Modulating sensitivity to drug-induced apoptosis: the future for chemotherapy?

CCT128930 induces G1-phase arrest and apoptosis and synergistically enhances the anticancer efficiency of VS5584 in human osteosarcoma cells

Osteosarcoma is a highly invasive primary malignant bone tumor. PI3K/mTOR pathway plays a key role in tumor progression, and inhibition of PI3K/mTOR pathway represents a novel strategy in therapy of osteosarcoma. CCT128930 and VS5584 are both inhibitors of PI3K/mTOR, but the anticancer mechanism of CCT128930 or/and VS5584 against human osteosarcoma cells remains unclear. Herein, U2OS and MG63 human osteosarcoma cells were cultured, and the anticancer effects of CCT128930 alone and the combined effect of CCT128930 and VS5584 against human osteosarcoma cells were explored. The results showed that CCT128930 as PI3K/mTOR inhibitor effectively inhibited p-p70 and p-AKT expression and dose-dependently inhibited U2OS cells and MG63 human osteosarcoma cells growth. Further studies found that CCT128930 triggered significant G-1 phase arrest and apoptosis, as convinced by the dysfunction of p27, Cyclin B1, Cyclin D1 and Cdc2, and PARP cleavage and caspase-3 activation. Moreover, CCT128930 treatment obviously enhanced VS5584-induced growth inhibition and apoptosis in human osteosarcoma cells, followed by enhanced PARP cleavage and caspase-3 activation. Taken together, CCT128930 alone or combined treatment with CCT128930 and VS5584 both effectively inhibited human osteosarcoma cells growth by induction of G1-phase arrest and apoptosis through regulating PI3K/mTOR and MAPKs pathways.

Systems analysis of phosphorylation-regulated Bcl-2 interactions establishes a model to reconcile the controversy over the significance of Bcl-2 phosphorylation

BACKGROUND AND PURPOSE

The biological significance of the multi-site phosphorylation of Bcl-2 at its loop region (T69, S70 and S87) has remained controversial for decades. This is a major obstacle for understanding apoptosis and anti-tumour drug development.

EXPERIMENTAL APPROACH

We established a mathematical model into which a phosphorylation and de-phosphorylation process of Bcl-2 was integrated. Paclitaxel-treated breast cancer cells were used as experimental models. Changes in the kinetics of binding with its critical partners, induced by phosphorylation of Bcl-2 were experimentally obtained by surface plasmon resonance, using a phosphorylation-mimicking mutant EEE-Bcl-2 (T69E, S70E and S87E).

KEY RESULTS

Mathematical simulations combined with experimental validation showed that phosphorylation regulates Bcl-2 with different dynamics depending on the extent of Bcl-2 phosphorylation and the phosphorylated Bcl-2-induced changes in binding kinetics. In response to Bcl-2 homology 3 (BH3)-only protein Bmf stress, Bcl-2 phosphorylation switched from diminishing to enhancing the Bcl-2 anti-apoptotic ability with increased phosphorylation of Bcl-2, and the turning point was 50% Bcl-2 phosphorylation induced by 0.2 μM paclitaxel treatment. In contrast, Bcl-2 phosphorylation enhanced the anti-apoptotic ability of Bcl-2 towards other BH3-only proteins Bim, Bad and Puma, throughout the entire phosphorylation procedure.

CONCLUSIONS AND IMPLICATIONS

The model could accurately predict the effects of anti-tumour drugs that involve the Bcl-2 family pathway, as shown with ABT-199 or etoposide.

The effect of tubeimoside-1 on the proliferation, metastasis and apoptosis of oral squamous cell carcinoma in vitro

Background

Tubeimoside-1 (TBMS1), a triterpenoid saponin extracted from traditional Chinese medicine tubeimoside, exerts a cytotoxic effect on several human cancer cell lines. However, no study has focused on whether TBMS1 works on oral squamous cell carcinoma (OSCC).

Materials and methods

We treated OSCC cells with TBMS1 to detect the effect and relevant molecular basis of TBMS1 for the first time. We chose two oral cancer cell lines, CAL27 and SCC15, for this study. First, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylte-trazolium bromide assay and cell proliferation 5′-bromo-2′-deoxyuridine assay were carried out to detect cell growth. Second, colony formation assay was performed to assess clonogenesis capacity. Next apoptosis was analyzed by flow cytometry. Subsequently, wound healing and transwell assays were applied to explore cell migration. Finally, Western blot was further performed to examine corresponding proteins’ expression change.

Results

Our data showed that TBMS1 significantly suppressed proliferation of OSCC cells in a dose- and time-dependent manner and it inhibited migration of OSCC cells as well. After treatment with TBMS1, OSCC cells underwent cell apoptosis. Furthermore, Western blot demonstrated that TBMS1 downregulated apoptosis-associated proteins such as PARP, p-ERK1/2, Bcl-2, caspase-3, caspase-7 and caspase-8 and upregulated cleaved PARP, cleaved caspase-3 and cleaved caspase-9. It could also reduce expression of c-Myc and MMP-7. Meanwhile, TBMS1 did not change the total ERK1/2 expression.

Conclusion

These results revealed that TBMS1 might be a potential chemotherapeutic drug for the management of OSCC.

Molecular chess? Hallmarks of anti-cancer drug resistance

Background

The development of resistance is a problem shared by both classical chemotherapy and targeted therapy. Patients may respond well at first, but relapse is inevitable for many cancer patients, despite many improvements in drugs and their use over the last 40 years.

Review

Resistance to anti-cancer drugs can be acquired by several mechanisms within neoplastic cells, defined as (1) alteration of drug targets, (2) expression of drug pumps, (3) expression of detoxification mechanisms, (4) reduced susceptibility to apoptosis, (5) increased ability to repair DNA damage, and (6) altered proliferation. It is clear, however, that changes in stroma and tumour microenvironment, and local immunity can also contribute to the development of resistance. Cancer cells can and do use several of these mechanisms at one time, and there is considerable heterogeneity between tumours, necessitating an individualised approach to cancer treatment. As tumours are heterogeneous, positive selection of a drug-resistant population could help drive resistance, although acquired resistance cannot simply be viewed as overgrowth of a resistant cancer cell population. The development of such resistance mechanisms can be predicted from pre-existing genomic and proteomic profiles, and there are increasingly sophisticated methods to measure and then tackle these mechanisms in patients.

