Bone-homing metastatic breast cancer cells impair osteocytes' mechanoresponse in a 3D loading model

Mechanical Loading of Osteocytes via Oscillatory Fluid Flow Regulates Early-Stage PC-3 Prostate Cancer Metastasis to Bone

Bone metastasis is a devastating complication for advanced-stage prostate cancer patients. Osteocytes, as the primary mechanosensors in bone, have been recently investigated for their role in prostate cancer bone metastasis. In vivo findings show potential benefits of exercise as a preventative intervention strategy for bone metastasis. In contrast, in vitro studies indicate direct prostate cancer-osteocyte interactions under mechanical loading promote prostate cancer growth and migration. These findings are not consistent with in vivo results and may be more reflective of late-stage metastatic colonization. Here, the role of flow-stimulated osteocytes during early-stage bone metastasis, particularly prostate cancer-endothelial interactions, is examined. Flow-stimulated osteocytes reduce PC-3 prostate cancer cell adhesion and trans-endothelial migration by 32.3% and 40% compared to static controls. Both MLO-Y4 and primary murine osteocytes under mechanical loading regulate the extravasation distance and frequency of PC-3 cells in a microfluidic tissue model. Application of vascular cellular adhesion molecule 1 (VCAM-1) neutralizing antibody abolishes the difference in cancer cell adhesion, extravasation frequency, and number of extravasated PC-3 cells between static and flow-stimulated groups. Taken together, the role of osteocytes in early-stage bone metastasis using PC-3 cells as a model is demonstrated here, bridging the gap between in vitro and in vivo findings.

High-fidelity computational fluid dynamics modeling to simulate perfusion through a bone-mimicking scaffold

Breast cancer cells sense shear stresses in response to interstitial fluid flow in bone and induce specific biological responses. Computational fluid dynamics models have been instrumental in estimating these shear stresses to relate the cell mechanoresponse to exact mechanical signals, better informing experiment design. Most computational models greatly simplify the experimental and cell mechanical environments for ease of computation, but these simplifications may overlook complex cell-substrate mechanical interactions that significantly change shear stresses experienced by cells. In this paper, we construct a high-fidelity model, i.e., a digital twin, of a bone-mimicking scaffold experiencing fluid stresses from a custom perfusion bioreactor by creating a stabilized multi-domain finite element formulation that accounts for physical components of the bioreactor and true flow boundaries. Our goals include determination of a range of applied flow rates that result in physiological wall shear stresses, evaluation of wall shear stress sensitivity to scaffold fabrication, and validation of our bioreactor set-up for applying physiologically-relevant fluid stresses. This work will provide us with a more structured framework to study breast cancer mechanobiology in bone metastasis. Accurate shear stress estimations will allow us to understand how in vitro models of anabolic loading in bone affect the breast cancer cell mechanoresponse.

Role of the osteocyte in bone metastasis - The importance of networking

Metastatic bone disease is a complex condition resulting from the migration and colonization of cancer cells from their primary site to the bone microenvironment, where they typically develop a metastatic niche. Osteocytes, the most abundant cells in bone tissue and the master regulators of bone remodelling, are increasingly thought to play a crucial role in this process through intricate interactions with cancer cells. This review covers the recent progress made in exploring the multifaceted interactions between osteocytes and cancer cells in the metastatic microenvironment, highlighting the importance of signalling networks in bone metastases. Though these interactions are particularly complex, the renewed focus of researchers on osteocytes within the last 5 years has uncovered multiple new potential molecular mechanisms underlying osteocyte-mediated regulation of cancer cell survival, proliferation, and invasion. A number of key papers will be discussed in detail, emphasizing the significance of signalling pathways and molecular crosstalk, and exploring potential therapeutic strategies targeting osteocyte-cancer cell interactions to improve patient treatment and outcomes.