STING1 and cancer: Deletion of STING in SKBR3 cells (Supplementary Fig. 12a) nearly abrogated the Fc-mutant HER2 ADC cancer cell killing activity in all three single-cell clones of the STING KO SKBR3 cells in PBMC co-cultures, while minimally impacting the Fc-wt HER2 ADC activity (Fig. 3f).