Camalexin induces apoptosis in T-leukemia Jurkat cells by increased concentration of reactive oxygen species and activation of caspase-8 and caspase-9

Anticancer Potential of Indole Phytoalexins and Their Analogues

Indole phytoalexins, found in economically significant Cruciferae family plants, are synthesized in response to pathogen attacks or stress, serving as crucial components of plant defense mechanisms against bacterial and fungal infections. Furthermore, recent research indicates that these compounds hold promise for improving human health, particularly in terms of potential anticancer effects that have been observed in various studies. Since our last comprehensive overview in 2016 focusing on the antiproliferative effects of these substances, brassinin and camalexin have been the most extensively studied. This review analyses the multifaceted pharmacological effects of brassinin and camalexin, highlighting their anticancer potential. In this article, we also provide an overview of the antiproliferative activity of new synthetic analogs of indole phytoalexins, which were synthesized and tested at our university with the aim of enhancing efficacy compared to the parent compound.

Exploring the Antiproliferative and Modulatory Effects of 1-Methoxyisobrassinin on Ovarian Cancer Cells: Insights into Cell Cycle Regulation, Apoptosis, Autophagy, and Its Interactions with NAC

Ovarian cancer, a highly lethal malignancy among reproductive organ cancers, poses a significant challenge with its high mortality rate, particularly in advanced-stage cases resistant to platinum-based chemotherapy. This study explores the potential therapeutic efficacy of 1-methoxyisobrassinin (MB-591), a derivative of indole phytoalexins found in Cruciferae family plants, on both cisplatin-sensitive (A2780) and cisplatin-resistant ovarian cancer cells (A2780 cis). The findings reveal that MB-591 exhibits an antiproliferative effect on both cell lines, with significantly increased potency against cisplatin-sensitive cells. The substance induces alterations in the distribution of the cell cycle, particularly in the S and G2/M phases, accompanied by changes in key regulatory proteins. Moreover, MB-591 triggers apoptosis in both cell lines, involving caspase-9 cleavage, PARP cleavage induction, and DNA damage, accompanied by the generation of reactive oxygen species (ROS) and mitochondrial dysfunction. Notably, the substance selectively induces autophagy in cisplatin-resistant cells, suggesting potential targeted therapeutic applications. The study further explores the interplay between MB-591 and antioxidant N-acetylcysteine (NAC), in modulating cellular processes. NAC demonstrates a protective effect against MB-591-induced cytotoxicity, affecting cell cycle distribution and apoptosis-related proteins. Additionally, NAC exhibits inhibitory effects on autophagy initiation in cisplatin-resistant cells, suggesting its potential role in overcoming resistance mechanisms.

Combined effects of two phytoalexins, brassinin and camalexin, on the cells of colorectal origin

Brassinin and camalexin belong to phytoalexins, plant compounds generated in the response to stress. Both compounds are known to be cytotoxic to several cancer cell lines, mainly by inducing oxidative stress and subsequent apoptosis. In the presented study, cytotoxic effects of brassinin and camalexin, individually and, for the first time, after combined exposure, on the cells of normal (CCD-Co18) and cancer (Caco-2) lines originated from colorectal tissues and their proapoptotic impact on Caco-2 cells were studied. The determined IC50 values indicate a clearly higher sensitivity of cancer cells to the tested substances, as well as a stronger cytotoxic effect of camalexin than brassinin. The synergistic effect of both phytoalexins was also demonstrated. Caspase-dependent and independent mechanisms were involved in the final effects. Both tested phytoalexins caused evident, concentration-dependent symptoms of oxidative stress in cancer cells, leading to apoptosis, but in the highest concentrations, also to necrosis. In case of camalexin, signs of pyroptosis were additionally detected.

Brassinin Enhances Apoptosis in Hepatic Carcinoma by Inducing Reactive Oxygen Species Production and Suppressing the JAK2/STAT3 Pathway

Plants from the family Brassicaceae produce brassinin (BSN), which is an essential indole phytoalexin. BSN can kill certain types of cancer cells. Using hepatocarcinoma (HCC) cells, we examined the molecular mechanisms of BSN. We found that HCC cell growth was suppressed and apoptosis was induced by BSN via the downregulation of the JAK/STAT3 pathway. The cytoplasmic latent transcription factor STAT3, belonging to the STAT family, acted as both a signal transducer and an activator and was linked to tumor progression and decreased survival. BSN incubation caused HCC cells to produce reactive oxygen species (ROS). By activating caspase-9/-3 and PARP cleavage, Bcl-2 was reduced, and apoptosis was increased. BSN inhibited constitutive STAT3, JAK2, and Src phosphorylation. The JAK/STAT signaling cascade was confirmed by siRNA silencing STAT3 in HCC cells. BSN also suppressed apoptosis by Z-Val-Ala-Asp-Fluoromethylketone (Z-VAD-FMK), an apoptotic inhibitor. N-acetylcysteine (NAC) inhibited the production of ROS and diminished BSN-induced apoptosis. Our findings suggested that BSN has potential as a treatment for cancer.

