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Modulation of TcR/CD3-zeta chain expression by a circulating factor derived from ovarian cancer patients
D D Taylor1, D P Bender, Gerçel-Taylor C
1Department of Obstetrics, University of Louisville School of Medicine, Louisville, KY 40292, USA.
Abstract:
In women with ovarian cancer, suppression of components of the immune system may promote tumour development. Previous studies in ovarian cancer have demonstrated that decreased expression and function of the T-cell receptor (TcR)-associated signal transducing zeta-chain correlates with deficient immune responsiveness of T cells. In this study, sera and ascitic fluids obtained from woman with advanced ovarian cancer were found to suppress the expression of TcR-associated zeta chain. This suppression of zeta chain expression was dose-dependent and was not observed with biologic fluids obtained from healthy women. The factor responsible for the loss of zeta chain was purified from ascites and characterized as a protein with an appropriate molecular weight of 14 kD. Suppression of T-cell TcR-zeta was specific, since neither lck nor ZAP-70 expression was affected, while zeta chain was almost completely suppressed. This selective suppression of TcR-zeta expression by the 14 kD ascites-derived factor was shown to operate at the mRNA level. By defining the mechanism through which this protein modulates TcR-zeta chain levels, it might be possible to ultimately prevent the suppressive influences of the tumour microenvironment and restor immune competence in patients with ovarian carcinoma.
Insights
A novel 14 kD protein found in ovarian cancer ascites suppresses T-cell receptor zeta-chain expression. This discovery offers potential therapeutic targets to restore immune function in ovarian carcinoma patients.
Area of Science:
- Immunology
- Oncology
- Biochemistry
Background:
- Immune system suppression contributes to ovarian tumor development.
- Decreased T-cell receptor (TcR)-associated zeta-chain expression correlates with impaired T-cell responsiveness in ovarian cancer.
- Understanding immune evasion mechanisms is crucial for treating ovarian cancer.
Purpose of the Study:
- To investigate the role of ovarian cancer-associated fluids in immune suppression.
- To identify and characterize factors within ascites fluid that affect T-cell function.
- To elucidate the molecular mechanisms underlying T-cell hyporesponsiveness in advanced ovarian cancer.
Main Methods:
- Analysis of sera and ascitic fluids from ovarian cancer patients and healthy controls.
- Quantification of T-cell receptor zeta-chain expression.
- Purification and characterization of a suppressive factor from ascites.
- Assessment of the factor's effect on mRNA levels of TcR-zeta, lck, and ZAP-70.
Main Results:
- Ascitic fluids and sera from ovarian cancer patients suppressed TcR-associated zeta-chain expression in a dose-dependent manner.
- A 14 kD protein was purified from ascites and identified as the suppressive factor.
- The factor selectively suppressed TcR-zeta chain expression at the mRNA level, without affecting lck or ZAP-70.
- This suppression was not observed with biological fluids from healthy individuals.
Conclusions:
- A specific 14 kD protein in ovarian cancer ascites actively suppresses T-cell receptor zeta-chain expression.
- This mechanism contributes to immune suppression within the tumor microenvironment.
- Targeting this protein could be a strategy to restore anti-tumor immunity in ovarian cancer.