Merja Auvinen

Incipient Angiogenesis in Barrett’s Epithelium and Lymphangiogenesis in Barrett’s Adenocarcinoma

PURPOSE Barretts esophagus (BE), a precancerous condition for Barretts adenocarcinoma, is classically characterized by flames of salmon-colored mucosa extending into normal pale esophageal mucosa. This flaming is thought to be a consequence of continuous erosis of mucosa caused by chronic reflux. Another characteristic feature of Barretts adenocarcinoma patients is the frequent development of lymph node metastases. We addressed whether onset of angiogenesis occurs in BE and if the lymphatic system might provide a route for Barretts adenocarcinoma cells to infiltrate regular lymph nodes. PATIENTS AND METHODS Fifteen surgically resected Barretts dysplasia or adenocarcinoma patients were included. Immunohistochemistry and a modified whole mount analysis were used. RESULTS The incipient angiogenesis originates from the pre-existing vascular network in the lamina propria and infiltrates Barretts epithelium, giving its ominous salmon-red color. Barretts epithelium-specific goblet cells express vascular endothelial growth factor (VEGF)-A. The immature blood vessels show a relative absence of smooth muscle actin (SMA)-positive mural cells and express VEGF receptor (VEGFR)-2 and matrix metalloproteinase (MMP)-9 on their exterior. Coexpression of VEGF-C and its receptor VEGFR-3 on lymphatic vessels is demonstrated. CONCLUSION 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 Barretts 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.

Oxidative stress has a role in malignant transformation in Barrett's oesophagus

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 Barretts 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, Barretts 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 Barretts epithelium without dysplasia. Only in Barretts 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 Barretts epithelium without dysplasia and progressively lower in Barretts 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–dysplasia–adenocarcinoma sequence of Barretts oesophagus indicate a role in the pathogenesis and malignant transformation related to oxidative stress.

ORNITHINE DECARBOXYLASE- AND RAS-INDUCED CELL TRANSFORMATIONS : REVERSAL BY PROTEIN TYROSINE KINASE INHIBITORS AND ROLE OF PP130CAS

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.