The c-Kit receptor belongs to type III tyrosine kinase receptor, which consists of an extracellular ligand binding domain and an intracellular kinase domain. In the kinase domain, the ATP binding site is separated from the phosphotransferase site by an interkinase sequence required for interaction with signal transduction proteins involved in the c-Kit pathway. 1 The c-Kit receptor is expressed in a wide variety of normal and neoplastic tissues. A positive correlation between misregulation of the c-kit gene and malignant transformation of cells has been reported. 2,3 For instance, substitution mutations in exon 11 of the gene, changing amino acids of the juxtamembrane region of the receptor, are associated with gastrointestinal stromal tumors, whereas mutations in exon 17 that substitute Asp816, just downstream of the tyrosine kinase signature, are associated with myeloid leukemias and testicular seminomas. 2,3 These mutations induce ligand-independent dimerization or autophosphorylation of the receptor and they cause constitutive activation of downstream signaling pathways. Moreover, overexpression of c-Kit and its ligand SCF occurs in several tumors and they probably stimulate proliferation in an autocrine or paracrine manner. 2 Recently, c-kit expression in various tumors has been revisited because this receptor is a target of the anti-cancer activity of a well described tyrosine kinase inhibitor: imatinib (STI1571). 2,4 Beside mutations affecting the activity of the full-length c-Kit, expression of an alternative transcript of human c-kit has been described in several transformed cell lines. The
Background and aims: The proto-oncogene c-KIT encodes a tyrosine kinase receptor essential during embryonic development and postnatal life. Although deregulated expression of c-KIT has been reported, its role in colorectal carcinoma remains controversial: some authors have described a correlation between c-KIT expression and colorectal cancer (CRC), while others have failed to detect the receptor in the majority of neoplasia examined. To address this question, we designed a prospective study to analyze the expression of c-KIT in normal and neoplastic colonic mucosa of the same patient. Patients and methods: We analyzed the tissues of 20 patients undergoing surgical resection for colorectal carcinoma by reverse transcriptase-polymerase chain reaction, Western blot and immunohistochemistry, whose results were correlated with histopathological parameters. Results: Most patients (90%) showed c-KIT expression in normal tissue both at RNA and protein level, while in neoplastic tissue it was observed in 30% of patients at RNA level and in 10% at protein level. By immunohistochemistry the localization of c-KIT protein in the normal colon was restricted to interstitial cells scattered in the stroma, whereas the non-neoplastic epithelium was always negative. The mucinous carcinomas were all c-KIT negative, whereas the only case in which c-KIT was displayed in the neoplastic epithelium was a G3 adenocarcinoma. Conclusion: Most colorectal carcinomas do not express c-KIT. We suggest that c-KIT expression is rarely present in this neoplasia; thus, the use of receptor inhibitors should be conducted in selected sub-groups of colon carcinoma patients, subsequent to the clear demonstration of c-KIT overexpression in the neoplastic cells.
This article reports the HIV epitope specificity of antibodies present in the sera of HIV-negative patients with autoimmune diseases. Recombinant gp120 and a panel of synthetic peptides derived from the amino acid consensus sequences of either related (gp120, gp41, and p24) or unrelated (Mage-1, necdin, heat shock protein [65 kDa], and amyloid) HIV proteins were tested by a specific ELISA. The first set of experiments performed on four patients with Sjögren's syndrome (SjS) and four patients with systemic lupus erythematosus (SLE) revealed a significant anti-gp120 antibody reactivity in autoimmune patients when compared to healthy HIV-negative controls. Moreover, such binding could be almost completely inhibited by preincubation with free gp120. A significant anti-p24 reactivity was observed in 18 of 29 sera from SjS patients and in 13 of 25 sera from SLE patients, while anti-gp41 was observed only in 3 of 14 SjS and in 2 of 20 SLE-affected patients. Similar analyses were performed in the murine model of autoimmunity, showing that sera from MRL/lpr mice were able to bind all HIV-related peptides in an age-dependent manner. The analysis of a panel of HIV-unrelated peptides showed that SLE as well as MRL/lpr sera bind both HIV-related and unrelated peptides, while SjS sera failed to do so, revealing the polyclonal nature of the SLE and MRL/lpr repertoire and the oligoclonal reactivity of SjS sera. This is also supported by inhibition experiments, which showed that SLE, but not SjS, sera competitively inhibited the binding to HIV gp120 peptide of sera from autoimmune MRL/lpr mice. These results indicate that an overlapping polyclonal repertoire is present in both SLE and MRL/lpr sera, while the oligoclonal specificity of SjS antibodies may be related to a specific, nonpolyclonal, activation against putative retroviral antigens.
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