Search PubMed⌕ Search

Biomedical subjects

N Saijo

Publications and source records attributed to N Saijo.

At least 181 records · Page 10Linked to original sources
PubMed1995

Construction of a novel bovine papillomavirus vector without detectable transforming activity suitable for gene transfer.

Bovine papillomavirus type 1 (BPV-1)-derived vectors may be useful for gene therapy because of their episomal maintenance at intermediate to high copy number and stable, high-level expression of gene products. To increase the safety of BPV-1 for human trials, the transforming early genes E5, E6, and E7 were deleted and a new vector, B45-Neo, was established and its transforming potential, episomal maintenance, and cDNA expression determined. Deletion of E5, E6, and E7, caused a decrease of the copy number to 80 in 3T3 fibroblasts when B45-Neo was compared to the parent vector that supported more than 1,000 copies per cell. No significant difference in the copy number, which ranged between 13 and 30 per cell, was detected in other cell lines of murine or human origin. The episomal maintenance of B45 and its ability to express cDNA was retained. B45-Neo, in contrast to BMG-Neo, however, was unable to transform NIH-3T3 and C1271 cells in soft agar colony assays. Unlike BMG-Neo, B45-Neo did not cause morphological changes in 3T3 and C1271 cells characteristic for transformation. It is concluded that B45-Neo is an efficient expression vector without detectable transforming activity and may be useful and safe for human gene therapy trials.

3T3 Cells↗
PubMed1995

Inhibition of vitamin D3-induced cell differentiation by interferon-gamma in HL-60 cells determined by a nitroblue tetrazolium reduction test.

The combined effects of 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] and interferon-gamma (IFN-gamma) or tumor necrosis factor alpha (TNF-alpha) on cell differentiation in HL-60 human promyelocytic leukemia cells were examined by a nitroblue tetrazolium (NBT) reduction test. 1,25(OH)2D3 at the concentrations of 7-70 nM induced NBT-positive cells, which was used as a criterion of cell differentiation. IFN-gamma itself showed little effect on induction of NBT-positive cells or on cell growth at a concentration up to 1000 U/ml. However, in a combination of 1,25(OH)2D3 with IFN-gamma (100 and 300 U/ml), cell differentiation was strongly inhibited and was accompanied by growth inhibition. Treatment with a combination of 1,25(OH)2D3 and TNF-alpha or IFN-gamma and TNF-alpha showed an additive effect on cell differentiation. IFN-gamma seems to act as a specific inhibitor for 1,25(OH)2D3-induced cell differentiation. To elucidate the cause of the inhibition of cell differentiation by IFN-gamma, the ability of the cells to produce superoxide (O2-) was examined after culture for 5 days in the presence of 1,25(OH)2D3 and IFN-gamma. The results indicated that the inhibition of IFN-gamma was caused by a reduction in the ability of the cells to produce O2- in response to stimulation by 12-O-tetradecanoylphorbol-13-acetate (TPA).

Calcitriol↗
PubMed1995

A pharmacokinetic and pharmacodynamic analysis of CPT-11 and its active metabolite SN-38.

In the present study, an attempt was made to determine the precise pharmacokinetics of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) and its active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38). The relationship between pharmacokinetic parameters and pharmacodynamic effects was also investigated to elucidate the cause of interpatient variation in side effects. Thirty-six patients entered the study. CPT-11, 100 mg/m2, was administered by IV infusion over 90 min weekly for four consecutive weeks. The major dose-limiting toxicities were leukopenia and diarrhea. There was a positive correlation between the area under the concentration-time curve (AUC) of CPT-11 and percent decrease of WBC (r = 0.559). On the other hand, episodes of diarrhea had a better correlation with the AUC of SN-38 (r = 0.606) than that of CPT-11 (r = 0.408). Multivariate analysis revealed that the AUC of SN-38, AUC of CPT-11 and indocyanine green retention test were significant variables for the incidence of diarrhea and that both performance status and AUC of CPT-11 were significant variables for percent decrease of WBC. The large interpatient variability of the degree of leukopenia and diarrhea is due to a great plasma pharmacokinetic variation in CPT-11 or SN-38. The AUCs of CPT-11 and SN-38 obtained from the first administration of CPT-11 correlate with toxicities, but it is impossible to predict severe side effects before the administration of CPT-11 at the present time.

