Flow cytometric detection of prostate tumor cells using chemoaffinity labels

Area of Science:

• Biochemistry
• Oncology
• Medical Diagnostics

Background:

• Prostate-specific membrane antigen (PSMA) is a key biomarker for prostate cancer, crucial for imaging and therapy.
• Detecting circulating prostate tumor cells (CTCs) using PSMA remains an underexplored area.
• This research focuses on PSMA-targeted fluorescent probes for CTC detection.

Purpose of the Study:

• To develop and optimize a method for specific labeling of PSMA-positive (PSMA+) prostate cancer cells.
• To quantify PSMA+ cells in blood samples using flow cytometry (FC).
• To assess the utility of fluorescent PSMA inhibitors for detecting circulating prostate tumor cells.

Main Methods:

• PSMA+ (LNCaP) and PSMA- (DU145) cells were incubated with a fluorescent PSMA inhibitor (FAMX-CTT-54).
• Optimization of incubation parameters (time, temperature, concentration) was performed.
• A flow cytometry gating strategy using CD45 and PSMA double labeling was established for quantification in blood, with nonfluorescent beads as internal standards.

Main Results:

• The fluorescent PSMA inhibitor FAMX-CTT-54 demonstrated specificity for PSMA+ cells.
• Optimal labeling conditions were determined as 7.5 minutes at 37°C with 35 nM FAMX-CTT-54.
• Specific binding was confirmed by reduced fluorescence upon pre-incubation with unlabeled PSMA inhibitor.
• Detection of LNCaP cells in blood samples showed an average of 5 cells in a 115 µl sample (29 cells/ml), closely matching theoretical expectations.

Conclusions:

• Fluorescent PSMA inhibitors are effective for detecting and quantifying PSMA+ cells via flow cytometry.
• This approach supports the application of FC for detecting, quantifying, and characterizing circulating prostate tumor cells.
• The findings pave the way for improved diagnostic tools in prostate cancer management.