B2M and neoplasm: Analysis of tumors from ApcMin/+/Ptpn13fl/fl/Vil-CreERT2 (APV) mice showed that Ptpn13 knockout, induced by TAM treatment, significantly upregulated the expression of IRF1, LMP2, TAP1, TAP2, H2-D1, H2-K1, and B2M and also increased the surface levels of MHC-I complex on tumor cells (Fig. 4f, g).