Pharmacokinetics and biological activity in subcutaneous long-term administration of recombinant interferon-gamma in cancer patients

Deficiency of interferon-gamma or its receptor promotes colorectal cancer development

Genetic variations in interferon-gamma (IFN-γ) and its receptor (IFNγR) subunits are closely associated with the risk of colorectal cancer (CRC) and survival after diagnosis. However, the role of loss of IFN-γ or IFNγR function in the pathogenesis of CRC remains unclear. Here, we investigated the role of endogenous IFN-γ deficiency in adenomatous polyposis coli (Apc)-mediated intestinal tumor by developing a variant of Apc(Min/+) mice. The Apc(Min/+)IFN-γ(+/-) mice presented with increased number and size of adenomas, and 41.7% of these mice developed adenocarcinoma. Molecular analyses of the adenomas suggested that heterozygous deletion of IFN-γ promoted EGFR/Erk1/2 and Wnt/β-catenin signaling. In vitro, IFN-γ administration inhibited Apc-mutated HT-29 colon cancer cell proliferation and had no effect on the proliferation of HCT-116 colon cancer cells that express wild-type Apc. Besides, we challenged HT-29 cells with small interfering RNA targeting one of its receptor subunits IFNγR1. We found that knockdown of IFNγR1 in HT-29 cells stimulated cell proliferation and colony formation, which was also related to the regulation of EGFR/Erk1/2 and Wnt/β-catenin signaling. Thus, our results strongly support the notion that IFN-γ and IFNγR1 act as a rate-limiting factor in the development of CRC, uncovering a novel role for them in cancer biology.

Increased Phagocyte FcγRI Expression and Improved Fcγ-Receptor–Mediated Phagocytosis After In Vivo Recombinant Human Interferon-γ Treatment of Normal Human Subjects

Recombinant human interferon-γ (rhIFN-γ) decreases the frequency of serious infections in patients with chronic granulomatous disease (CGD) through an unknown mechanism. To test the hypothesis that it exerts a beneficial effect by enhancing clearance of microbes from the bloodstream and tissues, normal human subjects were treated in vivo with rhIFN-γ. Phagocyte opsonic receptor expression, serum opsonin levels, and phagocytosis of bacteria were then measured. A 4.7-fold increase in neutrophil expression of the high-affinity Fcγ-receptor (FcγRI) was observed that peaked 48 hours after the initiation of rhIFN-γ treatment (P < .05). Monocyte expression of FcγRI, FcγRII, FcγRIII, CD11a, CD11b, CD18, and HLA-DR also significantly increased with peak expression at 48 hours. Phagocytosis by neutrophils of killed Staphylococcus aureus opsonized with heat-inactivated pooled human serum significantly improved after rhIFN-γ treatment (P < .05) and correlated with FcγRI expression by neutrophils (r = .8, P < .001). This increase in ingestion could be inhibited by anti-FcγRI monoclonal antibodies. Levels of the serum opsonin lipopolysaccharide-binding protein also significantly increased after in vivo rhIFN-γ (P < .05). These results suggest that the protective effect of rhIFN-γ in patients with CGD may involve improved microbial clearance. Moreover, improved phagocyte trafficking may occur secondary to increased expression of monocyte β2 -integrins. Because these IFN-γ–related improvements in host defense were seen in normal hosts, rhIFN-γ may have broader applications in the treatment of various disorders of immunity in addition to its demonstrated efficacy in CGD.