Variation In Drug Susceptibility Research Articles

Development and validation of a predictive model based on β-Klotho for head and neck squamous cell carcinoma

Head and neck epithelial tissue tumors may be identified as head and neck squamous cell carcinoma (HNSC). Numerous malignancies are encouraged by dysregulation of the FGF19-β-Klotho (KLB) axis in the tumor microenvironment. Using protein databases and RT-qPCR, we examined KLB expression in HNSC. In HNSC, higher KLB expression was linked to longer survival times and better prognoses. Furthermore, variations in drug susceptibility and immunological infiltration were noted according to KLB expression levels. These results underscore the importance of KLB in the course and management of HNSC by indicating that it may function as a possible prognostic marker and influence immunological and therapeutic responses in these individuals. Further study on HNSC is necessary to investigate KLB's potential as a therapeutic target and prognostic indicator.

In vitro drug susceptibility using a parasite-rescue and transformation assay of Leishmania (Mundinia) martiniquensis and Leishmania (Mundinia) orientalis amastigotes against antileishmanial drugs

Leishmaniasis is an emerging infectious disease in Thailand, with Leishmania martiniquensis and Leishmania orientalis identified as the primary causative agents among immunocompetent and immunocompromised individuals. Variations in drug susceptibility among different Leishmania species have been reported in different regions. Therefore, drug susceptibility assays are essential to assess the effectiveness of antileishmanial drugs used or potentially used in the affected areas. This study investigated the in vitro drug sensitivity of L. martiniquensis and L. orientalis, along with two reference species causing VL, namely L. donovani and L. infantum, against six antileishmanial drugs. Using a parasite-rescue and transformation assay, the results demonstrated that the IC50 values of amphotericin B (AmB), miltefosine (MIL), and sodium stibogluconate (Sb(III)) against all Leishmania species tested were within the sensitive range of each drug. On the contrary, the IC50 values of artemisinin (ART) and dihydroartemisinin (DHA), drugs primarily used for malaria treatment, were outside the sensitive range of the Leishmania species tested except L. infantum. This in vitro study highlights that AmB could effectively exhibit good sensitivity against the intracellular amastigotes of L. martiniquensis and L. orientalis. Also, MIL and Sb(III) could be considered alternative drugs for antileishmanial treatment in Thailand.

The germline genetic component of drug sensitivity in cancer cell lines

Patients with seemingly the same tumour can respond very differently to treatment. There are strong, well-established effects of somatic mutations on drug efficacy, but there is at-most anecdotal evidence of a germline component to drug response. Here, we report a systematic survey of how inherited germline variants affect drug susceptibility in cancer cell lines. We develop a joint analysis approach that leverages both germline and somatic variants, before applying it to screening data from 993 cell lines and 265 drugs. Surprisingly, we find that the germline contribution to variation in drug susceptibility can be as large or larger than effects due to somatic mutations. Several of the associations identified have a direct relationship to the drug target. Finally, using 17-AAG response as an example, we show how germline effects in combination with transcriptomic data can be leveraged for improved patient stratification and to identify new markers for drug sensitivity.

Extensive variation in drug-resistance mutational profile of Brazilian patients failing antiretroviral therapy in five large Brazilian cities

