Direct but not indirect co-culture with osteogenically differentiated human bone marrow stromal cells increases RANKL/OPG ratio in human breast cancer cells generating bone metastases

Abstract

BackgroundBone metastases arise in nearly 70% of patients with advanced breast cancer, but the complex metastatic process has not been completely clarified yet. RANKL/RANK/OPG pathway modifications and the crosstalk between metastatic cells and bone have been indicated as potential drivers of the process. Interactions between tumor and bone cells have been studied in vivo and in vitro, but specific effects of the direct contact between human metastatic cells and human bone cells on RANKL/RANK/OPG pathway have not been investigated.FindingsWe directly co-cultured bone metastatic human breast cancer cells (BOKL) with osteo-differentiated human mesenchymal cells (BMSCs) from 3 different donors. BMSCs and BOKL were then enzymatically separated and FACS sorted. We found a significant increase in the RANKL/OPG ratio as compared to control, which was not observed in BOKL cultured in medium conditioned by BMSCs, neither in BOKL directly cultured with fibroblasts or medium conditioned by fibroblasts. Direct co-culture with osteo-differentiated BMSCs caused BOKL aggregation while proliferation was not affected by co-culture. To more specifically associate RANKL expression to osteogenic differentiation degree of BMSCs, we determined their osteogenic markers expression and matrix calcification relative to osteoblasts and fibroblasts.ConclusionsIn conclusion, our co-culture model allowed to demonstrate for the first time that direct contact but not paracrine interactions between human metastatic breast cancer cells and bone cells has a significant effect on RANKL/OPG expression in bone metastatic cells. Furthermore, only direct contact with the bone microenvironment induced BOKL clustering without however significantly influencing their proliferation and migration.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-4598-13-238) contains supplementary material, which is available to authorized users.

Transition into inflammatory cancer-associated adipocytes in breast cancer microenvironment requires microRNA regulatory mechanism

“…Also, we could not determine the effect of direct co-culture with various cancer cells on mature adipocytes since we only used indirect co-culture methods. Direct co-culture, which mimics the in vivo cell-cell interaction, might have different effects on adipocytes [36]. Finally, the human counterpart microRNAs of mmu-miR-5112 that regulate the CPEB1 expression in cancer microenvironments should be investigated in future studies.…”

Human breast cancer bone metastasis in vitro and in vivo: a novel 3D model system for studies of tumour cell-bone cell interactions

“…These discs contain all of the cell types and bone matrix that are involved in breast cancer colonisation and growth in this environment. Many in vitro models have tried to recapitulate these interactions between bone cells and tumour cells including co-culture of breast cancer cells with fibroblasts [22,23], mesenchymal stromal cells [24] osteoclasts [25], osteoblasts or a mixture of these cell types [26]. When cultured on plastic these models lack the 3D space that is critical in determining cancer cell function (reviewed in [27]).…”

Phenotypic and functional heterogeneity of cancer-associated fibroblast within the tumor microenvironment

“…When directly co-cultured with breast cancer cells, bone marrow stromal cells, one of the phenotypes of CAFs, induce cancer cell aggregation and enhance bone metastasis stimulating RANKL/OPG pathway [34]. tumor-promoting microenvironment [37].…”