Alkylation and Carbamylation Effects of Lomustine and Its Major Metabolites and MGMT Expression in Canine Cells

Abstract

DNA Alkylation is thought to be the reason for the efficacy of lomustine while carbamylation has been implicated as the cause for the side effects seen with lomustine treatment such as hepatotoxicity. In the alkylation study we show that lomustine and its metabolites form similar levels of the DNA adducts N7 hydroxyethylguanine and O6 hydroxyethyldeoxyguanosine. In terms of carbamylation, lomustine showed greater extent of carbamylation in the canine hepatocytes and lymphoma cell lines. The DNA repair enzyme O6 methylguanine DNA methyltransferase (MGMT) causes resistance of tumor cells to bifunctional nitrosourea, like lomustine. There is no data available regarding MGMT expression/activity in canine cells or tissues. Our study shows that there is low MGMT activity in the canine lymphoid cell line 17–71 while the GL-1 cells did not show any detectable enzyme activity or mRNA expression. The MGMT enzyme activity measured in canine hepatocytes is about 250–350 fmol/mg protein as compared to about 90 fmol/mg protein in 17–71 cells. We also show that MGMT mRNA expression in 17–71 cells and canine hepatocytes positively correlates with its enzyme activity in these cells.

Automatic Generation of 3D-Printed Reactionware for Chemical Synthesis Digitization using ChemSCAD

“…To demonstrate the function of the ChemSCAD process, we designed monolithic reactionware cartridges for the batch synthesis of Ribavirin, an antiviral medication used to treat respiratory syncytial virus (RSV) infection, hepatitis C, and some viral hemorrhagic fevers; 17 Modafinil, a narcolepsy drug; 18 and Lomustine, an alkylating nitrosourea compound widely used in chemotherapy. 19 Lomustine was also synthesized in flow. Furthermore, we demonstrate the effective synthesis of these compounds in the designed cartridges as shown in Figure 3 .…”

Temozolomide is additive with cytotoxic effect of irradiation in canine glioma cell lines

“…MGMT mRNA expression was measured in G06A, SDT‐3 and J3T‐BG; the latter two cell lines showed high MGMT mRNA expression level (Chakkath et al., 2015 ). Canine lymphoma cells and canine hepatocytes were tested for MGMT mRNA and enzyme activity, and a positive correlation between MGMT mRNA expression and enzyme activity was found (Chakkath et al., 2015 ).…”

“…MGMT mRNA expression was measured in G06A, SDT‐3 and J3T‐BG; the latter two cell lines showed high MGMT mRNA expression level (Chakkath et al., 2015 ). Canine lymphoma cells and canine hepatocytes were tested for MGMT mRNA and enzyme activity, and a positive correlation between MGMT mRNA expression and enzyme activity was found (Chakkath et al., 2015 ). In our analysis of MGMT promoter methylation in three canine cell lines, we detected very high methylation levels (with exception to one location), interestingly, the methylation of enhancer and Exon 1 has shown higher variability between cell lines.…”

Continuous Flow Synthesis of Anticancer Drugs

“…The main cytotoxic effect of these species results from their ability to form an adduct via the oxygen atom of guanine causing DNA cross-linking. This adduct interferes with key cellular processes such as DNA replication leading to cell death via apoptosis [45,46].…”