Poorer graft survival in ethnic minorities: results from a multi-centre UK study of kidney transplant outcomes.

BACKGROUND: The STEPP group was established to investigate factors that affect long-term transplant outcomes including quality of life and other patient-reported outcomes between different transplant centers and patients. METHODS: Data were collected for 2,650 patients whose first renal transplant took place between 1992 and 2003 in five UK centers. Univariable and multivariable survival analyses were performed using eleven candidate explanatory variables. RESULTS: Graft survival was worse in Black (B) patients (HR B v W 1.57 95% CI 1.10, 2.24), and in South Asian (A) patients (HR A v W 1.39 95% CI 1.03, 1.85) compared to Whites (W) after adjusting for other factors including HLA mismatch, and time on dialysis. Time spent on dialysis pre-transplantation was non-linearly associated with patient, but not death-censored graft survival. Losing a functioning graft was a strong predictor of patient death. One site had both the best graft and the worst patient survival. CONCLUSIONS: Differences in patient and graft survival between ethnic groups cannot be explained by currently recognized factors. These, and the complex balance between optimum patient and graft survival which differs between sites in this study require further investigation.

Epidermal growth factor regulates the in vitro sensitivity of human ovarian carcinoma cells to cisplatin.

Cisplatin (DDP) is the most effective drug for the treatment of human ovarian cancer, but the mechanisms that determine sensitivity to the cytotoxic action of DDP are not well understood. Treatment of two human ovarian carcinoma cell lines with epidermal growth factor (EGF) simultaneously increased sensitivity to DDP and caused a persistent change in morphology in the absence of any mitogenic effect. Sensitization to DDP was shown to be dependent on both EGF concentration and EGF receptor number in C127 mouse fibroblasts expressing the human EGF receptor after transfection with a pBPV plasmid construct containing the human EGF receptor gene under control of the transferrin receptor 3'-inducible regulator. Sensitization of human ovarian carcinoma cells to DDP was not blocked by inhibition of protein synthesis. EGF did not enhance sensitivity to DDP or alter morphology in DDP-resistant human ovarian carcinoma cells despite the presence of functional EGF receptors on these cells. These results showed that elements of the signal transduction pathway activated by EGF determined cellular sensitivity to DDP, and that a DDP-resistant phenotype is associated with a defect in this signal transduction pathway.

Evaluation of Therapeutics for Advanced-Stage Heart Failure and Other Severely-Debilitating or Life-Threatening Diseases.

Severely-debilitating or life-threatening (SDLT) diseases include conditions in which life expectancy is short or quality of life is greatly diminished despite available therapies. As such, the medical context for SDLT diseases is comparable to advanced cancer and the benefit vs. risk assessment and development of SDLT disease therapeutics should be similar to that of advanced cancer therapeutics. A streamlined development approach would allow patients with SDLT conditions earlier access to therapeutics and increase the speed of progression through development. In addition, this will likely increase the SDLT disease therapeutic pipeline, directly benefiting patients and reducing the economic and societal burden of SDLT conditions. Using advanced-stage heart failure (HF) as an example that illustrates the concepts applicable to other SDLT indications, this article proposes a streamlined development paradigm for SDLT disease therapeutics and recommends development of aligned global regulatory guidance.

Renal transplantation in a patient with loin pain hematuria syndrome.

We describe a patient with loin pain hematuria syndrome who required bilateral nephrectomy because of intractable pain and urological complications. After bilateral nephrectomy, his pain disappeared for the first time in 40 years. He subsequently received a cadaveric renal transplant which, at 4-year follow-up, is working well. Although he has developed intermittent microscopic hematuria, there has been no significant recurrence of pain over the kidney. This is the first reported case of transplantation after bilateral nephrectomy for loin pain hematuria syndrome. It provides insight tnto the possible pathogenic mechanisms underlying the condition.

Abrogation of cisplatin-induced programmed cell death in human breast cancer cells by epidermal growth factor antisense RNA.

