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25-hydroxyvitamin D3 24-hydroxylase (CYP24A1), the catabolizing enzyme of the active vitamin D3, is often overexpressed in solid tumors. The unbalanced high levels of CYP24A1 seem to be a determinant of vitamin D resistance in tumors. Splice variants of CYP450 enzymes are common. Existence of CYP24A1 isoforms has been reported recently. We have investigated the presence of CYP24A1 splicing variants (SV) in human colon cancer cell lines and tissue samples. Using a set of primer combination we have screened the entire coding sequence of CYP24A1 and identified three splice variants in colon cancer cell lines. The presence of these SVs in human colon tissue samples showed a correlation with histological type of the tissue and gender of patients. The sequencing of the alternatively spliced fragments showed that two have lost the mitochondrial target domain, while the third lacks the heme-binding domain. All SVs retained their sterol binding domain. Translation of these variants would lead to a dysfunctional enzyme without catalytic activity that still binds its substrates therefore they might compete for substrate with the synthesizing and catabolizing enzymes of vitamin D., (Copyright (c) 2010 Elsevier Ltd. All rights reserved.)

Background: A cross-sectional study was performed on a cohort of colorectal cancer (CRC) patients to reveal any influence of age, gender, and subsite on grades of malignancy., Patients and Methods: Data from histopathological grading according to WHO criteria were pooled into groups of low-grade (well and moderately differentiated) and high-grade (poorly and undifferentiated) cancer and analyzed for associations., Results: In general, women with CRC were significantly older than men (p<0.05). In particular, women with high-grade cancer in the proximal and distal colon had a median age of 75 years and were thus 10-15 years older (p<0.01 and p<0.05, respectively) than their male counterparts. In contrast, high-grade rectal cancer developed in both genders around the early age of 60 years., Conclusion: Women are protected from more aggressive cancer in the colon though not in the rectum until well after menopause. This likely reflects the differential sensitivity of the mucosa at these sites against the anticancer effects triggered by activation of estrogen receptor-beta.

There is a growing body of evidence that disturbed circadian clock gene expression is associated with tumor development and tumor progression. Based on our initial experiments demonstrating decreased period 1 (Per1) expression in colon cancer, we evaluated clock gene and estrogen receptor (ER) alpha/beta expression in colon cancer cells of primary colorectal tumors and adjacent normal colon mucosa (NM) by real-time RT-PCR. Analysis of gene expression in G(2) and G(3) colorectal tumors revealed a decrease of Per1 mRNA compared with paired NM (G(2): 0.52-fold; P = n.s. and G(3): 0.48-fold; P = 0.03). A significant gender specific difference of Per1 expression was observed in G(2) tumors as compared with NM (female: 0.38-fold; P = 0.004 vs. male: 0.73-fold; P = n.s.). Expression of CLOCK was significantly elevated in G(2) tumors of male patients (1.63-fold, P = 0.01). The expression of ER-beta was significantly decreased in G(2) and G(3) tumors (G(2): 0.32-fold; P = 0.003 and 0.27; P = 0.001). No significant gender specific differences of ER-beta reduction in tumors were observed. A significant correlation between the decrease of Per1 and ER-beta in colorectal tumors (r = 0.61; P < 0.001) was found. No changes in gene expression were detected for ER-alpha and Per2. Our data demonstrate a correlated decrease of Per1 and ER-beta in colorectal tumors, mediated probably by epigenetic mechanisms. The observed gender differences in the expression of CLOCK and Per1 in G(2) tumors might suggest a gender-specific, distinctive role of the cellular clock in colorectal tumorigenesis.

Unimpaired vitamin D action has been implicated in human cancer prevention. We have previously demonstrated the effectiveness of 1 alpha-dihydroxyvitamin D3 (1,25-D3) to reduce proliferation and increase differentiation in human colon cancer cells. The aim of this study was to investigate, on the one hand, expression of the vitamin D receptor (VDR) and of 25-hydroxyvitamin D(3)-1 alpha-hydroxylase (1 alpha-hydroxylase) in human normal and malignant colonic tissue and, on the other hand, to determine consequences of reduced or lacking VDR action in a VDR knockout mouse model. In low-grade malignancies of the human colon we found increased VDR and 1 alpha-hydroxylase mRNA expression. However, in late-stage high-grade tumors the vitamin D system is severely compromised. In the mouse colon we found an inverse relationship between VDR levels and proliferation in colon descendens, a tissue known to be specifically affected by nutrients during carcinogenesis. Expression of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, was significantly augmented with complete loss of VDR. These data suggest that genomic 1,25-D(3) action is necessary to protect against nutrition-linked hyperproliferation and oxidative DNA damage.

Human colorectal cancer cells not only express the nuclear vitamin D receptor (VDR) but are also endowed with 25-hydroxy-vitamin D(3)-1alpha-hydroxylase activity and therefore are able to produce the specific ligand for the VDR, the hormonally active steroid 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)). In the present study we show by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) as well as by Western blotting and immunohistochemical methods, that in human large intestinal carcinomas expression of the genes encoding the 25-(OH)D(3)-1alpha-hydroxylase as well as the VDR increases in parallel with ongoing dedifferentiation in the early phase of cancerogenesis, whereas in poorly differentiated late stage carcinomas only low levels of the respective mRNAs can be detected. This indicates that, through up-regulation of this intrinsic 1alpha,25(OH)(2)D(3)/VDR system which mediates the anti-mitotic effects of the steroid hormone, colorectal cancer cells are apparently able to increase their potential for an autocrine counter-regulatory response to neoplastic cell growth, particularly in the early stages of malignancy.