Expression Of GST-pi Research Articles

A study on diagnosis of oral squamous cell carcinoma (oral SCC) by glutathione S-transferase-pi (GST-pi)

The purpose of this study was to estimate the usefulness of plasma GST-pi in diagnosis of oral SCC and to confirm the expression and localization of GST-pi in human oral SCC. Plasma GST-pi levels of 109 untreated oral SCC cases, 47 recurrent oral SCC cases and 36 healthy controls were measured by the sandwich enzyme-immunoassay (EIA) system. Human oral SCC and human oral SCC cell lines (HSC-3, HSC-4) were examined immunohistochemically and by the immunoelectron microscopic technique. The results were as follows: 1. The cut off level was 30.0 ng/ml (mean+2 S.D.). There was a statistically significant difference between the mean plasma GST-pi levels in oral SCC (both untreated and recurrent cases) and controls (p < 0.001). 2. The positive rate of GST-pi was 63.3% in untreated cases and 68.1% in recurrent cases. 3. There was no significant correlation between plasma GST-pi levels and each clinical factor. 4. The positive rates of plasma GST-pi were compared with those of serum SCC antigen in oral SCC. Plasma GST-pi was 62.9%, while serum SCC antigen 22.2%. 5. From immunohistochemical observation, GST-pi positive staining was evident in the cytoplasm and nucleus of oral SCC. 6. By immunoelectron microscopy, GST-pi was confirmed to be in the mitochondria and the inter-chromatinic regions of the nucleus.

Pi-class glutathione S-transferase: regulation and function

Our laboratory has been involved in the study of Glutathione S-transferase pi (GST pi) for many years, both in terms of regulation of gene expression and in trying to understand the endogenous function(s) of this enzyme and also what role it may play in the carcinogenic process [1]. Over-expression of GST pi has been associated with carcinogenesis and the development of many different human tumours, for example testis [2], ovarian [3] and colorectal [4] and is often inversely correlated with prognosis or patient survival [5, 6]. In addition, GST Pi has been implicated in the acquisition of antineoplastic drug resistance [7–9]. In order to study the transcriptional regulation of this gene, we have utilised a multi-drug resistant derivative (VCREMS) of the human mammary carcinoma cell line, MCF7, in which GST P1 mRNA and protein are significantly elevated in the absence of gene amplification [10–13]. Interestingly, we have recently reported the discovery of polymorphisms at the GSTP1 locus, resulting in two alleles GSTP1a and GSTP1b. In the study, the GSTP1b allele was found with increased frequency in bladder and testicular cancer, while the GSTP1a allele was significantly decreased in cases of prostate cancer [14]. In an attempt to elucidate the endogenous role(s) of GST pi, we have used homologous recombination in embryonic stem (ES) cells to inactivate both murine GST Pi genes and create a mouse strain completely deficient in the expression of this enzyme. This provides us with a unique animal model with which to study the effects of the absence of GST pi expression on the metabolism and pharmacokinetics of xenobiotics.

Biological indicators of survival in patients treated by surgery for squamous cell carcinoma of the oral cavity and oropharynx

Squamous cell carcinomas of the head and neck are a heterogeneous group of tumours with regard to anatomical site, natural history and response to various treatments. Assessment of the role of biomarkers as indicators of prognosis or response to treatment is thus complex. In the last decade, different biomarkers have been investigated in the search for objective and reproducible indicators of prognosis. In 69 squamous cell carcinomas of the oral cavity or oropharynx from patients treated with radical surgery alone, we determined cell kinetics, evaluated as in vitro 3H-thymidine labelling index (TLI), p53, bcl-2 and glutathione S-transferase pi (GST pi) expression, by using immunohistochemical methods. The biological variables were unrelated to one another or to established clinical and pathological prognostic factors. Univariate analysis showed that a low proliferative activity was associated to a significantly higher risk of death than that observed in patients with a high TLI, whereas p53, bcl-2 and GST pi expression did not provide prognostic information. Multivariate analysis showed that cell proliferation, gender and nodal status retained their clinical relevance. In the subset of node-negative patients, TLI and p53 expression were indicators of survival. Moreover, the combined analysis of TLI and p53 expression identified a subgroup of node-negative patients with slowly proliferating and highly p53-expressing tumours who died within 1 year of radical surgery. These results indicate that in patients with operable oral cavity and oropharyngeal cancer, biomarkers can provide important information on clinical outcome.

