Human tumors instigate granulin-expressing hematopoietic cells that promote malignancy by activating stromal fibroblasts in mice
Moshe Elkabets, … , Robert A. Weinberg, Sandra S. McAllister
Moshe Elkabets, … , Robert A. Weinberg, Sandra S. McAllister
Published January 25, 2011
Citation Information: J Clin Invest. 2011;121(2):784-799. https://doi.org/10.1172/JCI43757.
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Research Article

Human tumors instigate granulin-expressing hematopoietic cells that promote malignancy by activating stromal fibroblasts in mice

Abstract

Systemic instigation is a process by which endocrine signals sent from certain tumors (instigators) stimulate BM cells (BMCs), which are mobilized into the circulation and subsequently foster the growth of otherwise indolent carcinoma cells (responders) residing at distant anatomical sites. The identity of the BMCs and their specific contribution or contributions to responder tumor growth have been elusive. Here, we have demonstrated that Sca1+cKit– hematopoietic BMCs of mouse hosts bearing instigating tumors promote the growth of responding tumors that form with a myofibroblast-rich, desmoplastic stroma. Such stroma is almost always observed in malignant human adenocarcinomas and is an indicator of poor prognosis. We then identified granulin (GRN) as the most upregulated gene in instigating Sca1+cKit– BMCs relative to counterpart control cells. The GRN+ BMCs that were recruited to the responding tumors induced resident tissue fibroblasts to express genes that promoted malignant tumor progression; indeed, treatment with recombinant GRN alone was sufficient to promote desmoplastic responding tumor growth. Further, analysis of tumor tissues from a cohort of breast cancer patients revealed that high GRN expression correlated with the most aggressive triple-negative, basal-like tumor subtype and reduced patient survival. Our data suggest that GRN and the unique hematopoietic BMCs that produce it might serve as novel therapeutic targets.

Authors

Moshe Elkabets, Ann M. Gifford, Christina Scheel, Bjorn Nilsson, Ferenc Reinhardt, Mark-Anthony Bray, Anne E. Carpenter, Karin Jirström, Kristina Magnusson, Benjamin L. Ebert, Fredrik Pontén, Robert A. Weinberg, Sandra S. McAllister

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Figure 6

GRN induces αSMA expression in human mammary fibroblasts and affects tumor growth.

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GRN induces αSMA expression in human mammary fibroblasts and affects tum...
(A) Images show 2 different preparations of cultured normal human mammary fibroblasts (hMF-1 and hMF-2; isolated from patients undergoing reduction mammoplasty) following 6-day treatment with 5 ng/ml recombinant human TGF-β-1, human GRN protein (hGRN) at a low dose (250 ng/ml) or high dose (1 μg/ml), or PBS control. Treated cells were stained for αSMA (red); cell nuclei were stained with DAPI (blue). Original magnification, ×200. (B) Graphs representing CellProfiler quantification of αSMA staining in cultured human mammary fibroblasts from A following indicated treatments. Left: average percentage of total image area occupied by αSMA+ staining. Right: average αSMA staining per cell (arbitrary units) as calculated by total αSMA+ pixel area divided by number of cell nuclei counted in each image by CellProfiler software. n = 6 images per group; P values indicated below graphs. Data are expressed as mean ± SEM. (C) Representative images of responding tumors resulting from injection of admixtures of responder cells with human mammary fibroblasts that had been pretreated with PBS (top) or GRN (bottom). Left: H&E stains of responding tumor sections. Original magnification, ×20. Center and right: merged images of tumor sections stained for the SV40 LgT (green) to visualize responder cells, Ki67 (red) to visualize proliferating cells, and DAPI to mark cell nuclei. Yellow indicates proliferating responding tumor cells.