Attenuation of PI3K-Akt-mTOR Pathway to Reduce Cancer Stemness on Chemoresistant Lung Cancer Cells by Shikonin and Synergy with BEZ235 Inhibitor

Lung cancer is considered the number one cause of cancer-related deaths worldwide. Although current treatments initially reduce the lung cancer burden, relapse occurs in most cases; the major causes of mortality are drug resistance and cancer stemness. Recent investigations have provided evidence that shikonin generates various bioactivities related to the treatment of cancer. We used shikonin to treat multi-resistant non-small lung cancer cells (DOC-resistant A549/D16, VCR-resistant A549/V16 cells) and defined the anti-cancer efficacy of shikonin. Our results showed shikonin induces apoptosis in these ABCB1-dependent and independent chemoresistance cancer sublines. Furthermore, we found that low doses of shikonin inhibit the proliferation of lung cancer stem-like cells by inhibiting spheroid formation. Concomitantly, the mRNA level and protein of stemness genes (Nanog and Oct4) were repressed significantly on both sublines. Shikonin reduces the phosphorylated Akt and p70s6k levels, indicating that the PI3K/Akt/mTOR signaling pathway is downregulated by shikonin. We further applied several signaling pathway inhibitors that have been used in anti-cancer clinical trials to test whether shikonin is suitable as a sensitizer for various signaling pathway inhibitors. In these experiments, we found that low doses shikonin and dual PI3K-mTOR inhibitor (BEZ235) have a synergistic effect that inhibits the spheroid formation from chemoresistant lung cancer sublines. Inhibiting the proliferation of lung cancer stem cells is believed to reduce the recurrence of lung cancer; therefore, shikonin's anti-drug resistance and anti-cancer stem cell activities make it a highly interesting molecule for future combined lung cancer therapy.

Combination treatment of Src inhibitor Saracatinib with GMI, a Ganoderma microsporum immunomodulatory protein, induce synthetic lethality via autophagy and apoptosis in lung cancer cells

Saracatinib is an oral Src-kinase inhibitor and has been studied in preclinical models and clinical trials of cancer therapy. GMI, a fungal immunomodulatory protein from Ganoderma microsporum, possesses antitumor capacity. The aim of this study is to evaluate the cytotoxic effect of combination treatment with saracatinib and GMI on parental and pemetrexed-resistant lung cancer cells. Cotreatment with saracatinib and GMI induced synergistic and additive cytotoxic effect in A549 and A400 cells by annexin V/propidium iodide assay and combination index. Using western blot assay, saracatinib, and GMI combined treatment synergistically induced caspase-7 activation in A549 cells. Different from A549 cells, saracatinib and GMI cotreatment markedly increased LC3B-II in A400 cells. ATG5 silencing abolished the caspase-7 activation and reduced cell death in A549 cells after cotreatment. This is the first study to provide a novel strategy of treating lung cancer with or without drug resistance via combination treatment with GMI and saracatinib.

CD133 inhibition via autophagic degradation in pemetrexed-resistant lung cancer cells by GMI, a fungal immunomodulatory protein from Ganoderma microsporum

Background

Adaptive drug resistance is an unfavourable prognostic factor in cancer therapy. Pemetrexed-resistant lung cancer cells possess high-metastatic ability via ERK–ZEB1 pathway-activated epithelial–mesenchymal transition. GMI is a fungal immunomodulatory protein that suppresses the survival of several cancer cells.

Methods

Cell viability was analysed by MTT, clonogenic, tumour spheroid, and cancer stem cell sphere assays. Western blot assay was performed to detect the protein expression. Chemical inhibitors and ATG5 shRNA were used to inhibit autophagy. Tumour growth was investigated using xenograft mouse model.

Results

GMI decreased the viability with short- and long-term effects and induced autophagy but not apoptosis in A549/A400 cells. GMI downregulated the expression levels of CD133, CD44, NANOG and OCT4. GMI induces the protein degradation of CD133 via autophagy. CD133 silencing decreased the survival and proliferation of A549/A400 cells. GMI suppressed the growth and CD133 expression of A549/A400 xenograft tumour.

Conclusions

This study is the first to reveal the novel function of GMI in eliciting cytotoxic effect and inhibiting CD133 expression in pemetrexed-resistant lung cancer cells via autophagy. Our finding provides evidence that CD133 is a potential target for cancer therapy.

