It is evident (Figure 2(a)) that the preincubation of the CD3+CD4+CD25+ lymphocytes with the specific antibodies against Tag7 or the preincubation of the K562 cells with the anti-Hsp70 antibodies blocked the cytotoxic activity, suggesting that the binding of the lymphocytic Tag7 with the Hsp70 on the tumor cell surface is necessary for its subsequent killing through the FasL-Fas interaction. This evidence concerns the gene FAS and neoplasm.