Detection of P-glycoprotein in frozen and paraffin-embedded gastric adenocarcinoma tissues using a panel of monoclonal antibodies

Association of P-glycoprotein expression and response to anthracycline-based neoadjuvant chemotherapy in locally advanced breast cancer

BACKGROUND Neoadjuvant chemotherapy (NACT) has been shown to improve the overall survival of locally advanced breast cancer (LABC) patients with pathological complete response. However, the efficacy may be reduced due to chemoresistance mediated by P-glycoprotein (Pgp). This study aimed to explore the association between Pgp expression and patients’ response to NACT. METHODS A prospective cohort study was carried out from May 2018 to October 2019 at Cipto Mangunkusumo Hospital and Koja Hospital. Treatment-naïve LABC patients were consecutively enrolled in the study. Immunohistochemistry analysis of the biopsy samples was done to semi-quantitatively measure Pgp expression. The clinical response was evaluated after 3 cycles of NACT, while the pathological response was evaluated for subjects who underwent surgery post-NACT. RESULTS Mean age of the subjects was 46.2 (9.6) years old, and most of the cases were invasive ductal (78%) and luminal B subtype (61%). Pgp was strongly expressed in 21/27 subjects (78%). There were no differences between Pgp-positive and -negative subjects for clinical response (relative risk [RR] 1.1, 95% confidence interval [CI] 0.33–4.01, p = 0.61) and pathological response (RR 1.3, 95% CI 0.8–1.9, p = 0.22). Other clinicopathologic variables were not associated with either clinical or pathological responses. CONCLUSIONS These results showed that Pgp is expressed in most LABC patients, but its role as a predictive factor could not be established. However, due to the limited subjects and a lack of standardized Pgp measurement, careful consideration must be done when interpreting these results.

Association between temporal lobe P-glycoprotein expression and seizure recurrence after surgery for pharmacoresistant temporal lobe epilepsy

Surgery is recommended for pharmacoresistant temporal lobe epilepsy (TLE), but seizures recur in approximately one third of patients postsurgery. P-glycoprotein is an efflux multidrug transporter that is overexpressed in a range of epileptogenic pathologies. We hypothesized that increased expression of P-glycoprotein in the epileptogenic temporal lobe might be a marker for recurrence of pharmacoresistant seizures postsurgery. We performed immunohistochemistry on temporal lobe tissues resected from 69 patients who underwent anterior temporal lobectomy for pharmacoresistant TLE with histopathological proven hippocampal sclerosis. P-glycoprotein expression was rated by three pathologists independently. Patients with seizure recurrence (n=22) had greater number of positively stained capillaries (p=0.001) and higher P-glycoprotein immunoreactive score in capillaries (p=0.002) in the white matter of resected temporal lobe. The differences remained significant in multivariate analysis (p=0.002 and 0.006, respectively). The results suggest that P-glycoprotein expression in temporal lobe may be associated with seizure recurrence after surgery for pharmacoresistant TLE.

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 CYP3A isoforms and P-glycoprotein in human stomach, jejunum and ileum

1. CYP3A isoforms metabolise a diverse array of clinically important drugs and P-glycoprotein (P-gp), a transmembrane efflux pump, can extrude a wide variety of drugs from the cell. It has been suggested that the function of CYP3A4 is complementary to that of P-gp along the gastrointestinal (GI) tract, together forming a coordinated intestinal barrier against xenobiotics. Therefore, the expression of CYP3A4, CYP3A5, CYP3A7 and ABCB1 (P-gp) genes were quantified in five normal samples from the human stomach, seven from the jejunum and eight from the ileum by real-time reverse transcription-polymerase chain reaction and western blot analysis. 2. In the tissues examined, measurable mRNA expression of CYP3A was found in almost all samples from the stomach, jejunum and ileum. The rank order for CYP3A mRNA expression was CYP3A4 > CYP3A5 > CYP3A7 in the GI tract studied, whereas median mRNA CYP3A4 expression was highest in the small intestine and lowest in the stomach. Expression of ABCB1 mRNA was found in almost all samples and the median mRNA expression level was comparable in the jejunum and ileum, but lower in the stomach. Our data also show a significant correlation between all mRNA transcripts studied and a wide interindividual variation. 3. At the protein level, CYP3A4 was detected in all stomach and small intestine samples, the levels being substantially higher in the small intestine than in the stomach. P-Glycoprotein was detected in all GI samples, but no statistically significant difference was found along the GI tract considered. 4. Collectively, these results demonstrate that CYP3A4 is the main CYP3A expressed in the GI tract investigated, an extensive interindividual variability in the expression of the different CYP3A isoforms in all tissues examined and P-gp apoprotein levels similar in the stomach, jejunum and ileum.

