Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “resistant”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24Linked to original sources
PubMed2000

Characterisation of methicillin-resistant Staphylococcus aureus from Kuwait hospitals with high-level fusidic acid resistance.

Forty-seven fusidic acid- and methicillin-resistant Staphylococcus aureus isolates from clinical samples in four hospitals in Kuwait were studied for their relatedness by biotyping and pulsed-field gel electrophoresis (PFGE) and for the genetic location of their resistance determinants. Forty-four isolates were resistant to gentamicin, kanamycin and neomycin. Forty-one isolates were resistant to erythromycin and trimethoprim, 10 were resistant to chloramphenicol and four were resistant to ciprofloxacin. They contained two or three plasmids of c. 28, 2.8 and 1.8 kb. Genetic studies demonstrated that resistance to cadmium, propamidine isethionate and ethidium bromide were linked and were carried on the c. 28-kb plasmid. Chloramphenicol resistance was encoded by the 2.8-kb plasmid in resistant isolates. No resistance was associated with the 1.8-kb plasmid and this was considered to be a cryptic plasmid. Resistance to fusidic acid, methicillin, benzylpenicillin, gentamicin, kanamycin, neomycin, tetracycline, trimethoprim, erythromycin and ciprofloxacin were located on the chromosome. All the isolates produced urease, but varied in the production of haemolysins, pigments, lipase and lecithinase and were classified into nine biotypes. In contrast, PFGE divided the isolates into two major patterns with one PFGE type constituting the majority of isolates in all four hospitals. The presence of the dominant PFGE pattern in all four hospitals suggests that it is an epidemic MRSA clone with the capacity to spread. Infection control measures should be directed towards restricting the further spread of this clone.

Anti-Bacterial Agents↗
PubMed2006

Comparison of prevalence, antimicrobial resistance, and occurrence of multidrug-resistant Salmonella in antimicrobial-free and conventional pig production.

Conventional swine production evolved to routinely use antimicrobials, and common occurrence of antimicrobial-resistant Salmonella has been reported. There is a paucity of information on the antimicrobial resistance of Salmonella in swine production in the absence of antimicrobial selective pressure. Therefore, we compared the prevalence and antimicrobial resistance of Salmonella isolated from antimicrobial-free and conventional production systems. A total of 889 pigs and 743 carcasses were sampled in the study. Salmonella prevalence was significantly higher among the antimicrobial-free systems (15.2%) than the conventional systems (4.2%) (odds ratio [OR] = 4.23; P < 0.05). Antimicrobial resistance was detected against 10 of the 12 antimicrobials tested. The highest frequency of resistance was found against tetracycline (80%), followed by streptomycin (43.4%) and sulfamethoxazole (36%). Frequency of resistance to most classes of antimicrobials (except tetracycline) was significantly higher among conventional farms than antimicrobial-free farms, with ORs ranging from 2.84 for chloramphenicol to 23.22 for kanamycin at the on-farm level. A total of 28 antimicrobial resistance patterns were detected. A resistance pattern with streptomycin, sulfamethoxazole, and tetracycline (n = 130) was the most common multidrug resistance pattern. There was no significant difference in the proportion of isolates with this pattern between the conventional (19.5%) and the antimicrobial-free systems (18%) (OR = 1.8; P > 0.05). A pentaresistance pattern with ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline was strongly associated with antimicrobial-free groups (OR = 5.4; P = 0.01). While showing the higher likelihood of finding antimicrobial resistance among conventional herds, this study also implies that specific multidrug-resistant strains may occur on antimicrobial-free farms. A longitudinal study with a representative sample size is needed to reach more conclusive results of the associations detected in this study.

Animal Husbandry↗
PubMed2001

[Establishment of the drug resistant cell line of choriocarcinoma and the reversal of drug resistance by transfection of human interleukin 2 gene].

