Immunohistochemistry is a commonly used method for determining the presence of various markers, such as tumor markers, on tissue. One major limitation of immunohistochemistry is that it is a qualitative test and is therefore subject to significant variability in the interpretation of the test result. Quantitative immunoassays, however, can not be directly applied to tissue because most tissues are comprised of various cell types, which may not all express a particular marker. We have developed a procedure for coupling laser capture microdissection (LCM) with quantitative immunoassays. LCM enables the user to collect individual cells of interest from a stained tissue section. After solubilization, cells collected by LCM can then be analyzed by quantitative soluble immunoassays. The feasibility of this approach was shown by collecting epithelial cells from prostate cancer tissue and then measuring the level of PSA, using an automated immunoassay analyzer. The PSA content from as little as ten cells could be accurately measured in this way. In the upcoming year, we plan to extend this type of analysis to other clinically relevant tumor markers, such as Her2/Neu.