DIFFERENTIAL CARCINOGENICITY OF BENZO[a]PYRENE IN MALE AND FEMALE CD-1 MOUSE LUNG

Benzo[a]pyrene (BaP) is known to induce tumors in lung, forestomach, and skin in experimental animals. Earlier studies have suggested that glutathione S-transferase n (GST pi) is involved in the detoxification of the “ultimate” carcinogenic metabolite of BaP, 7p, 8a-dihydroxy-9a, IO(x-oxy-7tBt9tIO-tetrahydrobenzo[a]pyrene (BPDE). The constitutive expression of GST pi in the liver of the male CD-1 mouse is higher than that of the female, and BHA has been shown to preferentially induce GST pi in the female as compared with the male mouse. The present studies were therefore designed to compare the susceptibility of male and female CD-I mice to the carcinogenic effects of BaP and the protective effect of BHA. Results of these studies show that the female CD-1 mice are more susceptibile to the carcinogenic effect of BaP than the males and that the attenuation of BaP-induced carcinogenesis by BHA appears to be restricted only to the females.

Selective and synergistic activity of L-S,R-buthionine sulfoximine on malignant melanoma is accompanied by decreased expression of glutathione-S-transferase.

L-buthionine-S,R-sulfoximine (BSO) selectivley inhibits glutathione (GSH) synthesis. Malignant melanoma may be uniquely dependent on GSH and its linked enzymes, glutathione S-transferase (GST) and GSH-peroxidase, for metabolism of reactive orthoquinones and peroxides produced during melanin synthesis. We compared the in vitro effects of BSO on melanoma cell lines and fresh melanoma specimens (n = 118) with breast and ovarian cell lines and solid tumors (n = 244). IC50 values (microM) for BSO on melanoma, breast and ovarian tumor specimens were 1.9, 8.6, and 29, respectively. The IC90 for melanoma was 25.5 microM, a level 20-fold lower than steady state levels achieved clinically. The sensitivity of individual specimens of melanoma correlated with their melanin content (r = 0.63). BSO synergistically enhanced BCNU activity against melanoma cell lines and human tumors. We followed GSH levels, GST enzyme activity, GST isoenzyme profiles and mRNA levels after BSO. BSO (50 microM) treatment for 48 hr resulted in a 95% decrease in ZAZ and M14 melanoma cell line GSH levels, and a 60% decrease in GST enzyme activity. GST-mu protein and mRNA levels were significantly reduced in both cell lines. GST-pi expression was unaffected. These data suggest that BSO action on melanoma may be related to GSH depletion, diminishing the capacity to scavenge toxic metabolites produced during melanin synthesis. We report here for the first time that BSO enhancement of alkylator action may be related in part to down regulation of GST. BSO may be a clinically useful adjunct in the treatment of malignant melanoma.

Detection and significance of glutathione-S-transferase pi in osteogenic tumors of dogs

In this study we describe a relationship between the percentage of tumor cells staining positive for GST pi and the response to cisplatin treatment in dogs with appendicular osteosarcoma. Clinical resistance to platinum compounds has been attributed to tumor cell resistance to the drug. An overexpression of glutathione-S-transferase pi has been implicated in the resistance of tumor cells in vitro to cisplatin. In this study, the relative concentration of GST pi was quantified immunohistochemically in formalin-fixed, paraffin-embedded histologic specimens obtained from dogs with appendicular osteosarcoma prior to cisplatin treatment. The percentage of tumor cells staining positive for GST pi was compared with patient response (remission and survival times) following treatment. Those osteosarcoma-bearing dogs having a low pre-treatment tumor expression of GST pi (<50%; n=13) had a significantly longer (p <0.01) median remission and survival time (24.0 and 33.7 weeks, respectively) than those dogs with a high pre-treatment tumor expression of GST pi (>50%; n=8; median remission and survival times 14.2 and 24.0 weeks, respectively). The relative staining of GST pi in primary canine bone tumors has therapeutic importance and warrants further evaluation as a therapeutic model for human osteosarcoma.

Overexpression of glutathione S-transferase pi messenger RNA and its relationship to gene amplification in head and neck squamous cell carcinoma.

