Platelet-activating factor and human thyroid cancer

Abstract

Objective: Platelet-activating factor (PAF) is a pro-inflammatory and angiogenic lipid mediator involved in several types of cancer in humans. The levels of PAF, lyso-PAF (the PAF precursor), phospholipase A2activity (PLA2, the enzymatic activity implicated in lyso-PAF formation) and acetylhydrolase activity (AHA, the PAF-degrading enzyme) were investigated in various diseased thyroid tissues.Subjects: Control and diseased tissue of patients with a hyperplastic goitre (n= 14), a benign adenoma (n= 12) and a papillary thyroid carcinoma (n= 15) were investigated.Results: PAF receptor transcripts were found in the human thyroid tissue. PAF, lyso-PAF, PLA2and AHA were present in control thyroid tissues, their levels being significantly correlated with each other, suggesting tiny regulations of the PAF metabolic pathways inside the thyroid gland. PAF, lyso-PAF, PLA2and AHA levels remained unchanged in diseased tissues of patients with a hyperplastic goitre, a benign adenoma and a papillary thyroid carcinoma. No difference was found between PAF, lyso-PAF, PLA2and AHA levels with respect to the TNM tumour status and the histological sub-type of papillary thyroid carcinoma. No correlation was found between tissue PAF levels and those of vascular endothelial growth factor and basic fibroblast growth factor, two angiogenic growth factors involved in thyroid cancer and that mediate their effect through PAF release in breast and colorectal cancer.Conclusion: PAF, PAF receptor transcripts and the enzymatic activities implicated in PAF production and degradation are present in the thyroid gland. While the physiological role of PAF is presently unknown in thyroid physiology, this study highlights no evidence for a potentially important role of PAF during human thyroid cancer, a result that markedly differs from breast and colorectal ones.