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H I Scher

Publications and source records attributed to H I Scher.

At least 73 records · Page 4Linked to original sources
PubMed1998

Expression of potential target antigens for immunotherapy on primary and metastatic prostate cancers.

Defining the expression of tumor-associated antigens on primary and metastatic prostate cancer is the crucial first step in selecting appropriate targets for immune attack. In this study, the distribution of the tumor-associated antigens GM2, Tn, sTn, Thompson-Friedenreich antigen (TF), Globo H, Le(y), MUC1, MUC2, MUC3, MUC4, MUC5AC, MUC5B, MUC7, carcinoembryonic antigen, beta chain of human chorionic gonadotropin (hCG beta), HER2/neu, PSMA, and KSA on primary and metastatic prostate cancer and 16 types of normal tissues was compared by immunohistochemistry, using a panel of well-characterized monoclonal antibodies. Our results show that GM2, KSA, and MUC2 were strongly expressed on 8 or 9 of 9 metastatic prostate cancer biopsy specimens and, with PSMA, hCG beta, TF, Tn, and sTn, on 8 or more of 11 primary prostate cancer specimens. Tn, MUC1, and PSMA were expressed on 4-6 of 9 metastatic specimens. The remaining antigens were expressed on no more than three of nine metastatic specimens. Normal tissues were also tested with all antibodies. With regard to the eight antigens most widely expressed on prostate cancers, PSMA was not expressed significantly on any of the normal tissues except prostate epithelium. Tn, sTn, hCG beta, and MUC2 were detected on up to 3 of 10 types of normal epithelia. GM2, TF, MUC1, and KSA were more broadly distributed on normal epithelia, all primarily at the secretory borders. STn, KSA, and hCG beta were also detected in the testis, and GM2 was expressed on gray matter of brain. From the 30 antigens that we have screened, this study provides the basis for selecting GM2, TF, Tn, sTn, hCG beta, MUC1, MUC2, KSA, and PSMA as target antigens for specific immunotherapy of prostate cancer.

Amino Acid Sequence↗
PubMed1998

Interferon-gamma and monoclonal antibody 131I-labeled CC49: outcomes in patients with androgen-independent prostate cancer.

To assess the tumor targeting, safety, and efficacy of monoclonal antibody 131I-labeled CC49 in patients with androgen-independent prostate cancer, 16 patients received 75 mCi/m2 of the radiolabeled antibody after 7 days of IFN-gamma pretreatment. Sequential tumor biopsies in three patients showed a median 5-fold (range, 2-6-fold) increase in the proportion of cells staining positively for the TAG-72 antigen, whereas one showed a decrease in staining. Fourteen patients received 131I-labeled CC49, whereas 2 showed a disease-related decrease in performance status, precluding antibody treatment. The antibody localized to sites of metastatic androgen-independent prostate cancer in 86% (12 of 14; 95% confidence interval, 57-95%) of cases. Both osseous and extraosseous sites were visualized, and in six (42%) patients, more areas were visible when the radioimmunoconjugate was used than were apparent when conventional scanning techniques were used. The localization of the conjugate in the marrow cavity was usually a site not visualized by the radionuclide bone scan, in which the isotope localizes primarily to the tumor-bone interface. The dose-limiting toxicity was thrombocytopenia because five (36%) patients showed grade IV and seven (50%) showed grade III effects. In addition, six (42%) patients, four of whom were hospitalized, showed a flare in baseline pain, and four showed a decrease in pain. No patient showed a >50% decline in prostate-specific antigen, although radionuclide bone scans remained stable in four cases for a median of 4 months. The results are consistent with dosimetry estimates showing that the delivered dose to tumor was subtherapeutic and suggest that approaches that exclusively target the bone tumor interface or the marrow stroma may be unable to completely eradicate disease in the marrow cavity. For CC49, improving outcomes would require repetitive dosing, which was precluded by the rapid development of a human antimouse antibody response.

