Mesenchymal Stem Cell–Secreted Extracellular Vesicles Instruct Stepwise Dedifferentiation of Breast Cancer Cells into Dormancy at the Bone Marrow Perivascular Region

Abstract

In the bone marrow (BM), breast cancer cells (BCC) can survive in dormancy for decades as cancer stem cells (CSC), resurging as tertiary metastasis. The endosteal region where BCCs exist as CSCs poses a challenge to target them, mostly due to the coexistence of endogenous hematopoietic stem cells. This study addresses the early period of dormancy when BCCs enter BM at the perivascular region to begin the transition into CSCs, which we propose as the final step in dormancy. A two-step process comprises the Wnt-β-catenin pathway mediating BCC dedifferentiation into CSCs at the BM perivascular niche. At this site, BCCs responded to two types of mesenchymal stem cell (MSC)–released extracellular vesicles (EV) that may include exosomes. Early released EVs began the transition into cycling quiescence, DNA repair, and reorganization into distinct BCC subsets. After contact with breast cancer, the content of EVs changed (primed) to complete dedifferentiation into a more homogeneous population with CSC properties. BCC progenitors (Oct4alo), which are distant from CSCs in a hierarchical stratification, were sensitive to MSC EVs. Despite CSC function, Oct4alo BCCs expressed multipotent pathways similar to CSCs. Oct4alo BCCs dedifferentiated and colocalized with MSCs (murine and human BM) in vivo. Overall, these findings elucidate a mechanism of early dormancy at the BM perivascular region and provide evidence of epigenome reorganization as a potential new therapy for breast cancer. Significance: These findings describe how the initial process of dormancy and dedifferentiation of breast cancer cells at the bone marrow perivascular niche requires mesenchymal stem cell–derived exosomes, indicating a potential target for therapeutic intervention.

Specific N-cadherin–dependent pathways drive human breast cancer dormancy in bone marrow

“…We immunoprecipitated CDH2 in MSCs and also showed the interaction with Cx43 in MSCs ( Fig S1D ). This finding is significant because MSCs, which are also found in the perivascular niche ( Ehninger & Trumpp, 2011 ), are important for immediate transition to dormancy ( Sandiford et al, 2021 ). In summary, we carried out knockdown of CDH2 in CSCs and demonstrated reduced cells in femurs.…”

“…BCCs show preference for BM, resulting in poor prognosis ( Braun et al, 2005 ; Tjensvoll et al, 2019 ). Once in the BM, BCCs evoke the resident BM niche cells (such as macrophages, fibroblasts, and mesenchymal stem cells [MSCs]) to facilitate their transition into a dormant phase ( Rao et al, 2004 ; Patel et al, 2012 , 2014 ; Bliss et al, 2016 ; Sandiford et al, 2021 ). Investigations to identify specific markers for CSCs revealed continuous phases of cellular plasticity, which include dedifferentiation of BCC progenitors into BCCs with stem cell–like properties ( Naume et al, 2007 ; Plaks et al, 2015 ; Wang et al, 2017 ; Tjensvoll et al, 2019 ; Lynch-Sutherland et al, 2020 ).…”

“…Thus, it could be argued that CSCs may be defined as a cellular state that is dependent on the tissue microenvironment. Indeed, MSCs, which constitute the cellular niche within the BM, can induce BCC quiescence through gap junctional intercellular communication (GJIC) and, through their exosomal secretome ( Patel et al, 2014 ; Bliss et al, 2016 ; Sandiford et al, 2021 ).…”

Extracellular Vesicles Facilitate Large-Scale, Homogenizing Dynamic Exchange of Proteins and RNA Among Cultured Chinese Hamster Ovary (CHO) and Human Cells

“…Prior literature has investigated the relationship between cancer cells and stem cells and the transfer of regulatory RNAs via EVs to progress or inhibit tumor growth (Adamo, Dal Collo, Bazzoni, & Krampera, 2019; Fonsato et al, 2012; Lee et al, 2013; Sandiford et al, 2021; Zhou et al, 2019). The ability of cancerous cells and stem cells to communicate throughout the body and in culture presents interesting questions on the effects of how cancer cell derived EVs and stem cell EVs can influence cell expression regulation.…”

“…Y. Kao & Papoutsakis, 2019). For example, in in vitro studies, uptake of mesenchymal stem cell derived EVs by breast cancer cell lines have been linked to dedifferentiation of breast cancer cells towards cancer stem cells (Sandiford et al, 2021). Megakaryocyte derived microparticles (MkMPs) have been documented as selectively targeting hematopoietic stem and progenitor cells (HSPCs) (J.…”