BACKGROUND: Epidermal growth factor receptor (EGF-R) perturbation by receptor ligand(s), e.g., epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha), or receptor-specific antibodies accentuates cisplatin-induced toxicity in tumor cells. This sensitization occurs only in tumor cells with high expression of EGF-R but not in those with low expression of EGF-R. PURPOSE: Therefore, we have studied the role of EGF-R expression on cisplatin-mediated cytotoxicity. METHODS: MDA-468 human breast cancer cells were stably transfected with a p-chloramphenicol acetyl transferase (pact[p]-CAT) vector containing a 4.1-kilobase full-length antisense EGF-R complementary DNA. EGF-R content was assessed by 125I-EGF binding and EGF-R immunoblot assays. Cisplatin sensitivity was evaluated by (a) colony-forming assay in vitro, (b) xenograft growth in nude mice, (c) cell cycle distribution of propidium iodide-labeled DNA, (d) DNA fragmentation in agarose gels, and (e) terminal deoxynucleotidyl transferase (Tdt) fluorescence in situ. Cisplatin uptake was measured by atomic absorption spectroscopy, and the levels of drug-DNA intrastrand adducts were determined by a dissociation-enhanced fluoroimmunoassay that utilizes an antibody against cisplatin-modified DNA. RESULTS: Selected clones (MDA-468/AS-EGFR) exhibited more than 90% loss of both 125I-EGF binding and receptor content determined by western blot analysis, whereas clones transfected with the vector alone (MDA-468/p-CAT) had EGF-R levels similar to those of the parent cells. By use of a colony-forming assay, the 1-hour IC50 (i.e., the concentration of drug required for 1 hour to achieve 50% cell kill) for cisplatin was 2 microM or less for parental and vector-transfected clones (n = 4), whereas it was 25 microM or more for all MDA-468/AS-EGFR clones (n = 3). MDA-468/p-CAT clones exhibited internucleosomal DNA fragmentation, enhanced Tdt-end labeling in situ, and G2 arrest 48 hours after a 1-hour incubation with 3-30 microM cisplatin. Under these conditions, apoptosis and G2 arrest were undetectable in all MDA-468/AS-EGFR clones. An MDA-468 subline selected after long-term treatment with a TGF-alpha-Pseudomonas exotoxin A fusion protein 40 lacked EGF binding and also exhibited cisplatin resistance (1-hour IC50: > 30 microM) compared with parental cells. This EGF-R-dependent difference in cisplatin response was confirmed in a nude mouse xenograft model by use of high- and low-EGF-R-expressing cell clones. Total intracellular drug accumulation after a 1-hour cisplatin exposure, as measured by atomic absorption spectroscopy, was identical in both groups of cells. Intrastrand drug-DNA adducts, however, were statistically higher in high EGF-R expressors than in low-EGF-R-expressing clones. CONCLUSIONS: These data indicate that a critical level of EGF-R signaling, which is amplified in some common human cancers, is necessary for cisplatin-mediated apoptosis in tumor cells and suggest an inhibitory effect of this pathway on the repair of cisplatin-damaged DNA.

Mitochondrial defects in cis-diamminedichloroplatinum(II)-resistant human ovarian carcinoma cells.

