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

Differential expression of ABCB1, ABCG2, and KLF4 as putative indicators for paclitaxel resistance in human epithelial type 2 cells

Laryngeal squamous cell carcinoma (LSCC) is the second most common malignancy of the head and neck region in the USA with a declining 5-year survival rate. Paclitaxel resistance of tumors including LSCC still stands as a vital cause for poor clinical outcome in patients. In the current study, our aim was to explore the expressions of ATP-binding cassette transporters and stemness associated genes in human epithelial type 2 (Hep-2) cells with paclitaxel resistance. Resistant cells were developed via treatment with increasing doses of paclitaxel to acquire four sub-lines resistant to one-, two-, four-, and eightfold concentrations of paclitaxel (1×, 2×, 4×, 8×). Then, we profiled the expressions of ten selected ABC transporters (ABCA5, ABCB1, ABCB6, ABCC1, ABCC2, ABCC3, ABCC5, ABCC10, ABCF2, and ABCG2) and four stem cell markers (SOX2, OCT4, KLF, and CXCR4) using quantitative real time polymerase chain reaction in paclitaxel resistant cells to look for a link between these markers and chemoresistance. We demonstrated that ABCB1 and ABCG2 expressions gradually elevated and reached a maximum level in Taxol 8× cells. Considering stem cell markers, KLF4 expression elevated significantly, as soon as parental cells acquired resistance to the lowest dose of paclitaxel and its expression elevated stepwise. Expression levels of other tested ATP-binding cassette transporters and stem cell markers also elevated, although at different steps of paclitaxel resistance acquisition. Our findings suggest that higher expressions of ABCB1, ABCG2, and KLF4 might be considered as putative indicators for paclitaxel resistance in LSCC patients.

Expression profile of stem cell markers and ABC transporters in 5-fluorouracil resistant Hep-2 cells

Resistance of laryngeal squamous cell carcinoma cells to traditional therapeutic regimens still remains to be a major reason for therapeutic failure in patients. In this study, we aimed at investigating the expression profiles of ATP-binding cassette (ABC) transporters and stem cell markers in 5-fluorouracil (5-FU) resistant laryngeal Hep-2 cells. We treated parental Hep-2 cells, with stepwise increased doses of 5-FU for almost 1 year to develop 5-FU resistant sub-lines with resistance against varying levels of 5-FU concentrations (4 sub-lines resistant to 1, 2, 4, and eightfold of 5-FU). Then, we measured the expression levels of 10 genes from ABC transporters family and 4 stem cell associated markers using quantitative reverse transcription polymerase chain reaction (qRT-PCR) to find out a potential relationship between these markers and chemoresistance. We found that stemness-associated markers had elevated expressions from the beginning of 5-FU resistance acquisition. Their expressions elevated stepwise while parental Hep-2 cells got resistance to higher doses of 5-FU. Expressions of tested ABC transporters (ABCA5, ABCB1, ABCB6, ABCC1, ABCC2, ABCC3, ABCC5, ABCC10 and ABCF2, and ABCG2) were also deregulated in 5-FU resistant Hep-2 cells. Although their expressions remained unaltered at the beginning of acquisition of resistance, expressions of ABC transporters except from ABCB6 increased significantly when cells became resistant to higher doses of 5-FU. Our results suggest that enrichment of cells with stemness characteristics and upregulation of ABC transporters might be amongst the crucial contributors of chemoresistance in laryngeal cancer cells.

