The role of AP-1 in colon cancer stem cells.

e14699 Background: The AP-1 transcription factor is a heterodimeric protein, which regulates gene expression in response to a variety of stimuli. The above factor also regulates cellular processes including differentiation, proliferation and apoptosis. The AP-1 heterodimeric protein is consisted of the combination of c-Jun and c-Fos proteins. The c-Jun is activated through phosphorylation, but it has also phosphorylation independent function. The c-FOS is a cellular proto-oncogene, which is up-regulated in response to many extracellular signals. The present study aim to find out the effect of c-FOS gene in Colon CSCs according to stemness. Methods: In all experiments there have been used established human colon cancer stem cells (CelProgen). Experiments for suppression of c-FOS expression, by using specific siRNA were performed and the transfection was evaluated with qPCR assays. The stemness transcription factors Nanog, Oct3/4 and Sox2 were tested with gene expression assays, and a relative quantification was performed according to Livak method. The CD44 and CD26 genes were used as positive markers in colon cancer in all procedures. Results: The results indicated that the c-FOS proto-oncogene affects the gene expression of transcription factors, which are essential for the maintenance of stemness. However the results were different, depending on the rate of suppression. The suppression of c-FOS by 65% led to increase in gene expression of stemness transcription factors, with higher rates for Nanog, smaller for Sox2 and minimum for Oct3/4. Unlike results were observed when the expression was suppressed by 85%. In this case there was observed higher decrease in Oct3/4 and less in the other markers. Conclusions: Up to now studies have demonstrated the significant role of c-JUN in stem cells, but little is known about the other half of AP-1 complex, the c-FOS gene. In the first part of the study it was confirmed the effect of c-FOS in stemness, as it was observed change in gene expression of stemness’s significant transcription factors. However it is indicated that there is a cross-talk between JNK pathway and stemness. Further studies in more samples are needed to demonstrate all the above, so that it can be used at clinical level.