Expression of mdr1 and gst-pi in human breast tumours: comparison to in vitro chemosensitivity

Innovative nanotheranostics: Smart nanoparticles based approach to overcome breast cancer stem cells mediated chemo- and radioresistances

The alarming increase in the number of breast cancer patients worldwide and the increasing death rate indicate that the traditional and current medicines are insufficient to fight against it. The onset of chemo- and radioresistances and cancer stem cell-based recurrence make this problem harder, and this hour needs a novel treatment approach. Competent nanoparticle-based accurate drug delivery and cancer nanotheranostics like photothermal therapy, photodynamic therapy, chemodynamic therapy, and sonodynamic therapy can be the key to solving this problem due to their unique characteristics. These innovative formulations can be a better cargo with fewer side effects than the standard chemotherapy and can eliminate the stability problems associated with cancer immunotherapy. The nanotheranostic systems can kill the tumor cells and the resistant breast cancer stem cells by novel mechanisms like local hyperthermia and reactive oxygen species and prevent tumor recurrence. These theranostic systems can also combine with chemotherapy or immunotherapy approaches. These combining approaches can be the future of anticancer therapy, especially to overcome the breast cancer stem cells mediated chemo- and radioresistances. This review paper discusses several novel theranostic systems and smart nanoparticles, their mechanism of action, and their modifications with time. It explains their relevance and market scope in the current era. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Role of scintimammography in assessing the response of neoadjuvant chemotherapy in locally advanced breast cancer

Locally advanced breast cancer (LABC) is a common cancer in the developing countries. Neoadjuvant chemotherapy (NACT) is a very important step in the treatment of such tumors and hence that the disease can be down staged and made amenable for surgery. All the tumors do not respond to the therapy equally. Hence, it becomes very important to predict the response of chemotherapy in such cases. This study evaluated the role of scintimammography in assessing the response to NACT in 23 patients with LABC. Histologically proven 23 patients of LABC were recruited in this study. Prechemotherapy tumor size was measured clinically in all patients and technitium (Tc)-99m sestamibi test was performed before NACT for each patient. Early (10 min) and delayed (2 h) image of the breast were acquired in anterior and lateral views after Tc-99m sestamibi intravenous injections and wash out rate (WOR) was computed. After 3-4 cycles of chemotherapy, surgery in the form of modified radical mastectomy was performed in 20 out of 23 patients (3 patients lost to follow-up) with pathologic evaluation of the residual tumor size. The pretherapy Tc-99m sestamibi WOR ranged from 8.3% to 68% with mean ± SD of 34.5% ±16.5%. The prechemotherapy Tc-99m sestamibi study predicted chemoresistance (WOR >45%) in 6 out of 20 patients and no chemoresistance (WOR <45%) in 14 out of 20 patients. When the WOR cut-off was set at >45%, the predictivity of the test was indicated by sensitivity of 91.7%, specificity of 62.5%, positive predictive value of 78.6%, and negative predictive value of 82.3% with a likelihood ratio of 0.1. Tc-99m sestamibi WOR is a reliable test for predicting tumor response to NACT. WOR >45% is highly predictive of chemoresistance with likelihood ratio of 0.1 than WOR <45% being predictive of chemoresponsiveness.

Glutathione S-transferase P1 c.313A > G polymorphism could be useful in the prediction of doxorubicin response in breast cancer patients

BACKGROUND

Identification of predicting factors for anthracyclines-based chemotherapy remains a clinical challenge. Glutathione S-transferase (GSTs) enzymes detoxify chemotherapy drugs and their metabolites. Several polymorphisms in GST genes result in reduced or no activity of the enzymes. Specifically, GSTM1 and GSTT1 genes are polymorphically deleted, the polymorphism GSTP1 c.313A>G (rs1695) determines the amino acid substitution Ile105Val, where the Val-containing enzyme has reduced activity. Also, GSTA1*B allele has reduced levels of GSTA1 enzyme. Several polymorphisms in GSTs have been associated with differences in survival for cancer patients treated with chemotherapy.

PATIENTS AND METHODS

We genotyped a total of five polymorphisms in GSTM1, GSTT1, GSTP1 and GSTA1 genes in 159 patients with locally advanced breast cancer, treated with single-agent doxorubicin or docetaxel (Taxotere). Gene expression microarrays were performed in 67 breast tumor samples. We correlate this data with treatment outcome.

RESULTS

In multivariate analysis, patients homozygous GG for GSTP1 c.313A>G SNP had a lower risk of chemoresistance when treated with doxorubicin (odds ratio 0.106; confidence interval 0.012-0.898; P=0.040). No association was found in the docetaxel arm. Also, we found that GSTP1 expression varied significantly among breast cancer molecular subtypes.

CONCLUSIONS

GSTP1 may constitute another tool contributing to individualized anthracycline-based therapy.

Prediction of lack of response to neoadjuvant chemotherapy in rare breast tumour histology with Tc-99m sestamibi scintimammography

The authors report a case of a 47-year-old female with a malignant lump in the right breast and ipsilateral axillary nodal involvement. She was pathologically misinterpreted as a case of ductal cell carcinoma with papillary component on fine needle aspiration cytology (FNAC) pre-operatively. On lines of the FNAC report, the patient underwent scintimammography (SMM) for prediction of treatment response based on washout pattern. The SMM revealed rapid washout of radiotracer predictive of poor responder. Despite unfavourable result seen with SMM, the patient received 4 cycles of neo-adjuvant chemotherapy (NACT). However, there was no clinical response after chemotherapy. The post-surgical histopathology revealed the actual histology to be pleomorphic liposarcoma. This case highlights that SMM has the ability to predict non-responsiveness of unusual tumour histology to standard NACT.