Adult↗
PubMed1995

A limited sampling model for estimating pharmacokinetics of CPT-11 and its metabolite SN-38.

The objective of this study was to develop a limited sampling model (LSM) to estimate the area under the curve (AUC) of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) and that of 7-ethyl-10-hydroxycamptothecin (SN-38) as predictive pharmacokinetic variables for leukopenia and episodes of diarrhea induced by CPT-11 administration. The model was developed with a training set consisting of pharmacokinetic studies in 36 patients who received a 90-min i.v. infusion of CPT-11 at a dose of 100 mg/m2. A multiple regression analysis of CPT-11 or SN-38 concentrations observed at each time point in the training set was used to predict the AUC of CPT-11 or SN-38. The final sampling models using only two time points were: AUCCPT-11 = 3.7891*C2.5 + 14.0479*C13.5 + 1.5463 AUCSN-38 = 0.5319*C2.5 + 19.1468*C13.5 + 72.7349 where C2.5 and C13.5 are the plasma concentration of CPT-11 (micrograms/ml) or SN-38 (ng/ml) at 2.5 and 13.5 h after the initiation of CPT-11 infusion, respectively. The models were validated prospectively on a separate test data set of 12 patients receiving the same dose of CPT-11 investigated in a previous study. Validation of the final LSM on the test data set gave values of root mean square error (RMSE) of 12.72% and 5.97% for the AUC of CPT-11 and that of SN-38, respectively. The model can be used to monitor the AUCs of both CPT-11 and SN-38 for the early prediction of toxicities and to establish a pharmacokinetically based dose modification strategy for safe administration of CPT-11.

Adult↗
PubMed1995

Intracellular carboxyl esterase activity is a determinant of cellular sensitivity to the antineoplastic agent KW-2189 in cell lines resistant to cisplatin and CPT-11.

KW-2189, a novel antitumor antibiotic belonging to the duocarmycins, possesses marked DNA-binding activity upon activation by carboxyl esterase to its active form, DU-86. Three duocarmycins, KW-2189, DU-86 and duocarmycin SA, were active against the cisplatin (CDDP)-resistant human non-small cell lung cancer cell lines PC-9/CDDP and PC-14/CDDP, and the multidrug-resistant human small cell lung cancer cell line H69/VP. However, HAC2/0.1, a CDDP-resistant human ovarian cancer cell line which is also resistant to CPT-11 because of decreased intracellular activation of CPT-11, was about 12.8-fold more resistant to KW-2189. HAC2/0.1 was not resistant to other duocarmycins as compared to its parental cell line, HAC2. There was no difference between HAC2 and HAC2/0.1 with regard to the intracellular accumulation of KW-2189. Addition of 130 mU/ml of carboxyl esterase to the culture medium did not influence the sensitivity of HAC2 cells to KW-2189. However, the sensitivity of HAC2/0.1 cells to KW-2189 was enhanced to the level of HAC2. These results suggest that HAC2/0.1 is less potent than HAC2 in activating KW-2189. The carboxyl esterase activity of whole-cell and microsomal extracts from HAC2/0.1 was approximately 60% of that from HAC2. The cell-free experiment revealed that KW-2189 bound to DNA more efficiently in the presence of HAC2 than HAC2/0.1 cell extract. It was concluded that decreased intracellular carboxyl esterase activity in HAC2/0.1 cells caused decreased intracellular conversion of KW-2189 to its active form, thus producing resistance to KW-2189. The decreased conversion of CPT-11 to SN-38 in HAC2/0.1 cells might be explained by decreased carboxyl esterase activity.

Antibiotics, Antineoplastic↗
PubMed1995

Correlation of gene-specific damage with cisplatin between human adenocarcinoma cells and peripheral blood mononuclear cells analyzed by polymerase chain reaction-stop assay.

We investigated gene-specific damage in adenocarcinoma cells, obtained from pleural effusions of 9 primary lung cancer patients, induced by incubation with cisplatin for 3 h in vitro. The 2.7 kb fragment of the hypoxanthine phosphoribosyltransferase (HPRT) gene was amplified by the polymerase chain reaction (PCR) to quantify the DNA damage. A 7-fold difference in the extent of gene-specific damage among the patients was observed. Mononuclear cells (MNC) were obtained from freshly isolated blood from the same patients before they received chemotherapy. These cells were also incubated with cisplatin in vitro, and PCR amplification of the HPRT gene was carried out. A 4-fold variation of DNA damage among the patients was observed. Moreover, there was a linear correlation between the extents of the DNA damage in the tumor cells and MNCs (R2 = 0.676, P = 0.0016). These results suggest that the PCR-stop assay could be used to detect interindividual variations in the extent of gene-specific damage in both tumor cells and MNC from the same patients induced by cisplatin treatment. In conclusion, MNC could be used to analyze cisplatin-induced gene-specific damage in cancer patients whose tumor cells are inaccessible.

