This is supported by the fact that human DNA (mutated K-Ras, RAB and Alu Yd6 sequences) were found only in the tumor of the rat injected with SW480 cells and by the lower frequency of tumor formation in the rats that were treated with DNAse I/proteases which strongly suggests that this treatment decreased the levels of SW480-derived DNA in the circulation of rat that in turn reduced or avoided “passive” transfection of such DNA into rat colon epithelial cells. The gene discussed is KRAS; the disease is neoplasm.