Conclusion

The oncologist is now required to be at least one step ahead of the cancer, a process that can be likened to ‘molecular chess’. Thus, as well as an increasing role for predictive biomarkers to clinically stratify patients, it is becoming clear that personalised strategies are required to obtain best results.

Selenadiazole derivatives antagonize glucocorticoid-induced osteoblasts cells apoptosis by blocking ROS-mediated signaling, a new anti-osteoporosis strategy

Herein we demonstrate that synthetic selenadiazole derivatives could protect osteoblasts cells against Dex-induced cell apoptosisviaattenuating oxidative stress and downstream signalling pathways.

PU.1-Bim axis is involved in Trichostatin A-induced apoptosis in murine pro-B lymphoma FL5.12 cells

Trichostatin A (TSA) is a well-known histone deacetylases (HDACs) inhibitor that has been reported to show potent anti-tumor capabilities in some types of cancer cell lines. However, detailed mechanism of TSA action on lymphoma remains to be described. In the present study, anti-proliferative effects of TSA were investigated using a murine pro-B lymphoma cell line FL5.12. MTT assay revealed that TSA potently inhibited the proliferation of FL5.12 cells in a time- and dose-dependent manner. Bright-field microscopy of FL5.12 cells showed apoptotic morphology at 24 h after TSA treatment. Consistently, TSA treatment led to DNA fragmentation and increased the protein levels of cleaved caspase 3 and PARP as revealed by western blot analysis. To explore the underlying mechanism of TSA-induced apoptosis of FL5.12 cells, we further analyzed the hematopoietic transcription factor Purine Rich Box-1 (PU.1) by western blot analysis. TSA treatment resulted in the inhibition of PU.1 in FL5.12 cells. In contrast, apoptotic protein Bim was induced by TSA, which was inversely correlated with the survival of FL5.12 cells. These results suggest the possible mechanism of TSA-induced apoptosis in murine pro-B lymphoma FL5.12 cells via the PU.1-Bim axis.

Ovariectomy is associated with metabolic impairments and enhanced mammary tumor growth in MKR mice

Obesity and type 2 diabetes (T2D) are associated with an increased risk of breast cancer incidence and mortality. Common features of obesity and T2D are insulin resistance and hyperinsulinemia. A mammary tumor promoting effect of insulin resistance and hyperinsulinemia was demonstrated in the transgenic female MKR mouse model of pre-diabetes inoculated with mammary cancer cells. Interestingly, in MKR mice, as well as in other diabetic mouse models, males exhibit severe hyperglycemia, while females display insulin resistance and hyperinsulinemia with only a mild increase in blood glucose levels. This gender-specific protection from hyperglycemia may be attributed to estradiol, a key player in the regulation of the metabolic state, including obesity, glucose homeostasis, insulin resistance, and lipid profile. The aim of this study was to investigate the effects of ovariectomy (including the removal of endogenous estradiol) on the metabolic state of MKR female mice and subsequently on the growth of Mvt-1 mammary cancer cells, inoculated into the mammary fat pad of ovariectomized mice, compared with sham-operated mice. The results showed an increase in body weight, accompanied by increased fat mass, elevated blood glucose levels, and hypercholesterolemia, in ovariectomized MKR mice. In addition, mammary tumor growth was significantly higher in these mice. The results suggest that ovarian hormone deficiency may promote impaired metabolic homeostasis in the hyperinsulinemic MKR female mice, which in turn is associated with an increased growth of mammary tumors.

Synergistic effect of combinatorial treatment with curcumin and mitomycin C on the induction of apoptosis of breast cancer cells: a cDNA microarray analysis

In order to explore the synergistic mechanisms of combinatorial treatment using curcumin and mitomycin C (MMC) for breast cancer, MCF-7 breast cancer xenografts were conducted to observe the synergistic effect of combinatorial treatment using curcumin and MMC at various dosages. The synergistic mechanisms of combinatorial treatment using curcumin and MMC on the inhibition of tumor growth were explored by differential gene expression profile, gene ontology (GO), ingenuity pathway analysis (IPA) and Signal-Net network analysis. The expression levels of selected genes identified by cDNA microarray expression profiling were validated by quantitative RT-PCR (qRT-PCR) and Western blot analysis. Effect of combinatorial treatment on the inhibition of cell growth was observed by MTT assay. Apoptosis was detected by flow cytometric analysis and Hoechst 33258 staining. The combinatorial treatment of 100 mg/kg curcumin and 1.5 mg/kg MMC revealed synergistic inhibition on tumor growth. Among 1501 differentially expressed genes, the expression of 25 genes exhibited an obvious change and a significant difference in 27 signal pathways was observed (p<0.05). In addition, Mapk1 (ERK) and Mapk14 (MAPK p38) had more cross-interactions with other genes and revealed an increase in expression by 8.14- and 11.84-fold, respectively during the combinatorial treatment by curcumin and MMC when compared with the control. Moreover, curcumin can synergistically improve tumoricidal effect of MMC in another human breast cancer MDA-MB-231 cells. Apoptosis was significantly induced by the combinatorial treatment (p<0.05) and significantly inhibited by ERK inhibitor (PD98059) in MCF-7 cells (p<0.05). The synergistic effect of combinatorial treatment by curcumin and MMC on the induction of apoptosis in breast cancer cells may be via the ERK pathway.

