Biomedical subjects

A Yokomizo

Publications and source records attributed to A Yokomizo.

25 records · Page 2Linked to original sources

PubMed1996

Enhanced coexpression of thioredoxin and high mobility group protein 1 genes in human hepatocellular carcinoma and the possible association with decreased sensitivity to cisplatin.

Thioredoxin (TRX), a disulfide-reducing intracellular protein, functions as a cellular defense mechanism against oxidative stress. In this study, we asked whether expression of TRX, glutathione-thiol transferase pi, and high mobility group protein 1 (HMG-1) genes is enhanced in human hepatocellular carcinoma and whether expression of these genes is associated with sensitivity to cisplatin. Both TRX and HMG-1 were co-overexpressed in almost all cancerous lesions in comparison to normal tissue in surgically resected hepatocellular carcinomas of 20 patients. Tumor sensitivity to cisplatin [cis-diamminedichloroplatinum (II)], but not to mitomycin C or doxorubicin, correlated with mRNA levels of TRX in cancer tissue. TRX and HMG-1 may be useful tumor markers, and TRX might be also a useful marker for sensitivity to cisplatin in human hepatocellular carcinomas.

Adult↗

PubMed1995

Cellular levels of thioredoxin associated with drug sensitivity to cisplatin, mitomycin C, doxorubicin, and etoposide.

Thioredoxin, a cellular thiol, functions as a self-defense mechanism in response to environmental stimuli, including oxidative stress. We first determined cellular levels of thioredoxin in several human bladder and prostatic cancer cell lines resistant to cis-diamminedichloroplatinum(II) (cisplatin). All cisplatin-resistant cell lines had much higher levels of thioredoxin than those in their drug-sensitive parental counterpart. We then, by introducing thioredoxin antisense expression plasmids into human bladder cancer T24 cells, established two bladder cancer cell lines that had decreased levels of thioredoxin. These thioredoxin antisense transfectants showed increased sensitivity to cisplatin and also to other superoxide-generating agents, i.e., doxorubicin, mitomycin C, etoposide, and hydrogen peroxide, as well as to UV irradiation, but not to the tubulin-targeting agents, vincristine, and colchicine. Cellular levels of thioredoxin thus appear to limit sensitivity to various superoxide-generating anticancer drugs in cancer cells.

Antineoplastic Agents↗

PubMed1995

Markedly decreased expression of glutathione S-transferase pi gene in human cancer cell lines resistant to buthionine sulfoximine, an inhibitor of cellular glutathione synthesis.

Buthionine sulfoximine (BSO) is a synthetic amino acid that irreversibly inhibits an enzyme, gamma-glutamylcysteine synthetase (gamma-GCS), which is a critical step in glutathione biosynthesis. We isolated three BSO-resistant sublines, KB/BSO1, KB/BSO2, and KB/BSO3, from human epidermoid cancer KB cells. These cell lines showed 10-to 13-fold higher resistance to BSO, respectively, and had collateral sensitivity to cisplatin, ethacrynic acid, and alkylating agents such as melphalan and nitrosourea. Cellular levels of glutathione S-transferase pi (GST-pi) and its mRNA in BSO-resistant cell lines were less than 10% of the parental cells. Nuclear run-on assay showed that the transcriptional activity of GST-pi was decreased in BSO-resistant cells, and transient transfection of GST-pi promoter-chloramphenicol acetyltransferase constructs revealed that the sequences between -130 and -80 base pairs of the 5'-flanking region wer at least partially responsible for the decreased expression of the GST-pi gene. By contrast, gamma-GCS mRNA levels were 3-to 5-fold higher in resistant cell lines than in KB cells, and the gamma-GCS gene was found to be amplified in the BSO-resistant cells lines. GST-pi mRNA levels appeared to be inversely correlated with gamma-GCS mRNA levels in BSO-resistant cells. We further established the transfectants, KB/BSO3-pi1 and KB/ BSO2-pi2, that overexpressed GST-pi, from KB/BSO3, after introducing a GST-pi expression plasmid. These two transfectants had similar levels in gamma-GCS mRNA, drug sensitivity to alkylating agents, and glutathione content at those of KB cells. These findings suggest that the cellular levels of GST-pi and gamma-GCS might be co-regulated in these novel BSO-resistant cells.

Blotting, Southern↗

PubMed1995

Non-P-glycoprotein-mediated atypical multidrug resistance in a human bladder cancer cell line.