Aged↗
PubMed1998

A new parameter for measuring metastatic bone involvement by prostate cancer: the Bone Scan Index.

In this report, we describe a method for quantitative bone scan interpretation (the Bone Scan Index or BSI) in advanced prostate cancer. The BSI estimates the fraction of the skeleton that is involved by tumor, as well as the regional distribution of the metastases in the bones. The purpose of this report is to describe the development and validation of this method in terms of reproducibility and the application of BSI for determining extent of disease and monitoring disease progression. We analyzed 263 bone scans from 90 patients being studied under four protocols at Memorial Sloan-Kettering Cancer Center for progressive, androgen-independent prostate cancer (AIPC), who had bone scans as a part of their work-up. We determined: (a) the intraobserver and interobserver variability of the BSI; (b) the comparison between a change in BSI and prostate-specific antigen (PSA); (c) the regional distribution of bony metastases in early stage D prostate cancer (<3% skeletal involvement); and (d) the rate of growth of bony metastases from prostate cancer. A cube root transformation of the percentage of involvement of the entire skeleton was used to stabilize the variance over the entire span of values (0-60% tumor involvement). The range of interobserver variability between readers was 0.2-0.5 times the cube root of the BSI (69 scans, 18 patients). Intraobserver variability was minimal when the same reader read the same scans after a 2-year interval, showing a correlation coefficient of 0.97 (reader 1) and 0.99 (reader 2), P < 0.001. There was a parallel rise in the BSI and the PSA in 24 patients (105 scans) treated for AIPC with hydrocortisone followed by suramin at PSA relapse (Pearson's moment correlation, 0.71). In a group of 27 patients with limited bone involvement by AIPC (i.e., <3% BSI), the distribution of early metastases was not random within the skeleton but was distributed in the central skeleton in a manner that matched the distribution of the normal adult bone marrow. Also, in a group of 21 patients (62 scans), the change in BSI as a function of time after diagnosis was explored graphically. The progression of bone scan changes in AIPC, from early involvement (<3%) to late involvement, was fitted to a Gompertzian equation. It showed a rapid exponential growth phase, with an estimated tumor doubling time of 43 days when the BSI was 3.3%. The change in BSI rapidly approached a more gradual slope as the percentage of skeletal involvement increased. The BSI provides a reproducible new parameter for quantitative assessment of bone involvement by AIPC. These results suggest that the BSI will be useful for stratifying patients entering treatment protocols for extent of tumor involvement of bone. Although further study is necessary, serial bone scan BSI appears capable of quantifying both the progression of bony involvement by tumor as well as the response to treatment.

Aged↗
PubMed1997

Expression and localization of aminopeptidase A, aminopeptidase N, and dipeptidyl peptidase IV in benign and malignant human prostate tissue.

BACKGROUND: Cell-surface peptidases are ectoenzymes which regulate the access of bioactive peptides to their receptors on cell membranes. Abnormalities in their expression and function result in altered peptide activity which contribute to neoplastic transformation and/or progression. METHODS: Expression of aminopeptidase A (APA), aminopeptidase N (APN, CD13), and dipeptidyl peptidase IV (DPP IV, CD26) was immunohistochemically examined in 20 benign and 33 malignant prostate tissues (19 primaries and 14 metastases). RESULTS: Benign prostatic stroma exhibited no APA, APN, or DPP IV immunoreactivity. Stromal cells surrounding prostatic carcinoma cells demonstrated increased APA expression in 24/33 (73%) of tumors. Benign prostatic epithelial cells strongly expressed APN and DPP IV but not APA. In contrast, APN was expressed in > 80% of tumor cells in 5/33 (15%) of specimens, heterogeneously expressed (20-80% of cells positive) in 4/33 (12%) of specimens, and minimally expressed or absent in 24/33 (73%) of tumor specimens, with a similar pattern of expression in primary and metastatic tumors. DPP IV was expressed by > 80% of tumor cells in 18/19 (95%) of primary prostate cancer specimens, but in only 7/14 (50%) of metastases. CONCLUSIONS: These data show that cell-surface peptidases are differentially expressed by normal prostatic stromal and epithelial cells, with increased expression of APA in the stroma surrounding prostate cancer cells, absent APN expression in most tumor cells, and a decreased frequency of DPP IV expression in metastatic tumors. Further studies will elucidate the biological effects of the presence or loss of cell-surface peptidases in the benign and malignant prostate.