Anticancer Effects of Antihypertensive L-Type Calcium Channel Blockers on Chemoresistant Lung Cancer Cells via Autophagy and Apoptosis

Purpose

Hypertension and cancer are frequently found comorbidity occurring in same individual. This study was intended to evaluate the anticancer effects of commonly used antihypertensive medications and chemotherapy on chemoresistant lung cancer cells.

Methods

Calcium channel blockers (CCBs), including Verapamil, Diltiazem, and Nifedipine, either alone or combined with docetaxel (DOC) or vincristine (VCR) were used to treat A549 lung adenocarcinoma chemoresistant sublines. Cell viability was determined by MTT assay, and colony formation assay was used to demonstrate the long-term effect of CCBs on proliferation of the sublines. Apoptosis was evaluated by Annexin V assay and autophagy intensity was quantitated from acidic vesicular organelle formation. Pan-caspase inhibitor, shATG5 interference and chloroquine were applied to study the roles of Verapamil on apoptosis and autophagy, with related proteins verified by Western blot analysis.

Results

Results show that 10 μM of Verapamil and Diltiazem, but not Nifedipine, differentially induce autophagy in DOC-resistant or VCR-resistant A549 cells, respectively. When CCBs are combined with DOC or VCR to treat the sublines, 10 μM of Verapamil induces autophagy more significantly than Diltiazem and Nifedipine, respectively, in DOC-resistant (54.91±0.76, 18.03±0.69, 7.05±0.30) or VCR-resistant A549 (32.41±1.04, 21.51±0.63, 7.14±0.24) cells. Inhibition of apoptosis by pan-caspase inhibitor partly reduced cell death indicates association of caspase-dependent cell death but with persistence of autophagy. Inhibition of autophagy by interfering ATG5 expression reduced c-PARP level and apoptotic cells suggest a pro-death role of autophagy. Chloroquine treatment enhanced autophagosome accumulation and cell death but with reduced c-PARP level suggests that mechanism of caspase-independent cell death also contributes to Verapamil/chemotherapy-induced anticancer effects. 

Conclusion

Verapamil combined with DOC or VCR induces chemoresistant lung cancer cells to death through autophagy burst and apoptosis more strongly than Diltiazem and Nifedipine. Administering Verapamil or Diltiazem individually with chemotherapy, but not Nifedipine, can be considered in lung cancer patients with hypertension.

Ni-induced TGF-β signaling promotes VEGF-a secretion via integrin β3 upregulation

Nickel compounds are associated with lung and skin cancer incidence increase and accumulation of nickel in the body contributes to carcinogenesis. Upregulation of certain integrins in the primary tumor is associated with cancer metastasis and poor prognosis. However, the molecular mechanisms of nickel-induced cancer metastasis are still unclear. The purpose of the present study was to investigate the effects of nickel chloride (NiCl₂ ) on the progression of cancer during metastasis. The results of showed that NiCl₂ induces the expression of integrin β3 mRNA and protein in a dose- and time-dependent manner. Inhibition of integrin αvβ3 activation by ITGB3 ligand mimetics and GR144053, as well as downregulation of ITGB3 by lentiviral shRNA gene silencing, diminished NiCl₂ -induced secretion of vascular endothelial growth factor-a (VEGF-a). Furthermore, pretreatment with type I TGF-β receptor inhibitor, SB525334, suppressed the expression of ITGB3 at cell surface and secretion of VEGF-a in NiCl₂ -treated cells. In conclusion, NiCl₂ induces the expression of ITGB3 through TGF-β signaling activation, followed by increasing VEGF-a secretion, revealing a novel role for ITGB3 in nickel compound-induced cancer metastasis and tumor angiogenesis.

Tissue transglutaminase 2 expression is epigenetically regulated in human lung cancer cells and prevents reactive oxygen species-induced apoptosis

Purpose

Tissue transglutaminase 2 (TG2) is a stress-regulated protein and associated with cancer cell survival. However, the effects of TG2 expression in human non-small-cell lung cancer (NSCLC) cells on reactive oxygen species (ROS) production and redox homeostasis have not been fully elucidated.

Materials and methods

We investigated the TG2 expression and activity in A549, H1299, H1355, and H460 lung cancer cells by Western blots and quantitative polymerase chain reaction assay. The enzyme-linked immunosorbent assay was used for transglutaminase activity. The epigenetic expression was characterized with histone deacetylase inhibitor trichostatin A and DNA methyltransferase inhibitor 5-Aza treatment. TG2 expression was inhibited by siRNA transfection and the intracellular calcium was measured by Flow-3AM assay, apoptosis was analyzed by Annexin V/propidium iodide assay, and intracellular ROS was detected by fluorescence-activated cell sorting analysis. The ROS scavenger N-acetyl-L-cysteine (NAC) was applied to reduce TG2-knockdown-induced oxidative stress.