Adenocarcinoma↗
PubMed1995

Prospective evaluation of the feasibility of cisplatin-based chemotherapy for elderly lung cancer patients with normal organ functions.

A study was conducted to examine the feasibility of cisplatin-based chemotherapy in elderly patients (> or = 75 years old) with advanced non-small cell lung cancer (NSCLC) or small cell lung cancer (SCLC). Thirty-four patients were enrolled between September 1993 and December 1994. Patients with normal organ function and good performance status (PS) received cisplatin-based chemotherapy (cisplatin 80 mg/m2 on day 1 and vindesine 3 mg/m2 on days 2 and 8 for NSCLC, or cisplatin 80 mg/m2 on day 1 and etoposide 100 mg/m2 on days 2 to 4 for SCLC). Ten patients (29%) were eligible for this study, 7 with NSCLC and 3 with SCLC. Reasons for exclusion were ischemic heart disease in 14, poor PS (> or = 2) in 11, reduced creatinine clearance (Cer) in 10, abnormal electrocardiogram without ischemia in 9 and noncompliance with the protocol in 2 patients. Eight patients had two or more reasons. Nine of the 10 eligible patients were able to tolerate two or more courses of chemotherapy. All 3 patients with SCLC responded (1 complete response and 2 partial response), but only 1 of the patients with NSCLC achieved partial response. Toxicity was evaluated according to Japan Clinical Oncology Group criteria. All but one patient experienced grade 4 neutropenia, and 6 patients had infectious episodes requiring antibiotics. Grade 3 anemia and thrombocytopenia were observed in 1 and 2 patients, respectively. Non-hematological toxicities were mild. Only 10 of 34 patients (29%) satisfied our eligibility criteria and they experienced severe myelotoxicity. We conclude that chemotherapy should be given carefully to elderly patients even if they appear to have normal organ function.

Aged↗
PubMed1995

Phase I study of paclitaxel by three-hour infusion: hypotension just after infusion is one of the major dose-limiting toxicities.

The primary objectives of this study were to determine the maximum tolerated dose (MTD) of paclitaxel administered by 3-h infusion to patients with solid tumors, and to characterize the pharmacokinetics of a 3-h infusion in comparison with those of a 24-h infusion. Twenty-seven patients each received one of six levels of paclitaxel, 105, 135, 180, 210, 240 and 270 mg/m2, with premedication. Two patients given 240 mg/m2 and one patient given 270 mg/m2 unexpectedly had grade 3/4 hypotension just after finishing the paclitaxel infusion. Peripheral neuropathy was also dose-limiting at 270 mg/m2. Although granulocytopenia was significantly less severe than with a 24-h infusion, more than half of the patients experienced grade 4 toxicity at doses of 240 or 270 mg/m2. Severe hypersensitivity reactions (HSRs) were not observed. Pharmacokinetic studies using high performance liquid chromatography demonstrated proportionally greater increases in the peak plasma concentration and area under the curve, and decreases in clearance and volume of distribution with increasing dose, suggesting non-linear pharmacokinetics of paclitaxel when given by 3-h infusion. The MTD of paclitaxel given as a 3-h infusion was determined to be 240 mg/m2 with dose-limiting toxicities of granulocytopenia, peripheral neuropathy and hypotension. Hypotension just after infusion, induced by 3-h infusion of paclitaxel, is a new observation which has not been reported previously. The recommended dose for phase II study is 210 mg/m2. Although hypotension was observed as an unexpected toxic effect, paclitaxel could be administered safely over 3 h with premedication and proper monitoring, resulting in reduced myelotoxicity and with no increase in the incidence of HSRs as compared with a 24-h infusion.

Adult↗
PubMed1995

Intensive chemotherapy with cisplatin, doxorubicin, cyclophosphamide, etoposide and granulocyte colony-stimulating factor for advanced thymoma or thymic cancer: preliminary results.

