding Pyrin phosphorylation) to trigger caspase‐1‐ and gasdermin D‐mediated pyroptosis. In line with colchicine efficacy in patients, colchicine fully blocks this response in FMF patients’ monocytes. These results indicate that Pyrin inflammasome activation is solely controlled by Pyrin (de)phosphorylation in FMF patients while a second control mechanism restricts its activation in healthy donors/non‐FMF patients. This study paves the way toward a functional characterization of MEFV variants and a functional test to diagnose FMF.

A genome-wide screen identifies IRF2 as a key regulator of caspase-4 in human cells

Caspase-4, the cytosolic LPS sensor, and gasdermin D, its downstream effector, constitute the non-canonical inflammasome, which drives inflammatory responses during Gram-negative bacterial infections. It remains unclear whether other proteins regulate cytosolic LPS sensing, particularly in human cells. Here, we conduct a genome-wide CRISPR/Cas9 screen in a human monocyte cell line to identify genes controlling cytosolic LPS-mediated pyroptosis. We find that the transcription factor, IRF2, is required for pyroptosis following cytosolic LPS delivery and functions by directly regulating caspase-4 levels in human monocytes and iPSC-derived monocytes. CASP4, GSDMD, and IRF2 are the only genes identified with high significance in this screen highlighting the simplicity of the non-canonical inflammasome. Upon IFN-γ priming, IRF1 induction compensates IRF2 deficiency, leading to robust caspase-4 expression. Deficiency in IRF2 results in dampened inflammasome responses upon infection with Gram-negative bacteria. This study emphasizes the central role of IRF family members as specific regulators of the non-canonical inflammasome.

Knockdown MTMR14 promotes cell apoptosis and inhibits migration in liver cancer cells

Myotubularin-related protein 14 (MTMR14) is a member of the myotubularin (MTM)-related protein family and plays a key role in cardiomyopathy and autophagy. However, its potential implication in human cancer is unclear. In this study, we have investigated the expression profile of MTMR14 and its functional impact in liver cancer for the first time. Expression analysis by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry demonstrated that MTMR14 expression is obviously overexpressed in liver cancer, and positively correlated with clinical stage. A loss-of-function study showed that knockdown of MTMR14 promotes cell apoptosis and inhibits cell migration. MTMR14 knockdown also inhibits tumor migration in vivo in liver cancer peritoneal implantation nude mouse model. A molecular mechanistic study by western blot showed that Knockdown MTMR14 causes downregulation of N-cadherin and E-cadherin, and promotes the cleavage and activation of caspase12, caspase9 and caspase3, but excluding caspase8. These results suggest that MTMR14 affects cell migration through N-cadherin and E-cadherin. Additionally, MTMR14 affects cell apoptosis through mitochondrial pathway but not the death receptor pathway. Herein, our results indicate MTMR14 could have an oncogenic role in human liver cancer and thus demonstrates its potential as a target for the diagnosis and/or treatment of liver cancer.

Chromogranin-A Regulates Macrophage Function and the Apoptotic Pathway in Murine DSS colitis

Chromogranin-A (CHGA) is elevated in inflammatory bowel disease (IBD), but little is known about its role in colonic inflammation. IBD is associated with impaired functions of macrophages and increased apoptosis of intestinal epithelial cells. We investigated CHGA expression in human subjects with active ulcerative colitis (UC) and the underlying mechanisms in Chga ^-/- mice. In UC, CHGA, classically activated macrophage (M1) markers, caspase-3, p53, and its associated genes were increased, while alternatively activated macrophage (M2) markers were decreased without changes in the extrinsic apoptotic pathway. CHGA correlated positively with M1 and the apoptotic pathway and negatively with M2. In the murine dextran sulfate sodium (DSS)-induced colitis, Chga deletion reduced the disease severity and onset, pro-inflammatory mediators, M1, and p53/caspase-3 activation, while it upregulated anti-inflammatory cytokines and M2 markers with no changes in the extrinsic apoptotic markers. Compared to Chga ^+/+ , M1 and p53/caspase-3 activation in Chga ^-/- macrophages were decreased in vitro, while M2 markers were increased. CHGA plays a critical role during colitis through the modulation of macrophage functions via the caspase-3/p53 pathway. Strategies targeting CHGA to regulate macrophage activation and apoptosis might be developed to treat UC patients.

