Abstract:
The literature suggests that CD44 has the potential to be used as a non-invasive
tumour specific marker for early detection and monitoring. The gene transcript can
undergo alternative splicing, leading to the production of a number of isoforms and it
has been noted that in neoplastic states this splicing becomes abberant, leading to the
production of a number o f variant isoforms. The aim of this study was to analyse
CD44 variant expression with the goal o f reaching a platform from which a non-
invasive assay for routine clinical use could be produced.
In this study, the analysis o f exon junction splicing in bladder cancer has also led to
the finding of a tumour specific junction expressed in 64% o f tumours studied. This
exon junction (5/11) was found to be the same as that expressed in colorectal cancer.
Though mRNA based assays would provide a satisfactory method for exon junction
identification, a protein based approach would provide the platform for a more robust
assay.
Translation of gene expression data led to the design of a short synthetic peptide
which overlapped the 5/11 junction, and this was used to produce a novel polyclonal
antibody for this transitional epitope. The resulting polyclonal antibody was affinity
purified and used in a pilot study of 5/11 expression in bladder and colorectal
tumours.
In bladder tumours the antibody demonstrated an overall specificity o f 76.5% and an
overal sensitivity of 73.1 %, comparable to current commercially available early
detection assays. In a Dukes staged colorectal cancer study, no link between stage
and grade was noted, but the antibody gave an overall specificity of 76%.
Though further analysis is required, it is thought the 5/11 antibody may prove to be a
useful tool in the development o f a sensitive and specific assay for the non-invasive
detection of bladder and colorectal cancer.
