In studies that developed human tumors in nude mice, a pro-oncogenic effect was found: in a wide preclinical study of 20 human tumor models established in nude mice under continuous exposure to GH, no evidence for tumor growth stimulation was found in any of the tumors studied [42], and no effect was found when the proliferation of human gastric carcinoma cells was studied in vivo or in vitro [43,44]. This evidence concerns the gene GH1 and neoplasm.