We have been studying the membranes of cisplatin (DDP)-resistant 2008 human ovarian carcinoma cells (C13* cells) for alterations that may account for their decreased DDP accumulation. We now report that C13* cells have significant changes in their mitochondrial and plasma membrane potentials and in their mitochondrial morphology. C13* cells accumulated 2.0 +/- 0.1-fold more of the membrane potential marker [3H]tetraphenylphosphonium cation (TPP+) than sensitive cells. In high K+ medium, which depolarizes the plasma membrane but not the mitochondrial membrane, [3H]TPP+ accumulation was still 2.3 +/- 0.1- fold greater in resistant cells, indicating that the mitochondrial membrane potential was higher. In the presence of carbonyl cyanide p-trifluoromethoxyphenyl hydrazone, which depolarizes the mitochondrial membrane but not the plasma membrane, [3H]TPP+ accumulation demonstrated that the plasma membrane potential in C13* cells was elevated as well. These elevations were also present in C8 cells with low-level DDP resistance. After ouabain treatment, exposure to nigericin stimulated [3H]TPP+ accumulation 3-fold in sensitive cells but had no effect in C13* cells, indicating either that: (a) the mitochondrial pH gradient was minimal; or (b) the mitochondrial electric potential was already at a maximal level in C13* cells. Fluorescence microscopy of living cells stained with the mitochondria-specific dye rhodamine 123 revealed that resistant cells had significant changes in their mitochondrial morphology. Electron microscopy also revealed major alterations in the cristae structure. The C13* cells, which were approximately 15-fold resistant to DDP, were 5-fold hypersensitive to the mitochondrial poison rhodamine 123. We conclude that these DDP-resistant 2008 cells have an elevated plasma membrane potential and alterations in their mitochondria as indicated by their membrane potential, morphology, and sensitivity to mitochondrial poisons. These results imply that mitochondria play an important role in the cellular pharmacology of DDP.

Loss of cis-diamminedichloroplatinum(II) resistance in human ovarian carcinoma cells selected for rhodamine 123 resistance.

Cisplatin (DDP)-resistant 2008 human ovarian carcinoma cells (C13*) have an elevated mitochondrial membrane potential that confers hypersensitivity to lipophilic cations. We have addressed whether this change was directly linked to the DDP-resistant phenotype or was a random alteration, unrelated to resistance. The elevated mitochondrial membrane potential and ensuing rhodamine 123 (Rh123) hypersensitivity of C13* cells provided a positive selection rationale. Cells with low mitochondrial membrane potential will have a survival advantage over those with a high mitochondrial membrane potential, when exposed to Rh123. We therefore used Rh123 to isolate revertants (RH4) from the 12-fold DDP-resistant C13* cell line that had a low mitochondrial membrane potential. RH4 cells had parental (2008) mitochondrial membrane potential levels as shown by flow cytometry analysis of Rh123 stained cells and by tetraphenylphosphonium cation uptake. The RH4 cells lost a substantial portion of their DDP resistance such that they were only 2- to 3-fold resistant to DDP. Despite this major loss of resistance, they retained a number of the phenotypic changes related to DDP resistance, observed in C13* cells. RH4 cells displayed the same DDP accumulation defect, 2-fold elevated glutathione levels and 2-fold resistance to CdCl2 as C13* cells. We conclude that although the biochemical mechanism by which an elevated mitochondrial membrane potential elicits DDP resistance is unknown, these mitochondrial changes are central to the expression of DDP resistance in C13* cells.

Differential potentiation of alkylating and platinating agent cytotoxicity in human ovarian carcinoma cells by glutathione depletion.

We have determined the effect of glutathione (GSH) depletion on the cytotoxicity of three nitrogen mustards, six platinum complexes, and mitomycin C in a human ovarian carcinoma cell line. GSH levels in COLO 316 cells were depleted by exposure of cell monolayers to 0.5 mM D,L-buthionine-S,R-sulfoximine. GSH depletion significantly potentiated the cytotoxicity of L-phenylalanine mustard, chlorambucil, and mechlorethamine as determined by clonogenic assay on plastic plates. The dose modification factors were 2.6, 2.6, and 1.9, respectively. The same level of GSH depletion had a minimal effect on the cytotoxicity of cis-diamminedichloroplatinum(II) (cis-DDP), carboplatin, dichloro(ethylenediamine)platinum(II), 1,2-diaminocyclohexylplatinum(II) malonate, and iproplatin. The dose modification factors of GSH depletion for these drugs were 1.4 or less. trans-Diamminedichloroplatinum(II) was, however, markedly potentiated by GSH depletion with a dose modification factor of 2.7. Mitomycin C was minimally potentiated by GSH depletion. We have also generated cis-DDP-resistant cells from COLO 316 and 2008 human ovarian carcinoma cells by in vitro selection with cis-DDP. These cis-DDP-resistant cells had identical levels of GSH as the parental cells. GSH depletion sensitized these cells only to the same degree as the parental cells and did not reverse the resistant phenotype. Our results indicate that intracellular GSH levels are not an important determinant of the cytotoxicity of cis-platinum(II) or cis-platinum(IV) complexes in COLO 316 and 2008 cells. In addition, altered GSH metabolism does not appear to be a component of the cis-DDP-resistant phenotype in these cells.

