Expression of multidrug resistance-associated protein1,P-glycoprotein, and thymidylate synthase in gastric cancer patients treated with 5-fluorouracil and doxorubicin-based adjuvant chemotherapy after curative resection

Immunohistochemical expression of PD-L1 and MDR1 in breast tumors: association with clinico-pathological parameters and treatment outcome

Antitumor immune evasion is a hallmark for the development and progression of cancer. Tumor cells adopt various mechanisms to escape the host immune system recognition. One such mechanism is the over expression of programmed death ligand (PD-L1), a negative T cell regulatory molecule. Because PD-L1 overexpression causes resistance to chemotherapeutic response in many cancers, herein we explored the relationship between PD-L1 and multidrug resistance protein MDR1 in breast cancer. Immunohistochemical evaluation of PD-L1 and MDR1 proteins in 194 breast cancer tissue samples were carried out. The relationship between PD-L1 and MDR1 expression on cancer cells with clinicopathological factors and prognosis was investigated. IHC showed a significant correlation between PD-L1 and MDR1 expression on tumor cells. Increased PD-L1 expression was also associated with lymph node status and tumor grade of the patient. Our results also revealed that the expression of PD-L1 and MDR1 was higher in TNBC subtype compared to other breast cancer subtypes. Therefore, a better understanding of the molecular mechanism through which PD-1/PD-L1 pathway contribute to the chemoresistance might bring forth the prognostic significance of PD-L1 and selection of patients who may benefit from immunotherapy.

GM-CSF-miRNA-Jak2/Stat3 Signaling Mediates Chemotherapy-Induced Cancer Cell Stemness in Gastric Cancer

Chemotherapy serves as the first choice in clinic to treat advanced gastric cancer. However, emerging evidence indicated the induction of drug resistance and cancer stem cells occasionally by chemotherapy, which seriously limit the therapeutic effects, but the regulatory mechanism remains unclear. Here we treated two human gastric cancer cell lines SGC7901 and BGC823 with 5-Fluorouracil (5-Fu) or Cisplatin (DDP) in vitro. The survived cells showed significant increase of drug resistance, cell stemness and cytokine GM-CSF expression and secretion. As such, GM-CSF was applied to stimulate gastric cancer cells, followed by the subpopulation of CD133⁺ CSC analysis, sphere formation assay and stemness genes expression analysis. As a result, CSCs showed induction by GM-CSF treatment. A gastric cancer animal model further indicated that the gastric cancer cells significantly promoted tumor growth after GM-CSF treatment in vivo. High-throughput miRNA and mRNA sequencing analyses identified a subset of miRNAs and mRNAs under regulation of both 5-Fu and GM-CSF in gastric cancer cells, including upregulation of miR-877-3p and downregulation of SOCS2. Targeted overexpression or knockdown of miR-877-3p in gastric cancer cells revealed the oncogenic function of miR-877-3p in regulating gastric cancer by suppressing target gene SOCS2. Jak2/Stat3 signaling pathway, as a downstream target of SOCS2, showed activation in vitro and in vivo after treatment with miR-877-3p or GM-CSF. Our findings not only revealed a novel mechanism through which chemotherapy induced CSCs in gastric cancer via GM-CSF-miRNA-Jak2/Stat3 signaling, but also provided an experimental evidence for appropriate dose reduction of adjuvant chemotherapy in treatment of cancer patients.

Clinical significance and correlation of miR-200c and P-gp expression in gastric cancer and the effects on multidrug resistance

BACKGROUND

Poor prognosis is common in gastric cancer patients due to multidrug resistance (MDR)-induced recurrence and metastasis. In the present study, we investigated the expression of microRNA (miR)-200c in gastric cancer tissues and cell lines and its relationship with the expression of the drug resistant gene ABCB1, which encodes P-glycoprotein (P-gp).

METHODS

The basic characteristics of 102 patients with gastric cancer were reviewed. Real time-polymerase chain reaction (PCR), immunohistochemistry, and Western blot were employed to detect the expression levels of miR-200c and P-gp in gastric carcinoma tissues and cell lines. The correlation of miR-200c messenger RNA (mRNA) level with clinicopathological characteristics and P-gp protein expression were analyzed. SGC7901/vincristine (VCR) cells were transfected with miR-200c mimics or a specific small interfering RNA (siRNA) targeting the ABCB1 gene. The methyl thiazolyl tetrazolium (MTT) assay and flow cytometry were used to determine the role of miR-200c and ABCB1 on the viability and apoptosis of gastric carcinoma cell lines.

RESULTS

The level of miR-200c in carcinoma tissues was significantly lower than that in adjacent tissues, and the expression level of P-gp in carcinoma tissues was obviously higher than that in adjacent tissues (P<0.01, P=0.029). The expression levels of miR-200c and P-gp were associated with the malignant characteristics of gastric cancer, and patients with high expression of miR-200c or negative expression of P-gp had a better prognosis (P=0.006, P=0.022). MiR-200c negatively regulated the ABCB1 gene in gastric cancer cell lines. MiR-200c overexpression and ABCB1 down-regulation increased the sensitivity of SGC7901/VCR cells to VCR and reversed MDR by promoting cell apoptosis.

CONCLUSIONS

The expression level of miR-200c decreases in gastric carcinoma tissues and drug-resistant gastric cancer SGC7901/VCR cells. Overexpression of miR-200c may enhance the sensitivity of SGC7901/VCR cells to VCR by regulating the expression of P-gp.

Loganetin and 5-fluorouracil synergistically inhibit the carcinogenesis of gastric cancer cells via down-regulation of the Wnt/β-catenin pathway

Although most gastrointestinal tumours are sensitive to 5-fluorouracil (5FU), drug resistance is commonly occurred after 5FU therapy in gastric cancer (GC). Loganetin is the primary active compound in Cornus officinali. However, the synergetic effects of loganetin and 5FU on GC remain unknown. Here, we investigated the synergetic effects and the underlying mechanism of loganetin and 5FU on proliferation, stem-like properties, migration, and invasion of GC both in vitro and in vivo. We found that loganetin alone inhibited the proliferation, stem-like properties, migration and invasion of GC cells in vitro. Importantly, the loganetin remarkably enhanced the anti-cancer effect of 5FU on GC cells and the Wnt/β-catenin pathway might be involved in this process. Animal experiments further confirmed the synergistic effects of 5FU and loganetin on inhibiting cell growth and metastasis of GC. These results suggested that loganetin could synergistically increase the effect of 5FU against GC, which sheds light on effective combinational drug strategies for GC treatment.

