Growth and differentiation factor 3 induces expression of genes related to differentiation in a model of cancer stem cells and protects them from retinoic acid-induced apoptosis.

Misexpression of growth factors, particularly those related to stem cell-like phenotype, is often observed in several cancer types. It has been found to influence parameters of disease progression like cell proliferation, differentiation, maintenance of undifferentiated phenotype and modulation of the immune system. GDF3 is a TGFB family member associated with pluripotency and differentiation during embryonic development that has been previously reported to be re-expressed in a number of cancer types. However, its role in tumor development and progression has not been clarified yet. In this study we decipher the role of GDF3 in an in vitro model of cancer stem cells, NCCIT cells. By classical approach to study protein function combined with high-throughput technique for transcriptome analysis and differentiation assays we evaluated GDF3 as a potential therapeutic target. We observed that GDF3 robustly induces a panel of genes related to differentiation, including several potent tumor suppressors, without impacting the proliferative capacity. Moreover, we report for the first time the protective effect of GDF3 against retinoic acid-induced apoptosis in cells with stem cell-like properties. Our study implies that blocking of GDF3 combined with retinoic acid-treatment of solid cancers is a compelling direction for further investigations, which can lead to re-design of cancer differentiation therapies.

Macrophage migration inhibitory factor counterregulates dexamethasone-mediated suppression of hypoxia-inducible factor-1 alpha function and differentially influences human CD4+ T cell proliferation under hypoxia.

Hypoxia, a feature of inflammation and tumors, is a potent inducer of the proinflammatory cytokine macrophage migration inhibitory factor (MIF). In transformed cells, MIF was shown to modulate and to be modulated via the oxygen-sensitive transcription factor hypoxia-inducible factor (HIF)-1. Furthermore, anti-inflammatory glucocorticoids (GCs) were described to regulate MIF action. However, in-depth studies of the interaction between MIF and HIF-1 and GC action in nontransformed primary human CD4(+) T cells under hypoxia are missing. Therefore, we investigated the functional relationship between MIF and HIF and the impact of the GC dexamethasone (DEX) on these key players of inflammation in human CD4(+) T cells. In this article, we show that hypoxia, and specifically HIF-1, is a potent and rapid inducer of MIF expression in primary human CD4(+) T cells, as well as in Jurkat T cells. MIF signaling via CD74, in turn, is essential for hypoxia-mediated HIF-1α expression and HIF-1 target gene induction involving ERK/mammalian target of rapamycin activity complemented by PI3K activation upon mitogen stimulation. Furthermore, MIF signaling enhances T cell proliferation under normoxia but not hypoxia. MIF also counterregulates DEX-mediated suppression of MIF and HIF-1α expression. Based on these data, we suggest that hypoxia significantly affects the expression of HIF-1α in a MIF-dependent manner leading to a positive-feedback loop in primary human CD4(+) T cells, thus influencing the lymphoproliferative response and DEX action via the GC receptor. Therefore, we suggest that HIF and/or MIF could be useful targets to optimize GC therapy when treating inflammation.

Adaptation of human CD4+ T cells to pathophysiological hypoxia: a transcriptome analysis.

OBJECTIVE: Inflamed tissues are usually characterized by low oxygen levels. We investigated whether pathophysiological hypoxia (pO(2) < 1%) as found in the rheumatoid synovium modulates the transcriptome of human CD4+ T cells. METHODS: We analyzed the extent to which hypoxia influences the transcriptome in the rheumatoid synovium according to a gene cluster reflecting adaptation to low oxygen levels. Hypoxia-inducible factor-1alpha (HIF-1alpha) was detected in the rheumatoid synovium using immunohistochemistry. Isolated human CD4+ T cells were exposed to hypoxia and analyzed using microarray analysis, quantitative polymerase chain reaction, and immunoblot detection. RESULTS: In rheumatoid arthritis (RA) synovial tissue samples, hypoxia modulates the transcription profile. This profile is similar, but not identical, to that found in isolated CD4+ T cells incubated under hypoxic conditions. We show that HIF-1alpha is expressed in synovial tissue samples and in hypoxic CD4+ cells; and that hypoxia directly affects differential gene expression in human T cells with up to 4.8% modulation of the transcriptome. Functional genome analysis revealed substantial effects of hypoxia on immune response, transcriptional regulation, protein modification, cell growth and proliferation, and cell metabolism. CONCLUSION: Severe hypoxia, a feature of joint inflammation, considerably modulates the transcriptome of cells found in the rheumatoid synovium. Human CD4+ T cells adapt to hypoxic conditions mainly by HIF-1-driven effects on the transcriptome reflecting a profound influence on immune functions. Thus, hypoxia must be taken into account when therapeutically targeting inflammation.