Comprehensive review of Bcl-2 family proteins in cancer apoptosis: Therapeutic strategies and promising updates of natural bioactive compounds and small molecules.

Cancer has a considerably higher fatality rate than other diseases globally and is one of the most lethal and profoundly disruptive ailments. The increasing incidence of cancer among humans is one of the greatest challenges in the field of healthcare. A significant factor in the initiation and progression of tumorigenesis is the dysregulation of physiological processes governing cell death, which results in the survival of cancerous cells. B-cell lymphoma 2 (Bcl-2) family members play important roles in several cancer-related processes. Drug research and development have identified various promising natural compounds that demonstrate potent anticancer effects by specifically targeting Bcl-2 family proteins and their associated signaling pathways. This comprehensive review highlights the substantial roles of Bcl-2 family proteins in regulating apoptosis, including the intricate signaling pathways governing the activity of these proteins, the impact of reactive oxygen species, and the crucial involvement of proteasome degradation and the stress response. Furthermore, this review discusses advances in the exploration and potential therapeutic applications of natural compounds and small molecules targeting Bcl-2 family proteins and thus provides substantial scientific information and therapeutic strategies for cancer management.

Inhibition of histone deacetylase 6 destabilizes ERK phosphorylation and suppresses cancer proliferation via modulation of the tubulin acetylation-GRP78 interaction.

BACKGROUND: The leading cause of cancer-related mortality worldwide is lung cancer, and its clinical outcome and prognosis are still unsatisfactory. The understanding of potential molecular targets is necessary for clinical implications in precision diagnostic and/or therapeutic purposes. Histone deacetylase 6 (HDAC6), a major deacetylase enzyme, is a promising target for cancer therapy; however, the molecular mechanism regulating cancer pathogenesis is largely unknown. METHODS: The clinical relevance of HDAC6 expression levels and their correlation with the overall survival rate were analyzed based on the TCGA and GEO databases. HDAC6 expression in clinical samples obtained from lung cancer tissues and patient-derived primary lung cancer cells was evaluated using qRT-PCR and Western blot analysis. The potential regulatory mechanism of HDAC6 was identified by proteomic analysis and validated by immunoblotting, immunofluorescence, microtubule sedimentation, and immunoprecipitation-mass spectrometry (IP-MS) assays using a specific inhibitor of HDAC6, trichostatin A (TSA) and RNA interference to HDAC6 (siHDAC6). Lung cancer cell growth was assessed by an in vitro 2-dimensional (2D) cell proliferation assay and 3D tumor spheroid formation using patient-derived lung cancer cells. RESULTS: HDAC6 was upregulated in lung cancer specimens and significantly correlated with poor prognosis. Inhibition of HDAC6 by TSA and siHDAC6 caused downregulation of phosphorylated extracellular signal-regulated kinase (p-ERK), which was dependent on the tubulin acetylation status. Tubulin acetylation induced by TSA and siHDAC6 mediated the dissociation of p-ERK on microtubules, causing p-ERK destabilization. The proteomic analysis demonstrated that the molecular chaperone glucose-regulated protein 78 (GRP78) was an important scaffolder required for p-ERK localization on microtubules, and this phenomenon was significantly inhibited by either TSA, siHDAC6, or siGRP78. In addition, suppression of HDAC6 strongly attenuated an in vitro 2D lung cancer cell growth and an in vitro 3D patient derived-lung cancer spheroid growth. CONCLUSIONS: HDAC6 inhibition led to upregulate tubulin acetylation, causing GRP78-p-ERK dissociation from microtubules. As a result, p-ERK levels were decreased, and lung cancer cell growth was subsequently suppressed. This study reveals the intriguing role and molecular mechanism of HDAC6 as a tumor promoter, and its inhibition represents a promising approach for anticancer therapy.

Light-Mediated Transformation of Renieramycins and Semisynthesis of 4'-Pyridinecarbonyl-Substituted Renieramycin-Type Derivatives as Potential Cytotoxic Agents against Non-Small-Cell Lung Cancer Cells.