Silencing of the ARK5 gene reverses the drug resistance of multidrug-resistant SGC7901/DDP gastric cancer cells

For several years, the multidrug resistance (MDR) of gastric cancer cells has been a thorny issue worldwide regarding the chemotherapy process and needs to be solved. Here, we report that the ARK5 gene could promote the multidrug resistance of gastric cancer cells in vitro and in vivo. In this study, LV-ARK5-RNAi lentivirus was used to transfect the parental cell line SGC7901 and MDR cell line SGC7901/DDP to construct a stable model of ARK5 interference. Subsequently, the cells were treated with four chemotherapeutic drugs, cisplatin (DDP), adriamycin (ADR), 5-fluorouracil (5-FU) and docetaxel (DR) and were subjected to the CCK8, colony formation, adriamycin accumulation and retention, cell apoptosis and other assays. The study found that, in vitro, the expression of ARK5 in MDR gastric cancer cells was significantly higher than that in parental cells. Additionally, when treated with different chemotherapeutic drugs, compared with parental cells, MDR cells also had a higher cell survival rate, higher colony formation number, higher drug pump rate, and lower cell apoptosis rate. Additionally, in xenograft mouse models, MDR cells with high ARK5 expression showed higher resistance to chemotherapeutic drugs than parental cells. Overall, this study revealed that silencing the ARK5 gene can effectively reverse the drug resistance of MDR gastric cancer cells to chemotherapeutic drugs, providing insights into the mechanism of this process related to its inhibition of the active pump-out ability of MDR cells.

miRNA-765 mediates multidrug resistance via targeting BATF2 in gastric cancer cells

Elucidation of the mechanisms underlying multidrug resistance (MDR) is required to ensure the efficacy of chemotherapy against gastric cancer (GC). To investigate this issue, here we identified that microRNA-765 (miRNA-765) is up-regulated both in MDR GC cell lines and in specimens from patients who are not responding to chemotherapy. In addition, down-regulation of miRNA-765 increased the sensitivity of GC cells to anticancer drugs, whereas its overexpression had the opposite effect. Moreover, miRNA-765 suppressed drug-induced apoptosis and positively regulated the expression of MDR-related genes. Finally, we showed that the basic leucine zipper ATF-like transcription factor 2, a tumor suppressor gene, is the functional target of miRNA-765. In summary, these results suggest that miRNA-765 may promote MDR via basic leucine zipper ATF-like transcription factor 2 in GC cells.

Adapting and Surviving: Intra and Extra-Cellular Remodeling in Drug-Resistant Gastric Cancer Cells

Despite the significant recent advances in clinical practice, gastric cancer (GC) represents a leading cause of cancer-related deaths in the world. In fact, occurrence of chemo-resistance still remains a daunting hindrance to effectiveness of the current approach to GC therapy. There is accumulating evidence that a plethora of cellular and molecular factors is implicated in drug-induced phenotypical switching of GC cells. Among them, epithelial-mesenchymal transition (EMT), autophagy, drug detoxification, DNA damage response and drug target alterations, have been reported as major determinants. Intriguingly, resistant GC phenotype may be the result of GC cell-induced tumor microenvironment (TME) remodeling, which is currently emerging as a key player in promoting drug resistance and overcoming cytotoxic effects of drugs. In this review, we discuss the possible mechanisms of drug resistance and their involvement in determining current GC therapies failure.

Inhibition of Polo-Like Kinase 1 by BI2536 Reverses the Multidrug Resistance of Human Hepatoma Cells In Vitro and In Vivo

BACKGROUND

Multi Drug Resistance (MDR) is the phenomenon that cancers develop resistance to majority of chemotherapy drugs and is a serious obstacle to the treatment for Hepatocellular Carcinoma (HCC). Polo-Like Kinase 1 (PLK1) is a serine/threonine kinase associated with tumor growth and clinical prognosis in HCC and BI2536 is its potent inhibitor with IC50 of 0.83nM.

AIMS

To test whether the down-regulation of PLK1 by its inhibitor BI2536 would have beneficial effects on the reversal of MDR in HCC cells.

METHODS

The CCK-8 assay was used to determine the viability of HepG2/ADM and SMMC7721/ADM cells and their parental cells treated with BI2536. Then animal model studies were performed. Cell invasion assay and wound healing assay were used to determine the invasion ability and motility. Flow cytometric was used to test the apoptosis induced by BI2536. Western blot and quantitative real-time PCR were performed to test the change of expression of MDR and apoptosis-related gene.

RESULTS

BI2536 down-regulated the expression of PLK1 protein and mRNA specifically. BI2536 can significantly reduce IC50 for ADM and other drugs in ADM-resistant HCC cells. Meanwhile, it inhibited cell viability, proliferation, and invasion, and induced cell cycle arrest and apoptosis in HCC cells with MDR.

CONCLUSION

Our results suggest that PLK1 inhibitor BI2536 can re-sensitize HCC cancer cell with MDR through induction of apoptosis. Thus, PLK1 inhibitor BI2536 may act as an effective chemotherapeutic drug in the clinical treatment of HCC patients with MDR.

Identification and validation of NOLC1 as a potential target for enhancing sensitivity in multidrug resistant non-small cell lung cancer cells

Adjuvant chemotherapy has become the frequently adopted standard therapeutic approach for non-small cell lung cancer (NSCLC). However, the development of multidrug resistance (MDR) is a major obstacle contributing to the failure of chemotherapy. This study aimed to identify genes associated with MDR development that predict tumor response to chemotherapy in NSCLC. In the present study, a multidrug-resistant NSCLC cell sub-line, A549/MDR, was established from the A549/DDP cell line and characterized. The resistance index (RI) of this subline was calculated according to the IC50 of A549/MDR relative to the parental A549/DDP cells. The gene expression profiles of A549/DDP and A549/MDR were obtained using an oligonucleotide microarray (Agilent SureHyb microarray chip). The microarray results were validated by qRT-PCR and selected genes were analyzed by in vitro loss-of-function experiments. Gene expression profiling identified 921 differentially expressed genes (DEGs) according to the selection criteria, in which 541 genes were upregulated and 380 genes were downregulated in A549/MDR compared with A549/DDP cells. We found that these DEGs are involved in diverse biological processes, including ribonucleoprotein complex, drug metabolism, the Hippo signaling pathway and transcriptional misregulation. NOLC1, as one of the identified DEGs, was confirmed to be overexpressed in A549/MDR cells and its knockdown significantly enhanced the drug sensitivity of A549/MDR cells in response to multidrug treatment. Furthermore, knockdown of NOLC1 downregulated the expression levels of drug resistance-associated molecules (LRP and MDR1) in A549/MDR cells. These findings provide a new and comprehensive expression profile of MDR in NSCLC cells. Identification and validation of NOLC1 might be a promising therapeutic strategy for the management of MDR of NSCLC patients.

Doxorubicin combined with Notch1-targeting siRNA for the treatment of gastric cancer

Notch1, a transmembrane receptor that has a notable role in gastric cancer (GC) as an oncogene, has been reported to be involved in doxorubicin resistance. Thus, Notch1 is a potential therapeutic target for GC. In the present study, the protein levels of Notch1 intracellular domain (NICD; a marker of Notch1 activation) in human GC cell lines and tumor tissues was measured by western blotting. Next, the effects of Notch1 depletion in SGC7901 cells were evaluated. Finally, the efficacy of Notch1 small interfering RNA (siRNA) combined with doxorubicin therapy for GC was examined in vitro and in vivo. The results revealed that NICD levels were high in GC cells, and that the inhibition of NICD by transfection with Notch1 siRNA induced apoptosis and inhibited proliferation. Ectopic downregulation of Notch1 expression enhanced the sensitivity of GC tumors to doxorubicin, which suppressed the development of GC. These data demonstrated that Notch1 was a significant regulator of cell proliferation and apoptosis in GC. Thus, the combination of doxorubicin with Notch1 siRNA is a potential strategy for the treatment of GC.

miR-30 decreases multidrug resistance in human gastric cancer cells by modulating cell autophagy