Human glutathione S-transferase pi has been known to be a good marker for several tumor types because of the high frequency with which it is overexpressed. In order to determine whether GST pi is useful as an indicator for head and neck cancers, expression of GST pi was investigated by Northern analysis. Overexpression of mRNA was detected in 9 of 36 primary head and neck squamous cell carcinomas. To examine the relationship between overexpression and amplification of GST pi gene, Southern analysis was performed on all samples. Only 3 of the 36 tumors showed amplification GST pi genes, indicating that gene amplification may not play a key role in GST pi mRNA overexpression in these cancers.

Biological predictors of response to radiotherapy in cervical carcinomas

On 21 patients with T1b-T3b tumours subjected to external radiotherapy and brachytherapy, the expression of P53 and glutathione S-transferase pi [GST-pi], immunohistochemically detected, the S-phase cells fraction (H-3-thymidine labeling index, TLI) and DNA content evaluated by image analysis were determined on biopsies before and after the first 10 Gy. P53 accumulation was reduced in 60% of P53-overexpressing tumours and not induced in P53-negative tumours, GST-pi was induced in about 40% of pretreatment GST-pi-negative cases, TLI was reduced in 70% of the cases regardless of pretreatment values, and DNA profiles remained unchanged in two-thirds of the cases. P53 accumulation was a predictor of 3-year relapse-free survival after radiotherapy, followed by GST-pi expression, whereas TLI did not influence prognosis.

Examination of multidrug resistance in cell lines and primary breast tumours by flow cytometry.

The aim of this study was to measure multidrug resistance (MDR) by flow cytometry and quantify the expression of P-glycoprotein (using antibody) glutathione transferase (using alpha-GSTpi antibody) in alpha-JSB-1 and alpha-GSTpi of a series of cell lines and primary breast cancers, and to assess the relationship between these MDR proteins and a selection of oncogene and prognostic markers in breast cancer. Flow cytometry was performed using permeabilised cells stained with fluorescent antibodies using well-established methods. Antibody staining was confirmed for JSB1, but not GSTpi by use of known positive and negative controls. No correlation was seen when comparing the number of molecules of alpha-JSB-1 with alpha-GSTpi (P = 0.1, r2 = 0.4, n = 14) using a selection of cell lines. Examination of 45 breast tumours for expression of JSB-1 and GSTpi revealed a significant association between these two antibodies (P < 0.00001, r2 = 0.5, n = 45). On examining the breast tumours, alpha-JSB-1 showed a positive association with c-erbB-2 (P = 0.003), c-myc (P = 0.0004) and c-jun (P = 0.02) but not ER or EGF-R expression. alpha-GSTpi showed a positive association with c-erbB-2 (P = 0.03) and c-myc (P = 0.0004) but not ER, EGF-R or c-jun. Flow cytometric MDR levels were not related to tumour grade or axillary node status. In solid tumours, a relationship between the two antibodies used has been clearly demonstrated, however, specificity of alpha-GSTpi is questioned. Both antibodies show an association with c-erbB-2, which is associated with poor prognosis and with c-myc which is involved in cell cycling and differentiation. Monitoring MDR markers (Pgp) using this methodology may be useful for evaluation of prognosis in breast cancer.

PS2 protein: a marker improving prediction of response to neoadjuvant tamoxifen in post-menopausal breast cancer patients.

Tamoxifen as sole initial therapy is gaining importance in the management of post-menopausal breast cancer patients. Age oestrogen (ER) and progesterone (PR) receptor status are accurately considered to select patients for hormonal treatment. However, additional markers are needed. By immunohistochemistry (IHC), we studied tumour expression of ER, PR, pS2, c-erbB-2 and glutathione S-transferase pi (GST pi) on initial core biopsies of 208 post-menopausal patients with a non-metastatic invasive ductal carcinoma, treated by neoadjuvant tamoxifen therapy. A good response to tamoxifen was defined as tumoral regression > or = 50% (110 patients). Relationship between response and age, tumour size, T, N, histological grade, ER and PR contents evaluated by radioimmunoassay, ER, PR, pS2, c-erbB-2 and GST pi expression evaluated by IHC were studied. Univariate and multivariate analysis showed that tumoral regression was linked only to pS2 (P = 0.004) and ER (P = 0.018) IHC expression. According to the immunohistochemical profile, three groups could be defined: pS2- and ER-positive tumours, pS2- or ER-positive tumours and pS2- and ER-negative tumours with response rates of 60%, 45% and 8% respectively. Although prospective studies are needed to confirm these results, we conclude that pS2 and ER immunohistochemical status are useful tools for predicting tumour regression with neoadjuvant tamoxifen in post-menopausal breast carcinoma patients.

