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Biomedical subjects

J R Masters

Publications and source records attributed to J R Masters.

At least 55 records · Page 3Linked to original sources
PubMed1993

Hypersensitivity of human testis-tumour cell lines to chemotherapeutic drugs.

Metastatic testis tumours, in contrast to most other types of cancer, can be cured by drugs. To investigate which classes of chemotherapeutic drug are differentially toxic to testis-tumour cells, we compared the in vitro dose-response curves of 5 human testis and 5 bladder-cancer cell lines to 12 compounds. The testis cells were hypersensitive to drugs that interact directly with DNA (m-amsa, bleomycin, cisplatin, doxorubicin, methylnitrosourea, mitozolomide, etoposide, mitomycin-C), but little or no difference between the 2 cell types was seen following exposure to drugs whose mechanisms of action do not involve direct interaction with DNA (methotrexate, 5-fluorouracil, colchicine, vinblastine). We conclude that testis tumour cells are either less tolerant of, or have a reduced capacity to repair, DNA damage.

Antineoplastic Agents↗
PubMed1993

[Differential regulation of androgen receptor promoter in hormone-sensitive and -insensitive prostate carcinoma cells].

The sensitivity of prostate epithelial cells to androgens is mediated by the androgen receptor (AR). Analyses of cell lines in vitro and prostate carcinomas in vivo provide evidence that loss of AR expression parallels the loss of sensitivity to androgens. The aim of our work is to analyze the genetic control elements of the AR gene and answer the question of why these elements fail to function in hormone-insensitive prostate cancer cells. Therefore, we have cloned and fully sequenced a 5700 base pair sequence 5'-upstream of the AR gene. This DNA fragment contains promoter and enhancer elements that are active in androgen-sensitive but inactive in androgen-insensitive prostate cancer cell lines.

Androgens↗
PubMed1993

In vitro studies on the pathogenesis of bladder cancer.

Three methods for the culture of human urothelial cells in vitro are described: (1) the propagation of primary cultures and cell lines derived from normal urothelial cells, (2) the immortalization of normal urothelial cell lines with a temperature-sensitive SV40 large T antigen and (3) continuous cell lines derived from bladder cancers. Such cultures provide model systems for studying the factors that control the growth and differentiation of both normal and neoplastic urothelial cells, and for defining the morphological, biochemical and genetic changes associated with the development and progression of bladder cancer.

Cell Line, Transformed↗
PubMed1993

[Distribution pattern of urothelial associated glycoproteins in human bladder cancer cell lines in in vitro culture].

The distribution of four antibodies against urothelial-associated glycoproteins (UAGAb: Uro1, -5, -9, -10, SIGNET) was studied by dual parameter flow-cytometry (UAGAb and DNA staining) in normal non-urothelial cancer cell lines (2), normal urothelial cell lines (2) and bladder cell lines (5). When cell lines were compared as plateau monolayers, high proportions of Uro1 and Uro10 were found in all cell lines, in contrast to Uro5 and Uro9, both showing specificity for urothelial cells. Though being described as a pan-urothelial marker, Uro5 is not found in all cell lines. In two cell lines (RT4 and J82) three different growth states (exponential and plateau monolayer and multicellular spheroids were compared, and dependence on spatial configuration could be shown for Uro9. Cell cycle relation of expression was found for Uro1 and Uro10.

Cell Line↗
PubMed1992

The effect of retinoic acid on chemosensitivity of PA-1 human teratocarcinoma cells and its modulation by an activated N-ras oncogene.

Combination of chemotherapeutic drugs with agents that induce cell differentiation is a possible means of improving cancer chemotherapy. To explore this approach we used 4 cell lines established from the human teratocarcinoma-derived cell line PA-1; 2 retinoic acid (RA)-sensitive lines compared to 2 RA-resistant lines transformed by an activated N-ras oncogene. Equal numbers of colony-forming cells were exposed for 72 hr to 10(-6)M RA and subsequently to a range of concentrations of cisplatinum, etoposide or bleomycin. Enhanced cytotoxicity of cisplatin and etoposide (3- to 5-fold) was observed in the N-ras-transformed cell lines compared to the non-transformed lines. Treatment with RA caused an increase in the cytotoxicity of all 3 drugs to the 2 RA-sensitive cell lines. In contrast, a reduction of cytotoxicity was observed in the 2 N-ras-transformed lines. Our results indicate that sensitivity to cytotoxic agents can be increased by RA in RA-sensitive cells, but the opposite effect is seen in N-ras transformed, RA-resistant cells. Therefore, a general rationale for combination therapy with RA and cytotoxic drugs cannot be inferred.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1992

Screening of new anticancer agents in vitro using panels of human cell lines derived from non-seminomatous germ cell tumours and transitional cell carcinomas of the bladder.

