Two models have been described where overexpression of KRAS, a member of the Ras family, coding for the K-Ras protein that is part of the RAS/MAPK pathway (shown in Figure 1) in the oral epithelium resulted in the growth of premalignant oral papillomas [75] or dysplasia and squamous cell carcinoma [76]. Here, KRAS is linked to squamous cell carcinoma.