Ovarian Primary and Metastatic Tumors Suppressed by Survivin Knockout or a Novel Survivin Inhibitor

Survivin, a member of the inhibitor of apoptosis family, is upregulated in multiple cancers including ovarian cancer, but is rarely detectable in normal tissues. We previously reported that survivin promoted epithelial-to-mesenchymal transition (EMT) in ovarian cancer cells, suggesting that survivin may contribute to ovarian tumor metastasis and chemoresistance. In this study, we tested whether knockout or pharmacologic inhibition of survivin overcomes chemoresistance and suppresses tumor metastasis. The genetic loss of survivin suppressed tumor metastasis in an orthotopic ovarian cancer mouse model. To pharmacologically test the role of survivin on ovarian tumor metastasis, we treated chemo-resistant ovarian cancer cells with a selective survivin inhibitor, MX106, and found that MX106 effectively overcame chemoresistance in vitro MX106 inhibited cell migration and invasion by attenuating the TGFβ pathway and inhibiting EMT in ovarian cancer cells. To evaluate the efficacy of MX106 in inhibiting ovarian tumor metastasis, we treated an orthotopic ovarian cancer mouse model with MX106, and found that MX106 efficiently inhibited primary tumor growth in ovaries and metastasis in multiple peritoneal organs as compared with vehicle-treated control mice. Our data demonstrate that inhibition of survivin using either genetic knockout or a novel inhibitor MX106 suppresses primary ovarian tumor growth and metastasis, supporting that targeting survivin could be an effective therapeutic approach in ovarian cancer.

Novel oxazolinoanthracyclines as tumor cell growth inhibitors-Contribution of autophagy and apoptosis in solid tumor cells death

Chemical modification of known, effective drugs are one method to improve the chemotherapy of tumors. We reported ability of oxazoline analogs of doxorubicin (O-DOX) and daunorubicin (O-DAU) to induce apoptosis and autophagy in ovarian and liver cancer cells. Reactive oxygen and nitrogen species (ROS and RNS, respectively), together with intracellular calcium-mediated downstream signaling, are essential for the anticancer effect of these new anthracycline analogs. The changes of mitochondrial membrane potential and induction of the ceramide pathway suggests that these compounds induce cell death by apoptosis. In addition, a significant increase of autophagosome formation was observed by fluorescence assay and acridine orange staining, indicating that the new analogs also induce autophagic cell death. Compared to free DOX- and DAU-treated cells, we observed inhibition of colony formation and migration, a time-dependency between ROS/RNS levels and a greater fall in mitochondrial membrane potential. Altogether, our research broadens the base of molecular oxazolinoanthracyclines targets and reveals that derivatives mediated oxidative stress, ceramide production and increase in intracellular calcium level by mitochondria. Furthermore, our data highlight the importance of mitochondria that simultaneously assume the role of activator of autophagy and apoptosis signals.

Cancer stem cell mediated acquired chemoresistance in head and neck cancer can be abrogated by aldehyde dehydrogenase 1 A1 inhibition

Chemoresistance leading to disease relapse is one of the major challenges to improve outcome in head and neck cancers. Cancer Stem Cells (CSCs) are increasingly being implicated in chemotherapy resistance, this study investigates the correlation between CSC behavior and acquired drug resistance in in vitro cell line models. Cell lines resistant to Cisplatin (Cal-27 CisR, Hep-2 CisR) and 5FU (Cal-27 5FUR) with high Resistance Indices (RI) were generated (RI ≥ 3) by short-term treatment of head and neck squamous cell carcinoma (HNSCC) cell lines with chemotherapeutic drugs (Cisplatin, Docetaxel, 5FU), using a dose-incremental strategy. The cell lines (Cal-27 DoxR, Hep-2 DoxR, Hep-2 5FUR) that showed low RI, nevertheless had a high cross resistance to Cisplatin/5FU (P < 0.05). Cal-27 CisR and DoxR showed 12-14% enrichment of CD44+ cells, while CisR/5FUR showed 4-6% increase in ALDH1A1+ cells as compared to parental cells (P < 0.05). Increased expression of stem cell markers (CD44, CD133, NOTCH1, ALDH1A1, OCT4, SOX2) in these cell lines, correlated with enhanced spheroid/colony formation, migratory potential, and increased in vivo tumor burden (P < 0.05). Inhibition of ALDH1A1 in Cal-27 CisR led to down regulation of the CSC markers, reduction in migratory, self-renewal and tumorigenic potential (P < 0.05) accompanied by an induction of sensitivity to Cisplatin (P < 0.05). Further, ex vivo treatment of explants (n = 4) from HNSCC patients with the inhibitor (NCT-501) in combination with Cisplatin showed a significant decrease in proliferating cells as compared to individual treatment (P = 0.001). This study hence suggests an ALDH1A1-driven, CSC-mediated mechanism in acquired drug resistance of HNSCC, which may have therapeutic implications. © 2016 Wiley Periodicals, Inc.