Metastatic testis tumours are cured in over 80% of patients using combination chemotherapy, and this hypersensitivity is retained by the cells in vitro. To determine whether differential toxicity to testis tumour cells is useful in the screening of novel anticancer agents, we compared the toxicities of 12 compounds against panels of human bladder and testis tumour cell lines using a clonogenic assay. The compounds had screened negative against P388 in vivo, and had been retested using the human tumour colony forming assay (HTCFA) and in selected cases against human tumour xenografts. NSC 339004, chloroquinoxaline sulphonamide, was 7-fold more toxic to testis tumour than bladder cancer cells, comparing the mean of the concentrations reducing colony-forming ability by 70%. This was the only one of the compounds selected by the HTCFA shown to have clinical activity. Compound R was selectively toxic to the bladder cancer cells, and might be of value as an intravesical agent. These data indicate that panels of testis and bladder cancer cell lines might be a useful addition to the disease-oriented screening programme.

Antineoplastic Agents↗
PubMed1992

Fatty acid composition of normal and malignant cells and cytotoxicity of stearic, oleic and sterculic acids in vitro.

The aim of this study was to investigate the hypothesis that saturated fatty acids are differentially cytotoxic to cancer cells. Three studies were undertaken to: (1) measure the toxicities of stearic and oleic acids to normal and malignant cells in vitro, (2) assess if there is any relationship between toxicity and relative fatty acid composition and (3) determine whether the relative fatty acid composition of a cancer cell line could be modified by sterculic acid, an inhibitor of delta-9-desaturase. Stearic (18:0) and oleic (18:1) acids inhibited the colony-forming abilities of five human cancer cell lines and two non-neoplastic cell lines in a dose-dependent fashion. The concentration of oleic acid required to reduce colony formation ability by 50% was 2.5-6.0-fold greater than that of stearic acid. Addition of sterculic acid to a cancer cell line resulted in steady-state levels of stearic acid and increasing percentage of oleic acid.

Carcinoma, Transitional Cell↗
PubMed1992

O6-alkylguanine-DNA-alkyltransferase activity and nitrosourea sensitivity in human cancer cell lines.

The DNA repair enzyme, O6-alkylguanine-DNA-alkyltransferase (ATase), is thought to be the principal mechanism controlling resistance to nitrosoureas and related alkylating agents. We compared the sensitivities of five human testis and five bladder tumour cell lines to two nitrosoureas (N-nitroso-N-methylurea (MNU) and mitozolomide) with cellular levels of ATase. Enzyme levels ranged from 3 to 206 fmol mg-1 protein (0.1 x 10(4) to 5.1 x 10(4) molecules/cell) in the testis lines and from 11 to 603 fmol mg-1 (0.4 x 10(4) to 9.1 x 10(4) molecules/cell) in the bladder lines. Based on IC50s in an MTT assay, the testis tumour cell lines were, on average, four times more sensitive to MNU and six times more sensitive to mitozolomide than the bladder cell lines. The cytotoxicities of MNU and mitozolomide were closely related (R = 0.9). In the testis cell lines ATase activity (molecules/cell) was related to IC50s for mitozolomide (R = 0.97) but not MNU (R = 0.78). In the bladder cell lines and overall, ATase activity correlated with cellular sensitivity to neither agent. Relatively high levels of resistance occurred in cells expressing low levels of ATase, and amongst cell lines expressing high levels of ATase, large differences in IC50s were observed. These results support the suggestion that resistance to nitrosoureas can be mediated by mechanisms other than ATase and that at relatively high levels of expression, ATase does not confer resistance in proportion to its activity.

Antineoplastic Agents↗
PubMed1992

Does DNA flow cytometry give useful prognostic information in renal parenchymal adenocarcinoma?

