Breast cancer metastasis to bone is a critical determinant of long-term survival after treatment of primary tumors. We used a mouse model of spontaneous bone metastasis to determine new molecular mechanisms. Differential transcriptome comparisons of primary and metastatic tumor cells revealed that a substantial set of genes suppressed in bone metastases were highly enriched for promoter elements for the type I interferon (IFN) regulatory factor, Irf7, itself suppressed in mouse and human metastases. The critical function of the Irf7 pathway was demonstrated by restoration of exogenous Irf7 or systemic interferon administration, which significantly reduced bone metastases and prolonged metastasis-free survival. Using mice deficient in the type I receptor (Ifnar1-/-) or mature B, T and NK cell responses (NOD Scid IL-2r-/- mice), we demonstrated that Irf7-driven suppression of metastasis was reliant on IFN signaling to host immune cells. Metastasis suppression correlated with decreased accumulation of myeloid-derived suppressor cells and increased CD4++, CD8 T cells and NK cells in the peripheral blood and was reversed by depletion of CD8+ cells and NK cells. Clinical importance of our findings was demonstrated as increased primary tumor Irf7 expression predicted prolonged bone and lung metastasis-free survival. Thus we report for the first time, a novel innate immune pathway, intrinsic to breast cancer cells, whose suppression in turn restricts systemic immunosurveillance to enable metastasis. This pathway may constitute a novel therapeutic target for restricting breast cancer metastases.
Silencing of Irf7 pathways in breast cancer cells promotes bone metastasis through immune escape.
Specimen part
View SamplesHuman Immunodeficiency Virus (HIV) associated nephropathy (HIVAN) is characterized clinically by both nephrosis and by rapidly progressive kidney dysfunction. HIVAN is characterized histologically by both collapsing focal segmental glomerulosclerosis and prominent tubular damage. Neutrophil Gelatinase Associated Lipocalin (NGAL) is known to be rapidly expressed in distal segments of the nephron at the onset of different types of acute kidney injury, but few studies have examined NGAL in chronic kidney disease models. We found that urinary NGAL (uNGAL) was highly expressed by patients with biopsy proven HIVAN, whereas HIV+ patients without HIVAN demonstrated lower levels. uNGAL was also highly expressed in the TgFVB mouse model of HIVAN, which demonstrated NGAL gene expression in dilated, microcystic segments of the nephron. These data show that NGAL is markedly upregulated in the setting of HIVAN, and suggest that uNGAL levels may provide a non-invasive screening test to detect HIVAN related tubular disease.
Urinary NGAL marks cystic disease in HIV-associated nephropathy.
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