Lexicon · NucLex for innovators
Target expression
Fully specified name: Target expression (concept)
The presence or amount of a target reported in a biological context.
- Scope note
- Expression alone does not establish accessibility or response.
- Synonyms
- None recorded as true synonyms in this context.
- Monograph
- Molecular targeting (planned; brief only)
- External mappings
- None recorded. In W0 no mapping to SNOMED CT® or any external authority is asserted for this entry. A future mapping record will carry source system, identifier, version, relation type, evidence, author, confidence where meaningful, and review state.
- Formal status
- Editorial entry only. It is not part of any released ontology and a prose edit here changes no formal definition.
Draft. This entry is an unreviewed draft. Its sources have not been checked by a named person and no domain reviewer has approved it. Treat every claim as provisional.
Notes
Target expression is a statement that a molecular target is present, and in what amount, in a stated biological setting: a tissue, a tumor, a cell population, or a single cell. Molecular biologists distinguish levels of expression. Messenger RNA expression means the gene is transcribed. Protein expression means the product is made. Surface expression means the protein is displayed where a circulating agent could reach it. A finding at one level is not a finding at the others.
The method shapes the number. Immunohistochemistry, flow cytometry, sequencing, and molecular imaging each measure something different, with different sampling, sensitivity, and scoring conventions. A result from one method is not interchangeable with a result from another, and a score from one laboratory's protocol may not match a score from a different protocol. An expression record therefore needs the method, the sample, the scoring rule, and the date.
Expression is also not the whole story. A target can be expressed and yet unreachable, shed into the circulation, internalized, or biologically irrelevant to the outcome of interest. Whether a patient whose tumor expresses a target will respond to an agent directed at it is a separate empirical question. NucLex records expression as a context-bound observation about a target and keeps accessibility and response as distinct claims with their own evidence.