Rose Winkler

Different mechanisms are implicated in ERBB2 gene overexpression in breast and in other cancers.

The ERBB2 gene is overexpressed in 30% of breast cancers and this has been correlated with poor prognosis. ERBB2 is upregulated in other cancers such as prostate, pancreas, colon and ovary. In breast cancer cells, the mechanisms leading to ERBB2 gene overexpression are increased transcription and gene amplification. In these cancers, AP-2 transcription factors are involved in ERBB2 overexpression, and AP-2 levels are correlated with p185c-erbB-2 levels. In this work, we wanted to know if the same molecular mechanisms are responsible for the ERBB2 upregulation in non-breast cancers. We compared ERBB2 gene copy number, p185c-erbB-2 and mRNA levels with AP-2 levels in several ovary, prostate, colon and pancreas cancer cells. A moderate expression of erbB-2 mRNA and protein were observed in some cells without gene amplification. In contrast to breast cancer cells, AP-2 factors were absent or low in some non-breast cells which did express ERBB2. It is thus likely that AP-2 is not a major player in the increased levels of erbB-2 transcripts in non-breast cancer cells. The transcriptional activity of the ERBB2 promoter in colon and ovary cancer cells was estimated using reporter vectors. The results showed that the promoter regions involved in ERBB2 gene overexpression in breast cancer cells are different from those that lead to the gene upregulation in colon and ovary cancers. In conclusion, our results indicate that different transcriptional and post-transcriptional mechanisms are responsible for the increased levels of erbB-2 transcript and protein in breast and non-breast cancer cells.

Characterization of the Insulin-Like Growth Factor Axis in the Human Thymus

The components of the insulin‐like growth factor (IGF) axis have been investigated in the normal human thymus. Using ribonuclease protection assays (RPA), IGF‐II transcripts were detected in the normal human thymus. By reverse transcriptase polymerase chain reaction (RT‐PCR) analyses, promoters P3 and P4 were found to be active in the transcription of IGF2 gene within human thymic epithelial cells (TEC). No IGF‐II mRNA could be detected in human lymphoid Jurkat T cells with 30 cycles of RT‐PCR. By Northern blot analyses, IGFBP‐2 to ‐6 (but not IGFBP‐1) were found to be expressed in TEC with a predominance of IGFBP‐4. Interestingly, Jurkat T cells only express IGFBP‐2 but at high levels. The type 1 IGF receptor was detected in Jurkat T cells but not in human TEC. The identification of the components of the IGF axis within separate compartments of the human thymus adds further evidence for a role of this axis in the control of T‐cell development. The precise influence of thymic IGF axis upon T‐cell differentiation and immunological self‐tolerance however needs to be further investigated.

The IGF system in in-vitro human decidualization

Decidualization of endometrial stromal cells (ESCs) is critical for a successful pregnancy but the molecular mechanisms of the process are poorly understood. In this study, we investigated whether the insulin-like growth factor (IGF) network is involved in this cellular process. Expression kinetics of members of the IGF system was examined at both mRNA and protein levels during in-vitro decidualization of cultured human ESCs. We found a significant up-regulation of IGF-II as well as of IGF-I receptor and the A and B insulin receptor (InsR) isoforms. In addition, levels of the key adaptor proteins insulin receptor substrate 1 (IRS-1) and IRS-2 increased, suggesting a potential involvement of the IGF signalling pathway in the decidualization process. Expression of two IGF binding proteins, IGFBP-1 and IGFBP-4, which can inhibit IGF action, also increased. In order to determine whether IGF signalling was activated during decidualization, the phosphorylation status of the receptors and the adaptor proteins was estimated. Only IRS-2 was slightly phosphorylated in decidualized cells and was further activated by the addition of exogenous IGF-II. These results suggest that the IGF signalling pathway could play a crucial role in the functions of decidualized endometrial cells.

Altered expression of type I insulin-like growth factor receptor in Crohn's disease

The fibrotic and antiapoptotic effects of insulin‐like growth factors (IGF) are mediated by type I IGF receptor (IGF‐1R). IGFs could play a role in intestinal stricturing and in the maintenance of inflammation in Crohns disease (CD). We aimed to describe IGF‐1R expression in CD intestinal lesions, to compare it to other intestinal inflammatory diseases and to correlate it with fibrosis and apoptosis. IGF‐1R expression and apoptosis (active caspase‐3) were studied by immunohistochemistry. Surgical intestinal specimens [17 CD, nine controls, six diverticulitis and four ulcerative colitis (UC)] were used. IGF‐1R was expressed transmurally mainly by inflammatory cells (IC) and smooth muscle cells, both in diseased intestine and controls. IGF‐1R positive IC were increased in the mucosa and the submucosa of CD (P < 0·007), and in involved areas compared to uninvolved areas (P = 0·03). In UC, the number of IGF‐1R positive IC was only increased in the mucosa, and was not different from controls in the submucosa. In diverticulitis, the number of IGF‐1R positive IC did not differ from controls. In CD submucosa, IGF‐1R expression in IC was inversely correlated with apoptosis in uninvolved areas (P = 0·01). Expression of IGF‐1R in submucosal fibroblast‐like cells, subserosal adipocytes and hypertrophic nervous plexi was specific for CD. We have shown a transmural altered expression of IGF‐1R in CD. This may suggest a role for IGF‐1R in the maintenance of chronic inflammation and stricture formation in CD.