OBJECTIVE: To establish the drug-resistant cell line of choriocarcinoma and to study the transfection of the human interleukin 2 (hIL-2) gene into the established drug resistant cell line and investigate the reversal of the multidrug resistance. METHODS: The resistant cell line was established by pulse exposed choriocarcinoma cell line JEG-3 to etopside (VP-16) for ten months. The recombinant plasmid containing pcDNA3.1(+)-hIL-2 gene was constructed. The drug resistant cell line was transfected with the constructed plasmid by lipofectin, and the tumor cell colonies containing the IL-2 sequence were selected by genetin. The expression of hIL-2 and drug resistant-related genes was detected by reverse transcript polymerase chain reaction. The chemosensitivity of the gene-transfected tumor cells and the non transfected cell lines to methetraxate, VP-16, kengshengmycine, paclitaxol and 5-fluorouracil was determined by the methyl thiazolyl tetrazolium cytotoxicity assay. RESULTS: The transfected cells expressed human hIL-2 gene, and showed the reversal of multidrug resistance by methyl thiazolyl tetrazolium assay. The transfected cells expressed no multidrug resistance gene-1 (MDR1) on mRNA level. Drug resistance index to VP-16 decreased from 38.7 to 6.0 and 6.1, the index to methetraxate decreased from 14.5 to 2.6 and 2.5, to methetraxate from 13.0 to 2.0. CONCLUSION: The transfection of hIL-2 gene into the drug resistance cell line of choriocarcinoma can modulate the MDR1 expression on the mRNA level, and reverse the drug resistance.

Choriocarcinoma↗
PubMed2006

[Analysis of the macrolide resistance gene in penicillin-resistant Streptococcus pneumoniae].

We examined the penicillin and macrolide resistance of 496 strains of Streptococcus pneumoniae (S. pneumoniae) isolated at Showa University Hospital from November 2004 to May 2005. According to the classification established by the Clinical and Laboratory Standards Institute, the ratio of penicillin susceptible S. pneumoniae (PSSP) was 25.8%, penicillin intermediate S. pneumoniae was 35.9% and penicillin resistant S. pneumoniae (PRSP) was 38.3%. The ratios of macrolide resistant S. pneumoniae were 85.3% for erythromycin and 76.2% for clarithromycin. S. pneumoniae strains were isolated mainly from pediatric patients, and the ratios of PRSP were similar between outpatients (39.8%) and inpatients (45.6%). We screened for mutations in pbp1a, pbp2b and pbp2x, and the retention rate of the macrolide resistance genes, ermB and mefA in 90 strains isolated in the same period. Seventy two strains had at least one mutation in the pbp genes. Interestingly, some of the penicillin susceptible strains had one or two pbp mutations, suggesting a progressive genetic acquirement of penicillin resistance. In screening for retention of the macrolide resistance genes, we found that 42 strains(46.7%) had ermB, 19 strains (21.1%) had mefA and 13 strains (14.4%) had both ermB and mefA. The possession of resistance genes and the minimal inhibitory concentration indicate that the resistance to erythromycin and clarithromycin were induced by ermB or mefA, and the resistance to clindamycin was induced only by ermB. Among the 72 strains with pbps mutations, 65 strains (90.3%) had ermB or mefA or both. Together, these results show that the strains with pbp mutations were being selected and, after acquiring the macrolide resistance gene, transform to multidrug resistant S. pneumoniae.

Drug Resistance, Multiple, Bacterial↗
PubMed1996

Evolution of resistance in Staphylococcus aureus in Australian teaching hospitals. Australian Group on Antimicrobial Resistance (AGAR).

OBJECTIVE: To assess the changes in antibiotic resistances in Staphylococcus aureus, both methicillin-susceptible and methicillin-resistant strains, in Australia. DESIGN: Retrospective review of data collected annually. SETTING: Twenty metropolitan teaching hospitals in the six States of Australia and the Australian Capital Territory from 1988 to 1994. OUTCOME MEASURES: Changes in prevalence and resistance rates of methicillin-resistant S. aureus (MRSA) and methicillin-susceptible strains, based on antibiotic susceptibility testing of clinical isolates of S. aureus. RESULTS: Prevalence of MRSA has remained constant on the eastern seaboard of Australia. A distinctive strain of MRSA emerged in Western Australia which had different antimicrobial susceptibilities. Resistances emerged in MRSA strains from eastern Australia, principally to ciprofloxacin and rifampicin, while resistance to fusidic acid remained stable and resistance to chloramphenicol significantly declined. Resistances in methicillin-susceptible strains remained fairly stable, except for a decline in resistance levels for tetracycline. High levels of resistance were seen to penicillin, moderate levels to erythromycin and low levels to trimethoprim and fusidic acid in methicillin-susceptible strains. CONCLUSIONS: The continued high prevalence of and increasing resistance in MRSA in some Australian hospitals have meant that some strains are now untreatable with oral antibiotics.

