Overview
KRAS (Kirsten rat sarcoma virus) is a proto-oncogene located on chromosome 12p12.1 that encodes the K-Ras protein, a small GTPase involved in the RAS/MAPK signaling pathway. This pathway plays a critical role in transmitting signals from outside the cell to the nucleus and regulates essential cellular processes such as proliferation, differentiation, and survival.
KRAS mutations are commonly identified in colorectal carcinomas and colorectal adenomas, representing an early molecular event in the adenoma–carcinoma sequence. The KRAS variant is also found in a significant proportion of breast and ovarian cancer patients, making it more prevalent than pathogenic BRCA variants.
Symptoms
KRAS gene mutations do not produce direct clinical symptoms; instead, manifestations arise from the cancers associated with these mutations. Tumors harboring KRAS mutations tend to show aggressive behavior, rapid progression, and poor response to certain targeted therapies. Clinical features depend on the organ involved and may reflect advanced disease, treatment resistance, or recurrence rather than the mutation itself.
Causes
KRAS mutations result in structural changes in the K-Ras protein that cause it to remain permanently active in a GTP-bound state. This “stuck in the ON position” signaling leads to continuous cell growth and survival signals, even in the absence of external growth factors. As a consequence, cells undergo uncontrolled proliferation, a hallmark of cancer development. It plays a central role in oncogenesis by driving abnormal signaling pathways that promote tumor initiation and progression.
Risk Factors
KRAS mutations are among the most frequently activated oncogenic alterations and are present in approximately 30 percent of human cancers. They are commonly associated with colorectal cancer, pancreatic ductal adenocarcinoma, and non-small cell lung cancer. KRAS mutations are also seen in certain hereditary and developmental conditions such as Noonan syndrome and cardio-facio-cutaneous syndrome, as well as in leukemia and mucinous adenomas. The presence of a KRAS mutation is associated with resistance to EGFR inhibitor therapy and generally indicates a more aggressive disease course and poorer prognosis.
Prevention
There are no established preventive strategies to avoid KRAS gene mutations. Prevention focuses on early detection, accurate molecular testing, and appropriate therapeutic decision-making. KRAS mutation analysis is performed using formalin-fixed paraffin-embedded tissue samples as the gold standard, as well as liquid biopsy approaches using circulating tumor DNA from blood.
Molecular techniques such as PCR-based assays, next-generation sequencing, and confirmatory sequencing are used to detect KRAS mutations. Immunohistochemistry may provide supportive information, but it does not replace molecular testing. Identification of KRAS mutation status is essential for guiding personalized treatment strategies, predicting response to targeted therapies, and selecting patients who may benefit from newer KRAS G12C–specific inhibitors.