BackgroundDevelopment of drug-resistance mutations is the main cause of failure in antiretroviral therapy. In Brazil, there is scarce information on resistance pattern for patients failing antiretroviral therapy. ObjectivesTo define the HIV mutational profile associated with drug resistance in Brazilian patients from 5 large cities, after first, second or further failures to antiretroviral therapy. MethodsWe reviewed genotyping results of 1520 patients failing therapy in five Brazilian cities. Frequency of mutations, mean number of active drugs, viral susceptibility to each antiretrovirals drug, and regional differences were assessed. ResultsMean time of antiretrovirals use was 22.7±41.1 months. Mean pre-genotyping viral load was 4.2±0.8log (2.1±2.0 after switching antiretrovirals). Mean number of remaining active drugs was 9.4, 9.0, and 7.9 after 1st, 2nd, and 3rd failure, respectively. We detected regional variations in drug susceptibility: while BA and RS showed the highest (∼40%) resistance level to ATV/r, FPV/r and LPV/r, in the remaining cities it was around half of this rate. We detected 90% efavirenz/nevirapine resistance in SP, only 45% in RS, and levels between 25% and 30% in the other cities. Regarding NRTI, we found a similar pattern, with RJ presenting the highest, and CE the lowest susceptibility rates for all NRTI. Zidovudine resistance was detected in only 3% of patients in RJ, against 45–65% in the other cities. RJ and RS showed 3% resistance to tenofovir, while in CE it reached 55%. DRV/r (89–97%) and etravirine (61–85%) were the most active drugs, but again, with a wide variation across cities. ConclusionsThe resistance mutational profile of Brazilian patients failing antiretroviral therapy is quite variable, depending on the city where patients were tested. This variation likely reflects distinctive choice of antiretrovirals drugs to initiate therapy, adherence to specific drugs, or circulating HIV-1 strains. Overall, etravirine and DRV/r remain as the most active drugs.

Lack of correlation between the promastigote back-transformation assay and miltefosine treatment outcome.

Widespread antimony resistance in the Indian subcontinent has enforced a therapy shift in visceral leishmaniasis treatment primarily towards miltefosine and secondarily also towards paromomycin. In vitro selection of miltefosine resistance in Leishmania donovani turned out to be quite challenging. Although no increase in IC50 was detected in the standard intracellular amastigote susceptibility assay, promastigote back-transformation remained positive at high miltefosine concentrations, suggesting a more 'resistant' phenotype. This observation was explored in a large set of Nepalese clinical isolates from miltefosine cure and relapse patients to assess its predictive value for patient treatment outcome. The predictive value of the promastigote back-transformation for treatment outcome of a set of Nepalese L. donovani field isolates (n = 17) derived from miltefosine cure and relapse patients was compared with the standard susceptibility assays on promastigotes and intracellular amastigotes. In-depth phenotypic analysis of the clinical isolates revealed no correlation between the different susceptibility assays, nor any clear link to the actual treatment outcome. In addition, the clinical isolates proved to be phenotypically heterogeneous, as reflected by the large variation in drug susceptibility among the established clones. This in vitro laboratory study shows that miltefosine treatment outcome is not necessarily exclusively linked with the susceptibility profile of pre-treatment isolates, as determined in standard susceptibility assays. The true nature of miltefosine treatment failures still remains ill defined.

Variation in growth and drug susceptibility amongGiardia duodenalisassemblages A, B and E in axenicin vitroculture and in the gerbil model

This study investigated the molecular and biological variation among different Giardia duodenalis assemblages. In vitro growth and susceptibility to albendazole, fenbendazole, flubendazole, metronidazole, tinidazole and furazolidone was studied for laboratory (AI: WB, AII: G1 and B: GS/M-83-H7) and 6 field isolates of assemblage subtype AI, AII, B and EIII. Additionally, isolates of the 3 assemblages were evaluated in the gerbil upon 3-day oral treatment with albendazole (6 mg/kg), flubendazole (5 mg/kg) and metronidazole (20 mg/kg). Assemblage AI grew significantly faster than all other assemblage subtypes, which showed comparable generation times. The assemblage A laboratory strains displayed altered in vitro drug susceptibilities compared to their matching AI or AII field isolate. No variation in drug susceptibility was observed between field isolates of assemblages A and E. However, assemblage A laboratory strains were more susceptible to the benzimidazoles and less susceptible to the nitro-imidazoles and furazolidone than the assemblage B laboratory strain. In the gerbil, no markedly different drug susceptibilities were observed. In conclusion, the Giardia assemblage subtype can be associated with differences in growth characteristics rather than in drug susceptibility.

