RT PCR analysis of peripheral blood mononuclear cells (PBMCs) or solid tissue samples taken from colon cancer patients demonstrated that the pattern of HERV-K expression was different in human cells, in which malignant cells in the studied patients contained profuse amount of HERV-K Env transcripts class II (this class has lower homology of 71% with HERV-K 10), whereas low and non-malignant cells were diagnosed in a small quantity of both HERV-K Env class I (this class has higher homology of 96% with HERV-K 10) and class II [88]. This evidence concerns the gene ERVW-1 and malignant colon neoplasm.