However, unlike RelA p65, high class I HDAC expression did not attain statistical significance for overall survival in pancre atic carcinoma in our study, which might be explained by the fact that although we see a correlation ROCK1 between those parameters in our in vivo data the correlation is not extremely strong. This suggests that RelA p65 is only partly regulated activated by strong HDAC expression. Furthermore, nuclear RelA p65 as well as cytoplasmic RelA p65 positivity was linked to increased HDAC expression when comparing the distri butions of raw expression data, which suggests at least in part a transcriptional regulation and not only a post tran scriptional modification of RelA p65 activity by HDACs.
Our survival results are somewhat in contrast to the results reported by Miyake et al, who found a prognostic impact of HDAC1 expression in a moderately large cohort of pancreatic cancers. We cannot exclude that in certain cohorts of pancreatic cancer such a correlation might exist, however, in our Western European cohort which is twice as large as Miyakes cohort, we were not able to confirm these findings and therefore have to conclude that this observed correlation is not universially applicable. Since cut off values for defining HDAC1 positive negative cases in Miyakes and our study were different, we repeated our analysis with the cut offs used by Miyake. However, this Even though treatment with VPA resulted in a partial removal of nuclear translocated RelA p65 into the cyto plasm in our experiments as well, VPA was less effective in inhibiting DNA binding activity of the transcription factor than SAHA.
The different effectiveness of the two HDIs in deactivating RelA p65 might be explained by the fact that SAHA is known to act on various HDAC isoforms whereas VPA preferentially inhibits class I HDACs. Strong antineoplastic effects of SAHA like growth inhibi tion, induction of apoptosis and cell cycle arrest have been demonstrated in various studies. Our in vitro data on inhibition of RelA p65 activity indicate that these effects could be partly based on an alteration of the NF B signalling pathway. This finding could be of special inter est for the development of new treatment strategies for pancreatic carcinoma, since chronic inflammation due to elevated activities of mediators like NF B are conductive acetylationSAHAPANC 1VPA on I B protein level and histone did not result in a significant survival difference, either.
The finding that HDAC activity is linked Drug_discovery to the activity of RelA p65 in pancreatic carcinoma in vivo could be also confirmed in an in vitro cell culture model, where treat ment of cells with the HDI SAHA led to a markedly decrease in nuclear translocation and binding activity of RelA p65. This is in line with previous studies which reported RelA p65 inhibitory effects of HDIs like Trichos tatin A and SAHA in other cell culture systems. In contrast, Chen et. al.