Expression of multidrug resistance-related genes (mdrl, MRP, GST-pi and DNA topoisomerase II) in urothelial cancers.

To characterize the multidrug resistance (MDR) phenotype in human urothelial cancers, the expression levels of four MDR-related genes (multidrug resistance, mdrl; multidrug resistance-associated protein, MRP; glutathione S-transferase-pi, GST-pi; and DNA topoisomerase II, topo II) were analysed in urothelial cancers. Fifty-two tumour tissue and three normal urothelial mucosa samples were obtained from 44 patients with urothelial cancers. The expression of each gene was analysed with a reverse-transcription polymerase chain reaction (RT-PCR) method using beta 2-microglobulin (b2m) mRNA as an endogenous control. Levels of expression were expressed as the ratio of the specific products of the target gene to those specific to b2m. In primary urothelial cancer tissues, the mean (SD) expression of mdrl, MRP, GST-pi and topo II relative to b2m expression were 0.067 (0.061), 0.27 (0.23), 0.35 (0.31) and 0.12 (0.05), respectively. The mean expressions of MRP and GST-pi were higher than those of mdrl and topo II. The mean ratios of mdrl/b2m, MRP/b2m, GST-pi/b2m and topo II/b2m in normal urothelial mucosa were 0.06 (0.03), 0.12 (0.09), 0.30 (0.32) and 0.14 (0.01), respectively. There was no significant association of the expression of each gene with either the grade or extent of the primary tumour. The level of MRP expression in each sample was correlated significantly with the expression of mdrl and GST-pi in the urothelial cancers (r = 0.637 and 0.537, respectively). Chemotherapy did not markedly influence the induction of expression of the MDR-related genes, except for one case in which mdrl expression was 15 times greater than before chemotherapy. The expression of GST-pi in the patients not receiving chemotherapy was significantly higher than in those that did. These results suggest that the activation of MRP and GST-pi expression occurs during the tumorigenesis of urothelial cancers and that it may confer de novo and acquired drug resistance on urothelial cancers. These results should provide further insight into the complex role postulated for MDR-related genes in chemotherapy, carcinogenesis and tumour progression.

Glutathione S-Transferase-pi Expression in Prechemotherapy and Postchemotherapy Tumor Samples from Patients with Locally Advanced Breast Carcinomas

Abstract: Early local disease recurrence and distant metastasis remain major problems in the management of locally advanced breast carcinoma (LABC). Glutathione S-transferase of the pi class (GST-pi) has been implicated as a potential prognostic predictor for breast carcinomas, and its expression has been reported in 40–70% of untreated human primary breast cancers. We examined GST-pi expression by immunohistochemis-try technique in 45 prechemotherapy biopsy samples and 26 postchemotherapy resection samples from patients with LABC and evaluated its relationship with response to treatment, disease recurrence, and other known prognostic factors. GST-pi expression was present in 56% and 58% of prechemotherapy and postchemotherapy samples, respectively. Of 26 postchemotherapy tumor samples, 15 cases showed positive GST-pi staining; these 15 patients had shorter overall survival times compared with the 11 patients whose tissue samples showed negative staining (p = 0.053). Eight cases showed a marked increase (more than double) of GST-pi expression from prechemotherapy samples to postchemotherapy samples, however, the increase did not correlate with survival time, response rate, or relapse rate. Our findings suggest that evaluation of GST-pi expression after induction chemotherapy for LABC may allow selection of patients who might benefit from different chemotherapeutic regimens or adjuvant chemotherapy.?

Glutathione S-transferase and glutathione peroxidase are essential in the early stage of adriamycin resistance before P-glycoprotein overexpression in HOB1 lymphoma cells.