A human bladder cancer cell line resistant to adriamycin (ADM), T24/ADM9 has been established in vitro by exposing T24 parent cells to progressively higher concentrations of the drug over a period of 12 months. The T24/ADM9 cells were found to be 9 times more resistant to ADM than the T24 parent, and showed various degrees of cross-resistance to an ADM derivative, vinea alkaloids and a DNA topoisomerase II (Topo II)-targeting agent, etoposide. No significant differences was observed in the cellular accumulation of ADM between the T24/ADM9 and T24 parent cells. A Northern blot analysis showed an overexpression of multidrug resistance-associated protein (MRP) mRNA, but no overexpression of multidrug resistance-1 (MDR1) mRNA was observed in the T24/ADM9 cells. A flow cytometric analysis showed that the MDR1 gene product, P-glycoprotein (Pgp), is not expressed on the T24/ADM9 cells. T24/ADM9 showed approximately the parental level of DNA Topo II catalytic activity. In Western blot and Northern blot analyses, however, the cellular level of DNA topo II was apparently much lower in T24/ADM9 than in the T24 parent. Thus, these results suggest that a decreased cellular level of DNA Topo II and an overexpression of MRP gene may be responsible for the expression of an MDR phenotype in the T24/ADM9 cells and that such non-Pgp-mediated, atypical MDR may develop in bladder cancer treated with chemotherapy including ADM.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1994

Possible involvement of multidrug-resistance-associated protein (MRP) gene expression in spontaneous drug resistance to vincristine, etoposide and adriamycin in human glioma cells.

The multidrug-resistance phenotype in human tumors is partly associated with over-expression of the 170 kDa-P-glycoprotein encoded by the multidrug-resistance-1 (MDR1) gene. Another related, but non-P-glycoprotein, multidrug-resistance-associated protein (MRP) gene encodes a 190 kDa-membrane ATP-binding protein. Glioblastoma multiforme is a highly malignant primary neoplasm of the central nervous system which is refractory to anti-cancer chemotherapy, but the mechanism underlying this drug resistance is unknown. Out of glioma cell lines, 2, namely IN500 and T98G, which had elevated MRP mRNA levels, showed the highest resistance to multiple anti-cancer agents such as etoposide, vincristine and adriamycin, and decreased intracellular accumulation of etoposide. In the remaining 5 cell lines, various degrees of sensitivity to adriamycin and etoposide appeared to correlate with their respective MRP mRNA levels. Our study proposes that MRP may be involved in spontaneous multidrug resistance in human gliomas.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1994

Increased expression of DNA topoisomerase I gene and collateral sensitivity to camptothecin in human cisplatin-resistant bladder cancer cells.

We established three cis-diamminedichloroplatinum(II) (cisplatin)-resistant cell lines, T24/DDP5, T24/DDP7, and T24/DDP10, by the stepwise exposure of T24 human bladder cancer cells to increasing concentrations of cisplatin. The resistance to cisplatin of T24/DDP5, T24/DDP7, and T24/DDP10 cells was 2.2-, 5.2-, and 8.4-fold that of the parental T24 cells, respectively. The cisplatin-resistant cell lines also showed an increased resistance to vincristine, although their sensitivities to Adriamycin and etoposide resembled that of T24. In contrast, the cisplatin-resistant cells developed a collateral sensitivity to (4s)-4,11-diethyl-4-hydroxy-9-[(4-piperidinopiperidino)carbonyl oxy]dione hydrochloride trithydrate, a camptothecin derivative, and its active metabolite, 7-ethyl-10-hydroxy-camptothecin, that targets DNA topoisomerase I. Both a Northern blot analysis and an immunoblot analysis demonstrated increased cellular levels of DNA topoisomerase I mRNA in the resistant cell lines. However, the expression of DNA topoisomerase II in the three resistant cell lines did not differ significantly from that in the T24 cells. No significant differences in the glutathione S-transferase pi levels were observed, although the intracellular content of glutathione in the T24/DDP7 cells was slightly but significantly increased. In addition, the intracellular platinum concentration correlated negatively with the degree of cisplatin resistance and was found to be significantly decreased in T24/DDP10 at an external cisplatin concentration of 20 micrograms/ml. These results suggest that the increased levels of DNA topoisomerase I mRNA thus play an important role in cisplatin resistance and produce a collateral sensitivity to (4s)-4,11-diethyl-4-hydroxy-9[(4-piperidinopiperidino)carbonylo xy]dione hydrochloride trithydrate and 7-ethyl-10-hydroxycamptothecin in these cisplatin-resistant bladder cancer cell lines. In addition, the presence of decreased intracellular cisplatin accumulation may also contribute to the acquisition of resistance to cisplatin in these cell lines.

Blotting, Northern↗

PubMed1994

[Atypical MDR].

Multiple drug resistance(MDR) is a major clinical obstacle in cancer chemotherapy. Acquirement of MDR phenotype in cancer cells is often associated with enhanced expression of human MDR-1 gene: MDR-1 gene codes membranous P-glycoprotein which catalyses energy-dependent outward transport of anticancer agents. By contrast, MDR cancer cell lines without overexpression of P-glycoprotein are called as atypical MDR (at MDR) cells. The acquirement of at MDR has been shown to be partly associated with altered DNA topoisomerase II. Furthermore, a new ATP binding cassette (ABC) family, MRP gene has just recently shown to involve in acquirement of at-MDR in cancer cell lines, which do not express both altered topoisomerase II and P-glycoprotein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