Human prostatic-carcinoma cells modulate lymphocyte-proliferation by an immunosuppressive activity

Area of Science:

• Immunology
• Cancer Biology
• Prostate Cancer Research

Background:

• Androgen-independent prostate cancer cells (JCA-1) constitutively produce an immunosuppressive factor.
• This factor impacts normal human peripheral blood lymphocyte proliferation.

Purpose of the Study:

• To identify and characterize the immunosuppressive activity produced by JCA-1 cells.
• To understand the mechanism by which this activity affects lymphocyte function.

Main Methods:

• Conditioned medium from JCA-1 cells was used to assess immunosuppressive activity.
• Semi-purification involved ion-exchange chromatography and gel filtration.
• Lymphocyte proliferation assays, cell cycle analysis, and sensitivity tests (heat, reducing agent, protease) were performed.

Main Results:

• A dose-dependent, irreversible suppression of normal human peripheral blood lymphocyte proliferation was observed.
• The immunosuppressive factor has an apparent molecular weight of 40-55 kDa.
• The activity is heat-labile, sensitive to reducing agents and proteases, and does not induce lymphocyte apoptosis.
• It specifically inhibits lymphocyte entry from the G1 to S phase of the cell cycle.

Conclusions:

• JCA-1 cells secrete a potent immunosuppressive factor that impairs lymphocyte proliferation by cell cycle arrest.
• This factor may play a role in the immune evasion mechanisms of androgen-independent prostate cancer.