KEY MESSAGES

• Chromogranin-A (CHGA) is pro-hormone and is secreted in the gut. CHGA is elevated in colitis and is associated with the disease severity. The lack of GHGA has beneficial immunomodulatory properties during the development of intestinal inflammation. The lack of CHGA regulates the plasticity of macrophages and p53/caspase activation in colitis. Functional analysis of CHGA may lead to a novel therapy for IBD.

Crosstalk between p38 MAPK and caspase-9 regulates mitochondria-mediated apoptosis induced by tetra-α-(4-carboxyphenoxy) phthalocyanine zinc photodynamic therapy in LoVo cells

Photodynamic therapy (PDT) is considered to be an advancing antitumor technology. PDT using hydrophilic/lipophilic tetra-α-(4-carboxyphenoxy) phthalocyanine zinc (TαPcZn-PDT) has exhibited antitumor activity in Bel-7402 hepatocellular cancer cells. However, the manner in which p38 MAPK and caspase-9 are involved in the regulation of mitochondria-mediated apoptosis in the TαPcZn-PDT-treated LoVo human colon carcinoma cells remains unclear. Therefore, in the present study, a siRNA targeting p38 MAPK (siRNA-p38 MAPK) and the caspase-9 specific inhibitor z-LEHD-fmk were used to examine the crosstalk between p38 MAPK and caspase-9 during mitochondria-mediated apoptosis in the TαPcZn-PDT-treated LoVo cells. The findings revealed that the TαPcZn-PDT treatment of LoVo cells resulted in the induction of apoptosis, the formation of p38 MAPK/caspase-9 complexes, the activation of p38 MAPK, caspase-9, caspase-3 and Bid, the downregulation of Bcl-2, the reduction of mitochondrial membrane potential (ΔΨm), the upregulation of Bax and the release of apoptosis-inducing factor (AIF) and cytochrome c (Cyto c). By contrast, siRNA-p38 MAPK or z-LEHD-fmk both attenuated the effects of TαPcZn-PDT in the LoVo cells. Furthermore, the results revealed that siRNA-p38 MAPK had more significant inhibitory effects on apoptosis and mitochondria compared with the effects of z-LEHD-fmk in TαPcZn-PDT-treated LoVo cells. These findings indicated that p38 MAPK plays the major regulatory role in the crosstalk between p38 MAPK and caspase-9 and that direct interaction between p38 MAPK and caspase-9 may regulate mitochondria-mediated apoptosis in the TαPcZn-PDT-treated LoVo cells.

Guanylate-binding protein 2 regulates Drp1-mediated mitochondrial fission to suppress breast cancer cell invasion

Guanylate-binding protein 2 (GBP2) is a member of the large GTPase superfamily that is strongly induced by interferon-γ (IFN-γ). Although the biochemical characteristics of GBP2 have been reported in detail, its biological function has not been thoroughly elucidated to date. To the best of our knowledge, this study presents the first demonstration that GBP2 inhibits mitochondrial fission and cell metastasis in breast cancer cells both in vitro and in vivo. Our previous work demonstrated that dynamin-related protein 1 (Drp1)-dependent mitochondrial fission has a key role in breast cancer cell invasion. In this study, we demonstrate that GBP2 binds directly to Drp1. Elimination of Drp1 by shRNA or Mdivi-1 (a Drp1-specific inhibitor) suppressed GBP2's regulatory function. Furthermore, GBP2 blocks Drp1 translocation from the cytosol to mitochondria, thereby attenuating Drp1-dependent mitochondrial fission and breast cancer cell invasion. In summary, our data provide new insights into the function and molecular mechanisms underlying GBP2's regulation of breast cancer cell invasion.

PP2A mediates apoptosis or autophagic cell death in multiple myeloma cell lines

The crosstalk between apoptosis and autophagy contributes to tumorigenesis and cancer therapy. The process by which BetA (betulinic acid), a naturally occurring triterpenoid, regulates apoptosis and autophagy as a cancer therapy is unclear. In this study, we show for the first time that protein phosphatase 2A (PP2A) acts as a switch to regulate apoptosis and autophagic cell death mediated by BetA. Under normal conditions, caspase-3 is activated by the mitochondrial pathway upon BetA treatment. Activated caspase-3 cleaves the A subunit of PP2A (PP2A/A), resulting in the association of PP2A and Akt. This association inactivates Akt to initiate apoptosis. Overexpression of Bcl-2 attenuates the mitochondrial apoptosis pathway, resulting in caspase-3 inactivation and the dissociation of PP2A and Akt. PP2A isolated from Akt binds with DAPK to induce autophagic cell death. Meanwhile, in vivo tumor experiments have demonstrated that BetA initiates different types of cell death in a myeloma xenograft model. Thus, PP2A can shift myeloma cells from apoptosis to autophagic cell death. These findings have important implications for the therapeutic application of BetA, particularly against apoptosis-resistant cancers.