Chemotherapy is an important treatment modality for gastric cancer, and multidrug resistance (MDR) represents a major obstacle for successful cancer chemotherapy. There is a lack of research on whether microRNA (miR)-30a regulation affects the chemosensitivity of resistant gastric cancer cells, and mechanisms underlying the effects of miR-30a on drug resistance and cell autophagy require further investigation. In the present study, the expression of miR-30a and its effects in cisplatin (CDDP)-resistant human gastric cancer cells were investigated. A CDDP-resistant variant of the SGC-7901 cell line (SGC-7901/CDDP) was established by exposing the cells to gradually increasing drug concentrations, and miR-30a expression was detected by reverse transcription-semi quantitative polymerase chain reaction (RT-sqPCR). To examine the effect of miR-30a expression in the SGC-7901/CDDP cells, miR30a mimics or negative control miRNA were transfected into the cells, and a Cell Counting Kit-8 assay was performed to analyze the chemosensitivity of the different cell groups. RT-sqPCR and western blot analysis were also used to measure MDR1 mRNA and P-glycoprotein expression, and the light chain (LC)3-II/LC3-I ratio. Furthermore, apoptosis induced by the chemotherapeutic CDDP in the different groups was assessed using flow cytometry. The results demonstrated that low expression of miR-30a was associated with chemoresistance in gastric cancer cells, and in the chemoresistant cell line SGC7901/CDDP, CDDP-induced apoptosis was weakened. Additionally, it was demonstrated that the LC3-II/LC3-I ratio was elevated in SGC7901/CDDP cells compared with chemosensitive SGC7901 cells (P<0.001), which could be attenuated by upregulating miR-30a expression (P<0.001 vs. SGC7901/CDDP control cells). These results suggested that autophagy may contribute to drug resistance in gastric cancer cells, and that the reduction of LC3-II in response to miR-30a overexpression may inhibit chemoresistance-associated autophagy in gastric cancer cells.

FBXW7 expression is associated with prognosis and chemotherapeutic outcome in Chinese patients with gastric adenocarcinoma

Background

FBXW7, a component of the Skp-Cullin1-F-box, mediates target protein recognition. It is a tumor suppressor gene that plays a role in the regulation of cell cycle exit and reentry via c-Myc, c-Jun and Notch degradation. There are few studies, particularly involving a large patient cohort, that have evaluated FBXW7 during gastric cancer progression.

Methods

Our study aimed to evaluate the value of FBXW7 as a clinical marker in gastric adenocarcinoma (GC) patients including a subset treated with postoperative chemotherapy. Quantitative reverse transcription PCR (qRT-PCR) assay was used to measure FBXW7 transcript levels in tumors paired with normal gastric tissue in 24 gastric adenocarcinoma patients. Subsequently, 546 additional GC samples were evaluated from patients that underwent radical gastrectomy, including 118 early stage cases(Stage I) and 428 advanced stage cases (Stages II or III). Amongst the advanced stage patient cases evaluated, 347 received postoperative adjuvant chemotherapy. All 546 gastric adenocarcinoma cases were then evaluated by tissue microarray and immunohistochemistry (IHC) for FBXW7 expression. Clinicopathological features and diagnoses were confirmed by histopathologic evaluation and review of clinical data. Overall survival (OS) was then evaluated in the 546 gastric cancer patients.

Results

By immunohistologic evaluation, low expression of FBXW7 in primary gastric cancer significantly correlated with poor differentiation of tumor cells. Moreover, low FBXW7 expression was associated with worse survival as well as worse adjuvant chemotherapy response.

Conclusion

Our findings suggest that FBXW7 may serve as an important predictor in chemotherapeutic responses.

MiR-129 regulates cisplatin-resistance in human gastric cancer cells by targeting P-gp

Development of multiple drug resistance (MDR) to chemotherapy is the major reason for the failure of gastric cancer (GC) treatment. P-glycoprotein (P-gp), which is encoded by MDR gene 1, as one of the mechanisms responsible for MDR. Mounting evidence has demonstrated that the drug-induced dysregulation of microRNAs (miRNAs) function may mediate MDR in cancer cells. However, the underling mechanisms of miRNA-mediated MDR in GC remain unclear. Here, we found that miR-129 was downregulated in cisplatin-resistant GC tissues/cells. Our results also showed that overexpression of miR-129 decreased cisplatin-resistance in cisplatin-resistant GC cells, and miR-129 knockdown reduced chemosensitivity to cisplatin in cisplatin-sensitive GC cells. Furthermore, miR-129 activated the intrinsic apoptotic pathway via upregulating caspase-9 and caspase-3. Most importantly, we further confirmed that P-gp is the functional target of miR-129 by regulating cisplatin-resistance in GC cells. These results suggested that miR-129 reversed cisplatin-resistance through inhibiting the P-gp expression in GC cells.

Annosquacin B induces mitochondrial apoptosis in multidrug resistant human breast cancer cell line MCF-7/ADR through selectively modulating MAPKs pathways

CONTEXT

Multidrug resistance (MDR) is a major obstacle to efficient therapy of cancers. It is a prime concern for researchers to find compounds with anti-proliferative activity on MDR cell lines. In recent years, annonaceous acetogenins (ACGs) were reported to have anti-proliferative activity. However, the underlying mechanisms are still unknown.

OBJECTIVE

This study determines the mechanisms of anti-proliferative activity induced by Annosquacin B (AB) against MCF-7/ADR cells.

MATERIAL AND METHODS

The cytotoxicity of AB at varying concentrations (0.64, 1.6, 4, 10, 25, 62.5, 156.25 μM) on MCF-7/ADR cells was assessed using the MTT assay. Annexin V-FITC/propidium iodide staining and Acrinidine orange and ethidium bromide (AO/EB) staining were employed to investigate whether AB (14, 7, 3.5 μM) could induce apoptosis in MCF-7/ADR cells. Levels of caspase-3 and caspase-9, Bax, Bcl-2 and MAPKs kinases were evaluated by western blot assay following treatment with various concentrations of AB (3.5, 7, 14 μM) at different time points (0, 0.5, 1, 2, 4, 8, 12 h).

RESULTS AND CONCLUSION

MTT assay showed that AB significantly decreased cell viability on MCF-7/ADR (IC₅₀ of 14.69 μM). AB-induced apoptosis in MCF-7/ADR cells through mitochondrial apoptosis pathways. It induced typical apoptosis by morphologic changes; elevate levels of caspase-3, caspase-9 as well as the ratio of Bax/Bcl-2. In addition, AB increased the expression of p-p38 MAPK and decreased the expression of p-JNK, while whether ERK1/2 had an effect on the MCF-7/ADR apoptosis remains to be determined.

Molecular mechanisms of chemoresistance in gastric cancer

Gastric cancer is the fourth most common cancer and the second leading cause of cancer deaths worldwide. Chemotherapy is one of the major treatments for gastric cancer, but drug resistance limits the effectiveness of chemotherapy, which results in treatment failure. Resistance to chemotherapy can be present intrinsically before the administration of chemotherapy or it can develop during chemotherapy. The mechanisms of chemotherapy resistance in gastric cancer are complex and multifactorial. A variety of factors have been demonstrated to be involved in chemoresistance, including the reduced intracellular concentrations of drugs, alterations in drug targets, the dysregulation of cell survival and death signaling pathways, and interactions between cancer cells and the tumor microenvironment. This review focuses on the molecular mechanisms of chemoresistance in gastric cancer and on recent studies that have sought to overcome the underlying mechanisms of chemoresistance.