Discovery of Phytoalexin Camalexin and Its Derivatives as Novel Antiviral and Antiphytopathogenic-Fungus Agents

In response to the invasion of plant viruses and pathogenic fungi, higher plants produce defensive allelochemicals. Finding candidate varieties of botanical pesticides based on allelochemicals is one of the important ways to create efficient and green pesticides. Here, a series of camalexin derivatives based on a phytoalexin camalexin scaffold were designed, synthesized, and assessed for their antiviral and fungicidal activities systematically. Most of these camalexin derivatives exhibited better antiviral activities against tobacco mosaic virus (TMV) than the control antiviral agent ribavirin. Under the same test conditions, the anti-TMV activities of compounds 3d, 5a, 5d, and 10f-10h were found to be equivalent to or better than that of ningnanmycin, an agricultural cytosine nucleoside antibiotic with excellent protective effect. The antiviral mechanism research showed that compound 5a could cause 20S CP disk fusion and disintegration, thus affecting the assembly of virus particles. The results of molecular docking indicate that there were obvious hydrogen bonds between compounds 3d, 5a, and 10f and TMV CP. The binding constants of compounds 5a and 10f to TMV CP were also calculated using fluorescence titration. These camalexin derivatives also presented broad spectrum fungicidal activities, especially for Rhizoctonia solani and Physalospora piricola. In this work, the design, synthesis, structure optimization, and mode of action of camalexin derivatives were carried out progressively. This work provides a reference for using defensive chemical compounds as novel pesticide lead compounds.

Inhibition of the JAZ1 gene causes activation of camalexin biosynthesis in Arabidopsis callus cultures

Indole alkaloid camalexin has potential medicinal properties such as suppressing the viability of leukemic but not normal cells. Camalexin is not produced in plants and an external factor is required to activate its biosynthesis. In this work, we stimulated camalexin biosynthesis in Arabidopsis calli by blocking one of repressors of the jasmonate pathway, the jasmonate ZIM-domain protein 1 (JAZ1) by using amiRNA targeting JAZ1 gene transcripts. Inhibition of the JAZ1 gene led to an increase in camalexin content from trace amounts in control culture to 9 µg/g DW in the jaz1 line without affecting growth. In addition, JAZ1 silencing enhanced tolerance to cold stress with simultaneous increasing camalexin content up to 30 µg/g DW. Real-time quantitative PCR determination of marker gene expression showed that effects caused by the JAZ1 silencing might be realized through crosslinking JA, ROS, and abscisic acid signaling pathways. Thus, targeting the distal components of signaling pathways can be suggested as a tool for bioengineering of secondary metabolism, along with standard techniques for targeting biosynthetic genes or genes encoding transcription factors.

Naturally occurring heterocyclic anticancer compounds

Naturally occurring heterocyclic scaffolds are key ingredients for the development of various therapeutics employed for biomedical applications. Heterocyclic pharmacophores are widely disseminated and have been befallen in almost all categories of drugs for the alleviation of myriad ailments including diabetes, neurodegenerative, psychiatric, microbial infections, disastrous cancers etc. Countless fused heterocyclic anticancerous templates are reported to display antimetabolite, antioxidant, antiproliferative, cytostatic etc. pharmacological actions via targeting different signaling pathways (cell cycle, PI-3kinase/Akt, p53, caspase extrinsic pathway etc.), overexpressive receptors (EGRF, HER2, EGF, VEGF etc.) and physiological enzymes (topoisomerase I and II, cyclin dependent kinase etc.). A compiled description on various natural sources (plants, microbes, marine) containing anticancer agents comprising heterocyclic ring specified with presence of nitrogen (vincristine, vinblastine, indole-3-carbinol, meridianins, piperine, lamellarins etc.), oxygen (paclitaxel, halichondrin B, quercetin, myricetin, kaempferol etc.) and sulphur atoms (brugine, fucoidan, carrageenan etc.) are displayed here along with their molecular level cytotoxic action and therapeutic applications.

Camalexin, an indole phytoalexin, inhibits cell proliferation, migration, and mammosphere formation in breast cancer cells via the aryl hydrocarbon receptor

Breast cancer is the most commonly diagnosed cancer among women worldwide. Despite a variety of drugs available for the treatment of patients with breast cancer, drug resistance remains a significant clinical problem. Therefore, there is an urgent need to develop drugs with new mechanisms of action. Camalexin is the main indole phytoalexin in Arabidopsis thaliana and other crucifers. Camalexin inhibits the proliferation of various cancer cells. However, the mechanism by which camalexin inhibits cell proliferation remains unclear. In this study, we found that camalexin inhibited cell proliferation and migration of breast cancer cell lines. Furthermore, camalexin also suppressed breast cancer stem cell-derived mammosphere formation. We previously reported that the ligand-activated transcription factor aryl hydrocarbon receptor (AhR) agonist suppresses mammosphere formation. Several compounds with indole structures are known to act as AhR agonists. Therefore, we hypothesized that the inhibition of mammosphere formation by camalexin may involve AhR activation. We found that camalexin increased the nuclear translocation of AhR, AhR-mediated transcriptional activation, and expression of AhR target genes. In addition, camalexin suppressed mammosphere formation in AhR-expressing breast cancer cells more than in the breast cancer cells that lacked AhR expression. Taken together, the data demonstrate that camalexin is a novel AhR agonist and that the inhibition of cell proliferation, migration, and mammosphere formation by camalexin involves the activation of AhR. Our findings suggest that camalexin, an AhR agonist, may be a novel therapeutic agent for breast cancer.

