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In Vitro Co-Culture Models of Breast Cancer Metastatic Progression towards Bone

View Article: PubMed Central - PubMed

ABSTRACT

Advanced breast cancer frequently metastasizes to bone through a multistep process involving the detachment of cells from the primary tumor, their intravasation into the bloodstream, adhesion to the endothelium and extravasation into the bone, culminating with the establishment of a vicious cycle causing extensive bone lysis. In recent years, the crosstalk between tumor cells and secondary organs microenvironment is gaining much attention, being indicated as a crucial aspect in all metastatic steps. To investigate the complex interrelation between the tumor and the microenvironment, both in vitro and in vivo models have been exploited. In vitro models have some advantages over in vivo, mainly the possibility to thoroughly dissect in controlled conditions and with only human cells the cellular and molecular mechanisms underlying the metastatic progression. In this article we will review the main results deriving from in vitro co-culture models, describing mechanisms activated in the crosstalk between breast cancer and bone cells which drive the different metastatic steps.

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Related in: MedlinePlus

Mechanisms involved in the establishment of osteolytic bone metastases. (a) Effects of BCCs on bone resorption mediated by osteoblasts: molecules secreted by BCCs (TGF-β, IL-6, EGF, etc.) have been shown to activate osteoblasts to produce MMP-13 that degrades bone matrix and RANKL and RUNX-2, which stimulate osteoclasts to resorb bone; (b) direct effects of BCCs on osteoblasts differentiation: molecules secreted by BCCs (Galectin-3 and TGF-β1, IGF-2, PDGF) and BCC-expressed proteins (β-catenin) have been shown to regulate osteoblastic differentiation (affecting the expression of specific osteoblastic markers such as ALP, RUNX-2, etc.) through different pathways; (c) effects of molecules released by bone cells on BCCs: crosstalk between bone and cancer cells has been shown to promote an osteomimetic phenotype in BCCs (increasing the expression of typical bone markers such as osteocalcin OCN, osteopontin OPN, etc.) and TGF-β released by bone cells has been shown to activate Notch3 signaling and to promote BCCs growth; (d) direct effects of BCCs on osteoclastic differentiation: molecules secreted (CSF-1) or expressed (RANKL) by BCCs have been demonstrated to promote differentiation and activation of osteoclastic precursors towards mature osteoclasts. ↑: increased; ↓: decreased. Adapted by permission from [61] David, L.W.; Theresa, A.G. Cancer-associated muscle weakness: What’s bone got to do with it. BoneKEy Rep. 2015.
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ijms-17-01405-f004: Mechanisms involved in the establishment of osteolytic bone metastases. (a) Effects of BCCs on bone resorption mediated by osteoblasts: molecules secreted by BCCs (TGF-β, IL-6, EGF, etc.) have been shown to activate osteoblasts to produce MMP-13 that degrades bone matrix and RANKL and RUNX-2, which stimulate osteoclasts to resorb bone; (b) direct effects of BCCs on osteoblasts differentiation: molecules secreted by BCCs (Galectin-3 and TGF-β1, IGF-2, PDGF) and BCC-expressed proteins (β-catenin) have been shown to regulate osteoblastic differentiation (affecting the expression of specific osteoblastic markers such as ALP, RUNX-2, etc.) through different pathways; (c) effects of molecules released by bone cells on BCCs: crosstalk between bone and cancer cells has been shown to promote an osteomimetic phenotype in BCCs (increasing the expression of typical bone markers such as osteocalcin OCN, osteopontin OPN, etc.) and TGF-β released by bone cells has been shown to activate Notch3 signaling and to promote BCCs growth; (d) direct effects of BCCs on osteoclastic differentiation: molecules secreted (CSF-1) or expressed (RANKL) by BCCs have been demonstrated to promote differentiation and activation of osteoclastic precursors towards mature osteoclasts. ↑: increased; ↓: decreased. Adapted by permission from [61] David, L.W.; Theresa, A.G. Cancer-associated muscle weakness: What’s bone got to do with it. BoneKEy Rep. 2015.

Mentions: Once rescued from the dormant state, BCCs are known to promote osteolytic bone metastases through the establishment of “vicious cycles” (amplifying feedback loops), which induce continuous bone resorption and release of pro-tumorigenic factors [58,59] (Figure 4). Beyond the well-studied RANKL-RANK-OPG pathway [59] which will be discussed in a separate section, other signaling programs are involved in the formation of an osteolytic milieu. Morrison and colleagues characterized through co-cultures (direct contact, Transwell, conditioned medium) of BCCs (MDA-1833) and osteoblasts which osteoclast-independent features are critical for bone metastases [60]. The authors found a significant increase in matrix metalloprotease (MMP)-13 mRNA production by osteoblasts when co-cultured with BCCs. The presence of MMP-13 was shown to increase the level of CCL-2, platelet-derived growth factor (PDGF)-C and serum amyloid A3 apolipoprotein SAA3, which can promote monocyte recruitment and osteoclast differentiation. Hence, BCCs produce factors, such as SAA3, that induce osteoblast secretion of MMP-13, which in turn activates the inducers of MMP-13, stimulating additional MMP-13 production and the generation of a vicious cycle (Figure 4a).


