Paclitaxel induced apoptosis in breast cancer cells requires cell cycle transit but not Cdc2 activity

In-vivo studies of targeted and localized cancer drug release from microporous poly-di-methyl-siloxane (PDMS) devices for the treatment of triple negative breast cancer

Triple-negative breast cancer (TNBC) treatment is challenging and frequently characterized by an aggressive phenotype and low prognosis in comparison to other subtypes. This paper presents fabricated implantable drug-loaded microporous poly-di-methyl-siloxane (PDMS) devices for the delivery of targeted therapeutic agents [Luteinizing Hormone-Releasing Hormone conjugated paclitaxel (PTX-LHRH) and Luteinizing Hormone-Releasing Hormone conjugated prodigiosin (PG-LHRH)] for the treatment and possible prevention of triple-negative cancer recurrence. In vitro assessment using the Alamar blue assay demonstrated a significant reduction (p < 0.05) in percentage of cell growth in a time-dependent manner in the groups treated with PG, PG-LHRH, PTX, and PTX-LHRH. Subcutaneous triple-negative xenograft breast tumors were then induced in athymic female nude mice that were four weeks old. Two weeks later, the tumors were surgically but partially removed, and the device implanted. Mice were observed for tumor regrowth and organ toxicity. The animal study revealed that there was no tumor regrowth, six weeks post-treatment, when the LHRH targeted drugs (LHRH-PTX and LHRH-PGS) were used for the treatment. The possible cytotoxic effects of the released drugs on the liver, kidney, and lung are assessed using quantitative biochemical assay from blood samples of the treatment groups. Ex vivo histopathological results from organ tissues showed that the targeted cancer drugs released from the implantable drug-loaded device did not induce any adverse effect on the liver, kidneys, or lungs, based on the results of qualitative toxicity studies. The implications of the results are discussed for the targeted and localized treatment of triple negative breast cancer.

Discovery of Novel N-Heterocyclic-Fused Deoxypodophyllotoxin Analogues as Tubulin Polymerization Inhibitors Targeting the Colchicine-Binding Site for Cancer Treatment

Natural products are a major source of anticancer agents and play critical roles in anticancer drug development. Inspired by the complexity-to-diversity strategy, novel deoxypodophyllotoxin (DPT) analogues were designed and synthesized. Among them, compound C3 exhibited the potent antiproliferative activity against four human cancer cell lines with IC₅₀ values in the low nanomolar range. Additionally, it showed marked activity against paclitaxel-resistant MCF-7 cells and A549 cells. Moreover, compound C3 can inhibit tubulin polymerization by targeting the colchicine-binding site of tubulin. Further study revealed that compound C3 could arrest cancer cells in the G₂/M phase and disrupt the angiogenesis in human umbilical vein endothelial cells. Meanwhile, C3 remarkably inhibited cancer cell motility and migration, as well as considerably inhibited tumor growth in MCF-7 and MCF-7/TxR xenograft model without obvious toxicity. Collectively, these results indicated that compound C3 may be a promising tubulin polymerization inhibitor development for cancer treatment.

The Crosstalk Between Regulatory Non-Coding RNAs and Nuclear Factor Kappa B in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a highly lethal type of malignancies that possesses great loss of life safety to human beings worldwide. However, few effective means of curing HCC exist and its specific molecular basis is still far from being fully elucidated. Activation of nuclear factor kappa B (NF-κB), which is often observed in HCC, is considered to play a significant part in hepatocarcinogenesis and development. The emergence of regulatory non-coding RNAs (ncRNAs), particularly microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), is a defining advance in cancer biology, and related research in this branch has yielded many diagnostic and therapeutic opportunities. Recent studies have suggested that regulatory ncRNAs act as inhibitors or activators in the initiation and progression of HCC by targeting components of NF-κB signaling or regulating NF-κB activity. In this review, we attach importance to the role and function of regulatory ncRNAs in NF-κB signaling of HCC and NF-κB-associated chemoresistance in HCC, then propose future research directions and challenges of regulatory ncRNAs mediated-regulation of NF-κB pathway in HCC.

