MICs shed light on prostate cancer

Usual immune system role of a molecule is counteracted by shedding in prostate cancer

August 16, 2004. The body's immune system has built in anti-tumor mechanisms. Cancers don't form unless the tumor cells develop the means to avoid being attacked by this defense mechanism.

There are several different methods by which the immune system can get rid of tumors early in their development. One way employs a specific molecule, the MHC class I chain-related molecule (MIC), which is often expressed on the surface of some tumor cells. MICs interact with the immune system's natural killer cells and trigger them to destroy the tumor cells.

Jennifer Wu at the University of Washington is looking into how prostate cancers evade this anti-tumor defense strategy. Her team found that MIC-expressing prostate cancer cell lines are able to activate natural killer cells. Initially, this defense mechanism appears intact.

Analysis of prostate tumor biopsies, however, shows that the cell surface localization of MIC is highest in early-stage tumors. The researchers note that tumors from later-stage patients can no longer activate natural killer cells. High levels of soluble MIC in the blood serum occur in these patients.

The later stage tumors shed the MIC from their cell surfaces. Because of this, some (aggressive) prostate cancer cells evade this particular form of immune surveillance. Can anything herlp?

Wu and her team say the deficiency in the ability to activate natural killer cells can be overcome in tissue culture by stimulating the cells with a powerful immune system booster, the cytokine IL-2 or IL-15.

The authors looked closer at how soluble MIC level in blood related to prostate-specific antigen (PSA). PSA measurements are used as a test, or biomarker, for presence of prostate cancer. Wu has found that soluble MIC serum levels do not correspond with PSA serum levels, but they do correspond closely with high-grade and invasive tumor status in prostate cancer patients.

This new work indicates that one key to prostate cancer progression may be the ability of evade the MIC activated immune surveillance system. So, while soluble MIC measurement may be a useful biomarker for disease progression, cytokine treatment may aid in reviving natural killer cell anti-tumor activity.

Research article title: Prevalent expression of the immunostimulatory MHC class I chain-related molecule is counteracted by shedding in prostate cancer

View the PDF of the original research article at: https://www.the-jci.org/press/22206.pdf

This story edited by J. Strax; page last updated Aug 15, 2004.

Information on this website is not intended as medical advice nor to be taken as such. Consult qualified physicians specializing in the treatment of prostate cancer. Neither the editors nor the publisher accepts any responsibility for the accuracy of the information or consequences from the use or misuse of the information contained on this website.

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