A single-chain fragment against prostate specific membrane antigen as a tool to build theranostic reagents for prostate cancer
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Updated: May 13, 2026
MR Molecular Imaging of Prostate Cancer with a Small Molecular CLT1 Peptide Targeted Contrast Agent
Published on: September 3, 2013
B Frigerio1, G Fracasso2, E Luison1
1Molecular Therapies Unit, Department of Experimental Oncology and Molecular Medicine, Fondazione IRCCS Istituto Nazionale dei Tumori, Milano, Italy.
Abstract:
Prostate carcinoma is the most common non-cutaneous cancer in developed countries and represents the second leading cause of death. Early stage androgen dependent prostate carcinoma responds well to conventional therapies, but relatively few treatment options exist for patients with hormone-refractory prostate cancer. One of the most suitable targets for antibody-mediated approaches is prostate specific membrane antigen (PSMA) which is a well known tumour associated antigen. PSMA is a type II integral cell-surface membrane protein that is not secreted, and its expression density and enzymatic activity are increased progressively in prostate cancer compared to normal prostate epithelium, thereby making PSMA an ideal target for monoclonal antibody imaging and therapy. To obtain a small protein that can better penetrate tissue, we have engineered a single-chain variable fragment (scFv) starting from the variable heavy and light domains of the murine anti-PSMA monoclonal antibody D2B. scFvD2B was analysed in vitro for activity, stability, internalisation ability and in vivo for targeting specificity. Maintenance of function and immunoreactivity as well as extremely high radiolabelling efficiency and radiochemical purity were demonstrated by in vitro assays and under different experimental conditions. Despite its monovalent binding, scFvD2B retained a good strength of binding and was able to internalise around 40% of bound antigen. In vivo we showed its ability to specifically target only PSMA expressing prostate cancer xenografts. Due to these advantageous properties, scFvD2B has the potential to become a good theranostic reagent for early detection and therapy of prostate cancers.
Insights
Researchers engineered a small protein targeting prostate specific membrane antigen (PSMA) for improved prostate cancer detection and therapy. This engineered antibody fragment, scFvD2B, shows potential as a theranostic reagent.
Area of Science:
- Oncology
- Immunology
- Biotechnology
Background:
- Prostate carcinoma is a leading cause of cancer death, with limited options for hormone-refractory disease.
- Prostate specific membrane antigen (PSMA) is a promising target due to its overexpression in prostate cancer.
- Existing antibody therapies face challenges with tissue penetration.
Purpose of the Study:
- To engineer a smaller, tissue-penetrating protein targeting PSMA.
- To evaluate the engineered single-chain variable fragment (scFvD2B) for in vitro and in vivo efficacy.
- To assess scFvD2B's potential as a theranostic reagent for prostate cancer.
Main Methods:
- Engineered a single-chain variable fragment (scFvD2B) from anti-PSMA monoclonal antibody D2B.
- Performed in vitro analyses for activity, stability, and internalisation.
- Conducted in vivo studies to assess targeting specificity in prostate cancer xenografts.
Main Results:
- scFvD2B demonstrated maintained function, high immunoreactivity, and efficient radiolabelling.
- The fragment exhibited strong binding affinity and antigen internalisation (approx. 40%).
- In vivo studies confirmed specific targeting of PSMA-expressing prostate cancer xenografts.
Conclusions:
- Engineered scFvD2B retains anti-PSMA binding and internalisation capabilities.
- scFvD2B shows specific targeting of prostate cancer xenografts in vivo.
- scFvD2B holds potential as an effective theranostic agent for prostate cancer detection and therapy.