Natural variation in drug susceptibility to HCV polymerase inhibitors in treatment-naïve HCV patient isolates

Summary. To assess the natural variation in drug susceptibility among treatment-naïve hepatitis C virus (HCV) patient isolates, the susceptibilities of chimeric replicons carrying the HCV NS5B polymerase from up to 51 patient isolates against a panel of diverse HCV nonnucleoside polymerase inhibitors were evaluated using a replicon-based transient replication assay. Some patient to patient variation in susceptibility to the panel of three HCV nonnucleoside polymerase inhibitors was observed. Linear regression and correlation analyses revealed no correlations among the susceptibilities to the polymerase inhibitors tested. Our results suggest that variable antiviral responses to HCV nonnucleoside polymerase inhibitors may be observed because of the natural variation in baseline susceptibility. In addition, the lack of correlation among the susceptibilities to three classes of HCV polymerase inhibitors evaluated here supports their possible combined use in a combination therapy strategy.

HIV Genetic Diversity and Drug Resistance

Most of the current knowledge on antiretroviral (ARV) drug development and resistance is based on the study of subtype B of HIV-1, which only accounts for 10% of the worldwide HIV infections. Cumulative evidence has emerged that different HIV types, groups and subtypes harbor distinct biological properties, including the response and susceptibility to ARV. Recent laboratory and clinical data highlighting such disparities are summarized in this review. Variations in drug susceptibility, in the emergence and selection of specific drug resistance mutations, in viral replicative capacity and in the dynamics of resistance acquisition under ARV selective pressure are discussed. Clinical responses to ARV therapy and associated confounding factors are also analyzed in the context of infections by distinct HIV genetic variants.

A genome-wide approach to identify genetic variants that contribute to etoposide-induced cytotoxicity

Large interindividual variance has been observed in sensitivity to drugs. To comprehensively decipher the genetic contribution to these variations in drug susceptibility, we present a genome-wide model using human lymphoblastoid cell lines from the International HapMap consortium, of which extensive genotypic information is available, to identify genetic variants that contribute to chemotherapeutic agent-induced cytotoxicity. Our model integrated genotype, gene expression, and sensitivity of HapMap cell lines to drugs. Cell lines derived from 30 trios of European descent (Center d'Etude du Polymorphisme Humain population) and 30 trios of African descent (Yoruban population) were used. Cell growth inhibition at increasing concentrations of etoposide for 72 h was determined by using alamarBlue assay. Gene expression on 176 HapMap cell lines (87 Center d'Etude du Polymorphisme Humain population and 89 Yoruban population) was determined by using the Affymetrix GeneChip Human Exon 1.0ST Array. We evaluated associations between genotype and cytotoxicity, genotype and gene expression and correlated gene expression of the identified candidates with cytotoxicity. The analysis identified 63 genetic variants that contribute to etoposide-induced toxicity through their effect on gene expression. These include genes that may play a role in cancer (AGPAT2, IL1B, and WNT5B) and genes not yet known to be associated with sensitivity to etoposide. This unbiased method can be used to elucidate genetic variants contributing to a wide range of cellular phenotypes induced by chemotherapeutic agents.

Variability and variation in drug susceptibility among Giardia duodenalis isolates and clones exposed to 5-nitroimidazoles and benzimidazoles in vitro

We analysed, in a cell-by-cell study, the in vitro susceptibility of Giardia duodenalis strains, including Mexican isolates and their clones to 5-nitroimidazoles and benzimidazoles. Fluorogenic dye staining (FDA-PI) and cell morphology (CM) assays, two fast and direct techniques, replaced the indirect 'gold standard' method (subculture in liquid medium) in the evaluation of 5-nitroimidazoles and benzimidazoles, respectively. Under these conditions, the activity of several 5-nitroimidazole and benzimidazole derivatives was consistent with their known efficacy, but parasite stocks exhibited a greater variability in response to 5-nitroimidazoles compared with benzimidazoles. Also, consecutive progenies from single stocks maintained in continuous subculture in drug-free media displayed changes (variations) in the proportions of drug resistant (R/T) subpopulations when exposed to sublethal concentrations of 5-nitroimidazoles and benzimidazoles. These were again more variable upon exposure to 5-nitroimidazoles than to benzimidazoles. Variations were not due to drug susceptibility shifts in parent trophozoites since analysis of cytokinetic processes showed a predominant pattern of susceptible/susceptible or resistant/resistant daughters, whereas susceptible/resistant daughters were scarce. Our observations support the idea that G. duodenalis cultures exhibit variations in their response to 5-nitroimidazoles and benzimidazoles as a result of a drug-independent competition between drug-susceptible and drug-resistant subpopulations when parasites are subcultured.

