FLT1 as a Radioligand Therapy Target
FLT1, fms related receptor tyrosine kinase 1, is a cell-surface protein (RTK). In Human Protein Atlas immunohistochemistry, FLT1 staining is highest in head and neck cancer (100% of samples positive), bladder cancer (42% of samples positive) and melanoma (50% of samples positive). Published literature suggests FLT1 does not readily internalize, so radionuclide retention may rely on surface binding. Clinical status: Clinical-stage (up to phase 3, any modality).
Is FLT1 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: Medium IHC staining in head and neck 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.
FLT1 expression in cancer
Protein expression of FLT1 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 |
|---|---|---|---|
| Head and Neck Cancer | 0.50 | Medium | 100% |
| Bladder Cancer | 0.22 | Medium | 42% |
| Melanoma | 0.20 | Medium | 50% |
| Pancreatic Cancer | 0.12 | Low | 36% |
| Ovarian Cancer | 0.08 | Low | 17% |
| Breast Cancer | 0.08 | Low | 13% |
| Gastric Cancer | 0.07 | Low | 10% |
| Kidney Cancer | 0.03 | Low | 9% |
Not detected by IHC in: skin cancer, colorectal cancer, lymphoma, thyroid cancer, neuroendocrine tumors, cervical cancer, lung cancer, prostate cancer, testicular cancer, endometrial cancer, glioma, liver cancer.
Is FLT1 internalized?
No. VEGF-A selectively inhibits FLT1 ectodomain shedding independent of receptor activation and receptor endocytosis.
Sources: PMID 29719170 · PMID 23932502 · PMID 23465835 · PMID 21209384 · PMID 20838437. AI-extracted from abstracts, so verify before citing.
FLT1 clinical trials
Clinical-stage (up to phase 3, any modality). Nuclens hasn't indexed trials for FLT1 yet. Search ClinicalTrials.gov for FLT1 trials.
FLT1 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 FLT1 in the Human Protein Atlas tissue atlas, and read how normal-tissue expression predicts radioligand dosimetry risk.
FLT1 gene essentiality (DepMap)
CRISPR knockout effect across 1251 cancer cell lines: 0.03 (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 head and neck cancer radioligand targets
EGFR · c-MET (MET) · HER3 (ERBB3) · ITGAV · SSTR2 · B7-H3 (CD276) · STEAP2 · Mesothelin (MSLN)
See all radioligand therapy targets in head and neck 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.