A new 2α,5α,10β,14β-tetraacetoxy-4(20),11-taxadiene (SIA) derivative overcomes paclitaxel resistance by inhibiting MAPK signaling and increasing paclitaxel accumulation in breast cancer cells

Tumor resistance due to multiple mechanisms seriously hinders the efficacy of chemotherapy drugs such as paclitaxel. The most widely studied P-glycoprotein inhibitors still have limited ability to reverse resistance in the clinic. In this study, NPB304, a novel Sinenxan A (SIA) derivative, was found to significantly sensitize resistant breast cancer cells to paclitaxel in vitro and in vivo. Treatment with NPB304 increased paclitaxel-induced apoptosis in a p53-dependent manner through PARP cleavage. Importantly, NPB304 enhanced the antitumor effect of paclitaxel in resistant breast tumor xenografts in nude mice without significantly affecting weight loss. NPB304 regulated cell resistance through inhibition of MAPK pathway components, including p-ERK and p-p38. Moreover, NPB304 increased paclitaxel accumulation by affecting P-gp function. In addition to increasing Rhodamine 123 accumulation, NPB304 promoted bidirectional permeability but decreased the efflux ratio of paclitaxel in a Caco-2 monolayer model, thereby increasing the intracellular concentration of paclitaxel. Similarly, NPB304 increased the concentration of paclitaxel in the resistant tumor tissue. Hence, NPB304 is a novel compound that promotes the sensitization of resistant cells to paclitaxel through multiple mechanisms and has the potential for use in combination therapies to treat resistant breast cancer.

HS-1793, a resveratrol analogue, induces cell cycle arrest and apoptotic cell death in human breast cancer cells

Resveratrol, a polyphenolic compound, is a naturally occurring phytochemical and is found in a variety of plants, including food such as grapes, berries and peanuts. It has gained much attention for its potential anticancer activity against various types of human cancer. However, the usefulness of resveratrol as a chemotherapeutic agent is limited by its photosensitivity and metabolic instability. In this study the effects of a synthetic analogue of resveratrol, HS-1793, on the proliferation and apoptotic cell death were investigated using MCF-7 (wild-type p53) and MDA-MB-231 (mutant p53) human breast cancer cells. HS-1793 inhibited cell growth and induced apoptotic cell death in a concentration-dependent manner. The induction of apoptosis was determined by morphological changes, cleavage of poly(ADP-ribose) poly-merase, alteration of Bax/Bcl-2 expression ratio and caspase activities. Flow cytometric analysis revealed that HS-1793 induced G2/M arrest in the cell cycle progression in both types of cells. Of note, HS-1793 induced p53/p21WAF1/CIP1-dependent apoptosis in MCF-7 cells, whereas it exhibited p53-independent apoptosis in MDA-MB-231 cells. Furthermore, HS-1793 showed more potent anticancer effects in several aspects compared to resveratrol in MCF-7 and MDA-MB-231 cells. Thus, these findings suggest that HS-1793 has potential as a candidate chemotherapeutic agent against human breast cancer.

Pemetrexed downregulates ERCC1 expression and enhances cytotoxicity effected by resveratrol in human nonsmall cell lung cancer cells

The multitargeted antifolate pemetrexed has demonstrated certain clinical activities against nonsmall cell lung cancer (NSCLC). Resveratrol (3,5,4-trihydroxy-trans-stilbene) is a polyphenol found in grapes and other plants and has great potential as a preventative and therapeutic agent due to its anticarcinogenic activity. The efficacy of adding resveratrol to pemetrexed to prolong the survival of patients with NSCLC still remains unclear. The excision repair cross-complementation 1 (ERCC1) is a DNA repair gene coding 5' endonuclease in nucleotide excision repair and is overexpressed in chemo- or radioresistant carcinomas. In this study, resveratrol (10-50 μM) inhibited cell survival in two NSCLC cells, H520 and H1975. Treatment with resveratrol increased ERCC1 messenger RNA and protein levels in a MKK3/6-p38 MAPK signal activation-dependent manner. Furthermore, blocking p38 MAPK activation by SB202190 or knocking down ERCC1 expression by transfection with small interfering RNA of ERCC1 enhanced the cytotoxicity of resveratrol. Combining resveratrol with pemetrexed resulted in a synergistic cytotoxic effect, accompanied with the reduction of phospho-p38 MAPK and ERCC1 protein levels, and a DNA repair capacity. Expression of constitutively active MKK6 (MKK6E) or HA-p38 MAPK vectors significantly rescued the decreased p38 MAPK activity, and restored ERCC1 protein levels and cell survival in resveratrol and pemetrexed cotreated NSCLC cells. In this study, for the first time, we have demonstrated the synergistic effect of combined treatment with resveratrol and pemetrexed in human NSCLC cells through downregulation of the MKK3/6-p38 MAPK-ERCC1 signal, suggesting a potential benefit of combining resveratrol and pemetrexed to treat lung cancer in the future.

Natural borneol, a monoterpenoid compound, potentiates selenocystine-induced apoptosis in human hepatocellular carcinoma cells by enhancement of cellular uptake and activation of ROS-mediated DNA damage

Selenocystine (SeC) has been identified as a novel compound with broad-spectrum anticancer activities. Natural borneol (NB) is a monoterpenoid compound that has been used as a promoter of drug absorption. In the present study, we demonstrated that NB significantly enhanced the cellular uptake of SeC and potentiated its antiproliferative activity on HepG2 cells by induction of apoptosis. NB effectively synergized with SeC to reduce cancer cell growth through the triggering apoptotic cell death. Further mechanistic studies by Western blotting showed that treatment of the cells with NB and SeC activated the intrinsic apoptotic pathway by regulation of pro-survival and pro-apoptotic Bcl-2 family proteins. Treatment of the cells with NB and SeC induced the activation of p38MAPK and inactivation of Akt and ERK. NB also potentiated SeC to trigger intracellular ROS generation and DNA strand breaks as examined by Comet assay. Moreover, the thiol-reducing antioxidants effectively blocked the occurrence of cell apoptosis, which confirmed the important role of ROS in cell apoptosis. Taken together, these results reveal that NB strongly potentiates SeC-induced apoptosis in cancer cells by enhancement of cellular uptake and activation of ROS-mediated DNA damage. NB could be further developed as a chemosensitizer of SeC in treatment of human cancers.

