Drug Response In Patients Research Articles

Reliability of tumor primary cultures as a model for drug response prediction: expression profiles comparison of tissues versus primary cultures from colorectal cancer patients

Since primary tumor cells from patients have been used as a model for assessment of drug response for individual patients, this study aims to evaluate the reliability of such a model in colorectal cancer (CRC) in predicting the response of tumor tissues through comparison of their expression profiles. Establishment of primary cultures from tissues obtained surgically from CRC patients allowed us to study the gene expression differences between normal and tumor tissues as well as primary cultures derived from the tumor mass. The tissues comparison highlights the molecular characteristics of tumors, while the comparison between primary tumor cells versus normal and tumor tissues allowed us to identify alterations associated with the establishment of culture. Genes-drug association analyses allowed us to fine-tune our expectations while using primary culture as a model for drug assessment. Comparison between tumor cultures and original tissues through functional analyses showed the deregulations caused by culture establishment. Investigating the impact of such changes in genes-drug associations to identify the potential alterations in drug response, we found that primary cultures may have increased susceptibility toward paclitaxel, but reduced susceptibility toward analogues of fluorouracil compared with original tumors. Response of primary tumor cells toward different drugs is not linearly associated to tumor tissues. Our results highlight the importance to account for the discrepancy in responses between the primary tumor cells and original counterparts in order to provide clinicians with important insights to improve selection of drugs for individual patients based on in vitro assays.

Pharmacogenomics and metastatic colorectal cancer: Current knowledge and perspectives

The pharmacogenomics field is crucial for optimizing the selection of which chemotherapy regimen to use according to the patient's genomic profile. Indeed, the individual's inherited genome accounts for a large proportion of the variation in his or her response to chemotherapeutic agents both in terms of efficiency and toxicity. Patients with metastatic disease are more likely to receive different lines of chemotherapy with variable efficacy and experience some related complications. It is therefore critical to tailor the best therapeutic arsenal to improve the efficacy and avoid as much as possible related complications that are susceptible to interrupt the treatment. The pharmacogenomics approach investigates for each drug the implicated metabolic pathway and the potential personal variations in gene function. The aim of this review is to present a clear overview of the most accurate polymorphisms that have been identified as related to drug response in patients with mCRC.

Prediction of a Side Effect and Efficacy of Adjuvant Chemotherapy with Gemcitabine for Post Operative Patient of Pancreatic Cancer by a Genetic Polymorphism Analysis

Single nucleotide polymorphism (SNP) of the genes for ATP-binding cassette transporters is related to the side effects of anticancer drugs and that of drug metabolism-related enzyme genes is involved in the activation of gemcitabine (GEM). Forty eight patients treated with adjuvant GEM chemotherapy after pancreatic cancer resection was examined for the SNP of multidrug-resistance 1 (MDR1) 2677, MDR1 3435, breast cancer resistance protein (BCRP) 421, ribonucleotide reductase M1 (RRM1)(-)524, RRM1(-)37 and deoxycytidine deaminase (CDA) 208. We divided the patients according to normal group: patients homozygous for a wild-type allele or heterozygous for a mutant allele and mutant group: those homozygous for a mutant allele. Both groups were compared regarding the outcome and the occurrence and severity of side effects. MDR1 2677, MDR1 3435, BCRP421, RRM1(-) 524, RRM1(-) 37 and CDA mutant groups comprised 37.5, 31.3, 0, 12.5, 4.2 and 4.2%, respectively. The occurrence of >G3 side effects was the most frequent in the MDR1 2677 mutant group at 39%. The disease-free survival and overall survival tended to be longer in the MDR1 2677 mutant group. A correlation between the SNP of MDR1 2677 and drug response in patients receiving GEM chemotherapy.

Abstract PL03-01: Discovery of candidate biomarkers of anticancer drug sensitivity by high-throughput cell line screening.

Abstract PL03-01: Discovery of candidate biomarkers of anticancer drug sensitivity by high-throughput cell line screening.