The semisynthesis of renieramycin-type derivatives was achieved under mild and facile conditions by attaching a 1,3-dioxole-bridged phenolic moiety onto ring A of the renieramycin structure and adding a 4'-pyridinecarbonyl ester substituent at its C-5 or C-22 position. These were accomplished through a light-induced intramolecular photoredox reaction using blue light (4 W) and Steglich esterification, respectively. Renieramycin M (4), a bis-tetrahydroisoquinolinequinone compound isolated from the Thai blue sponge (Xestospongia sp.), served as the starting material. The cytotoxicity of the 10 natural and semisynthesized renieramycins against non-small-cell lung cancer (NSCLC) cell lines was evaluated. The 5-O-(4'-pyridinecarbonyl) renieramycin T (11) compound exhibited high cytotoxicity with half-maximal inhibitory concentration (IC50) values of 35.27 ± 1.09 and 34.77 ± 2.19 nM against H290 and H460 cells, respectively. Notably, the potency of compound 11 was 2-fold more than that of renieramycin T (7) and equal to those of 4 and doxorubicin. Interestingly, the renieramycin-type derivatives with a hydroxyl group at C-5 and C-22 exhibited weak cytotoxicity. In silico molecular docking and dynamics studies confirmed that the mitogen-activated proteins, kinase 1 and 3 (MAPK1 and MAPK3), are suitable targets for 11. Thus, the structure-cytotoxicity study of renieramycins was extended to facilitate the development of potential anticancer agents for NSCLC cells.

Overexpressing Carotenoid Biosynthetic Genes in Synechocystis sp. PCC 6803 Improved Intracellular Pigments and Antioxidant Activity, Which Can Decrease the Viability and Proliferation of Lung Cancer Cells In Vitro.

In the antioxidant system in cyanobacteria, non-enzymatic antioxidants, such as carotenoids, are considered good candidates for coping with oxidative stress, particularly light stress, and pharmaceutical therapeutic applications. A significant amount of carotenoid accumulation has been recently improved by genetic engineering. In this study, to achieve higher carotenoid production with higher antioxidant activity, we successfully constructed five Synechocystis sp. PCC 6803 strains overexpressing (OX) native genes related to the carotenoids biosynthetic pathway, including OX_CrtB, OX_CrtP, OX_CrtQ, OX_CrtO, and OX_CrtR. All of the engineered strains maintained a significant quantity of myxoxanthophyll, while increasing zeaxanthin and echinenone accumulation. In addition, higher components of zeaxanthin and echinenone were noted in all OX strains, ranging from 14 to 19% and from 17 to 22%, respectively. It is worth noting that the enhanced echinenone component responded to low light conditions, while the increased ß-carotene component contributed to a high light stress response. According to the higher antioxidant activity of all OX strains, the carotenoid extracts presented lower IC50 in lung cancer cell lines H460 and A549, with values less than 157 and 139 µg/mL, respectively, when compared with those of WTc, particularly OX_CrtR and OX_CrtQ. A higher proportion of zeaxanthin and ß-carotene in OX_CrtR and OX_CrtQ, respectively, may considerably contribute to the ability to treat lung cancer cells with antiproliferative and cytotoxic effects.

Tiered approach for evaluation of anti-melanogenic activity of trans-N-coumaroyltyramine derivatives.

Skin hyperpigmentation is commonly treated by topical drug application. Several naturally occurring compounds exhibit attractive biological effects including anti-melanogenic activity. Chemically modified derivatives of those compounds are expected to be more efficient. However, efficacy and safety testing processes are of significant consideration to identify the most effective compound among them. Herein, we demonstrated a tiered approach to investigate the antipigmentation activity of 17 trans-N-coumaroyltyramine derivatives. First, we evaluated the in chemico antityrosinase activity, then the cytotoxicity of the most potent derivatives using a mitochondrial activity-based assay, followed with the in vitro anti-melanogenic activity in two dimensional (2D) monolayer human melanocytes. The selected derivatives were topically applied on a three dimensional (3D) pigmented-reconstructed human epidermis (pRhE) containing melanocytes and keratinocytes to evaluate their depigmenting activity. Two of the 17 derivatives displayed a significant reduction in pigmentation in the 3D pRhE, comparable to kojic acid, a known tyrosinase inhibitor. In addition, a molecular docking experiment indicated an interaction of the three derivatives and tyrosinase, suggesting that these derivatives have potent anti-melanogenic activity through tyrosinase inhibition. Our findings provide an alternative approach for investigating skin-whitening agents, thereby facilitating the research and development of skin-whitening products that need not be tested on animals.

