Why isn't an oncogenic mutation in KRAS enough to induce and sustain transformation?

KRAS, a key member of the RAS proto-oncogene family, encodes a small GTPase involved in regulating cell proliferation, differentiation, and survival through signaling cascades such as MAPK/ERK, PI3K/AKT/mTOR, RalGEF/RalA/B, JAK/STAT3, and NF-κB. Although KRAS mutations, especially at codons 12, 13, or 61, lead to its activation and contribute to uncontrolled growth, these changes alone are not enough to fully transform a normal cell. KRAS activation requires cooperation with other genetic or epigenetic events, such as inactivation of p53 or p16INK4a, tumor suppressor genes to overcome critical cellular barriers, for example, senescence and apoptosis. This need for cooperation reflects the complexity of the oncogenic process, requiring simultaneous deregulation of multiple signaling pathways for malignant transformation. Indeed, in experimental models, mutant KRAS expression in normal cells often induces oncogene-induced senescence rather than unlimited proliferation. These findings highlight that KRAS functions more as an initiator of tumorigenesis than as an autonomous driver. Thus, in depth understanding of the genetic context in which KRAS operates is essential for the development of effective and personalized therapeutic strategies.