However, while neither CT45A1 expression nor MLC2 phosphorylation was associated with the presence of a homotypic CIC structure (Fig. S9A,B and Fig. 6D), CT45A1 immunoreactivity‐positive cells in CIC structures were mainly the moon‐shaped outer cells (Fig. 6E, red arrows) in the CIC structure of MSI‐H CRC tumors (Fig. 6F). Here, CT45A1 is linked to colorectal carcinoma.