Impact of ABCC2 genotype on antiepileptic drug response in Caucasian patients with childhood epilepsy

Antiepileptic treatment response has been suggested to be modulated by genetic polymorphisms of drug efflux transporters, in particular ABCB1. Recently, we found a significant association of ABCC2 -24C>T with nonresponse, primarily in the context of generalized epilepsy. Moreover, ABCC2 1249G>A was reported to alter transmembranal carbamazepine transport. Therefore, we aimed to confirm the association of ABCC2 variants with pharmacotherapy-resistance in Caucasians mainly affected by partial epilepsy. A total of 208 patients (114 male; age: 11.3±5.9 years) were genotyped for three putatively functionally relevant polymorphisms of ABCC2 (-24C>T, 1249G>A, 3972C>T). Genotype and haplotype frequencies were compared between responders and nonresponders to first-line antiepileptic treatment. Carriers of the ABCC2 1249G>A variant (417V>I) were more frequent among responders [odds ratio (OR)=2.68 (1.25-5.78); P=0.010]. This association remained significant after adjusting for age, sex and seizure type, [OR=2.88 (1.23-6.73); P=0.015]. The impact of 1249G>A was more pronounced among 64 patients receiving carbamazepine or oxcarbazepine (P=0.005), but nonsignificant in patients receiving other anticonvulsants. ABCC2 -24C>T and 3972C>T showed lack of association to therapy response. Haplotype analyses revealed that haplotype H2 containing solely the 1249A variant allele was more frequent in the responder group [OR=2.98 (1.38-6.44); P=0.004]. These data argue for a greater probability of antiepileptic drug response among carriers of the ABCC2 1249A variant that is associated with reduced carbamazepine transport. Although we could not confirm an impact of ABCC2 -24C>T, these results suggest that ABCC2 genotype may also modulate the response to anticonvulsants besides the extensively studied ABCB1 (P-glycoprotein).

Response to dexamethasone is glucose-sensitive in multiple myeloma cell lines

BackgroundHyperglycemia is among the major side effects of dexamethasone (DEX). Glucose or glucocorticoid (GC) regulates the expression of thioredoxin-interacting protein (TXNIP) that controls the production of reactive oxygen species (ROS) through the modulation of thioredoxin (TRX) activity.MethodsMultiple myeloma (MM) cells were grown in 5 or 20 mM/L glucose with or without 25 μM DEX. Semiquantitative reverse transcription-PCR (RT-PCR) was used to assess TXNIP RNA expression in response to glucose and DEX. ROS were detected by 5-6-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (CM-H2DCFDA). TRX activity was assayed by the insulin disulfide-reducing assay. Proliferation was evaluated using CellTiter96 reagent with 490-nm absorbtion and used to calculate the DEX IC50 in 20 mM/L glucose using the Chou's dose effect equation.ResultsTXNIP RNA level responded to glucose or DEX with the same order of magnitude ARH77 > NCIH929 > U266B1 in these cells. MC/CAR cells were resistant to the regulation. ROS level increased concurrently with reduced TRX activity. Surprisingly glucose increased TRX activity in MC/CAR cells keeping ROS level low. DEX and glucose were lacking the expected additive effect on TXNIP RNA regulation when used concurrently in sensitive cells. ROS level was significantly lower when DEX was used in conditions of hyperglycemia in ARH77/NCIH9292 cells but not in U266B1 cells. Dex-IC50 increased 10-fold when the dose response effect of DEX was evaluated with glucose in ARH && and MC/Car cellsConclusionsOur study shows for the first time that glucose or DEX regulates important components of ROS production through TXNIP modulation or direct interference with TRX activity in MM cells. We show that glucose modulates the activity of DEX through ROS regualtion in MM cells. A better understanding of these pathways may help in improving the efficacy and reducing the toxicity of DEX, a drug still highly used in the treatment of MM. Our study also set the ground to study the relevance of the metabolic milieu in affecting drug response and toxicity in diabetic versus non-diabetic patients with MM.