High-definition DNA methylation profiles from breast and ovarian carcinoma cell lines with differing doxorubicin resistance

Acquired drug resistance represents a frequent obstacle which hampers efficient chemotherapy of cancers. The contribution of aberrant DNA methylation to the development of drug resistant tumor cells has gained increasing attention over the past decades. Hence, the objective of the presented study was to characterize DNA methylation changes which arise from treatment of tumor cells with the chemotherapeutic drug doxorubicin. DNA methylation levels from CpG islands (CGIs) linked to twenty-eight genes, whose expression levels had previously been shown to contribute to resistance against DNA double strand break inducing drugs or tumor progression in different cancer types were analyzed. High-definition DNA methylation profiles which consisted of methylation levels from 800 CpG sites mapping to CGIs around the transcription start sites of the selected genes were determined. In order to investigate the influence of CGI methylation on the expression of associated genes, their mRNA levels were investigated via qRT-PCR. It was shown that the employed method is suitable for providing highly accurate methylation profiles, comparable to those obtained via clone sequencing, the gold standard for high-definition DNA methylation studies. In breast carcinoma cells with acquired resistance against the double strand break inducing drug doxorubicin, changes in methylation of specific cytosines from CGIs linked to thirteen genes were detected. Moreover, similarities between methylation profiles obtained from breast and ovarian carcinoma cell lines with acquired doxorubicin resistance were found. The expression levels of a subset of analyzed genes were shown to be linked to the methylation levels of the analyzed CGIs. Our results provide detailed DNA methylation information from two separate model systems for acquired doxorubicin resistance and suggest the occurrence of similar methylation changes in both systems upon exposure to the drug.

Trabectedin (ET-743, Yondelis) is a substrate for P-glycoprotein, but only high expression of P-glycoprotein confers the multidrug resistance phenotype

Trabectedin (ET-743, Yondelis) is a novel anticancer drug currently undergoing phase II and III investigations. There are various and conflicting reports whether trabectedin is a substrate for P-glycoprotein (P-gp), an important factor in drug disposition and multi-drug resistance (MDR). We have now unambiguously shown that trabectedin is a P-gp substrate by investigating vectorial transport over monolayers of LLC-PK1 pig kidney and Madine-Darby Canine kidney (MDCK) cells and the mdr1a and/or MDR1 transfected subclones. We further characterized the cytotoxic effects and cellular accumulation of trabectedin in these cell lines as well as in a panel of other cell lines with high or moderate expression levels of P-gp. Trabectedin displayed the typical MDR phenotype only in highly P-gp expressing cell lines, but not in cell lines with expression levels more closely conforming to clinical samples, suggesting that P-gp will not confer resistance to trabectedin in cancer patients.

Multidrug resistance in locally advanced breast cancer

BACKGROUND

Advanced breast cancer cases can still be encountered resulting in poor prognosis. The primary treatment for these patients is chemotherapy, and multidrug resistance (MDR) is a serious obstacle in the treatment. Detecting drug resistance before first-line chemotherapy may increase the patient's survival. In this study, the role of MDR is evaluated in locally advanced breast cancer patients.

METHODS

Reverse transcriptase polymerase chain reaction was used for the detection of MDR genes, ABCB1 and ABCC1. Immunohistochemistry was used for the detection of MDR proteins, P-glycoprotein (Pgp) and MDR-associated protein 1.

RESULTS

Breast tissues from 25 patients both before and after chemotherapy were examined. Five patients were unresponsive to chemotherapy. Four had ABCB1 gene expression induced by chemotherapy, and Pgp positivity was detected in 9 patients after chemotherapy. Both the induction of ABCB1 gene expression (p < 0.001) and Pgp positivity (p < 0.001) during chemotherapy were significantly related with clinical response. Although 80% of the clinically unresponsive patients had ABCC1 gene expression, the relation between ABCC1 expression and clinical drug response was not significant.

CONCLUSION

In locally advanced breast cancer, ABCB1 gene expression during chemotherapy contributes to clinical unresponsiveness. However, ABCC1 gene expression did not correlate strongly with the clinical response.

Prognostic impact of multidrug resistance gene expression on the management of breast cancer in the context of adjuvant therapy based on a series of 171 patients

Study of the prognostic impact of multidrug resistance gene expression in the management of breast cancer in the context of adjuvant therapy. This study involved 171 patients treated by surgery, adjuvant chemotherapy±radiotherapy±hormonal therapy (mean follow-up: 55 months). We studied the expression of multidrug resistance gene 1 (MDR1), multidrug resistance-associated protein (MRP1), and glutathione-S-transferase P1 (GSTP1) using a standardised, semiquantitative rt–PCR method performed on frozen samples of breast cancer tissue. Patients were classified as presenting low or high levels of expression of these three genes. rt-PCR values were correlated with T stage, N stage, Scarff–Bloom–Richardson (SBR) grade, age and hormonal status. The impact of gene expression levels on 5-year disease-free survival (DFS) and overall survival (OS) was studied by univariate and multivariate Cox analysis. No statistically significant correlation was demonstrated between MDR1, MRP1 and GSTP1 expressions. On univariate analysis, DFS was significantly decreased in a context of low GSTP1 expression (P=0.0005) and high SBR grade (P=0.003), size ⩾5 cm (P=0.038), high T stage (P=0.013), presence of intravascular embolus (P=0.034), and >3 N+ (P=0.05). On multivariate analysis, GSTP1 expression and the presence of ER remained independent prognostic factors for DFS. GSTP1 expression did not affect OS. The levels of MDR1 and MRP1 expression had no significant influence on DFS or OS. GSTP1 expression can be considered to be an independent prognostic factor for DFS in patients receiving adjuvant chemotherapy for breast cancer.

YB-1 is upregulated during prostate cancer tumor progression and increases P-glycoprotein activity

BACKGROUND

Currently, the main obstacle to curing advanced prostate cancer is development of androgen independence (AI), where malignant cells acquire the ability to survive in the absence of androgens. Our initial experimental approach used cDNA microarrays to characterize changes in gene expression in the LNCaP human prostate tumor model during progression to AI. The transcription factor Y-box binding protein (YB-1) was shown to be one of the genes upregulated. We focused on increased YB-1 expression during progression in clinical specimens, and further examined one of its downstream targets, P-glycoprotein (P-gp).

METHODS

Northern blot analysis was performed on LNCaP tumor series, as well as immunohistochemical analyses of human prostate cancer tissue samples. YB-1 was transiently transfected and transport analysis were performed to analyze P-gp efflux activity.

