CTSB as a Radioligand Therapy Target
CTSB, cathepsin B, is a cell-surface protein. In Human Protein Atlas immunohistochemistry, CTSB staining is highest in thyroid cancer (100% of samples positive), endometrial cancer (100% of samples positive) and cervical cancer (92% of samples positive). Clinical status: Discovery-stage (no clinical drug program).
Is CTSB 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: Not yet assessed.
- ⚠️ Clinical precedent: Discovery-stage (no clinical drug program)
- ❔ Shedding: Not yet assessed.
- ❔ Normal-tissue dosimetry: Check kidney, liver, bone marrow and salivary expression in the Human Protein Atlas tissue atlas.
CTSB expression in cancer
Protein expression of CTSB 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 | 1.00 | High | 100% |
| Endometrial Cancer | 0.94 | High | 100% |
| Cervical Cancer | 0.75 | High | 92% |
| Liver Cancer | 0.73 | High | 73% |
| Kidney Cancer | 0.70 | High | 82% |
| Glioma | 0.69 | High | 100% |
| Ovarian Cancer | 0.69 | High | 83% |
| Colorectal Cancer | 0.61 | High | 83% |
| Breast Cancer | 0.60 | High | 80% |
| Head and Neck Cancer | 0.58 | High | 75% |
| Lung Cancer | 0.58 | High | 82% |
| Lymphoma | 0.56 | High | 83% |
| Prostate Cancer | 0.56 | High | 75% |
| Neuroendocrine Tumors | 0.50 | Medium | 75% |
| Gastric Cancer | 0.46 | Medium | 73% |
| Bladder Cancer | 0.44 | Medium | 67% |
| Melanoma | 0.42 | Medium | 75% |
| Pancreatic Cancer | 0.28 | Medium | 50% |
| Skin Cancer | 0.22 | Medium | 50% |
| Testicular Cancer | 0.17 | Low | 20% |
Is CTSB internalized?
Nuclens has not yet extracted internalization evidence for CTSB. Internalization matters for radioligands because an internalizing receptor traps the radionuclide inside the tumor cell. Run a full analysis to pull the latest literature.
CTSB clinical trials
Discovery-stage (no clinical drug program). Nuclens hasn't indexed trials for CTSB yet. Search ClinicalTrials.gov for CTSB trials.
CTSB 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 CTSB in the Human Protein Atlas tissue atlas, and read how normal-tissue expression predicts radioligand dosimetry risk.
CTSB gene essentiality (DepMap)
CRISPR knockout effect across 1258 cancer cell lines: 0.07 (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.
See how CTSB ranks against 15,000 targets for your indication.
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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.