Alan Aitchison

University of Cambridge, Cambridge, England, United Kingdom

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Publications (4)27.07 Total impact

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    ABSTRACT: Transforming growth factor-beta (TGF-beta) is a potent growth inhibitor in a wide range of cell types. A transducer of TGF-beta signaling known as Mothers against decapentaplegic homologue 4 (Smad4) is a known tumor suppressor found on chromosome 18q21.1 and is typically inactivated by deletion or mutation in pancreatic and colorectal cancers. The purpose of the article is to investigate Smad4 expression, gene copy number and methylation status in advanced cases of prostate cancer. We have employed Methylation Specific PCR (MSP) to identify methylation sites within the Smad4 promoter and combined this with quantitative real-time PCR to look for correlates between methylation status and Smad4 expression and to examine androgen receptor (AR) expression. Bacterial artificial chromosome-comparative genomic hybridization (BAC-CGH) has been used to look for genomic amplifications and deletions which may also contribute to expression changes. We fail to find evidence of genomic deletions or amplifications affecting the Smad4 locus on chromosome 18 but show a correlation between promoter methylation and the loss of Smad4 expression in the same material. We confirm that the AR locus on the X chromosome is amplified in 30% of the advanced clinical samples and that this correlates with increased transcript levels as previously reported by other groups. This indicates that epigenetic changes affect the expression of the Smad4 protein in prostate cancer and points to methylation of the promoter as a novel marker of and contributor to the disease warranting further study.
    The Prostate 06/2008; 68(6):661-74. · 3.84 Impact Factor
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    ABSTRACT: The RASSF1A gene is a tumor suppressor gene inactivated by hypermethylation in a very wide variety of malignant tumors including prostate cancer. In this study we have used laser capture microdissection to provide pure cell populations to investigate the methylation status of 16 CpG sites in the promoter region of this gene in prostatic intra-epithelial neoplasia, in histologically normal epithelial cells associated with these lesions and in epithelial cells from benign prostatic hyperplasia. Unexpectedly, frequent methylation, detected by sequence analysis following bisulphite treatment, was observed in benign epithelium as well as in the lesions associated with prostatic intra-epithelial neoplasia and at high risk of cancer formation. Fifty percent or more CpG sites were methylated in 7/14 prostatic intra-epithelial neoplasms, 8/11 histologically normal epithelial cells and 8/12 specimens of benign prostatic tissue. These observations suggest that methylation of the RASSF1A gene is present in both pre-malignant and benign epithelia and suggests quantitation is required for it to be an effective marker of early prostate cancer.
    The Prostate 06/2007; 67(6):638-44. · 3.84 Impact Factor
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    ABSTRACT: Transforming growth factor beta (TGF-beta) is frequently involved in gastrointestinal carcinogenesis although its contribution to oesophageal adenocarcinoma (AC) and its precursor Barrett's oesophageal epithelium (BE) metaplasia are unclear. Expression of TGF-beta signalling components was assessed by reverse transcription-polymerase chain reaction (PCR), western blot, and immunohistochemistry in oesophageal endoscopic biopsies and cell lines. Genomic alterations in SMAD4 were characterised by fluorescence in situ hybridisation, methylation specific PCR, and sequencing. Functional integrity of TGF-beta signalling was assessed by characterisation of p21 and proliferation status. Smad4 negative BIC-1 cells were transiently transfected with smad4 and TGF-beta responsiveness evaluated. smad4 mRNA expression was progressively reduced in the metaplasia-dysplasia-adenocarcinoma sequence (p<0.01). A quarter of AC samples displayed an abnormal Smad4 protein isoform, with no corresponding changes in gene sequence or organisation. Methylation of smad4 has not been described previously but we found promoter methylation in 70% of primary AC samples. In 6/8 oesophageal cell lines, chromosomal rearrangements affected the smad4 locus. Lack of smad4 expression in BIC-1 cells occurred secondary to loss of one copy and extensive deletion of the second allele's promoter region. TGF-beta dependent induction of p21 and downregulation of minichromosome maintenance protein 2 was lost in >80% of BE and AC. TGF-beta failed to inhibit proliferation in 5/8 oesophageal cell lines. In BIC-1, the antiproliferative response was restored following transient transfection of smad4 cDNA. In BE carcinogenesis, downregulation of Smad4 occurs due to several different mechanisms, including methylation, deletion, and protein modification. Frequent alterations in TGF-beta signalling lead to a functionally significant impairment of TGF-beta mediated growth suppression.
    Gut 07/2006; 55(6):764-74. · 10.73 Impact Factor
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    ABSTRACT: The DUTT1 gene is located on human chromosome 3, band p12, within a region of nested homozygous deletions in breast and lung tumors. It is therefore a candidate tumor suppressor gene in humans and is the homologue (ROBO1) of the Drosophila axonal guidance receptor gene, Roundabout. We have shown previously that mice with a targeted homozygous deletion within the Dutt1/Robo1 gene generally die at birth due to incomplete lung development: survivors die within the first year of life with epithelial bronchial hyperplasia as a common feature. Because Dutt1/Robo1 heterozygous mice develop normally, we have determined their tumor susceptibility. Mice with a targeted deletion within one Dutt1/Robo1 allele spontaneously develop lymphomas and carcinomas in their second year of life with a 3-fold increase in incidence compared with controls: invasive lung adenocarcinomas are by far the predominant carcinoma. In addition to the mutant allele, loss of heterozygosity analysis indicates that these tumors retain the structurally normal allele but with substantial methylation of the gene's promoter. Substantial reduction of Dutt1/Robo1 protein expression in tumors is observed by Western blotting and immunohistochemistry. This suggests that Dutt1/Robo1 is a classic tumor suppressor gene requiring inactivation of both alleles to elicit tumorigenesis in these mice.
    Cancer Research 10/2004; 64(18):6432-7. · 8.65 Impact Factor