Australia↗
PubMed1998

Levels of multidrug resistance (MDR1) P-glycoprotein expression by human breast cancer correlate with in vitro resistance to taxol and doxorubicin.

To determine whether multidrug resistance (MDR1) P-glycoprotein (Pgp) expression correlated with clinical MDR1-related drug resistance, we established a protocol for quantitative measurement of Pgp expression and in vitro drug resistance in doxorubicin resistant MCF7 breast cancer cell lines and 359 freshly resected specimens of breast carcinoma. Pgp expression was detected with 4E3, UIC2, and JSB-1 monoclonal antibodies using flow cytometry and immunohistochemistry (IHC). Pgp function was determined using PSC833 in a drug resistance-reversal assay and with a three-dimensional agarose-based extreme drug resistance assay. MCF7 calibrator cell lines expressed Pgp, which was functional and in proportion to the degree of drug resistance. Flow cytometry, UIC2 shift assays, IHC scores, and determination of absorbance products by image analysis were all highly correlated (r > 0.9). Overall Pgp expression increased from 11% in untreated patients to 30% in patients who had previously received chemotherapy. Compared with Pgp-negative tumors, a significant increase in doxorubicin and Taxol resistance was seen for breast cancers that expressed Pgp, regardless of prior treatment. A strong correlation between the degree of Pgp expression and in vitro resistance to Taxol and doxorubicin (but not to 5-fluorouracil) was found when either IHC scores or image analysis-based methods were used to quantify Pgp expression (n = 185, P < 0.0001). The degree of Pgp expression strongly correlated with the degree of drug resistance in the clinical specimens studied. These data suggest that (a) Pgp contributes to clinical MDR1-related drug resistance, and (b) both intrinsic and acquired expression of Pgp in breast cancer may contribute in part to therapeutic failure and relapse.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

Establishment of a human leukemia subline resistant to the growth-inhibitory effect of 12-O-tetradecanoylphorbol 13-acetate (TPA) and showing non-P-glycoprotein-mediated multi-drug resistance.

We have previously reported that K562/ADM, a typical P-glycoprotein-mediated multi-drug-resistant cell line, is cross-resistant to the growth-inhibitory effect of 12-O-tetradecanoylphorbol 13-acetate (TPA) and non-TPA type tumor promoters. To elucidate the mechanism of cross-resistance to tumor promoters in K562/ADM, we have established a K562 subline resistant to TPA-induced growth inhibition by exposing K562 cells to N-methyl-N'-nitro-N-nitrosoguanidine for 24 hr followed by continuous exposure to TPA. A K562 subline resistant to the TPA-induced growth inhibition, termed K562/TPA, was selected by a limiting dilution technique. K562/TPA was more than 500-fold resistant to TPA compared with parental K562 cells. K562/TPA showed cross-resistance to etoposide, teniposide, adriamycin (ADM), vincristine, vindesine and 3-[(4-amino-2-methyl-5-pyrimidinyl)] methyl-1-(2-chloroethyl)-1-nitrosourea, but showed collateral sensitivity to cisplatin. Although K562/ADM was not cross-resistant to 3'-deamino-3'-morpholino-13-deoxo-10-hydroxycarminomycin (MX2), an anthracycline derivative, K562/TPA was cross-resistant to MX2. By Northern blot analysis, K562/TPA did not express MDR-1. Accumulation of ADM by K562/TPA was no lower than that of K562 although that of K562/ADM was 5-fold lower than K562. We examined the subcellular distribution of ADM by fluorescence microscopy. The fluorescence of ADM was located in the nucleus of K562 and mainly in the cytoplasm of K562/TPA and K562/ADM. The distribution of ADM in K562/TPA, however, was different from that in K562/ADM. These results suggested that K562/TPA had a non-P-glycoprotein-mediated multi-drug-resistance phenotype and that the mechanism of drug-resistance in this cell line might be explained by an alteration in the intracellular drug distribution.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

Modulation of drug resistance in homoharringtonine-resistant C-1300 neuroblastoma cells with cyclosporine A and dipyridamole.