A study was conducted to evaluate the impact of cisplatin, doxorubicin, cyclophosphamide and etoposide (PACE) with granulocyte colony-stimulating factor (G-CSF) on advanced thymoma or thymic cancer. Between August 1989 and December 1994, 14 patients with invasive, metastatic or recurrent thymoma or thymic cancer were treated with cisplatin (80 mg/m2, on day 1), doxorubicin (45 mg/m2, on day 1), cyclophosphamide (800 mg/m2, on day 1) and etoposide (80 mg/m2, on day 1-3) with G-CSF (90 micrograms/m2, on day 5-18) at the National Cancer Center Hospital, Tokyo. Courses were repeated every 3 or 4 weeks for a maximum of 4 cycles. Twelve patients were treated with 2 or more courses of PACE. Two patients were treated with only one course, one refused and another required emergency thoracic radiotherapy after one course of PACE. Six patients had partial responses (3 thymomas and 3 thymic cancers) but there were no complete remissions (response rates, 42.9%; 95% confidence interval, 17.7% to 71.1%). Moderate hematological toxicities were observed: grade 3 or 4 leukopenia, neutropenia, anemia and thrombocytopenia in 10, 13, 8 and 6 patients, respectively. Six patients developed infections that required antibiotics. Surgical resection or thoracic radiotherapy after PACE treatment was performed in 2 and 7 patients, respectively. The overall median survival time was 14.7 months (range, 5.9 to 59.7 months). For 9 patients who had received no prior treatment before chemotherapy, the median survival time was 8.9 months, and one patient survived for 4 years and is still alive. In conclusion, PACE with G-CSF frequently produces objective remissions in patients with advanced thymoma or thymic cancer. A large-scale intergroup study is necessary to determine the impact of this regimen on advanced thymoma and thymic cancer.

Adult↗
PubMed1995

[Cell cycle regulation by anticancer agent].

Some anticancer agents induce cell cycle arrest. We analyzed the effect of anticancer agents on cell-cycle regulators, such as CDK. Our data suggested that arresting cells in the G2-phase of the cell cycle by cisplatin might be regulated by dephosphorylation of cdc2 kinase. Butyrolactone I inhibits both cdc2 and CDK2 kinase in the cell-free system. The cytotoxic effect of paclitaxel shows mainly in the M-phase of the cell cycle. Suramin inhibits cdc2 kinase. UCN-01, a protein kinase-C inhibitor, also inhibits both cdc2 and CDK2 kinase. Some anticancer agents induce apoptosis.

Antineoplastic Agents↗
PubMed1995

[Strategies for the overcoming of drug resistance].

The purpose of the studies for drug resistance could be summarized in the following four points. 1) Mechanisms of acquired drug resistance can be translated to those of inherent resistance. 2) Molecular targets of anticancer drugs can be clarified and accurate application of methods for the overcoming of drug resistance may be possible. 3) Important hints can be obtained for the development of new anticancer agents against molecular targets. 4) Efficient methods can be provided to find new anticancer agents against drug refractory tumors. The clinical strategies for the overcoming of drug resistance are 1) the use of non cross-resistant drugs, 2) the application of the drugs for overcoming resistance, 3) high dose chemotherapy, and 4) the combined use of radiotherapy and surgery.

Antineoplastic Agents↗
PubMed1995

[Can improvement in therapy decrease the rate of death due to lung cancer?].

The incidence of lung cancer is increasing, and therapy for patients with this disease is not satisfactory. Surgery is done for patients with clinical (c)-stage I, II, and resectable stage IIIA non-small cell lung cancer (NSCLC). Chemotherapy, alone or in combination with radiotherapy, is given to patients with unresectable stage IV and stage III NSCLC, respectively. Chemotherapy is an important therapeutic modality for patients with small cell lung cancer (SCLC). CDDP + VP-16 (PVP) and CPA + ADM + VCR (CAV) alternating PVP regimens are standard treatment for patients with SCLC. Chemotherapy and radiotherapy are given to patients with limited disease. To develop more effective treatments, we are investigating (1) the schedule and timing of radiotherapy, (2) combination chemotherapy including new drugs, (3) dose-intensive chemotherapy, and (4) new strategies such as gene therapy. Radiotherapy is commonly used sequentially and the standard fractionation is 2 Gy/fr/day. We are studying other timings, such as concurrent and alternating, and other schedules, such as hyperfractionation and accelerated hyperfractionation. Promising new drugs include paciltaxel, docetaxel, vinorelbine, and CPT-11. These are now used in combination with platinum. To evaluate dose-intensive chemotherapy for SCLC, we are conducting a phase III study comparing CODG + G-CSF with CAV/PVP.

