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Introduction: Colorectal carcinoma does not have a single specific biomarker that can detect and predict disease behavior and response to therapy. Consequently, combinations of expression markers may be useful in both diagnostics and prognostics. Moreover, it is likely that the complex interaction between tumor epithelium and stroma is a key facilitator in sustaining tumor growth and could provide a powerful source of information for disease management. Methods: Colectomy specimens from 36 patients with colorectal carcinoma were included in the study. Epithelium and stroma of matched normal and cancerous colonic tissues were isolated by laser capture microdissection (LCM) of fresh-frozen specimens. Reverse phase microarrays were constructed by printing lysates of the LCM material on nitrocellulose-coated glass slides. The slides were probed with 62 phospho-specific and total protein antibodies. Stained slides were analyzed with MicroVigene™ software to determine relative intensities of each protein. Statistical analyses were performed using Statistical Analysis of Microarrays algorithm (SAM), Random Forests and Hierarchical Clustering. Results: There was striking heterogeneity in protein expression between the patients and between the epithelial and stromal tissue types. Supervised and unsupervised clustering analyses indicated that global signaling pathway portraits of tumor epithelium and stroma were more similar than their corresponding normal tissue counterparts. The strongest determinants of the epithelial-stromal tumor portrait include the phosphorylated forms of p38, Ras-GRF and IκB, as well as cleaved caspase-3 and Paxillin. Moreover, analysis of the coordinated signaling across pathways revealed that there was a significant and increasing degree of epithelial-stromal cross-talk that correlated with advancing Dukes’ Stage (fdr = 0.175). In particular, phosphorylated STAT5 and E-Cadherin become highly correlated in advanced stage tumors compared with normal colon mucosa, (r=-0.31 in normal and r=0.91 in advanced tumors). Conclusions: This is the first study to perform isolated functional mapping of the epithelial and stromal components of colorectal cancer tumors from human patients at a cellular signaling level. Since the portraits analyzed are comprised of phosphorylated signaling molecules, which are drug targets themselves, the read-out represents a functional map for therapeutic intervention. The greater similarity between protein expression in tumor epithelium and matched stroma compared to the corresponding normal tissue compartments from the same patient, supports the hypothesis of tumor-stromal cross talk and underscores the future potential to target tumor stroma therapeutically.

[Proc Amer Assoc Cancer Res, Volume 47, 2006]