RESULTS

YB-1 expression is markedly increased during benign to malignant transformation and further following androgen ablation. In addition, increased YB-1 expression after castration in the LNCaP model is linked to upregulation of P-gp. We demonstrate that YB-1 upregulates P-gp activity resulting in a 40% intracellular decrease in the P-gp substrate vinblastine. We have also found that P-gp increases the efflux of the endogenous androgen, dihydrotestosterone (DHT), from prostate cells and leads to decreased androgen regulated gene expression.

CONCLUSIONS

We hypothesize that early in prostate cancer progression, increased expression of YB-1 may increase P-gp activity which may in turn lower androgen levels in the prostate tumor cells. Suppression of androgen levels may activate cell survival pathways and lead to an adaptive survival advantage of androgen independent prostate cancer cells following androgen ablation therapy.

Multidrug resistance gene 1 expression in salivary gland adenocarcinomas and oral squamous-cell carcinomas

In combined chemotherapy for head-and-neck cancer (HNC), salivary gland-cell adenocarcinoma (SGA) shows insufficient clinical outcome, and it has been suggested that the sensitivity and/or the mechanism of resistance to anti-cancer drugs are different between SGA and oral squamous-cell carcinoma (SCC). The aim of our study was to clarify whether P-glycoprotein (P-gp) expression is associated with multidrug resistance (MDR) in HNC and the difference in the process of its development between SGA and SCC. In immunohistochemical analysis, P-gp expression was found in the ductal cells of salivary glands but not in oral mucosal epithelium. In cancer tissues, a few SCC cells in 12 of 37 and most cells in all SGAs expressed P-gp. The intensive P-gp expression was significantly found in SGA compared with SCC. In an in vivo chemotherapeutic model using tumor-bearing nude mice, P-gp expression in counterparts was observed in only a few cells of the HSY line, while no P-gp expression was observed in Hepd cells. However, P-gp expression was developed in both HSY and Hepd cell lines after vincristine (VCR) treatment. RT-PCR showed that the mean ratios of mdr1 mRNA expression levels in HSY clones were 3.7-fold higher than those in Hepd clones after VCR treatment, while each cell line exhibited both induction and activated production of P-gp. These results suggest that P-gp-related MDR in SGA is an inherent phenotype caused by both high levels of P-gp induction and activated P-gp production during VCR treatment, while that in SCC is an acquired phenotype chiefly caused by induction of P-gp.

Multidrug resistance phenotype in high grade soft tissue sarcoma: correlation of P-glycoprotein immunohistochemistry with pathologic response to chemotherapy

BACKGROUND

P-glycoprotein-mediated drug efflux has been implicated as an important mechanism of multidrug resistance (MDR) in cancer. Its role in chemotherapy resistance in soft tissue sarcoma is unclear.

METHODS

Tumor specimens prior to and following neoadjuvant chemotherapy from 29 cases of high grade soft tissue sarcoma were analyzed with 2 monoclonal antibodies (C494 and JSB-1) that recognize different epitopes of P-glycoprotein. Staining intensity was graded 0 = negative, 1 = equivocal, 2 = moderate, 3 = strong. Only cases with Grade 2 or 3 staining intensity with both antibodies were considered MDR positive. The resection specimens were evaluated for tumor necrosis postchemotherapy. Pathologic response was graded as good for <15%, moderate for 15-50%, or poor for >50% posttreatment tumor viability.

RESULTS

Of the 29 pretreatment specimens, 10 (34%) were MDR positive and 19 (66%) were MDR negative. Pathologic response to treatment was characterized as good in 6, moderate in 7, and poor in 16 patients. Of the MDR positive biopsies, 9 (90%) had poor response, compared with 7 (36%) in the MDR negative biopsy group (P = 0.0078). None of the cases with MDR positive biopsies had a good response, compared with 6 cases in which biopsies were MDR negative (32%) (P = 0.057). Only one MDR negative case became MDR positive posttreatment.

CONCLUSIONS

Expression of MDR phenotype is found in approximately one-third of high grade soft tissue sarcomas. These preliminary data show a significant correlation between MDR phenotype and poor pathologic response to chemotherapy, and suggest that MDR induction by chemotherapy in soft tissue sarcoma is an uncommon event.

Complete regression of recurrent esophageal carcinoma with reduced expression of glutathione S-transferase-pi by treatment with continuous infusion of 5-fluorouracil and low-dose cisplatin infusion

The mortality rate of recurrent esophageal carcinoma remains high because of its resistance to chemotherapy and radiation therapy. We present a patient with recurrent esophageal carcinoma, which dramatically disappeared after treatment with the combination of continuous infusion of 5-fluorouracil and low-dose cis-Diamminedichloroplatinum-II (cisplatin) infusion (FP therapy). Furthermore, we immunohistologically found that glutathione S-transferases (GST)-pi, a marker of resistance to cisplatin, was faintly expressed both in the endoscopical biopsy specimens of recurrent tumor and in the resected specimens of esophageal carcinoma and metastatic lymph nodes. FP therapy was suggested to be effective for recurrent esophageal carcinoma. Immunostaining for GST-pi might be a prospective marker for the sensitivity of esophageal carcinoma to FP therapy, particularly cisplatin.

Phorbol ester-induced P-glycoprotein phosphorylation and functionality in the HTB-123 human breast cancer cell line

The discordance between P-glycoprotein (P-gp) expression and functionality [as measured by the efflux of doxorubicin (DOX)] was analyzed in a DOX-sensitive human breast cancer cell line (HTB-123) with high reactivity against four P-gp specific monoclonal antibodies (C219, MRK-16, UIC2, and 4E3). Reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting analyses confirmed the overexpression of MDR1 mRNA and P-gp in this cell line. However, incubation of cells with efflux blockers, verapamil (VPL) or dipyridamole (DPD), did not enhance cellular (DOX) accumulation or cytotoxicity. Upon incubation with 12-O-tetradecanoylphorbol-13-acetate (TPA), HTB-123 cells retained less DOX than control cells and were sensitive to the efflux blockers verapamil or dipyridamole. These observations suggest that 12-O-tetradecanoylphorbol-13-acetate-induced P-gp phosphorylation may be associated with induction of P-gp-mediated drug efflux in the HTB-123 cell line.