Aged↗
PubMed1997

Prognostic significance of detection of prostate-specific antigen transcripts in the peripheral blood of patients with metastatic androgen-independent prostatic carcinoma.

OBJECTIVES: To evaluate the prognostic significance of reverse transcriptase polymerase chain reaction (RT PCR) detection of prostate-specific antigen (PSA) mRNA in relation to survival in patients with metastatic androgen-independent prostatic carcinoma (AIPC). METHODS: Peripheral blood from 122 men (64 from Memorial Sloan-Kettering Cancer Center [MSKCC] and 58 from the Dana Farber Cancer Institute [DFCI]) with metastatic (Stage D2) AIPC was analyzed for PSA mRNA using RT PCR. Forty-one controls without prostatic carcinoma were also evaluated. RESULTS: RT PCR positivity for PSA mRNA was present in 24 of the 64 (38%) patients seen at MSKCC and in 26 of the 58 (45%) patients followed at DFCI. All control individuals were PSA PCR negative. There was a significant correlation between RT PCR positivity and decreased survival in each of the Memorial and Dana Farber population (P = 0.028 and 0.039, respectively). Serum PSA (at time of blood collection for PCR) was not predictive of survival as a continuous variable in the MSKCC [P = 0.31] and the DFCI (P = 0.09) groups. RT PCR for PSA mRNA was found to be independent from and superior to serum PSA in predicting survival in both the MSKCC and DFCI populations (P = 0.048 and P = 0.027, respectively). CONCLUSIONS: The detection of PSA mRNA in the peripheral blood by RT PCR is a predictor of survival in patients with metastatic AIPC, and PCR is superior to a single serum PSA measurement. Further studies are needed to test the value of this factor in comparison to and coupled with other prognostic parameters.

Adult↗
PubMed1997

Steroid hormone withdrawal syndromes. Pathophysiology and clinical significance.

The steroid withdrawal syndrome has brought a new dimension to the treatment of advanced prostate cancer not only in the way we treat androgen-independent disease but also in terms of insights into the development of hormonal resistance. The data now confirm that 30% of cases have a meaningful subjective, biochemical, and objective response to the withdrawal of a steroid hormone as the first maneuver after primary hormonal therapy failure. Larger studies are needed to define further the withdrawal effect related to the other steroid hormone family members and to determine the objective response proportions. Although controversy surrounds the cause of the steroid withdrawal phenomenon, studies suggest that the androgen receptor plays a pivotal role. Molecular studies of the androgen receptors involving larger number of patients are paramount if we are going to develop a better understanding of the evolution of the withdrawal effect and hormone resistance.

Androgen Antagonists↗
PubMed1997

The antiandrogen withdrawal syndrome in relapsed prostate cancer.

Evolving data suggest that palliation of relapsed prostate cancer can be achieved by the selective discontinuation of agents that act via steroid hormone receptors. Clinical benefit has been observed following the withdrawal of flutamide (Eulexin, Schering-Plough International), bicalutamide (Casodex, Zeneca Ltd), oestrogens, progestational agents and retinoids. For patients with progression of disease while receiving these drugs, a period of observation after withdrawal should be considered before further therapy is initiated.

Androgen Antagonists↗
PubMed1997

Phase II trial of docetaxel in patients with advanced or metastatic transitional-cell carcinoma.

