We demonstrate that CD161 is a highly up-regulated gene in human interleukin

Conclusion. These findings suggest that a shifting of CD4؉CD161؉ T cells from Th17 to the Th17/Th1 or Th1 phenotype can occur in the SF of children with oligoarticular-onset JIA, and indicate that the accumulation of these cells is correlated with parameters of inflammation. Thus, the results support the hypothesis that these cells may play a role in JIA disease activity.

SummaryThe epidermal growth factor receptor (EGFR) is a transmembrane tyrosine kinase receptor involved in the proliferation and survival of cancer cells. EGFR is the first molecular target against which monoclonal antibodies (mAb) have been developed for cancer therapy. Here we review the mechanisms underlying the effects of EGFR-specific mAb in cancer therapy. The efficacy of EGFR-specific mAb in cancer occurs thanks to inhibition of EGFRgenerated signalling; furthermore, the effects of antibodies on the immune system seem to play an important role in determining the overall anti-tumour response. In this review, attention is focused on cetuximab and panitumumab, two mAb introduced recently into clinical practice for treatment of metastatic colorectal and head and neck cancer which target the external part of EGFR.

Purpose: Although cetuximab, an anti-EGF receptor (EGFR) monoclonal antibody, is an effective treatment for patients with KRAS wild-type metastatic colorectal cancer (mCRC), its clinical use is limited by onset of resistance.Experimental Design: We characterized two colorectal cancer models to study the mechanisms of acquired resistance to cetuximab.Results: Following chronic treatment of nude mice bearing cetuximab-sensitive human GEO colon xenografts, cetuximab-resistant GEO (GEO-CR) cells were obtained. In GEO-CR cells, proliferation and survival signals were constitutively active despite EGFR inhibition by cetuximab treatment. Whole gene expression profiling identified a series of genes involved in the hepatocyte growth factor (HGF)-MET-dependent pathways, whichwere upregulated in GEO-CR cells.Furthermore,activated, phosphorylated MET was detected in GEO-CR cells. A second colorectal cancer cell line with acquired resistance to cetuximab was obtained (SW48-CR). Inhibition of MET expression by siRNA restored cetuximab sensitivity in GEO-CR and SW48-CR cells, whereas exogenousactivation ofMETbyHGFstimulationin cetuximab-sensitiveGEOandSW48cells inducedresistance to cetuximab. Treatment of GEO-CR and SW48-CR cells with PHA665752, a selective MET inhibitor, inhibited cell growth, proliferation, and survival signals and impaired cancer cell migration. Overexpression of TGF-a, a specific EGFR ligand, was involved in the acquisition of cetuximab resistance in GEO-CR and SW48-CR cells. In fact, TGF-a overexpression induced the EGFR-MET interaction, with subsequent MET phosphorylation and activation of MET downstream effectors in GEO-CR and SW48-CR cells.Conclusions: These results suggest that overexpression of TGF-a through induction of EGFR-MET interaction contributes to cetuximab resistance in colorectal cancer cells. The combined inhibition of EGFR and MET receptor could represent a strategy for preventing and/or overcoming cetuximab resistance in patients with colorectal cancer.

The reason why CD4(+) T helper 17 (Th17) cells, despite their well-known pathogenic role in chronic inflammatory disorders, are very rare in the inflammatory sites remains unclear. We demonstrate that human Th17 cells exhibit low ability to proliferate and to produce the T cell growth factor interleukin-2 (IL-2), in response to combined CD3 and CD28 stimulation. This was due to the upregulated expression of IL-4-induced gene 1 (IL4I1) mRNA, a secreted L-phenylalanine oxidase, which associated with a decrease in CD3ζ chain expression and consequent abnormalities in the molecular pathway that allows IL-2 production and cell proliferation. High IL4I1 mRNA expression was detectable in Th17 cell precursors and was strictly dependent on Th17 cell master gene, the retinoid acid related orphan receptor (RORC). Th17 cells also exhibited RORC-dependent CD28 hyperexpression and the ability to produce IL-17A after CD28 stimulation without CD3 triggering. Our findings suggest that the rarity of human Th17 cells in inflamed tissues results from RORC-dependent mechanisms limiting their expansion.