Association of the variants in AGT gene with modified drug response in Korean aspirin-intolerant asthma patients

The angiotensinogen ( AGT) gene enhances the effect of several bronchoconstrictors and produces a peptide that is accumulated in the airways of asthma patients; events that may underpin the pathogenesis of aspirin-intolerant asthma (AIA). To carry out a case-control analysis between AGT and aspirin-induced bronchospasm following treatment with an anti-asthma drug, montelukast (MLK), 38 single nucleotide polymorphisms (SNPs) in AGT were genotyped in 56 AIA cohort. Genotyping was performed with TaqMan assay and haplotypes were inferred using PHASE algorithm ver. 2.0. Statistical analyses of each SNPs and haplotypes were performed using SAS version 9.1. Among 13 variants displaying significant signals, two SNPs ( +2401C>G and +2476C>T) in the intronic region of AGT were significantly associated with modification of drug response even after correction for multiple testing ( P = 0.0009–0.002; P corr = 0.02–0.03). Furthermore, the two variants also exhibited associations with MLK response rate ( P = 0.0003–0.0006; P corr = 0.006–0.01). Although our results are preliminary and further replication in a larger-scale group of subjects should be warranted, these observations provide evidence that AGT variants might be one of genetic factors involved in the response of anti-asthma drugs in AIA patients.

A functional polymorphism in the SCN1A gene does not influence antiepileptic drug responsiveness in Italian patients with focal epilepsy

A splice site variation (c.603-91G>A or rs3812718) in the SCN1A gene has been claimed to influence efficacy and dose requirements of carbamazepine and phenytoin. We investigated the relationship between c.603-91G>A polymorphism and response to antiepileptic drugs (AEDs) in 482 patients with drug-resistant and 401 patients with drug-responsive focal epilepsy. Most commonly used AEDs were carbamazepine and oxcarbazepine. The distribution of c.603-91G>A genotypes was similar among drug-resistant and drug-responsive subjects, both in the entire population and in the groups treated with carbamazepine or oxcarbazepine. There was no association between the c.603-91G>A genotype and dosages of carbamazepine or oxcarbazepine. These findings rule out a major role of the SCN1A polymorphism as a determinant of AED response.

Clinical Predictors of Drug Response in Patients with Obsessive-Compulsive Disorder

ObjectiveThe aim of this study was to evaluate which clinical variables might influence the antiobsessional responses to proserotonergic drugs in a sample of patients with obsessive-compulsive disorder (OCD).MethodsTwo hundred forty-nine patients with DSM-IV OCD under-gone mean 13-month treatments with selective serotonin reuptake inhibitors. According to the treatment response, defined as a reductions of the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) total score ≥35%, patients were divided into two groups.ResultsOne hundred fourteen patients responded to the treatment and the other one hundred thirty five patients did not. Responders had a significant long duration of medication in YUMC OCD clinic, short total duration of past treatment in other institutes, and higher frequency of drug naïve cases and lower baseline Y-BOCS scores.ConclusionThe pre-treatment factors including total duration of past treatment, drug naïve or not, baseline OCD symptoms and the factor of duration of the treatment may influence drug treatment response in OCD patients.

Abstract 2232: Effectiveness evaluation of an in vitro nucleic acid amplification test for quantification of BCR-ABL fusion transcript variants in human whole blood

