Escape from immune recognition has been hypothesized to be a factor in carcinogenesis. It may be mediated for many cancers through down-regulation in the MHC class 1 antigen processing and presentation pathway. TAP-1, TAP-2, tightly linked to LMP-2 and LMP-7 are multiple components of the endogenous, antigen presentation pathway machinery. We addressed the question of alterations in this pathway in human Glioblastoma (HGB) and of its relationship to modulation in expression of IGF-1 that is highly expressed in this cancer. Deficiencies in expression of TAP-1 were demonstrated by RT-PCR and/or by immuno-flow cytometry in the HGB cell line T98G obtained from ATCC, and in 3 of 4 human cell lines established from patients with Glioblastoma Multiforme. Deficiencies in expression of TAP-2 were observed in 3 of 4, deficiencies in expression of LMP-2 in 4 of 4 and deficiencies in LMP-7 in 3 of 4 HGB cell lines examined by RT-PCR and Western blot. Following down-regulation of IGF-1 by transfection with the pAnti IGF-1 vector that expresses IGF-1 RNA in antisense orientation, or by the exogenous addition of IGF-1 receptor monoclonal antibody to cell culture media, the deficiencies in components of the MHC-1 antigen presentation pathway were up-regulated and/or rescued in all HGB cell lines tested. Moreover, this up-regulation in expression was aborted by addition of 100 ng/ml of IGF-1 to the culture media. Unlike in the case of IFN-γ, the restoration of TAP-1 and LMP-2 by down-regulation of IGF-1 in Glioblastoma cells was not correlated to the tyrosine phosphorylation of STAT 1. In summary, the simultaneous reversion in expression of the multiple constituents of MHC-1 antigen processing path and up-regulation in expression of MHC-1 occurring with down-regulation in IGF-1 may have a role in reinforcement of immunity against tumor antigen(s) in some animal cancers and in humans with Glioblastoma Multiforme.
Abstract The stability of several RNA transcripts in cultured hepatocytes is known to increase when serum is omitted from the culture medium. In order to investigate possible mechanisms for this phenomenon, we examined the effects of actinomycin D and cycloheximide on the levels of actin, albumin, and insulin‐like growth factor I transcripts in primary cultures incubated in serumfree medium. The levels of IGF‐I and albumin transcripts per culture increased for the first 4 hours following addition of actinomycin D and then declined. The levels of actin transcripts and total RNA per culture declined immediately following actinomycin D addition in a manner consistent with exponential decay. IGF‐I and albumin transcript levels were relatively unaffected by cycloheximide, while actin transcript levels increased 7‐fold over 7 hours. The half‐lives of actin transcripts and total RNA were calculated to be 4.6 to 7.7 hours and 11 to 19 hours, respectively, with no statistically significant correlation with hormone treatment. The data suggest that the stability of albumin and IGF‐I transcripts, but not actin transcripts, is controlled in part by an actinomycin D‐sensitive process.
UNLABELLED Antisense techniques that inhibit intracellular expression of insulin-like growth factor-I (IGF-I) were efficient in gene therapy of some tumor diseases. IGF-I in the airways is considered to induce lung fibrosis in interstitial lung diseases, inhibit apoptosis of epithelial cells and participate in local carcinogenesis. AIM OF THE STUDY The aim of the study was--by examining the IGF-I expression in the lower airways--to evaluate preliminary the efficacy of anti-IGF-I antisense technicques in the treatment of airways diseases. MATERIAL AND METHODS The IGF-I expression was examined in the reverse transcriptase--polimerase chain reaction (RT-PCR) applied to A549 human cell line, that is representative for lower airway epithelium and exemplifies the model of bronchioloalveolar adenocarcinoma. IGF-I expression in non-neoplastic lower airways cells was assessed by immunocytochemical staining (anti-IGF-I) in cytological materials originating from bronchoalveolar lavage (BAL) of sarcoidosis and asbestosis patients and in individuals free of lung pathology. RESULTS The IGF-I expression was detected in A549 cells with use of RT-PCR method (3 independent probes). In BAL cytological specimens the appearance of IGF-I was found, mainly in alveolar macrophages (62 +/- 6, 5 in sarcoidosis vs. 36 +/- 6 in controls, p=0,09), as well as in BAL lymphocytes. CONCLUSIONS Summing up, the antisense technicques, blocking the intracellular IGF-I expression may be potentially useful in treatment of selected lower airways, both tumor (non-small cell lung carcinoma) and non-tumor (ILD complicated with lung fibrosis) conditions.
The insulin-like growth factor-I (IGF-I) gene was analyzed in a population of children with growth disorders presenting normal GH and low IGF-I. We thus tried to detect any mutation in the IGF-I gene that could be responsible for short stature in children, using PCR, single-strand conformation polymorphism (SSCP) analysis, followed by DNA cloning and sequencing. We demonstrated in all examined children significant changes in the promoter region of the IGF-I gene (P1 IGF-I). Nucleotide sequence changes, such as CC-->GT and A-->G, and their localization are described. The results obtained excluded mutations in the coding sequence of the IGF-I gene. We conclude that testing the IGF-I P1 region, using PCR/SSCP analysis, could be useful in the diagnosis of growth disorders.
IGF-I, insulin-like growth factor 1, is present in normal fetal/neonatal brain development and reappears in the mature brain participating in the development of malignant tumor, glioblastoma multiforme. Targeting the IGF-I system has emerged as a useful method to reduce glial malignant development. Downregulation in the expression of IGF-I using antigene anti-IGF-I technology (antisense, AS, and triple helix, TH) applied in glioma cell culture established from glioblastoma biopsies induces the expression of B7 and MHC-I antigens in transfected cells (immunogenicity). The transfected cancer cells, "vaccines," after subcutaneous injection, initiated an immune response mediated by T CD8+ lymphocytes, followed by tumor regression (immunotherapy). The median survival of patients treated by surgery followed by radiotherapy and immunotherapy was 21–24 months. On the other side, the experimental work has demonstrated that IGF-I AS or TH transfected tumor cells fused with activated dendritic cells, DC, showing more striking immunogenic character. Using IGF-I TH/DC "vaccination," the efficiency in suppressing rat glioma tumors is not only relatively higher than that obtained using IGF-I TH cells but is also more rapid.