Atorvastatin facilitates chemotherapy effects in metastatic triple-negative breast cancer

BACKGROUND

Metastatic triple-negative breast cancer (mTNBC) is treated mainly with chemotherapy. However, resistance frequently occurs as tumours enter dormancy. Statins have been suggested as effective against cancer but as they prolong and promote dormancy, it is an open question of whether the concomitant use would interfere with chemotherapy in primary and mTNBC. We examined this question in animal models and clinical correlations.

METHODS

We used a xenograft model of spontaneous metastasis to the liver from an ectopic tumour employing a mTNBC cell line. Atorvastatin was provided to sensitise metastatic cells, followed by chemotherapy. The effects of statin usage on outcomes in women with metastatic breast cancer was assessed respectively by querying a database of those diagnosed from 1999 to 2019.

RESULTS

Atorvastatin had limited influence on tumour growth or chemotherapy effects in ectopic primary tumours. Interestingly, atorvastatin was additive with doxorubicin (but not paclitaxel) when targeting liver metastases. E-cadherin-expressing, dormant, breast cancer cells were resistant to the use of either statins or chemotherapy as compared to wild-type cells; however, the combination of both did lead to increased cell death. Although prospective randomised studies are needed for validation, our retrospective clinical analysis suggested that patients on statin treatment could experience prolonged dormancy and overall survival; still once the tumour recurred progression was not affected by statin use.

CONCLUSION

Atorvastatin could be used during adjuvant chemotherapy and also in conjunction with metastatic chemotherapy to reduce mTNBC cancer progression. These preclinical data establish a rationale for the development of randomised studies.

Sub-acute Toxicity Assessment of Taxol Isolated From Fusarium Solani, an Endophytic Fungus of Taxus Brevifolia, in Wistar Rats and Analyzing Its Cytotoxicity and Apoptotic Potential in Lung Cancer Cells

The limited availability of taxol from plant sources has prompted the scientific world to look for an alternative, as in the chemical synthesis of tissue cultures of the Taxus species, to meet the increasing demand for the drug. However, these alternative means are expensive or result in low yield. Previously, we have reported that Fusarium solani isolated from Taxus celebica produced taxol and its precursor baccatin III in liquid-grown cultures, and it exhibited promising anticancerous effects in certain cancer cell lines. In the present study, we examined the sub-acute toxicity of fungal taxol (FS) in Wistar rats according to the Organization for Economic Co-operation and Development (OECD) guidelines. The sub-acute oral administration of FS up to 500 mg/kg for a period of 28 days appears to be safe in rats and did not cause severe treatment-related toxicity or treatment-related death. The observed changes in body weight, histopathology, hematological and biochemical parameters, and organ weight were not significant compared to those in the control group of animals. The results suggest that FS is relatively safe when administered orally in rats. The antiproliferative and apoptosis-inducing activities were studied in A549 (human lung cancer) cell line. FS arrested the cells at S and G2/M phases, leading to apoptosis. The characteristic molecular signatures of apoptosis, such as externalized phosphatidyl serine, DNA fragmentation, and nuclear and chromatin condensation, were observed upon FS treatment. FS triggered the generation of reactive oxygen species in A549 cells and elicited cell death by both extrinsic as well as the mitochondria-mediated intrinsic pathway of apoptosis. These results indicate that endophytic fungi isolated from medicinal plants may serve as potential sources of anticancerous compounds with little side effects.

miR-31-5p may enhance the efficacy of chemotherapy with Taxol and cisplatin in TNBC

The limited efficacy of chemotherapy with Taxol (TAX) and cisplatin (DDP) in triple-negative breast cancer (TNBC) has prompted the investigation of combined therapies. Previous studies demonstrated that microRNA (miR)-31-5p is involved in various biological processes. In the present study, it was hypothesized that the overexpression of miR-31-5p may enhance the efficacy of chemotherapy. The expression levels of miR-31-5p in the TNBC cell lines MDA-MB-231 and MDA-MB-468 were measured using reverse transcription-quantitative PCR following transfection with miR-31-5p mimic or inhibitor. A Cell Counting Kit-8 and flow cytometry assays suggested that the overexpression of miR-31-5p inhibited cell proliferation and promoted apoptosis, and these effects were reversed by transfecting a miR-31-5p inhibitor into MDA-MB-231 and MDA-MB-468 cells. Furthermore, the overexpression of miR-31-5p increased the sensitivity of cells to chemotherapy, which exhibited an increase in apoptosis and in the expression level of Bax, and a decrease in the expression level of Bcl-2. Chemotherapy resistance induced by miR-31-5p inhibitor could be reversed by inhibiting the AKT signaling pathway in MDA-MB-231 and MDA-MB-468 cells. In conclusion, the present preclinical results indicated that targeting miR-31-5p may enhance the efficacy of TAX- and DDP-mediated chemotherapy in TNBC.