cis-Diamminedichloroplatinum(II) accumulation in sensitive and resistant human ovarian carcinoma cells.

We have characterized the accumulation of cisplatin (DDP) into parent and cisplatin-resistant 2008 human ovarian carcinoma cells. Accumulation of DDP at 1 h was a linear function of concentration from 0.25 to 100 microM DDP in both cell types. DDP-resistant cells that were only 3.3-fold resistant had approximately 50% less accumulated platinum at all concentrations examined. Accumulation of 1.0 microM DDP was linear for approximately 3 h and then slowed but did not reach equilibrium at up to 24 h in either cell type. The decreased DDP accumulation in resistant cells did not appear to be due to increased efflux; similar percentages of platinum were available for exodus in parent and resistant cells. Intracellular metabolites of DDP appeared to be decreased by similar amounts in the resistant cells. Native DDP was not driven uphill into cells against a concentration gradient, suggesting that DDP uptake does not involve primary active transport. The metabolic inhibitors, dinitrophenol and NaF, did not decrease DDP accumulation; iodoacetate had a stimulatory effect. Dinitrophenol, however, in combination with NaF or iodoacetate decreased DDP accumulation. A 30-min exposure to 0.2 mM ouabain also decreased DDP accumulation in both parent and resistant cells. A component of DDP accumulation thus appears to be energy dependent. These studies have identified decreased DDP accumulation as an important mechanism of resistance that is expressed early in the acquisition of DDP resistance in human ovarian carcinoma cells.

Role of the Na+, K(+)-adenosine triphosphatase in the accumulation of cis-diamminedichloroplatinum(II) in human ovarian carcinoma cells.

We examined the importance of the Na+, K(+)-ATPase in cisplatin (DDP) accumulation in 2008 human ovarian carcinoma cells and describe changes in the Na+, K(+)-ATPase in DDP-resistant cells with DDP accumulation defects. Approximately 50% of DDP accumulation was inhibitable by ouabain. DDP accumulation into 2008 cells could be maximally inhibited when cells were preincubated with ouabain for 1 h prior to DDP exposure. The half-maximal inhibition was obtained with 0.13 microM ouabain. Similar inhibition of DDP accumulation was obtained when the Na+, K(+)-ATPase was blocked by ATP depletion or by incubating cells in K(+)-free medium. This same percentage of DDP accumulation was Na+ dependent and varied directly with Na+ concentration. These effects on DDP accumulation could be detected as early as 1 min after the imposition of 0-trans conditions, strongly suggesting that the inhibition was due to modulation of a drug influx step. The Na+, K(+)-ATPase in 2008/DDP cells had a similar KD for ouabain binding and 36% less Na+, K(+)-ATPase molecules/mg of protein than 2008 cells. 2008/DDP cells 2.3 +/- 0.2 (SE, n = 3) fold cross-resistant to ouabain in a continuous exposure clonogenic assay. Despite these changes in the Na+, K(+)-ATPase, the net basal Na+, K(+)-ATPase activity was the same in sensitive and DDP-resistant cells as determined by ouabain-inhibitable 86Rb+ influx. The basal Na+ levels were also similar in the sensitive and resistant cells. These data suggest that DDP accumulation is partially Na+ dependent and that, therefore, the Na+, K(+)-ATPase which maintains the Na+ gradient may play an important role in determining how much DDP enters cells. Whether there is a causal link between the changes in the Na+, K+-ATPase in DDP-resistant cells and their DDP accumulation defect is not yet known.