Induction of apoptotic cell death by ursolic acid through mitochondrial death pathway and extrinsic death receptor pathway in MDA-MB-231 cells

Ursolic acid (3-hydroxy-urs-12-en-28-oic acid) is a pentacyclic triterpenoid derived from leaves, berries, fruits, and flowers of medicinal plants, such as Rosemarinus officinalis. Ursolic acid has been shown to inhibit tumorigenesis, tumor promotion, and suppress angiogenesis. In our present study, we found that ursolic acid decreased cell proliferation rate and induce apoptosis in human breast cancer cell line, MDA-MB-231. When we checked the expression levels of proteins associated with apoptosis signal by using immunoblotting, we found that ursolic acid induces various apoptotic molecules related to either extrinsic or intrinsic apoptosis signal pathway in MDA-MB-231 cells. In our study, we found that ursolic acid induced the appearance of Fas receptor and cleavage of caspase-8, -3 and PARP. We also found that ursolic acid induced Bax up-regulation and Bcl-2 down-regulation and release of cytochrome C to the cytosol from mitochondria. Moreover, ursolic acid cleaved caspase-9 and decreased mitochondrial membrane potential (ΔΨm) as shown with JC-1 staining. These data indicate that ursolic acid induce apoptosis through both mitochondrial death pathway and extrinsic death receptor dependent pathway in MDA-MB-231 cells. Our data clearly indicate that ursolic acid could be used as a potential anticancer drug for breast cancer.

Tissue inhibitor of metalloproteinase-1 decreased chemosensitivity of MDA-435 breast cancer cells to chemotherapeutic drugs through the PI3K/AKT/NF-кB pathway

TIMP-1 is well known to be capable of inhibiting apoptosis. Elevated levels of TIMP-1 in tumor tissue have been shown to be strongly associated with a poor response to chemotherapy. In this study, using conventional cytotoxic drugs commonly used in the treatment of breast cancer, we investigated how TIMP-1 influenced the efficacy using breast cell lines. Our data demonstrated that overexpression of TIMP-1 could significantly decrease the sensitivity of MDA-435 breast cancer cells to epirubicin and paclitaxel. TIMP-1 can potently activate phosphatidylinositol 3-kinase (PI3K)/Akt and nuclear factor-kappaB (NF-кB) signaling. Furthermore, the TIMP-1-induced attenuation of the effect of epirubicin and paclitaxel was reversed by the PI3K/Akt chemical inhibitor LY294002 and the NF-кB inhibitor pyrrolidine dithiocarbamate (PDTC), showing that the PI3K/Akt and NF-кB signaling pathway was involved in the TIMP-1-induced effect on chemoresistance. Taken together, our results indicate that TIMP-1 decreased chemosensitivity through the PI3K/Akt/NF-кB signal transduction pathway in MDA-435 breast cancer cells.

Myosin light chain kinase is responsible for high proliferative ability of breast cancer cells via anti-apoptosis involving p38 pathway

AIM

To investigate whether myosin light chain kinase (MLCK) contributed to the high proliferative ability of breast cancer cells.

METHODS

Soft agar colony formation on the MCF-7 and LM-MCF-7 cell lines was determined. The cell cycles of MCF-7 and LM-MCF-7 were detected using flow cytometry analysis. Western blot analysis was performed to detect the expression levels of p-ERK1/2, total-ERK1/2, p-p38, total p38, p-JNK, total-JNK, survivin, Bcl-2, p-MLC, caspase-9, cleaved caspase-9, and MLCK. After treatment with adriamycin (ADR), ML-7 and SB203580, apoptosis was examined using flow cytometry analysis and Annexin V-FITC fluorescence microscopy.

RESULTS

The breast cancer LM-MCF-7 cell line with high metastasis potential (a metastitic sub-clone of MCF-7) had higher anti-apoptosis ability relative to MCF-7 cells in response to adriamycin treatment (apoptosis rate: 6.76% vs 28.58%, P<0.05). Moreover, the expression level of MLCK was upregulated and the level of phosphorylated p38 (p-p38) was decreased in LM-MCF-7 cells. Flow cytometry analysis showed that ML-7, selective inhibitor of MLCK, could induce apoptosis of the LM-MCF-7 cells, in which the level of p-p38 was increased. Meanwhile, the expression levels of Bcl-2 and survivin were downregulated, while the caspase-9 was upregulated suggesting that the cells were undergone apoptosis. Flow cytometry analysis showed that SB203580, an inhibitor of p38, abolished ML-7-induced apoptosis, which resulted in the upregulation of Bcl-2 and survivin, and downregulation of caspase-9, suggesting that Bcl-2, survivin and caspase-9 are downstream effectors of p38.

CONCLUSION

MLCK is responsible for high proliferative ability of breast cancer cells through anti-apoptosis, in which p38 pathway was involved.

The combination of baicalin and baicalein enhances apoptosis via the ERK/p38 MAPK pathway in human breast cancer cells

AIM

To examine whether the cell growth inhibitory effect of the combination of baicalin and baicalein is related to apoptosis. Moreover, to determine whether the expression of some apoptosis-related proteins is regulated by the ERK/p38 MAPK pathway.

METHODS

Cell viability was measured using a 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was detected by acridine orange (AO) staining, DNA ladder assay and flow cytometric analysis. Apoptosis-related proteins were observed using Western blot analysis.

RESULTS

Compared with baicalin or baicalein alone, the combination treatment of baicalin (50 micromol/L) and baicalein (25 micromol/L) had an anti-proliferative effect in a time-dependent manner. Isobologram analysis demonstrated that the combination treatment had a synergistic effect. Moreover, apoptosis in MCF-7 cells was increased by 12% and 20% with the combination treatment at 24 h and 48 h, respectively. With the combination treatment in MCF-7 cells, cleaved caspase-3 and caspase-9 were observed, and the level of bcl-2 expression was decreased approximately 20% and 40% at 24 h and 48 h, respectively. The expression of bax and p53 were increased about 25% and 15% at 48 h, respectively. Moreover, the activation of caspase-3, -9 and the regulation of bcl-2, bax and p53 were related to ERK /p38 MAPK activation.

CONCLUSION

In this study, apoptosis was enhanced by the combination treatment of baicalin and baicalein, which activated caspases-3 and caspase-9, downregulated the level of bcl-2 and upregulated the level of bax or p53 via the ERK/p38 MAPK pathway.

