HRAS and breast cancer: For example, N-nitroso-N-methylurea (NMU) induces G > A transition in codon 12 of the rat HRAS gene resulting in the development of mammary tumours (NMU-induced rat mammary tumours) [42, 43] and dimethylbenzanthracene (DMBA)-induced A > T transition in codon 61 of mouse HRAS will result in the development of various skin tumours [44].