Effect of multidrug resistance 1/P-glycoprotein on the hypoxia-induced multidrug resistance of human laryngeal cancer cells

In a previous study, it was demonstrated that hypoxia upregulated the multidrug resistance (MDR) of laryngeal cancer cells to chemotherapeutic drugs, with multidrug resistance 1 (MDR1)/P-glycoprotein (P-gp) expression also being upregulated. The present study aimed to investigate the role and mechanism of MDR1/P-gp on hypoxia-induced MDR in human laryngeal carcinoma cells. The sensitivity of laryngeal cancer cells to multiple drugs and cisplatin-induced apoptosis was determined by CCK-8 assay and Annexin-V/propidium iodide staining analysis, respectively. The accumulation of rhodamine 123 (Rh123) in the cells served as an estimate of drug accumulation and was evaluated by flow cytometry (FCM). MDR1/P-gp expression was inhibited using interference RNA, and the expression of the MDR1 gene was analyzed using reverse transcription-quantitative polymerase chain reaction and western blotting. As a result, the sensitivity to multiple chemotherapeutic agents and the apoptosis rate of the hypoxic laryngeal carcinoma cells increased following a decrease in MDR1/P-gp expression (P<0.05). Additionally, FCM analysis of fluorescence intensity indicated that the downregulated expression of MDR1/P-gp markedly increased intracellular Rh123 accumulation (P<0.05). Such results suggest that MDR1/P-gp serves an important role in regulating hypoxia-induced MDR in human laryngeal carcinoma cells through a decrease in intracellular drug accumulation.

Trichostatin A potentiates genistein-induced apoptosis and reverses EMT in HEp2 cells

Genistein and trichostatin A (TSA) are two chemotherapeutic compounds with antitumor effects in different types of cancer cell. However, the effects of genistein and TSA on the HEp-2 laryngeal cancer cell line remain to be fully elucidated. In the present study, it was found that genistein and TSA inhibited cell growth and cell migration, and promoted apoptosis in the HEp-2 laryngeal cancer cell line. The HEp-2 cells were treated with genistein, TSA or the two compounds in combination. Cell proliferation and apoptosis were measured using an MTT assay, Annexin V/propidium iodide staining and a TUNEL assay. Cell invasion was determined using a Matrigel-based Transwell assay. Western blotting was used to examine the activation of the Akt pathway and the expression levels of pro-or anti-apoptotic proteins. Treatment with either genistein or TSA alone mildly inhibited cell viability, growth and invasion, and induced the apoptosis of the laryngeal cancer cells, whereas more marked effects were observed in the cells treated with the combination of the two compounds. In addition, genistein reversed endothelial growth factor-induced epithelial-mesenchymal transition (EMT) in the HEp-2 cells, the effect of which were was further increased by joint application with TSA. Treatment of the HEp-2 cells with genistein and TSA led to a significant reduction in the phosphorylation of Akt and activation of its downstream target, and resulted in peroxisome proliferator-activated receptor-γ cleavage, increased expression of B cell lymphoma-2 (Bcl-2)-associated X protein and reduced the expression of Bcl-2. In conclusion, the present study demonstrated that, with the involvement of TSA, genistein exhibited substantial advantages in inhibiting laryngeal carcinoma cell growth, invasion and EMT, and induced apoptosis, compared with genistein treatment alone, which occurred through the regulation of Akt activation and the apoptotic pathway.