Association of thymidylate synthase expression and clinical outcomes of gastric cancer patients treated with fluoropyrimidine-based chemotherapy: a meta-analysis

PURPOSE

Although several studies have suggested an association between thymidylate synthase (TS) expression and outcomes of gastric cancer (GC) patients treated with fluoropyrimidine-based chemotherapy (FUC), the predictive value of TS for response and survival in this setting is unclear. This meta-analysis aimed to estimate prognostic and predictive significance of TS more precisely.

METHODS

We searched PubMed, Embase, Cochrane Library, and Web of Science databases for literature published up to June 2015. Primary outcomes included hazard ratios (HRs) for overall survival (OS), and event-free survival (EFS) and odds ratio (OR) for chemotherapy response. Fixed- or random-effects models were used to calculate pooled HR and OR according to heterogeneity.

RESULTS

A total of 2,442 GC patients in 25 studies met our inclusion criteria. Response rates for FUC were significantly lower in patients with high TS expression than in those with low expression (OR: 0.43, 95% confidence interval [CI]: 0.22-0.84, P=0.013). High TS expression was significantly correlated with unfavorable OS (HR: 1.62, 95% CI: 1.28-2.05, P<0.001) and EFS (HR: 1.54, 95% CI: 1.22-1.93, P<0.001) in advanced disease. However, TS expression was not significantly related to OS (HR: 1.06, 95% CI: 0.74-1.50, P=0.760) or EFS (HR: 1.16, 95% CI: 0.84-1.61, P=0.374) in the adjuvant setting.

CONCLUSION

Higher TS expression might predict drug resistance and adverse prognosis in patients with advanced GC treated with FUC.

The potential predictive role of nuclear NHERF1 expression in advanced gastric cancer patients treated with epirubicin/oxaliplatin/capecitabine first line chemotherapy

Cellular resistance in advanced gastric cancer (GC) might be related to function of multidrug resistance (MDR) proteins. The adaptor protein NHERF1 (Na(+)/H(+) exchanger regulatory factor) is an important player in cancer progression for a number of solid malignancies, even if its role to develop drug resistance remains uncertain. Herein, we aimed to analyze the potential association between NHERF1 expression and P-gp, sorcin and HIF-1α MDR-related proteins in advanced GC patients treated with epirubicin/oxaliplatin/capecitabine (EOX) chemotherapy regimen, and its relation to response. Total number of 28 untreated patients were included into the study. Expression and subcellular localization of all proteins were assessed by immunohistochemistry on formalin-fixed paraffin embedded tumor samples. We did not found significant association between NHERF1 expression and the MDR-related proteins. A trend was observed between positive cytoplasmic NHERF1 (cNHERF1) expression and negative nuclear HIF-1α (nHIF-1α) expression (68.8% versus 31.3% respectively, P = 0.054). However, cytoplasmic P-gp (cP-gp) expression was positively correlated with both cHIF-1α and sorcin expression (P = 0.011; P = 0.002, respectively). Interestingly, nuclear NHERF1 (nNHERF1) staining was statistically associated with clinical response. In detail, 66.7% of patients with high nNHERF1 expression had a disease control rate, while 84.6% of subjects with negative nuclear expression of the protein showed progressive disease (P = 0.009). Multivariate analysis confirmed a significant correlation between nNHERF1 and clinical response (OR 0.06, P = 0.019). These results suggest that nuclear NHERF1 could be related to resistance to the EOX regimen in advanced GC patients, identifying this marker as a possible independent predictive factor.

The impact of insulin on chemotherapeutic sensitivity to 5-fluorouracil in gastric cancer cell lines SGC7901, MKN45 and MKN28

Background

The role of insulin in the pathogenesis of cancer has been increasingly emphasized because of the high incidence of obesity and metabolic syndrome and their correlated complication including cancer. This study aimed to explore the impact of insulin on chemoresistance to 5-fluorouracil in gastric cancer and the possible mechanisms.

Methods

Tissue samples of gastric cancer and adjacent normal gastric mucosa from patients with or without obesity were performed immunohistochemical staining for P-glycoprotein. The follow-up was done after the surgical treatment. The effect of insulin on chemotherapeutic sensitivity of the three gastric cancer cell lines to 5-fluorouracil was evaluated by pre-incubation with insulin before administration of 5-fluorouracil. The expression of P-glycoprotein was determined by Western blotting.

Results

P-glycoprotein were overexpressed in tissues from patients who suffered gastric cancer and were higher in those simultaneously suffered gastric cancer and obesity. Addition of 1 μM insulin remarkably promoted the proliferation of SGC7901, MKN45 and MKN28 cells and decreased the cytotoxicity of 5-fluorouracil. In addition, the expression of P-glycoprotein was upregulated in SGC7901, MKN45 and MKN28 cells.

Conclusion

Insulin improved the proliferation of gastric cancer cell lines and contributed to chemoresistance of gastric cancer cells to 5-fluorouracil which is likely to involve upregulation of P-glycoprotein.

Association between ABCB1 immunohistochemical expression and overall survival in gastric cancer patients

Gastric cancer (GC) is one of the most common malignancies worldwide. The ABCB1 protein, a member of the ATP-binding cassette (ABC) transporter family, encoded by the ABCB1 gene, considerably influences the distribution of drugs across cell membranes as well as multidrug resistance (MDR) of antineoplastic drugs. In contrast to the extensive knowledge on the pharmacological action of ABCB1 protein, the correlation between the clinical-pathological data and ABCB1 protein expression in patients with GC remains unclear. The aim was to investigate association between ABCB1 expression and overall survival in GC patients. Human tumor fragments from 57 GC patients were examined by immunohistochemistry assay. We observed lower survival rate of patients with GC who were positive for ABCB1 expression (p=0.030). Based on these observations, we conclude that GC patients with positive ABCB1 protein immunohistochemical expression in their tumors suffer shorter overall survival.

Role of ABC transporters in fluoropyrimidine-based chemotherapy response

Since over 50 years, 5-fluorouracil (5-FU) is in use as backbone of chemotherapy treatment regimens for a wide range of cancers including colon, breast, and head and neck carcinomas. However, drug resistance and severe toxicities such as mucositis, diarrhea, neutropenia, and vomiting in up to 40% of treated patients often lead to dose limitation or treatment discontinuation. Because the oral bioavailability of 5-FU is unpredictable and highly variable, 5-FU is commonly administered intravenously. To overcome medical complications and inconvenience associated with intravenous administration, the oral prodrugs capecitabine and tegafur have been developed. Both fluoropyrimidines are metabolically converted intracellularly to 5-FU, which then needs metabolic activation to exert its damaging activity on RNA and DNA. The low response rates of 10-15% of 5-FU monotherapy can be improved by combination regimens of infusional 5-FU and leucovorin together with oxaliplatin (FOLFOX) or irinotecan (FOLFIRI), thereby increasing response rates to 30-40%. The impact of metabolizing enzymes in the development of fluoropyrimidine toxicity and resistance has been studied in great detail. In addition, membrane drug transporters, which are critical determinants of intracellular drug concentrations, may play a role in occurrence of toxicity and development of resistance against fluoropyrimidine-based therapy as well. This review therefore summarizes current knowledge on the role of drug transporters with particular focus on ATP-binding cassette transporters in fluoropyrimidine-based chemotherapy response.