Shikonin potentiates paclitaxel antitumor efficacy in esophageal cancer cells via the apoptotic pathway

Shikonin is a natural naphthoquinone pigment that can suppress the growth of a number of cancer cell types. Paclitaxel is an antineoplastic chemotherapy drug, which is used for the treatment of various types of solid tumor cancer. However, acquired paclitaxel resistance results in the failure of therapy, and consequent metastasis and relapse. The aim of the present study was to investigate whether shikonin can sensitize esophageal cancer cells to paclitaxel-treatment and to elucidate the underlying mechanisms. The biological effects of these two agents on esophageal cancer cell lines KYSE270 and KYSE150 were investigated by MTT assay, cell cycle analysis, Annexin-V apoptosis assay, western blotting and reverse transcription-quantitative polymerase chain reaction. The results demonstrated that shikonin could significantly increase the cell growth inhibition effect induced by paclitaxel in the examined cell lines (P<0.001). The addition of shikonin to paclitaxel promoted cancer cell mitotic arrest and induced significantly higher levels of cell apoptosis. Notably, the mRNA and protein levels of Bcl-2 were downregulated, while p53 was upregulated in KYSE270 and KYSE150 cells following combined treatment. In summary, shikonin can sensitize esophageal cancer cells to paclitaxel-treatment by promoting cell mitotic arrest and reinforcing the susceptibility of esophageal cancer cells to apoptosis induced by paclitaxel, which is potentially associated with altered levels of Bcl-2 and p53.

Treatment response assessment with (R)-[11CPAQ PET in the MMTV-PyMT mouse model of breast cancer

Background

The goal of the study was to assess the potential of the vascular endothelial growth factor receptor (VEGFR)-2-targeting carbon-11 labeled (R)-N-(4-bromo-2-fluorophenyl)-6-methoxy-7-((1-methyl-3-piperidinyl)methoxy)-4-quinazolineamine ((R)-[¹¹C]PAQ) as a positron emission tomography (PET) imaging biomarker for evaluation of the efficacy of anticancer drugs in preclinical models.

Methods

MMTV-PyMT mice were treated with vehicle alone (VEH), murine anti-VEGFA antibody (B20-4.1.1), and paclitaxel (PTX) in combination or as single agents. The treatment response was measured with (R)-[¹¹C]PAQ PET as standardized uptake value (SUV)_mean, SUV_max relative changes at the baseline (day 0) and follow-up (day 4) time points, and magnetic resonance imaging (MRI)-derived PyMT mammary tumor volume (TV) changes. Expression of Ki67, VEGFR-2, and CD31 in tumor tissue was determined by immunohistochemistry (IHC). Non-parametric statistical tests were used to evaluate the relation between (R)-[¹¹C]PAQ radiotracer uptake and therapy response biomarkers.

Results

The (R)-[¹¹C]PAQ SUV_max in tumors was significantly reduced after 4 days in the B20-4.1.1/PTX combinational and B20-4.1.1 monotherapy groups (p < 0.0005 and p < 0.003, respectively). No significant change was observed in the PTX monotherapy group. There was a significant difference in the SUV_max change between the VEH group and B20-4.1.1/PTX combinational group, as well as between the VEH group and the B20-4.1.1 monotherapy group (p < 0.05). MRI revealed significant decreases in TV in the B20-4.1.1/PTX treatment group (p < 0.005) but not the other therapy groups. A positive trend was observed between the (R)-[¹¹C]PAQ SUV_max change and TV reduction in the B20-4.1.1/PTX group. Statistical testing showed a significant difference in the blood vessel density between the B20-4.1.1/PTX combinational group and the VEH group (p < 0.05) but no significant difference in the Ki67 positive signal between treatment groups.