Carcinoma, Non-Small-Cell Lung↗
PubMed1995

Clinical pharmacokinetics and pharmacodynamics of paclitaxel: a 3-hour infusion versus a 24-hour infusion.

The present study was conducted to compare the pharmacokinetics and pharmacodynamics (PD) of paclitaxel between Phase I trials of 3- and 24-h infusions and to determine the most informative pharmacokinetic parameter to describe the PD. Twenty-seven patients were treated in a Phase I study of paclitaxel by a 3-h infusion at one of six doses: 105, 135, 180, 210, 240, and 270 mg/m2. Pharmacokinetic data were obtained from all patients. Paclitaxel concentrations were measured in the plasma and urine using HPLC. The pharmacokinetics and PD were compared with those of a Phase I trial of paclitaxel by a 24-h schedule previously performed. The maximum tolerated dose of paclitaxel by a 3-h infusion was determined to be 240 mg/m2. The major toxicities were granulocytopenia, neuromuscular toxicities, and hypotension. Apparent differences in pharmacodynamic relationships for the change in granulocytes with dose, peak concentration, and areas under the concentration versus time curve were observed between the 3- and 24-h schedules. However, the relationship between the duration of plasma concentration above 0.05 microM and the change in granulocytes could be fitted to the same sigmoid maximum effect model in either schedule (P < 0.01). There were no clear relationships between peripheral neuropathy or hypotension and any pharmacokinetic parameters. The pharmacokinetics and PD of paclitaxel were schedule dependent. The duration of plasma concentration above 0.05 microM could be a common pharmacokinetic parameter predicting granulocytopenia for both schedules.

Agranulocytosis↗
PubMed1994

Effect of suramin on p34cdc2 kinase in vitro and in extracts from human H69 cells: evidence for a double mechanism of action.

We examined the effect of suramin, an anticancer agent and a functional analog of naturally occuring glycosaminoglycans, on p34cdc2 kinase. We find that suramin strongly inhibits the catalytic activity of purified p34cdc2 kinase (IC50 approximately 4 microM), whereas it only weakly inhibits the p13-agarose precipitated kinase activity from nuclear and cytoplasmic extracts of the asynchronous H69 human small cell lung cancer cells. We also find that the tyrosine phosphorylation of p34cdc2 kinase in the nuclear extract is increased about twice when the extracts are preincubated with 50 microM of suramin prior to the p13-agarose precipitation. We propose that this increase might result from the inhibitory effect of suramin towards p34cdc2-specific tyrosine phosphatases. These results suggest both a direct and an indirect effect of suramin on p34cdc2 kinase. We also find that heparin is a potent inhibitor of purified cdc2 kinase (IC50 approximately 3.5 micrograms/ml). Therefore, glycosaminoglycans might be physiological regulators of p34cdc2 kinase in vivo.

Antineoplastic Agents↗
PubMed1994

Establishment of a human small-cell lung-cancer subline resistant to okadaic acid.

Okadaic acid (OA), a specific protein phosphatase inhibitor, has various biological functions. To elucidate the mechanism of OA resistance, we have established a small-cell lung-cancer subline (H69/OA100) resistant to the growth-inhibitory effect of OA; this was done by using the parental cell line (H69) and increasing the concentration of OA. H69/OA100 was about 8 times more resistant to OA than H69. Intracellular retention of the fluorescent OA derivative in H69/OA100 was the same as that in H69. The catalytic activity of protein phosphatase from H69/OA100 was significantly reduced compared with that from H69. The protein phosphatase from H69/OA100 was 3.6 times more resistant to OA than that from H69. We examined the effect of OA on the activity of the immunoprecipitated protein phosphatase type I (PPI) and type 2A (PP2A) from the 2 cell lines. The PPI and PP2A from H69/OA100 showed more resistance to OA than those from H69. We next examined the effect of OA on the cell cycle of H69 and H69/OA100. In H69, G2/M block was observed at an OA concentration of 30 ng/ml whereas in H69/OA100, no G2/M block was observed at concentrations up to 100 ng/ml OA. We finally evaluated the amount of p34cdc2 kinase expression and the phosphorylation status of p34cdc2. There was no difference in p34cdc2 expression between H69 and H69/OA100 at several concentrations of OA. However, dephosphorylation of p34cdc2 was observed at 30 ng/ml OA in H69, but not in H69/OA100 up to 100 ng/ml OA. These data suggest that the resistance to OA and the resistance of the cell-cycle block to OA in H69/OA100 might be due to alteration of protein phosphatase activity.