The development of resistance accounts for therapy failure in the majority of advanced cases of neuroblastoma in children. A new transplantable murine C-1300 neuroblastoma cell line was developed in vitro, by repeated exposure of a sensitive cell line to increasing, but sublethal, doses of Homoharringtonine (HHT). The ED50 of the highly resistant cells for HHT, using a standard agar colony assay, is 480 ng/ml, compared with 13 ng/ml for the sensitive parental line. The resistant cells have cross-resistance to a number of other agents, including adriamycin, vinca alkaloids, melphalan, and CCNU. Western blot analysis revealed progressive increases in P-glycoprotein, parallel to the graded development of resistance with a 29-fold elevation in the highest resistant cells. High-performance liquid chromatography (HPLC) indicated that resistant cells have a significantly lower uptake of HHT than parental sensitive cells. cyclosporine A (CsA) and dipyridamole (DPM) could modulate the acquired resistance and completely restore the cytotoxic effects of HHT and adriamycin as determined by the clonogenic assay. The reversal of resistance by CsA and DPM was dose dependent. With the relative low toxicity of dipyridamole and CsA in doses required for modulation of resistance, these agents may be candidates for clinical utilization in chemotherapy of resistant neuroblastoma.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2006

Tebufenozide resistance selected in Plutella xylostella and its cross-resistance and fitness cost.

A susceptible strain of diamondback moth, Plutella xylostella (L.), was used to select for resistance to tebufenozide in the laboratory. After continuous selection with tebufenozide 17 times during 35 generations, a resistant strain was achieved with high resistance to tebufenozide (RR 93.8). Bioassay revealed that this strain showed high cross-resistance to abamectin (RR 35.7), methoxyfenozide (29.1) and JS118 (16.5), and a little to deltamethrin (3.9), but no obvious cross-resistance was found to cypermethrin (1.3), fipronil (1.3), trichlorfon (1.1), chlorfenapyr (1.0), phoxim (0.9) and acephate (0.8). The resistant and susceptible insects had similar development rates, but life table tests indicated that the resistant strain showed reproductive disadvantages, including decreased copulation rate, reproductivity and hatchability. When compared with the susceptible strain, the resistant insects had a relative fitness of only 0.3. This indicated that tebufenozide resistance selected under laboratory conditions had considerable fitness costs in this pest, and therefore rotational use of insecticides without cross-resistance is recommended to delay development of resistance.

Animals↗
PubMed1988

Comparison of glutathione S-transferase activity between drug-resistant and -sensitive human tumor cells: is glutathione S-transferase associated with multidrug resistance?

We have studied the levels of glutathione S-transferase in drug-resistant and -sensitive human tumor cell lines to examine a possible involvement of glutathione S-transferase (GST) in multidrug resistance mechanisms. No increase in the activity of glutathione S-transferase was detected in myelogenous leukemia K562 resistant to adriamycin (K562/ADM), ovarian carcinoma cell line A2780 resistant to adriamycin (2780AD), or acute lymphoblastic leukemia cell line CCRF-CEM resistant to vinblastine (CEM-VLB100), compared with the drug-sensitive parent tumor cells. The human breast cancer cell lines Hattori and MCF-7 had a 12- to 63-fold lower level of glutathione S-transferase activity than K562, A2780, CCRF-CEM, and their drug-resistant sublines. Induction of ADM resistance in Hattori did not increase the activity of glutathione S-transferase. However, induction of colchicine resistance in MCF-7 resulted in a 70-fold increase in the activity of glutathione S-transferase. A revertant of the colchicine-resistant MCF-7 contained a level of glutathione S-transferase activity similar to that of the resistant subline. The increase of glutathione S-transferase activity did not alter the sensitivity of the cell to cytotoxic drugs. The increased activity was due to the appearance of glutathione S-transferase pi, as shown by enzyme inhibition using anti-glutathione S-transferase pi antibody. Our findings indicate that increased cellular glutathione S-transferase activity is not associated with the development of multidrug resistance.