T helper17 (Th17) lymphocytes represent a third arm of the CD4+ T-cell effector responses, in addition to Th1 and Th2 cells. Th17 cells have been found to exhibit high plasticity because they rapidly shift into the Th1 phenotype in inflammatory sites. In humans, Keywords: CD161 r IL4I1 r RORC r Th17 Th1 cells derived from Th17 cells express CD161, whereas classic Th1 cells do not; these Th17-derived Th1 cells have been termed nonclassic Th1 cells. In this study, we examined similarities and differences between classic and nonclassic human Th1 cells by assessing a panel of T-cell clones, as well as CD161Introduction CD4 + T helper (Th) cells can be classified into lineages on the basis of cytokine production, the expression of specific transcription factors, and the immunological function they mediate: Th1 cells, which express the transcription factor T-box expressed in T cells (T-bet) and secrete IFN-γ, protect the host against intracellular infections; Th2 cells, which express GATA-3 and secrete IL-4, IL-5, and IL-13, mediate host defense against helminths [1,2]. Recently, additional subsets that preferentially produce distinct cytokines Correspondence: Prof. Francesco Annunziato e-mail: f.annunziato@dmi.unifi.it have been described. The most studied subset includes cells that selectively produce IL-17A (Th17 cells), express the transcription factor RAR-related orphan receptor (ROR)γt, and protect the host against infection with extracellular pathogens [3,4]. Human Th17 cells are, at least partially, different from murine Th17 cells [5,6]. Indeed, human Th17 cells express not only distinctive Th17 molecules, such as IL-23 receptor (IL-23R) and RORC, but also those typical of the Th1 phenotype such as IL-12Rβ2 and T-bet [6]. Moreover, we have previously discovered a subset of human Th17 cells that are also able to produce IFN-γ, named Th17/Th1 * These authors contributed equally to this work. To investigate the main features of these two different Th1 subsets, CD4+ CD161 + and CD4 + CD161 − T-cell populations were purified from peripheral blood (PB) of healthy human subjects and then cloned under limiting dilution conditions. As expected, clones derived from the CD4 + CD161 + T-cell fraction exhibited a Th17, a Th17/Th1, or a Th1 phenotype, whereas virtually all clones generated from the CD4 + CD161 − T-cell subset had a Th1 phenotype and none of them was able to produce IL-17A ( Fig. 1A and B). CD161 − Th1 clones were considered as classic Th1 cells, whereas CD161 + Th1 cells were considered as nonclassic (Th17-derived) cells. Transcription factorsThe expression of the transcription factors T-bet and RORC by classic and nonclassic Th1, as well as by Th17 or Th17/Th1, cells were compared by assessing 20 randomly selected T-cell clones from each phenotype with quantitative RT-PCR. In agreement with previously published data [15,16], the Th1-related transcription factor T-bet was found to be expressed by all four types of T-cell clones analyzed, reaching the highest mRNA levels in both classic and nonclassic-Th1 c...

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Human Th17 clones and circulating Th17 cells showed lower susceptibility to the antiproliferative effect of TGF-b than Th1 and Th2 clones or circulating Th1-oriented T cells, respectively. Accordingly, human Th17 cells exhibited lower expression of clusterin, and higher Bcl-2 expression and reduced apoptosis in the presence of TGF-b, in comparison with Th1 cells. Umbilical cord blood naïve CD161 + CD4 + T cells, which contain the precursors of human Th17 cells, differentiated into IL-17A-producing cells only in response to IL-1b plus IL-23, even in serum-free cultures. TGF-b had no effect on constitutive RORct expression by umbilical cord blood CD161 + T cells but it increased the relative proportions of CD161 + T cells differentiating into Th17 cells in response to IL-1b plus IL-23, whereas under the same conditions it inhibited both T-bet expression and Th1 development. These data suggest that TGF-b is not critical for the differentiation of human Th17 cells, but indirectly favors their expansion because Th17 cells are poorly susceptible to its suppressive effects.Key words: CD161 . RORct . TGF-b Á Th17 IntroductionThe role of TGF-b in the differentiation and function of human Th17 cells is still controversial. Although many authors agree that murine Th17 cells originate from naïve CD4 + T cells in the presence of IL-6 and TGF-b, and their development is then stabilized and/or amplified by , several studies have denied the role of TGF-b in human Th17-cell differentiation [5][6][7][8][9][10]. Acosta-Rodriguez et al. [5] found that human Th17 cells originate in response to the combined activity of IL-1b and IL-6, whereas Wilson et al. [6] found that the activity of IL-1b or IL-23 alone was critical, the combined activity of the two cytokines exerting no additive or synergistic effect [6].In another study, IL-1b and IL-6 upregulated RORgt expression, but they did not induce Th17 differentiation from human adult naïve CD4 + T cells, whereas IL-23 was a powerful upregulator of its own receptor and an important inducer of . In some human studies, the addition of TGF-b to human naïve or memory CD4 + T cells was even found to be inhibitory on the development of Th17 cells [5,6,8]. These differences between humans and mice and the discrepancies among different studies in humans were attributed to the difficulty to ensure a truly naïve T-cell population in these latter [9]. Accordingly, van Beelen et al. [10] found that the combined activity of IL-1a or IL-1b and IL-23 was required for the enhancement of IL-17A-producing human memory T cells, whereas under these or even other conditions, the differentiation of human naïve T cells from adult subjects into Th17 cells could not be achieved [10]. 207Recently, however, three independent studies [11][12][13] showed that, in contrast to the previous observations [5][6][7][8], even the differentiation of human Th17 cells requires the activity of TGF-b. All these authors [11][12][13] suggested that in previous studies performed in humans [5][6][7][8], the role of TGF-b had been...