CNR1 as a Radioligand Therapy Target
CNR1, cannabinoid receptor 1, is a cell-surface protein (GPCR). In Human Protein Atlas immunohistochemistry, CNR1 staining is highest in thyroid cancer (100% of samples positive), bladder cancer (58% of samples positive) and head and neck cancer (75% of samples positive). Published literature suggests CNR1 does not readily internalize, so radionuclide retention may rely on surface binding. Clinical status: Clinical-stage (up to phase 3, any modality).
Is CNR1 a good radioligand therapy target?
Scored against the six criteria that decide whether a protein can become a radioligand therapy:
- ✅ Cell-surface accessibility: Localized to the cell surface, so a radioligand can reach it from circulation.
- ✅ Tumor expression: High IHC staining in thyroid cancer, 100% of samples positive.
- ❌ Internalization: Reported not to internalize.
- ✅ Clinical precedent: Clinical-stage (up to phase 3, any modality)
- ❔ Shedding: Not yet assessed.
- ❔ Normal-tissue dosimetry: Check kidney, liver, bone marrow and salivary expression in the Human Protein Atlas tissue atlas.
CNR1 expression in cancer
Protein expression of CNR1 across 20 cancer types from Human Protein Atlas immunohistochemistry. The score is a weighted staining intensity from 0 to 1; "% positive" is the share of patient samples with detectable staining.
| Cancer type | IHC score | Level | % positive |
|---|---|---|---|
| Thyroid Cancer | 0.75 | High | 100% |
| Bladder Cancer | 0.44 | Medium | 58% |
| Head and Neck Cancer | 0.42 | Medium | 75% |
| Colorectal Cancer | 0.39 | Medium | 73% |
| Endometrial Cancer | 0.31 | Medium | 75% |
| Ovarian Cancer | 0.31 | Medium | 50% |
| Gastric Cancer | 0.30 | Medium | 73% |
| Neuroendocrine Tumors | 0.25 | Medium | 50% |
| Pancreatic Cancer | 0.24 | Medium | 46% |
| Lung Cancer | 0.19 | Low | 42% |
| Liver Cancer | 0.17 | Low | 33% |
| Prostate Cancer | 0.14 | Low | 25% |
| Breast Cancer | 0.12 | Low | 27% |
| Testicular Cancer | 0.11 | Low | 25% |
| Cervical Cancer | 0.08 | Low | 25% |
| Skin Cancer | 0.06 | Low | 18% |
| Melanoma | 0.03 | Low | 8% |
Not detected by IHC in: lymphoma, kidney cancer, glioma.
Is CNR1 internalized?
No. The abstract states that the binding of SGIP1 to CNR1 promotes its surface expression and that SGIP1 knockdown reduces axonal surface expression, indicating that CNR1 does not internalize upon binding.
Sources: PMID 38864427 · PMID 35052795 · PMID 25772509 · PMID 23600761. AI-extracted from abstracts, so verify before citing.
CNR1 clinical trials
Clinical-stage (up to phase 3, any modality). Nuclens hasn't indexed trials for CNR1 yet. Search ClinicalTrials.gov for CNR1 trials.
CNR1 normal tissue expression
Normal-tissue expression in dose-limiting organs (kidney, liver, bone marrow, salivary glands) drives radioligand dosimetry risk. Nuclens is re-validating its normal-tissue values, so they are not shown here yet. See CNR1 in the Human Protein Atlas tissue atlas, and read how normal-tissue expression predicts radioligand dosimetry risk.
CNR1 gene essentiality (DepMap)
CRISPR knockout effect across 1249 cancer cell lines: 0.06 (not essential). Radioligands kill by radiation, not by blocking the target, so essentiality matters less than for inhibitors. A non-essential target can still be an excellent radioligand target.
Related thyroid cancer radioligand targets
c-MET (MET) · HER3 (ERBB3) · EPCAM · SSTR2 · EGFR · ITGAV · STEAP2 · FAP
See all radioligand therapy targets in thyroid cancer.
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Subcellular localization: UniProt via Open Targets (CC BY 4.0 / CC0). Tumor immunohistochemistry: Human Protein Atlas (CC BY-SA 4.0). Clinical trials: ClinicalTrials.gov (public domain). Gene essentiality: DepMap (CC BY 4.0). Internalization and shedding: AI-extracted from PubMed abstracts, so verify against the cited papers before relying on them. Nuclens is a first-pass triage layer, not a substitute for wet-lab validation or clinical dosimetry. Derived expression data on this page is shared under CC BY-SA 4.0.