Redox Control in Acute Lymphoblastic Leukemia: From Physiology to Pathology and Therapeutic Opportunities

Acute lymphoblastic leukemia (ALL) is a hematological malignancy originating from B- or T-lymphoid progenitor cells. Recent studies have shown that redox dysregulation caused by overproduction of reactive oxygen species (ROS) has an important role in the development and progression of leukemia. The application of pro-oxidant therapy, which targets redox dysregulation, has achieved satisfactory results in alleviating the conditions of and improving the survival rate for patients with ALL. However, drug resistance and side effects are two major challenges that must be addressed in pro-oxidant therapy. Oxidative stress can activate a variety of antioxidant mechanisms to help leukemia cells escape the damage caused by pro-oxidant drugs and develop drug resistance. Hematopoietic stem cells (HSCs) are extremely sensitive to oxidative stress due to their low levels of differentiation, and the use of pro-oxidant drugs inevitably causes damage to HSCs and may even cause severe bone marrow suppression. In this article, we reviewed research progress regarding the generation and regulation of ROS in normal HSCs and ALL cells as well as the impact of ROS on the biological behavior and fate of cells. An in-depth understanding of the regulatory mechanisms of redox homeostasis in normal and malignant HSCs is conducive to the formulation of rational targeted treatment plans to effectively reduce oxidative damage to normal HSCs while eradicating ALL cells.

MEDICASCY: A Machine Learning Approach for Predicting Small-Molecule Drug Side Effects, Indications, Efficacy, and Modes of Action

To improve the drug discovery yield, a method which is implemented at the beginning of drug discovery that accurately predicts drug side effects, indications, efficacy, and mode of action based solely on the input of the drug's chemical structure is needed. In contrast, extant predictive methods do not comprehensively address these aspects of drug discovery and rely on features derived from extensive, often unavailable experimental information for novel molecules. To address these issues, we developed MEDICASCY, a multilabel-based boosted random forest machine learning method that only requires the small molecule's chemical structure for the drug side effect, indication, efficacy, and probable mode of action target predictions; however, it has comparable or even significantly better performance than existing approaches requiring far more information. In retrospective benchmarking on high confidence predictions, MEDICASCY shows about 78% precision and recall for predicting at least one severe side effect and 72% precision drug efficacy. Experimental validation of MEDICASCY's efficacy predictions on novel molecules shows close to 80% precision for the inhibition of growth in ovarian, breast, and prostate cancer cell lines. Thus, MEDICASCY should improve the success rate for new drug approval. A web service for academic users is available at http://pwp.gatech.edu/cssb/MEDICASCY.

Camalexin Induces Apoptosis via the ROS-ER Stress-Mitochondrial Apoptosis Pathway in AML Cells

Camalexin is a phytoalexin that accumulates in various cruciferous plants upon exposure to environmental stress and plant pathogens. It was shown that camalexin has potent antitumor properties, but its underlying mechanisms are still elusive. In the present study, we evaluated the effects of camalexin on human leukemic cells and normal polymorph nuclear cells. CCK-8 assay was used to determine cell viability after camalexin treatment. Apoptosis, intracellular reactive oxygen species (ROS) levels, and loss of mitochondrial membrane potential (MMP) were measured by flow cytometry. The activity of SOD, catalase, and ratio of GSH/GSSG were assayed. ER stress and apoptotic signaling pathway was examined by Western blot. Xenograft mice were used to verify the effect of camalexin in vivo. Our results indicated that camalexin inhibited viability of leukemic but not normal polymorph nuclear cells. Furthermore, camalexin induces apoptosis via the mitochondrial pathway in a caspase-dependent manner. We also observed ER stress is located upstream of apoptosis induced by camalexin. Besides, ROS levels, SOD activity, CAT activity, and GSSG levels were significantly enhanced while the GSH level was decreased after treatment of camalexin. In addition, the generation of ROS is critical for the ER stress and apoptosis induced by camalexin. Finally, administration of camalexin suppresses xenograft tumor graft growth without obvious toxicity. Taken together, this study indicates that camalexin exerts antitumor effects against leukemia cells via the ROS-ER stress-mitochondrial apoptosis pathway.

