Increased expression of extracellular matrix (ECM) proteins in circulating tumor cells (CTCs) suggests potential function of cancer cell-produced ECM in initiation of cancer cell colonization. Here, we showed that collagen and heat shock protein 47 (Hsp47), a chaperone facilitating collagen secretion and deposition, were highly expressed during the epithelial-mesenchymal transition (EMT) and in CTCs. Hsp47 expression induced mesenchymal phenotypes in mammary epithelial cells (MECs), enhanced platelet recruitment, and promoted lung retention and colonization of cancer cells. Platelet depletion in vivo abolished Hsp47-induced cancer cell retention in the lung, suggesting that Hsp47 promotes cancer cell colonization by enhancing cancer cell–platelet interaction. Using rescue experiments and functional blocking antibodies, we identified type I collagen as the key mediator of Hsp47-induced cancer cell–platelet interaction. We also found that Hsp47-dependent collagen deposition and platelet recruitment facilitated cancer cell clustering and extravasation in vitro. By analyzing DNA/RNA sequencing data generated from human breast cancer tissues, we showed that gene amplification and increased expression of Hsp47 were associated with cancer metastasis. These results suggest that targeting the Hsp47/collagen axis is a promising strategy to block cancer cell–platelet interaction and cancer colonization in secondary organs.

Document Type


Publication Date


Notes/Citation Information

Published in PNAS, p. 1-11.

Copyright © 2020 the Author(s).

This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).

Digital Object Identifier (DOI)


Funding Information

This study was supported by National Cancer Institute Grants 1R01 CA207772, 1R01 CA215095, and 1R21 CA209045 (to R.X.).

Related Content

Data deposition: Microarray data have been deposited in the Gene Expression Omnibus(GEO) database, https://www.ncbi.nlm.nih.gov/geo (accession no GSE143349).

This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1911951117/-/DCSupplemental. It is also available as the additional file listed at the end of this record.

pnas.1911951117.sapp.pdf (2663 kB)
Supporting Information