PURPOSE: A phase II trial of docetaxel was conducted to assess its efficacy and toxicity in patients with advanced transitional-cell carcinoma (TCC) who had failed to respond to prior cisplatin-based therapy. PATIENTS AND METHODS: Thirty assessable patients who had failed to respond to or relapsed after one prior cisplatin-containing regimen were treated with docetaxel 100 mg/m2 over 1 hour, every 21 days. All patients were premedicated with dexamethasone and diphenhydramine to reduce allergic reactions. Reductions of subsequent doses were made for severe hematologic toxicity. Prophylactic hematopoietic growth factors were not used. RESULTS: Four of 30 patients (13.3%; 95% confidence interval [CI], 3.8% to 30.7%) demonstrated a partial response (PR), with durations of response ranging from 3 to 8 months. The estimated median survival duration for all patients is 9 months (95% CI, 6 to 12 months) with a median follow-up time of 14 months (range, 1 to 27). Hematologic toxicity included anemia, thrombocytopenia, neutropenia, and febrile neutropenia. Nonhematologic toxicity included alopecia and mucositis. Fluid retention was not observed and cutaneous toxicity was mild and infrequent. Dose reductions were necessary for adverse events in 18 patients (60%). CONCLUSION: Docetaxel is an active single agent in previously treated patients with TCC of the urothelial tract. Therapy was well tolerated in this patient population but myelosuppression was frequent. Further study in previously untreated patients, both alone and in combination, is warranted.

Adult↗
PubMed1997

Phase II randomized trial of gallium nitrate plus fluorouracil versus methotrexate, vinblastine, doxorubicin, and cisplatin in patients with advanced transitional-cell carcinoma.

PURPOSE: A phase II randomized trial of gallium nitrate/fluorouracil (5-FU) versus dose-intense methotrexate, vinblastine, doxorubicin, and cisplatin (M-VAC) was performed in poor-risk patients with advanced urothelial tract tumors. The efficacy and toxicity of these regimens were compared. Assessment of dose-intense M-VAC as salvage treatment in patients who failed to respond to the gallium nitrate/5-FU regimen was also performed. PATIENTS AND METHODS: Thirty-four patients who had not received prior systemic chemotherapy were randomized to either arm of the study. All patients had one or more clinical features predicting a low likelihood of durable complete response to standard chemotherapy, ie, weight loss, visceral metastases, and low performance status. Gallium nitrate and 5-FU were each administered by continuous 5-day infusions every 28 days. M-VAC was recycled every 21 days, with prophylactic recombinant human granulocyte colony-stimulating factor (rh-G-CSF). RESULTS: Two of 17 patients (12%; 95% confidence interval [CI], 1.4% to 36.4%) had a major response to gallium nitrate/5-FU. Sixteen of 17 patients treated with M-VAC (94%; 95% CI, 71.3% to 99.8%) demonstrated a major response. Five of 12 patients who failed to respond to the gallium nitrate/5-FU combination responded to M-VAC as second-line therapy (42%; 95% CI, 15.2% to 72.3%). Median survival for the gallium nitrate and 5-FU arm was 19 versus 17 months for the M-VAC arm, with a median follow-up duration of 35 months (range, 2 to 51) for all patients. Dose-intense M-VAC was associated with a greater incidence of neutropenia and thrombocytopenia. CONCLUSION: Dose-intense M-VAC is superior to gallium nitrate/5-FU in poor-risk patients (P < .0001). Despite the overall high response rate, the median survival for patients with M-VAC remained unsatisfactory. Similar survival distributions were observed for patients who received investigational therapy followed by cisplatin-based therapy and patients treated with initial cisplatin-based therapy.

Adult↗
PubMed1997

Bicalutamide for advanced prostate cancer: the natural versus treated history of disease.