Multidrug resistance in glioblastoma. Chemosensitivity testing and immunohistochemical demonstration of P-glycoprotein

Chemosensitivity of previously untreated glioblastomas to mitoxantrone, methotrexate, ACNU and BCNU was tested on cultured tissue. Sixteen of 62 tumors were partially chemosensitive in vitro. The monoclonal antibody C 219 was used to demonstrate the presence of p-glycoprotein in the 16 sensitive and five highly resistant glioblastomas. All 21 tumors identically expressed p-glycoprotein. These results show that untreated glioblastomas primarily express p-glycoprotein even if they are at least partially chemosensitive in vitro. Therefore, immunohistochemical demonstration of p-glycoprotein with the monoclonal antibody C 219 can not provide reliable information on short term resistance of the individual tumors to antineoplastic drugs. P-glycoprotein expression could, however, help to explain the disappointing overall long-term efficacy of chemotherapy by showing the existence of cell populations with early drug resistance in these tumors.

Comparative evaluation by semiquantitative reverse transcriptase polymerase chain reaction of MDR1, MRP and GSTp gene expression in breast carcinomas

Identification and quantitative evaluation of drug resistance markers are essential to assess the impact of multidrug resistance (MDR) in clinical oncology. The MDR1 gene confers pleiotropic drug resistance in tumour cells, but other molecular mechanisms are also involved in drug resistance. In particular, the clinical pattern of expression of the other MDR-related genes is unclear and their interrelationships are still unknown. Here, we report standardization of the procedures used to determine a reliable method of semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) using a standard series of drug-sensitive and increasingly resistant cell lines to evaluate the expression of three MDR-related genes, i.e. MDR1 (multidrug resistance gene 1), MRP (multidrug resistance related protein) and GSTp (glutathione-S-transferase p), reported to be endogenous standard genes for normalization of mRNAs. A total of 74 breast cancer surgical biopsies, obtained before any treatment, were evaluated by this method. When compared with classical clinical and laboratory findings, GSTp mRNA level was higher in diploid tumours. However, the main finding of our study suggests a clear relationship between two of these MDR-related gene expressions, namely GSTp and MRP. This finding provides new insight into human breast tumours, which may possibly be linked to the glutathione conjugate carrier function of MRP. Well defined semiquantitative RT-PCR procedures can therefore constitute a powerful tool to investigate MDR phenotype at mRNA levels of different related genes in small and precious tumour biopsy specimens.

mdr1 mRNA expression by RT-PCR in patients with primary breast cancer submitted to neoadjuvant therapy

mdr1 expression by reverse transcription and polymerase chain reaction (RT-PCR) has been compared to P-glycoprotein (Pgp) expression by immunohistochemistry (IHC) and correlated with clinical response to neoadjuvant therapy. RNA has been recovered from glass slide smears of fine-needle aspiration from 57 untreated primary breast cancers prior to neoadjuvant chemotherapy (33 cases), hormone therapy (23 cases), or both (1 case). Furthermore, mdr1 mRNA has been analyzed in 6 cases after 2 months of treatment. The neoadjuvant therapy consisted of 4 cycles of adriamycin and cyclophosphamide or tamoxifen. Of 57 tumor specimens, an interpretable result was obtained in 52 cases, indicating the feasibility of the analysis by RT-PCR with very small tumor specimens. The presence of mdr1 mRNA has been documented in 44/52 (84%) tumor samples with a spectrum of expression levels. The expression of mdr1 mRNA was compared with P-glycoprotein (Pgp) expression by IHC using JSB-1, 4E3, and C494 monoclonal antibodies in 48 of the 52 interpretable tumor samples. 12/48 (25%) expressed Pgp by IHC. All tumors expressing Pgp by IHC were also positive by RT-PCR. The results confirm the higher prevalence of mdr1 mRNA compared to the protein expression. However, mdr1 mRNA expression was found to correlate significantly with resistance to neoadjuvant hormone therapy only while Pgp expression detected by JSB-1 immunostaining only correlated with chemoresistance. The lack of convincing correlation with chemoresistance suggests that mRNA and Pgp may not be directly or solely responsible for clinical response to drugs. Further studies should focus on the post-translational modulation of P-glycoprotein and other mechanisms of drug resistance.

Multidrug resistance in breast cancer: a meta-analysis of MDR1/gp170 expression and its possible functional significance

BACKGROUND

P-glycoprotein (gp170; encoded by the MDR1 gene [also known as PGY1]) is a membrane protein capable of exporting a variety of anticancer drugs from cells. MDR1/gp170 expression has been studied in breast cancer, but the prevalence of this expression and its role in breast tumor drug resistance are unclear.

PURPOSE

We conducted a critical review and meta-analysis of studies examining MDR1/gp170 expression in breast cancer to estimate the likely prevalence and clinical relevance of this expression. We also explored reasons for differences in the findings from individual studies.

METHODS

Published papers on MDR1/gp170 expression in breast cancer were identified by searching several literature databases and reviewing the bibliographies of identified papers. Variability across the studies in the proportion of tumors expressing MDR1/gp170 was assessed by use of chi-squared tests of homogeneity, weighted means, and weighted linear regression. Pooled relative risks (RRs) for the association between the induction of MDR1/gp170 expression and prior chemotherapy and associations between MDR1/gp170 expression and several clinical outcomes were estimated by use of Mantel-Haenszel methods. Heterogeneity among the pooled RRs was explored by use of chi-squared tests. Reported P values are two-sided.

RESULTS

Thirty-one studies were identified and evaluated. The proportion of breast tumors expressing MDR1/gp170 in all of the studies was 41.2%, but there was substantial heterogeneity in the values across individual studies (P<.0001). Regression analyses demonstrated that a considerable portion of the observed heterogeneity was a consequence of the change, over time, from RNA hybridization-based assays to immunohistochemistry-based assays of MDR1/gp170 expression. Measuring MDR1/gp170 expression before versus after chemotherapy and use of cytotoxic drugs that are not substrates for gp170 also contributed to the heterogeneity. Treatment with chemotherapeutic drugs or hormonal agents was associated with an increase in the proportion of tumors expressing MDR1/gp170 (RR = 1.77; 95% confidence interval [CI] = 1.46-2.15). Patients with tumors expressing MDR1/gp170 were three times more likely to fail to respond to chemotherapy than patients whose tumors were MDR1/gp170 negative (RR = 3.21; 95% CI = 2.28-4.51); this RR increased to 4.19 (95% CI = 2.71-6.47) when considering only patients whose tumor expression of MDR1/gp170 was measured after chemotherapy. MDR1/gp170 expression was not associated with lymph node metastases, estrogen receptor status, tumor size, tumor grade, or tumor histology.