Curcumin reduced the side effects of mitomycin C by inhibiting GRP58-mediated DNA cross-linking in MCF-7 breast cancer xenografts

Mitomycin C (MMC), a chemotherapeutic agent in breast cancer treatments, inhibits tumor growth through DNA cross-linking and breaking, but it has severe side effects. Here we examined whether and how curcumin reduced the side effects of MMC. We found that combination treatment with MMC and curcumin reduced tumor weight by 70% and 36% compared with saline and curcumin-treated groups, respectively. The combination treatment reduced weight loss and improved kidney function and bone marrow suppression compared with MMC treatment alone. Moreover, the combination treatment inhibited glucose regulatory protein (GRP58)-mediated DNA cross-linking. The combination treatment inhibited GRP58 through the ERK/p38 MAPK pathway. In conclusion, the current study provided evidence that MMC and curcumin combination treatment reduced MMC side effects by inhibiting GRP58-mediated DNA cross-linking through the ERK/p38 MAPK pathway.

VEGF and Bcl-2 interact via MAPKs signaling pathway in the response to hypoxia in neuroblastoma

Tumor hypoxia has been reported to be a negative prognostic factor in a number of tumor sites, which suggests a positive correlation between tumor hypoxia and increased metastatic efficiency. Evidence shows that vascular endothelial growth factor (VEGF) stimulates angiogenesis in tumor growth and mediates neuroprotection to prevent an apoptotic cell death. Human neuroblastoma cells (CHP126) were exposed to moderate hypoxia for different time spans to explore the molecular stress responses. Apoptotic features as an increase of Bax/Bcl-2 ratio and activation of caspase 3 were observed at early period of exposure time, but these effects were reversed with the extension of hypoxic treatment. Hypoxia also activated MAPKs signaling pathways in a time-relative manner, which were involved in the regulation of hypoxia-related resistance of CHP126 cells. Meanwhile, VEGF and its receptor KDR were found to interact with MAPKs signaling pathways except the effect of hypoxia. Furthermore, rhVEGF(165) was utilized to discern that VEGF increased Bcl-2 and procaspase 3 expressions, contributing to a synergistic relationship of an angiogenic response with Bcl-2 in hypoxia via a cross talk, while the activation of ERK MAPK is important for both productions. These altered signals may be critical to predict a poor outcome; therefore, our knowledge provides new insight into apoptosis and angiogenesis control of tumor cells and suggests a strategy based on the blockade of hypoxia-induced VEGF signaling under hypoxia in neuroblastoma.

Alteration of the mitochondrial apoptotic pathway is key to acquired paclitaxel resistance and can be reversed by ABT-737

Paclitaxel is a microtubule-targeting antineoplastic drug widely used in human cancers. Even when tumors are initially responsive, progression of disease despite continued taxane therapy is all too common in the treatment of many of the most common epithelial cancers, including breast cancer. However, the mechanisms underlying paclitaxel resistance in cancer cells are not completely understood. Our hypothesis is that changes in the intrinsic (or mitochondrial) cell death pathway controlled by the BCL-2 family are key to the development of acquired paclitaxel resistance. Here we show that paclitaxel activates the mitochondrial apoptosis pathway, which can be blocked by BCL-2 overexpression. Treatment with ABT-737, a small-molecule BCL-2 antagonist, restores sensitivity to paclitaxel in BCL-2-overexpressing cells. To investigate the importance of changes in the intrinsic apoptotic pathway in the absence of enforced BCL-2 expression, we generated two independent breast cancer cell lines with acquired resistance to apoptosis induced by paclitaxel. In these lines, acquired resistance to paclitaxel is mediated either by increased antiapoptotic BCL-2 proteins or decreased proapoptotic BCL-2 proteins. In both cases, ABT-737 can engage the mitochondrial apoptosis pathway to restore sensitivity to paclitaxel to cell lines with acquired paclitaxel resistance. In summary, these findings suggest that alterations in the intrinsic apoptotic pathway controlled by BCL-2 protein family members may be crucial to causing paclitaxel resistance. Furthermore, our results suggest that combining small-molecule BCL-2 antagonists with paclitaxel may offer benefit to patients with paclitaxel-resistant tumors, an oncologic problem of great prevalence.

Molecular basis for the induction of an angiogenesis inhibitor, thrombospondin-1, by 5-fluorouracil

5-Fluorouracil (5-FU) is one of the most commonly used anticancer drugs in chemotherapy against various solid tumors. 5-FU dose-dependently increased the expression levels of intrinsic antiangiogenic factor thrombospondin-1 (TSP-1) in human colon carcinoma KM12C cells and human breast cancer MCF7 cells. We investigated the molecular basis for the induction of TSP-1 by 5-FU in KM12C cells. Promoter assays showed that the region with the Egr-1 binding site is critical for the induction of TSP-1 promoter activity by 5-FU. The binding of Egr-1 to the TSP-1 promoter was increased in KM12C cells treated with 5-FU. Immunofluorescence staining revealed that 5-FU significantly increased the level of Egr-1 in the nuclei of KM12C cells. The suppression of Egr-1 expression by small interfering RNA decreased the expression level of TSP-1. Furthermore, 5-FU induced the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and heat shock protein 27 (HSP27). Blockade of the p38 MAPK pathway by SB203580 remarkably inhibited the phosphorylation of HSP27 induced by 5-FU and decreased the induction of Egr-1 and TSP-1 by 5-FU in KM12C cells. These findings suggest that the p38 MAPK pathway plays a crucial role in the induction of Egr-1 by 5-FU and that induced Egr-1 augments TSP-1 promoter activity, with the subsequent production of TSP-1 mRNA and protein.

[Pt(O,O'-acac)(gamma-acac)(DMS)], a new Pt compound exerting fast cytotoxicity in MCF-7 breast cancer cells via the mitochondrial apoptotic pathway

BACKGROUND AND PURPOSE

We showed previously that a new Pt complex containing an O,O'-chelated acetylacetonate ligand (acac) and a dimethylsulphide in the Pt coordination sphere, [Pt(O,O'-acac)(gamma-acac)(DMS)], induces apoptosis in HeLa cells. The objective of this study was to investigate the hypothesis that [Pt(O,O'-acac)(gamma-acac)(DMS)] is also cytotoxic in a MCF-7 breast cancer cell line relatively insensitive to cisplatin, and to gain a more detailed analysis of the cell death pathways.