PURPOSE: To determine the therapeutic effects of bicalutamide 200 mg in patients with prostate cancers of different hormone sensitivities. METHODS: Patients with progressive prostate cancer were treated with bicalutamide 200 mg daily. Before treatment, patients' tumors were classified on the basis of prior hormone exposure and by serum testosterone levels into androgen-dependent and androgen-independent groups. Prior exposure to flutamide and response to flutamide withdrawal was also considered. Outcomes were reported independently on the basis of posttherapy changes in prostate-specific antigen (PSA), measurable disease, and radionuclide bone scans. RESULTS: Outcomes varied by prior hormone exposure as a higher proportion of patients with progression of androgen-dependent tumors showed posttherapy PSA decreases of more than 50% or more than 80%, measurable disease regression, and improvement on radionuclide bone scans than did patients with androgen-independent progression. Within the category of androgen-independent progression, clinical benefit was observed in patients who had previously progressed on flutamide, independent of the response to flutamide withdrawal. Patients who had progressed on a gonadotropin-releasing hormone (GnRH) analog alone had a low response proportion, whereas those who progressed after two or more hormone therapies did not respond. Overall, the drug was well tolerated. After progression on bicalutamide monotherapy, one third of patients with androgen-dependent progression responded to medical castration with a GnRH analog. CONCLUSION: Classifying patient tumors on the basis of prior hormone exposure permits a more precise estimate of the potential benefit of a specific hormone therapy for the individual patient. The precision is further increased by reporting the effects of a drug on each parameter of disease independently. The difference in outcomes for patients with androgen-independent progression suggests that the specific hormone therapy administered and the response to that therapy can influence the biology of the relapsing tumor and the sensitivity to subsequent therapies. The sensitivity to bicalutamide after progression on flutamide deserves further study.

Aged↗
PubMed1997

Neoadjuvant hormonal therapy plus surgery for prostate cancer. The MSKCC experience.

This article reviews the current status of neoadjuvant hormonal therapy (NHT) in the treatment of clinically localized prostate cancer. Although significant increases in the organ confined rate and similar marked decreases in the positive margin rate are found in patients receiving NHT, to date no difference in disease free survival rate, as determined by PSA values, can be shown. However, there is a suggestion (P = 10 ng/ ml when treated with NHT compared with controls. Given the prolonged natural history of prostate cancer, longer follow-up will be required before the value of NHT can be established.

Antineoplastic Agents, Hormonal↗
PubMed1997

Combined-modality therapy for bladder cancer.

Radical cystectomy remains standard management for patients with locally advanced T2 through T4, N0, M0 transitional cell carcinoma of the urinary bladder. Although radical cystectomy results in excellent local control, 50% or more of patients relapse. Studies have shown that multidrug cisplatin (Platinol)-based chemotherapy prolongs disease-free survival in 10% to 15% of cases and is superior to single-agent cisplatin. These studies led to the application of these regimens in conjunction with surgery and/or radiation therapy in an attempt to preserve bladder function. With this approach, the decision to leave the bladder in place, remove a portion (partial cystectomy), or perform a radical cystectomy is made after assessing the initial response to therapy. Results from neoadjuvant studies have shown that: major responses are observed in at least 50% of patients; bladder preservation can be achieved in 25% to 50%; a pathologic complete response predicts long survival; and patients with deeply invasive lesions (T3b to T4) usually are not candidates for bladder preservation. Whether overall survival is improved has been difficult to ascertain due to such issues as small sample size and case selection. Concurrently, newer surgical approaches with continent diversions have reduced, to some extent, the need for ileal conduits, a factor influencing the bladder preservation approach. Adjuvant chemotherapy, although less well studied, suggests a possible survival benefit for selected patients with a high likelihood of relapse. To optimize patients selection, new prognostic factors are necessary. Many biologic variables based on expression of tumor-related proteins are under study. Combined-modality therapy is not standard management for the majority of bladder-cancer patients. However, it is a viable alternative for those who are committed to preserving bladder function. Additional research is required to determine whether these approaches improve survival and to identify better markers of treatment outcome.

Carcinoma, Transitional Cell↗
PubMed1997

Relative contribution of normal and neoplastic cells determines telomerase activity and telomere length in primary cancers of the prostate, colon, and sarcoma.

