B2M and breast carcinoma: CRISPR-mediated deletion of Usp22 in mouse prostate cancer RM1, colon cancer MC38, and breast cancer 4T1 cells resulted in a substantial elevation in the expression of both H-2Kb/d and β2M, 2 subunits of the MHC-I complex (Figure 1A and Supplemental Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/JCI193162DS1).