Results

Only A549 cells expressing high levels of TG2 correlated with high TG2 activity. The expression of TG2 can be regulated by epigenetic regulation in A549, H1299, and H1355 cells. The data also show that TG2 reduction induces apoptosis in A549 and H1299 cells. Furthermore, increased intracellular ROS and calcium levels were both detected in TG2-reduced cells. Moreover, endoplasmic reticulum stress inhibitor (salubrinal) and antioxidant NAC were able to reduce ROS and calcium levels to recover cell viability. Interestingly, the extrinsic and intrinsic apoptosis pathways were activated with a p53 independence upon TG2 reduction. TG2 reduction not only attenuated AKT activation but also reduced superoxide dismutase 2 (SOD2) expression. Exogenous NAC partially recovered SOD2 expression, indicating that mitochondrial-mediated apoptosis accounts for a part of but not all of the TG2-reduction-related death.

Conclusion

TG2 plays a protection role in NSCLC cell lines. Regardless of the endogenous level of TG2 and p53 status, reduction of TG2 may result in oxidative stress that induces apop-tosis. Therefore, target TG2 expression represents a logical strategy for NSCLC management.

High pemetrexed sensitivity of docetaxel-resistant A549 cells is mediated by TP53 status and downregulated thymidylate synthase

The chemoresistance of non-small cell lung cancer (NSCLC) that occurs in docetaxel (DOC) chemotherapy substantially decreases the survival of patients. To overcome DOC-induced chemoresistance, we established DOC-selected A549 lung cancer sublines (A549/D16 and A549/D32) and revealed that both sublines were cross-resistant to vincristine (VCR) and doxorubicin (DXR). Notably, both sublines were more sensitive to pemetrexed (PEM) than parental cells according to MTT and clonogenic assays. The expression levels of thymidylate synthase (TS) and γ-glutamyl hydrolase (GGH) were downregulated in DOC-resistant sublines. When exogenous TS was overexpressed in A549/D16 cells, PEM sensitivity was significantly decreased, however it was not decreased by overexpression of exogenous GGH. PEM treatment induced more apoptotic sub-G1 cells in both DOC-resistant sublines and in the in vivo PEM sensitivities of A549/D16 cells. These findings were further confirmed by a xenografted tumor model. To unmask the mediator of TS downregulation, we investigated human lung cancer cell lines that have various TP53 statuses using DOC treatment. The level of TS protein was significantly decreased in wild-type TP53-containing cells with DOC treatment; TS expression levels were not affected in mutant-TP53 and TP53-null cells under the same conditions. Furthermore, when the expression of TP53 was inhibited in A549 cells, the expression level of TS was increased. Our data indicated that DOC activated wild-type TP53 and suppressed TS expression under continuous DOC exposure. Therefore, the expression of TS remained at low levels in DOC-resistant A549 cancer cells. Our data revealed that for lung cancer with DOC resistance and wild-type TP53 status, the administration of PEM as a second-line agent to overcome DOC-resistance may benefit patients.

Immunomodulatory Protein from Ganoderma microsporum Induces Pro-Death Autophagy through Akt-mTOR-p70S6K Pathway Inhibition in Multidrug Resistant Lung Cancer Cells