Aspiletrein A Induces Apoptosis Cell Death via Increasing Reactive Oxygen Species Generation and AMPK Activation in Non-Small-Cell Lung Cancer Cells.

Lung cancer remains a leading cause of death in cancer patients, and deregulation of apoptosis is a serious concern in clinical practice, even though therapeutic intervention has been greatly improved. Plants are a versatile source of biologically active compounds for anticancer drug discovery, and aspiletrein A (AA) is a steroidal saponin isolated from Aspidistra letreae that has a potent cytotoxic effect on various cancer cell lines. In this study, we investigated and determined the underlying molecular mechanism by which AA induces apoptosis. AA strongly induced apoptosis in NSCLC cells by mediating ROS generation and thereby activating AMP-activated protein kinase (AMPK) signaling. Consequently, downstream signaling and levels of phosphorylated mTOR and Bcl-2 were significantly decreased. Pretreatment with either an antioxidant, N-acetylcysteine, or an AMPK inhibitor, compound C, could reverse the apoptosis-inducing effect and counteract the effect of AA on the AMPK signaling pathway. Decreased levels of Bcl-2 were due to AA-mediating Bcl-2 degradation via a ROS/AMPK/mTOR axis-dependent proteasomal mechanism. Consistently, the apoptotic-inducing effect of AA was also observed in patient-derived malignant lung cancer cells, and it suppressed an in vitro 3D-tumorigenesis. This study identified the underlying mechanism of AA on lung cancer apoptosis, thereby facilitating potential research and development of this compound for further clinical implications.

Evaluating the Expression and Prognostic Value of Genes Encoding Microtubule-Associated Proteins in Lung Cancer.

Microtubule-associated proteins (MAPs) play essential roles in cancer development. This study aimed to identify transcriptomic biomarkers among MAP genes for the diagnosis and prognosis of lung cancer by analyzing differential gene expressions and correlations with tumor progression. Gene expression data of patients with lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC) from the Cancer Genome Atlas (TCGA) database were used to identify differentially expressed MAP genes (DEMGs). Their prognostic value was evaluated by Kaplan-Meier and Cox regression analysis. Moreover, the relationships between alterations in lung cancer hallmark genes and the expression levels of DEMGs were investigated. The candidate biomarker genes were validated using three independent datasets from the Gene Expression Omnibus (GEO) database and by quantitative reverse transcription polymerase chain reaction (qRT-PCR) on clinical samples. A total of 88 DEMGs were identified from TCGA data. The 20 that showed the highest differential expression were subjected to association analysis with hallmark genes. Genetic alterations in TP53, EGFR, PTEN, NTRK1, and PIK3CA correlated with the expression of most of these DEMGs. Of these, six candidates-NUF2, KIF4A, KIF18B, DLGAP5, NEK2, and LRRK2-were significantly differentially expressed and correlated with the overall survival (OS) of the patients. The mRNA expression profiles of these candidates were consistently verified using three GEO datasets and qRT-PCR on patient lung tissues. The expression levels of NUF2, KIF4A, KIF18B, DLGAP5, NEK2, and LRRK2 can serve as diagnostic biomarkers for LUAD and LUSC. Moreover, the first five can serve as prognostic biomarkers for LUAD, while LRRK2 can be a prognostic biomarker for LUSC. Our research describes the novel role and potential application of MAP-encoding genes in clinical practice.

Target Identification of 22-(4-Pyridinecarbonyl) Jorunnamycin A, a Tetrahydroisoquinoline Derivative from the Sponge Xestospongia sp., in Mediating Non-Small-Cell Lung Cancer Cell Apoptosis.