EXPERIMENTAL APPROACH

Cells were treated with Pt compounds and cytotoxicity tests were performed, together with Western blotting of various proteins involved in apoptosis. The mitochondrial membrane potential was assessed by fluorescence microscopy and spectrofluorometry and the Pt bound to cell fractions was measured by atomic absorption spectrometry.

KEY RESULTS

In contrast to cisplatin, the cytotoxicity of [Pt(O,O'-acac)(gamma-acac)(DMS)] correlated with cellular accumulation but not with DNA binding. Also, the Pt content in DNA bases was considerably higher for cisplatin than for [Pt(O,O'-acac)(gamma-acac)(DMS)], thus excluding DNA as a target of [Pt(O,O'-acac)(gamma-acac)(DMS)]. [Pt(O,O'-acac)(gamma-acac)(DMS)] exerted high and fast apoptotic processes in MCF-7 cells since it provoked: (a) mitochondria depolarization; (b) cytochrome c accumulation in the cytosol; (c) translocation of Bax and truncated-Bid from cytosol to mitochondria and decreased expression of Bcl-2; (d) cleavage of caspases -7 and -9, and PARP degradation; (e) chromatin condensation and DNA fragmentation.

CONCLUSIONS AND IMPLICATIONS

[Pt(O,O'-acac)(gamma-acac)(DMS)] is highly cytotoxic for MCF-7 cells, cells relatively resistant to many chemotherapeutic agents, as it activates the mitochondrial apoptotic pathway. Hence, [Pt(O,O'-acac)(gamma-acac)(DMS)] has the potential to provide us with new opportunities for therapeutic intervention.

Jaceosidin induces apoptosis in ras-transformed human breast epithelial cells through generation of reactive oxygen species

Extracts of Artemisia plants possess anti-inflammatory and antioxidative activities. Eupatilin (5,7-dihydroxy-3',4',6-tri-methoxy-flavone), a pharmacologically active flavone derived from Artemisia asiatica, was shown to inhibit phorbol ester-induced cyclooxygenase-2 expression and NF-kappaB activation in mouse skin, and also to induce cell cycle arrest in ras-transformed human mammary epithelial (MCF10A-ras) cells. In this article, we examined the ability of jaceosidin (4',5,7-trihydroxy-3',6-dimethoxyflavone) isolated from Artemisia argyi to inhibit the proliferation of MCF10A-ras cells. Jaceosidin reduced the viability of MCF10A-ras cells to a greater extent than eupatilin. Jaceosidin treatment resulted in increased intracellular accumulation of reactive oxygen species (ROS) in MCF10A-ras cells, which was blocked by the antioxidant N-acetylcysteine (NAC). NAC attenuated jaceosidin-induced cytotoxicity. To better assess the proapoptotic effects of jaceosidin, we analyzed the treated cells by the flow cytometry. MCF10A-ras cells treated with jaceosidin (100 microM) exhibited the increased proportion of hypodiploid or apoptotic cells (48.72% as composed to 7.78% in control cells). Jaceosidin treatment also increased the ratio of proapoptotic Bax to the antiapoptotic Bcl-2 and induced the cleavage of caspase-3 and poly(ADP-ribose)polymerase (PARP). Moreover, jaceosidin elevated the expression of p53 and p21, while the compound inhibited the activation of ERK1/2 that is an important component of cell survival signaling.

Pretreatment with insulin enhances anticancer functions of 5-fluorouracil in human esophageal and colonic cancer cells

AIM

To investigate the effects of insulin on enhancing 5-fluorouracil (5-FU) anticancer functions and its mechanisms in the human esophageal cancer cell line (Eca 109) and human colonic cancer cell line (Ls-174-t).

METHODS

The effect of insulin/5-FU combination treatment on the growth of Eca 109 and Ls-174-t cells was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. After insulin treatment or insulin/5-FU treatment, cell cycle distribution of both cell lines was analyzed by flow cytometry. Western blot assay was used to assess the expression of caspase-3 and thymidylate synthase (TS). Apoptosis was detected by flow cytometry, DNA fragmentation assay, and terminal transferase dUTP nick end labeling assay (TUNEL). Moreover, the changes of 5-FU uptake after insulin pretreatment were detected by HPLC assay and Western blot analysis.

RESULTS

We found that insulin enhanced the inhibitory effect of 5- FU on cell proliferation when Eca 109 cells and Ls-174-t cells were pretreated with insulin for the appropriate time. Insulin increased the cell number of the S phase and the uptake of 5-FU. Insulin/5-FU treatment enhanced apoptosis of tumor cells and upregulated the expression of cleaved caspase-3 compared with 5-FU treatment. Moreover, insulin/5-FU treatment induced the changes of free TS and the TS ternary complex level compared with 5-FU treatment in Eca 109 and Ls-174-t cells.

CONCLUSION

These data suggest that insulin enhances anticancer functions of 5- FU when it is treated before 5-FU for the appropriate time in human esophageal and colonic cancer cell lines.

A pharmacoproteomics study of the cancer cell line EKVX using capillary-LC/MS/MS

The chemotherapeutic agent camptothecin, 10-OH (CPT,10-OH), was shown to act synergistically with the epithelial growth factor receptor (EGFR) inhibitor (AG1478) against several transformed cell lines. To study the cellular response to these drugs, the non-small-cell lung carcinoma cell line, EKVX, was treated with these compounds either alone or in combination. We performed a proteomic analysis using capillary-HPLC coupled with electrospray ion trap mass spectrometry (capillary-LC-ESI/MS) of a tryptic digest to obtain a global protein profile of the EKVX cell line and identify changes in protein expression. The combination of AG1478 and CPT,10-OH showed synergistic cytotoxicity and also changed the expression of multiple proteins, while individual treatments showed a lesser effect on protein expression. Thus, the synergistic action of AG1478 and CPT,10-OH was reflected in altered protein profiles, showing that a proteomic analysis can serve to evaluate chemotherapeutic agents and their combinations.