Phase I/pharmacokinetic study of intraperitoneal cisplatin and etoposide.

We administered cisplatin and etoposide by peritoneal dialysis to 39 patients with i.p. malignancies in order to investigate the toxicity, pharmacokinetics, and clinical activity of this 2-drug combination. All patients received i.v. sodium thiosulfate concurrently with the i.p. chemotherapy. Myelosuppression, nausea, vomiting, and malaise were the primary toxicities encountered. The maximum tolerated dose of etoposide was 350 mg/m2, when administered with a fixed dose of cisplatin, 200 mg/m2. Although the total (free and protein-bound) etoposide exposure for the peritoneal cavity was only 1.5-fold greater than that for the plasma, the free (non-protein bound) etoposide peritoneal exposure was 65-fold greater than the plasma. Tumor regressions were noted in patients with ovarian and pancreatic carcinomas. This study is the first demonstration of the large pharmacokinetic advantage that exists for the i.p. administration of highly protein-bound drugs, and it also documents the clinical activity of i.p. cisplatin and etoposide.

Growth inhibition by thymidine of leukemic HL-60 and normal human myeloid progenitor cells.

We compared the relative susceptibility of HL-60, a human acute progranulocytic leukemia cell line, and the normal human myeloid progenitor cell, the colony-forming unit in culture, to growth inhibition by thymidine. Normal human myeloid colony formation was more sensitive to thymidine than was HL-60 colony formation, the former being inhibited by greater than or equal to 0.5 mM thymidine and the latter by greater than or equal to 5.0 mM. Colony inhibition by thymidine was irreversible in both cases after a seven-day incubation of the colony-forming unit in culture in liquid medium enriched with thymidine and subsequent replating in thymidine-free soft agar. Thymidine-induced inhibition of HL-60 cloning could be partially prevented by deoxycytidine, whereas normal myeloid cloning could not, suggesting that high-concentration thymidine may affect processes necessary for cloning in addition to deoxyribonucleotide synthesis. HL-60 growth in liquid suspension culture could be suppressed transiently by 1.0 mM thymidine, suppressed totally by greater than or equal to 5.0 mM thymidine, and rescued completely by concomitant addition of deoxycytidine. The development of resistance to 1.0 mM thymidine could not be accounted for by reduction in thymidine pool size or by reduction in thymidine kinase activity. Replating of HL-60 cells growing in the presence of 1.0 mM thymidine in liquid medium in thymidine-free soft agar produced significant colony inhibition, also suggesting that thymidine affects more than just deoxyribonucleotide synthesis or that the clonogenic HL-60 cell presents a distinct subpopulation with more sensitive deoxyribonucleotide-synthetic control mechanisms.

Expression of the c-Ha-ras oncogene in mouse NIH 3T3 cells induces resistance to cisplatin.

The effect of expression of the c-Ha-ras oncogene on cisplatin (DDP) sensitivity was examined in murine NIH 3T3 cells transfected with the dexamethasone (DEX)-inducible mouse mammary tumor virus promoter linked to an activated c-Ha-ras gene [LTR H-ras(A) cells]. Treatment of these cells with 5 microM DEX for 24 h induced c-Ha-ras expression and produced an 8.2 +/- 1.3-fold (SD) increase in DDP resistance as quantitated by clonogenic assay. Induction of the c-Ha-ras oncogene reduced DDP accumulation by 40% and intrastrand adduct formation by 17%. In nontransfected wild-type NIH 3T3 cells, DEX did not induce DDP resistance nor did it decrease DDP accumulation. Induction of c-Ha-ras expression did not alter cellular glutathione content or the activity of glutathione-S-transferase in the LTR H-ras(A) cells. DEX increased cellular metallothionein content by 1.6-fold in NIH 3T3 cells and 3.3-fold in LTR H-ras(A) cells. We conclude that DEX-induced overexpression of a mutant c-Ha-ras gene confers DDP resistance and that this resistance is associated with an impairment of cellular drug accumulation and an increase in metallothionein content.