CONCLUSIONS AND IMPLICATIONS

MDR1/gp170 expression in breast tumors is associated with treatment and with a poor response to chemotherapy. The data are consistent with a contributory role for MDR1/gp170 in the multidrug resistance in some breast tumors.

Expression of drug resistance proteins in breast cancer, in relation to chemotherapy

Drug resistance plays an important role in chemotherapy failure in breast cancer. We studied the expression of MDR1, MRP, LRP, DNA topoisomerases, p53 and Ki-67 in different groups of breast cancer patients in relation to chemotherapy. Tissues from 6 normal breasts and 20 primary operable, 40 locally advanced and 10 anthracycline-resistant metastatic breast cancers were assessed. Sequential samples of the same patient were available from 17 patients with locally advanced breast cancer undergoing neo-adjuvant chemotherapy and in 7 metastatic patients undergoing paclitaxel treatment. Protein expression was investigated by immunohistochemistry. Significantly higher protein expression was observed for Pgp, Ki-67 and p53 in the locally advanced breast cancers than in primary operable breast cancers. No other significant differences in protein expression were found among the 3 breast cancer groups. Expression of none of the markers that could be assessed (Pgp, MRP, LRP, p53 and Ki-67) in locally advanced breast cancer had predictive value for pathological response. Interestingly, after chemotherapy a significant decrease in percentage of Ki-67 positive tumor cells was observed, whereas the other markers did not vary substantially. Furthermore, considering all breast cancer samples, a cumulative dose of doxorubicin >400 mg/m2 inversely correlated with Ki-67 positivity. However, 2 patients with a pathological complete remission had only 5-10% Ki67-positive tumor cells before chemotherapy, indicating that Ki67 negativity itself is not responsible for chemoresistance. In conclusion, none of the known proteins related to multidrug resistance predicted response to chemotherapy in breast cancer, and resistant clones left behind generally had a low proliferation rate.

Differential expression of multidrug resistance gene product, P-glycoprotein, in normal, dysplastic and malignant oral mucosa in India

Multidrug resistance (MDR) in human cancer is often associated with over-expression of the mdr-1 gene, which encodes a 170-kDa transmembrane protein, termed P-glycoprotein (P-gp). We evaluated the immunoreactivity of P-gp in oral tissues at different stages of tumorigenesis in the Indian population by flow cytometry, using the MRK-16 monoclonal antibody, which recognizes an external epitope of P-gp. The expression of P-gp was studied in human oral normal tissues (12 cases), dysplastic lesions (13 cases), primary untreated squamous-cell carcinomas (12 cases) and recurrent tumors (18 cases). Quantitative flow-cytometric analysis of P-gp expression showed a significant increase in P-gp levels in untreated primary oral tumors (p < 0.01) and in dysplastic lesions (p < 0.05) as compared with normal oral tissues. A marked significant increase in P-gp expression was observed in recurrent oral carcinomas as compared with normal oral tissues (p < 0.001) and dysplastic lesions (p < 0.01). Among recurrent tumors, a significant increase in the level of P-gp was observed in T4-stage tumors as compared with T3-stage tumors (p < 0.01). We conclude that P-gp is differentially expressed during oral tumorigenesis, and may be an indicator of the biological behavior of oral malignancies.

Primary breast cancer imaging with technetium-99m sestamibi and its relation with P-glycoprotein overexpression

The aim of this preliminary study was to evaluate retrospectively sestamibi scintigraphy in relation to the presence of the 170-kDa P-glycoprotein (Pgp), which represents an expression of multidrug resistance in patients with primary breast cancer. Fifteen women (age range 37-76 years) were referred for technetium-99m sestamibi scintigraphy because of suspicious breast lesions detected by mammography and ultrasonography, and subsequently assessed by fine-needle aspiration. Scintigraphy was performed 30 min following the injection of 500 MBq 99mTc-sestamibi. Three planar anterior and oblique images were obtained with the patient in the supine position. Excised tumours were assessed for cytosolic CA 15.3, oestrogen (OR) and progesterone (PR) receptors and c-erb B2 neu oncogene. Pathology revealed that only 13 of the 15 patients had malignant tumours. The two benign tumours were sestamibi-negative and Pgp-positive. Sestamibi scintigraphy was positive in 10 of the 13 malignant lesions (including nine of ten infiltrating ductal carcinomas). Two of the three lesions with false-negative scintigraphy were Pgp-negative; in one of these cases histology revealed an invasive lobular carcinoma and in the other, mucinous adenocarcinoma. The third false-negative lesion was a Pgp-positive infiltrating ductal carcinoma which was c-erb B2 neu-negative but CA 15.3-, OR- and PR-positive. This preliminary study confirms that the resistance to chemotherapy which may occur in patients with primary breast cancer can be a cause of negative sestamibi scintigraphy.

p53 and P-glycoprotein are often co-expressed and are associated with poor prognosis in breast cancer

Expression of both P-glycoprotein (P-gp) and mutant p53 have recently been reported to be associated with poor prognosis of breast cancer. The expression of P-gp is associated in vitro and in vivo with cross-resistance to several anti-cancer drugs. p53 plays a regulatory role in apoptosis, and mutant p53 has been suggested to be involved in drug resistance. Interestingly, in vitro experiments have shown that mutant p53 can activate the promoter of the MDR1 gene, which encodes P-gp. We investigated whether p53 and P-gp are simultaneously expressed in primary breast cancer cells and analysed the impact of the co-expression on patients prognosis. Immunohistochemistry was used to investigate P-gp expression (JSB-1, C219) and nuclear p53 accumulation (DO-7) in 20 operable chemotherapy untreated and 30 locally advanced breast cancers undergoing neoadjuvant chemotherapy with doxorubicin and cyclophosphamide. Double immunostaining showed that P-gp expression and nuclear p53 accumulation often occur concomitantly in the same tumour cells. A correlation between p53 and P-gp expression was found in all 50 breast cancers (P = 0.003; Fisher's exact test). P-gp expression, nuclear p53 accumulation, and co-expression of p53 and P-gp were more frequently observed in locally advanced breast cancers than in operable breast cancers (P = 0.0004, P = 0.048; P = 0.002 respectively. Fisher's exact test). Co-expression of p53 and P-gp was the strongest prognostic factor for shorter survival by multivariate analysis (P = 0.004) in the group of locally advanced breast cancers (univariate analysis: P = 0.0007). Only 3 out of 13 samples sequentially taken before and after chemotherapy displayed a change in P-gp or p53 staining. In conclusion, nuclear p53 accumulation is often associated with P-gp expression in primary breast cancer, and simultaneous expression of p53 and P-gp is associated with shorter survival in locally advanced breast cancer patients. Co-expression of P-gp and mutant p53 belong to a series of molecular events resulting in a more aggressive phenotype, drug resistance and poor prognosis.

