Instability of mRNA expression signatures of drug transporters in chronic myeloid leukemia patients resistant to imatinib.

Despite the success of imatinib mesylate (IM) in the treatment of chronic myeloid leukemia (CML), approximately 30% of patients are resistant to therapy, mostly due to unknown causes. To profile the expression signatures of drug transporters throughout IM therapy and correlate them with resistance, we quantified mRNA expression levels of the SLC22A12, ABCB1, ABCC1, ABCG2 and MVP genes in consecutive samples from peripheral blood or bone marrow of CML patients who were either responsive or resistant to IM. Additionally we identified and quantified BCR-ABL1 transcript variants and analyzed 1236T>C ABCB1 and 480G>C SLC22A1 polymorphisms.

Estragole: a weak direct-acting food-borne genotoxin and potential carcinogen.

We evaluated the genotoxicity of the food-flavouring agent estragole in V79 cells using the sister chromatid exchange (SCE) assay and the alkaline comet assay. Unexpectedly, we observed an increase in SCE without an exogenous biotransformation system (S9) and a decrease in its presence. Positive results were also observed in the alkaline comet assay without S9, indicating DNA strand breakage.

DNA damage response in imatinib resistant chronic myeloid leukemia K562 cells.

Resistance to imatinib in patients with chronic myeloid leukemia can lead to advanced disease and blast crisis. Conventional chemotherapy with DNA damaging agents is then used, alone or in combination with other tyrosine kinase inhibitors (TKIs). Our aim was to assess whether imatinib resistant K562 cells were also resistant to DNA damaging agents.

Genomics and cancer drug resistance.

Cellular drug resistance is a major obstacle in cancer therapy. Mechanisms of resistance can be associated with altered expression of ATP-binding cassette (ABC) family of transporters on cell membrane transporters, the most common cause of multi-drug resistance (MDR), but can also include alterations of DNA repair pathways, resistance to apoptosis and target modifications. Anti-cancer treatments may be divided into different categories based on their purpose and action: chemotherapeutic agents damage and kill dividing cells; hormonal treatments prevent cancer cells from receiving signals essential for their growth; targeted drugs are a relatively new cancer treatment that targets specific proteins and pathways that are limited primarily to cancer cells or that are much more prevalent in cancer cells; and antibodies function by either depriving the cancer cells of necessary signals or by causing their direct death.

Development of imatinib and dasatinib resistance: dynamics of expression of drug transporters ABCB1, ABCC1, ABCG2, MVP, and SLC22A1.

About 20% of patients with chronic myeloid leukemia (CML) do not respond to treatment with imatinib either initially or because of acquired resistance. To study the development of CML drug resistance, an in vitro experimental system comprising cell lines with different resistance levels was established by exposing K562 cells to increasing concentrations of imatinib and dasatinib anticancer agents. The mRNA levels of BCR- ABL1 and of genes involved in drug transport or redistribution (ABCB1, ABCC1, ABCC3, ABCG2, MVP, and SLC22A1) were measured and the ABL1 kinase domain sequenced.

Genotoxic and apoptotic activities of the food flavourings myristicin and eugenol in AA8 and XRCC1 deficient EM9 cells.

Some food flavourings, such as safrole and methyleugenol, are known for their genotoxic and hepatocarcinogenic properties whereas for others, such as myristicin, there is less data. Myristicin and eugenol are both alkenylbenzenes, and we compared their direct genotoxicity in repair proficient (AA8) and repair deficient XRCC(-) (EM9) Chinese hamster ovary cells. Cell viability was assessed by the MTT assay.

Naturally contaminated shellfish samples: quantification of diarrhetic shellfish poisoning toxins in unhydrolysed and hydrolysed extracts and cytotoxicity assessment.

Contamination of shellfish from the Portuguese coast with diarrhetic shellfish poisoning (DSP) toxins is a recurrent event, with most of the commercial bivalves contaminated with high percentages of esters of okadaic acid (OA) and dinophysistoxin-2 (DTX2). This report describes the quantification of DSP toxins in unhydrolysed and hydrolysed extracts of several cockle and mussel samples naturally contaminated and the evaluation of their cytotoxicity profiles in V79 cells. The quantification of the acyl esters in the shellfish samples involved the cleavage of the ester bond through alkaline hydrolysis and the release of the parent toxins OA and DTX2.

The stimulatory role of human cytochrome b5 in the bioactivation activities of human CYP1A2, 2A6 and 2E1: a new cell expression system to study cytochrome P450-mediated biotransformation (a corrigendum report on Duarte et al. (2005) Mutagenesis 20, 93-100).

This corrigendum report describes the study of the comparison of human cytochrome b(5) (b(5)) with rat b(5) when coupled with human cytochrome P450 CYP1A2, 2A6 or 2E1. Results indicate a role of the N-terminal part of b(5) in the coupling with CYP. Indeed, the plasmid pLCM-b(5)-RED used in our former study on b(5) [Duarte et al.

Genotoxicity and endoreduplication inducing activity of the food flavouring eugenol.

Eugenol (1-allyl-3-methoxy-4-hydroxybenzene; CAS No. 97-53-0), a compound extracted from clove oil and marjoram, is widely used as a food flavouring substance and is present in spices such as basil, cinnamon and nutmeg. It is also used in dentistry as an antiseptic and analgesic.

Escherichia coli BTC, a human cytochrome P450 competent tester strain with a high sensitivity towards alkylating agents: involvement of alkyltransferases in the repair of DNA damage induced by aromatic amines.

We report here on strain BTC, a new Escherichia coli mutagenicity tester strain for the expression of human cytochrome P450 (CYP) with an enhanced sensitivity for the detection of alkylating agents. This strain was developed first through knocking out of the genes ada and ogt in our previously developed strain BMX100, resulting in PD1000. Strain PD1000 demonstrated a significantly higher detection sensitivity towards several alkylating agents such as N-nitrosodiethylamine (NNdEA), N-nitrosodi-n-propylamine (NNdPA), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG).

The stimulatory role of human cytochrome b5 in the bioactivation activities of human CYP1A2, 2A6 and 2E1: a new cell expression system to study cytochrome P450 mediated biotransformation.

Cytochrome b(5) (b(5)) is increasingly recognized to be of importance for specific cytochrome P450 (CYP) activities. We developed human b(5)/CYP-competent mutagenicity tester bacteria to study the role of b(5) in the bioactivation activity of human CYP. These new tester bacteria were derived from the previously engineered human CYP-competent Escherichia coli K12 tester strain MTC, containing a bi-plasmid system for the co-expression of a specific CYP form (CYP1A2, 2A6 or 2E1) with human b(5), and human NADPH cytochrome P450 reductase (RED), resulting in the strain BTC-b(5)-1A2, BTC-b(5)-2A6 and BTC-b(5)-2E1, respectively.

Possible transient adaptive response to mitomycin C in peripheral lymphocytes from thyroid cancer patients after iodine-131 therapy.

Our study attempted to assess the possible induction and persistence of an adaptive response in lymphocytes of thyroidectomized thyroid cancer patients treated with 131I (2,590 MBq, corresponding to whole body doses in the range of 200-300 mGy), to a testing dose of mitomycin C (MMC) in vitro. The cytogenetic endpoint studied was the induction of micronuclei in cytokinesis-blocked peripheral blood lymphocytes, immediately before treatment and 1, 6 and 24 months after therapy. One month after therapy, induction of micronucleated cytokinesis-blocked lymphocytes ( per thousand ) by MMC was lower (34.