The effects of terbium on the accumulation of cisplatin in human ovarian cancer cells.

In this investigation, we report a relationship between the terbium (Tb3+) binding protein and the accumulation of cisplatin in human ovarian cancer cells. The number of Tb3+ binding sites in cisplatin-resistant C13+ cells is significantly greater by 79% than those in cisplatin-sensitive 2008 cells. Exposure to Tb3+ also increased the cellular accumulation of cisplatin. The accumulation of cisplatin as a function of the Tb3+ concentration in the C13+ cells (0.85%/microM Tb3+) was significantly greater than the accumulation of cisplatin in 2008 cells with respect to Tb3+ (0.46%/microM Tb3+). The number of Tb3+ binding sites in revertant RH4 cells was similar to that in 2008 cells. The RH4 cells were less sensitive to the stimulatory effects of Tb3+ than the C13+ cells. Our results show that the Tb3+ binding protein correlates with cisplatin resistance, and the receptor binding of Tb3+ increases the accumulation of cisplatin in cisplatin-resistant cells.

The pharmacology of intraperitoneally administered bleomycin.

The clinical pharmacology of intraperitoneally administered bleomycin was examined in 11 patients with malignancies confined predominantly to the peritoneal cavity. Bleomycin (60 mg/m2) was mixed in 2 L of 0.9% NaCl, and administered rapidly into the peritoneal cavity via a Port-a-Cath (Pharmacia Nu Tech, Inc, Walpole, MA). The cavity was drained following either a four- or eight-hour dwell time. Bleomycin concentration in the peritoneal cavity and plasma was determined by radioimmunoassay. A total of 15 courses was studied. The peak peritoneal: plasma concentration ratio averaged 22, and total exposure for the peritoneal cavity averaged seven-fold greater than that for the plasma. The peritoneal and plasma half-lives for bleomycin were 3.2 and 6.0 hours, respectively. The peritoneal clearance of bleomycin averaged 11.3 mL/min/m2. Abdominal pain occurred on 47% of courses; other toxicities included fever, skin rash, and mucositis. We conclude that there is a substantial pharmacologic advantage to the peritoneal route for tumors confined to the peritoneum, but that the advantage is less, and the local toxicity greater, than that found with the intraperitoneal administration of many other anticancer drugs.

Pharmacokinetics of 5-fluorouracil during hyperthermic pelvic isolation-perfusion.

The pharmacokinetics of 5-fluorouracil (5-FU) injected into a surgically isolated pelvic circuit during hyperthermic perfusion was studied in five patients with local recurrence of anorectal cancer. 5-FU doses ranged from 11 to 23 mg/kg. The geometric mean ratio of peak plasma 5-FU in the isolated to systemic circuits was 10, the ratio at the end of the 45-minute perfusion was 12.5. The mean half-life of 5-FU in the isolated circuit was 18.5 minutes. Total drug exposure for the isolated circuit was 7.8-fold greater than for the systemic compartment. These results demonstrate a large pharmacologic advantage for the use of the isolation-perfusion technique.

High-dose cisplatin with sodium thiosulfate protection.

Nephrotoxicity frequently limits the dose of cisplatin to less than 120 mg/m2 per injection. Sodium thiosulfate is a neutralizing agent for cisplatin that protects against renal damage. To determine whether injection of thiosulfate would permit larger doses of cisplatin to be administered, a fixed 9.9-g/m2 dose of thiosulfate was given intravenously over three hours concurrently with escalating doses of cisplatin. Cisplatin was administered over the last two hours of the thiosulfate infusion. Using this technique, it was possible to escalate the cisplatin dose to 225 mg/m2 before dose-limiting toxicities were encountered. Comparison of cisplatin pharmacokinetics in patients treated with 202.5 mg/m2 plus thiosulfate to those in patients treated with 100 mg/m2 without thiosulfate indicated that there were no changes in the elimination rate constant, volume of distribution, or total body clearance of cisplatin. The total drug exposure for the plasma was approximately twofold at the higher cisplatin dose. This study demonstrates that concurrent administration of thiosulfate permits at least a twofold increase in dose and total exposure to cisplatin.

