Tumor-specific expression of the novel cytochrome P450 enzyme, CYP2W1

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Abstract

A novel human cytochrome P450, CYP2W1, was cloned and expressed heterologously. No or very low CYP2W1 mRNA levels were detected in fetal and adult human tissues, expression was however seen in 54% of human tumor samples investigated (n = 37), in particular colon and adrenal tumors. Western blotting also revealed high expression of CYP2W1 in some human colon tumors. In rat tissues, CYP2W1 mRNA was expressed preferentially in fetal but also in adult colon. The CYP2W1 gene was shown to encompass one functional CpG island in the exon 1–intron 1 region which was methylated in cell lines lacking CYP2W1 expression, but unmethylated in cells expressing CYP2W1. Re-expression of CYP2W1 was seen following demethylation by 5-Aza-2′-deoxycytidine. Transfection of HEK293 cells with CYP2W1 caused the formation of a properly folded enzyme, which was catalytically active with arachidonic acid as a substrate. It is concluded that CYP2W1 represents a tumor-specific P450 isoform with potential importance as a drug target in cancer therapy.

Section snippets

Materials and methods

Bioinformatics. The BLASTN and TBLASTN algorithms [13] were used to search the dbEST [14] and the Celera sequence databases (http://www.celera.com) for sequences related to previously described CYP2 sequences.

Cell culture conditions and preparation of total cell extracts. The human hepatoma cell line HepG2, human embryonic kidney HEK293 cells, the human cervix adenocarcinoma cell line HeLa (ATCC, Manassas, VA), and the human hepatoma cell line B16A2 (a kind gift from Drs. Laurent Corcos and

Bioinformatics

In the dbEST database, a cDNA sequence (GenBank Accession No. AK000366) containing a part of CYP2W1 was found, and in the Celera sequence database genomic clones related to this sequence were identified and aligned in order to obtain the CYP2W1 gene sequence. The CYP2W1 gene was more than 5.5 kb long, located on chromosome 7p22.3, and showed the typical family 2 gene structure with nine exons. The open-reading frame was 1473 nucleotide long and encoded a 490 amino acid long polypeptide. The

Discussion

Using Northern blotting, mRNA dot blot, and MTC panels no significant CYP2W1 expression was seen in any untransformed human adult or fetal tissue but high mRNA expression was observed in several tumor samples, in particular, the majority of colon samples. The relative CYP2W1 expression at the protein and mRNA levels did not coincide in all different tumor samples, probably indicating differences in quality of the specimens obtained, variable contribution by untransformed tissue in the

Acknowledgments

We are grateful to Prof. Bertil Hamberger at the Department of Molecular Medicine and Surgery, Karolinska Hospital, Stockholm, Sweden, for providing human tumor samples. This work was supported by grants from The Swedish Research Council and by The Swedish Cancer Foundation.

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