Abstract Quantitative measurement of BCR-ABL fusion gene transcripts in whole blood by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) is a clinically validated method to monitor tyrosine kinase inhibitor drug response in patients diagnosed with chronic myelogenous leukemia (CML). Monitoring of BCR-ABL expression in blood of cML patients under treatment with a tyrosine kinase inhibitor of BCR-ABL is considered standard of care. A three log or greater reduction in BCR-ABL expression from baseline is considered a Maximum Molecular Response (MMR). A subsequent 0.5 log increase in BCR-ABL from MMR is considered a sign of treatment failure sufficient to trigger change in treatment. The challenge is to develop a test with sufficient analytical performance characteristics and quality control to reliably measure BCRABL in MMR samples in which there may be less than 10 molecules in 300 of RNA extracted from whole blood. A method validation protocol was developed using the International Committee on Harmonization (ICH) Q2(R1) international validation guidelines. BCRABL variants b2a2 and b3a2 as well as the housekeeping gene GUSB were measured in KCL22 cell line RNA and Stratagene Universal Human Reference RNA test articles in extreme linear dilution assay, robustness testing conditions, and in multiple laboratories. Quality controls were developed to enable loading as much whole blood RNA into the assay as possible without assay interference. These included a reverse transcription (RT) standardization mixture comprising External RNA Control Consortium (ERCC) reagents to control for RT interference, and controls for genomic DNA contamination, RNA integrity, and PCR interference. Results: This test for b2a2 and b3a2 variants of BCR-ABL meets ICHQ2(R1) guidelines for specificity, linearity, accuracy, LOD and LOQ, imprecision, robustness, and reproducibility. Each analyte comprised by the test was linear (R2 > 0.97) over more than 3 logs10, and demonstrated inter-experimental and inter-laboratory imprecision low enough to enable measurement of a 3-fold difference as significant (P <0.05) from a value as low as five molecules/assay. Experiments are underway to quantify the amount of whole blood RNA that can be loaded into RT reaction without interference. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2232. doi:10.1158/1538-7445.AM2011-2232

The prognostic impact of O 6- methylguanine DNA methyltransferase and epidermal growth factor receptor expressions on primary gliosarcoma: A clinicopathologic and immunohistochemical study of seven cases at a single institution

Gliosarcoma is an uncommon variant of glioblastoma characterized by a biphasic tissue pattern of glial and mesenchymal differentiation. O6-methylguanine DNA methyltransferase (MGMT) is a DNA repair protein that removes mutagenic and cytotoxic adducts from O6-guanine in DNA. Lack of MGMT protein expression immunohistochemically is related to drug responses in patients of malignant glioma treated with alkylating agents. Epidermal growth factor receptor (EGFR) is the most frequently amplified gene in glioblastoma and associated with tumor invasiveness, angiogenesis, poor survival, and resistance to radiation therapy. To elucidate the relationship between the statuses of the MGMT as well as EGFR proteins and the prognosis. The study was undertaken on samples received at the Department of Pathology from 2003 to 2009. Clinicopathologic and immunohistochemical study of seven cases was performed. This series included three men and four women with a mean age of 49.3 years at first surgery. The median progression-free survival (PFS) was 22.2 months and 8.6 months for primary tumors with 0 to 1+ and 2+ to 3+ MGMT staining, respectively; the median overall survival (OS) was 27.5 months and 14.2 months for primary tumors with 0 to 1+ and 2+ to 3+ MGMT staining, respectively. The median PFS was 17.2 months and 11.2 months for primary tumors with 0 to 1+ and 2+ to 3+ EGFR staining, respectively; the median OS was 20.4 months and 17.7 months for primary tumors with 0 to 1+ and 2+ to 3+ EGFR staining, respectively. The series showed that MGMT and EGFR protein expressions were both unfavorable prognostic factors for patients with gliosarcoma.

Disease Characterization of Long QT Syndrome Using iPS Cell-Derived Cardiomyocytes

Long QT syndrome (LQTS) is well characterized inheritable, life threatening disease, and often related to large pedigrees of family history. The present study established induced pluripotent stem cell (iPSC) from the patients with LQTS, and investigated whether the LQTS patient-derived iPSCs can be utilized for disease characterization, and drug response. We reprogrammed patient somatic cells, differentiated cardiomyocytes and examined electrophysiological properties. Genotype analysis showed the heterozygote mutation in KCNQ1 gene, 1893delC, indicating that this patient was type 1 LQTS. Drug response examination using multi-electrode analysis (MEA) revealed the LQTS-iPSC-derived cardiomyocytes revealed IKs disturbance, but not IKr. Electrophysiological recording confirmed 1893delC has a dominant negative role in IKs channel function by trafficking defect. Isoproterenol induced ventricular tachycardia-like arrhythmia. This study provides the evidences that iPSCs can be utilized for characterization, drug response, and diagnosis for patients with LQTS to conduct medical therapies.

