Persistence of the bacterial pathogen Granulibacter bethesdensis in chronic granulomatous disease monocytes and macrophages lacking a functional NADPH oxidase.

Granulibacter bethesdensis is a Gram-negative pathogen in patients with chronic granulomatous disease (CGD), a deficiency in the phagocyte NADPH oxidase. Repeated isolation of genetically identical strains from the same patient over years, and prolonged waxing and waning seropositivity in some subjects, raises the possibility of long-term persistence. G. bethesdensis resists killing by serum, CGD polymorphonuclear leukocytes (PMN), and antimicrobial peptides, indicating resistance to nonoxidative killing mechanisms. Although G. bethesdensis extends the survival of PMN, persistent intracellular bacterial survival might rely on longer-lived macrophages and their precursor monocytes. Therefore, we examined phagocytic killing by primary human monocytes and monocyte-derived macrophages (MDM). Cells from both normal and CGD subjects internalized G. bethesdensis similarly. G. bethesdensis stimulated superoxide production in normal monocytes, but to a lesser degree than in normal PMN. Normal but not CGD monocytes and MDM killed G. bethesdensis and required in vitro treatment with IFN-γ to maintain this killing effect. Although in vitro IFN-γ did not enhance G. bethesdensis killing in CGD monocytes, it restricted growth in proportion to CGD PMN residual superoxide production, providing a potential method to identify patients responsive to IFN-γ therapy. In IFN-γ-treated CGD MDM, G. bethesdensis persisted for the duration of the study (7 d) without decreasing viability of the host cells. These results indicate that G. bethesdensis is highly resistant to oxygen-independent microbicides of myeloid cells, requires an intact NADPH oxidase for clearance, and can persist long-term in CGD mononuclear phagocytes, most likely relating to the persistence of this microorganism in infected CGD patients.

Heat shock transcription factor Hsf1 is involved in tumor progression via regulation of hypoxia-inducible factor 1 and RNA-binding protein HuR.

Previously we demonstrated that the heat shock transcription factor Hsf1 is indispensable for transformation of mammary epithelial cells by the Her2 oncogene. Since Hsf1 affects oncogene-induced senescence (OIS), these findings suggest that Hsf1 affects tumor initiation when OIS plays a role. Indeed, here we report that Hsf1 knockout suppressed mammary hyperplasia in Her2-expressing mice and reduced tumor emergence. On the other hand, Hsf1 expression increases with advanced breast cancer, indicating that there is an additional role of Hsf1 in tumor progression. We studied rare tumors that developed in Hsf1-knockout mice and found that these tumors grew slower than tumors in control animals and showed suppressed angiogenesis. Similarly, in the xenograft model, knockdown of Hsf1 suppressed angiogenesis, which was associated with suppression of the HIF-1 pathway. Suppression of HIF-1 was at the level of translation due to downregulation of the RNA-binding protein HuR. Importantly, besides HIF-1, HuR controls translation of other major regulators of cancer progression, many of which were suppressed in Hsf1-knockdown cells. Therefore, in addition to OIS, Hsf1 regulates the HuR-HIF-1 pathway, thus affecting both cancer initiation and progression.