Synergistic antitumor activities of docetaxel and octreotide associated with apoptotic-upregulation in castration-resistant prostate cancer

Androgen deprivation therapy has become the fist-line treatment of metastatic prostate cancer; however, progression to castrate resistance disease occurs in the majority of patients. Thus, there is an urgent need for improvements in therapy for castration-resistant prostate cancer. The aims of the present study were to determine the efficacy somatostatin analogue octreotide (OCT) combined with a low dose of docetaxel (DTX) using castration resistant prostate cancer cells and to investigate the involved molecular mechanisms in vitro. The anti-proliferative and synergism potential effects were determined by MTT assay. Induction of apoptosis was analyzed employing annexing V and propidium iodide staining and flow cytometry. VEGFA, CASP9, CASP3 and ABCB1 gene expression was evaluated by RT-PCR and Q-RT-PCR analysis. OCT in combination with DTX treatments on DU145 cell migration was also evaluated. Investigation revealed that combined administration of DTX and OCT had significant, synergistically greater cytotoxicity than DTX or OCT treatment alone. The combination of the two drugs caused a more marked increase in apoptosis and resulted in greater suppression of invasive potential than either individual agent. There was obvious increase in caspase 3 expression in the OCT alone and two-drug combined treatment groups, however, VEGFA expression was markedly suppressed in them. These results support the conclusion that somatostatin analogues combined with docetaxel may enhance the chemotherapy efficacies through multiple mechanisms in castration-resistant PCa cell line. This work provides a preclinical rationale for the therapeutic strategies to improve the treatment in castrate resistance disease.

Anti-tumor activity of the X-linked inhibitor of apoptosis (XIAP) inhibitor embelin in gastric cancer cells

This study investigated the anticancer effects of embelin in human gastric cancer cells and the underlying molecular mechanisms. Gastric cancer cells were treated with embelin and 5-FU for methyl-thiazolyl-tetrazolium bromide cell viability assay and flow cytometric detection of cell viability and apoptosis. Protein pathway array (PPA) and Western blot were used to investigate differentially expressed proteins in embelin-treated gastric cancer cells. Embelin reduced gastric cancer cell viability, induced apoptosis, and enhanced 5-FU antitumor activity in gastric cancer cells. Mechanistically, embelin induced cell cycle arrest at the S and G2/M phases. Molecularly, embelin downregulated expression of X-linked inhibitor of apoptosis and cell cycle-regulatory proteins, such as CDK1, CDC25B, CDC25C, cyclinB1, and CDK2. PPA analysis showed that embelin modulated several pathways that are associated with cell growth and apoptosis, such as PI3K/AKT, JAK/STAT, p38 MAPK, and p53. The data from the current study implied that reduction of gastric cancer cell viability after treatment with embelin was through cell cycle arrest at the S and G2/M phases and apoptosis.

Adenovirus-mediated IL-24 expression enhances the chemosensitivity of multidrug-resistantgastric cancer cells to cisplatin

Chemotherapy is one of the commonly used strategies in gastric cancer, especially for unresectable patients, but it becomes insensitive to repeated administration of even the most effective chemotherapeutic agents, such as cisplatin. Given this, there is an urgent need for developing chemosensitizers to overcome acquired resistance to chemotherapeutic agents. Interleukin-24 (IL-24), a cytokine-tumor suppressor, shows broad-spectrum and tumor-specific antitumor properties, and studies have demonstrated that IL-24 could conspicuously restore the chemosensitivity of MDR cancer cells. Herein, we developed a human MDR gastric cancer cell subline, SGC7901/CDDP, by repeated selection of resistant clones of parental sensitive cells, and further investigated the chemosensitizing effects and the underlying mechanisms of adenovirus-mediated IL-24 (Ad-IL-24) gene therapy plus CDDP for the human MDR gastric cancer cells SGC7901/CDDP in vitro and in vivo. The results demonstrated that the expression of IL-24 mRNA and protein was profoundly downregulated in SGC7901/CDDP cells by RT-PCR and western blot analysis. In addition, the cell viability assay showed that the IC50 of SGC7901/CDDP cells to CDDP, 5-FU, ADM and MTX was significantly enhanced compared to parental sensitive SGC7901 cells. Ad-IL-24-induced IL-24 overexpression decreased the IC50 of the above agents (not MTX), induced G2/M cell cycle arrest, and Ad-IL-24 plus CDDP elicited significant apoptosis and tumor suppression of SGC7901/CDDP cells in vitro and SGC7901/CDDP cell xenograft tumors in vivo, respectively. Moreover, our results demonstrated that the mechanisms of Ad-IL-24-elicited chemosensitizing effects were closely associated with a substantial upregulation of Bax and downregulation of P-gp and Bcl-2 in SGC7901/CDDP cells in vitro and SGC7901/CDDP xenograft tissues in vivo. Thus, this study indicates that overexpression of IL-24 gene can significantly promote chemosensitivity in MDR phenotype SGC7901/CDDP gastric cancer cells.

MicroRNA-19a/b regulates multidrug resistance in human gastric cancer cells by targeting PTEN

Multidrug resistance (MDR) is the major cause of failure of gastric cancer chemotherapy. Members of the miR-17-92 cluster, including miR-19a/b, are considered oncomiRs and influence multiple aspects of the malignant phenotype of gastric cancer. However, the role of miR-19a/b in MDR in gastric cancer and its underlying mechanism remain unclear. In this study, we found that miR-19a/b were upregulated in MDR cell lines. Our results also showed that miR-19a/b upregulation decreased the sensitivity of gastric cancer cells to anticancer drugs. We further confirmed that miR-19a/b accelerated the ADR efflux of gastric cancer cells by increasing the levels of mdr1 and P-gp and that miR-19a/b suppressed drug-induced apoptosis by regulating Bcl-2 and Bax. Finally, we verified that PTEN, an inhibitor of AKT phosphorylation, is the functional target of miR-19a/b. Overall, these findings demonstrated that miR-19a/b promote MDR in gastric cancer cells by targeting PTEN.

Helicobacter pylori infection as an independent prognostic factor for locally advanced gastric cancer patients treated with adjuvant chemotherapy after curative resection

A few studies reported the association between negative Helicobacter pylori infection and poor clinical outcome in resected gastric cancer patients. We investigated the H. pylori infection status and its association with the clinical outcome in 274 locally advanced gastric cancer patients (American Joint Committee on Cancer stage IB: 25, II: 82, IIIA: 80, IIIB: 39 and IV: 48) who underwent adjuvant chemotherapy after curative resection (≥ D2 dissection). H. pylori infection status in hematoxylin and eosin stained corporal and antral mucosa of non-tumor tissue was graded according to the updated Sydney System and categorized as H. pylori negative (normal or mild infection) and H. pylori positive (moderate or marked infection). Eighty-one patients received 5-fluorouracil (5-FU) and doxorubicin-based chemotherapy, while 193 patients underwent 5-FU, mitomycin-C and polysaccharide-K chemotherapy. The median follow-up duration of survivors was 144 (120-184) months. In univariate analysis, patients with H. pylori negative status (108 patients) demonstrated significantly poor 10-year overall survival (OS) compared to those with H. pylori-positive status (166 patients; 21.3% vs. 71.1%, p < 0.0001). H. pylori negative status was associated with poor outcome in all stages except stage IIIB. In multivariate analysis, H. pylori-negative status was the most significant independent prognostic factor of poor OS (hazard ratio: 3.45, 95% confidence interval: 2.43-4.89, p < 0.0001) followed by old age (>54 years, p < 0.0001), advanced stage (stage III or IV, p = 0.001), and Borrmann type IV (p = 0.027). H. pylori infection status seems to have strong prognostic significance in locally advanced gastric cancer. H. pylori-negative patients may need careful follow-up after curative resection.