The role of the SHH gene in prostate cancer cell resistance to paclitaxel

BACKGROUND

The increased activity of the Sonic Hedgehog (SHH) pathway has been demonstrated in many types of cancer including prostate cancer (PCa). It has been shown that SHH pathway is involved in tumor angiogenesis and in regulation of metabolism of cancer stem cells. The increased activity of the SHH pathway is responsible for generation and maintenance of the multidrug resistance in cancer cells. A key role in the development of this insensitivity to cytotoxic drugs play ATP-binding cassette (ABC) transporters.

METHODS

SHH encoding plasmid was stably transfected into PCa cell lines DU145 and LNCaP. The expression of SHH was silenced by shRNA and the level of SHH was tested by quantitative (q)PCR and western blot methods. The effect of SHH overexpression in cells after treatment with paclitaxel was measured by MTT assay, crystal violet assay and flow cytometry. The level of 44 ABC transporters was estimated by qPCR.

RESULTS

Expression of exogenous SHH protein in DU145 and LNCaP cell lines enhanced their resistance to paclitaxel along with increased expression of ABC transporters transcripts. Paclitaxel treatment further enhanced the expression of increased ABC transporters transcripts in cells overexpressing SHH.

CONCLUSIONS

Overexpression of SHH enhances PCa cell lines resistance to paclitaxel. Higher level of SHH leads to increase in ABC transporters expression in a manner dependent on paclitaxel.

Hypoxia induced multidrug resistance of laryngeal cancer cells via hypoxia-inducible factor-1α

OBJECTIVES

To investigate whether hypoxia has an effect on regulation of multidrug resistance (MDR) to chemotherapeutic drugs in laryngeal carcinoma cells and explore the role of hypoxia-inducible factor-1α (HIF- 1α).

METHODS

Laryngeal cancer cells were cultured under normoxic and hypoxic conditions. The sensitivity of the cells to multiple drugs and levels of apoptosis induced by paclitaxel were determined by MTT assay and annexin-V/propidium iodide staining analysis, respectively. HIF-1α expression was blocked by RNA interference. The expression of HIF-1α gene was detected by real-time quantitative RT-PCR and Western blotting. The value of fluorescence intensity of intracellular adriamycin accumulation and retention in cells was evaluated by flow cytometry.

RESULTS

The sensitivity to multiple chemotherapy agents and induction of apoptosis by paclitaxel could be reduced by hypoxia (P<0.05). A the same time, the adriamycin releasing index of cells was increased (P<0.05). However, resistance acquisition subject to hypoxia in vitro was suppressed by down-regulating HIF-1α expression.

CONCLUSION

HIF-1α could be considered as a key regulator for mediating hypoxia-induced MDR in laryngeal cancer cells via inhibition of drug-induced apoptosis and decrease in intracellular drug accumulation.

The connection between the toxicity of anthracyclines and their ability to modulate the P-glycoprotein-mediated transport in A549, HepG2, and MCF-7 cells

Multidrug resistance (MDR) is a major obstacle to the successful chemotherapy of solid tumors. We compared the resistance of the most popular solid tumors, breast adenocarcinoma (MCF-7 cell line) and nonsmall cell lung (A549 cell line) hepatocellular liver carcinoma (HepG2 cells), to aclarubicin (ACL) and doxorubicin (DOX). This research aimed at determining the relation between the toxicity of ACL and DOX, their cell accumulation, and then effect on P-glycoprotein functionality. ACL is more cytotoxic for tumor cells compared to DOX. The intracellular concentration of drugs in cancer cells was dependent on the dose of the drugs and the time of incubation. The P-gp inhibitor Verapamil (V) increased DOX accumulation in all tested cell lines. By contrast, the intracellular level of ACL was not affected by this modifying agent. The assessment of the uptake of 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolocarbocyanine iodide (JC-1) or Rhodamine 123 (R123) allows the evaluation of the different influence of drugs on P-gp activity which is in agreement with the estimation of expression measured by MDR-1 shift assay. These data suggest that ACL is less P-gp dependent than DOX and consequently may be used in a clinical setting to increase treatment efficacy in resistant human tumors.