Mcl-1 expression and JNK activation induces a threshold for apoptosis in Bcl-xL-overexpressing hematopoietic cells

The regulation of Mcl-1 expression is necessary for the induction of cancer cell apoptosis by ABTs such as ABT-737, ABT-263 and ABT-199. However, the reduction in Mcl-1 expression is not sufficient for initiating cell death in hematopoietic cancer cells with high Bcl-xL expression. Here, we demonstrate that 2-deoxyglucose (2-DG) enhanced the effect of ABT-199 to induce cell apoptosis in hematologic malignancies with up-regulated Bcl-xL expression. Our study revealed that 2-DG could decrease glucose-dependent and Akt-independent Mcl-1 expression, which is mediated by the mechanistic target of rapamycin complex 1 (mTORC1) pathway. Moreover, the combination of 2-DG and ABT-199 triggered c-Jun NH2-terminal kinase (JNK) phosphorylation and subsequent Bcl-xL degradation, whereas 2-DG and ABT-199 alone had little effect on JNK activation. Therefore, the combination of 2-DG and ABT-199 initiated cell death through the reduction of Mcl-1 expression and JNK activation. Our study could provide a clinical theoretical basis for the use of ABT-199 in hematologic malignancies with excessive Bcl-xL expression.

Drugs currently under investigation for the treatment of invasive candidiasis

INTRODUCTION

The widespread implementation of immunosuppressants, immunomodulators, hematopoietic stem cell transplantation and solid organ transplantation in clinical practice has led to an expanding population of patients who are at risk for invasive candidiasis, which is the most common form of fungal disease among hospitalized patients in the developed world. The emergence of drug-resistant Candida spp. has added to the morbidity associated with invasive candidiasis and novel therapeutic strategies are urgently needed. Areas covered: In this paper, we explore investigational agents for the treatment of invasive candidiasis, with particular attention paid to compounds that have recently entered phase I or phase II clinical trials. Expert opinion: The antifungal drug development pipeline has been severely limited due to regulatory hurdles and a systemic lack of investment in novel compounds. However, several promising drug development strategies have recently emerged, including chemical screens involving Pathogen Box compounds, combination antifungal therapy, and repurposing of existing agents that were initially developed to treat other conditions, all of which have the potential to redefine the treatment of invasive candidiasis.

Anticancer effects of β-elemene with hyperthermia in lung cancer cells

β-elemene is a novel, plant-derived anticancer drug, which has been used to target multiple solid tumor types. Hyperthermia is an adjuvant therapeutic modality to treat cancer. However, the underlying mechanisms associated with the efficacy of these two treatments are largely unknown. The aim of the present study was to evaluate the effects of β-elemene combined with hyperthermia in lung cancer cell lines. An MTT assay was used to determine cell viability. The cell cycle and apoptosis were analyzed using flow cytometry. The morphology of cells during apoptosis was determined using a transmission electron microscope. The expression levels of P21, survivin, caspase-9, B-cell lymphoma 2 (Bcl-2) and Bcl-2-like protein 4 (Bax) mRNA were detected using quantitative polymerase chain reaction. β-elemene with hyperthermia treatment significantly inhibited the viability and increased the apoptosis rate of A549 cells compared with β-elemene treatment alone (P<0.01), and significantly decreased the proportion of cells in S phase compared with the control (P<0.01). Morphological observation using transmission electron microscopy indicated cross-sectional features of apoptosis: Chromatin condensation, reduced integrity of the plasma membrane, increased cellular granularity, nuclear collapse and the formation of apoptotic bodies. β-elemene with hyperthermia treatment significantly promoted P21 and Bax mRNA expression (P<0.01) and significantly decreased caspase-9, Bcl-2 and survivin mRNA expression (P<0.01) in A549 cells. In conclusion, β-elemene with hyperthermia has a significant inhibitory effect on A549 cells. This occurs through reducing S phase and inducing apoptosis, via an increase in P21 and Bax expression and a decrease in caspase-9, Bcl-2 and survivin expression.