New insights into the mechanisms of gastric cancer multidrug resistance and future perspectives

Gastric cancer is still the second leading cause of cancer death worldwide. Chemotherapy is one of the major treatment options for advanced gastric cancer. The efficacy of chemotherapy for gastric cancer is poor due to insensitivity and the development of multidrug resistance (MDR). Gastric cancer MDR involves a large number of molecules and complex mechanisms. Classical drug-resistant molecules, such as P-glycoprotein/ABCB1 and MRP1/ABCC1, have been found to play important roles in mediating MDR in some gastric cancers. In recent years, new molecules and mechanisms have been found to be associated with the development of gastric cancer MDR and might provide new targets for tackling gastric cancer MDR. Combined use of molecularly targeted therapy with chemotherapy may offer improved outcomes for gastric cancer patients and might provide new threads of hope for gastric cancer treatment.

Comparison of the multi-drug resistant human hepatocellular carcinoma cell line Bel-7402/ADM model established by three methods

Background

To compare the biological characteristics of three types of human hepatocellular carcinoma multi-drug resistant cell sub-lines Bel-7402/ADM models established by three methods.

Methods

Established human hepatocellular carcinoma adriamycin (ADM) multi-drug resistant cell sub-lines models Bel-7402/ADM_V, Bel-7402/ADM_L and Bel-7402/ADM_S by three methods of in vitro concentration gradient increased induction, nude mice liver-implanted induction and subcutaneous-implanted induction respectively. Phase contrast microscopy was used to observe the cells and the MTT (methyl thiazolyl tetrazolium) method was used to detect drug resistance of the three different sub-lines of cells.

Results

The three groups of drug resistant cells, Bel-7402/ADM_V, Bel-7402/ADM_L and Bel-7402/ADM_S generated cross-resistance to ADM and CDDP (cis-Diaminedichloroplatinum), but showed a significant difference in resistance to Bel-7402 IC₅₀ value (P < 0.01). The doubling times were significantly extended compared to the parent cell line (39 h) and were 65 h (Bel-7402/ADM_V), 46 h (Bel-7402/ADM_L), and 45 h (Bel-7402/ADM_S). The excretion rates of ADM were significantly increased compared with the parent cell (34.14%) line and were 81.06% (Bel-7402/ADM_V), 66.56% (Bel-7402/ADM_L) and 61.56% (Bel-7402/ADM_S). Expression of P-gp and MRP in the three groups of resistant cells was significantly enhanced (P < 0.01). There was no significant variation in the expression of GSH/GST (P > 0.05).

Conclusions

Stable resistance was involved in the resistant cell line model established by the above three methods. Liver implantation was a good simulation of human hepatocellular and proved to be an ideal model with characteristics similar to human hepatocellular biology and the pharmacokinetics of anticancer drugs.

CpG hypomethylation of MDR1 gene in tumor and serum of invasive ductal breast carcinoma patients

OBJECTIVES

Multidrug resistance 1 (MDR1) gene encodes P-glycoprotein (P-gp), a transmembrane calcium-dependent efflux pump, implicated in drug resistance. In this prospective study, methylation status of MDR1 promoter and its correlation with clinicopathological parameters were evaluated in tumor and serum of breast cancer patients.

DESIGN AND METHODS

Methylation-specific PCR was carried out to investigate the promoter methylation status of MDR1 in tumor and serum of 100 patients with invasive ductal carcinomas of breast (IDCs). The effect of promoter methylation on protein expression was evaluated by immunohistochemistry.

RESULTS

MDR1 was hypomethylated in 47% tumors and 44% paired sera of IDC patients and correlated significantly with increased tumor size and advanced tumor stage. Promoter hypomethylation of MDR1 in serum DNA showed 98% specificity and 50% sensitivity.

CONCLUSIONS

Hypomethylation of MDR1 promoter in IDCs accounted for P-gp overexpression and aggressive biologic behavior in a subset of patients. Detection of these epigenetic changes in circulating DNA may not only enhance insight into the biological behavior of the primary tumor of an individual but may also provide valuable information regarding prognosis that can be readily monitored throughout the disease course.

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.

Expression of P-glycoprotein and its significance in metastatic lymph nodes and primary lesions of gastric carcinoma

AIM: To explore the different levels of P-glycoprotein (P-gp) expression in metastatic lymph nodes and primary lesions of gastric carcinoma and its relation with the biological behaviors of gastric cancer.

METHODS: Tissue specimens from 19 cases of gastric carcinoma with lymph node metastases were collected. The expression of P-gp was examined by immunohistochemistry in tissues of metastatic lymph nodes, primary lesions and normal gastric mucosa.

RESULTS: P-gp expression in metastatic lymph nodes was higher than that in the primary cancers (84.20% vs 52.63%, P < 0.05). The expression of P-gp in lymph node metastastic tissues had no significant association with the sex and age of patients, gastric carcinoma differentiation and infiltration, but P-gp expression in primary tumors was markedly associated with cancer differentiation degree and infiltration depth (P < 0.05). The positive rate of P-gp expression in patients without serosal invasion or with high and moderate differention was higher than that in those with serosal invasion or with low differentiation (P < 0.05).

CONCLUSION: P-gp expression in metastatic lymph nodes is higher than that in primary gastric cancers. The relation of P-gp expression with the biological behaviors is different between metastatic lymph nodes and primary lesions of gastric cancer.

Calebin-A induces apoptosis and modulates MAPK family activity in drug resistant human gastric cancer cells

This study is the first to investigate Calebin-A, a natural compound present in Curcuma longa, which inhibits cell growth and induce apoptosis in SGC7901/VINCRISTINE cells, a multidrug resistant (MDR) human gastric adenocarcinoma cell line. Our data suggest the drug efflux function of P-glycoprotein was inhibited by Calebin-A treatment, while the expression level of P-glycoprotein was not affected. Additionally, co-treatment of Calebin-A and vincristine resulted in a remarkable reduction in S phase and G2/M phase arrest in SGC7901/VINCRISTINE cells. Calebin-A was also found to modulate the activities of mitogen-activated protein kinase (MAPK) family members, which includes decreased c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and increased protein kinase of 38 kDa (p38) activity. These results suggest that Calebin-A might be an effective compound for the treatment of human gastric and other MDR cancers.

