1. Overview of NRAS
- Gene Name: NRAS (Neuroblastoma RAS viral oncogene homolog)
- Protein Type: Small GTPase
- Normal Function:
- Part of the RAS family (KRAS, HRAS, NRAS)
- Regulates cell proliferation, differentiation, and survival via downstream signaling pathways (MAPK, PI3K-AKT)
- Acts as a molecular switch: GTP-bound active → GDP-bound inactive
2. NRAS Mutations
- Hotspot codons: 12, 13, 61
- Effect of mutation:
- Constitutive activation → NRAS permanently “on”
- Continuous signaling through MAPK and PI3K pathways → uncontrolled proliferation and survival
3. Tumors Associated with NRAS Mutations
| Tumor Type | Frequency / Notes |
|---|---|
| Melanoma | 15–20% of cutaneous melanomas; mutually exclusive with BRAF V600 mutations |
| Acute myeloid leukemia (AML) | 10–15% of cases; often associated with intermediate risk |
| Multiple myeloma | ~15–20%; can contribute to progression |
| Thyroid carcinoma | Rare; more often follicular variant |
| Other solid tumors | Rare (colorectal, lung) |
4. Clinical Implications
- Prognosis:
- Predictive:
- NRAS-mutant tumors are generally resistant to BRAF inhibitors if BRAF wild-type
- MEK inhibitors may have modest activity in NRAS-mutant melanoma (e.g., binimetinib)
5. Therapeutic Considerations
| Strategy | Notes |
|---|---|
| MEK inhibitors | Some activity in NRAS-mutant melanoma |
| Immunotherapy | ICIs (PD-1, CTLA-4) effective in melanoma regardless of NRAS status |
| Targeted therapy | Direct NRAS inhibitors are largely experimental; research ongoing |
Key Mechanism: NRAS mutation → constitutive MAPK (RAS-RAF-MEK-ERK) signaling → proliferation and survival
6. Key Points
- NRAS is a driver oncogene via MAPK and PI3K-AKT pathways.
- NRAS mutations are common in melanoma and some hematologic malignancies.
- Direct targeting is difficult → therapy focuses on downstream inhibition (MEK) and immunotherapy.
Synonyms
NRAS