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Commonly observed in colorectal cancer is the elevated expression of the prostaglandin (PG) synthase COX-2. In normal intestinal epithelium, the COX-2 mRNA is targeted for rapid decay through the 3′-untranslated region (3′-UTR) adenylate- and uridylate (AU)-rich element (ARE), whereas in tumors ARE-mediated decay is compromised. Here we show that the COX-2 ARE can mediate degradation through microRNA (miRNA)-mediated regulation. We identified miR-16 to bind the COX-2 3′-UTR and inhibit COX-2 expression by promoting rapid mRNA decay. In colorectal cancer cells and tumors, miR-16 levels were decreased approximately twofold and miR-16 expression in cancer cells attenuated COX-2 expression and PG synthesis. The COX-2 ARE is also bound by the RNA-binding protein HuR. In colorectal cancer tumors, HuR is overexpressed and localized within the cytoplasm, where it promotes ARE-mRNA stabilization. Under conditions of HuR overexpression, miR-16 was unable to promote rapid mRNA decay through the COX-2 ARE. Ribonucleoprotein immunoprecipitation of HuR showed direct association with miR-16 that was reversed when cytoplasmic trafficking of HuR was inhibited. Furthermore, this interaction between HuR and miR-16 promoted the downregulation of miR-16. These new results identify miR-16 as a central posttranscriptional regulator of COX-2 and show the ability of elevated levels of HuR to antagonize miR-16 function. Along with insight into altered ARE-mediated mRNA decay observed in colorectal cancer, these findings provide a new explanation for tumor-derived loss of miR-16. Mol Cancer Res; 10(1); 167–80. ©2011 AACR.

Tumor-associated macrophages (TAM) play a controversial role in epithelial–mesenchymal transition (EMT) and prognosis of colorectal cancer (CRC). In particular, the microlocalization, polarization and prognostic impact of TAM in the immediate environment of invading CRC cells has not yet been established. To address this clinically relevant question, intraepithelial (iCD68) and stromal macrophages (sCD68), M1-macrophages (iNOS), M2-macrophages (CD163), cytokeratin-positive cancer cells (tumor buds) and expression of the anti-phagocytic marker CD47 were investigated in primary tumors of 205 well-characterized CRC patients. Cell-to-cell contacts between tumor buds and TAM were detected using high-resolution digital scans. The composition of the tumor microenvironment was analyzed with clinicopathological and molecular features. High CD68 counts predicted long term overall survival independent of microlocalization (iCD68 p=0.0016; sCD68 p=0.03), pT, pN, pM and post-operative therapy. CD68 infiltration correlated with significantly less tumor budding (iCD68 p=0.0066; sCD68 p=0.0091) and absence of lymph node metastasis (sCD68 p=0.0286). Cell-to-cell contact of sCD68 and invading cancer cells was frequent and ameliorated the detrimental prognostic effect of the tumor budding phenotype. Subgroup analysis identified long-term survival with CD47 loss and predominance of CD163⁺ M2 macrophages (p = 0.0366). CD163⁺ macrophages represented 40% of the total population, and positively correlated with total CD68 macrophage numbers (r[CD68/CD163] = 0.32; p = 0.0001). Strong CD163 infiltration predicted lower tumor grade (p = 0.0026) and less lymph node metastasis (p = 0.0056). This study provides direct morphological evidence of an interaction between TAM and infiltrating cancer cells. The prognostic impact of TAM is modulated by phenotype, microlocalization and the expression of anti-phagocytic markers in CRC.

Tapasin is a crucial component of the major histocompatibility (MHC) class I antigen presentation pathway. Defects in this pathway can lead to tumor immune evasion. The aim of this study was to test whether tapasin expression correlates with CD8+ cytotoxic T lymphocyte (CTL) infiltration of colorectal cancer (CRC) and overall survival. A next-generation tissue microarray (ngTMA) of 198 CRC patients with full clinicopathological information was included in this study. TMA slides were immunostained for tapasin, MHC I and CD8. Marker expression was analyzed with immune-cell infiltration, patient survival and TNM-staging. A reduction of tapasin expression strongly correlated with venous invasion (AUC 0.682, OR 2.7, p = 0.002; 95 % CI 1.7–5.0), lymphatic invasion (AUC 0.620, OR 2.0, p = 0.005; 95 % CI 1.3–3.3), distant metastasis (AUC 0.727, OR 2.9, p = 0.004; 95 % CI 1.4–5.9) and an infiltrative tumor border configuration (AUC 0.621, OR 2.2, p = 0.017; 95 % CI 1.2–4.4). Further, tapasin expression was associated with CD8+ CTL infiltration (AUC 0.729, OR 5.4, p < 0.001; 95 % CI 2.6–11), and favorable overall survival (p = 0.004, HR 0.6, 95 % CI 0.42–0.85). Consistent with published functional data showing that tapasin promotes antigen presentation, as well as tumor immune recognition and destruction by CD8+ CTLs, a reduction in tapasin expression is associated with tumor progression in CRC.

// <![CDATA[ $('.header-date').hide();$('#titleAuthors').hide();$('#abstractHeader').hide(); // ]]> Christian Schafroth1, José A. Galván1, Irene Centeno1, Viktor H. Koelzer1,2, Heather E. Dawson1,2, Lena Sokol1, Gregor Rieger1,2, Martin D. Berger3, Marion Hädrich4, Robert Rosenberg5, Ulrich Nitsche6, Beat Schnüriger4, Rupert Langer1,2, Daniel Inderbitzin4,7, Alessandro Lugli1,2 and Inti Zlobec1 1 Translational Research Unit, Institute of Pathology, Bern University Hospital, Bern, Switzerland 2 Division of Clinical Pathology, Institute of Pathology, University of Bern, Bern, Switzerland 3 Department of Medical Oncology, Bern University Hospital, Bern, Switzerland 4 Visceral Surgery and Medicine, Bern University Hospital, Bern, Switzerland 5 Department of Surgery, Kantonsspital Baselland, Liestal, Switzerland 6 Department of Surgery, Klinikum rechts der Isar, Technische Universität München, Munich, Germany 7 Department of Surgery, Tiefenau Hospital, Bern, Switzerland Correspondence to: Inti Zlobec, email: // <![CDATA[ mail("inti.zlobec","pathology.unibe",27,"") // ]]> Keywords: colorectal cancer, BRAF, VE1, heterogeneity, prognosis, metastasis, Pathology Section Received: September 22, 2015 Accepted: October 04, 2015 Published: October 19, 2015