Expression of MRP and mdr1 in human gastrointestinal cancer cell lines: a correlation with resistance against doxorubicin

The mRNA expression of mdr1 and MRP, each of which codes for a transport protein belonging to ATP-binding cassette superfamily and are reported to be responsible for multidrug resistance phenotype, were semi-quantified by RT-PCR in a panel of gastrointestinal cancer cell lines. Although the expression of MRP was predominant in esophageal cancer cell lines, expression of either or both of the genes was detected in all the cell lines tested. Expression of these two genes added together correlated significantly with chemosensitivity against doxorubicin, implicating that expression of both genes should be evaluated in the future analysis of multidrug resistance phenotype. The ID50 values for pirarubicin, although generally lower than the values for doxorubicin, correlated well with the latter, suggesting that the similar phenotype as that for doxorubicin might be responsible for drug resistance against this semisynthetic anthracycline glycoside.

Anthracycline resistance in breast cancer: clinical applications of current knowledge

Anthracyclines are highly effective antineoplastic agents for the treatment of breast cancer. Nevertheless, essentially all breast cancer patients have tumours which are intrinsically resistant or which develop resistance during the course of therapy. Clinical trials provide indirect information on the nature of anthracycline resistance and work in the basic sciences has demonstrated molecular mechanisms which play a role. Initial clinical attempts to exploit and translate these mechanisms to predict, and interfere with, anthracycline resistance have met with mixed success, and have not yet led to accepted clinical applications.

Expression of resistance-related proteins in nephroblastoma after chemotherapy

Tumor tissues of untreated and cytostatic-agent-treated patients with nephroblastomas were investigated for expression of resistance-related proteins (P-glycoprotein, glutathione S-transferase-pi, glutathione peroxidase and topoisomerase II) to ascertain whether resistance proteins are changed after treatment. Tumor tissue was analyzed by means of mRNA. Twenty-three children were treated with actinomycin D and vincristine for 4 to 8 weeks. Eight children received no preoperative chemotherapy. In untreated patients, no expression of P-glycoprotein was seen, whereas, in the patients who were treated with actinomycin D and vincristine, 12 out of 23 tumors showed increased P-glycoprotein expression (> mean value). Although we found no difference between treated and untreated tumors for glutathione S-transferase-pi, we found significant differences in the expression of glutathione peroxidase. In the 8 untreated patients, 7 tumors showed low glutathione peroxidase (< mean value) and one high (> mean value) glutathione-peroxidase-mRNA content. With treatment, 11 tumors expressed low levels and 12 tumors high levels of mRNA. A significant positive correlation between P-glycoprotein and glutathione peroxidase was found. In addition, of the 8 untreated patients, 2 had low topoisomerase-II expression, and 6 high expression. With treatment, the expression was reduced in 18 tumors, and only 5 tumors had high levels of this protein. These results were confirmed by PCR and immunohistochemistry.

Prognostic relevance of P-glycoprotein expression in breast cancer

BACKGROUND

P-glycoprotein (Pgp) expression has been reported to be associated with a poor prognosis in some malignancies such as neuroblastoma, soft tissue sarcoma and acute myeloid leukemia. The prognostic role of Pgp expression in breast cancer is still unclear. We investigated the expression of Pgp in primary and metastatic breast cancer tissues in relation to patient characteristics and treatment outcome.

PATIENTS AND METHODS

Pgp expression was evaluated in 92 primary and 12 metastatic breast cancers by the use of immunohisto/cytochemistry with three monoclonal antibodies (MAbs) (JSB-1, C219, MRK16), and an RNAse protection assay. Follow-up information was available for 77 primary breast cancer patients (median follow-up 42 months; range 2-63 months).

RESULTS

Concordance among the anti-Pgp MAbs varied, the highest being between JSB-1 and MRK16 (71%; p=0.002). Pgp expression was more frequent in metastatic disease (58%) than in primary breast cancer (29%) (JSB-1; p=0.055). Pgp expression as assessed with JSB-1 (univariate analysis; p<0.05) was associated with shorter overall survival (OS). Nineteen (21%) primary breast cancers had Pgp expression in fibroblasts in desmoplastic stroma and this did not correlate with Pgp expression in the tumor. The combination of Pgp-positive tumor cells and Pgp-expressing fibroblasts was the strongest prognostic factor for OS by multivariate analysis. Subgroup analysis suggested that Pgp expression was associated with a shorter OS in tamoxifen-treated patients, but not in those who received chemotherapy (most often CMF).

CONCLUSIONS

Pgp expression in tumor cells, and especially when accompanied by Pgp expression in fibroblasts in desmoplastic stroma, has prognostic value in primary breast cancer patients and is likely to be a marker of a more malignant phenotype. Pgp expression of tumor cells might play a role in tamoxifen resistance. These findings may have important implications for teh treatment of breast cancer patients, and warrant further prospective investigation in a larger patient population.

