J Virol. unique heterodimeric receptor complex consisting of IFN- receptor 1 and the IL-10 receptor subunit 2 . However, unlike the receptors for type I IFNs, which are broadly expressed on virtually all cell types, IFN-III receptors exhibit a more restricted tissue distribution [6, 10]. Because of the use of distinct receptors, types I and III IFNs likely do not signal identical biological outcomes in anti-viral and anti-cancer activities . The activity of IFN- is highly prominent in barrier epithelia compared with other cell types . In addition IFN- has lower toxicity than IFN- . Interestingly IFN- has been recently shown to exert antitumor effects in both murine and human models. This has been shown to occur through direct effects on target tumor cells as well as through indirect-immune-mediated responses [13, 14]. Recently human intestinal enteroids (HIEs) that exhibit a similar cellular composition to Defactinib hydrochloride the intestinal epithelium have been established, and used to study viral epithelial interactions . Using this model system Saxena have shown that rotavirus infection of human intestinal epithelial cells induces type III IFN as the dominant transcriptional response over type 1 IFN . Such a conclusion was also reached by Pervolaraki  who state that type III IFN is the frontline of antiviral response in the human gut. Interestingly viroplasm-free dsRNA is present in the cytoplasm of rotavirus-infected cells and is a key intermediate in the replication cycle of many viruses, including other major human enteric viral pathogens [16, 18]. In this context, it is worth noting that the type III IFN response to rotavirus was also obtained using the dsRNA analog poly-IC . Finally, it can be speculated that Defactinib hydrochloride human intestinal epithelial cells are programmed to respond to viral dsRNA with type III IFN . Other experiments have shown that the dsRNA analog poly-IC induces crypt cell death in murine enteroids . In the same way poly-IC Defactinib hydrochloride administered to mice induced intestinal epithelial cell death HSP70-1 within a few hours (3 to 6 h) . Apoptotic deletion of infected epithelial cells translates into pathological cell shedding . Taken together, these findings Defactinib hydrochloride strongly suggest that the dsRNA analog poly-IC is able to trigger a dual effect in normal intestinal cells, i.e. an immunoadjuvant effect represented by IFN- production and epithelial cell shedding. In this context, we hypothesized that human gastrointestinal carcinoma cells could maintain these dual functions upon intracellular treatment by the dsRNA analog poly-IC. Our aim was twofold: i) determine concomitantly both IFN- secretion and cell proliferation/shedding upon poly-IC treatment in several human gastrointestinal carcinoma cell lines; and ii) evaluate whether these two parameters are connected via a common pathway using NFB signaling as a probe. RESULTS Intracellular poly-IC induces IFN- production in human gastrointestinal cancer cell lines As shown in Figure ?Figure1A,1A, T84 cancer cells exposed intracellularly to Poly-IC produced huge amounts of IFN- in a time-dependent manner. The kinetics of IFN- production shows two phases: a steep rise in IFN- accumulation in the medium, significant at time point 6 h, peaking at 72 h and followed by a plateau up to 96 h. In addition, IFN- production was almost undetectable when T84 cells were treated with extracellular poly-IC for 72 h (Figure ?(Figure1B1B). Open in a separate window Figure 1 Intracellular Poly-IC elicits IFN- production in gastrointestinal cancer cell lines as measured by ELISA in culture supernatants(A) Time-dependent effect of intracellular Poly-IC on T84 cells. Proliferating T84 cells, maintained in 6-well plates, were treated for the indicated time points with 0.64 g/ml poly-IC in presence of Dharmafect (intracellular Poly-IC). Each symbol represents the mean sem of 3 experiments performed in triplicate. (B) T84 cells were incubated with extracellular (extra) or intracellular (intra) poly-IC (0.64 g/ml) for 72 h, or with medium (control) or vehicle alone (Dharm). Mean sem of 3 experiments performed in triplicate. (poly-IC intra vs Dharm: < 0.0001; poly-IC extra vs control: NS). (C) Gastrointestinal cell lines or Jurkat cells were treated with intracellular Poly-IC for 72 h. Mean sem of 3 experiments performed in triplicate. We then determined the kinetics of committment to IFN- production. To this end, a variable exposure time to poly-IC (3 h, 6 h, 9 h) was followed by replacement of the poly-IC-containing medium by fresh medium. The read-out of results was the determination of IFN- concentration at time point 72 h. These experiments showed that an exposure time of 3 h to.