ACTA1 and neoplasm: First, marker overlap (α-SMA, FAP, PDGFRα/β, and vimentin) means that stromal antigens may be co-expressed by tumor cells; depletion strategies risk on-target, pro-tumor shifts if protective stromal elements are removed, while payload strategies (e.g., antibody–drug conjugates) can be advantageous if the expression is tumor-dominant.