Chemoresistance in cancer therapy is an unfavorable prognostic factor in non-small cell lung cancer (NSCLC). Elevation of intracellular calcium level in multidrug resistant (MDR) sublines leads to sensitization of MDR sublines to cell death. We demonstrated that a fungal protein from Ganoderma microsporum, GMI, elevates the intracellular calcium level and reduces the growth of MDR subline via autophagy and apoptosis, regardless of p-glycoprotein (P-gp) overexpression, in mice xenograft tumors. In addition, we examined the roles of autophagy in the death of MDR A549 lung cancer sublines by GMI, thapsigargin (TG) and tunicamycin (TM) in vitro. Cytotoxicity of TG was inhibited by overexpressed P-gp. However, TM-induced death of MDR sublines was independent of P-gp level. Combinations of TG and TM with either docetaxel or vincristine showed no additional cytotoxic effects on MDR sublines. TG- and TM-mediated apoptosis of MDR sublines was demonstrated on Annexin-V assay and Western blot and repressed by pan-caspase inhibitor (Z-VAD-FMK). Treatment of MDR sublines with TG and TM also augmented autophagy with accumulation of LC3-II proteins, breakdown of p62 and formation of acidic vesicular organelles (AVOs). Inhibition of ATG5 by shRNA silencing significantly reduced autophagy and cell death but not apoptosis following TG or TM treatment. GMI treatment inhibited the phosphorylation of Akt/S473 and p70S6K/T389. Interestingly, the phosphorylation of ERK was not associated with GMI-induced autophagy. We conclude that autophagy plays a pro-death role in acquired MDR and upregulation of autophagy by GMI via Akt/mTOR inhibition provides a potential strategy for overcoming MDR in the treatment of lung cancers.

Inhibition of lysosome degradation on autophagosome formation and responses to GMI, an immunomodulatory protein from Ganoderma microsporum

BACKGROUND AND PURPOSE

Autophagic cell death is considered a self-destructive process that results from large amounts of autophagic flux. In our previous study, GMI, a recombinant fungal immunomodulatory protein cloned from Ganoderma microsporum, induced autophagic cell death in lung cancer cells. The aim of this study was to examine the role of autophagosome accumulation in GMI-mediated cell death.

EXPERIMENTAL APPROACH

Western blot analysis, flow cytometry and confocal microscopy were used to evaluate the effects of different treatments, including silencing of ATP6V0A1 by use of short hairpin RNAi, on GMI-mediated cell death, lung cancer cell viability and autophagosome accumulation in vitro.

KEY RESULTS

Lysosome inhibitors bafilomycin-A1 and chloroquine increased GMI-mediated autophagic cell death. GMI and bafilomycin-A1 co-treatment induced the accumulation of large amounts of autophagosomes, but did not significantly induce apoptosis. GMI elicited autophagy through the PKB (Akt)/mammalian target of rapamycin signalling pathway. Silencing of ATP6V0A1, one subunit of vesicular H(+)-ATPases (V-ATPases) that mediates lysosome acidification, spontaneously induced autophagosome accumulation, but did not affect lysosome acidity. GMI-mediated autophagosome accumulation and cytotoxicity was increased in shATP6V0A1 lung cancer cells. Furthermore, ATP6V0A1 silencing decreased autophagosome and lysosome fusion in GMI-treated CaLu-1/GFP-LC3 lung cancer cells.

CONCLUSION AND IMPLICATIONS

We demonstrated that autophagosome accumulation induces autophagic cell death in a GMI treatment model, and ATP6V0A1 plays an important role in mediating autophagosome-lysosome fusion. Our findings provide new insights into the mechanisms involved in the induction of autophagic cell death.

GMI, an immunomodulatory protein from Ganoderma microsporum, induces autophagy in non-small cell lung cancer cells

Autophagy is a self-digestive process that degrades the cytoplasmic constituents. Immunomodulatory protein, one major bioactive component of Ganoderma, has antitumor activity. In this study, recombinant fungal immunomodulatory protein, GMI, was cloned from Ganoderma microsporum and purified. We demonstrated that GMI induces lung cancer cell death by activating autophagy, but does not induce apoptotic cell death. On western blot, GMI increased LC3 conversion and decreased p53 expression in a time- and concentration-dependent manner. Cytoplasmic calcium chelator BAPTA-AM was used to prove that GMI promotes autophagy via a calcium-mediated signaling pathway. 3-methyladenine (3-MA), an autophagy inhibitor, enhanced the cytotoxicity of GMI on cell viability assay. Using VZV-G pseudotyped lentivirus-shRNA system for autophagy-related genes silencing, the capabilities of GMI to reduce cell viability and colony formation were abolished in autophagy-defective cells. Furthermore, GMI did not stimulate apoptosis after blocking of autophagy by 3-MA or shRNA knockdown system. In xenograft studies, oral administration of GMI inhibited the tumor growth and induced autophagy significantly in nude mice that had received a subcutaneous injection of A549 cells. This is the first study to reveal the novel function of GMI in activating autophagy. GMI may be a potential chemopreventive agent against non-small cell lung cancer.