A dysregulation of the cell-death mechanism contributes to poor prognosis in lung cancer. New potent chemotherapeutic agents targeting apoptosis-deregulating molecules have been discovered. In this study, 22-(4-pyridinecarbonyl) jorunnamycin A (22-(4'py)-JA), a synthetic derivative of bistetrahydroisoquinolinequinone from the Thai blue sponge, was semisynthesized by the Steglich esterification method, and its pharmacological mechanism in non-small-cell lung cancer (NSCLC) was elucidated by a network pharmacology approach. All predicted targets of 22-(4'py)-JA and genes related to NSCLC were retrieved from drug-target and gene databases. A total of 78 core targets were identified, and their associations were analyzed by STRING and Cytoscape. Gene ontology and KEGG pathway enrichment analyses revealed that molecules in mitogen-activated protein kinase (MAPK) signaling were potential targets of 22-(4'py)-JA in the induction of NSCLC apoptosis. In silico molecular docking analysis displayed a possible interaction of ERK1/2 and MEK1 with 22-(4'py)-JA. In vitro anticancer activity showed that 22-(4'py)-JA has strong cytotoxic and apoptosis-inducing effects in H460, H292 and A549 NSCLC cells. Furthermore, immunoblotting confirmed that 22-(4'py)-JA induced apoptotic cell death in an ERK/MEK/Bcl-2-dependent manner. The present study demonstrated that 22-(4'py)-JA exhibited a potent anticancer effect that could be further developed for clinical application and showed that network pharmacology approaches are a powerful tool to illustrate the molecular pathways of new drugs or compounds.

Erianthridin Induces Non-small Cell Lung Cancer Cell Apoptosis through the Suppression of Extracellular Signal-regulated Kinase Activity.

Due to the high mortality of lung cancer, natural derivative compounds have been promoted as versatile sources for anticancer drug discovery. Erianthridin, a phenanthrene compound isolated from Dendrobium formosum, exhibits intriguing apoptosis-inducing effects in non-small cell lung cancer cells. Apoptotic nuclei staining assays showed that apoptotic cells with DNA fragmentation and apoptotic bodies were apparent, and an increase in annexin V-FITC-positive cells were found in cells treated with erianthridin. The apoptosis protein markers for cleaved caspase-3 and cleaved poly-ADP-ribose polymerase were significantly upregulated in response to erianthridin. A mechanistic investigation revealed that erianthridin was able to attenuate extracellular signal-regulated kinase activity and thereby mediate apoptosis through the modulation of Bcl-2 family protein levels. U0126, an extracellular signal-regulated kinase inhibitor, augmented the apoptosis-inducing effect of erianthridin; in contrast, overexpression of exogenous extracellular signal-regulated kinase substantially abrogated erianthridin activity. Furthermore, an in vitro 3D tumorigenesis assay showed that erianthridin was able to potentially suppress lung cancer cell proliferation. This study is the first to report a promising cytotoxic effect of erianthridin, which provides preclinical evidence for further research and development of this compound.

CAMSAP3 maintains neuronal polarity through regulation of microtubule stability.

The molecular mechanisms that guide each neuron to become polarized, forming a single axon and multiple dendrites, remain unknown. Here we show that CAMSAP3 (calmodulin-regulated spectrin-associated protein 3), a protein that regulates the minus-end dynamics of microtubules, plays a key role in maintaining neuronal polarity. In mouse hippocampal neurons, CAMSAP3 was enriched in axons. Although axonal microtubules were generally acetylated, CAMSAP3 was preferentially localized along a less-acetylated fraction of the microtubules. CAMSAP3-mutated neurons often exhibited supernumerary axons, along with an increased number of neurites having nocodazole-resistant/acetylated microtubules compared with wild-type neurons. Analysis using cell lines showed that CAMSAP3 depletion promoted tubulin acetylation, and conversely, mild overexpression of CAMSAP3 inhibited it, suggesting that CAMSAP3 works to retain nonacetylated microtubules. In contrast, CAMSAP2, a protein related to CAMSAP3, was detected along all neurites, and its loss did not affect neuronal polarity, nor did it cause increased tubulin acetylation. Depletion of α-tubulin acetyltransferase-1 (αTAT1), the key enzyme for tubulin acetylation, abolished CAMSAP3 loss-dependent multiple-axon formation. These observations suggest that CAMSAP3 sustains a nonacetylated pool of microtubules in axons, interfering with the action of αTAT1, and this process is important to maintain neuronal polarity.

Targeting the PI3K/AKT/mTOR Signaling Pathway in Lung Cancer: An Update Regarding Potential Drugs and Natural Products.