Viscum articulatum Burm. f. aqueous extract exerts antiproliferative effect and induces cell cycle arrest and apoptosis in leukemia cells

ETHNOPHARMACOLOGICAL RELEVANCE

Viscum articulatum Burm. f. (leafless mistletoe) has been used in traditional system of medicines in India, China, Taiwan, Cambodia, Laos, and Vietnam, to treat blood-related diseases and various inflammatory and degenerative diseases including cancer. Anticancer activities of some phytomolecules purified from Viscum articulatum Burm. f. have been tested. However scientific evidence for the anticancerous potential of aqueous extract of V. articularum (VAQE) used in traditional medicine is lacking.

AIM OF THE STUDY

To study the antiproliferative and apoptotic effect of VAQE on Jurkat E6.1 and THP1 leukemia cells.

MATERIALS AND METHODS

The aqueous extract of the whole plant of Viscum articulatum Burm. f. was prepared in phosphate buffer saline. In VAQE, total soluble protein was estimated using Bradford's dye-binding assay; flavonoid content was determined using aluminum chloride colorimetric assay; and phenolic content was estimated following Folin-Ciocalteu colorimetric assay. XTT cell viability assay was used to test VAQE induced cytotoxicity in Jurkat E6.1 and THP1 leukemia cells and peripheral blood mononuclear cells (PBMC). The effect of VAQE on cell cycle progression was analyzed by PI staining using flow cytometry. Annexin-V-FITC/PI differential staining method was used for detecting the onset of apoptosis in leukemia cells. Rhodamine 123 dye was used to detect the change in mitochondrial membrane potential (MMP) using flow cytometry. DCF-DA fluorescence dye was used to estimate the level of reactive oxygen species (ROS). The ROS inhibitors were used to evaluate the role of ROS in mediating DNA degradation in VAQE-treated leukemia cells. The molecular mechanisms underlying VAQE induced apoptosis induction was studied by analyzing the expression of anti-apoptotic (Bcl-2) and pro-apoptotic (Bax) proteins, caspase-8 and caspase-3 enzymes using western blot. Diphenylamine (DPA) assay was used to determine the DNA fragmentation and conclusion of apoptosis.

RESULTS

VAQE triggered cytotoxic effect on Jurkat E6.1 (IC₅₀-2.4 µg/ml; 24 h) and THP1 (IC₅₀-1.0 µg/ml; 24 h) cells in a dose- and time-dependent manner. The apoptosis induction and G2/M arrest of the cell cycle are the cause of VAQE-induced cytotoxicity in leukemia cells. The apoptosis in VAQE-treated Jurkat E6.1 and THP1 cells was mediated via a reduction in MMP, elevation of intracellular ROS, decreased expression of the anti-apoptotic (Bcl-2) and increased expression of the pro-apoptotic (Bax) protein, activation of caspase-8 and caspase-3 and DNA fragmentation.

CONCLUSION

VAQE has a high efficacy to exert a cytotoxic effect in Jurkat E6.1 and THP1 cells and to induce apoptosis and G2/M cell cycle arrest. VAQE induces extrinsic pathway of apoptosis in both the leukemia cell lines via disruption of MMP, intracellular ROS imbalance, increased ratio of Bax/Bcl-2, activation of caspase-8, caspase-3 and ROS-mediated DNA fragmentation. The knowledge gained from the outcomes of the study may encourage the identification of novel chemotherapeutic agent from Viscum articulatum Burm. f. to treat leukemia.

Indole phytoalexin derivatives induce mitochondrial-mediated apoptosis in human colorectal carcinoma cells

AIM

To investigate the mechanism of the antiproliferative effect of synthetic indole phytoalexin derivatives on human colorectal cancer cell lines.

METHODS

Changes in cell proliferation and the cytotoxic effect of the tested compounds on human colorectal cancer cell lines and human fibroblasts were evaluated using MTS and BrdU assay, allowing us to choose the most potent substance. Cell cycle alterations were analyzed using flow cytometric analysis. The apoptosis-inducing effect of compound K-453 on the HCT116 cell line was examined with annexin V/PI double staining using flow cytometry, as well as acridine orange/propidium iodide (AO/PI) staining. The flow cytometry method also allowed us to measure changes in levels or activation states of other factors associated with apoptosis, such as poly (ADP-ribose) polymerase (PARP), caspase-3 and -9, cytochrome c, Bcl-2 family proteins, and also the integrity of the mitochondrial membrane. To evaluate activity of the transcription factors and proteins involved in signaling pathways we used Western blot analysis together with flow cytometry.

RESULTS

Among the ten tested compounds, compound K-453 {(±)-trans-1,2-dimethoxy-2’-(3,5-bis-trifluoromethylphenylamino)spiro{indoline-3,5’[4’,5’]dihydrothiazol} exhibited the most potent activity with IC₅₀ = 32.22 ± 1.14 μmol/L in human colorectal HCT116 cells and was thus selected for further studies. Flow cytometric analysis revealed a K-453-induced increase in the population of cells with sub-G₁ DNA content, which is considered as a marker of apoptotic cell death. The apoptosis-inducing effect of compound K453 was also confirmed by annexin V/PI double staining and AO/PI staining. The apoptosis was associated with the loss of mitochondrial membrane potential, PARP cleavage, caspase-3 and caspase-9 activation, release of cytochrome c, as well as changes in the levels of Bcl-2 family members. Moreover, flow cytometry showed that compound K-453 stimulates phosphorylation of p38 MAPK but decreases phosphorylation of Akt and Erk 1/2. Activation of p38 MAPK was also confirmed using Western blot analysis. This analysis also revealed down-regulation of NF-κB1 (p50) and RelA (p65) proteins and the loss of their anti-apoptotic activity.