Telomerase and telomere length are increasingly investigated as potential diagnostic and prognostic markers in human tumors. Among other factors, telomerase and telomere length may be influenced by the degree of tumor cell content in tumor specimens. We studied telomerase activity and telomere length with concomitant integration of histopathological data to determine whether both were influenced by the amount of tumor cells. We measured telomerase in 153 specimens: in 51 solid tumor blocks; in 51 cryostat sections; and in 51 adjacent normal tissues from patients with sarcoma (n = 10) and colorectal (n = 11) and prostate cancer (n = 30) using the sensitive and rapid detection telomeric repeat amplification protocol assay. Telomere length was determined by telomere restriction fragment Southern blot analysis. From cryostat sections, tumor cell infiltration was assessed. Telomerase activity was detected in all colorectal tumors and sarcomas, as expected. In primary prostate cancer, however, telomerase activity was less frequently observed (14 of 30, 47%). Moreover, a decreased intensity compared to colon cancer and sarcoma was evident (P < 0.001). The median tumor cell infiltration was significantly higher in sarcoma (65%) and colon (30%) compared to prostate cancer (5%; P < 0.001). There was a positive correlation between tumor cell infiltration and telomerase activity (r = 0.89; P < 0.001). Telomere restriction fragments in tumors were shorter compared to the normal tissues with peak differences in colon, sarcoma, and prostate of 1.8, 2.8, and 1 kilobase pairs, respectively (P < 0.002). Our data suggest the presence of a positive correlation between the degree of tumor cell content in human solid tumors and the level of telomerase activity detected. We demonstrated that the amount of tumor cells also affects telomere restriction fragment analysis. Therefore, with the predominance of normal cells in tumor specimens, telomerase activity measured may not reflect the malignant phenotype, and telomere loss may be underestimated. This phenomenon was most evident in prostate cancer. Our results will have implications for the future when telomerase activity and telomere lengths may be used for early screening, diagnosis, and prognosis determinations and when telomerase inhibitors are applied to clinical practice.

Adenocarcinoma↗
PubMed1997

Alterations affecting the p53 control pathway in bilharzial-related bladder cancer.

Bilharzial-related bladder carcinoma (BBC) is the most common malignant neoplasm in Egypt, also occurring with a high incidence in other regions of the Middle East and East Africa. The clinical and pathological features of BBC are different than those described for the conventional transitional cell carcinoma of the bladder, including the high incidence of squamous cell carcinoma reported in BBC and the fact that over 90% of BBC cases at presentation are advanced-stage tumors (P3 and P4). This study was conducted to better define the phenotypic alterations associated with BBC affecting the p53 cell cycle control pathway, including altered patterns of expression of downstream effector proteins such as mdm2 and p21/WAF1. A well-characterized cohort of 125 patients affected with bilharzial-related bladder tumors was studied. Tumors were classified as squamous carcinomas (n = 68), transitional cell carcinomas (n = 55), or adenocarcinomas (n = 2). The products encoded by TP53, mdm2, and p21/WAF1 genes were analyzed by immunohistochemistry. Furthermore, the patterns of expression of these molecules were correlated with the Ki67 proliferative index. In addition, the microanatomical distribution of programmed cell death was assessed in a subset of tumors, using the so-called terminal deoxynucleotidyl transferase-mediated nick end labeling method. p53 nuclear overexpression was identified in 25 (20%) of 125 cases. Nuclear overexpression of mdm2 was detected in 74 (59.2%) of 125 cases. There was a statistically significant association between coexpression of both p53 and mdm2 and detection of lymph node metastases (P = 0.04). p21/WAF1 expression was detected in 87 (72%) of 121 evaluable cases. A high Ki67 proliferative index was observed in 99 (86%) of 115 evaluable cases. There was a statistically significant association between high Ki67 proliferative index and mdm2-positive phenotype (P = 0.005) and deep muscle invasion (P3b; P = 0.026) as well as lymph node metastases (P = 0.039). Apoptosis was observed in terminally differentiated tumor cells identified in the superficial layers of well-differentiated squamous carcinoma or exfoliating cells in transitional lesions. However, only rare apoptotic tumor cells were found in basal or suprabasal layers as well as in the invasive elements of the neoplasms studied. These results suggest that the frequency of p53 nuclear overexpression in BBC is lower than that reported for conventional transitional cell carcinoma. Nevertheless, tumors with p53 alterations have a greater propensity to progress. The prominent number of cases displaying an mdm2-positive phenotype suggests that this may be an early incident in BBC and should be regarded as a potential oncogenic phenomenon. This is supported by the significant correlation between high Ki67 proliferative index and mdm2 overexpression. The association of an aggressive clinical course with the coexpression of both p53 and mdm2 products might be viewed as a cooperative effect that develops in tumor progression.

