Cell-autonomous TGFbeta signaling is required for both induction and maintenance of in vitro invasiveness and metastasis during late-stage tumorigenesis. TGFbetaRII therefore represents a potential target for therapeutical intervention in human tumorigenesis.

Abstract.A recently described splice variant of CD44 expressed in metastasizing cell lines of rat tumors has been shown to confer metastatic potential to a nonmetastasizing rat pancreatic carcinoma cell line and to non-metastasizing sarcoma cells. Homologues of this variant as well as several other CIM4 splice variants are also expressed at the RNA level in human carcinoma cell lines from lung, breast, and colon, and in immortalized keratinocytes.Using antibodies raised against a bacterial fusion protein encoded by variant CD44 sequences, we studied the expression of variant CD44 glycoproteins in normal human tissues and in colorectal neoplasia. Expression of CD44 variant proteins in normal human tissues was readily found on several epithelial tissues including the squamous epithelia of the epidermis, tonsils, and pharynx, and the glandular epithelium of the pancreatic ducts, but was largely absent from other epithelia and from most non-epithelial cells and tissues. In human colorectal neoplasia CD44 variant proteins, ineluding homologues of those which confer metastatic ability to rat tumors, were found on all invasive carcinomas and carcinoma metastases. Interestingly, focal expression was also observed in adenomatous polyps, expression being related to areas of dysplasia. The distribution of the CD44 variants in human tissues suggests that they play a role in a few restricted differew tiation pathways and that in colorectal tumors one of these pathways has been reactivated. The finding that metastasis-related variants are already expressed at a relatively early stage in colorectal carcinogenesis and tumor progression, i.e., in adenomatous polyps, suggests the existence of a yet unknown selective advantage linked to CD44 variant expression. The continued expression in metastases would be compatible with a role in the metastatic process.T UMOR metastasis is the principal cause of death for cancer patients. A subset of parental tumor cells acquire metastatic properties, presumably through a series of genetic alterations (Nicolson 1987;Hart et al., 1989). As a result of this process of tumor progression, carcinoma ceils detach from the primary tumor, penetrate the basement membrane into the connective tissue and invade adjacent structures including lymph and blood vessels. The tumor cells are subsequently transported to sites of metastatic outgrowth via lymph or blood. This dissemination process obviously requires a complex series of interactions of tumor cells with extracellular matrix components and with other cells probably involving adhesion receptors, proteolytic enzymes, growth factors, and growth factor receptors.In an analysis of the metastatic properties of rat carcinoma cells, antibodies were raised that recognize antigens exclusively expressed in the metastasizing clonal variants of these tumors (Matzku et al., 1989). Using one of these antibodies, we have isolated eDNA sequences that encode splice variants of CD44 ; Rudy, W., M. Hofmann, R. Schwartz-Albiez, M. Z611er, K.-H. Heider, H. Ponta, and P. He...

With the objective of discovering novel putative intervention sites for anticancer therapy, we compared transcriptional profiles of breast cancer, lung squamous cell cancer (LSCC), lung adenocarcinoma (LAC), and renal cell cancer (RCC). Each of these tumor types still needs improvement in medical treatment. Our intention was to search for genes not only highly expressed in the majority of patient samples but which also exhibit very low or even absence of expression in a comprehensive panel of 16 critical (vital) normal tissues. To achieve this goal, we combined two powerful technologies, PCR-based cDNA subtraction and cDNA microarrays. Seven subtractive libraries consisting of ϳ9250 clones were established and enriched for tumor-specific transcripts. These clones, together with ϳ1750 additional tumor-relevant genes, were used for cDNA microarray preparation. Hybridizations were performed using a pool of 16 critical normal tissues as a reference in all experiments. In total, we analyzed 20 samples of breast cancer, 11 of LSCC, 11 of LAC, and 8 of RCC. To select for genes with low or even no expression in normal tissues, expression profiles of 22 different normal tissues were additionally analyzed. Importantly, this tissue-wide expression profiling allowed us to eliminate genes, which exhibit also high expression in normal tissues. Similarly, expression signatures of genes, which are derived from infiltrating cells of the immune system, were eliminated as well. Cluster analysis resulted in the identification of 527 expressed sequence tags specifically up-regulated in these tumors. Gene-wise hierarchical clustering of these clones clearly separated the different tumor types with RCC exhibiting the most homogenous and LAC the most diverse expression profile. In addition to already known tumor-associated genes, the majority of identified genes have not yet been brought into context with tumorigenesis such as genes involved in bone matrix mineralization (OSN, OPN, and OSF-2) in lung, breast, and kidney cancer or genes controlling Ca 2؉ homeostasis (RCN1, CALCA, S100 protein family). EGLN3, which recently has been shown to be involved in regulation of hypoxia-inducible factor, was found to be highly up-regulated in all RCCs and in half of the LSCCs analyzed. Furthermore, 42 genes, the expression level of which correlated with the overall survival of breast cancer patients, were identified. The gene dendogram clearly separates two groups of genes, those up-regulated such as cyclin B1, TGF-␤3, B-Myb, Erg2, VCAM-1, and CD44 and those down-regulated such as MIG-6, Esp15, and CAK in patients with short survival time.

SummaryA recently described splice variant of CD44 expressed in metastasizing cell lines of rat tumors, has been shown to confer metastatic potential to nonmetastasizing rat pancreatic carcinoma and sarcoma cell lines. Using antibodies raised against a bacterial fusion protein encoded by variant CD44 sequences, we have explored the expression of variant CD44 glycoproteins on human lymphoid cells and tissues and on non-Hodgkin's lymphomas. Normal lymphohematopoietic cells express barely detectable low levels of variant CD44 glycoproteins, whereas T lymphocytes, upon activation by mitogen or antigen, transiently upregulate expression of specific CD44 variant glycoproteins. The reaction pattern of various antibodies indicates that these CD44 variants contain the domain encoded by exon v6, which is part of the variant that in the rat confers metastatic capability. It is interesting that overexpression of v6 was also found in several aggressive, but not low-grade, non-Hodgkin's lymphomas.