CONCLUSION

In our study compound K-453 exhibited an antiproliferative effect by induction of intrinsic apoptosis as well as modulation of several signaling pathways.

Camalexin-Induced Cell Membrane Scrambling and Cell Shrinkage in Human Erythrocytes

Background/Aims: The thaliana phytoalexin Camalexin has been proposed for the treatment of malignancy. Camalexin counteracts tumor growth in part by stimulation of suicidal death or apoptosis of tumor cells. Similar to apoptosis of nucleated cells, erythrocytes may enter suicidal death or eryptosis, which is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Cellular mechanisms contributing to the complex machinery executing eryptosis include increase of cytosolic Ca2+ activity ([Ca2+]i), oxidative stress, ceramide, protein kinase C and caspases. The present study explored, whether Camalexin induces eryptosis and, if so, to shed light on mechanisms involved. Methods: Phosphatidylserine exposure at the cell surface was estimated from annexin-V-binding, cell volume from forward scatter, [Ca2+]i from Fluo-3 fluorescence, ROS formation from DCFDA dependent fluorescence, and ceramide abundance utilizing specific antibodies. Results: A 48 hours exposure of human erythrocytes to Camalexin significantly increased the percentage of annexin-V-binding cells (≥ 10 µg/ml), significantly decreased forward scatter (≥ 5 µg/ml) and significantly increased Fluo-3-fluorescence (≥ 10 µg/ml), but did not significantly modify DCFDA fluorescence or ceramide abundance. The effect of Camalexin on annexin-V-binding was significantly blunted by removal of extracellular Ca2+, by kinase inhibitors staurosporine (1 µM) and chelerythrine (10 µM), as well as by caspase inhibitors zVAD (10 µM) and zIETD-fmk (50 µM). Conclusions: Camalexin triggers cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane, an effect at least in part depending on Ca2+ entry, as well as staurosporine and chelerythrine sensitive kinase(s) as well as zVAD and zIETD-fmk sensitive caspase(s).

Acquired resistance of pancreatic cancer cells to cisplatin is multifactorial with cell context-dependent involvement of resistance genes

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal of malignancies, in large measure, due to the propensity of PDAC cells to acquire resistance to chemotherapeutic agents. A better understanding of the molecular basis of acquired resistance is a major focus of contemporary PDAC research. We report here the results of a study to independently develop cisplatin resistance in two distinct parental PDAC cell lines, AsPC1 and BxPC3, and to subsequently examine the molecular mechanisms associated with the acquired resistance. Cisplatin resistance in both resistant cell lines was found to be multifactorial and to be associated with mechanisms related to drug transport, drug inactivation, DNA damage response, DNA repair and the modulation of apoptosis. Our results demonstrate that the two resistant cell lines employed alternative molecular strategies in acquiring resistance dictated, in part, by pre-existing molecular differences between the parental cell lines. Collectively, our findings indicate that strategies to inhibit or reverse acquired resistance of PDAC cells to cisplatin, and perhaps other chemotherapeutic agents, may not be generalized but will require individual molecular profiling and analysis to be effective.

Antiproliferative Effect of Indole Phytoalexins

Indole phytoalexins from crucifers have been shown to exhibit significant anti-cancer, chemopreventive, and antiproliferative activity. Phytoalexins are natural low molecular antimicrobial compounds that are synthesized and accumulated in plants after their exposure to pathogenic microorganisms. Most interestingly, crucifers appear to be the only plant family producing sulfur-containing indole phytoalexins. The mechanisms underlying its anti-cancer properties are unknown. Isolation from cruciferous plants does not provide sufficient quantities of indole phytoalexins and, for biological screening, they are usually obtainable through synthesis. Understanding the molecular mechanism of the action of these substances and their structure-activity relationships is quite important in the development of new analogs with a more favorable profile of biological activities. In this review, we present the key features of indole phytoalexins, mainly their antiproliferative ativities.

Reactive Oxygen Species Regulate T Cell Immune Response in the Tumor Microenvironment

Reactive oxygen species (ROS) produced by cellular metabolism play an important role as signaling messengers in immune system. ROS elevated in the tumor microenvironment are associated with tumor-induced immunosuppression. T cell-based therapy has been recently approved to be effective for cancer treatment. However, T cells often become dysfunctional after reaching the tumor site. It has been reported that ROS participate extensively in T cells activation, apoptosis, and hyporesponsiveness. The sensitivity of T cells to ROS varies among different subsets. ROS can be regulated by cytokines, amino acid metabolism, and enzymatic activity. Immunosuppressive cells accumulate in the tumor microenvironment and induce apoptosis and functional suppression of T cells by producing ROS. Thus, modulating the level of ROS may be important to prolong survival of T cells and enhance their antitumor function. Combining T cell-based therapy with antioxidant treatment such as administration of ROS scavenger should be considered as a promising strategy in cancer treatment, aiming to improve antitumor T cells immunity.