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 of Cytochromes P450 3A and P-Glycoprotein in Human Large Intestinse in Paired Tumour and Normal Samples

Our objective was to investigate the expression of different cytochromes P450 3A (CYP3A4, CYP3A5, and CYP3A7) and P-glycoprotein (ABCB1) genes along the human large intestine in paired tumour and normal samples. Real-time reverse transcriptase-polymerase chain reaction was used to measure CYP3A4-, CYP3A5-, CYP3A7- and ABCB1-specific mRNA expression, and Western blot analysis was used to measure membrane protein levels of CYP3A4/7, CYP3A5 and P-glycoprotein. Levels of mRNA and membrane protein fractions in the large intestine were compared with those of normal human liver. The mRNA expressions of CYP3A4, CYP3A5, CYP3A7 and ABCB1 in the large intestine were found to be highly variable, but overall the levels were significantly lower than those measured in liver (P < 0.0001, P < 0.001, P < 0.0001 and P < 0.01, respectively). At the membrane protein level, CYP3A4/7 was detected in all large intestine samples examined and the levels were substantially higher than those of the liver (P < 0.01). Although expression of CYP3A5 was detected in all large intestine samples, in most the levels were too low to allow quantification. P-glycoprotein was readily detected at levels slightly higher than those of liver (P < 0.05). Comparison between paired samples of normal and tumour in large intestine showed no significant differences in either the mRNA or membrane protein levels of these genes. In conclusion, this work suggests a potential role of the large intestine in the absorption and metabolism of xenobiotics and nutrients and no difference in the CYP3A and P-glycoprotein membrane protein fractions and mRNA expression between normal and tumour tissues.

Multidrug resistance-associated protein (MRP1) gene is strongly expressed in gastric carcinomas. Analysis by immunohistochemistry and real-time quantitative RT-PCR

AIMS

To assess MRP1 protein and MRP1 mRNA levels in gastric carcinomas and in non-neoplastic mucosa remote from the tumours. MRP1 gene expression may play a role in the complex pattern of chemoresistance present in gastric carcinomas.

METHODS AND RESULTS

A total of 57 carcinomas and respective gastric tissues were included for immunohistochemical assessment with the anti-MRP1 monoclonal antibodies MRPr1 and QCRL-1. Of these, 35 tumour and gastric mucosa tissues were also assessed by real-time quantitative reverse transcriptase-polymerase chain reaction. Medium or high MRP1 protein expression was detected in 89% and 77% of carcinomas and in 96% and 93% of non-neoplastic gastric mucosa by MRPr1and QCRL-1, respectively. No difference in MRP1 mRNA levels was detected between carcinomas and non-neoplastic gastric mucosa tissues in 77% of the patients. A significant correlation was found between MRP1 mRNA level and protein expression detected in carcinomas related to non-neoplastic gastric mucosa, although they were non-concordant in 29% of the patients.

CONCLUSIONS

MRP1 gene is usually expressed in most gastric carcinomas and does not differ substantially from that observed in non-neoplastic gastric mucosa remote from the tumour. However, a decrease in MRP1 gene expression is found in some carcinomas. For accurate assessment of changes in MRP1 expression between tumour and normal tissues both protein and mRNA detection are necessary.

