F. TOXICITY RESULTING FROM DYSREPAIR 3) Carcinogenesis ; a) Failure of DNA Repair: Mutation, the Initiating Event in Carcinogenesis 1 Transient increases in the production or activity of __ are required for regulated growth, as during embryogenesis, tissue regeneration, and stimulation of cells by growth factors or hormones. 2 In contrast, permanent activation and/or overexpression of these favors __