Antineoplastic Agents↗
PubMed1988

Imazaquin and chlorsulfuron resistance and cross resistance in mutants of Chlamydomonas reinhardtii.

Chlorsulfuron and/or imazaquin resistant mutants of Chlamydomonas reinhardtii strain CW15 have been obtained and shown to have actolactate synthase (ALS) with altered sensitivity to one or both of these herbicides. Herbicide resistance in the three mutants described is allelic, and resistance appears to result from a dominant or semidominant mutation in a single, nuclear gene. Imazaquin and chlorsulfuron resistant ALS from imazaquin and chlorsulfuron resistant mutants, together with single-gene Mendelian inheritance of these phenotypes, suggests that ALS is the sole site of action of the two herbicides in Chlamydomonas. A high degree of cross resistance between the two herbicides was found in only one mutant. This mutant (IMR-13) was selected for resistance to imazaquin and has a high level of in vitro resistance to both imazaquin (270-fold increased I50) and chlorsulfuron (900-fold increased I50). In another mutant selected for resistance to imazaquin (IMR-2), hyper-sensitivity to chlorsulfuron was found. A mutant selected for resistance to chlorsulfuron (CSR-5), had a substantial degree of resistance of chlorsulfuron (80-fold increased I50), but not to imazaquin (7-fold increased I50).

Acetolactate Synthase↗
PubMed1992

Cross-resistance of drug-resistant murine P388 leukemias to taxol in vivo.

The antimicrotubule agent taxol (NSC 125973) has shown clinical antitumor activity against several classically refractory tumors. We developed a drug-resistance profile for taxol using ten drug-resistant P388 leukemias to identify potentially useful guides for patient selection for further clinical trials of taxol and possible non-cross-resistant drug combinations with taxol. Multidrug-resistant P388 leukemias exhibited either clear (leukemia resistant to amsacrine) or marginal cross-resistance (leukemias resistant to doxorubicin, actinomycin D, and mitoxantrone) to taxol. Leukemias resistant to vincristine (non-multidrug-resistant leukemia), camptothecin, melphalan, cisplatin, 1-beta-D-arabinofuranosylcytosine, and methotrexate were not cross-resistant to taxol. The data suggest that (1) it may be important to exclude or to monitor with extra care patients who have previously been treated with amsacrine, doxorubicin, actinomycin D, or mitoxantrone and (2) a combination of one of the non-cross-resistant drugs and taxol might exhibit therapeutic synergism.

Animals↗
PubMed1993

Decreased resistance to N,N-dimethylated anthracyclines in multidrug-resistant Friend erythroleukemia cells.

Doxorubicin-resistant Friend erythroleukemia cells, line F4-6 ADM2R, were selected by exposure of wild-type F4-6 cells to doxorubicin concentrations of up to 1 microgram/ml. In these cells, increased expression of multidrug resistance (MDR) genes was demonstrated by Northern blot analysis. The growth-inhibitory effect of doxorubicin, daunorubicin, N,N-dimethyldoxorubicin, N,N-dimethyldaunorubicin, morpholinodoxorubicin, and pyrromycin was comparatively investigated in resistant and wild-type cells. The doxorubicin-resistant F4-6 cells showed approx. 200-fold resistance to doxorubicin and about 100-fold resistance to daunorubicin with respect to the drug-sensitive counterpart. A dramatic decrease in resistance was observed for the N,N-dimethylated derivatives of doxorubicin and daunorubicin as well as for the N,N-dimethylated natural anthracycline pyrromycin and for morpholinodoxorubicin. Uptake studies using [14C]-daunorubicin and [14C]-N,N-dimethyldaunorubicin in resistant F4-6 cells showed a decreased accumulation of daunorubicin but no significant reduction in N,N-dimethyldaunorubicin accumulation as compared with the wild-type cells. Treatment with verapamil led to increased intracellular levels of daunorubicin in resistant cells, whereas an excess of N,N-dimethyldaunorubicin did not have this effect. Thus, the decreased resistance of the doxorubicin-resistant F4-6 cells to the N-alkylated anthracyclines may at least in part be due to a reduced affinity of these compounds for the efflux pump. The results indicate that the dimethylation of the amino group of the anthracycline sugar moiety and its incorporation within a morpholinyl ring may overcome MDR by similar mechanisms.

