Osteocytes are mechanosensitive bone cells, but little is known about their effects on tumor cells in response to mechanical stimulation. We treated breast cancer cells with osteocyte-derived conditioned medium(CM) an...Osteocytes are mechanosensitive bone cells, but little is known about their effects on tumor cells in response to mechanical stimulation. We treated breast cancer cells with osteocyte-derived conditioned medium(CM) and fluid flow-treated conditioned medium(FFCM) with 0.25 Pa and 1 Pa shear stress. Notably, CM and FFCM at 0.25 Pa induced the mesenchymal-to-epithelial transition(MET), but FFCM at 1 Pa induced the epithelial-to-mesenchymal transition(EMT). This suggested that the effects of fluid flow on conditioned media depend on flow intensity. Fluorescence resonance energy transfer(FRET)-based evaluation of Src activity and vinculin molecular force showed that osteopontin was involved in EMT and MET switching. A mouse model of tumorinduced osteolysis was tested using dynamic tibia loadings of 1, 2, and 5 N. The low 1 N loading suppressed tumor-induced osteolysis, but this beneficial effect was lost and reversed with loads at 2 and 5 N, respectively. Changing the loading intensities in vivo also led to changes in serum TGFβ levels and the composition of tumor-associated volatile organic compounds in the urine.Collectively, this study demonstrated the critical role of intensity-dependent mechanotransduction and osteopontin in tumorosteocyte communication, indicating that a biophysical factor can tangibly alter the behaviors of tumor cells in the bone microenvironment.展开更多
Osteocytes are the most abundant cells in bone,which is a frequent site of breast cancer metastasis.Here,we focused on Wnt signaling and evaluated tumor-osteocyte interactions.In animal experiments,mammary tumor cells...Osteocytes are the most abundant cells in bone,which is a frequent site of breast cancer metastasis.Here,we focused on Wnt signaling and evaluated tumor-osteocyte interactions.In animal experiments,mammary tumor cells were inoculated into the mammary fat pad and tibia.The role of Lrp5-mediated Wnt signaling was examined by overexpressing and silencing Lrp5 in osteocytes and establishing a conditional knockout mouse model.The results revealed that administration of osteocytes or their conditioned medium(CM)inhibited tumor progression and osteolysis.Osteocytes overexpressing Lrp5 or β-catenin displayed strikingly elevated tumor-suppressive activity,accompanied by downregulation of tumor-promoting chemokines and upregulation of apoptosis-inducing and tumor-suppressing proteins such as p53.The antitumor effect was also observed with osteocyte-derived CM that was pretreated with a Wnt-activating compound.Notably,silencing Lrp5 in tumors inhibited tumor progression,while silencing Lrp5 in osteocytes in conditional knockout mice promoted tumor progression.Osteocytes exhibited elevated Lrp5 expression in response to tumor cells,implying that osteocytes protect bone through canonical Wnt signaling.Thus,our results suggest that the Lrp5/β-catenin axis activates tumor-promoting signaling in tumor cells but tumor-suppressive signaling in osteocytes.We envision that osteocytes with Wnt activation potentially offer a novel cell-based therapy for breast cancer and osteolytic bone metastasis.展开更多
基金supported in part by funds from the breast cancer advocacy group 100 Voices of Hope, as well as by NIHR01 AR52144, R03 CA238555 (HY) and R01 AR053237 (AGR).NIHR01 AR52144,R03 CA238555 (HY) and R01 AR053237 (AGR)100 Voices of Hope (HY)。
文摘Osteocytes are mechanosensitive bone cells, but little is known about their effects on tumor cells in response to mechanical stimulation. We treated breast cancer cells with osteocyte-derived conditioned medium(CM) and fluid flow-treated conditioned medium(FFCM) with 0.25 Pa and 1 Pa shear stress. Notably, CM and FFCM at 0.25 Pa induced the mesenchymal-to-epithelial transition(MET), but FFCM at 1 Pa induced the epithelial-to-mesenchymal transition(EMT). This suggested that the effects of fluid flow on conditioned media depend on flow intensity. Fluorescence resonance energy transfer(FRET)-based evaluation of Src activity and vinculin molecular force showed that osteopontin was involved in EMT and MET switching. A mouse model of tumorinduced osteolysis was tested using dynamic tibia loadings of 1, 2, and 5 N. The low 1 N loading suppressed tumor-induced osteolysis, but this beneficial effect was lost and reversed with loads at 2 and 5 N, respectively. Changing the loading intensities in vivo also led to changes in serum TGFβ levels and the composition of tumor-associated volatile organic compounds in the urine.Collectively, this study demonstrated the critical role of intensity-dependent mechanotransduction and osteopontin in tumorosteocyte communication, indicating that a biophysical factor can tangibly alter the behaviors of tumor cells in the bone microenvironment.
基金This study was supported in part by funds from a breast cancer advocacy group,100 Voices of Hope(H.Y.)the Indiana University Precision Health Initiative(H.N.)NIH R01AR52144(H.Y.),R03CA238555(H.Y.),and R01AR053237(A.R.).
文摘Osteocytes are the most abundant cells in bone,which is a frequent site of breast cancer metastasis.Here,we focused on Wnt signaling and evaluated tumor-osteocyte interactions.In animal experiments,mammary tumor cells were inoculated into the mammary fat pad and tibia.The role of Lrp5-mediated Wnt signaling was examined by overexpressing and silencing Lrp5 in osteocytes and establishing a conditional knockout mouse model.The results revealed that administration of osteocytes or their conditioned medium(CM)inhibited tumor progression and osteolysis.Osteocytes overexpressing Lrp5 or β-catenin displayed strikingly elevated tumor-suppressive activity,accompanied by downregulation of tumor-promoting chemokines and upregulation of apoptosis-inducing and tumor-suppressing proteins such as p53.The antitumor effect was also observed with osteocyte-derived CM that was pretreated with a Wnt-activating compound.Notably,silencing Lrp5 in tumors inhibited tumor progression,while silencing Lrp5 in osteocytes in conditional knockout mice promoted tumor progression.Osteocytes exhibited elevated Lrp5 expression in response to tumor cells,implying that osteocytes protect bone through canonical Wnt signaling.Thus,our results suggest that the Lrp5/β-catenin axis activates tumor-promoting signaling in tumor cells but tumor-suppressive signaling in osteocytes.We envision that osteocytes with Wnt activation potentially offer a novel cell-based therapy for breast cancer and osteolytic bone metastasis.