Snail-induced epithelial-to-mesenchymal transition of MCF-7 breast cancer cells: systems analysis of molecular changes and their effect on radiation and drug sensitivity

Background

Epithelial-to-mesenchymal transition (EMT) has been associated with the acquisition of metastatic potential and the resistance of cancer cells to therapeutic treatments. MCF-7 breast cancer cells engineered to constitutively express the zinc-finger transcriptional repressor gene Snail (MCF-7-Snail cells) have been previously shown to display morphological and molecular changes characteristic of EMT. We report here the results of a comprehensive systems level molecular analysis of changes in global patterns of gene expression and levels of glutathione and reactive oxygen species (ROS) in MCF-7-Snail cells and the consequence of these changes on the sensitivity of cells to radiation treatment and therapeutic drugs.

Methods

Snail-induced changes in global patterns of gene expression were identified by microarray profiling using the Affymetrix platform (U133 Plus 2.0). The resulting data were processed and analyzed by a variety of system level analytical methods. Levels of ROS and glutathione (GSH) were determined by fluorescent and luminescence assays, and nuclear levels of NF-κB protein were determined by an ELISA based method. The sensitivity of cells to ionizing radiation and anticancer drugs was determined using a resazurin-based cell cytotoxicity assay.

Results

Constitutive ectopic expression of Snail in epithelial-like, luminal A-type MCF-7 cells induced significant changes in the expression of >7600 genes including gene and miRNA regulators of EMT. Mesenchymal-like MCF-7-Snail cells acquired molecular profiles characteristic of triple-negative, claudin-low breast cancer cells, and displayed increased sensitivity to radiation treatment, and increased, decreased or no change in sensitivity to a variety of anticancer drugs. Elevated ROS levels in MCF-7-Snail cells were unexpectedly not positively correlated with NF-κB activity.

Conclusions

Ectopic expression of Snail in MCF-7 cells resulted in morphological and molecular changes previously associated with EMT. The results underscore the complexity and cell-type dependent nature of the EMT process and indicate that EMT is not necessarily predictive of decreased resistance to radiation and drug-based therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2274-5) contains supplementary material, which is available to authorized users.

ROS-dependent antiproliferative effect of brassinin derivative homobrassinin in human colorectal cancer Caco2 cells

This study was designed to examine the in vitro antiproliferative effect of brassinin and its derivatives on human cancer cell lines. Among seven tested compounds, homobrassinin (K1; N-[2-(indol-3-yl)ethyl]-S-methyldithiocarbamate) exhibited the most potent activity with IC₅₀ = 8.0 μM in human colorectal Caco2 cells and was selected for further studies. The flow cytometric analysis revealed a K1-induced increase in the G₂/M phase associated with dysregulation of α-tubulin, α₁-tubulin and β₅-tubulin expression. These findings suggest that the inhibitory effect of K1 can be mediated via inhibition of microtubule formation. Furthermore, simultaneously with G₂/M arrest, K1 also increased population of cells with sub-G₁ DNA content which is considered to be a marker of apoptotic cell death. Apoptosis was also confirmed by annexin V/PI double staining, DNA fragmentation assay and chromatin condensation assay. The apoptosis was associated with the loss of mitochondrial membrane potential (MMP), caspase-3 activation as well as intracellular reactive oxygen species (ROS) production. Moreover, the antioxidant Trolox blocked ROS production, changes in MMP and decreased K1 cytotoxicity, which confirmed the important role of ROS in cell apoptosis. Taken together, our data demonstrate that K1 induces ROS-dependent apoptosis in Caco2 cells and provide the rationale for further in vivo anticancer investigation.

Brassinin and its derivatives as potential anticancer agents

The aim of the study was to investigate the anti-proliferative activity of brassinin and its derivatives on human cancer cell lines. We found that among twenty-one tested compounds, 1- methoxybrassinin exerted the most potent anti-proliferative activity in Caco-2 cells with IC₅₀ 8.2 (±1.2)μmoll(-1). The flow cytometric analysis revealed a 1-methoxybrassinin-induced increase in the sub-G1 DNA content fraction which is considered to be a marker of apoptotic cell death. Apoptosis was also confirmed by DNA fragmentation assay. Moreover, quantitative real-time PCR showed that 1-methoxybrassinin upregulated the expression of pro-apoptotic Bax and downregulated the expression of anti-apoptotic genes Bcl-2 and Bcl-xL. The compound also increased activity of caspase-3, -7, cleaved PARP and decreased intracellular GSH content. The present study has assessed the in vitro anti-proliferative potential of 1-methoxybrassinin. The results generate a rationale for in vivo efficacy studies with this compound in preclinical cancer models.