We have previously established Adriamycin-resistant HOB1 cell lines showing the multidrug resistance (MDR) phenotype. For further study, we analyzed the free-radical scavengers glutathione S-transferase (GST) and glutathione peroxidase (GPX) by enzyme assays and Northern blots. Three cell lines, HOB1/ADR0.1, HOB1/ADR1.0, and HOB1/ADR5.0, represented HOB1 cells resistant to 0.1, 1.0, and 5.0 microM Adriamycin, respectively. The mdr1 transcript was overexpressed in HOB1/ADR0.1 cells, and the amount of its expression reached a maximum between HOB1/ADR1.0 and HOB1/ADR5.0 cell lines. The increases in GST activity and GST-pi expression were observed only in high-level-resistant cell line (HOB1/ADR1.0 and HOB1/ADR5.0), which also showed increased GPX activity and expression. For investigation of the cytotoxic effect of Adriamycin on HOB1 cells prior to the mdr1 overexpression, an appropriate number of parental HOB1 cells were treated with 0.1 microM Adriamycin for 7 days, and the viable cells (HOB1/ADR) were isolated and subjected to analyses for mdr1, GST-pi, and GPX expression and for GST and GPX activity. In comparison with HOB1/ADR0.1 cells, HOB1/ADR cells did not show mdr1 overexpression but had significant increases in the activity and expression of GST and GPX. The current study suggests that in the early phase of Adriamycin treatment, GST and GPX are more important than P-glycoprotein for the development in HOB1 cells of resistance against Adriamycin.

Glutathione S-Transferase and Multidrug-Resistant Phenotype in Transitional Cell Carcinoma of the Bladder

To asses the role of expression of resistance phenotypes in treatment failure in patients with invasive transitional cell carcinoma of the urinary bladder, since P-glycoprotein and glutathione S-transferase pi (GST) expression are implicated in resistance to various chemotherapy agents in different tumors. Tumor samples from P-glycoprotein and GST-pi were analyzed by immunohistochemistry. P-glycoprotein and GST-pi were found in 35.7 and 42.9% of the samples, respectively. In 21.4% of the samples there was simultaneous expression of both proteins. No significant impact on prediction of tumor behavior was evident on statistical analysis by any one of the protein expressions. Drug resistance in transitional cell carcinoma may be through different mechanisms. Although the small sample size of this study precludes firm conclusions, the assessment of P-glycoprotein or GST-pi expression appears to be of little value as a predictor of response to chemotherapy in this group of tumors.

The immunohistochemical localization of drug-metabolizing enzymes in prostate cancer.

The major groups of enzymes involved in activating and detoxifying therapeutic drugs, not least several anti-cancer drugs, include the cytochromes P450 (P450s), epoxide hydrolase, and glutathione S-transferases (GSTs). The expression of these enzymes in malignant tumours is one possible mechanism of anti-cancer drug resistance. This study has investigated the presence, cellular localization, and distribution of drug-metabolizing enzymes in prostate cancer. The P450 subfamilies CYP1A, CYP2C, and CYP3A were present in 63, 25, and 61 per cent of tumours, respectively. Epoxide hydrolase was identified in 96 per cent of tumours. GST-alpha and GST-mu were expressed in 29 and 41 per cent of tumours, respectively, while there was no immunoreactivity for the pi form of GST. The absence of GST-pi in prostate cancer contrasts with the frequent expression of GST-pi observed in other types of malignant tumour. In non-neoplastic prostatic epithelium, there was expression of CYP1A, CYP2C, epoxide hydrolase, and the different forms of GST, while there was no apparent immunoreactivity for CYP3A.

Immunohistochemical Expression of Glutathione S‐Transferase π (GST‐π) and Chemotherapy Response in Malignant Ovarian Tumors

To clarify the relationship between the expression of GST-pi and the therapeutic effects of high-dose combination chemotherapy with support by autologous bone-marrow transplantation (ABMT). Expression of GST-pi in tissue specimen were analyzed by indirect immunoperoxidase methods using anti-GST-pi polyclonal antibody. (1) Eighteen of 36 cases (50%) tested prior to administration of any chemotherapeutic agents were found to be positive in terms of immunohistochemical expression of GST-pi in the cancer cells. (2) The rate of GST-pi expression was elevated following administration of cisplatin, adriamycin, and cyclophosphamide, which suggests that administration of such anti-cancer agents is capable of inducing expression of GST-pi in cancer cells. (3) GST-pi negative patients exhibit better survival rates than do GST-pi positive patients (Kaplan Meier method: p < 0.001). Analysis of GST-pi obtained at primary surgery can serve as a valid marker in anticipating chemotherapeutic effects and long-term prognoses.

