text: The primary translation product of SFRP1 contains an atypical signaling sequence, where a chain of 15 hydrophilic amino acids precede the hydrophobic domain.  Looking at 7 tumors without the truncating mutation, the retained SFRP1 allele contained an in-frame three-base insertion after nucleotide 37.  This is thought to lead to an extra alanine in the protein after codon 13.  However, no significant association was found between the development of colorectal cancer and the presence of the 3-bp insertion.