Mitochondrial p53 phosphorylation induces Bak-mediated and caspase-independent cell death

Chemoresistance in cancer has previously been attributed to gene mutations or deficiency. Caspase mutations or Bax deficiency can lead to resistance to cancer drugs. We recently demonstrated that Bak initiates a caspase/Bax-independent cell death pathway. We show that Plumbagin (PL) (5-hydroxy-2-methyl-1,4-napthoquinone), a medicinal plant-derived naphthoquinone that is known to have anti-tumor activity in a variety of models, induces caspase-independent cell death in HCT116 Bax knockout (KO) or MCF-7 Bax knockdown (KD) cells that express wild-type (WT) Bak. The re-expression of Bax in HCT116 Bax KO cells fails to enhance the PL-induced cell death. Additionally, Bak knockdown by shRNA efficiently attenuates PL-induced cell death. These results suggest that PL-induced cell death depends primarily on Bak, not Bax, in these cells. Further experimentation demonstrated that p53 Ser15 phosphorylation and mitochondrial translocation mediated Bak activation and subsequent cell death. Knockdown of p53 or a p53 Ser15 mutant significantly inhibited p53 mitochondrial translocation and cell death. Furthermore, we found that Akt mediated p53 phosphorylation and the subsequent mitochondrial accumulation. Taken together, our data elaborate the role of Bak in caspase/Bax-independent cell death and suggest that PL may be an effective agent for overcoming chemoresistance in cancer cells with dysfunctional caspases.

Caspase-3 feedback loop enhances Bid-induced AIF/endoG and Bak activation in Bax and p53-independent manner

Chemoresistance in cancer has previously been attributed to gene mutations or deficiencies. Bax or p53 deficiency can lead to resistance to cancer drugs. We aimed to find an agent to overcome chemoresistance induced by Bax or p53 deficiency. Here, we used immunoblot, flow-cytometry analysis, gene interference, etc. to show that genistein, a major component of isoflavone that is known to have anti-tumor activities in a variety of models, induces Bax/p53-independent cell death in HCT116 Bax knockout (KO), HCT116 p53 KO, DU145 Bax KO, or DU145 p53 KO cells that express wild-type (WT) Bak. Bak knockdown (KD) only partially attenuated genistein-induced apoptosis. Further results indicated that the release of AIF and endoG also contributes to genistein-induced cell death, which is independent of Bak activation. Conversely, AIF and endoG knockdown had little effect on Bak activation. Knockdown of either AIF or endoG alone could not efficiently inhibit apoptosis in cells treated with genistein, whereas an AIF, endoG, and Bak triple knockdown almost completely attenuated apoptosis. Next, we found that the Akt-Bid pathway mediates Bak-induced caspase-dependent and AIF- and endoG-induced caspase-independent cell death. Moreover, downstream caspase-3 could enhance the release of AIF and endoG as well as Bak activation via a positive feedback loop. Taken together, our data elaborate the detailed mechanisms of genistein in Bax/p53-independent apoptosis and indicate that caspase-3-enhanced Bid activation initiates the cell death pathway. Our results also suggest that genistein may be an effective agent for overcoming chemoresistance in cancers with dysfunctional Bax and p53.

The Tomato Glycoalkaloid α-Tomatine Induces Caspase-Independent Cell Death in Mouse Colon Cancer CT-26 Cells and Transplanted Tumors in Mice

Tomatoes (Solanum lycopersicum) produce the bioactive glycoalkaloid α-tomatine. This study determined the effect of commercial α-tomatine on CT-26 colon cancer cells in vitro and in vivo in an intracutaneously transplanted mouse tumor. Cytotoxicity experiments showed that α-tomatine induces about 50% lysis of the colon cancer cells at 3.5 μM after 24 h of treatment. Large proportions of cells were found to be in the annexin V (+)/propidium iodide (+) phase of cell death, implying late phase apoptotic/necrotic status. However, α-tomatine induced cell death in CT-26 cancer cells through caspase-independent signaling pathways. This conclusion was supported by Western blot analysis showing a localization of apoptosis-inducing mitochondrial protein (AIF) to the nucleus and down-regulation of survivin (an inhibitor of apoptosis) expression as well as failure to detect the active form of caspase-3, -8, and -9 produced by proteolytic cleavage in CT-26 cancer cells. Intraperitoneally administered α-tomatine (5 mg/kg body weight) also markedly inhibited growth of the tumor using CT-26 cancer cells without causing body and organ weight changes. The reduced tumor growth in the mice by 38% after 2 weeks was the result of increased caspase-independent apoptosis associated with increased nuclear translocation of AIF and decreased survivin expression in tumor tissues. α-Tomatine in pure form and in tomatine-rich green tomatoes might prevent colon cancer.