Base Sequence↗
PubMed1994

Reversal of multidrug resistance by tyrosine-kinase inhibitors in a non-P-glycoprotein-mediated multidrug-resistant cell line.

We have already established a human leukemia sub-line resistant to the growth-inhibitory effect of TPA (12-O-tetradecanoylphorbol 13-acetate) (K562/TPA) derived from K562. K562/TPA was found to be a non-P-glycoprotein-mediated multidrug-resistant cell line, in which intracellular drug accumulation was not reduced. In K562/TPA, adriamycin (ADM) was distributed mainly in the cytoplasm and was scarcely observed in the nucleus. We determined the relative levels of multidrug-resistance-associated protein (MRP), which was recently identified as the novel transporter. The relative levels of MRP in K562/TPA were the same as in K562. Although the catalytic activity of K562/TPA topoisomerase II was about half that of the parental cells, resistance to other drugs could not be explained by topoisomerase-II activity. To elucidate the mechanism of drug resistance in K562/TPA, we tried to find chemicals that would reverse the drug resistance. Tyrosine-kinase inhibitors enhanced the cytotoxicity of anti-neoplastic drugs against K562/TPA. Therefore we examined the modification of nuclear ADM accumulation in K562/TPA by one of these tyrosine-kinase inhibitors, genistein. Although the amount of ADM was decreased in the nuclei of K562/TPA cells, it was significantly increased after incubation in the presence of genistein. The formation of DNA single-strand breaks by ADM, etoposide, and ACNU was significantly lower in K562/TPA than in K562, but was significantly increased in the presence of genistein. These results suggest that genistein could overcome drug resistance by enhancing the accumulation of drug into the nuclear fraction of K562/TPA.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Ouabain-resistant non-small-cell lung-cancer cell line shows collateral sensitivity to cis-diamminedichloroplatinum(II) (CDDP).

We have reported that the cellular uptake of cis-diamminedichloroplatinum(II) (CDDP) was inhibited by an Na+,K(+)-adenosine triphosphatase (ATPase) inhibitor, ouabain, in a human non-small-cell lung-cancer cell line, PC-14, but not in its CDDP-resistant cell line, PC-14/CDDP. [3H]Ouabain binding of PC-14/CDDP was about 50% lower than that of PC-14. Accordingly, we speculated that a decrease in Na+,K(+)-ATPase activity in PC-14/CDDP might contribute to the decrease in cellular CDDP accumulation. To clarify the relationship between the activity or expression of Na+,K(+)-ATPase and cellular CDDP accumulation, we established an ouabain-resistant non-small-cell lung-cancer cell line (PC-14/OB300), which showed 1.9-fold resistance to the cytotoxicity of ouabain. Interestingly, this cell line was 4.2-fold more sensitive to CDDP than PC-14. The accumulation of CDDP in PC-14/OB300 was increased to 2.7-fold that in PC-14. This elevation of CDDP accumulation was not considered to be caused by increased passive diffusion, because the accumulation of CDDP in PC-14/OB300 was also inhibited by ouabain compared to PC-14. As one of the indices of Na+,K(+)-ATPase activity, we determined cellular 86Rb+ influx rates. The 86Rb+ influx rate was 1.5-fold higher in PC-14/OB300 and fell to 0.7-fold in PC-14/CDDP compared with PC-14. The mRNA expression of Na+,K(+)-ATPase was increased in PC-14/OB300 and decreased in PC-14/CDDP. There was no difference in cellular [3H]ouabain binding between PC-14/OB300 and PC-14. It is possible that Na+,K(+)-ATPase of PC-14/OB300 has a different affinity for ouabain from that of PC-14. Our results suggest that the enzyme activity or the level of expression of Na+,K(+)-ATPase may contribute to the cellular uptake of CDDP and determine the sensitivity to CDDP.

Adenocarcinoma↗