Three out of 10 advanced colorectal tumors had mutations leading to premature termination of the SFRP1 translation product.  The mutations were two single-base deletions (26delG and 67delG) and a single-base change (G450A), which generates an in-frame stop codon.  These three mutations were found within the first exon, which was shown previously to be sufficient for Wnt antagonist activity by itself [26, 32].  Of the 10 tumors analyzed, no truncating mutations were found in the second or third exons of SFRP1.
An additional 51 tumors were analyzed via direct sequence analysis, yielding 49 clearly interpretable results.  Only the first exon was sequenced for stop codon mutations, but none were found.  This indicates that point mutation is not a frequent method of inactivation of the SFRP1 gene in colorectal cancer.