Antibiotics, Antineoplastic↗
PubMed1994

V79 Chinese hamster lung cells resistant to the bis-alkylator bizelesin are multidrug-resistant.

Bizelesin (U-77779) is a highly potent bis-alkylating antitumor agent that is effective against several tumor systems in vitro and in vivo. V79 cells that were 125- to 250-fold resistant to bizelesin developed after constant exposure to gradually increasing concentrations of the drug. Resistant cells exhibited a multidrug-resistant phenotype and genotype as indicated by cross-resistant to several structurally and functionally unrelated drugs, e.g., colchicine, actinomycin D, and Adriamycin, and overexpression of mdr mRNA. Very low levels of cross-resistance to the alkylating agents cisplatin and melphalan were seen. Multidrug-resistant mouse leukemia (P388/Adriamycin-resistant) and human (KB/vinblastine-resistant) cells were also resistant to bizelesin. Bizelesin resistance was unstable and decreased when cells were grown in the absence of the drug. Resistant and sensitive cell lines had similar levels of glutathione, and bizelesin cytotoxicity for resistant cells was not markedly affected by treatment with buthionine sulfoximine. Cross-resistance between bizelesin and several of its analogs is reported.

Alkylating Agents↗
PubMed1999

Drug resistance among clinical isolates of frequently encountered bacterial species in central Europe during 1975-1995. Study Group Bacterial Resistance of the Paul-Ehrlich-Society for Chemotherapy.

A multicenter study for monitoring antimicrobial drug resistance in clinical isolates of the family Enterobacteriaceae, Pseudomonas aeruginosa, Staphylococcus and Enterococcus species in central Europa conducted by the Study Group Bacterial Resistance of the Paul-Ehrlich-Society for Chemotherapy has been ongoing since 1975. Between 1975 and 1995 susceptibility data on almost 60,000 bacteria, which were isolated and sampled under a common protocol by laboratories from Austria, Germany and Switzerland, were collected. These bacterial isolates were known by the respective investigators to have caused infections. From 1975 to the mid-80s none of the bacterial species examined showed an increase in resistance. The frequency of resistance in klebsiellae and Staphylococcus aureus to some antibiotics even declined. In 1990 and particularly in 1995, a clear increase in resistance for a number of antibiotic-organism pairs was observed. Resistance rates to fluoroquinolones increased in all species under investigation. In Escherichia coli the increase of resistance to ampicillin, co-trimoxazole and gentamicin was remarkable. Resistance to imipenem increased in P. aeruginosa. Resistance to cephalosporins, on the other hand, remained largely unchanged in gram-negative bacilli. Between 1990 and 1995, the prevalence of oxacillin resistance increased from 1.7 to 12.9% in S. aureus and from 15.8 to 55.8% in coagulase-negative staphylococci, whereas staphylococcal and enterococcal resistance to glycopeptides was still rare.

Anti-Bacterial Agents↗
PubMed1990

Patterns of cross-resistance in a multidrug-resistant small-cell lung carcinoma cell line.

H69AR is a multidrug-resistant human small-cell lung carcinoma cell line that was selected in doxorubicin and has previously been shown to be cross-resistant to a variety of natural-product-type anticancer drugs. H69AR is unlike many other multidrug-resistant cell lines in that it does not overexpress P-glycoprotein. In the present study, the drug sensitivity and cross-resistance patterns of H69AR cells were further characterized. A total of 15 drugs belonging to a number of chemical classes were screened. These compounds included anthracyclines, DNA binders (anthrapyrazoles, benzothiopyranoindazoles, and pyrazoloacridines), and lipophilic antifolates. The alkylating agent melphalan and the antimetabolite cytosine arabinofuranoside (Ara-C) were also tested. In general, the drug sensitivity and cross-resistance profiles of H69AR cells were consistent with those reported by others using other drug-resistant cell lines. However, there were several unexpected instances of cross-resistance. Thus, the H69AR cell line was more resistant than its parent cell line to the potent 3'-deamino-3'-(3-cyano-4-morpholinyl) doxorubicin, bisantrene, the pyrazoloacridine PD 114541, Ara-C, and melphalan. In addition, no cross-resistance to the four lipophilic antifolates tested, including trimetrexate, was found. The absence of a consistent pattern among the various drug-resistant cell lines indicates that assumptions about the efficacy of anticancer drugs in multidrug resistance should be made with caution.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Cross-resistance pattern of cell lines selected for resistance towards different cytotoxic drugs to membrane-toxic phospholipids in vitro.