p38 MAPK turns hepatocyte growth factor to a death signal that commits ovarian cancer cells to chemotherapy-induced apoptosis

We recently showed that Hepatocyte Growth Factor (HGF), known as a survival factor, unexpectedly enhances apoptosis in human ovarian cancer cells treated with the front-line chemotherapeutics cisplatin (CDDP) and paclitaxel (PTX). Here we demonstrate that this effect depends on the p38 mitogen-activated kinase (MAPK). In fact, p38 MAPK activity is stimulated by HGF and further increased by the combined treatment with HGF and either CDDP or PTX. The expression of a dominant negative form of p38 MAPK abrogates apoptosis elicited by drugs, alone or in combination with HGF. HGF and drugs also activate the ERK1/2 MAPKs, the PI3K/AKT and the AKT substrate mTOR. However, activation of these survival pathways does not hinder the ability of HGF to enhance drug-dependent apoptosis. Altogether data show that p38 MAPK is necessary for HGF sensitization of ovarian cancer cells to low-doses of CDDP and PTX and might be sufficient to overcome activation of survival pathways. Therefore, the p38 MAPK pathway might be a suitable target to improve response to conventional chemotherapy in human ovarian cancer.

Microtubule stabilizing agents: Their molecular signaling consequences and the potential for enhancement by drug combination

Microtubule stabilization by chemotherapy is a powerful weapon in the war against cancer. Disruption of the mitotic spindle activates a number of signaling pathways, with consequences that may protect the cell or lead to its death via apoptosis. Taxol, the first microtubule stabilizing drug to be identified, has been utilized successfully in the treatment of solid tumors for two decades. Several features, however, make this drug less than ideal, and the search for next generation stabilizing drugs with increased efficacy has been intense and fruitful. Microtubule stabilizing agents (MSAs), including the taxanes, the epothilones, discodermolide, laulimalide, and eleutherobin, form an important and expanding family of chemotherapeutic agents. A strong understanding of their molecular signaling consequences is essential to their value, particularly in regard to their potential for combinatorial chemotherapy - the use of multiple agents to enhance the efficacy of cancer treatment. Here we present a critical review of research on the signaling mechanisms induced by MSAs, their relevance to apoptosis, and their potential for exploitation by combinatorial therapy.

Inhibition of extracellular signal regulated kinase (ERK) leads to apoptosis inducing factor (AIF) mediated apoptosis in epithelial breast cancer cells: the lack of effect of ERK in p53 mediated copper induced apoptosis

Recent studies have shown that MEK/ERK-mediated signals play a major role in regulation of activity of p53 tumor suppressor protein. In this study, we investigated whether or not there is functional interaction between p53 and MEK/ERK pathways in epithelial breast cancer cells exposed to copper or zinc. We demonstrated that expression of wild-type p53 induced by copper or zinc significantly reduced phosphorylation of extracellular signal regulated kinase (ERK) in epithelial breast cancer MCF7 cells. Mutation or suppression of p53 in MDA-MB231 and MCF7-E6 cells, respectively, resulted in a strong ERK phosphorylation in the presence of metals. Weak ERK phosphorylation in MCF7 cells induced by copper or zinc was linked to mitochondrial disruption and apoptosis. Furthermore, inhibition of ERK through addition of PD98059 stimulated p53 activation in MCF7 cells and also led to upregulation of p53 downstream targets, p21 and Bax, which is a proapototic member of Bcl-2 family triggering mitochondrial pore opening. Moreover, blockage of the MEK/ERK pathway caused a breakdown of the mitochondrial membrane potential accompanied by an elevation in the ROS production. Disruption of p53 expression attenuated the depolarization of the mitochondrial membrane and ROS generation. Furthermore, PD98059 initiated apoptosis inducing factor (AIF) translocation from mitochondria to the nucleus in MCF7 cells; which are depleted in caspase 3. Interestingly, repression of MEK/ERK pathway did not intensify the cell stress caused by metal toxicity. Therefore, these findings demonstrate that MEK/ERK pathway plays an important role in downregulation of p53 and cell survival. Inhibition of ERK can lead to apoptosis via nuclear relocation of AIF. However, metal-induced activation of p53 and mitochondrial depolarization appears to be independent of ERK. Our data suggest that copper induces apoptosis through depolarization of mitochondrial membrane with release of AIF, and this process is MEK/ERK independent.

The role of pH dynamics and the Na+/H+ antiporter in the etiopathogenesis and treatment of cancer. Two faces of the same coin--one single nature

Looked at from the genetic point-of-view cancer represents a daunting and, frankly, confusing multiplicity of diseases (at least 100) that require an equally large variety of therapeutic strategies and substances designed to treat the particular tumor. However, when analyzed phenotypically cancer is a relatively uniform disease of very conserved 'hallmark' behaviors across the entire spectrum of tissue and genetic differences [D. Hanahan, R.A. Weinberg, Hallmarks of cancer, Cell 100 (2000) 57-70]. This suggests that cancers do, indeed, share common biochemical and physiological characteristics that are independent of the varied genetic backgrounds, and that there may be a common mechanism underlying both the neoplastic transformation/progression side and the antineoplastic/therapy side of oncology. The challenge of modern oncology is to integrate all the diverse experimental data to create a physiological/metabolic/energetic paradigm that can unite our thinking in order to understand how both neoplastic progression and therapies function. This reductionist view gives the hope that, as in chemistry and physics, it will possible to identify common underlying driving forces that define a tumor and will permit, for the first time, the actual calculated manipulation of their state. That is, a rational therapeutic design. In the present review, we present evidence, obtained from a great number of studies, for a fundamental, underlying mechanism involved in the initiation and evolution of the neoplastic process. There is an ever growing body of evidence that all the important neoplastic phenotypes are driven by an alkalization of the transformed cell, a process which seems specific for transformed cells since the same alkalinization has no effect in cells that have not been transformed. Seen in that light, different fields of cancer research, from etiopathogenesis, cancer cell metabolism and neovascularization, to multiple drug resistance (MDR), selective apoptosis, modern cancer chemotherapy and the spontaneous regression of cancer (SRC) all appear to have in common a pivotal characteristic, the aberrant regulation of hydrogen ion dynamics [S. Harguindey, J.L. Pedraz, R. García Cañero, J. Pérez de Diego, E.J. Cragoe Jr., Hydrogen ion-dependent oncogenesis and parallel new avenues to cancer prevention and treatment using a H+-mediated unifying approach: pH-related and pH-unrelated mechanisms, Crit. Rev. Oncog. 6 (1) (1995) 1-33]. Cancer cells have an acid-base disturbance that is completely different than observed in normal tissues and that increases in correspondence with increasing neoplastic state: an interstitial acid microenvironment linked to an intracellular alkalosis.

