GTPases are not typically measured directly in routine clinical labs — instead, they’re evaluated indirectly through associated diseases, biomarkers, and molecular diagnostics.
Genetic/Mutational Testing The most common clinical approach: Mutations in GTPase genes are driver events in many diseases.
RAS mutations (KRAS, NRAS, HRAS) — tested in colorectal, lung, and pancreatic cancers to guide therapy (e.g., EGFR inhibitor eligibility)
BRAF V600E— downstream of RAS signaling; tested in melanoma, thyroid, colon cancer.
RAC1, RHO mutations— emerging in melanoma and lymphoma panels
Methods: next-generation sequencing (NGS), PCR-based assays, liquid biopsy (ctDNA)
Protein Expression (Immunohistochemistry / Western Blot)
Tumor biopsies stained for GTPase-related proteins (e.g., overexpressed RAS)
Activation state sometimes assessed in research/translational settings via pull-down assays on fresh tissue
Disease-Specific Biomarkers
Disease | Relevant GTPase | Clinical Test
Colorectal/lung cancer | KRAS/NRAS | Tumor mutation panel
Neurofibromatosis (NF1) | RAS (dysregulated) | NF1 gene sequencing
Noonan syndrome | RAS pathway | Germline panel
Charcot-Marie-Tooth | Dynamin-2 (DNM2) | Gene sequencing
Intellectual disability | RAB GTPases | Exome sequencing
Thyroid cancer | HRAS/NRAS | Somatic mutation testing
Functional/Pathway Surrogates
Since direct GTPase activity measurement isn’t practical on clinical samples, downstream pathway activation is used instead:
pERK, pAKT levels by IHC — surrogate for RAS/MAPK pathway activity Phosphoproteomic panels in research GTP-bound RAS ELISA kits
Liquid biopsy for KRAS mutations in circulating tumor DNA.
Companion diagnostics— KRAS G12C testing required before prescribing sotorasib (Lumakras)
Pharmacodynamic assaysin clinical trials measuring RAS pathway suppression
GTPase evaluation means mutational profiling, especially RAS family, rather than enzyme activity measurement.
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