title: The expression and prognostic significance of retinoic acid metabolising enzymes in colorectal cancer.
abstract: Colorectal cancer is one of the most common types of cancer with over fifty percent of patients presenting at an advanced stage. Retinoic acid is a metabolite of vitamin A and is essential for normal cell growth and aberrant retinoic acid metabolism is implicated in tumourigenesis. This study has profiled the expression of retinoic acid metabolising enzymes using a well characterised colorectal cancer tissue microarray containing 650 primary colorectal cancers, 285 lymph node metastasis and 50 normal colonic mucosal samples. Immunohistochemistry was performed on the tissue microarray using monoclonal antibodies which we have developed to the retinoic acid metabolising enzymes CYP26A1, CYP26B1, CYP26C1 and lecithin retinol acyl transferase (LRAT) using a semi-quantitative scoring scheme to assess expression. Moderate or strong expression of CYP26A1was observed in 32.5% of cancers compared to 10% of normal colonic epithelium samples (p<0.001). CYP26B1 was moderately or strongly expressed in 25.2% of tumours and was significantly less expressed in normal colonic epithelium (p<0.001). CYP26C1 was not expressed in any sample. LRAT also showed significantly increased expression in primary colorectal cancers compared with normal colonic epithelium (p<0.001). Strong CYP26B1 expression was significantly associated with poor prognosis (HR = 1.239, 95%CI = 1.104-1.390, χ(2) = 15.063, p = 0.002). Strong LRAT was also associated with poorer outcome (HR = 1.321, 95%CI = 1.034-1.688, χ(2) = 5.039, p = 0.025). In mismatch repair proficient tumours strong CYP26B1 (HR = 1.330, 95%CI = 1.173-1.509, χ(2)= 21.493, p<0.001) and strong LRAT (HR = 1.464, 95%CI = 1.110-1.930, χ(2) = 7.425, p = 0.006) were also associated with poorer prognosis. This study has shown that the retinoic acid metabolising enzymes CYP26A1, CYP26B1 and LRAT are significantly overexpressed in colorectal cancer and that CYP26B1 and LRAT are significantly associated with prognosis both in the total cohort and in those tumours which are mismatch repair proficient. CYP26B1 was independently prognostic in a multivariate model both in the whole patient cohort (HR = 1.177, 95%CI = 1.020-1.216, p = 0.026) and in mismatch repair proficient tumours (HR = 1.255, 95%CI = 1.073-1.467, p = 0.004).
authors.affiliation: Pathology, Division of Applied Medicine, School of Medicine and Dentistry, University of Aberdeen, Aberdeen, United Kingdom.
authors.forename: Gordon T
authors.initials: GT
authors.lastname: Brown
authors.affiliation: Vertebrate Antibodies, Zoology Building, Tillydrone Avenue, Aberdeen, United Kingdom.
authors.forename: Beatriz Gimenez
authors.initials: BG
authors.lastname: Cash
authors.affiliation: George S. Wise Faculty of Life Sciences, Department of Zoology, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Daniela
authors.initials: D
authors.lastname: Blihoghe
authors.affiliation: The Scottish Fish Immunology Research Centre, School of Biological Sciences, University of Aberdeen, Aberdeen, United Kingdom.
authors.forename: Petronella
authors.initials: P
authors.lastname: Johansson
authors.affiliation: Vertebrate Antibodies, Zoology Building, Tillydrone Avenue, Aberdeen, United Kingdom.
authors.forename: Ayham
authors.initials: A
authors.lastname: Alnabulsi
authors.affiliation: Pathology, Division of Applied Medicine, School of Medicine and Dentistry, University of Aberdeen, Aberdeen, United Kingdom.
authors.forename: Graeme I
authors.initials: GI
authors.lastname: Murray
mesh_terms: D002460:Cell Line; D015179:Colorectal Neoplasms / Q000201:enzymology* / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D000072500:Cytochrome P450 Family 26; D006801:Humans; D007150:Immunohistochemistry; D000072516:Retinoic Acid 4-Hydroxylase; D046888:Tissue Array Analysis; D014212:Tretinoin / Q000378:metabolism*
chemical_list: D014212:Tretinoin; D003577:Cytochrome P-450 Enzyme System; C000607079:CYP26B1 protein, human; C482075:CYP26C1 protein, human; D000072500:Cytochrome P450 Family 26; D000072516:Retinoic Acid 4-Hydroxylase