N-acetyl cysteine mitigates curcumin-mediated telomerase inhibition through rescuing of Sp1 reduction in A549 cells

Curcumin is a natural compound that has been extensively observed due to its potential as an anticancer drug. Curcumin restrains cancer cell progression via telomerase activity suppression. However, the exact mechanism is still unknown. In this study, we demonstrate that the effects of curcumin on cell viability and telomerase activity can be blunted by reactive oxygen species (ROS) inhibitor N-acetyl cysteine (NAC). The ROS induced by curcumin in A549 cells was detected by flow cytometry. Using Western blot and RT-PCR, human telomerase reverse transcriptase (hTERT) decreased in the presence of curcumin. Sp1 is one of the important transcription factors in hTERT expression. Our data showed that curcumin decreases the expression of Sp1 through proteasome pathway. In addition, NAC blunted the Sp1 reduction and hTERT downregulation by curcumin. Further, reporter assay and DNA affinity precipitation assay confirmed the influence of curcumin on Sp1 in hTERT regulation. This is the first study to demonstrate that curcumin induces ROS production resulting in Sp1 binding activity inhibition and hTERT downregulation.

Isolation of an insertion sequence from Ralstonia solanacearum race 1 and its potential use for strain characterization and detection

A new insertion sequence (IS), IS1405, was isolated and characterized from a Ralstonia solanacearum race 1 strain by the method of insertional inactivation of the sacB gene. Sequence analysis indicated that the IS is closely related to the members of IS5 family, but the extent of nucleotide sequence identity in 5' and 3' noncoding regions between IS1405 and other members of IS5 family is only 23 to 31%. Nucleotide sequences of these regions were used to design specific oligonucleotide primers for detection of race 1 strains by PCR. The PCR amplified a specific DNA fragment for all R. solanacearum race 1 strains tested, and no amplification was observed with some other plant-pathogenic bacteria. Analysis of nucleotide sequences flanking IS1405 and additional five endogenous IS1405s that reside in the chromosome of R. solanacearum race 1 strains indicated that IS1405 prefers a target site of CTAR and has two different insertional orientations with respect to this target site. Restriction fragment length polymorphism (RFLP) pattern analysis using IS1405 as a probe revealed extensive genetic variation among strains of R. solanacearum race 1 isolated from eight different host plants in Taiwan. The RFLP patterns were then used to subdivide the race 1 strains into two groups and several subgroups, which allowed for tracking different subgroup strains of R. solanacearum through a host plant community. Furthermore, specific insertion sites of IS1405 in certain subgroups were used as a genetic marker to develop subgroup-specific primers for detection of R. solanacearum, and thus, the subgroup strains can be easily identified through a rapid PCR assay rather than RFLP analysis.

Transcription factors in melanocyte development: distinct roles for Pax-3 and Mitf

A transgenic mouse model was used to examine the roles of the murine transcription factors Pax-3 and Mitf in melanocyte development. Transgenic mice expressing beta-galactosidase from the dopachrome tautomerase (Dct) promoter were generated and found to express the transgene in developing melanoblasts as early as embryonic day (E) 9.5. These mice express the transgene in a pattern characteristic of endogenous Dct expression. Transgenic mice were intercrossed with two murine coat color mutants, Splotch (Sp), containing a mutation in the murine Pax3 gene, and Mitf(mi), with a mutation in the basic-helix-loop-helix-leucine zipper gene Mitf. Transgenic heterozygous mutant animals were crossed to generate transgenic embryos for analysis. Examination of beta-galactosidase-expressing melanoblasts in mutant embryos reveals that Mitf is required in vivo for survival of melanoblasts up to the migration staging area in neural crest development. Examination of Mitf(mi)/+ embryos shows that there are diminished numbers of melanoblasts in the heterozygous state early in melanocyte development, consistent with a gene dosage-dependent effect upon cell survival. However, quantification and analysis of melanoblast growth during the migratory phase suggests that melanoblasts then increase in number more rapidly in the heterozygous embryo. In contrast to Mitf(mi)/Mitf(mi) embryos, Sp/Sp embryos exhibit melanoblasts that have migrated to characteristic locations along the melanoblast migratory pathway, but are greatly reduced in number compared to control littermates. Together, these results support a model for melanocyte development whereby Pax3 is required to expand a pool of committed melanoblasts or restricted progenitor cells early in development, whereas Mitf facilitates survival of the melanoblast in a gene dosage-dependent manner within and immediately after emigration from the dorsal neural tube, and may also directly or indirectly affect the rate at which melanoblast number increases during dorsolateral pathway migration.