Functionally, VB12 is bound to haptocorrin and transcobalamin in blood, the former being encoded by TCN1 and the latter by TCN2.29 A recent study has revealed that TCN1 is highly expressed in most colon cancer tissues both at transcription and translation levels, whose upregulation is associated with tumorigenesis and progress. This evidence concerns the gene TCN2 and colonic neoplasm.