International Tissue Array Study
An international multi-institutional working group has been established to address pertinent translational research questions that cannot be adequately addressed by a single research institution. One overlapping area of interest to researchers studying bladder cancer is the identification of biomarkers relevant to the biology and therapy of this disease. The creation of an international multi-institutional tissue resource will allow sharing of bladder tumor specimens and establishing tissue microarrays in order to conduct highly powered multivariate biomarker studies to improve our understanding of the relevant biology of TCC, and to allow for the development of more effective therapy.
The goals of the international bladder cancer tissue array:
- To establish an international multi-institutional tissue resource and database to create tissue microarrays using archival paraffin blocks of stage pT3 transitional cell carcinoma of the bladder. At least 20 institutions will contribute 30 cases each for a total of 600 cases.
- To exchange stained sections to evaluate the reproducibility of immunohistochemical staining and interpretation.
- To evaluate the prognostic and predictive utility of multiple markers using tissue microarray blocks. Markers to be evaluated will be p53, Ki67, EGFR, erbB2, cyclinD1, Rb, VEG-F and E-Cadherin. Outcome will be disease-free survival. Data will be stratified by lymph node status and adjuvant treatment.
The tissue microarray (TMA) technology was developed to allow efficient immunohistochemical and in situ hybridization analysis of large numbers of tumors. Tissue microarrays are constructed by collecting a cylindrical core tissue biopsy from one or more representative regions of a regular formalin-fixed, paraffin-embedded tumor block. This core (diameter 0.6 mm, height 3-4 mm) taken from the "donor" is now precisely arrayed into a new "recipient" paraffin block using a custom-built instrument (Beecher Instruments). As many as 1,000 cylindrical tissue biopsy specimens from individual tumors can be distributed in a single tissue microarray, allowing analysis of a thousand tumors at the RNA, DNA or protein level. Up to 200 consecutive sections of 4- to 5-µm thickness can be cut from each tumor array block. This technique allows parallel analyses of a large number of molecular markers.
Tissue Array Proposal
Tissue array blocks will be constructed from samples provided by multiple institutions. We expect 500 node negative pT3 archival tumor blocks will be used from 20 institutions to construct a set of tissue microarrays. Arrays containing these samples will be constructed at University of Basel (Dr. G. Sauter). These arrays will be tested for expression of p53, Ki67, EGFR, erbB2, cyclinD1, Rb, VEGF and E-Cadherin using standard immunohistochemistry assays. Those assays, done in replicate sections by multiple institutions, will use agreed upon protocols for staining and established criteria for interpretation. The sections will also be exchanged to allow other institutions to score identical sections.
Expression of these eight antigens will be tested for their ability to predict outcome in this set of 500 pT3 bladder transitional cell carcinomas. Requirements for inclusion in these arrays will be pT3 tumors, node negative (with at least one lymph node examined), having at least three years of follow-up (known disease status) following cystectomy. Cases will be stratified for grade and adjuvant chemotherapy. An additional 100 tumors will be requested (five/site) with known node positivity to compare prevalence of expression changes. Patients receiving neoadjuvant and/or radiation therapy will be excluded. Pure adenocarcinoma, squamous cell carcinoma and small cell neuroendocrine carcinoma are excluded. Presence of squamous or glandular differentiation is acceptable.