Adenocarcinoma↗
PubMed1996

Clinical trials in relapsed prostate cancer: defining the target.

A re-examination of the methods of developing new treatments for patients with prostate cancer whose disease has progressed during hormone therapy is necessitated by the following: 1) the impact of prostate-specific antigen (PSA) testing on patient selection, 2) the increasing number of studies using noncytotoxic approaches, and 3) the lack of validated methods to report outcomes. PSA monitoring after primary therapy has increased the number of patients referred for therapy with a rising value in this marker or an asymptomatic change in a radionuclide bone scan as the only manifestation(s) of relapse. The development of drugs for this population of patients presents a unique challenge because the classical criterion used to assess efficacy in the phase II setting, i.e., the presence of objective changes in measurable disease sites, frequently does not apply. Since no approach has been proven to prolong survival, the highest priority must be placed on developing new therapies. Standardizing the methods for evaluating treatments is also essential so that promising strategies are pursued and inactive therapies are not developed further.

Biomarkers, Tumor↗
PubMed1996

Genistein is a natural inhibitor of hexose and dehydroascorbic acid transport through the glucose transporter, GLUT1.

Genistein is a dietary-derived plant product that inhibits the activity of protein-tyrosine kinases. We show here that it is a potent inhibitor of the mammalian facilitative hexose transporter GLUT1. In human HL-60 cells, which express GLUT1, genistein inhibited the transport of dehydroascorbic acid, deoxyglucose, and methylglucose in a dose-dependent manner. Transport was not affected by daidzein, an inactive genistein analog that does not inhibit protein-tyrosine kinase activity, or by the general protein kinase inhibitor staurosporine. Genistein inhibited the uptake of deoxyglucose and dehydroascorbic acid in Chinese hamster ovary (CHO) cells overexpressing GLUT1 in a similar dose-dependent manner. Genistein also inhibited the uptake of deoxyglucose in human erythrocytes indicating that its effect on glucose transporter function is cell-independent. The inhibitory action of genistein on transport was instantaneous, with no additional effect observed in cells preincubated with it for various periods of time. Genistein did not alter the uptake of leucine by HL-60 cells, indicating that its inhibitory effect was specific for the glucose transporters. The inhibitory effect of genistein was of the competitive type, with a Ki of approximately 12 microM for inhibition of the transport of both methylglucose and deoxyglucose. Binding studies showed that genistein inhibited glucose-displaceable binding of cytochalasin B to GLUT1 in erythrocyte ghosts in a competitive manner, with a Ki of 7 microM. These data indicate that genistein inhibits the transport of dehydroascorbic acid and hexoses by directly interacting with the hexose transporter GLUT1 and interfering with its transport activity, rather than as a consequence of its known ability to inhibit protein-tyrosine kinases. These observations indicate that some of the many effects of genistein on cellular physiology may be related to its ability to disrupt the normal cellular flux of substrates through GLUT1, a hexose transporter universally expressed in cells, and is responsible for the basal uptake of glucose.

Amino Acids↗