ITGAM and neoplasm: Flow cytometry of established tumors showed that PD-L1 is expressed on both MC38 tumor cells and tumor-infiltrating CD11b+ myeloid cells (Fig. 2E).Because PD-L1 knockout MC38 tumor-bearing mice failed to respond to the A12-VHHkappa conjugate therapy, expression of PD-L1 on tumor cells is required for therapeutic efficacy, supported by the imaging data (Fig. 4).