The enzyme ornithine decarboxylase is the key regulator of the synthesis of polyamines which are essential for cell proliferation. Expression of this enzyme is transiently increased upon stimulation by growth factors, but becomes constitutively activated during cell transformation induced by carcinogens, viruses or oncogenes. To test whether ornithine decarboxylase could be a common mediator of transformation and oncogenic itself, we transfected NIH3T3 cells with expression vectors carrying the complementary DNA encoding human ornithine decarboxylase in sense and antisense orientations. The increased expression of the enzyme (50-100-times endogenous levels) induced not only cell transformation, but also anchorage-independent growth in soft agar and increased tyrosine phosphorylation of a protein of M(r) 130K. Expression of ornithine decarboxylase antisense RNA was associated with an epithelioid morphology and reduced cell proliferation. Moreover, blocking the endogenous enzyme using specific inhibitor or synthesizing antisense RNA prevented transformation of rat fibroblasts by temperature-sensitive v-src oncogene. Our results imply that the gene encoding ornithine decarboxylase is a proto-oncogene central for regulation of cell growth and transformation.

BE is strongly neovascularized not eroded. This novel concept of a molecular mechanism of the origin of BE might emphasize why precancerous BE can give rise to the more cancerous dysplasia and Barrett's adenocarcinoma stages. In addition, adenocarcinoma cells induce lymphangiogenesis. The new lymphangiogenic vessels might provide a systemic route for adenocarcinoma cells to invade circulation and induce lymph node metastasis.

Mechanisms underlying the development of oesophageal adenocarcinoma are poorly understood. To discover the role of oxidative stress and radical scavenger capacity in the malignant transformation of Barrett's oesophagus, we measured myeloperoxidase activity, superoxide dismutase activity, glutathione content and total aromatic DNA adducts. Mucosal specimens came from 52 patients in 6 groups: symptomatic gastro-oesophageal reflux disease (GORD) without and with endoscopic oesophagitis, Barrett's epithelium without and with dysplasia, adenocarcinoma in the oesophagus and controls. In the GORD-oesophagitis-metaplasia-dysplasia-adenocarcinoma sequence, glutathione content was progressively lower and myeloperoxidase activity higher than in controls, plateauing at Barrett's epithelium without dysplasia. Only in Barrett's epithelium with dysplasia was SOD activity significantly increased. In all patient groups, DNA adduct levels were significantly higher than the control level. Though these levels between patient groups did not differ significantly, the level was highest in Barrett's epithelium without dysplasia and progressively lower in Barrett's with dysplasia and adenocarcinoma. Pooled data showed a negative correlation between glutathione content and DNA adducts (؊0.28, p ‫؍‬ 0.05). Simultaneous formation of DNA adducts, increased myeloperoxidase-related oxidative stress, decreased antioxidant capacity (glutathione content) and the negative correlation between glutathione content and DNA adducts in the GORD-oesophagitis-metaplasia-dysplasiaadenocarcinoma sequence of Barrett's oesophagus indicate a role in the pathogenesis and malignant transformation related to oxidative stress.

We have found that overexpression of human ornithine decarboxylase (ODC) induces cell transformation in NIH 3T3 and Rat-1 cells (M. Auvinen, A. Paasinen, L. C. Andersson, and E. Hölttä, Nature (London) 360:355-358, 1992). The ODC-transformed cells display increased levels of tyrosine phosphorylation, in particular of a cluster of 130-kDa proteins. Here we show that one of the proteins with enhanced levels of tyrosine phosphorylation in ODC-overexpressing cells is the previously described p130 substrate of pp60v-src, known to associate also with v-Crk and designated p130CAS. We also studied the role of protein tyrosine phosphorylation in the ODC-induced cell transformation by exposing the cells to herbimycin A, a potent inhibitor of Src-family kinases, and to other inhibitors of protein tyrosine kinases. Treatment with the inhibitors reversed the phenotype of ODC-transformed cells to normal, with an organized, filamentous actin cytoskeleton. Coincidentally, the tyrosine hyperphosphorylation of p130 was markedly reduced, while the level of activity of ODC remained highly elevated. A similar reduction in pp130 phosphorylation and reversion of morphology by herbimycin A were observed in v-src- and c-Ha-ras-transformed cells. In addition, we show that expression of antisense mRNA for p130CAS resulted in reversion of the transformed phenotype of all these cell lines. An increased level of tyrosine kinase activity, not caused by c-Src or c-Abl, was further detected in the cytoplasmic fraction of ODC-transformed cells. Preliminary characteristics of this kinase are shown. These data indicate that p130CAS is involved in cell transformation by ODC, c-ras, and v-src oncogenes, raise the intriguing possibility that p130CAS may be generally required for transformation, and imply that there is at least one protein tyrosine kinase downstream of ODC that is instrumental for cell transformation.