Expression and cellular distribution of multidrug resistance-related proteins in the hippocampus of patients with mesial temporal lobe epilepsy

PURPOSE

This study investigated the cellular distribution of different multidrug resistance (MDR)-related proteins such as P-glycoprotein (P-gp), the multidrug resistance-associated proteins (MRP) 1 and 2, and the major vault protein (MVP) in normal and sclerotic hippocampus of patients with medically refractory mesial temporal lobe epilepsy (MTLE).

METHODS

Single- and double-label immunocytochemistry was used on brain sections of control hippocampus and of hippocampus of refractory MTLE patients.

RESULTS

In TLE cases with hippocampal sclerosis (HS), all four MDR proteins examined that had low or no expression in control tissue were upregulated, albeit with different cellular distribution patterns. P-gp immunoreactivity (IR) was observed in astrocytes in regions with diffuse reactive gliosis. In 75% of HS cases, strong P-gp IR was detected in blood vessels, with prominent endothelial labeling. Reactive astrocytes displayed low MRP1 IR. However, glial MRP1 expression was noted in glial endfoot processes around blood vessels. Neuronal MRP1 expression was observed in hypertrophic hilar neurons and in a few residual neurons of the CA1 region. Hippocampal MRP2 expression was observed in the large majority of HS cases in blood vessels. Hypertrophic hilar neurons and blood vessels within the sclerotic hippocampus expressed major vault protein (MVP).

CONCLUSIONS

These findings indicate that MDR proteins are upregulated in concert in the hippocampus of patients with refractory MTLE, supporting their role in the mechanisms underlying drug resistance. The specific cell-distribution patterns within the sclerotic hippocampus suggest different cellular functions, not necessarily linked only to clinical drug resistance.

Expression of multidrug resistance-1 protein inversely correlates with paclitaxel response and survival in ovarian cancer patients: a study in serial samples

OBJECTIVES

The role of MDR1 in clinical paclitaxel resistance remains poorly characterized. This study sought to identify the incidence and significance of P-glycoprotein (P-gp) over-expression on survival, tumor response to paclitaxel and the effect of prior cytotoxic exposure on P-gp expression in patients with paired primary and recurrent ovarian cancer samples.

METHODS

Retrospective survival analysis. P-gp expression was evaluated immunohistochemically with antibodies c494 and c219.

RESULTS

Thirty-two patients were identified from the tumor registry. Median interval between primary and secondary surgery was 17.9 (5.7-40.9) months. Only five primary tumors (16%) demonstrated +++ staining for P-gp. First-line treatment contained paclitaxel in 17 patients (53%) and 26 patients (81%) had been exposed to P-gp exportable chemotherapy before second surgery. Only seven of the recurrent tumors (22%) were +++. Only one of seven (14% (95% CI 0-46%)) recurrent tumors with ++ or +++ staining responded to subsequent paclitaxel, while 8 of 10 (80% (CI 46-100%)) recurrent tumors with 0/+ staining responded (P = 0.025). In multivariate analysis of outcome following second surgery, response to paclitaxel (P = 0.004) and P-gp over-expression (P < 0.001) were significant predictors of survival.

CONCLUSIONS

De novo strong P-gp over-expression is uncommon, appears to change little over time or with prior exposure to chemotherapy. However, P-gp over-expression is a significant prognostic factor, and at the time of disease, relapse is inversely correlated with tumor response to paclitaxel.

Expression and cellular distribution of multidrug transporter proteins in two major causes of medically intractable epilepsy: focal cortical dysplasia and glioneuronal tumors