Stimulation of cis-diamminedichloroplatinum(II) accumulation by modulation of passive permeability with genistein: an altered response in accumulation-defective resistant cells.

The effect of the tyrosine kinase inhibitor genistein on the accumulation of cisplatin (DDP) was investigated in DDP-sensitive and -resistant human 2008 ovarian carcinoma cell lines. DDP accumulation after a 1-h exposure was maximally increased by concurrent 40 micrometer genistein. The maximal stimulation of accumulation was observed after 2 h of total genistein exposure and was 83 +/- 13% (n = 5) higher than controls. With resistant C13(*) cells, however, the stimulation of accumulation was delayed until 4 h and was increased only 46 +/- 18% compared to controls. Revertant RH4 cells that retained the accumulation defect behaved like the C13(*) cells. Genistein stimulated [3H]mannitol accumulation (a marker of passive permeability) by 43 +/- 9% (n = 3) in 2008 cells, and the effect was maximal after 2 h of total genistein exposure. Changes in [3H]mannitol accumulation in 2008 parent cells were highly correlated with DDP accumulation (r = 0.9010). These experiments also revealed that [3H]mannitol accumulation after 2 h in C13(*) cells was reduced 38% compared to 2008 cells, a decrease that reflected the DDP accumulation defect. Fluid-phase pinocytosis determined with lucifer yellow CH as a marker showed no difference between 2008 and C13(*) cells and no effect of genistein. Genistein was demonstrated to clearly inhibit protein-tyrosine phosphorylation initiated by the epidermal growth factor receptor kinase. Differences were noted in the phosphotyrosine pattern between the 2008 and C13(*) cells. Under the conditions that had the maximal effect on DDP accumulation in 2008 cells, genistein decreased the IC50 of DDP 8.2-fold in 2008 cells and 4.7-fold in C13(*) cells. We conclude that: (a) genistein stimulates DDP accumulation by modulating the passive permeability of the plasma membrane; (b) C13(*) cells are less permeable to passively diffusing small molecules, which offers a mechanism for the DDP accumulation defect without invoking carrier proteins; (c) the effect of tyrosine kinase inhibition on passive permeability is altered in C13(*) cells; and (d) pinocytosis contributes insignificantly to DDP accumulation. Genistein, a dietary isoflavone, thus seems to be a promising clinical candidate for combination with DDP.

Immunohistochemical staining for glutathione S-transferase predicts response to platinum-based chemotherapy in head and neck cancer.

The glutathione S-transferases (GSTs) play an important role in the cell's defense against toxic substances. The GSTs are a family of enzymes produced by several genes that interact with distinct but overlapping substrates and that may play a role in resistance of tumor cells to several chemotherapeutic agents. We examined the correlation between expression of GSTs determined by immunohistochemistry and clinical response to platinum-based chemotherapy in 51 patients with head and neck cancer, who received a total of 56 courses of chemotherapy. The overall response rate for the 56 chemotherapy treatment courses was 48%. The overall response rate (complete response + partial response) for patients with low GST scores was 88% (21 of 24), whereas among the patients with high GST scores, the overall response rate was 19% (6 of 32; P = 0.001). Patients with a low GST score were 4.7 times more likely to respond to chemotherapy than patients with high GST scores. GST scores corresponded to response in 84% of cases. Among 23 patients treated with neoadjuvant chemotherapy, the overall response rate for patients with low GST scores was 100% (14 of 14), whereas among the patients with high GST scores, the overall response rate was 44% (4 of 9; P = 0.002). Among 33 patients treated with chemotherapy for relapsed disease, the overall response rate for patients with low GST scores was 70% (7 of 10), whereas among the patients with high GST scores, the overall response rate was 8.6% (2 of 23; P < 0.001). We conclude that GST expression correlates well with response to platinum-based chemotherapy in head and neck cancer.