Conclusions

The results of this study are promising. However, additional studies are necessary before (R)-[¹¹C]PAQ can be approved as a predictive radiotracer for cancer therapy response.

Oxamate potentiates taxol chemotherapeutic efficacy in experimentally-induced solid ehrlich carcinoma (SEC) in mice

Several human cancers including the breast display elevated expression of Lactate dehydrogenase-A (LDH-A), the enzyme that converts pyruvate to lactate and oxidizes NADH to NAD⁺. Indeed, tumor lactate levels correlate with increased metastasis, tumor recurrence, and poor outcome. Lactate also plays roles in promoting tumor inflammation and as a signaling molecule that stimulates tumor angiogenesis. Because of its essential role in cancer metabolism, LDH-A has been considered as a potential target for combination cancer therapy. Therefore, the current study investigated the possible anti-tumor effect of LDH inhibitor (oxamate) in a murine model of breast cancer [Solid Ehrlich Carcinoma (SEC)], alone and in combination with Taxol chemotherapy. The potential underlying mechanisms were also investigated. The results indicated that oxamate induced significant anti-tumor activity against the SEC. Mechanistically, the combination treatment was more efficient than paclitaxel monotherapy in reducing ATP, MDA, TNF-α and Il-17 contents in SEC. Moreover, the apoptotic and anti-angiogenic effects of the combination treatment were triggered more efficiently as compared to paclitaxel monotherapy, Therefore, oxamate may represent a promising agent that enhance the antitumor activity of paclitaxel.

Suppression of pyruvate dehydrogenase kinase-2 re-sensitizes paclitaxel-resistant human lung cancer cells to paclitaxel

Despite impressive initial clinical responses, the majority of lung cancer patients treated with paclitaxel eventually develop resistance to the drug. Pyruvate dehydrogenase kinase-2 (PDK2) is a key regulator of glycolysis and oxidative phosphorylation, and its expression is increased in a variety of tumors. In this study, the role of PDK2 in mediating paclitaxel resistance in lung cancer cells was investigated using biochemical and isotopic tracing methods. Increased expression of PDK2 was observed in paclitaxel-resistant cells ascompared totheir parental cells. Down-regulation of PDK2 usingsiRNA increased the sensitivity to paclitaxel of resistant lung cancer cells. Targeting paclitaxel-resistant cells throughPDK2 knockdown was associated with reduced glycolysis rather than increased oxidative phosphorylation (OXPHOS). Moreover, combining paclitaxel withthe specific PDK2 inhibitor dichloroacetate had a synergistic inhibitory effect on the viability of paclitaxel-resistant lung cancer cells. These results indicate that paclitaxel-induced expression of PDK2 serves as an important mechanism for acquired paclitaxel resistance of lung cancer cells. They also highlight the importance of PDK2 for potential therapeutic interventions in patients who have developed a resistance to paclitaxel.

Targeted inhibitory effect of Lenti-SM22alpha-p27-EGFP recombinant lentiviral vectors on proliferation of vascular smooth muscle cells without compromising re-endothelialization in a rat carotid artery balloon injury model

AIMS

In-stent restenosis remains a serious problem after the implantation of drug-eluting stents, which is attributable to neointima formation and re-endothelialization. Here, we tried to find a new method which aims at selectively inhibiting proliferation of vascular smooth muscle cells (VSMC) proliferation without inhibition of re-endothelialization.

METHODS AND RESULTS

We used the smooth muscle-specific SM22alpha promoter in a recombinant lentiviral vector to drive overexpression of cell-cycle inhibitor, p27, in VSMCs. p27 effectively inhibited VSMC proliferation mediated by cell cycle arrest at the G0/G1 checkpoint. The SM22alpha-p27 lentiviral vector inhibited VSMC proliferation more effectively than paclitaxel. Rats infected with Lenti-SM22alpha-p27 had a significantly lower intima/media (I/M) ratio and also showed inhibition of restenosis on day 28 after balloon injury. Moreover, the repair of injured endothelium, and re-endothelialization of the carotid artery wall, was not affected by the smooth muscle cell-specific expression of p27.