Effects of celecoxib on the reversal of multidrug resistance in human gastric carcinoma by downregulation of the expression and activity of P-glycoprotein

We investigated the effects of celecoxib on the cell proliferation and the expression and activity of P-glycoprotein in the human gastric carcinoma multidrug resistance sublines SGC7901/adriamycin and SGC7901/vincristine. The cell proliferation was measured by [3H]thymidine incorporation assay and MTT test. The expression of the multidrug resistant gene (MDR1) was detected by real-time quantitative reverse transcription-polymerase chain reaction. P-glycoprotein was measured by Western blot analysis. The intracellular rhodamine 123 accumulation was analyzed by flow cytometry to evaluate the activity of P-glycoprotein. After treatment with celecoxib, the proliferation inhibitions of SGC7901 cell line and the SGC7901/adriamycin and SGC7901/vincristine sublines increased linearly in a positive dose-dependent pattern in both the [3H]thymidine incorporation assay and in the MTT test. The IC50 value of the MDR1/GAPDH ratio was 5.50 x 10(-6) mol/l in SGC7901/adriamycin and 3.89 x 10(-6) mol/l in SGC7901/vincristine. P-glycoprotein expression levels in the two multidrug resistance sublines treated with celecoxib were significantly lower than those in control groups, 0.28 vs. 0.71 in the SGC7901/adriamycin subline and 0.21 vs. 0.83 in the SGC7901/vincristine subline, respectively, P<0.05. After treatment with celecoxib, intracellular rhodamine 123 accumulation in the SGC7901/adriamycin and SGC7901/vincristine sublines increased positively in a dose-dependent pattern (P<0.05), and reached more than 50% of that in the SGC7901 cell line at the concentration of 1 x 10(-4) mol/l of celecoxib. In conclusion, celecoxib could inhibit proliferation of multidrug resistance in gastric carcinoma sublines. The reversal of multidrug resistance was caused by downregulation of the expression and activity of P-glycoprotein. The results may suggest a new way to reverse P-glycoprotein-dependent multidrug resistance in human gastric carcinoma.

Multidrug resistance in gastric cancer: recent research advances and ongoing therapeutic challenges

Gastric cancer is the second leading cause of cancer mortality worldwide. The major cause of treatment failure for gastric cancer is the development of multidrug resistance (MDR) to chemotherapy, which is currently one of the primary treatment options. Recently, research into the MDR of gastric cancer has revealed that, in addition to the classical ATP-binding cassette transporters, such as P-glycoprotein (P-gp) and MDR-associated protein (MRP)1, a number of other molecules might mediate the drug resistance of human gastric cancer. The absence of P-gp and MRP1 expression in some gastric cancer cases also indicates that there might be other mechanisms responsible for human gastric cancer MDR. These molecules belong to different functional families and might work together to confer MDR phenotypes. The new findings may provide new clues to the mechanisms of MDR and enable the selection of new candidates for targeting MDR in human gastric cancer.

DeltaNp73alpha regulates MDR1 expression by inhibiting p53 function

The p73 protein is a transcription factor and member of the p53 protein family that expresses as a complex variety of isoforms. DeltaNp73alpha is an N-terminally truncated isoform of p73. We found that DeltaNp73 protein is upregulated in human gastric carcinoma suggesting that DeltaNp73 may play an oncogenic role in these tumors. Although it has been shown that DeltaNp73alpha inhibits apoptosis and counteracts the effect of chemotherapeutic drugs, the underlying mechanism by which this p73 isoform contributes to chemotherapeutic drug response remains to be explored. We found that DeltaNp73alpha upregulates MDR1 mRNA and p-glycoprotein (p-gp), which is involved in chemotherapeutic drug transport. This p-gp upregulation was accompanied by increased p-gp functional activity in gastric cancer cells. Our data suggest that upregulation of MDR1 by DeltaNp73alpha is mediated by interaction with p53 at the MDR1 promoter.

Expression and significance of multidrug resistance-associated protein-1 in gastric carcinoma

AIM: To explore the expression of multidrug resistance-associated protein 1 (MRP-1) in gastric carcinoma and its significance.

METHODS: The expression of MRP-1 were detected by immunohistochemistry (SP method) in 30 cases of chronic superficial gastritis (CSG), 30 cases of gastric intestinal metaplasia (IM), 45 cases of dysplasia (Dys) and 65 cases of gastric carcinoma (GC). Reverse transcription-polymerase chain reaction (RT-PCR) was used to examine the expression of MRP-1 mRNA. The comparison between mean values and rates was performed by t test and χ² test, respectively, and the relativity between two factors was evaluated by linear relative analysis.

RESULTS: The expression of MRP-1 showed a gradually increasing tendency as the disease progressed from CSG, IM, Dys to GC, and there was significant difference between GC and Dys as well as IM (43/65 vs 19/45, 6/30, P < 0.05). The protein and mRNA expression of MRP-1 in gastric carcinoma were significantly higher than those in the corresponding cancer adjacent tissues (66.2% vs 33.3%, P < 0.01; 63.1% vs 28.9%, P < 0.01). Positive correlation was found between MRP-1 protein and mRNA expression (r = 0.598, P < 0.05).

CONCLUSION: MRP-1 expression shows a gradually increasing tendency in gastric carcinogensis both at mRNA and protein level.

[Expression of multidrug resistance (MDR)-associated proteins in solid tumors]

The causes of drug resistance in tumor cells vary widely. The present study aims to provide an update of multidrug resistance in tumor cells and, in particular, of multidrug resistance-associated proteins.

[Expression of multiple-drug resistant proteins in lung cancer]

BACKGROUND

Reduction of intracellular drug accumulation plays an important role in resistance to chemotherapy in neoplasms. MDR-proteins regulate this cell activity.

MATERIAL AND METHOD

A total of 147 tumor samples were collected from 143 patients. Thirty-five samples were obtained by bronchoscopy and 112 were surgical specimens. One hundred and one samples from 99 patients were valid for the study. The samples underwent cryopreservation and immunohistochemistry for detection of three multiple-drug resistant proteins (MDR-proteins): Pgp, Mrp1 and Lrp.

RESULTS

No proteins were expressed in 16 patients. A single protein was expressed in 32 patients: 3 Pgp, 11 Mrp1 and 18 Lrp=0. Two proteins were expressed in 34 patients: 24 Pgp and Lrp, 5 Mrp1 and Pgp, 5 Mrp1 and Lrp=0. All three proteins were expressed in 17 patients. No differences were observed in expression according to age (Pgp [p=0.74], Mrp1 [p=0.95], Lrp [p=0.26]). No differences were found according to sex, when both the number (p=0.72) and type (p=0.39) of simultaneously expressed proteins were analyzed. No differences were observed according to tumoral stage [number (p=0.55), type (p=0.21)] or histological grade [number (p=0.59), type (p=0.51)]. The tendency toward simultaneous expression of Pgp and Lrp was highly significant (p<0.01). The same tendency was not observed in the association between Mrp1 and Lrp (p=0.26).

CONCLUSIONS

MDR-proteins are frequently expressed in lung cancer. Of the three MDR-proteins studied, Lrp was the most frequent. Adenocarcinoma expressed less Mrp1 than other histological types. Squamous carcinoma expressed less Lrp than adenocarcinomas and large-cell undifferentiated carcinomas. In a considerable number of patients, more than two proteins were expressed simultaneously. Squamous-cell carcinomas tended to express Pgp, Mrp1 and Lrp simultaneously. Pgp was usually expressed in association with Lrp.

Prognostic Role of Thymidylate Synthase Polymorphisms in Gastric Cancer Patients Treated with Surgery and Adjuvant Chemotherapy

PURPOSE

To investigate the prognostic role of thymidylate synthase (TS) polymorphisms in gastric cancer patients treated with radical surgery and fluorouracil-based adjuvant chemotherapy.