Erythromycin is ineffective against Listeria monocytogenes in multidrug resistant cells

Multidrug resistance of tumor cells is a well-known phenomenon in oncology. Among the substances excluded from the cells are not only antineoplastic drugs but also certain antibiotics, e.g. erythromycin. To prove the hypothesis that this might render infections with intracellular bacteria untreatable with these antibiotics we used erythromycin to treat intracellular infection of multidrug resistant (MDR) cells with Listeria monocytogenes. Erythromycin was unable to restrict the growth of L. monocytogenes in KBV-1 MDR cells in concentrations of up to 25 micrograms/ml. In contrast, 0.049 micrograms/ml of erythromycin were sufficient to restrict the growth of the bacteria in nonresistant KB 3-1 cells. When verapamil was added to the supernatant of KBV-1 cells, erythromycin regained its effectivity on L. monocytogenes multiplying in these cells. The fact that MDR cells may render intracellular bacteria inaccessible to certain antibiotics might have important implications for the persistence of these bacteria in the host and for the treatment of patients with genetically engineered MDR cells.

P-glycoprotein: clinical significance and methods of analysis

Multidrug resistance (MDR) is responsible for a decrease in sensitivity of tumor cells tumor cells to unrelated, naturally occurring anticancer drugs. This resistance is correlated with expression and activity of a membrane protein, P-gp 170, functioning as a drug-extruding pump. It has been well described in in vitro situations; however, the clinical detection and implications are not yet clear. Multiple detection assays have been developed based on the discovery of the MDR gene family and the corresponding protein. Southern, Northern, or Western blot analysis, S1 nuclease protection or PCR-based assays, immunohistochemical detection or functionality tests by flow cytometry have been used extensively. However, by use of these techniques on clinical material, both normal and malignant, contradictory results have emerged. The sensitivity and specificity of a certain technique are always limited by unavoidable parameters, for example, skill of the technician. Moreover, the complexity of the development of resistance against anticancer agents (external determinants), such as the diversity of tumor tissues, the simultaneous presence of other resistance mechanisms, and the low expression level, make MDR detection equivocal and can lead to contradictory results. Previous treatment influencing the MDR profile and inappropriate timing of the test make a possible correlation between MDR expression and chemotherapeutic resistance difficult to establish and can lead to discordant results. In this review, the need for proper criteria is stressed. No single detection technique provides the ideal test to detect MDR. Tandem testing could give more certainty, although small sample size limit this application. Formulation of a standard assay with better definition of a positivity is essential before clinical trials are started.

Expression of glutathione S-transferase-pi and sensitivity of human gastric cancer cells to cisplatin

BACKGROUND

The authors examined the correlation between the expression of glutathione S-transferase-pi (GST pi) and the sensitivity of gastric cancer to anticancer agents.

METHODS

In 62 human gastric carcinomas, the expression of GST pi was immunohistochemically evaluated, and sensitivity to the anticancer drugs, cisplatin (CDDP), doxorubicin (DXR) aclacinomycin A (aclarubicin), (ACR), 5-fluorouracil (5-FU), mitomycin C (MMC) and carboquone (carbazilquinon) (CQ) was examined using the in vitro succinate dehydrogenase inhibition test. The authors used the Chinese hamster ovary (CHO) cell line and its variant CDDP-resistant cell line C/CDP-2, and they analyzed the relationship among CDDP-sensitivity, mRNA expression, and immunohistochemical staining.

RESULTS

Immunohistochemically detected GST-pi-positive tumors were noted in 35 of 62 excised tumors. There was no significant correlation between GST-pi expression and clinicopathologic features or prognosis. The succinate dehydrogenase activity of each drug for tumors, with regard to negative or positive GST-pi, was 34.9 plus or minus 13.7% and 46.0 plus or minus 22.0% for CDDP, with a significant statistical difference (P < 0.05). However, there was no statistical difference for the other drugs tested. C/CDP-2 cells showed a lower sensitivity to CDDP, a higher expression of mRNA for GST pi and a stronger immunohistochemical staining than CHO cells.

CONCLUSIONS

The overexpression of GST-pi is significantly related to the sensitivity of gastric cancer to CDDP.

Expression of pi-glutathione S-transferase gene (GSTP1) in gastric cancer: lack of correlation with resistance against cis-diamminedichloroplatinum (II)

Class pi-glutathione S-transferase (GSTP-1) is one of several factors proposed to affect drug sensitivity to cisdiamminedichloroplatinum (II) (CDDP). It has also been investigated as a potential marker for the serodiagnosis of various types of cancers. In this study, attempts were made to quantify mRNA levels of the enzyme in healthy and cancerous gastric mucosa specimens, and to evaluate their significance in inherent drug resistance to CDDP. Thirty gastric cancer specimens were analysed by northern blotting with radiolabelled GSTP1 cDNA. Of these, the chemosensitivities of 22 specimens were evaluated by the succinic dehydrogenase inhibition (SDI) test. GSTP-1 mRNA was detected in all the specimens, with slightly increased, but non-significant expression in the neoplasms. Comparison of these drug sensitivities with results of northern blotting analysis showed no inverse correlation, as was expected from the widely investigated role of the enzyme in drug resistance.

Expression of glutathione-S-transferases alpha and pi in gastric cancer: a correlation with cisplatin resistance

Glutathione-S-transferase (GST) in one of several factors that are proposed to affect tumor sensitivity to anticancer drugs, including cisplatin (CDDP). Attempts are made herein to evaluate the significance of the enzymes in resistance to CDDP in clinical samples of gastric cancer. A total of 22 gastric cancer specimens, 16 of which were obtained with matching normal mucosae, underwent immunoblotting with polyclonal antibodies against GST-alpha and GST-pi. At the same time, the chemosensitivity of 15 gastric cancer specimens to CDDP was evaluated by the succinic dehydrogenase inhibition (SDI) test. The expression of GST-pi was detected in all the specimens, and its content in the neoplasms exhibited a significant positive correlation with that in the matched normal mucosae. The expression of GST-alpha was detected in 18 of 22 cancer specimens (82%), but its content in the neoplasms did not correlate with that in the matched mucosae. A comparison of the drug-sensitivity findings with the results of immunoblotting revealed a weak but interesting correlation between the protein levels of GST-alpha and CDDP resistance. The cellular content of GST-alpha correlated weakly with CDDP resistance in gastric cancer, and its quantification could contribute to prediction of the clinical effects of CDDP in patients with gastric cancer.