Camalexin-induced apoptosis in prostate cancer cells involves alterations of expression and activity of lysosomal protease cathepsin D

Camalexin, the phytoalexin produced in the model plant Arabidopsis thaliana, possesses antiproliferative and cancer chemopreventive effects. We have demonstrated that the cytostatic/cytotoxic effects of camalexin on several prostate cancer (PCa) cells are due to oxidative stress. Lysosomes are vulnerable organelles to Reactive Oxygen Species (ROS)-induced injuries, with the potential to initiate and or facilitate apoptosis subsequent to release of proteases such as cathepsin D (CD) into the cytosol. We therefore hypothesized that camalexin reduces cell viability in PCa cells via alterations in expression and activity of CD. Cell viability was evaluated by MTS cell proliferation assay in LNCaP and ARCaP Epithelial (E) cells, and their respective aggressive sublines C4-2 and ARCaP Mesenchymal (M) cells, whereby the more aggressive PCa cells (C4-2 and ARCaPM) displayed greater sensitivity to camalexin treatments than the lesser aggressive cells (LNCaP and ARCaPE). Immunocytochemical analysis revealed CD relocalization from the lysosome to the cytosol subsequent to camalexin treatments, which was associated with increased protein expression of mature CD; p53, a transcriptional activator of CD; BAX, a downstream effector of CD, and cleaved PARP, a hallmark for apoptosis. Therefore, camalexin reduces cell viability via CD and may present as a novel therapeutic agent for treatment of metastatic prostate cancer cells.

Molecular analysis of the inhibitory effect of N-acetyl-L-cysteine on the proliferation and invasiveness of pancreatic cancer cells

Preliminary studies have suggested that the reactive oxygen species (ROS) scavenger N-acetyl-L-cysteine (NAC) may be effective in inhibiting the growth of pancreatic cancer cells. In-depth cellular and molecular analyses were carried out to determine NAC's mode of action in inhibiting the growth of a well-characterized pancreatic cancer cell line (AsPC-1). Standardized assays were used to monitor cellular growth, apoptosis, levels of ROS, cellular senescence, migration, and invasiveness. Cell stiffness was measured using atomic force microscopy. Gene expression was monitored by quantitative PCR. NAC significantly inhibits the growth and metastatic potential of AsPC-1 cells by inducing cell-cycle arrest in G1 and subsequent cellular senescence and decreased invasiveness. These anticancer properties are associated with an unexpected increase in the intracellular concentrations of ROS. NAC does not decrease the susceptibility of AsPC-1 cells to the anticancer drugs gemcitabine, mitomycin C, and doxorubicin. NAC-induced changes in gene expression are consistent with the onset of mesenchymal-to-epithelial transition. In conclusion, our findings indicate that NAC induces an integrated series of responses in AsPC-1 cells that make it a highly promising candidate for development as a pancreatic cancer therapeutic.

De novo genetic engineering of the camalexin biosynthetic pathway

Camalexin is a tryptophan-derived phytoalexin that is induced in the model plant Arabidopsis thaliana upon pathogen attack. Only few genes in the biosynthetic pathway of camalexin remain unidentified, however, investigation of candidate genes for these steps has proven particularly difficult partly because of redundancy in the genome of Arabidopsis. Here we describe metabolic engineering of the camalexin biosynthetic pathway in the transient Nicotiana benthamiana expression system. Camalexin accumulated in levels corresponding to what is seen in induced Arabidopsis thaliana. We have used this system to evaluate candidate genes suggested to be involved in the camalexin pathway. This has provided biochemical evidence for CYP71A12 conducting same reaction as CYP71A13 in the pathway. We discuss the prospects of using metabolic engineering of camalexin, both with respect to engineering plant defense and as a tool for screening yet unidentified candidate genes in the camalexin pathway.

In vitro toxicity of camalexin derivatives in human cancer and non-cancer cells

The aim of the study was to investigate the cytotoxic activity of camalexin and its five synthetic derivatives in cancer and non-cancer cells. In cancer cells the benzocamalexin (BC) displayed the most potent activity with an IC value of 23.3-30.1 μmol/L. On the other hand, minimal toxicity (IC>100.0 μmol/L) in non-cancer cells was observed. Based on these results, BC was selected for further studies. Flow cytometric analysis revealed a BC-induced arrest of the cell cycle in the G2 phase associated with downregulation of α-tubulin, α1-tubulin, β5-tubulin expression. These findings suggest that the inhibitory effect of BC is mediated via inhibition of microtubule formation. Moreover, BC downregulated the expression of microtubule-related protein indicating the effect of this compound on microtubule assembly. After treatment with BC increase of the sub-G DNA content fraction was noted which is considered to be a marker of apoptotic cell death. Apoptosis was also confirmed by DNA fragmentation assay. Moreover, quantitative real-time PCR showed that BC downregulated the expression of antiapoptotic genes Bcl-2 and Bcl-xL and upregulated the expression of proapoptotic Bax. Taken together, our study suggests that the blockade of cell cycle progression and initiation of apoptosis may play an important role in the antiproliferative activity of BC in human cancer cells.