Glutathione S transferase Pi is a powerful indicator in chemotherapy of human lung squamous-cell carcinoma.

We immunohistochemically investigated the expression of glutathione S transferase pi (GST- pi) and clarified the correlation between GST-pi and the results of chemosensitivity testing on the tissue of primary human squamous-cell carcinoma of the lung. The expression of GST-pi was evaluated in 105 cases and their level of chemosensitivity was estimated by the in vitro succinate dehydrogenase inhibition test for cisplatin, Adriamycin, cyclophosphamide, mitomycin C, vindesine and fluorouracil. Tumors in which 25% and more of the cells stained for GST-pi were classified as having a high GST-pi expression, while those tumors demonstrating less than 25% of the cells staining for GST-pi were considered to have a low expression GST-pi. The percentage of high GST-pi was 52% (53 of 105) while that of low GST-pi was 48% (52 of 105). No significant correlation between the expression of GST-pi and clinicopathologic factors was observed, while no significant difference in the survival of the two groups was found either. An increase in succinate dehydrogenase activity was recognized in the high-GST-pi group compared with the low-GST-pi group for each anticancer drug; however, no statistical significance was seen except for cisplatin. In the cases with adjuvant combination chemotherapy using cisplatin after a complete resection, all cases demonstrating a relapse were associated with a high GST-pi. These findings thus indicate that an overexpression of GST-pi is related to the resistance to cisplatin in human lung squamous-cell carcinoma. It is therefore important to select carefully the optimal anticancer drug for high-GST-pi cases.

DIFFERENTIAL EXPRESSION OF GLUTATHIONE-S-TRANSFERASE ISOZYMES IN MURINE AND HUMAN SKIN TUMORS

Glutathione S-transferases (GSTs) are a family of widely distributed multifunctional enzymes present in a number of organs and species. GSTs participate in the detoxification of a wide variety of xenobiotics and their metabolites. Mammalian GSTs have been grouped into three major classes alpha, mu and pi. The differential expression of specific GST isozymes has been reported as a phenotypic marker for the preneoplastic lesions and neoplastic tissues in liver and other extracutaneous organs of rat and other species including humans. However, the expression of GST isozymes in skin cancer is not known. In the present study, therefore, employing Western blot analysis, we assessed the GST isozyme expression in experimentally-induced murine skin tumors and clinically obtained human skin basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs). As compared to normal murine skin showing high levels of GST-pi, significantly lower expression of GST-pi was observed in murine skin papillomas and carcinomas induced chemically in SENCAR mice or by chronic ultraviolet B radiation in SKH-1 hairless mice. Similar results were also observed for GST-mu isozyme. On the other hand, compared to normal murine skin where the expression of GST-alpha isozyme was not detectable, significant levels of this GST isozyme were observed in all the murine skin papillomas and carcinomas. In case of human skin BCCs and SCCs, variable GST isozyme patterns were evident, however in each case, GST-pi was found to be significantly underexpressed as compared to that in skin from healthy subjects. Our results suggest that altered phenotypic expression of GST isozymes may be a useful marker for skin cancer.

RESISTANCE FACTORS AND PROLIFERATIVE ACTIVITY IN CHILDHOOD ACUTE NONLYMPHOBLASTIC LEUKEMIA

Thirty-four children with newly diagnosed acute nonlymphoblastic leukemia were analysed for the expression of P-glycoprotein (P-170), glutathione S-transferase-pi, (GST-pi) topoisomerase II (Topo II) and the proliferation antigen Ki-67 by the streptavidin-biotin-peroxidase method. Overexpression of P-170 was present in 26 cases (76%) and GST-pi overexpression was seen in 11 patients (32%). Down regulation of Topo II was found in 16 patients (47%) and Ki-67 positive cells (>5%) were detectable in 9 patients (26%). The remission rate was not influenced by P-170 or GST-pi expression, whereas patients with down regulation of Topo II or low Ki-67 expression had lower remission rates. The data were not significant. The probability of continuous first remission (CR) was lower in patients with P-170 expression (p=0.09). A significantly lower probability of CR was also seen in patients with low proliferative activity (p=0.03, log-rank test). The expression of the resistance proteins and the proliferative activity were found to be independent of the clinical parameters age, sex, FAB-type, and initial white blood cell count.

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.