The cell-specific distribution of multidrug resistance extrusion pumps was studied in developmental glioneuronal lesions, including focal cortical dysplasia (15 cases) and ganglioglioma (15 cases) from patients with medically intractable epilepsy. Lesional, perilesional, as well as normal brain regions were examined for the expression of the multidrug resistance gene 1 encoded P-glycoprotein (P-gp) and the multidrug resistance-associated protein 1 (MRP1) by immunocytochemistry. In normal brain MRP1 expression was below detection, whereas P-gp staining was present only in blood vessels. MRP1 and P-gp immunoreactivity was observed in dysplastic neurons of 11/15 cases of focal cortical dysplasia, as well as in the neuronal component of 14/15 ganglioglioma. Glial cells with astrocytic morphology within the lesion showed multidrug-resistant protein immunoreactivity (P-gp>MRP1). Moderate to strong MRP1 and P-gp immunoreactivity was observed in a population of large ballooned neuroglial cells. P-gp appeared to be most frequently expressed in glial fibrillary acidic protein-positive balloon cells (glial type), whereas MRP1 was more frequently expressed in microtubule-associated protein 2-positive balloon cells (neuronal type). In both types of lesions strong P-gp immunoreactivity was found in lesional vessels. Perilesional regions did not show increased staining in vessels or in neuronal cells compared with normal cortex. The predominant intralesional cell-specific distribution of multidrug transporter proteins supports the hypothesis of a constitutive overexpression as common mechanism underlying the intrinsic pharmaco-resistance to antiepileptic drugs of both malformative and neoplastic glioneuronal developmental lesions.

The cytotoxic effect of mistletoe lectins I, II and III on sensitive and multidrug resistant human colon cancer cell lines in vitro

Multidrug resistance glycoprotein1 (MDR-1) eliminates amphiphilic chemotherapeutic agents out of tumour cells leading to therapeutic failures. The aim of this study was to investigate the cytotoxic effect of mistletoe lectins (MLs) I, II and III on the sensitive human colon cancer cell line HT 29(mdr-), its multidrug resistant variant HT 29(mdr+), the variant HT 29(SF1m) transfected with the MDR-1 gene and its sensitive control cell line HT 29(deltaSF). Both cell proliferation and ML binding pattern were analysed. Marked quantitative differences concerning the cytotoxic effect of the three MLs on the different cell lines were observed. All MLs showed the greatest cytotoxicity towards the HT 29(mdr+) cells, in which multidrug resistance (MDR) was induced by increasing concentrations of a MDR inducing agent. In contrast, MDR-1 and mock-transfected cells showed almost the same sensitivity towards the three MLs as the control cells (HT 29(mdr-)). FACS analysis showed that the HT 29(mdr+) cells were the cells with the highest density of ML binding sites. Thus, higher sensitivity of HT 29(mdr+) cells are not caused by the overexpression of MDR-1, but are caused by the general changes of the cellular glycosylation during the acquisition of the MDR phenotype.

Drug resistance in epilepsy: expression of drug resistance proteins in common causes of refractory epilepsy

Epilepsy is resistant to drug treatment in about one-third of cases, but the mechanisms underlying this drug resistance are not understood. In cancer, drug resistance has been studied extensively. Amongst the various resistance mechanisms, overexpression of drug resistance proteins, such as multi-drug resistance gene-1 P-glycoprotein (MDR1) and multidrug resistance-associated protein 1 (MRP1), has been shown to correlate with cellular resistance to anticancer drugs. Previous studies in human epilepsy have shown that MDR1 and MRP1 may also be overexpressed in brain tissue from patients with refractory epilepsy; expression has been shown in glia and neurones, which do not normally express these proteins. We examined expression of MDR1 and MRP1 in refractory epilepsy from three common causes, dysembryoplastic neuroepithelial tumours (DNTs; eight cases), focal cortical dysplasia (FCD; 14 cases) and hippocampal sclerosis (HS; eight cases). Expression was studied immunohistochemically in lesional tissue from therapeutic resections and compared with expression in histologically normal adjacent tissue. With the most sensitive antibodies, in all eight DNT cases, reactive astrocytes within tumour nodules expressed MDR1 and MRP1. In five of eight HS cases, reactive astrocytes within the gliotic hippocampus expressed MDR1 and MRP1. Of 14 cases of FCD, MDR1 and MRP1 expression was noted in reactive astrocytes in all cases. In five FCD cases, MRP1 expression was also noted in dysplastic neurones. In FCD and DNTs, accentuation of reactivity was noted around lesional vessels. Immunoreactivity was always more frequent and intense in lesional reactive astrocytes than in glial fibrillary acidic protein-positive reactive astrocytes in adjacent histologically normal tissue. MDR1 is able to transport some antiepileptic drugs (AEDs), and MRP1 may also do so. The overexpression of these drug resistance proteins in tissue from patients with refractory epilepsy suggests one possible mechanism for drug resistance in patients with these pathologies. We propose that overexpressed resistance proteins lower the interstitial concentration of AEDs in the vicinity of the epileptogenic pathology and thereby render the epilepsy caused by these pathologies resistant to treatment with AEDs.