Magnetic Resonance Imaging Predictors of Treatment Response in First-Episode Schizophrenia

Identifying neurobiological predictors of response to antipsychotics in patients with schizophrenia is a critical goal of translational psychiatry. Few studies, however, have investigated the relationship between indices of brain structure and treatment response in the context of a controlled clinical trial. In this study, we sought to identify magnetic resonance (MR) imaging measures of the brain that predict treatment response in patients experiencing a first-episode of schizophrenia. Structural MR imaging scans were acquired in 39 patients experiencing a first-episode of schizophrenia with minimal or no prior exposure to antipsychotics participating in a double-blind 16-week clinical trial comparing the efficacy of risperidone vs olanzapine. Twenty-five patients were classified as responders by meeting operationally defined treatment response criteria on 2 consecutive study visits. Fourteen patients never responded to antipsychotic medication at any point during the clinical trial. MR imaging scans were also acquired in 45 age- and sex-matched healthy volunteers. Cortical pattern matching methods were used to compare cortical thickness and asymmetry measures among groups. Statistical mapping results, confirmed by permutation testing, indicated that responders had greater cortical thickness in occipital regions and greater frontal cortical asymmetry compared with nonresponders. Moreover, among responders, greater thickness in temporal regions was associated with less time to respond. Our findings are consistent with the hypothesis that plasticity and cortical thickness may be more preserved in responders and that MR imaging may assist in the prediction of antipsychotic drug response in patients experiencing a first-episode of schizophrenia.

Antiepileptic drug response in temporal lobe epilepsy

To investigate the relationship between brain MRI and clinical characteristics and patterns of antiepileptic drug (AED) response in patients with mesial temporal lobe epilepsy (MTLE). A total of 165 MTLE patients were divided into seizure-free with AED (AED responders, n = 50), pharmacoresistant (n = 87), and remitting-relapsing seizure control group (n = 28). All groups were evaluated regarding age, frequency of seizures, and age at epilepsy onset, duration of epilepsy, febrile seizures, presence and side of hippocampal atrophy (HA), and initial precipitating injuries. For gray matter (GM) MRI voxel-based morphometry (VBM) we selected only patients with unilateral HA on visual MRI analysis (n = 100). Comparisons were made between all groups and 75 healthy controls. Age at epilepsy onset was lower (p = 0.005) and initial frequency of seizures was higher in the pharmacoresistant compared with the other 2 groups (p = 0.018). All groups showed GM atrophy compared to controls in ipsilateral hippocampus, bilateral parahippocampal gyri, frontal, occipital, parietal, and cerebellar areas. In the AED responders group, such findings were more restricted to areas ipsilateral to the epileptic focus and more widespread in the pharmacoresistant and remitting-relapsing groups. VBM pairwise comparisons showed areas with GM volume reduction in the pharmacoresistant and remitting-relapsing groups compared with AED responders in bilateral periorbital frontal (p < 0.01), cingulum (p < 0.05), and temporal lobe contralateral to the epileptic focus (p < 0.05). Pharmacoresistant and remitting-relapsing groups presented a similar pattern of GM atrophy, which was more widespread compared with AED responders. Conversely, age at epilepsy onset was lower and initial seizure frequency was higher in pharmacoresistant patients.

