To understand the relationship between DCLK1 isoforms and Notch signaling, we isolated total RNA from the formalin-fixed paraffin-embedded (FFPE) sections of either control subjects or patients with UC or immune-related adverse events—colitis (IRAEC) and discovered distinct changes in the expression of DCLK1-L and DCLK1-S isoforms along with Notch1 and FoxD3, respectively. Here, NOTCH1 is linked to colitis.