Interferon-induced transmembrane protein 1 (IFITM1) overexpression enhances the aggressive phenotype of SUM149 inflammatory breast cancer cells in a signal transducer and activator of transcription 2 (STAT2)-dependent manner

Abstract

BackgroundInflammatory breast cancer (IBC) is a very aggressive and lethal subtype of breast cancer that accounts for about 4 % of all breast cancers diagnosed in the United States. Despite the efforts of several investigators to identify the molecular factors driving the aggressive phenotype of IBC, a great deal is still unknown about the molecular underpinnings of the disease. In the present study, we investigated the role of interferon-induced transmembrane protein 1 (IFITM1), a well-known interferon-stimulated gene (ISG), in promoting the aggressiveness of SUM149 IBC cells.MethodsWestern blot and real-time polymerase chain reaction analyses were performed to assess the protein and messenger RNA (mRNA) levels of IFITM1 and other ISGs in three IBC cell lines: SUM149, MDA-IBC-3, and SUM190. IFITM1 expression and cellular localization were assessed by using immunofluorescence, while the tumorigenic potential was assessed by performing cell migration, invasion, and colony formation assays. Small interfering RNA and short hairpin RNA knockdowns, enzyme-linked immunosorbent assays, and luciferase assays were performed to determine the functional significance of IFITM1 and signal transducers and activators of transcription 1 and 2 (STAT1/2) in SUM149 cells.ResultsWe found that IFITM1 was constitutively overexpressed at the mRNA and protein levels in triple-negative SUM149 IBC cells, but that it was not expressed in SUM190 and MDA-IBC-3 IBC cells, and that suppression of IFITM1 or blockade of the IFNα signaling pathway significantly reduced the aggressive phenotype of SUM149 cells. Additionally, we found that knockdown of STAT2 abolished IFITM1 expression and IFITM1 promoter activity in SUM149 cells and that loss of STAT2 significantly inhibited the ability of SUM149 cells to proliferate, migrate, invade, and form 2-D colonies. Notably, we found that STAT2-mediated activation of IFITM1 was particularly dependent on the chromatin remodeler brahma-related gene 1 (BRG1), which was significantly elevated in SUM149 cells compared with SUM190 and MDA-IBC-3 cells.ConclusionsThese findings indicate that overexpression of IFITM1 enhances the aggressive phenotype of triple-negative SUM149 IBC cells and that this effect is dependent on STAT2/BRG1 interaction. Further studies are necessary to explore the potential of IFITM1 as a novel therapeutic target and prognostic marker for some subtypes of IBCs.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-016-0683-7) contains supplementary material, which is available to authorized users.

IFITM1 suppression blocks proliferation and invasion of aromatase inhibitor-resistant breast cancer in vivo by JAK/STAT-mediated induction of p21

“…We used the mammary intraductal (MIND) model of breast cancer to investigate the effect of reduced IFITM1 expression on AI-resistant tumor cell invasion in vivo (Figure 3A) [14, 53]. After three weeks of Dox exposure, we confirmed that the MIND model was able to accurately assess tumor cell invasion out of the mammary duct using immunofluorescent staining (Figure 3B).…”

“…[53] For analysis of IFITM1 promoter activity, the pGL3 plasmid with the first 750 nucleotides of the IFITM1 promoter inserted (pGL3-IFITM1 [−750/−1]), was used. [53] The pGL3-Basic-IRES was a kind gift from Joshua Mendell (Addgene #64784) [8]. For analysis of p21 promoter activity, the pGL2-p21 promoter-Luc plasmid was used, which as a kind gift from Martin Walsh (Addgene #33021).…”

“…Notably, we have identified interferon induced transmembrane protein 1 (IFITM1) as a critical downstream target of the IFN signaling pathway and have found that it is overexpressed in AI-resistant breast cancer cells and AI-resistant patient tumors [14, 53]. IFITM1 is a 17-kDa transmembrane protein coded on the short arm of chromosome 11 [66].…”

“…ISGs are induced by type 1 IFN signaling through the type 1 IFN(α/β) receptor (IFNAR), which stimulates JAK/STAT activation and transcription [5, 23, 57]. We have shown that IFITM1-expressing breast cancer cells produce type 1 IFNs and stimulate IFITM1 production in an autocrine manner, but outside of DNA damage resistance, little is understood about the mechanism by which IFITM1 influences the breast cancer cell phenotype [14, 53]. …”

Combination of IFITM1 knockdown and radiotherapy inhibits the growth of oral cancer

“…After STAT is phosphorylated, it undergoes polymerization to become an activated transcriptional activator in the form of a homodimer or heterodimer which enters the nucleus to bind to specific sites in the target gene promoter sequence, facilitating its transcription. Meanwhile, in the literature, a close relationship between IFITM1 and STAT1/2/3/p21 is demonstrated . Changes in various proteins were measured using STAT1/2/3/p21 total protein antibody and its phosphorylation antibody, respectively, to observe the STAT1/2/3/p21 expression after inhibiting IFITM1 expression in drug‐resistant oral neoplasm.…”