Discovery of the transforming activity with human TNF-α in BALB/3T3 cells encouraged us to move on to an experiment with the skin of TNF-α-deficient (TNF−/−) mice (Marino et al. 1997): Treatment with DMBA plus okadaic acid showed no tumors for up to 19 weeks in TNF−/− mice, whereas the percentage of tumor-bearing TNF+/+ mice was 100%. Here, TNF is linked to neoplasm.