Expression and significance of hypoxia-inducible factor-1α and MDR1/P-glycoprotein in laryngeal carcinoma tissue and hypoxic Hep-2 cells

The present study aimed to evaluate the expression of hypoxia-inducible factor-1α (HIF-1α) and MDR1/P-glycoprotein (P-gp) in human laryngeal squamous cell carcinoma (LSCC) tissues, and also to investigate the regulation of MDR1 gene expression by HIF-1α in Hep-2 cells under hypoxic conditions. The expression of HIF-1α and MDR1/P-gp in human LSCC tissues was examined using immunohistochemistry. The HIF-1α and MDR1 gene expression in the Hep-2 cells was detected using real-time quantitative reverse transcription (QRT)-PCR and western blot analysis under normoxic and hypoxic conditions. In hypoxia, HIF-1α expression was inhibited by RNA interference. HIF-1α and MDR1/P-gp expression was high in the LSCC tissues and was associated with the clinical stage and lymph node metastasis (P<0.05). HIF-1α expression was positively correlated with MDR1/P-gp expression (P<0.01). In the Hep-2 cells, HIF-1α and MDR1/P-gp expression significantly increased in response to hypoxia. The inhibition of HIF-1α expression synergistically downregulated the expression of the MDR1 gene in hypoxic Hep-2 cells. HIF-1α expression is positively correlated with MDR1/P-gp expression in LSCC, and the two proteins may be able to serve as potential biomarkers for predicting the malignant progression and metastasis of LSCC. HIF-1α may be critical for the upregulation of MDR1 gene expression induced by hypoxia in Hep-2 cells.

Expression of ABC transporters is an unfavorable prognostic factor in laryngeal squamous cell carcinoma

OBJECTIVES

Two prominent and well-characterized representatives of adenosine triphosphate-binding cassette (ABC) transporter - breast cancer resistance protein (BCRP or ABCG2) and P-glycoprotein (P-gp or ABCB1) - are known to be membrane transporters associated with multidrug resistance. The aim of this study was to explore the correlation between ABC transporter expression and the clinicopathologic characteristics, proliferative index, and apoptotic index and their prognostic value in laryngeal squamous cell carcinoma (LSCC).

METHODS

Paraffin sections of 98 human LSCC specimens were investigated with immunohistochemical techniques. The relationship between ABCG2 and ABCB1 expression and clinicopathologic parameters, proliferative activities, and apoptotic activities and their prognostic value in patients' overall survival rate were subsequently analyzed.

RESULTS

Immunohistochemical analysis revealed positive expression of ABCG2 and ABCB1 in 52.0% and 41.8% of patients, respectively. There was a positive correlation between ABCG2 expression and ABCB1 expression. The presence of these two proteins was significantly related to clinical stage, lymph node metastasis, and overall survival in LSCC. Interestingly, up-regulation of ABCG2 expression was found to be associated with increased proliferation, but that of ABCB1 was not. Up-regulation of both ABCG2 expression and ABCB1 expression was associated with decreased apoptosis.

CONCLUSIONS

The results of this study revealed that the presence of ABCG2 and/or ABCB1 is predictive for malignant progression and is an independent prognostic factor in LSCC. The mechanism of ABC transporters may contribute to chemotherapy resistance by promoting proliferation and/or suppressing apoptosis.

Expression and function of ABCG2 in head and neck squamous cell carcinoma and cell lines