Hepatic microRNA expression is associated with the response to interferon treatment of chronic hepatitis C

BackgroundHCV infection frequently induces chronic liver diseases. The current standard treatment for chronic hepatitis (CH) C combines pegylated interferon (IFN) and ribavirin, and is less than ideal due to undesirable effects. MicroRNAs (miRNAs) are endogenous small non-coding RNAs that control gene expression by degrading or suppressing the translation of target mRNAs. In this study we administered the standard combination treatment to CHC patients. We then examined their miRNA expression profiles in order to identify the miRNAs that were associated with each patient's drug response.Methods99 CHC patients with no anti-viral therapy history were enrolled. The expression level of 470 mature miRNAs found their biopsy specimen, obtained prior to the combination therapy, were quantified using microarray analysis. The miRNA expression pattern was classified based on the final virological response to the combination therapy. Monte Carlo Cross Validation (MCCV) was used to validate the outcome of the prediction based on the miRNA expression profile.ResultsWe found that the expression level of 9 miRNAs were significantly different in the sustained virological response (SVR) and non-responder (NR) groups. MCCV revealed an accuracy, sensitivity, and specificity of 70.5%, 76.5% and 63.3% in SVR and non-SVR and 70.0%, 67.5%, and 73.7% in relapse (R) and NR, respectively.ConclusionsThe hepatic miRNA expression pattern that exists in CHC patients before combination therapy is associated with their therapeutic outcome. This information can be utilized as a novel biomarker to predict drug response and can also be applied to developing novel anti-viral therapy for CHC patients.

Prediction of drug response using genomic signatures from the Cancer Cell Line Encyclopedia

Abstract Accurate prediction of patient drug response is required for successful personalized medicine. Cancer is a disease resulting from myriad genetic alterations. Accordingly, it should be possible to predict drug response of specific cancers using genetic and molecular signatures. To aid this effort, an ongoing collaboration established between Novartis and the Broad Institute called the Cancer Cell Line Encyclopedia (CCLE) has (i) comprehensively characterized genome-scale mRNA expression, copy number alteration and mutation profiles for nearly 1000 cancer cell line models spanning many tumor types and (ii) profiled ~500 of these cell lines against ~1000 anticancer compounds. Using these data, we are developing a scalable, extensible predictive modeling framework based on various supervised learning methods that include both categorical classification and linear regression approaches to predict compound sensitivity. By cross-validation of the generated models against test data sets, we quantitatively estimated model performance. Our initial results validate several preexisting genetic predictors of sensitivity. In addition, our models reported 70% or higher sensitivity and specificity for a number of compounds and yielded interesting potentially novel predictive features that, in some cases, outperform previously existing genetic predictors of sensitivity. Our integrative approach demonstrates that pharmacological profiling of large, genomically annotated cancer model systems, coupled with systematic predictive modeling, can uncover novel predictors of drug response and may ultimately aid patient stratification. This talk is also presented as Poster A4.

Association of the G-protein and α2-adrenergic receptor gene and plasma norepinephrine level with clonidine improvement of the effects of diuretics in patients with cirrhosis with refractory ascites: a randomised clinical trial

ObjectiveClonidine is an α2-adrenoceptor agonist which, by coupling with G-protein, has been proposed as an alternative treatment for refractory ascites of patients with cirrhosis for several years. Genetic polymorphisms of...

Approaches and limitations of phosphatidylinositol-3-kinase pathway activation status as a predictive biomarker in the clinical development of targeted therapy

The central role played by the class I(A) phosphatidylinositol-3-kinase (PI3K) signaling node in human cancer is highlighted in the multiple mechanisms by which these signals become dysregulated. Many studies suggest that constitutive PI3K activation in human cancer contributes to drug resistance, including targeted agents and standard cytotoxic therapy. The combination of activation mechanisms and the multiple downstream cascades that emanate from the PI3K node contributes to the difficulty in measuring PI3K activation as a biomarker. Although many agents suppress the pathway in models, the challenge remains to translate this biology into a patient selection strategy (i.e., identify patients with "PI3K activated" tumors) and subsequently link this biomarker definition to drug responses in patients. The various genetic and epigenetic lesions resulting in pathway activation necessitate combined approaches using genetic, genomic, and protein biomarkers to accurately characterize "PI3K activated" tumors. Such a combined approach to pathway status can be assessed using a statistical stratification of patients in a randomized trial into "pathway on" and "pathway off" subsets to compare the treatment effect in each arm. Instead of considering individual biomarkers for their predictive ability, this strategy proposes the use of a collection of biomarkers to identify a specific "pathway on" patient population predicted to have clinical benefit from a pathway inhibitor. Here, we review the current understanding of the mechanisms of PI3K activation in breast cancer and discuss a pathway-based approach using PI3K as a predictive biomarker in clinical development, which is currently in use in a global phase 3 setting.