CONCLUSION

A recombinant lentiviral vector carrying the SM22alpha promoter was used to effectively infect and selectively overexpress p27 protein in VSMCs, leading to inhibition of intimal hyperplasia without compromising endothelial repair.

MiR-16 targets Bcl-2 in paclitaxel-resistant lung cancer cells and overexpression of miR-16 along with miR-17 causes unprecedented sensitivity by simultaneously modulating autophagy and apoptosis

Non-small cell lung cancer is one of the most aggressive cancers as per as the mortality and occurrence is concerned. Paclitaxel based chemotherapeutic regimes are now used as an important option for the treatment of lung cancer. However, resistance of lung cancer cells to paclitaxel continues to be a major clinical problem nowadays. Despite impressive initial clinical response, most of the patients eventually develop some degree of paclitaxel resistance in the course of treatment. Previously, utilizing miRNA arrays we reported that downregulation of miR-17 is at least partly involved in the development of paclitaxel resistance in lung cancer cells by modulating Beclin-1 expression [1]. In this study, we showed that miR-16 was also significantly downregulated in paclitaxel resistant lung cancer cells. We demonstrated that anti-apoptotic protein Bcl-2 was directly targeted miR-16 in paclitaxel resistant lung cancer cells. Moreover, in this report we showed that the combined overexpression of miR-16 and miR-17 and subsequent paclitaxel treatment greatly sensitized paclitaxel resistant lung cancer cells to paclitaxel by inducing apoptosis via caspase-3 mediated pathway. Combined overexpression of miR-16 and miR-17 greatly reduced Beclin-1 and Bcl-2 expressions respectively. Our results indicated that though miR-17 and miR-16 had no common target, both miR-16 and miR-17 jointly played roles in the development of paclitaxel resistance in lung cancer. miR-17 overexpression reduced cytoprotective autophagy by targeting Beclin-1, whereas overexpression of miR-16 potentiated paclitaxel induced apoptotic cell death by inhibiting anti-apoptotic protein Bcl-2.

Inherent and acquired resistance to paclitaxel in hepatocellular carcinoma: molecular events involved

Hepatocellular carcinoma (HCC) is a primary malignancy of the liver and is a major cause of cancer related deaths worldwide. Only 10 to 20% of HCC can be surgically excised. Therefore, chemotherapeutic intervention and treatment is essential for achieving favorable prognosis. However, therapeutic outcome of chemotherapy is generally poor owing to inherent resistance of cancer cells to the treatment or due to development of acquired resistance. To differentiate and delineate the molecular events, we developed drug resistant Hep3B cells (DRC) by treating cells with the increasing concentration of paclitaxel. We also developed a unique single cell clone of Hep3B cells (SCC) by selecting single cell colonies and screening them for resistant phenotype. Interestingly, both DRC and SCC were resistant to paclitaxel in comparison to parental Hep3B cells. We analyzed the contributory factors that may be involved in the development of resistance. As expected, level of P-glycoprotein (P-gp) was elevated in DRC. In addition, Caveolin-1 (Cav-1), Fatty acid synthase (FASN) and Cytochrome P450 (CYP450) protein levels were elevated in DRC whereas in SCC, FASN and CYP450 levels were elevated. Downregulation of these molecules by respective siRNAs and/or by specific pharmacological inhibitors resensitized cells to paclitaxel. Interestingly, these drug resistant cells were also less sensitive to vinblastine, doxorubicin and methotrexate with the exception of cisplatin. Our results suggested that differential levels of P-gp, Cav-1 and FASN play a major role in acquired resistant phenotype whereas FASN level was associated with the presentation of inherent resistant phenotype in HCC.