Overexpression of breast cancer resistance protein, the ATP-binding cassette, subfamily G, member2 (BCRP/ABCG2), confers multidrug resistance to tumor cells and often limits the efficacy of chemotherapy. The aim of this study was to investigate the expression and functional activity of ABCG2 in head and neck squamous cell carcinoma (HNSCC) and corresponding cell lines. Immunohistochemistry was performed to investigate the presence of the ABCG2 transporter in HNSCC tissues. Expression of ABCG2 in the Hep-2, Hep-2T, CNE and FaDu cell lines was analyzed by real-time quantitative reverse transcription-polymerase chain reaction and Western blotting at the levels of messenger RNA (mRNA) and protein, respectively. The drug sensitivity of the above four cell lines to mitoxantrone was detected using MTT, and the drug accumulation of mitoxantrone was analyzed by flow cytometry. Positive expression of ABCG2 was detected in 52.04% of the laryngeal cancer samples from 98 patients, in 65% of the 40 hypopharyngeal cancer samples and in 58.82% of the 34 nasopharyngeal cancer samples. The level of expression was found to be correlated with tumor TNM stage (P<0.05) and lymph node metastasis (P<0.01). All four HNSCC cell lines expressed ABCG2 at the mRNA and protein levels. The levels of ABCG2 expression in the four cell lines were significantly correlated with the function and sensitivity to mitoxantrone. The addition of fumitremorgin C at a concentration of 5 μM to mitoxantrone treatment caused a varied increase in mitoxantrone accumulation of 1.09-fold, 1.33-fold (P<0.01), 1.4-fold (P<0.01) and 1-fold in the Hep-2, Hep-2T, CNE and FaDu cells, respectively. Expression of ABCG2 varied among the different types of carcinoma tissues and each HNSCC cell line, and it induced multidrug resistance and separation of cancer stem cells attributing to its efflux pump function. Thus, ABCG2 expression may be an unfavorable prognostic factor for HNSCC. Due to the negligible expression and function of ABCG2, we suggest that the FaDu cell line is suitable to be a negative control in studies involving HNSCC. Taken together, ABCG2 is a promising universal biomarker of cancer stem cells and a target gene for HNSCC chemotherapy.

Effect of apoptotic and proliferative indices, P-glycoprotein and survivin expression on prognosis in laryngeal squamous cell carcinoma

This study was to explore the relationship between P-glycoprotein and survivin expression with apoptotic index, proliferative index, clinicopathologic characteristics, and their prognostic value in laryngeal squamous cell carcinoma (LSCC). Samples from 86 patients with LSCC were analyzed for P-glycoprotein, survivin, and Ki-67 expression by immunohistochemistry and apoptotic index by the TUNEL method. The association of P-glycoprotein and survivin expression with clinicopathologic parameters, apoptotic and proliferative activities, and patients' overall survival was subsequently analyzed. We found that up-regulation of P-glycoprotein expression was associated with decreased apoptosis but not with changes in proliferation, whereas increased survivin expression was correlated with decreased apoptosis and increased proliferation. There was a positive correlation between P-glycoprotein and survivin expression. Expression of these two proteins was significantly related to the clinical stage, histological grade, lymph node metastasis, and overall survival in LSCC. These results reveal that survivin and P-glycoprotein may have an effect on chemotherapy resistance and progression of LSCC through promoting proliferation and/or suppressing apoptosis. Furthermore, our results demonstrate that P-glycoprotein and survivin proteins are both predictive of malignant progression and prognosis of LSCC.

Alteration in TWIST expression: possible role in paclitaxel-induced apoptosis in human laryngeal carcinoma Hep-2 cell line

AIM

To explore the relationship between alteration in the expression of TWIST, highly conserved transcription factor from the basic helix-loop-helix family, and apoptosis of Hep-2 cells induced by chemotherapeutic agent paclitaxel.

METHODS

Morphological changes of Hep-2 cells were observed by acridine orange cytochemistry staining. Viability of Hep-2 cells treated with various concentrations of paclitaxel was examined by cell proliferation assay. Apoptosis was examined by flow cytometry. The mRNA and protein expression of TWIST in response to paclitaxel at 24 hours, 48 hours, and 72 hours was examined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting, respectively.

RESULTS

Typical morphological changes of apoptotic cells at 24 hours, 48 hours, or 72 hours after treatment wiyth paclitaxel (10x10(-9) mol/L) were observed. The cell survival rates significantly decreased in a concentration- and time-dependent manner (P=0.001). Paclitaxel-induced apoptosis increased with culture time (22.6+/-5.3% after 24 hours, 38.7+/-7.9% after 48 hours, and 52.4+/-14.3% after 72 hours; P=0.002). Both mRNA and protein expression of TWIST was markedly decreased at both mRNA levels and protein levels, at 24 hours, 48 hours, and 72 hours in the paclitaxel-induced apoptosis of Hep-2 cells (P<0.001).

