Cytochromes P450 and ABC-transporters mRNA expression in canine mast cell and mammary tumours

Introduction. Cytochromes P450 (CYPs) and ABC-transporters (ABCTs) are involved in anticancer drugs and carcinogens biotransformation and multidrug resistance phenomena, respectively. Limited information are actually available about CYPs and ABCTs expression in canine tumours. The aim of this study was to measure mRNA levels of foremost CYPs and ABCTs in canine mast cell and mammary tumours. Materials and Methods. Biopsies of 70 mast cell tumours (MCTs, 32 G1 and 38 G2+G3) and 33 mammary tumours (MTs, 12 benign and 21 malignant) were collected during surgery. Quantitative Real Time RT-PCR assays for canine CYP1A1, 1A2, 1B1, 2A13, 2A25, 2B11, 2C21, 2D15, 2E1, 3A12, MDR1, MRP1, -3, -5, -6, -7 as well as two internal control genes (ICGs) were set up and validated. Differences between benign and malignant tumours in target gene expression profiles in term of relative quantification were evaluated by using the arithmetic mean of selected ICGs and the 2-∆∆Ct method (Livak et al., 2001). Results. Among the whole set of candidate genes, CYP2A13, 2A25, 2B11 (only in MTs), 2E1 and MRP6 mRNAs were never detected in MCTs and MTs. Most of undifferentiated MCTs showed highest amounts of MRP7 mRNA compared to differentiated ones (p<0.05). In contrast, CYP1B1 and BCRP were significantly inhibited in malignant versus benign MTs (p<0.05). Conclusions. Cytochromes P450 mostly involved in anticancer drugs metabolism were shown to be expressed in MCTs and MTs and independently from tumour malignancy. The absence of CYP2B11 mRNA in MTs would confirm the potential usefulness of the gene pro-drug therapy approach envisaged in humans (i.e., for cyclophosphamide: Chen et al., 2007). Likewise to humans, CYP1B1 mRNA amount was higher in pre-neoplastic than malignant MTs (Yang et al., 2008). Finally, ABCTs gene expression profiles might be important, in perspective, to detect multidrug resistance phenomena. References Livak and Schmittgen (2001). Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method. Methods 25, 402-408. Chen CS, Jounaidi Y, Su T, Waxman DJ (2007). Enhancement of intratumoral cyclophosphamide pharmacokinetics and antitumor activity in a P450 2B11-based cancer gene therapy model. Cancer Gene Therapy 14, 935-944. Yang X, Solomon S, Fraser LR, Trombino AF, Liu D, Sonenshein GE, Hestermann EV, Sherr DH (2008). Constitutive regulation of CYP1B1 by the aryl hydrocarbon receptor (AhR) in pre-malignant and malignant mammary tissue. Journal of Cell Biochemistry 104, 402-417. Acknowledgements. Project supported by RC IZSVE 09/06.