Compared Regorafenib mw with conventional IFN-��, we found that pegIFN-�� induced a broader spectrum of ISGs, including many genes involved in cellular immune responses. The initial activation of ISGF3 was the main driver of ISG transcription during the entire week after the first injection of pegIFN-��. The induction of secondary transcription factors and of unphosphorylated STAT1 (U-STAT1) had negligible effects. We conclude that the superior therapeutic efficacy of pegIFN-�� is not caused by a sustained activation of the Jak/STAT pathway in hepatocytes, but rather by the sustained induction of ISGs in liver-infiltrating immune cells. Results pegIFN-��2b induced STAT1 phosphorylation and ISG expression in the liver. We studied pegIFN-��2b�Cinduced STAT1 phosphorylation and gene regulation in 18 patients who underwent treatment for CHC with pegIFN-�� and ribavirin.
All patients had a first liver biopsy before treatment during the routine clinical CHC work-up. A second biopsy was taken 4 hours (n = 6), 16 hours (n = 3), 2 days (n = 3), 4 days (n = 3), and 6 days (n = 3) after the first injection of pegIFN-��2b. The 6 patients whose second liver biopsy was performed 4 hours after injection were selected from among the 16 patients who had already been included in the previous study described above (13), because they had no preactivation of the endogenous IFN system in the liver and a normal response to pegIFN-��2b. The patients were selected in a two-step procedure for the later time points.
First, liver biopsies from patients Batimastat with CHC who agreed to donate part of their liver biopsy for research were analyzed with a previously developed and validated four-gene classifier to predict their likelihood of responding to pegIFN-�� (17). Patients with a high probability of an unimpaired, normal response to pegIFN-�� were then asked to participate in our study and to consent to a second liver biopsy. This two-step selection process was necessary, because in patients with preinduced hepatic ISGs, the Jak/STAT signaling pathway is refractory in liver cells (13), and a second liver biopsy would have been of little use for the study of pegIFN-�� pharmacodynamic effects in the liver. Indeed, the selection process with the four-gene classifier was highly accurate in predicting a good response to pegIFN-��: all patients were treatment responders, and apart from 1 patient who relapsed after treatment, all patients were cured of their HCV infection (Table (Table11). Table 1 Patient characteristics We analyzed pegIFN-��2b�Cinduced Jak/STAT signaling by immunohistochemistry (IHC) with phosphorylated STAT1�Cspecific (p-STAT�Cspecific) antibodies.