Yes, Ras is one of the most important oncogenes in human cancer. Mutations in one of the three Ras genes are found in roughly 19% of all cancer patients, which translates to about 3.4 million new cases worldwide each year. When a Ras gene picks up certain mutations, the protein it produces gets stuck in a permanently active state, sending nonstop growth signals that drive cells to multiply out of control.
How the Ras Protein Normally Works
Ras proteins act as molecular switches inside your cells. In their normal state, they flip between “on” and “off” to relay growth signals from the cell surface to the interior. When a growth factor binds to a receptor on the outside of a cell, Ras switches on by grabbing a molecule called GTP. Once its job is done, Ras shuts itself off by breaking down that GTP into GDP, helped along by partner proteins called GAPs.
This cycling happens quickly and is tightly controlled. The on state lasts just long enough to pass the signal forward, telling the cell to grow or divide when appropriate. Two flexible regions on the Ras protein, called switch I and switch II, physically change shape depending on whether Ras is holding GTP or GDP. That shape change determines which downstream partners Ras can interact with.
What Goes Wrong in Cancer
In cancer, a single point mutation in a Ras gene can jam the switch in the “on” position. The mutant protein either loses its ability to break down GTP or becomes resistant to the GAP proteins that would normally help shut it off. The result is a Ras protein that continuously signals the cell to grow and divide, regardless of whether the cell has received any external instruction to do so.
Nearly all cancer-driving Ras mutations cluster in just three spots on the gene: codons 12, 13, and 61. Five specific mutations at these locations account for 70% of all Ras-mutant cancers. These mutations are called “gain of function” because they don’t simply break the protein. They give it a new, harmful capability: permanent activation.
Two Key Signaling Pathways Ras Hijacks
Once stuck in the on position, mutant Ras floods two major signaling highways inside the cell. The first is the MAPK pathway, which tells cells to multiply. The second is the PI3K/Akt pathway, which blocks the cell’s built-in self-destruct program (apoptosis). Together, these two pathways create a dangerous combination: cells that divide too fast and refuse to die when they should.
The PI3K/Akt arm is particularly important for survival signaling. Activated Akt interferes with several molecules that would normally trigger cell death, effectively making the cancer cell resistant to signals that should eliminate it. This dual action, promoting growth while suppressing death, is a big part of why Ras mutations are so effective at driving cancer.
Three Ras Genes, Different Cancer Types
Humans have three Ras genes: KRAS, NRAS, and HRAS. Each tends to be mutated in different cancers, and they are not equally common.
- KRAS is by far the most frequently mutated. It dominates in pancreatic cancer, colorectal cancer, lung cancer, and gynecologic cancers. In non-small cell lung cancer, one particular mutation (called G12C) is especially prevalent. That same mutation shows up in about 10% of colorectal cancers and 1% of pancreatic cancers.
- NRAS mutations appear more often in melanoma, thyroid cancer, and blood cancers like certain leukemias.
- HRAS is the least commonly mutated of the three across all tumor types.
There are also racial differences in mutation patterns. Research from Johns Hopkins found that Black individuals with colorectal cancer had a higher frequency of certain KRAS codon 12 mutations (6.5% higher) and codon 13 mutations (4.4% higher) compared to other racial groups, a finding that could eventually influence how screening and treatment are approached.
Where the Name “Ras” Comes From
The name stands for “rat sarcoma.” In 1964, researcher Jenny Harvey in London discovered a virus that caused sarcomas (connective tissue tumors) in rats when injected at high doses. Three years later, Werner Kirsten and colleagues in Chicago isolated a related but distinct virus with the same tumor-causing ability. Both viruses turned out to carry mutant versions of normal rat genes, and those genes were eventually found in human cells too. The human versions became known as HRAS (Harvey) and KRAS (Kirsten), and they were among the first oncogenes ever identified.
How Doctors Test for Ras Mutations
Ras mutation testing is now routine in several cancer types, particularly colorectal and lung cancers, because the results directly influence which treatments will work. The most common method is PCR (polymerase chain reaction), which amplifies small stretches of DNA from a tumor biopsy to check for known mutations at the key hotspots. Several commercial PCR kits exist, including systems from Roche, Qiagen, and Biocartis, each designed to detect a panel of common Ras mutations from preserved tissue samples.
A newer approach is next-generation sequencing (NGS), which reads large stretches of DNA in parallel and can catch a broader range of mutations than PCR. While PCR checks only for pre-specified mutations, NGS can reveal unexpected ones. Both methods start with DNA extracted from formalin-fixed tissue, the standard way tumor samples are preserved after biopsy or surgery.
Targeted Treatments and Resistance
For decades, Ras was considered “undruggable” because the protein’s smooth surface offered no obvious pocket where a drug could latch on. That changed with a new class of drugs targeting one specific mutation: KRAS G12C. The first of these, sotorasib (brand name Lumakras), works by locking the mutant protein in its inactive GDP-bound state, essentially forcing the stuck switch back to “off.”
In January 2025, the FDA approved sotorasib in combination with another drug, panitumumab, for adults with KRAS G12C-mutated metastatic colorectal cancer who had already been through standard chemotherapy. The approval came alongside a companion diagnostic test to identify eligible patients.
The challenge is that cancers often find workarounds. Tumors treated with KRAS G12C inhibitors can develop resistance through several routes. Some cancer cells reactivate the same growth-signaling pathway by ramping up activity from surface receptors like EGFR or HER2, bypassing the blocked Ras protein entirely. Others increase production of the non-mutated Ras proteins (NRAS or HRAS) to compensate. Still others undergo a physical transformation called epithelial-to-mesenchymal transition, becoming more invasive and activating alternative survival pathways. These resistance mechanisms are a major reason why combination therapies, hitting multiple targets at once, are a focus of current treatment strategies.
Drugs targeting KRAS G12C represent only the first crack in the problem. Other common Ras mutations, like G12D (the single most frequent across all cancers), are being pursued with different drug designs, but none have yet reached broad clinical use. For cancers driven by NRAS or HRAS mutations, direct inhibitors remain largely unavailable, and treatment still relies on targeting the downstream pathways that Ras activates.