CONCLUSION

TWIST, which has a significantly decreased expression in response to paclitaxel in Hep-2 cells, may play a pivotal role in paclitaxel-induced apoptosis of Hep-2 cells.

MDR1/P-gp and VEGF synergistically enhance the invasion of Hep-2 cells with multidrug resistance induced by taxol

BACKGROUND

Tumor invasion/metastasis and multidrug resistance (MDR) are the main causes of treatment failure and high mortality in all kinds of cancer patients. The relationship between the two factors is still unclear. The aim of this study is to investigate the association between MDR and invasion, especially the role of multidrug resistance 1/P-glycoprotein (MDR1/P-gp) and vascular endothelial growth factor (VEGF) during the invasion.

METHODS

Multidrug resistance 1 (MDR1) and VEGF receptor 2 (VEGFR-2) were detected with real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) and Western blotting at the levels of messenger RNA (mRNA) and protein, respectively. RNA interference was applied to inhibit the expression of MDR1. The invasive assays were performed with the CHEMICON cell invasion assay kit.

RESULTS

The MDR cell line induced by Taxol (Hep-2T cell) was more invasive than its parent cell line (Hep-2 cell), which was at least in part mediated through the overexpressed MDR1/P-pg. MDR1-targeted RNA interference could effectively inhibit the expression of MDR1 and obviously decrease the invasive ability. Synergistic enhancing effects existed between MDR1/P-gp and VEGF on the invasion of Hep-2T cells. The expression of VEGFR-2 was elevated in Hep-2T cells. SU1498 could significantly decrease the invasion of Hep-2T cells. MDR1-targeted RNA interference and SU1498 had synergistic decreasing effect on the invasion of Hep-2T cells.

CONCLUSIONS

MDR1/P-pg may be a risk predictor for the invasion of laryngeal cancer. MDR1 knock down and VEGFR-2 inhibitor may be two promising treatment regiments for advanced laryngeal carcinoma patients with MDR and invasion/metastasis.

Increased p38-MAPK is responsible for chemotherapy resistance in human gastric cancer cells

Background

Chemoresistance is one of the main obstacles to successful cancer therapy and is frequently associated with Multidrug resistance (MDR). Many different mechanisms have been suggested to explain the development of an MDR phenotype in cancer cells. One of the most studied mechanisms is the overexpression of P-glycoprotein (P-gp), which is a product of the MDR1 gene. Tumor cells often acquire the drug-resistance phenotype due to upregulation of the MDR1 gene. Overexpression of MDR1 gene has often been reported in primary gastric adenocarcinoma.

Methods

This study investigated the role of p38-MAPK signal pathway in vincristine-resistant SGC7901/VCR cells. P-gp and MDR1 RNA were detected by Western blot analysis and RT-PCR amplification. Mitgen-activated protein kinases and function of P-gp were demonstrated by Western blot and FACS Aria cytometer analysis. Ap-1 activity and cell apoptosis were detected by Dual-Luciferase Reporter Assay and annexin V-PI dual staining.

Results

The vincristine-resistant SGC7901/VCR cells with increased expression of the multidrug-resistance 1 (MDR1) gene were resistant to P-gp-related drug and P-gp-unrelated drugs. Constitutive increases of phosphorylated p38-MAPK and AP-1 activities were also found in the drug-resistant cells. Inhibition of p38-MAPK by SB202190 reduced activator protein-1 (AP-1) activity and MDR1 expression levels and increased the sensitivity of SGC7901/VCR cells to chemotherapy.

Conclusion

Activation of the p38-MAPK pathway might be responsible for the modulation of P-glycoprotein-mediated and P-glycoprotein-unmediated multidrug resistance in the SGC7901/VCR cell line.