Sensitized RNAi screen of human kinases and phosphatases identifies new regulators of apoptosis and chemoresistance

Evasion from apoptosis is a hallmark of cancer, and recent success using targeted therapeutics underscores the importance of identifying anti-apoptotic survival pathways. Here we utilize RNA interference (RNAi) to systematically screen the kinase and phosphatase component of the human genome. In addition to known kinases, we identified several new survival kinases. Interestingly, numerous phosphatases and associated regulatory subunits contribute to cell survival, revealing a previously unrecognized general role for phosphatases as negative regulators of apoptosis. We also identified a subset of phosphatases with tumour-suppressor-like activity. Finally, RNAi targeting of specific protein kinases sensitizes resistant cells to chemotherapeutic agents. The development of inhibitors that target these kinases or phosphatases may lead to new anti-cancer strategies.

Silibinin modulates UVB-induced apoptosis via mitochondrial proteins, caspases activation, and mitogen-activated protein kinase signaling in human epidermoid carcinoma A431 cells

Several recent studies by us have shown the strong chemopreventive efficacy of silibinin against both ultraviolet B (UVB) radiation and chemical carcinogen-induced tumorigenesis in mouse skin models. The molecular mechanisms underlying silibinin protective efficacy, however, are not completely known. Here, we examined the effect of silibinin on UVB-caused apoptosis in human epidermoid carcinoma A431 cells. Irradiation of cells with different doses of UVB (5-100 mJ/cm2) and different time periods (0.5-24h) resulted in a dose- and time-dependent increase in apoptosis (P < 0.05-0.001). Silibinin (100-200 microM) pre-treatment, however, resulted in an increase in UVB-induced apoptosis (P < 0.05-0.001); interestingly, its post-treatment caused a decrease in UVB-induced apoptosis (P < 0.05-0.001). A similar pattern in the activation of caspases-9, -3, and -7 was observed with these silibinin treatments. Further, silibinin treatment prior to or immediately after UVB exposure altered Bcl-2, Bax, Bak, and cytochrome c levels in mitochondria and cytosol in favor of or against apoptosis, respectively. Silibinin treatment prior to UVB also increased the activation of mitogen/stress activated protein kinases Erk1/2, JNK, and p38 kinase as compared to its post-treatment. Together, for the first time, our results demonstrate the role of mitochondrial apoptotic machinery and MAPK signaling cascade in silibinin-caused increase as well as protection in UVB-induced apoptosis in A431 cells, and suggest that similar mechanisms might be involved in preventive efficacy of silibinin against UVB-induced skin tumorigenesis.

Effects of seminal oil emulsion of Brucea javanica on apoptosis and apoptosis-related genes in human hepatocellular carcinoma cells

AIM: To explore the anti-tumor mechanism of seminal oil emulsion of Brucea javanica by studying in vitro its effects on apoptosis, cell cycle and expression of apoptosis-related genes p53 and Bcl-2 in human hepatocellular carcinoma cell line SMMC-7721.

METHODS: Anti-proliferation effect was measured by MTT assay. The morphology of cells was observed under transmission electron microscope. Agarose gel electrophoresis was used to analyze DNA character and the flow cytometry to detect apoptotic rate and cell cycle distribution. The levels of p53 and Bcl-2 protein were examined by immunocytochemical staining.

RESULTS: The proliferation of hepatocellular carcinoma cell line SMMC-7721 could be remarkably inhibited by seminal oil emulsion of Brucea javanica in a time- and concentration-dependent manner. Morphological and biochemical changes characteristic of apoptosis were observed through electron microscope and agarose gel electrophoresis. After 12, 24, 48 h incubation with 0.10 g/L emulsion of seminal oil of Brucea javanica, the flow cytometry showed typical subdiploid peaks and the cell cycle was arrested at G0/G1 phase(P < 0.05). The expression of p53 and Bcl-2 was down-regulated after exposure to the drug, with a positive correlation between them (r = 0.966, P < 0.05).

CONCLUSION: Seminal oil emulsion of Brucea javanica can significantly inhibit the proliferation of human hepatocellular carcinoma cell line SMMC-7721 in vitro through inducing apoptosis and arresting cell cycle at G0/G1 phase, and its underlying mechanism is related to the down-regulating mutant type p53 as well as Bcl-2, with p53 pathway playing a leading role.

Ras-MAP kinase signaling pathways and control of cell proliferation: relevance to cancer therapy

The mitogen-activated protein (MAP) kinase pathways represent several families of signal transduction cascades that mediate information provided by extracellular stimuli. MAP kinase pathways regulate a wide range of physiological responses, including cell proliferation, apoptosis, cell differentiation, and tissue development. Constitutive activation of MAP kinase proteins in experimental models has been shown to cause cell transformation and is implicated in tumorigenesis. Of clinical importance, MAP kinase pathways are regulated by Ras G-proteins, which are found to be mutated and constitutively active in approximately 30% of all human cancers. Thus, a major goal in the treatment of cancer is the development of specific compounds that target Ras and critical downstream signaling proteins responsible for uncontrolled cell growth. A variety of biochemical, molecular, and structural approaches have been used to develop drug compounds that target signaling proteins important for MAP kinase pathway activation. These compounds have been useful tools for identifying the mechanisms of MAP kinase pathway signaling and hold promise for clinical use. This review will present an overview of the major proteins involved in Ras and MAP kinase signaling pathways and their function in regulating cell cycle events and proliferation. In addition, some of the relevant compounds that have been developed to inhibit the activities of these proteins and MAP kinase signaling are discussed.