Changes in P-glycoprotein expression in gastric carcinoma with respect to distant gastric mucosa may be influenced by p53

BACKGROUND

The effectiveness of some chemotherapeutic agents used to treat gastric carcinoma patients may be impaired by the presence of P-glycoprotein (P-gp) and the status of p53. A modulation of P-gp expression by p53 or other alterations during tumorigenesis have been reported. The authors analyzed P-gp expression in relation to p53 and histopathologic features in gastric carcinoma.

METHODS

Forty-one resected gastric carcinomas and mucosa distant from the tumor were assessed for P-gp expression by immunohistochemistry with C494 and JSB-1 antibodies. p53 expression was also immunohistochemically assessed by DO7 antibody in tumor samples. P-gp and p53 expression were semiquantitatively analyzed according to the percentage of stained cells. Histologic type, grade, vessel invasion, and stage were also studied.

RESULTS

Moderate or high P-gp expression was detected in gastric carcinoma in 29 cases (71%) and in gastric mucosa remote from the tumor in 36 cases (88%). This reduction in P-gp expression was observed in 22% of the carcinomas, all but 1 being p53 immunonegative tumors. Thus, 8 (42%) of the p53 immunonegative carcinomas showed a loss of P-gp expression compared with their distant gastric mucosa. All p53 immunopositive carcinomas coexpressed P-gp. No correlation between P-gp expression and histologic type, grade, vessel invasion, or stage was found.

CONCLUSIONS

P-gp expression in gastric carcinomas is frequent and coexpression with p53 is found. The analysis of P-gp expression in carcinomas and distant mucosa show that it is not regulated by p53, but a loss of P-gp detected in some of these carcinomas is mainly associated with a lack of p53 protein accumulation.

Changes in P-glycoprotein expression in gastric carcinoma with respect to distant gastric mucosa may be influenced by p53

BACKGROUND

The effectiveness of some chemotherapeutic agents used to treat gastric carcinoma patients may be impaired by the presence of P-glycoprotein (P-gp) and the status of p53. A modulation of P-gp expression by p53 or other alterations during tumorigenesis have been reported. The authors analyzed P-gp expression in relation to p53 and histopathologic features in gastric carcinoma.

METHODS

Forty-one resected gastric carcinomas and mucosa distant from the tumor were assessed for P-gp expression by immunohistochemistry with C494 and JSB-1 antibodies. p53 expression was also immunohistochemically assessed by DO7 antibody in tumor samples. P-gp and p53 expression were semiquantitatively analyzed according to the percentage of stained cells. Histologic type, grade, vessel invasion, and stage were also studied.

RESULTS

Moderate or high P-gp expression was detected in gastric carcinoma in 29 cases (71%) and in gastric mucosa remote from the tumor in 36 cases (88%). This reduction in P-gp expression was observed in 22% of the carcinomas, all but 1 being p53 immunonegative tumors. Thus, 8 (42%) of the p53 immunonegative carcinomas showed a loss of P-gp expression compared with their distant gastric mucosa. All p53 immunopositive carcinomas coexpressed P-gp. No correlation between P-gp expression and histologic type, grade, vessel invasion, or stage was found.

CONCLUSIONS

P-gp expression in gastric carcinomas is frequent and coexpression with p53 is found. The analysis of P-gp expression in carcinomas and distant mucosa show that it is not regulated by p53, but a loss of P-gp detected in some of these carcinomas is mainly associated with a lack of p53 protein accumulation.