DNA ploidy and S-phase fraction (SPF) were measured by flow cytometry on 381 paraffin blocks from 93 unselected primary renal parenchymal adenocarcinomas (RPA). The results were compared with tumour grade and T category and patient survival, with a mean follow-up of 87 months. Only 21% of the tumours were uniformly diploid and ploidy was heterogeneous in 49% of cases. DNA ploidy and SPF were significantly associated with grade, but not T category of disease. Both flow cytometric parameters were significantly related to survival in a univariate analysis. However, when tumour grade was taken into account, both DNA ploidy and SPF lost their prognostic significance. Thus, neither of these parameters gave prognostic information additional to that provided by tumour grade in unselected cases of primary RPA.

Adenocarcinoma↗
PubMed1991

Relationship between topoisomerase II level and chemosensitivity in human tumor cell lines.

Patients with metastatic testis tumors are generally curable using chemotherapy, whereas those with disseminated bladder carcinomas are not. We have compared levels of the nuclear enzyme topoisomerase II in three testis (SuSa, 833K, and GH) and three bladder (RT4, RT112, and HT1376) cancer cell lines which differ in their sensitivity to chemotherapeutic agents. The testis cell lines were more sensitive than the bladder lines to three drugs whose cytotoxicity is mediated in part by inhibiting topoisomerase II: amsacrine; Adriamycin; and etoposide (VP16). The frequency of DNA strand breaks induced by amsacrine was higher (1.5- to 13-fold) in the testis cells than in the bladder cells. The level of topoisomerase II-mediated DNA strand breakage in vitro, measured by filter trapping of amsacrine-induced protein:DNA cross-links, was similarly higher in nuclear extracts from the testis than the bladder cells. Western blot analysis showed a generally higher level of topoisomerase II protein in testis than in bladder cell nuclear extracts. Topoisomerase II protein expression broadly correlated with drug-induced strand breakage in both protein extracts and whole cells, but not with population doubling time. However, despite a 2- to 20-fold increased sensitivity to the different topoisomerase II inhibitors, the testis line 833K had a less than 2-fold higher level of topoisomerase II protein than that of the bladder line RT4. These results indicate that the level of expression of topoisomerase II is an important determinant of the relative chemosensitivity of testis and bladder tumor cell lines, but that additional factors must contribute to the extreme chemosensitivity of testis cells.

Amsacrine↗
PubMed1990

pSV3neo transfection and radiosensitivity of human cancer cell lines.

Immortalisation of human fibroblasts by transfection with a plasmid, pSV3neo, results in an increase in their radioresistance. The change in radiosensitivity may either be a consequence of transformation or due to expression of the SV40 T-antigen in pSV3neo. To investigate these two possibilities, we transfected pSV3neo into cells already transformed and immortalised. The radiosensitivities of three human bladder cancer cell lines were unaltered in clones expressing T-antigen, indicating that the changes observed in fibroblasts probably are a consequence of transformation, and not the presence of SV40 T-antigen.

Antigens, Viral, Tumor↗
PubMed1990

Inherent sensitivity and induced resistance to chemotherapeutic drugs and irradiation in human cancer cell lines: relationship to mutation frequencies.

Metastatic nonseminomatous testicular germ cell tumors are curable using combination chemotherapy in approximately 80% of patients. In contrast, most other patients with other types of cancer either present with or acquire drug-resistant disease following chemotherapy. Cell lines derived from testis tumors retain hypersensitivity to both drugs and radiation in vitro, thus providing a model system with which to investigate the genetic basis of hypersensitivity to these agents. This study compared the spontaneous and both ethyl methanesulfonate- and cisplatin-induced frequencies of mutation of 6-thioguanine resistance in 3 human bladder and 3 testis tumor cell lines and a bladder and a testis cell line with cisplatin resistance induced in vitro. The two tumor types showed similar frequencies of both spontaneous and induced mutation frequencies at this locus. Therefore, we failed to provide evidence for the hypothesis that the curability of testis tumors is associated with a low frequency of mutation to drug resistance.

Antineoplastic Agents↗
PubMed1990

The photodynamic effect of a pulsed dye laser on human bladder carcinoma cells in vitro.

The photodynamic effect of a pulsed flashlamp pumped dye laser on cultured human bladder carcinoma cells was studied. MGH-U1 cells were incubated for 1 h in dihaematoporphyrin either (DHE) and then exposed to green laser light (504 nm, 20 Hz) for varying laser power densities (50-100 mW/cm2 and exposure times (2-15 s), representing incident pulse energy fluences of 2.5-5 mJ/cm2 and energy densities of 0.1-1.5 J/cm2. The cell survival was measured by clonogenic assay and controls exposed to either laser light alone or DHE in the dark showed no cytotoxicity. Sensitised cells were killed by energy densities of less than 1 J/cm2 (LD90 = 0.54 J/cm2). This demonstrates the probable effectiveness of a pulsed dye laser for photodynamic therapy provided that pulse fluence are below the saturation threshold of the photosensitiser (10 mJ/cm2).