Engineered 3D environments to elucidate the effect of environmental parameters on drug response in cancer

Traditional in vitro models used for the development of anti-cancer drugs are based on the monolayer culture of cells, which has a limited predictivity of in vivo efficacy. A number of cell culture platforms have been developed in recent years to improve predictivity and further to elucidate the mechanisms governing the differing responses observed in vitro versus in vivo. One detrimental aspect of current in vitro models is their inability to decouple the effect of different extrinsic factors on the responsiveness of the cells to drug treatment. Here, we have used an engineered poly(dimethylsiloxane) (PDMS) microwell array as a reductionist approach to study the effect of environmental parameters, independently of each other. It is observed for MCF-7 breast cancer cells, that culture within the three-dimensional (3D) environment of the microwells alone had an effect on the response to Taxol and results in a reduction of cell death in comparison to cells cultured on flat substrates. Additionally the microwells allowed the response of single versus multicell clusters to be differentiated. It was found that the formation of cell-cell contacts alters the drug response, depending on the type of adhesive protein present. Thus, with this microwell platform it is revealed that the presence of cell-cell contacts in addition to the dimensionality and the matrix composition of the environment are important mediators of altered drug responses. In conclusion the microwell array can not only serve as a platform to reveal which parameters of the extracellular environment affect drug response but further the interdependence of these parameters.

MicroRNA-125b confers the resistance of breast cancer cells to paclitaxel through suppression of pro-apoptotic Bcl-2 antagonist killer 1 (Bak1) expression

Paclitaxel (Taxol) is an effective chemotherapeutic agent for treatment of cancer patients. Despite impressive initial clinical responses, the majority of patients eventually develop some degree of resistance to Taxol-based therapy. The mechanisms underlying cancer cells resistance to Taxol are not fully understood. MicroRNA (miRNA) has emerged to play important roles in tumorigenesis and drug resistance. However, the interaction between the development of Taxol resistance and miRNA has not been previously explored. In this study we utilized a miRNA array to compare the differentially expressed miRNAs in Taxol-resistant and their Taxol-sensitive parental cells. We verified that miR-125b, miR-221, miR-222, and miR-923 were up-regulated in Taxol-resistant cancer cells by real-time PCR. We further investigated the role and mechanisms of miR-125b in Taxol resistance. We found that miR-125b was up-regulated in Taxol-resistant cells, causing a marked inhibition of Taxol-induced cytotoxicity and apoptosis and a subsequent increase in the resistance to Taxol in cancer cells. Moreover, we demonstrated that the pro-apoptotic Bcl-2 antagonist killer 1 (Bak1) is a direct target of miR-125b. Down-regulation of Bak1 suppressed Taxol-induced apoptosis and led to an increased resistance to Taxol. Restoring Bak1 expression by either miR-125b inhibitor or re-expression of Bak1 in miR-125b-overexpressing cells recovered Taxol sensitivity, overcoming miR-125-mediated Taxol resistance. Taken together, our data strongly support a central role for miR-125b in conferring Taxol resistance through the suppression of Bak1 expression. This finding has important implications in the development of targeted therapeutics for overcoming Taxol resistance in a number of different tumor histologies.

Warburg effect in chemosensitivity: targeting lactate dehydrogenase-A re-sensitizes taxol-resistant cancer cells to taxol

BACKGROUND

Taxol is one of the most effective chemotherapeutic agents for the treatment of patients with breast cancer. Despite impressive clinical responses initially, the majority of patients eventually develop resistance to Taxol. Lactate dehydrogenase-A (LDH-A) is one of the predominant isoforms of LDH expressed in breast tissue, which controls the conversion of pyruvate to lactate and plays an important role in glucose metabolism. In this study we investigated the role of LDH-A in mediating Taxol resistance in human breast cancer cells.

RESULTS

Taxol-resistant subclones, derived from the cancer cell line MDA-MB-435, sustained continuous growth in high concentrations of Taxol while the Taxol-sensitive cells could not. The increased expression and activity of LDH-A were detected in Taxol-resistant cells when compared with their parental cells. The downregulation of LDH-A by siRNA significantly increased the sensitivity of Taxol-resistant cells to Taxol. A higher sensitivity to the specific LDH inhibitor, oxamate, was found in the Taxol-resistant cells. Furthermore, treating cells with the combination of Taxol and oxamate showed a synergistical inhibitory effect on Taxol-resistant breast cancer cells by promoting apoptosis in these cells.

CONCLUSION

LDH-A plays an important role in Taxol resistance and inhibition of LDH-A re-sensitizes Taxol-resistant cells to Taxol. This supports that Warburg effect is a property of Taxol resistant cancer cells and may play an important role in the development of Taxol resistance. To our knowledge, this is the first report showing that the increased expression of LDH-A plays an important role in Taxol resistance of human breast cancer cells. This study provides valuable information for the future development and use of targeted therapies, such as oxamate, for the treatment of patients with Taxol-resistant breast cancer.