The synthetic ether lipids ET-18-OCH3 and BM41.440 and a derivative, hexadecylphosphocholine, were tested for inhibition of [3H]-thymidine uptake into a Chinese hamster ovarian cell line (AUXBl) and its multidrug-resistant subline selected for colchicine resistance (CHRC5). The activity of all three compounds against the multidrug-resistant subline was equal to or higher than that against the parent line. The same result was found for their activity against a human leukemic lymphoblastic cell line (CEM/O) and its methotrexate-resistant subline (CEM/MTX). In contrast, two multidrug-resistant cell lines selected for resistance to Adriamycin, the mouse leukemia cell line P388/ADR and the murine sarcoma cell line S180/ADR, expressed modest cross-resistance to the lipids as measured by thymidine uptake. Experiments performed using the trypan-blue dye-exclusion assay yielded comparable results, although this system revealed a slightly different sensitivity in showing the cytotoxicity of the drugs. By this assay, modest cross-resistance for ET-18-OCH3 and BM41.440 to Adriamycin was found only after 24 h incubation and decreased after 48 h incubation, with almost equal sensitivity to both drugs being shown by the parental (P388/W) and resistant lines (P388/ADR). Furthermore, findings from a human tumor-cloning assay were in accordance with these data, although they did not indicate cross-resistance for the P388/ADR cell line. These results suggest that certain ether lipids and derivatives might represent valuable anticancer drugs warranting further study in the setting of resistant disease.

Animals↗
PubMed1996

Cellular resistance to the antimelanoma immunotoxin ZME-gelonin and strategies to target resistant cells.

The development of cellular resistance to immunotoxins has been demonstrated in a variety of models and can involve a number of mechanisms. For the present study, an immunotoxin was utilized composed of an anti-melanoma antibody ZME-018 recognizing a 240-kDa surface glycoprotein (gp 240) and the plant toxin gelonin. Human melanoma cells (A375-M) were grown in the presence of increasing amounts of ZME-gelonin and a clonal variant (A-375-ZR) was developed that was 100-fold resistant to ZME-gelonin compared to parental cells. Scatchard analysis showed that the A375-M parental cells had 260 X 10(3) ZME-gelonin-binding sites/cell with relatively low affinity (5 nM). In contrast, resistant A375-ZR cells demonstrated a reduced number of low-affinity sites (160 x 10(3)/cel1), but showed a small number (47 x 10(3)) of higher-affinity sites (0.8 nM). Internalization rates and degradation rates of 125I-labeled ZME-gelonin were identical in both the parental and resistant cells. A375-ZR cells were found to be more resistant to vincristine and doxorubicin than were parental cells. Both cell lines were almost equally sensitive to native gelonin, 5-fluorouracil (5-FU), cisplatin. melphalan, carmustine, interferon gamma (IFNgamma) and IFNalpha. In addition. both cell lines were equally sensitive to another gelonin antibody conjugate that binds to cell-surface, GD2 (antibody 14G2A). However, resistant cells were twice as sensitive to the cytotoxic effects of etoposide than were parental cells. Finally, a variety of agents were tested in combination with ZME-gelonin against A375-ZR cells in an attempt to identify agents to augment immunotoxin cytotoxic effects against resistant cells. The agents 5-FU, cisplatin, IFNgamma, IFNalpha, and etoposide were the most effective in augmenting the cytotoxicity of ZME-gelonin against resistant cells. These studies suggest that development of resistance to one immunotoxin does not cause development of cross-resistance to other gelonin immunotoxins. Further, specific biological response modifiers and chemotherapeutic agents may be effective in augmenting the effectiveness of immunotoxins and specifically targeting or reducing the emergence of immunotoxin-resistant cells.

Antineoplastic Agents↗