Abstract B43: Comparative proteomic analysis of colorectal cell lines to identify biomarkers for the prediction of intrinsic resistance to FOLFOX chemotherapy

Abstract As there is a great interpatient variability in drug response caused by the individual geno- and phenotype the choice of optimal chemotherapy should be tailored for each patient. Intrinsic drug resistance is one of the main reasons for therapeutic ineffectiveness of first line therapy and recurrence in colorectal cancer. To advance individualized chemotherapy and understanding of drug resistance mechanisms, predictive biomarkers which indicate individual drug response of patients are urgently needed. The prediction of response to first line therapy will identify subgroups of patients who benefit from treatment and thus avoid ineffective treatment and associated side effects. In this study, several commercially available cell lines as well as primary epithelial mixed cultures and clonal cell lines established from colorectal cancer patients were treated with different drugs, such as 5-fluorouracil, oxaliplatin, and drug combinations, e.g., FOLFOX. The determination of chemosensitivity of these cell lines to drug treatment was performed using two different assays, the ATPlite™-(Perkin Elmer) and FMC-assay (according to Larsson et al.). Both assays showed time- and dose-dependent drug responses which differed significantly among the 18 colorectal cell cultures. The analysis of obtained in vitro chemosensitivity data allowed us to cluster sensitive versus resistant cell lines by determining IC50-values. For the discovery of differentially expressed proteins which might be linked to a specific phenotypes of intrinsic chemoresistance we generated protein expression patterns from all 18 cell lines using a combination of reversed phase highperformance liquid chromatography and matrix-assisted laser desorption/ionization mass spectrometry (RP-HPLC MALDI MS). Up to 3500 m/z ion signals in the molecular mass range between 2500-35000 m/z were detected reflecting a complex pattern of small proteins and peptides. For protein identification, RP-HPLC fractionated samples were purified and digested by trypsin. Fragments of interest were subjected to MS/MS analysis in the TOF/TOF mode. The corresponding MS/MS spectra were used to search the NCBInr database using MASCOT software. Based on these data, we hope to gain more understanding of the biological processes of chemoresistance concerning important cellular drug responses (e.g., signal transduction pathways) and thereby obtain insight into new drug targets for future therapeutic intervention. Citation Information: Clin Cancer Res 2010;16(14 Suppl):B43.

Effect of ABCB1 C3435T polymorphism on docetaxel pharmacokinetics according to menopausal status in breast cancer patients

Background:It can be hypothesised that inherited polymorphisms in the drug-transporter ABCB1 gene may interfere with interindividual variations in drug response in breast cancer patients. Docetaxel is a substrate for ABCB1 whose function has been shown to be modulated by oestrogen and progesterone.Methods:Whether ABCB1 polymorphisms including T-129C, A61G, C1236T, G2677T/A and C3435T polymorphisms could account for variations in the disposition of docetaxel and whether menopausal status at the time of diagnosis might interact with this effect were analysed in women receiving neoadjuvant chemotherapy for breast cancer (n=86).Results:A highly significant association was observed, but restricted to premenopausal women (n=53), between the pharmacokinetics of docetaxel and C3435T polymorphism, as patients with CC genotype had lower mean values of the area under the plasma concentration-time curve (AUC) of docetaxel than patients with CT and TT genotypes (P<0.0001). Comparison between pre- and postmenopausal women with the same C3435T genotype yielded a significant difference in docetaxel AUC only for CC genotype (P<0.0001).Conclusion:These results suggest that C3435T polymorphism genotyping and menopausal status at the time of diagnosis might be useful when considering chemotherapy regimens including docetaxel in breast cancer patients.