Lung cancer is one of the most common cancers and has a high mortality rate. Due to its high incidence, the clinical management of the disease remains a major challenge. Several reports have documented a relationship between the phosphatidylinositol-3-kinase (PI3K)/ protein kinase B (AKT)/ mammalian target of rapamycin (mTOR) pathway and lung cancer. The recognition of this pathway as a notable therapeutic target in lung cancer is mainly due to its central involvement in the initiation and progression of the disease. Interest in using natural and synthetic medications to target these signaling pathways has increased in recent years, with promising results in vitro, in vivo, and in clinical trials. In this review, we focus on the current understanding of PI3K/AKT/mTOR signaling in tumor development. In addition to the signaling pathway, we highlighted the therapeutic potential of recently developed PI3K/AKT/mTOR inhibitors based on preclinical and clinical trials.

Loss of CAMSAP3 promotes EMT via the modification of microtubule-Akt machinery.

Epithelial-to-mesenchymal transition (EMT) plays pivotal roles in a variety of biological processes, including cancer invasion. Although EMT involves alterations of cytoskeletal proteins such as microtubules, the role of microtubules in EMT is not fully understood. Microtubule dynamics are regulated by microtubule-binding proteins, and one such protein is CAMSAP3, which binds the minus-end of microtubules. Here, we show that CAMSAP3 is important to preserve the epithelial phenotypes in lung carcinoma cells. Deletion of CAMSAP3 in human lung carcinoma-derived cell lines showed that CAMSAP3-deficient cells acquired increased mesenchymal features, mostly at the transcriptional level. Analysis of the mechanisms underlying these changes demonstrated that tubulin acetylation was dramatically increased following CAMSAP3 removal, leading to the upregulation of Akt proteins (also known as protein kinase B proteins, hereafter Akt) activity, which is known to promote EMT. These findings suggest that CAMSAP3 functions to protect lung carcinoma cells against EMT by suppressing Akt activity via microtubule regulation and that CAMSAP3 loss promotes EMT in these cells.This article has an associated First Person interview with the first author of the paper.

α7-Nicotinic acetylcholine receptor antagonist QND7 suppresses non-small cell lung cancer cell proliferation and migration via inhibition of Akt/mTOR signaling.

Lung cancer, one of the most commonly found carcinoma type, has the highest mortality rate in cancer patients worldwide. Therapeutic interventions targeting to lung cancer become remaining the world significant challenge. Recently, the α7-nicotinic acetylcholine receptor (α7-nAChR) was reported to play an important role in the mechanism underlying lung cancer progression, being intriguing drug target for lung cancer therapy. Hence, the top four α7-nAChR antagonists (QND7, PPRD10, PPRD11 and PPRD12) among our previously developed ligands were proceeded to the in vitro anti-cancer evaluations in non-small cell lung cancer (NSCLC) cell lines (H460 and A549). In this study, we found that QND7 exhibited the highest cytotoxic effect and induced cell apoptosis in both cell lines at a level comparable to cisplatin, whereas the PPRD compounds showed much lower cytotoxicity. Low doses of QND7 and PPRD11 were able to suppress H460 and A549 cell proliferation, whereas PPRD10 and PPRD12 were considered ineffective. In an in vitro wound healing assay, QND7-treatment showed the greatest suppression of H460 and A549 cell migration. The variations in the anti-cancer activities of PPRD compounds might be, at least in part of, their non-selective antagonisms to serotonin receptor (5-HT3) and α4ß2-nAChR. Further investigation revealed that QND7 was able to minimize protein kinase B/mammalian target of rapamycin (Akt/mTOR) activity, in correlating to its anti-cancer effects. These findings warrant QND7 for further preclinical evaluation and demonstrate the potential of α7-nAChR as cancer drug target.

Ti0.8O2 Nanosheets Inhibit Lung Cancer Stem Cells by Inducing Production of Superoxide Anion.

