Effects of inflammatory factors on mesenchymal stem cells and their role in the promotion of tumor angiogenesis in colon cancer.

Mesenchymal stem cells (MSCs), which are modulated by cytokines present in the tumor microenvironment, play an important role in tumor progression. It is well documented that inflammation is an important part of the tumor microenvironment, so we investigated whether stimulation of MSCs by inflammatory cytokines would contribute to their ability to promote tumor growth. We first showed that MSCs could increase C26 colon cancer growth in mice. This growth-promoting effect was further accelerated when the MSCs were pre-stimulated by inflammatory factors IFN-γ and TNF-α. At the same time, we demonstrated that MSCs pre-stimulated by both inflammatory factors could promote tumor angiogenesis in vivo to a greater degree than untreated MSCs or MSCs pre-stimulated by either IFN-γ or TNF-α alone. A hen egg test-chorioallantoic membrane (HET-CAM) assay showed that treatment of MSC-conditioned medium can promote chorioallantoic membrane angiogenesis in vitro, especially treatment with conditioned medium of MSCs pretreated with IFN-γ and TNF-α together. This mechanism of promoting angiogenesis appears to take place via an increase in the expression of vascular endothelial growth factor (VEGF), which itself takes place through an increase in signaling in the hypoxia-inducible factor 1α (HIF-1α)-dependent pathway. Inhibition of HIF-1α in MSCs by siRNA was found to effectively reduce the ability of MSC to affect the growth of colon cancer in vivo in the inflammatory microenviroment. These results indicate that MSCs stimulated by inflammatory cytokines such as IFN-γ and TNF-α in the tumor microenvironment express higher levels of VEGF via the HIF-1α signaling pathway and that these MSCs then enhance tumor angiogenesis, finally leading to colon cancer growth in mice.

[Interleukin 7 and its receptor promote cell proliferation and induce lymphangiogenesis in non-small cell lung cancer].

OBJECTIVE: To study the mechanism of interleukin 7/interleukin 7 receptor (IL-7/IL-7R) in promoting cell proliferation and inducing lymphangiogenesis of non-small cell lung cancer (NSCLC) in vivo and in vitro. METHODS: Immunohistochemical study for IL-7, IL-7R, cyclin D1 and vascular endothelial growth factor-D (VEGF-D) was carried out in NSCLC tissues from 95 patients. The relationship between IL-7/IL-7R expression and various parameters was analyzed. The mechanism of IL-7/IL-7R in promoting cell proliferation and inducing lymphangiogenesis was studied by methylthiazolyldiphenyl-tetrazolium bromide, fluorescence-activated cell sorting, reverse transcriptase-PCR, Western blot, co-immunoprecipitation, chromatin immunoprecipitation and nude mice experiments with xenograft tumors. RESULTS: IL-7 (63.2%, 60/95), IL-7R (61.1%, 58/95), cyclin D1 (52.6%, 50/95) and VEGF-D (58.9%, 56/95) showed that high level of expression in NSCLC. IL-7/IL-7R over-expression correlated with cyclin D1 expression (P < 0.01, P < 0.01), VEGF-D expression (P < 0.01, P < 0.01), increased lymphovascular density (P = 0.005, P = 0.013), advanced clinical stage (P = 0.008, P = 0.005) and presence of lymph node metastasis (P < 0.01, P < 0.01). IL-7/IL-7R could promote proliferation of A549 cell, increase cyclin D1 and VEGF-D expression, and enhance c-Fos/c-Jun expression and phosphorylation, resulting in formation of heterodimer. Furthermore, IL-7/IL-7R could induce binding of c-Fos/c-Jun to cyclin D1/VEGF-D promoters and regulate their transcription. IL-7/IL-7R could also promote proliferation and lymphangiogenesis of lung cancer xenograft tumors. CONCLUSIONS: IL-7/IL-7R promotes c-Fos/c-Jun expression and activity in NSCLC. This further facilitates cyclin D1 expression and accelerates proliferation of cells and VEGF-D-induced lymphovascular formation.