Proteolytic fragments of fibronectin function as matrikines driving the chemotactic affinity of prostate cancer cells to human bone marrow mesenchymal stromal cells via the α5β1 integrin

Abstract

The haematopoietic niche is contributed to by bone marrow-resident mesenchymal stromal cells (BM-MSCs) and subverted by prostate cancer cells. To study mechanisms by which BM-MSCs and prostate cancer cells may interact, we assessed the migration, invasion, adhesion and proliferation of bone-derived prostate cancer cells (PC-3) in co-culture with pluripotent human BM-MSCs. We observed a strong adhesive, migratory and invasive phenotype of PC-3 cells with BM-MSC-coculture and set out to isolate and characterize the bioactive principle. Initial studies indicated that chemotaxis was secondary to a protein residing in the >100kDa fraction. Size-exclusion chromatography (SEC) recovered peak activity in a high-molecular weight fraction containing thrombospondin-1 (TSP1). While TSP1 immunodepletion decreased activity, put-back with purified TSP1 did not reproduce bioactivity. Further purification of the TSP1-containing high-molecular weight fraction of the BM-MSC secretome with heparin-affinity chromatography recovered bioactivity with highly restricted bands on polyacrylamide gel electrophoresis, determined by mass spectroscopy to be proteolytic fragments of fibronectin (FN). Put-back experiments with full-length FN permitted adhesion but failed to induce migration. Monospecific antibodies to FN blocked adhesion. Proteolytic cleavage of FN generated FN fragments which now induced migration. Neutralizing monoclonal antibodies to FN receptors a5 and b1 integrins, and a5 knockdown specifically blocked migration and adhesion. Conclusion: Fibronectin fragments (FNFr) function as matrikines driving the chemotactic affinity of prostate cancer cells via the a5b1 integrin. Taken together with the high-frequency of a5b1 expression in disseminated prostate cancer cells in bone marrow aspirates from patients, the FNFr/FN-a5b1 interaction warrants further study as a therapeutic target.

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“…Another recent study indicated that the dysregulated of FN1 restricted prostate cancer cell invasion [12]. And the enhanced fibronectin expression in tamoxifen-resistant breast cancer cells had been reported by You et al [13].…”

Characterization of plasma fibronectin for migration, proliferation, and differentiation on human articular chondrocytes

“…However, similar results to ours were found in a study, which showed that proliferation could not be induced in rat‐derived bone marrow mesenchymal stem cells treated with 0.1–100 μg/ml pFN (Jimbo et al, ). The same was observed in prostate cancer cells, where FN did not show a stimulating effect on cell proliferation (Joshi, Goihberg, Ren, Pilichowska, Mathew, ).…”

Matrix‐filled microcavities in the emerging avian left‐right organizer

“…LLC formation enables spatio‐temporal regulation of interaction of TGF‐beta with cell surface receptors which is prevented by LLCs and is enabled by local proteolytic cleavage of ECM. Furthermore, proteins of ECM possess elements which are released by proteolysis and activate matrikines signaling by binding to cell surface receptors (as shown for fibronectin producing a rise of matrikines which in turn promote cell motility). Testing this hypothesis would require focused perinodal knockdown of ECM‐related NMC components to minimize global deleterious effects even if this may be challenging in view of the dynamic character of the node .…”