9-bromonoscapine-induced mitotic arrest of cigarette smoke condensate-transformed breast epithelial cells

In the present investigation, we determined the chemotherapeutic efficacy of 9-bromonoscapine (Br-Nos), a more potent noscapine analog, on MCF10A, spontaneously immortalized human normal breast epithelial cells and MCF10A-CSC3, cigarette smoke condensate (CSC)-transformed cells. The results from cytogenetic analysis showed that Br-Nos induced polyploidy and telomeric association in MCF10A-CSC3 cells, while MCF10A cells remained unaffected. Our immunofluorescence data further demonstrated that MCF10A-CSC3 cells were susceptible to mitotic catastrophe on exposure to Br-Nos and failed to recover after drug withdrawal. MCF10A-CSC3 cells exhibited Br-Nos-induced aberrant multipolar spindle formation, which irreversibly impaired the alignment of replicated chromosome to the equatorial plane and finally culminated in cell death. Although MCF10A cells upon Br-Nos treatment showed bipolar spindles with some uncongressed chromosomes, these cells recovered fairly well after drug withdrawal. Our flow-cytometry analysis data reconfirmed that MCF10A-CSC3 cells were more susceptible to cell death compared to MCF10A cells. Furthermore, our results suggest that decreased levels of cdc2/cyclin B1 and cdc2 kinase activity are responsible for Br-Nos-induced mitotic cell arrest leading to cell death in MCF10A-CSC3 cells. This study thus explores the underlying mechanism of Br-Nos-induced mitotic catastrophe in CSC-transformed MCF10A-CSC3 cells and its potential usefulness as a chemotherapeutic agent for prevention of cigarette smoke-induced breast cancer growth.

Differential effects of retinol and retinoic acid on cell proliferation: a role for reactive species and redox-dependent mechanisms in retinol supplementation

While some authors suggest that retinoids are potential anti-proliferative and antioxidant agents, evidence has suggested those present pro-oxidant properties, which might lead to malignant proliferation. These discordances stimulated one to investigate the proliferative/anti-proliferative properties of two major retinoids, retinol (ROH) and retinoic acid (RA). In Sertoli cells, ROH increased proliferation while RA was anti-proliferative. ROH increased DNA synthesis, decreased p21 levels and induced cell cycle progression. ROH increased reactive species (RS) production and stimulated p38, JNK1/2 and ERK1/2 MAPKs activation. Antioxidant treatment with Trolox blocked ROH-induced RS production, MAPKs activation and proliferation; MAPKs inhibition blocked proliferation. The potential sites of RS indicate that ROH-induced RS is promoted via mitochondria and xanthine oxidase. In contrast, RA induced neither RS production nor MAPKs activation. RA decreased DNA synthesis and increased p21 leading to cell arrest. Overall, data show that ROH, but not RA, is able to induce proliferation through non-classical and redox-dependent mechanisms.

The characteristics of Hep-2 cell with multiple drug resistance induced by Taxol

OBJECTIVE

To investigate the characteristics of Hep-2 cell with multidrug resistance (MDR) induced by Taxol.

STUDY DESIGN

Hep-2 cells were exposed in stepwise escalating concentration of Taxol to develop the resistant cell line-Hep-2T. Cell cycle distribution, apoptosis, and rhodamine accumulation were studied through flow cytometry. The MDR1 and MRP1 genes were detected through real-time quantitative RT-PCR, and the corresponding proteins were detected through Western blotting.

RESULTS

The drug resistance of Hep-2T cells to Taxol, doxorubicin, gemcitabine, 5-FU, and cisplatin all increased. The percentage of G0/G1 phase and the antiapoptosis ability increased significantly compared with Hep-2 cells. Both MDR1 and MRP1 also increased at gene and protein level, though MDR1 was more prominent.

CONCLUSION

More emphasis should be laid on MDR1/Pgp, the non-Pgp substrate chemotherapeutic agents, and the changes of cell cycle distribution to prevent MDR induced by Taxol.

SIGNIFICANCE

These findings may provide theoretical support for the reverse of MDR.