In Vitro Co-Culture Models of Breast Cancer Metastatic Progression towards Bone
Mechanisms involved in the establishment of osteolytic bone metastases. (a) Effects of BCCs on bone resorption mediated by osteoblasts: molecules secreted by BCCs (TGF-β, IL-6, EGF, etc.) have been shown to activate osteoblasts to produce MMP-13 that degrades bone matrix and RANKL and RUNX-2, which stimulate osteoclasts to resorb bone; (b) direct effects of BCCs on osteoblasts differentiation: molecules secreted by BCCs (Galectin-3 and TGF-β1, IGF-2, PDGF) and BCC-expressed proteins (β-catenin) have been shown to regulate osteoblastic differentiation (affecting the expression of specific osteoblastic markers such as ALP, RUNX-2, etc.) through different pathways; (c) effects of molecules released by bone cells on BCCs: crosstalk between bone and cancer cells has been shown to promote an osteomimetic phenotype in BCCs (increasing the expression of typical bone markers such as osteocalcin OCN, osteopontin OPN, etc.) and TGF-β released by bone cells has been shown to activate Notch3 signaling and to promote BCCs growth; (d) direct effects of BCCs on osteoclastic differentiation: molecules secreted (CSF-1) or expressed (RANKL) by BCCs have been demonstrated to promote differentiation and activation of osteoclastic precursors towards mature osteoclasts. ↑: increased; ↓: decreased. Adapted by permission from [61] David, L.W.; Theresa, A.G. Cancer-associated muscle weakness: What’s bone got to do with it. BoneKEy Rep. 2015.
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ijms-17-01405-f004: Mechanisms involved in the establishment of osteolytic bone metastases. (a) Effects of BCCs on bone resorption mediated by osteoblasts: molecules secreted by BCCs (TGF-β, IL-6, EGF, etc.) have been shown to activate osteoblasts to produce MMP-13 that degrades bone matrix and RANKL and RUNX-2, which stimulate osteoclasts to resorb bone; (b) direct effects of BCCs on osteoblasts differentiation: molecules secreted by BCCs (Galectin-3 and TGF-β1, IGF-2, PDGF) and BCC-expressed proteins (β-catenin) have been shown to regulate osteoblastic differentiation (affecting the expression of specific osteoblastic markers such as ALP, RUNX-2, etc.) through different pathways; (c) effects of molecules released by bone cells on BCCs: crosstalk between bone and cancer cells has been shown to promote an osteomimetic phenotype in BCCs (increasing the expression of typical bone markers such as osteocalcin OCN, osteopontin OPN, etc.) and TGF-β released by bone cells has been shown to activate Notch3 signaling and to promote BCCs growth; (d) direct effects of BCCs on osteoclastic differentiation: molecules secreted (CSF-1) or expressed (RANKL) by BCCs have been demonstrated to promote differentiation and activation of osteoclastic precursors towards mature osteoclasts. ↑: increased; ↓: decreased. Adapted by permission from [61] David, L.W.; Theresa, A.G. Cancer-associated muscle weakness: What’s bone got to do with it. BoneKEy Rep. 2015.
Mentions: Once rescued from the dormant state, BCCs are known to promote osteolytic bone metastases through the establishment of “vicious cycles” (amplifying feedback loops), which induce continuous bone resorption and release of pro-tumorigenic factors [58,59] (Figure 4). Beyond the well-studied RANKL-RANK-OPG pathway [59] which will be discussed in a separate section, other signaling programs are involved in the formation of an osteolytic milieu. Morrison and colleagues characterized through co-cultures (direct contact, Transwell, conditioned medium) of BCCs (MDA-1833) and osteoblasts which osteoclast-independent features are critical for bone metastases [60]. The authors found a significant increase in matrix metalloprotease (MMP)-13 mRNA production by osteoblasts when co-cultured with BCCs. The presence of MMP-13 was shown to increase the level of CCL-2, platelet-derived growth factor (PDGF)-C and serum amyloid A3 apolipoprotein SAA3, which can promote monocyte recruitment and osteoclast differentiation. Hence, BCCs produce factors, such as SAA3, that induce osteoblast secretion of MMP-13, which in turn activates the inducers of MMP-13, stimulating additional MMP-13 production and the generation of a vicious cycle (Figure 4a).

View Article: PubMed Central - PubMed

ABSTRACT

Advanced breast cancer frequently metastasizes to bone through a multistep process involving the detachment of cells from the primary tumor, their intravasation into the bloodstream, adhesion to the endothelium and extravasation into the bone, culminating with the establishment of a vicious cycle causing extensive bone lysis. In recent years, the crosstalk between tumor cells and secondary organs microenvironment is gaining much attention, being indicated as a crucial aspect in all metastatic steps. To investigate the complex interrelation between the tumor and the microenvironment, both in vitro and in vivo models have been exploited. In vitro models have some advantages over in vivo, mainly the possibility to thoroughly dissect in controlled conditions and with only human cells the cellular and molecular mechanisms underlying the metastatic progression. In this article we will review the main results deriving from in vitro co-culture models, describing mechanisms activated in the crosstalk between breast cancer and bone cells which drive the different metastatic steps.

No MeSH data available.


Related in: MedlinePlus