Cross validation of cluster analysis using immunostained multi-tissue tumour block slides.

We assayed the panel of SCLC MAbs using multi-tissue tumour block (MTTB) slides obtained from Dr. Hector Battifora (City of Hope Hospital, Duarte CA). MTTB slides contain up to 100 different formalin-fixed tumour tissue specimens and can be immunostained with as little as 50 microliters of antibody solution. In this study, the MAbs in the SCLC panel were used to stain slides from a MTTB comprised of eight normal, ten SCLC, ten squamous cell, ten adenocarcinoma and five undifferentiated lung cancer tissues. Many MAbs in the SCLC panel failed to immunostain the lung MTTB whereas many others showed significant immunoreactivity. Of those MAbs that stained SCLC tissue, none was found to be specific; these MAbs also stained NSCLC tissues or normal lung tissues. Some MAbs in the panel immunostained SCLC and NSCLC tissues, but were also reactive to normal lung tissue as well as other normal tissue specimens. A major advantage of immunostaining MTTBs with a panel of MAbs is that we were able to compare the immunoreactivity of the MAbs on a total of 128 different tissues requiring only 100 microliters of antibody solution using only two MTTB slides per MAb. Although this study was preliminary and certain technical problems in assembling the MTTB as well as optimising the immunostaining procedure for handling 98 or more MAbs simultaneously remain, the MTTB technique remains promising.