Recent research into the cancer stem cell (CSC) concept has driven progress in the understanding of cancer biology and has revealed promising CSC-specific targets for drug discovery efforts. As malignancies of lung cancer have been shown to be strongly associated with activities of CSCs, we examined the effects of Ti0.8O2 nanosheets on these cells. Here we show that the nanosheets target lung CSCs but not normal primary dermal papilla (DP) stem cells. Whereas Ti0.8O2 caused a dramatic apoptosis along with a decrease in CSC phenotypes, in primary human DP cells such effects of nanosheets have been minimal. Nanosheets reduced the ability of lung cancer cells to generate three-dimensional tumor spheroids, lung CSC markers (CD133 and ALDH1A1), and CSC transcription factors (Nanog and Oct-4). Ti0.8O2 nanosheets reduced CSC signaling through mechanisms involving suppression of protein kinase B (AKT) and Notch-1 pathways. In addition, the nanosheets inhibited the migration and invasive activities of lung cancer cells and reduced epithelial-to-mesenchymal transition (EMT) markers as N-cadherin, vimentin, and Slug, as well as metastasis-related integrins (integrin-αv and integrin-ß1). Importantly, we found that the selectivity of the Ti0.8O2 nanosheets in targeting cancer cells was mediated by induction of cellular superoxide anion in cancerous but not normal cells. Inhibition of nanosheet-induced superoxide anion restored the suppression of CSC and EMT in cancer cells. These findings demonstrate a promising distinctive effect of Ti0.8O2 nanosheets on lung CSC that may lead to opportunities to use such a nanomaterial in cancer therapy.

Molecular mechanisms of natural compounds in cell death induction and sensitization to chemotherapeutic drugs in lung cancer.

Cancer remains one of the leading causes of death worldwide, especially lung cancer. Chemotherapeutic drugs are commonly used for lung cancer treatment; nonetheless, undesirable side effects and drug resistance remain major challenges for therapeutic success. Therefore, harmless and effective treatments against lung cancer are urgently required. The use of natural phytochemical products, in single or combinatorial therapy, is an emerging strategy for prevention and cure of cancer because of the various remarkable anticancer properties of these compounds. Cell death, which primarily occurs via apoptosis and nonapoptotic mechanisms (necrosis, autophagy, and cellular senescence), is one of the antineoplastic effects of natural compounds. In this review, we highlight representative plant-derived compounds with cancer chemopreventive and sensitizing effects in combination with chemotherapeutic drugs with various cell death-inducing mechanisms. Relevant molecular mechanisms implicated in the pharmacological effects of these natural compounds are discussed. Overall, this review provides a reference and new perspective for application of phytochemical agents as potential anti-lung cancer drugs for further cancer drug research and development.

Cancer Stem Cell-Suppressing Activity of Chrysotoxine, a Bibenzyl from Dendrobium pulchellum.

Cancer stem cells (CSCs) have been recognized as rare populations driving cancer progression, metastasis, and drug resistance in leading cancers. Attempts have been made toward identifying compounds that specifically target these CSCs. Therefore, investigations of novel therapeutic strategies for CSC targeting are required. The cytotoxic effects of chrysotoxine on human non-small cell lung cancer-derived H460 and H23 cells were evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The effects of chrysotoxine suppression of CSC-like phenotypes were determined in CSC-rich populations and primary CSCs in three-dimensional (3D) culture and in an extreme limiting dilution assay. Expression of CSC markers and associated proteins was determined by Western blot analyse and flow cytometry. We have reported herein the CSC-suppressing activity of chrysotoxine, a bibenzyl compound isolated from Dendrobium pulchellum We have shown, to our knowledge for the first time, that chrysotoxine dramatically suppresses CSC-like phenotypes of H460 and H23 cells. Treatment with chrysotoxine significantly reduced the viability of 3D CSC-rich populations and concomitantly decreased known CSC markers. Chrysotoxine suppressed CSC phenotypes through downregulation of Src/protein kinase B (Akt) signaling. Active (phosphorylated Y416) Src was shown to regulate cancer stemness, since ectopic overexpression of Src strongly activated Akt and subsequently enhanced pluripotency transcription factor SRY (sex-determining region Y)-box 2 (Sox2)- mediating CSC phenotypes, whereas the short hairpin RNA of Src and an Src inhibitor (dasatinib) suppressed Akt, Sox2, and CSC properties. Importantly, chrysotoxine was shown to suppress active Src/Akt signaling and in turn depleted Sox2-mediated CSCs. Our findings indicate a novel CSC-targeted role of chrysotoxine and its regulation by Src/Akt and Sox2, which may be exploited for cancer treatment.

The attenuation of epithelial to mesenchymal transition and induction of anoikis by gigantol in human lung cancer H460 cells.

