The interactions between tumor cells and the microenvironment play a crucial role in tumor progression. Tumor cells secrete growth factors, cytokines and proteases and are thus able to affect the gene expression of stromal cells. Activate d stromal cells like fibroblasts, immune cells and endothelial cells are able to promote tumor progression by releasing growth factors, cytokines and proteases. One of the factors which play a central role in this tumor - and stroma - interaction is interleuk in - 6. In many tumor entities, the IL - 6 signal pathway is highly dysregulated by overexpression of IL - 6 and otherwise by permanent activation of the STAT3 transcription factor. In this work, we showed that IL - 6 stimulation resulted in an increased prolifera tion of HaCaT - ras A5 benign tumor keratinocytes, but does not affect the fibroblast cell line MSU1.1. This increase correlates with the activation of the JAK/STAT signaling pathway. We were able to demonstrate that the amount of activated STAT3 proteins after IL - 6 stimulation in HaCaT - ras A5 cells is strongly up regulated and the inhibition of STAT3 activation also inhibits the proliferation of HaCaT - ras A5 cells. This showed the crucial role of the STAT3 activation in proliferation of HaCaT - ras A5 cells. In contrast, fibroblasts showed a stronger inhibition of the JAK/STAT signal pathway by SOCS3 in comparison with the HaCaT - ras A5 cells. All data where used to establish a mathematical model of JAK/STAT pathway which is able to describe the dynamic behav ior of STAT3 and SOCS3 Proteins. In addition to the effects shown, IL - 6 is also able to affect the proliferation in an indirect manner. To this end, IL - 6 stimulation activates a network of growth factors in HaCaT - ras A5 cells and fibroblasts like HGF, KGF , VEGF or IL - 8. While IL - 6 showed no direct influence of the proliferation of fibroblasts, the addition of the condition media of both IL - 6 stimulated HaCaT - ras A5 and as well as IL - 6 stimulated MSU1.1 resulted in strong up regulation of the cell numbers o f the other cell line. Comparative gene expression analyses clearly showed that upon IL - 6 stimulation of over 16000 analyzed genes in HaCaT - ras A5 and Fibroblasts only a subset of 19 genes was up regulated in both cell types. The up regulated genes were f ound to be closely connected with the interferon signal pathway which gives a potential hint of the cause of the IL - 6 induced inhibition of growth in fibroblasts. Further gene expression analyses showed that the proteinase inhibitor SerpinB4, was permanent ly up regulated in IL - 6 stimulated HaCaT - ras A5 cells. The down regulation of Summary 9 SerpinB4 by siRNA knockdown indicated that SerpinB4 plays an important role in the proliferation of HaCaT - ras A5. The observation of this work of the detailed regulation of IL - 6 in tumor and stroma cells should give information about the tumor promoting effect of IL - 6 and will ultimately serve as a basis for therapeutic therapies.
|Supervisor:||Angel, Prof. Dr. Peter|
|Date of thesis defense:||20 February 2014|
|Date Deposited:||27 Feb 2014 09:59|
|Faculties / Institutes:||The Faculty of Bio Sciences > Dean's Office of the Faculty of Bio Sciences|
|Subjects:||570 Life sciences|