Context-dependent adaption of EpCAM expression in early systemic esophageal cancer.

The role of the epithelial cell adhesion molecule EpCAM in cancer progression remains largely unclear. High expression of EpCAM in primary tumors is often associated with more aggressive phenotypes and EpCAM is the prime epithelial antigen in use to isolate circulating tumor cells (CTCs) and characterize disseminated tumor cells (DTCs). However, reduced expression of EpCAM was associated with epithelial-to-mesenchymal transition (EMT) and reports on a lack of EpCAM on CTCs emerged. These contradictory observations might reflect a context-dependent adaption of EpCAM expression during metastatic progression. To test this, EpCAM expression was monitored in esophageal cancer at different sites of early systemic disease. Although most of the primary esophageal tumors expressed high levels of EpCAM, the majority of DTCs in bone marrow lacked EpCAM. In vitro, downregulation of EpCAM expression at the plasma membrane was observed in migrating and invading cells, and was associated with a partial loss of the epithelial phenotype and with significantly decreased proliferation. Accordingly, induction of EMT through the action of TGFß resulted in substantial loss of EpCAM cell surface expression on esophageal cancer cells. Knock-down or natural loss of EpCAM recapitulated these effects as it reduced proliferation while enhancing migration and invasion of cancer cells. Importantly, expression of EpCAM on DTCs was significantly associated with the occurrence of lymph node metastases and with significantly decreased overall survival of esophageal cancer patients. We validated this observation by showing that high expression of EpCAM promoted tumor outgrowth after xenotransplantation of esophageal carcinoma cells. The present data disclose a dynamic expression of EpCAM throughout tumor progression, where EpCAM(high) phenotypes correlate with proliferative stages, whereas EpCAM(low/negative) phenotypes associated with migration, invasion and dissemination. Thus, differing expression levels of EpCAM must be taken into consideration for therapeutic approaches and during clinical retrieval of disseminated tumor cells.

[Comparison of different stool tests for the detection of cancer of the colon]. / Vergleich verschiedener Stuhltests zur Detektion von Neoplasien des Kolon.

BACKGROUND AND OBJECTIVE: Colonoscopy is the gold standard for the diagnosis of colonic neoplasia. Because of the low compliance, the discomfort of bowel preparation and the procedure itself and the (albeit small) risk of perforation or bleeding alternative procedures such as stool tests are being focused on. PATIENTS AND METHODS: After informed consent stool samples of 116 patients (44 male, 72 female, median age 47 years), scheduled for colonoscopy and 22 patients (17 m, 5 f, 69 y) with known colorectal cancer stool samples were collected. The samples were investigated by three methods: a biochemical (Guajak) test for fecal occult blood, an immunological test for fecal occult blood and a test determining the dimer pyruvat kinase M2 (tumor M2-PK). RESULTS: Sensitivity for detection of colorectal cancer or polyps was 27 % and 10 % for the biochemical test, 91 % and 19 % for the immunological test and 77 % and 48 % for the M2-PK-test, respectively. Specificity was 89 %, 94 % and 72 %, respectively. CONCLUSIONS: Both methods for detection of occult blood had a similar specificity. The sensitivity of the immunological test for the detection of colorectal cancer was significantly higher. The M2-PK-test had a markedly lower specificity in diagnosing cancer. Because of the low sensitivity for polyps the usefulness of stool tests is questionable. Reducing incidence and mortality of colorectal cancer should be achieved by colonoscopy, a recommendation that requires specific communication to the public.

The nucleus-encoded HCF107 gene of Arabidopsis provides a link between intercistronic RNA processing and the accumulation of translation-competent psbH transcripts in chloroplasts.

To understand the functional significance of RNA processing for the expression of plastome-encoded photosynthesis genes, we investigated the nuclear mutation hcf107 of Arabidopsis. The mutation is represented by two alleles, both of which lead to a defective photosystem II (PSII). In vivo protein labeling, in vitro phosphorylation, and immunoblot experiments revealed that the psbB gene product (CP47) and an 8-kD phosphoprotein, the psbH gene product (PsbH), are absent in mutant plants. PsbH and PsbB are essential requirements for PSII assembly in photosynthetic eukaryotes, and their absence in hcf107 is consistent with the PSII-less mutant phenotype. RNA gel blot hybridizations showed that the hcf107 mutation specifically impairs the accumulation of some but not all oligocistronic psbH transcripts that are released from the pentacistronic psbB-psbT-psbH-petB-petD precursor RNA by intergenic endonucleolytic cleavage. In contrast, neither the levels nor the sizes of psbB-containing RNAs are affected. S1 nuclease protection analyses revealed that psbH RNAs are lacking only where psbH is the leading cistron and that they are processed at position -45 in the 5' leader segment of psbH. These data and additional experiments with the cytochrome b(6)f complex mutant hcf152, which is defective in 3' psbH processing, suggest that only those psbH-containing transcripts that are processed at their -45 5' ends can be translated. Secondary structure analysis of the 5' psbH leader predicted the formation of stable stem loops in the nonprocessed transcripts, which are unfolded by processing at the -45 site. We propose that this unfolding of the psbH leader segment as a result of RNA processing is essential for the translation of the psbH reading frame. We suggest further that HCF107 has dual functions: it is involved in intercistronic processing of the psbH 5' untranslated region or the stabilization of 5' processed psbH RNAs, and concomitantly, it is required for the synthesis of CP47.