Lung cancer has been the major cause of death within patients due to the high metastatic rate. One of the most essential processes of metastasis is the ability of cancer cells to resist the programmed cell death in a detached condition called anoikis. The discoveries of new natural compound that is able to sensitize anoikis in cancer cells have garnered the most interest in cancer pharmaceutical science. Gigantol, a bibenzyl compound extracted from Dendrobium draconis, has been a promising natural derived compound for cancer therapy due to several cytotoxic effects in cancer cells. This study has demonstrated for the first time that gigantol significantly decreases lung cancer cells' viability in a detached condition through anoikis and anchorage-independent assays. Western blotting analysis reveals that gigantol greatly decreases epithelial to mesenchymal transition (EMT) markers including N-cadherin, vimentin, and Slug leading to a significant suppression of protein kinase B (AKT), extracellular signal-regulated kinase (ERK), and caveolin-1 (cav-1) survival pathways during the detached condition. Therefore, gigantol could be a potential cancer therapeutic compound suggesting for further development for cancer therapy.

Nitric oxide induces cancer stem cell-like phenotypes in human lung cancer cells.

Even though tremendous advances have been made in the treatment of cancers during the past decades, the success rate among patients with cancer is still dismal, largely because of problems associated with chemo/radioresistance and relapse. Emerging evidence has indicated that cancer stem cells (CSCs) are behind the resistance and recurrence problems, but our understanding of their regulation is limited. Rapid reversible changes of CSC-like cells within tumors may result from the effect of biological mediators found in the tumor microenvironment. Here we show how nitric oxide (NO), a key cellular modulator whose level is elevated in many tumors, affects CSC-like phenotypes of human non-small cell lung carcinoma H292 and H460 cells. Exposure of NO gradually altered the cell morphology toward mesenchymal stem-like shape. NO exposure promoted CSC-like phenotype, indicated by increased expression of known CSC markers, CD133 and ALDH1A1, in the exposed cells. These effects of NO on stemness were reversible after cessation of the NO treatment for 7 days. Furthermore, such effect was reproducible using another NO donor, S-nitroso-N-acetylpenicillamine. Importantly, inhibition of NO by the known NO scavenger 2-(4-carboxy-phenyl)-4,4,5,5 tetramethylimidazoline-1-oxy-3-oxide strongly inhibited CSC-like aggressive cellular behavior and marker expression. Last, we unveiled the underlying mechanism of NO action through the activation of caveolin-1 (Cav-1), which is upregulated by NO and is responsible for the aggressive behavior of the cells, including anoikis resistance, anchorage-independent cell growth, and increased cell migration and invasion. These findings indicate a novel role of NO in CSC regulation and its importance in aggressive cancer behaviors through Cav-1 upregulation.

Caveolin-1 regulates metastatic behaviors of anoikis resistant lung cancer cells.

Caveolin-1 (Cav-1), a protein component of cellular membrane, has been reported to regulate several cancer cell behaviors. However, its role on cancer metastasis in anoikis resistant cells is unknown. The present study aimed to investigate the correlation between Cav-1 level and aggressive behaviors of anoikis resistant cancer cells. Cav-1 and ShRNACav-1 stably transfected lung carcinoma cells, and anoikis resistant H_AR1 and H_AR2 cells expressing different levels of Cav-1 were subjected to anoikis, cell growth, anchorage-independent growth, extracellular matrix adhesion, cisplatin sensitivity, migration, and invasion assays. The correlations between cellular Cav-1 level and such cancer aggressive behaviors were evaluated. Results revealed that anoikis resistant lung cancer cells as well as Cav-1 overexpressing cells exhibit a significant increase in anchorage-independent growth, extracellular matrix adhesion, migration, and invasion in comparison to those of their parental H460 cells. Knock-down of Cav-1 by ShRNA transfection was able to reverse such metastatic potentials in H_AR2 cells. In addition, basal Cav-1 level of these cells was positively correlated with anoikis resistance, anchorage-independent growth, migration, and invasion behaviors of the cells, whereas such Cav-1 level showed poor correlation to cisplatin sensitivity, cell adhesion, and growth in attached condition. These findings give more information regarding role of Cav-1 in the regulation of behaviors of lung cancer cells.