EXPERIMENTAL DESIGN

Ninety gastric cancer cases were identified among 187 patients previously enrolled in prospective case-control studies for disease susceptibility. Patients were genotyped for a G/C nucleotide change within a triple 28 bp variable number of tandem repeat sequence in the TS 5'-untranslated region (5'-UTR) and a 6 bp deletion in the TS 3'-untranslated region (3'-UTR). According to available functional data, patients with 5'-UTR 2R/2R, 2R/3C, 3C/3C genotypes were classified as low TS producers (5'-UTRlow) and patients with 5'-UTR 3G/3G, 3G/3C, 2R/3G genotypes as high TS producers (5'UTRhigh). Patients with 3'-UTR del6/del6 and del6/ins6 genotypes were classified as low TS producers (3'-UTRlow) and patients with 3'-UTR ins6/ins6 genotype as high TS producers (3'-UTRhigh). The prognostic analysis was based on 5'-UTR/3'-UTR combined genotypes.

RESULTS

Ten patients (11%) were 5'-UTRhigh/3'-UTRhigh, 36 patients were 5'-UTRhigh/3'-UTRlow, 19 patients were 5'-UTRlow/3'-UTRhigh, and 25 patients were 5'-UTRlow/3'-UTRlow. 5'-UTRlow/3'-UTRlow patients showed the best outcome and the threshold of statistical significance was achieved in the comparison of disease-free survival and overall survival with 5'-UTRhigh/3'-UTRlow patients and 5'-UTRhigh/3'-UTRhigh patients. The presence of at least one high TS expression genotype showed independent adverse prognostic role in multivariate analysis.

CONCLUSIONS

The prognostic role of TS polymorphisms in gastric cancer deserves further investigation because the adverse effect of high TS expression genotypes may be a relevant information to improve adjuvant chemotherapeutic strategies.

Reversal of multidrug resistance in drug-resistant human gastric cancer cell line SGC7901/VCR by antiprogestin drug mifepristone

AIM: To explore the reversal effect of mifepristone on multidrug resistance (MDR) in drug-resistant human gastric cancer cell line SGC7901/VCR and its mechanisms.

METHODS: Expression of multidrug resistance-associated protein (MRP) was detected using reverse transcription-polymerase chain reaction (RT-PCR). Flow cytometry was used to assay the expression of P-glycoprotein (P-gp), Bcl-2, Bax, and the mean fluorescent intensity of intracellular rhodamine 123 in the cells. Meanwhile, the protein levels of Bcl-2 and Bax were also detected by Western blotting analysis. The sensitivity of cells to the anticancer agent, vincrimycin (VCR), and the intracellular [³H]VCR accumulation were determined by tetrazolium blue (MTT) assay and a liquid scintillation counter, respectively.

RESULTS: Expression of MRP and P-gp in SGC7901/VCR cells was 6.04-and 8.37-fold higher as compared with its parental SGC7901 cells, respectively. After treatment with 1, 5, 10, and 20 μmol/L mifepristone, SGC7901/VCR cells showed a 1.34-, 2.29-, 3.11-, and 3.71-fold increase in the accumulation of intracellular VCR, a known substrate of MRP, and a 1.03-, 2.04-, 3.08-, and 3.68-fold increase in the retention of rhodamine 123, an indicator of P-gp function, respectively. MTT assay revealed that the resistance of SGC7901/VCR cells to VCR was 11.96-fold higher than that of its parental cells. The chemosensitivity of SGC7901/VCR cells to VCR was enhanced by 1.02-, 7.19-, 12.84-, and 21.17-fold after treatment with mifepristone at above-mentioned dose. After 96 h of incubation with mifepristone 10 μmol/L, a concentration close to plasma concentrations achievable in human, the expression of Bcl-2 protein was decreased to (9.21 ± 0.65)% from (25.32 ± 1.44)%, whereas the expression of Bax protein was increased to (19.69 ± 1.13)% from (1.24 ± 0.78)% (P < 0.01). Additionally, the effects of mifepristone on the expression of Bcl-2 and Bax proteins in SGC7901/VCR cells were further demonstrated by Western blotting analysis.

CONCLUSION: Mifepristone has potent reversal effect on MDR in SGC7901/VCR via inhibiting the function of MRP and P-gp, modulating the expression of Bcl-2 and Bax proteins, and enhancing the sensitivity to anticancer agent VCR.

The association of P-glycoprotein with response to chemotherapy and clinical outcome in patients with osteosarcoma. A meta-analysis

BACKGROUND

There is controversy regarding whether P-glycoprotein (Pgp) may be a prognostic factor for the response to chemotherapy and clinical disease progression in patients with osteosarcoma.

METHODS

The authors conducted a meta-analysis of 14 studies (n = 631 patients) that evaluated the correlation between Pgp and histologic response to chemotherapy and clinical disease progression (death, metastasis, or recurrence). Data were synthesized in receiver operating characteristic curves and with fixed-effects and random-effects likelihood ratios and risk ratios.

RESULTS

Pgp had no discriminating ability for identifying poor responders versus good responders to chemotherapy: The positive likelihood ratio was 1.15 (95% confidence interval [95% CI], 0.93-1.43), and the negative likelihood ratio was 0.88 (95% CI, 0.65-1.18; random-effects calculations). There was some between-study heterogeneity, but no study showed strong discriminating ability. Conversely, Pgp positivity increased the risk of disease progression 1.92-fold (95% CI, 1.18-3.13; random-effects calculations) with some between-study heterogeneity that disappeared when only studies that employed immunohistochemistry were considered (risk ratio, 2.23; 95% CI, 1.37-3.64). The results were robust in various sensitivity analyses, although smaller studies tended to show stronger associations with the risk of disease progression compared with larger studies (P = 0.03).

CONCLUSIONS

The available evidence showed conclusively that Pgp was not associated with the histologic response of patients with osteosarcoma to combination chemotherapy regimens. Conversely, Pgp positivity, as determined by immunohistochemistry, was a strong correlate of more rapid disease progression, although there was heterogeneity across the performed studies that, to some extent, may have reflected bias, differential measurements of Pgp, or confounding with other risk factors.

Molecular analysis of therapy resistance in gastric cancer

Therapy resistance is the main cause of therapeutic failure and death in patients suffering from gastric carcinoma. Clinical resistance against systemic chemotherapy of gastric cancer is likely to be multifactorial and heterogenous. So far, no significant resistance factor that predicts the clinical outcome of systemic treatment of gastric carcinoma has been identified. In order to gain further understanding of therapy resistance in gastric carcinoma, various in vitro model systems were established. One of these models consists of the parental, drug-sensitive and thermosensitive human gastric carcinoma cell line EPG85-257P, its classical multidrug-resistant variant EPG85-257RDB, its atypical multidrug-resistant subline EPG85-257RNOV and their thermoresistant counterparts EPG85-257P-TR, EPG85-257RDB-TR, and EPG85-257RNOV-TR. This panel of cells was analyzed using morphological, biochemical, cellular and molecular biological methods to identify potential new factors involved in therapy resistance of gastric carcinoma. Cellular alterations that could be identified in these models were evaluated by functional investigations. This review will discuss the current state of knowledge of these new therapy resistance-associated factors, e.g. glypican-3 (GPC3), as well as the impact of well-known drug resistance-associated factors, such as MDR1/P-glycoprotein, on therapy resistance of gastric carcinoma.