As the transcriptional downregulation of SVOPL was observed in all CRC samples, SVOPL allelic switching may occur primarily as a result of downregulation of the most abundantly expressed allele, unlike DLX5 and GRB10. We therefore conclude that allelic switching of these genes is due to changes in transcriptional regulation that affect the individual alleles differently. The gene discussed is GRB10; the disease is colorectal carcinoma.