Related Experiment Video
Updated: Jul 3, 2026
MR Molecular Imaging of Prostate Cancer with a Small Molecular CLT1 Peptide Targeted Contrast Agent
Published on: September 3, 2013
Tomoregulin internalization confers selective cytotoxicity of immunotoxins on prostate cancer cells
Xiao-Yan Zhao1, Hsiao-Lai Liu, Bing Liu
1Department of Cancer Research, Berlex Biosciences, Richmond, CA, USA.
Abstract:
We have recently identified and validated the prostate cancer antigen Tomoregulin as a target for the radioimmunotherapy for prostate cancer. Here, we provide evidence that Tomoregulin is an internalizing antigen and a potential target for immunotoxins. First, the cell surface localization of Tomoregulin was confirmed by flow cytometry, and its expression levels were determined by whole-cell binding assays. Second, laser scanning confocal microscopy revealed Tomoregulin internalization into the cytoplasm on antibody binding at 37 degrees C. The internalized Tomoregulin was found to colocalize with acidic vesicles. Third, internalization kinetics assays using (125)I-labeled anti-Tomoregulin mouse monoclonal antibody 2H8 demonstrated that the amount of internalized antigen-antibody complexes increased with time and reached approximately 25% of the total surface antigen after 60 to 90 minutes. Because 2H8 is capable of binding to Tomoregulin on the cell surface and can be internalized, we finally evaluated 2H8 as a means of targeting toxic payloads to prostate cancer cells. 2H8 was coupled to the cytotoxin saporin through a secondary antibody (Mab-ZAP) in indirect immunotoxin assays. Cell killing occurred on Tomoregulin-positive cells (Clone69) at the immunotoxin concentrations not affecting the Tomoregulin-negative cells (PC-3). In contrast to 2H8, the control antibody (mouse anti-c-Myc antibody 9E10) had no effect on cells in the presence of Mab-ZAP. Thus, Tomoregulin internalization confers selective cytotoxicity of immunotoxins on prostate cancer cells, and Tomoregulin-mediated delivery of immunotoxin has potential as a prostate cancer therapy.
Insights
Prostate cancer antigen Tomoregulin is an internalizing target for immunotoxins. This study shows Tomoregulin-targeted immunotoxins selectively kill prostate cancer cells, offering a new therapeutic strategy.
Area of Science:
- Oncology
- Immunotherapy
- Molecular Biology
Background:
- Prostate cancer remains a significant health concern, necessitating novel therapeutic targets.
- Radioimmunotherapy and immunotoxins are promising approaches for targeted cancer treatment.
- Tomoregulin has been identified as a potential target antigen for prostate cancer therapy.
Purpose of the Study:
- To investigate Tomoregulin's internalization properties for targeted therapy.
- To evaluate Tomoregulin as a target for immunotoxin-mediated cancer cell killing.
- To assess the therapeutic potential of Tomoregulin-targeted immunotoxins in prostate cancer.
Main Methods:
- Flow cytometry and whole-cell binding assays confirmed Tomoregulin cell surface expression.
- Laser scanning confocal microscopy visualized Tomoregulin internalization upon antibody binding.
- Internalization kinetics assays quantified antigen-antibody complex uptake.
- Indirect immunotoxin assays assessed cell killing efficacy using antibody-cytotoxin conjugates.
Main Results:
- Tomoregulin is expressed on the surface of prostate cancer cells and internalizes into the cytoplasm.
- Internalized Tomoregulin colocalizes with acidic vesicles.
- Antibody-mediated internalization of Tomoregulin reached approximately 25% within 90 minutes.
- Immunotoxins targeting Tomoregulin selectively killed Tomoregulin-positive prostate cancer cells without affecting negative cells.
Conclusions:
- Tomoregulin is an internalizing antigen suitable for targeted drug delivery.
- Targeted delivery of immunotoxins via Tomoregulin demonstrates selective cytotoxicity against prostate cancer cells.
- Tomoregulin-mediated immunotoxin therapy holds potential as a novel treatment for prostate cancer.
