Prognostic value of soluble intercellular adhesion molecule-1 (sICAM-1) in body fluids of cancer patients
Abstract
The infiltration of tumor stroma by immune cells has traditionally been explained as an attempt of the host immune system to erradicate the tumor cells. More recently, a series of protumor activities, mediated mostly by the cells of innate immunity, have been reported.
Among the genes upregulated both in inflammatory conditions and in cancer are the genes involved in cell-cell interactions. Intercellular adhesion molecule-1 represents one of the most studied gene products.
This molecule exists both in a membrane-bound (ICAM-1), and in a soluble, free form (sICAM-1). In contrast to ICAM-1, which is directly involved in the cell-to-cell interactions, sICAM-1 presumably inhibits immune cell interactions by competing for the cellular binding sites.
Increased concentrations of sICAM-1 have been detected in serum of cancer patients as well as in fluids proximal to tumor tissue. These fluids, eg. pleural fluids, are believed to be more closely related to the underlying pathology than the blood plasma.
There are indications that sICAM-1 is generated in pleural space in a regulated manner. It has been hypothesized that sICAM-1 may interfere with the tumoricidal action of T cells and hence it may compromize the host antitumor activities.
However, this hypothesis is challenged by sICAM-1 in cancer-related pleural effusions since, in contrast to common inflammatory markers, it shows a positive correlation with the survival time.