We stably co-expressed NrasV12 and c-MYC oncogenes in the livers of different mouse strains (e.g., CBA/CaJNarl, C57BL/6Jnarl, and C3H/HeNCrNarl strains) with the same approach and observed a dramatic divergence in both tumor latency and tumor burdens among these mouse strains. The gene discussed is MYC; the disease is neoplasm.