Expression of the multidrug-resistance gene product in untreated human breast cancer and its relationship to prognostic markers

The immunohistochemical expression of the 170-kDa permeability glycoprotein (P-gp) was investigated in 41 primary untreated breast carcinomas, using the monoclonal antibodies C219 and MRK16. DNA ploidy by flow cytometry and estrogen (ER) and progesterone receptor (PgR) contents were also determined. P-gp expression, as revealed by C219 or MRK16, was observed in 6 (14%) of the investigated cancers. P-gp expression had a tendency to occur in non-diploid, high-grade tumors as well as in patients with lymph node negative disease. However, except for lymph node status, these associations were not statistically significant. No positive statistical relationships were observed between other prognostic parameters (age, tumor size, and receptor status) and P-gp expression. Considering the great heterogeneity observed in previous studies and the low expression of P-gp observed hereby, the utility of P-gp immunostaining as a guide for therapy planning in patients with breast cancer remains uncertain.

Glutathione S-transferase expression in benign and malignant ovarian tumours

Glutathione S-transferase sub-types alpha, mu and pi were assessed by immunocytochemistry in 109 biopsies of ovarian tissue, comprising malignant epithelial tissue in 86 cases and tissue of ovarian origin considered to be normal in 23. Glutathione S-transferase pi was the most prevalent, being present in all except one malignant epithelium studied and 83% of non-malignant tissue. There were no significant differences in the overall distribution of positive staining for alpha, mu and pi in the malignant and non-malignant biopsies, although the intensity of staining was greater in the malignant epithelium. Stromal staining was in general more pronounced in the malignant biopsies, and this was particularly prominent in the case of the alpha sub-type. Positive staining was seen more frequently in the less well-differentiated tumours, and a diffuse cytoplasmic pattern was the most common observation in tumours of moderate and poor differentiation. There was no significant association between survival and the presence or absence of sub-type staining of alpha and mu sub-type. For the sub-type pi, patient survival was found to correlate with the intensity of staining (on a 0-(+++) scale). Those patients showing resistance to cytotoxic chemotherapy were found to have a higher intensity of staining for GST pi than responding patients.

Response to adjuvant chemotherapy in primary breast cancer: no correlation with expression of glutathione S-transferases

Of 139 node-positive breast cancer patients treated with adjuvant chemotherapy, the pre-treatment levels of glutathione S-transferase (GST) classes alpha, mu and pi, were determined by immuno-quantification on Western blots in cytosols of the primary tumours. Their expression was studied with respect to cytosolic oestrogen-receptor, progesterone-receptor and cathepsin D levels, and to the length of disease-free survival. GST class pi was negatively correlated with oestrogen receptor and progesterone receptor, and positively correlated with cathepsin D. There was no correlation between GST isoenzymes and the length of disease-free survival. These data suggest that glutathione S-transferases are not useful as markers to predict the response to adjuvant chemotherapy in human breast cancer.

Differential effects of estrogen, tamoxifen and the pure antiestrogen ICI 182,780 in human drug-resistant leukemia cell lines

ICI 182,780, a potent, new steroidal antiestrogen without apparent agonist activity, appears to be a potent modulator of the classic multidrug resistance (MDR) phenotype in the CEM/A7, CEM/VLB100 and K562/VIN100 MDR cell lines. This reagent had no effect on the respective parental CCRF-CEM and K562 cell lines. The use of 1.25 microM ICI 182,780 resulted in a 6- to 7-fold decrease in doxorubicin resistance in the CEM/A7 and CEM/VLB100 cell lines. A dose-response effect was observed at ICI 182,780 concentrations of up to 5 microM. As compared with tamoxifen (TAM), ICI 182,780 was 2 and 4 times more effective in the K562/VIN100 and CEM/A7 cell lines, respectively. ICI 182,780 at 0.625 microM increased [3H]-daunomycin uptake (P < 0.0001) as effectively as 5 microM TAM in the resistant CEM/A7 line. Drug-efflux studies showed that 5 microM ICI 182,780 significantly decreased drug efflux as compared with 5 microM TAM (P < 0.0001). Estradiol (EST) at 10 microM increased doxorubicin resistance by 1.2-1.3 times in the CEM/A7 and CEM/VLB100 cell lines and significantly decreased drug accumulation (P = 0.002) and retention (P < 0.001) in the CEM/A7 cell line. However, the addition of 10 microM EST to 1-2 microM ICI 182,780 did not inhibit the ability of ICI 182,780 to modulate doxorubicin resistance in the two resistant cell lines. Using reverse-phase high-performance liquid chromatography (HPLC) to measure lipophilicity, we found no apparent association between the ability of ICI 182,780, TAM or EST to modulate resistance and their relative hydrophobicity.

Expression of P-glycoprotein and anionic glutathione S-transferase genes in non-Hodgkin's lymphoma

Non-Hodgkin's lymphomas (NHL) are usually sensitive to chemotherapy. A certain percentage of patients are primarily or subsequently resistant to chemotherapeutic agents. Several biological mechanisms are implicated in this phenomenon, including multidrug resistance (mdr1) and glutathione S-transferase (GST pi). We investigated these two systems, using dot blot analysis, in 41 patients who presented NHL with advanced disease. There were 15 patients with low grade, 22 with intermediate grade, and 4 patients with high grade using the Working Formulation for Clinical Usage. Twenty-five patients had not been previously treated and 16 had been treated, including 13 with refractory disease. Eleven out of 25 (44%) patients overexpressed mdr1 mRNA at diagnosis as compared to 6/16 (38%) in relapse, corresponding to 6/13 (46%) refractory patients. Nine out of 25 (36%) patients overexpressed GST pi mRNA at the time of diagnosis, and 6/16 (50%) in relapse. These data indicate that overexpression of these two messengers is not acquired after treatment in NHL. Furthermore, there is no relationship between the stage or histological grade and the overexpression of these two markers. This study shows that mdr1 and GST pi gene expressions are independent of one another. With regard to the clinical response, our results also demonstrated a higher level of treatment failure in the group co-expressing the two transcripts, 6/8 (75%) patients died in progressive disease as compared to 9/15 (60%) patients without overexpression, and 2/8 (25%) vs 6/15 (40%) responded to treatment. On the other hand, overexpression of only one of the two mRNAs did not allow us to observe a difference in the clinical response. Since it seems that coexpression of the mechanisms of resistance present a better clinical impact, it would be of interest to analyse simultaneously different mechanisms involved in the resistance phenomenon in NHL.