Angiotensin stimulates the expression of interferon-inducible genes in H295R cells

IFITM protein regulation and functions: Far beyond the fight against viruses

Interferons (IFNs) are important cytokines that regulate immune responses through the activation of hundreds of genes, including interferon-induced transmembrane proteins (IFITMs). This evolutionarily conserved protein family includes five functionally active homologs in humans. Despite the high sequence homology, IFITMs vary in expression, subcellular localization and function. The initially described adhesive and antiproliferative or pro-oncogenic functions of IFITM proteins were diluted by the discovery of their antiviral properties. The large set of viruses that is inhibited by these proteins is constantly expanding, as are the possible mechanisms of action. In addition to their beneficial antiviral effects, IFITM proteins are often upregulated in a broad spectrum of cancers. IFITM proteins have been linked to most hallmarks of cancer, including tumor cell proliferation, therapeutic resistance, angiogenesis, invasion, and metastasis. Recent studies have described the involvement of IFITM proteins in antitumor immunity. This review summarizes various levels of IFITM protein regulation and the physiological and pathological functions of these proteins, with an emphasis on tumorigenesis and antitumor immunity.

The human 1-8D gene (IFITM2) is a novel p53 independent pro-apoptotic gene

The human 1-8 interferon inducible gene family consists of at least 3 functional genes; 9-27, 1-8D and 1-8U, which are all linked on an 18-kb fragment of chromosome 11 and are highly homologous. It has recently been shown by us and others that the 1-8D gene is overexpressed in colon carcinoma. Here, we show, by sequence comparison of the 1-8D in pairs of tumor/normal colon tissues, the existence of 6 different alleles, containing single-nucleotide polymorphisms with no mutations. Transformation assays revealed a possible role for the 1-8D gene as a transformation inhibitor. Further, transient expression of the human 1-8D gene in multiple mammalian cell lines showed accumulation of cells in the G1 phase followed by elevation in the subG1 phase. SubG1 elevation was confirmed as apoptosis by Annexin-V binding assays and transferase-mediated dUTP nick end labeling assays. Moreover, knock-down of 1-8D provided partial protection from Etoposide and UV-induced apoptosis. The induction of apoptosis by 1-8D is dependent on caspase activities but not on p53 expression. Although 1-8D induces apoptosis independently of p53, p53 expression downregulates 1-8D protein expression. Our data suggest a role for the 1-8D gene as a novel pro-apoptotic gene that will provide new insights into the regulated cellular pathways to death.

'1-8 interferon inducible gene family': putative colon carcinoma-associated antigens

D^b−/−xβ2 microglobulin (β2m) null mice transgenic for a chimeric HLA-A2.1/D^b-β2m single chain (HHD mice) are an effective biological tool to evaluate the antitumour cytotoxic T-lymphocyte response of known major histocompatibility-restricted peptide tumour-associated antigens, and to screen for putative unknown novel peptides. We utilised HHD lymphocytes to identify immunodominant epitopes of colon carcinoma overexpressed genes. We screened with HHD-derived lymphocytes over 500 HLA-A2.1-restricted peptides derived from colon carcinoma overexpressed genes. This procedure culminated in the identification of seven immunogenic peptides, three of these were derived from the ‘human 1-8D gene from interferon inducible gene’ (1-8D). The 1-8D gene was shown to be overexpressed in fresh tumour samples. The three 1-8D peptides were both antigenic and immunogenic in the HHD mice. The peptides induce cytotoxic T lymphocytes that were able to kill a colon carcinoma cell line HCT/HHD, in vitro and retard its growth in vivo. One of the peptides shared by all the 1-8 gene family primed efficiently normal human cytotoxic T lymphocyte precursors. These results highlight the 1-8D gene and its homologues as putative immunodominant tumour-associated antigens of colon carcinoma.

Interferon-inducible genes in the rat adrenal gland and vascular smooth muscle cells

Chronic stimulation of the renin-angiotensin system results in increased zona glomerulosa cells and in cells expressing the final enzyme in the synthesis of aldosterone, the cytochrome P-450 aldosterone synthase. The genes activated during adrenal remodeling are not well defined. We have reported that the expression of interferon-inducible genes, 9-27, 1-8D and 1-8U in H295R cells is stimulated by A-II. The 9-27 gene is expressed mainly in leukocytes and is associated with cell proliferation. In this study, we searched for similar genes in a rat zona glomerulosa cDNA library, and examined the regulation of the expression of these genes. We found the Rat8 gene, which has been reported to be similar to human interferon-inducible genes, as well as two similar genes, No. 10 (1096 bp), and No. 16 (630 bp). Rat8 gene and No. 16 were mainly expressed in zona glomerulosa. The product of No. 10 is thought to be a secreted protein, unlike those of 8 and 16, and its expression in the adrenal was weak in comparison. The control of the expression of rat8 or No. 16 genes differs depending on the tissue. Expression in A10 cells (derived from rat embryo thoracic aorta) was not stimulated by A-II, nor was it influenced by salt intake in the adrenal gland, but it was reduced in vascular smooth muscle cells (VSMC) of rats on a low sodium diet. These results show that genes similar to the human 1-8 gene family are expressed in rat adrenal glomerulosa cells and VSMC, but their expression is not regulated by A-II. The function of these genes in VSMC and adrenal is unknown.