Natural variation of drug susceptibility in wild-type human immunodeficiency virus type 1.

Wild-type viruses from the ViroLogic phenotype-genotype database were evaluated to determine the upper confidence limit of the drug susceptibility distributions, or "biological cutoffs," for the PhenoSense HIV phenotypic drug susceptibility assay. Definition of the natural variation in drug susceptibility in wild-type human immunodeficiency virus (HIV) type 1 isolates is necessary to determine the prevalence of innate drug resistance and to assess the capability of the PhenoSense assay to reliably measure subtle reductions in drug susceptibility. The biological cutoffs for each drug, defined by the 99th percentile of the fold change in the 50% inhibitory concentration distributions or the mean fold change plus 2 standard deviations, were lower than those previously reported for other phenotypic assays and lower than the clinically relevant cutoffs previously defined for the PhenoSense assay. The 99th percentile fold change values ranged from 1.2 (tenofovir) to 1.8 (zidovudine) for nucleoside reverse transcriptase RT inhibitors (RTIs), from 3.0 (efavirenz) to 6.2 (delavirdine) for nonnucleoside RTIs, and from 1.6 (lopinavir) to 3.6 (nelfinavir) for protease inhibitors. To evaluate the potential role of intrinsic assay variability in the observed variations in the drug susceptibilities of wild-type isolates, 10 reference viruses with different drug susceptibility patterns were tested 8 to 30 times each. The median coefficients of variation in fold change for the reference viruses ranged from 12 to 18% for all drugs except zidovudine (32%), strongly suggesting that the observed differences in wild-type virus susceptibility to the different drugs is related to intrinsic virus variability rather than assay variability. The low biological cutoffs and assay variability suggest that the PhenoSense HIV assay may assist in defining clinically relevant susceptibility cutoffs for resistance to antiretroviral drugs.

Hospital-reported pneumococcal susceptibility to penicillin.

Geographic variation in drug susceptibility among isolates of Streptococcus pneumoniae has influenced national treatment guidelines for community-acquired pneumonia. Whether individual hospital susceptibility data provide reliable and valid information for providers is unclear. We examined the geographic and temporal variability in hospital-reported rates of pneumococcal susceptibility. We surveyed all 52 hospitals that provided acute adult care in the five counties surrounding Philadelphia and collected data on levels of penicillin susceptibility among all pneumococcal blood isolates from 1998 to 2000. In 1998, pneumococcal nonsusceptibility to penicillin varied from 0% to 67% of all blood isolates across the 33 hospitals with >10 isolates in that year. Hospital location did not correlate with the level of reported pneumococcal susceptibility (p = 0.8). In addition, correlations were not significant in reported pneumococcal susceptibility to penicillin within individual hospitals during the 3 years.

Clonal diversity in a single isolate of the malaria parasite Plasmodium falciparum

Clones of an isolate of Plasmodium falciparum from Mae Sod (Thailand) were prepared by a dilution procedure. Some of the parasite cultures thus obtained have been typed for the following characters: (i) electrophoretic variants of three enzymes; (ii) susceptibility to chloroquine and pyrimethamine; (iii) antigen diversities recognized by ten strain-specific monoclonal antibodies; (iv) presence or absence of knobs on infected erythrocytes and (v) two-dimensional PAGE variants of seven proteins. Amongst the clones there was variation involving each of these five characters. At least seven different types of clones were found in ten cultures produced by dilution. The amount of phenotypic variation within a single isolate has thus been shown to be surprisingly great. Variations in drug susceptibility and antigens are considered to be particularly important in view of their relevance to anti-malarial treatments.