A microfluidic systems biology approach for live single-cell mitochondrial ROS imaging

Most current studies of reactive oxygen species (ROS) production report globally averaged measurements within the cell; however, ROS can be produced in distinct subcellular locations and have local effects in their immediate vicinity. A microfluidic platform for high-throughput single-cell imaging allows mitochondrial ROS production to be monitored as varying in both space and time. Using this systems biology approach, single-cell variability can be viewed within a population. We discuss single-cell monitoring of contributors to mitochondrial redox state-mitochondrial hydrogen peroxide or superoxide-through the use of a small molecule probe or targeted fluorescent reporter protein. Jurkat T lymphoma cells were stimulated with antimycin A and imaged in an arrayed microfluidic device over time. Differences in single-cell responses were observed as a function of both inhibitor concentration and type of ROS measurement used.

The phytoalexin camalexin mediates cytotoxicity towards aggressive prostate cancer cells via reactive oxygen species

Camalexin is a phytoalexin that accumulates in various cruciferous plants upon exposure to environmental stress and plant pathogens. Besides moderate antibacterial and antifungal activity, camalexin was reported to also exhibit antiproliferative and cancer chemopreventive effects in breast cancer and leukemia. We studied the cytotoxic effects of camalexin treatment on prostate cancer cell lines and whether this was mediated by reactive oxygen species (ROS) generation. As models, we utilized LNCaP and its aggressive subline, C4-2, as well as ARCaP cells stably transfected with empty vector (Neo) control or constitutively active Snail cDNA that represents an epithelial to mesenchymal transition (EMT) model and displays increased cell migration and tumorigenicity. We confirmed previous studies showing that C4-2 and ARCaP-Snail cells express more ROS than LNCaP and ARCaP-Neo, respectively. Camalexin increased ROS, decreased cell proliferation, and increased apoptosis more significantly in C4-2 and ARCaP-Snail cells as compared to LNCaP and ARCaP-Neo cells, respectively, while normal prostate epithelial cells (PrEC) were unaffected. Increased caspase-3/7 activity and increased cleaved PARP protein shown by Western blot analysis was suggestive of increased apoptosis. The ROS scavenger N-acetyl cysteine (NAC) antagonized the effects of camalexin, whereas the addition of exogenous hydrogen peroxide potentiated the effects of camalexin, showing that camalexin is mediating its effects through ROS. In conclusion, camalexin is more potent in aggressive prostate cancer cells that express high ROS levels, and this phytoalexin has a strong potential as a novel therapeutic agent for the treatment of especially metastatic prostate cancer.

The effects of MicroRNA transfections on global patterns of gene expression in ovarian cancer cells are functionally coordinated

Background

MicroRNAs (miRNAs) are a class of small RNAs that have been linked to a number of diseases including cancer. The potential application of miRNAs in the diagnostics and therapeutics of ovarian and other cancers is an area of intense interest. A current challenge is the inability to accurately predict the functional consequences of exogenous modulations in the levels of potentially therapeutic miRNAs.

Methods

In an initial effort to systematically address this issue, we conducted miRNA transfection experiments using two miRNAs (miR-7, miR-128). We monitored the consequent changes in global patterns of gene expression by microarray and quantitative (real-time) polymerase chain reaction. Network analysis of the expression data was used to predict the consequence of each transfection on cellular function and these predictions were experimentally tested.

Results

While ~20% of the changes in expression patterns of hundreds to thousands of genes could be attributed to direct miRNA-mRNA interactions, the majority of the changes are indirect, involving the downstream consequences of miRNA-mediated changes in regulatory gene expression. The changes in gene expression induced by individual miRNAs are functionally coordinated but distinct between the two miRNAs. MiR-7 transfection into ovarian cancer cells induces changes in cell adhesion and other developmental networks previously associated with epithelial-mesenchymal transitions (EMT) and other processes linked with metastasis. In contrast, miR-128 transfection induces changes in cell cycle control and other processes commonly linked with cellular replication.

Conclusions

The functionally coordinated patterns of gene expression displayed by different families of miRNAs have the potential to provide clinicians with a strategy to treat cancers from a systems rather than a single gene perspective.

Automated Multistep Continuous Flow Synthesis of 2-(1H-Indol-3-yl)thiazole Derivatives

The multistep continuous flow assembly of 2-(1H-indol-3-yl)thiazoles using a Syrris AFRICA® synthesis station is reported. Sequential Hantzsch thiazole synthesis, deketalization and Fischer indole synthesis provides rapid and efficient access to highly functionalized, pharmacologically significant 2-(1H-indol-3-yl)thiazoles. These complex, drug-like small molecules are generated in reaction times of less than 15 min and in high yields (38%-82% over three chemical steps without isolation of intermediates).