Carcinoma, Transitional Cell↗
PubMed1990

ThioTEPA pharmacokinetics during intravesical chemotherapy and the influence of Tween 80.

A pharmacokinetic study of randomised crossover design was carried out in which eight patients with recurrent stage pTa or pT1 transitional cell carcinoma of the bladder were given thioTEPA (30 mg) in distilled water or in 10% (v/v) Tween 80 (30 ml) intravesically for 2 h, followed 3 months later by the alternative treatment. ThioTEPA and its primary metabolite, TEPA, were measured in plasma and urine using a sensitive and specific chromatographic assay. Large differences between patients were observed in the proportion of thioTEPA absorbed, ranging from 20%-78%. Peak plasma levels of thioTEPA were observed within 1 h of intravesical administration. By 2 h after administration the plasma levels of TEPA were similar to those of thioTEPA and, in contrast to those of the parent compound, remained at a similar level over the next 4 h. The rate of absorption of thioTEPA was not influenced by Tween 80, but it did cause statistically significant increases in mean peak plasma levels (from 101 to 154 ng/ml) and mean AUC values (from 0.376 to 0.496 micrograms h per ml) and a decrease in the mean half-life (from 1.83 to 1.25 h). To obtain plasma levels similar to those achieved after instillation with thioTEPA alone, the dose should be reduced with Tween 80.

Absorption↗
PubMed1990

Biochemical basis of resistance to chemotherapy.

Recent progress in the understanding of drug resistance has led to the discovery of new targets for chemotherapy. By attacking the molecules that make cancer cells insensitive to chemotherapy, it is hoped that drug-resistant disease will respond to treatment. This review describes some of the latest advances in understanding of the biochemistry of drug resistance. Following a general introduction four areas of topical interest are discussed: (1) multidrug resistance and P-glycoprotein, (2) glutathione and its related enzymes, (3) topoisomerase II and (4) DNA repair.

Antineoplastic Agents↗
PubMed1990

Development and characterization of cisplatin-resistant human testicular and bladder tumour cell lines.

Cisplatin-resistant cells were derived in vitro from a human bladder carcinoma cell line (RT112) and a testicular tumour cell line (SuSa) by continuous exposure to increasing concentrations of cisplatin for 14 and 11 months, respectively. Both resistant cell lines had a four-fold level of resistance relative to their parental cell lines, comparing the cisplatin concentration to inhibit colony forming ability by 70%. These levels of resistance were retained in the absence of cisplatin for at least 3 months. In each case, four-fold fewer micronuclei were produced in the resistant lines by the same cisplatin concentrations. Cross-resistance to carboplatin and methotrexate was observed in both resistant cell lines, but neither line was resistant to doxorubicin. Isozyme and DNA analysis with hypervariable probes confirmed the origin of each resistant cell line from its parental line. Population doubling times and intermitotic times were similar in each of the pairs of cell lines. Karyotyping showed that the resistant cell lines had gained and lost marker chromosomes, but there were no changes common to both resistant cell lines.

Carcinoma, Transitional Cell↗
PubMed1989

Sensitivities of monolayers and spheroids of the human bladder cancer cell line MGH-U1 to the drugs used for intravesical chemotherapy.

The in vitro cytotoxicities of the four drugs most frequently used for intravesical chemotherapy (Adriamycin, epodyl, mitomycin C, Thiotepa) and epirubicin were compared using monolayers and multicellular tumor spheroids of the human bladder cancer cell line, MGH-U1. Adriamycin and epirubicin were most cytotoxic against monolayer cultures, whereas mitomycin C killed more cells in spheroids. Epodyl was least cytotoxic against both two- and three-dimensional cultures. Thiotepa was the only drug more cytotoxic to three- than two-dimensional cultures. Topographic analysis of bromodeoxyuridine-stained nuclei using image analysis indicated that Adriamycin selectively removed or killed superficial cells in multicellular tumor spheroids, but had little effect on DNA synthesis within the spheroids. In contrast Thiotepa killed cells throughout the spheroids. These in vitro data appear to reflect clinical experience using intravesical chemotherapy to treat superficial bladder cancer.

Administration, Topical↗