Complement C3a activates osteoclasts by regulating the PI3K/PDK1/SGK3 pathway in patients with multiple myeloma

Objective:Myeloma bone disease(MBD)is the most common complication of multiple myeloma(MM).Our previous study showed that the serum levels of C3/C4 in MM patients were significantly positively correlated with the severity of bone disease.However,the mechanism of C3 a/C4 a in osteoclasts MM patients remains unclear.Methods:The formation and function of osteoclasts were analyzed after adding C3 a/C4 a in vitro.RNA-seq analysis was used to screen the potential pathways affecting osteoclasts,and the results were verified by Western blot,q RT-PCR,and pathway inhibitors.Results:The osteoclast area per view induced by 1μg/m L(mean±SD:50.828±12.984%)and 10μg/m L(53.663±12.685%)of C3 a was significantly increased compared to the control group(0μg/m L)(34.635±8.916%)(P<0.001 and P<0.001,respectively).The relative m RNA expressions of genes,OSCAR/TRAP/RANKL/cathepsin K,induced by 1μg/m L(median:5.041,3.726,1.638,and 4.752,respectively)and 10μg/m L(median:5.140,3.702,2.250,and 5.172,respectively)of C3 a was significantly increased compared to the control group(median:3.137,2.004,0.573,and 2.257,respectively)(1μg/m L P=0.001,P=0.003,P<0.001,and P=0.008,respectively;10μg/m L:P<0.001,P=0.019,P<0.001,and P=0.002,respectively).The absorption areas of the osteoclast resorption pits per view induced by 1μg/m L(mean±SD:51.464±11.983%)and 10μg/m L(50.219±12.067%)of C3 a was also significantly increased(33.845±8.331%)(P<0.001 and P<0.001,respectively)compared to the control.There was no difference between the C4 a and control groups.RNA-seq analysis showed that C3 a promoted the proliferation of osteoclasts using the phosphoinositide 3-kinase(PI3 K)signaling pathway.The relative expressions of PIK3 CA/phosphoinositide dependent kinase-1(PDK1)/serum and glucocorticoid inducible protein kinases(SGK3)genes and PI3 K/PDK1/p-SGK3 protein in the C3 a group were significantly higher than in the control group.The activation role of C3 a in osteoclasts of MM patients was reduced by the SGK inhibitor(EMD638683).Conclusions:C3 a activated osteoclasts by regulating the PI3 K/PDK1/SGK3 pathways in MM patients,which was reduced using a SGK inhibitor.Overall,our results identified potential therapeutic targets and strategies for MBD patients。

Overexpressed Cyclin D1 and CDK4 proteins are responsible for the resistance to CDK4/6 inhibitor in breast cancer that can be reversed by PI3K/mTOR inhibitors

CDK4/6 inhibitors are the standard treatment in advanced HR+/HER2-breast cancer patients.Nevertheless,the resistance to CDK4/6 inhibitors is inevitable and the strategies to overcome resistance are of great interest.Here,we show that the palbociclibresistant breast cancer cells expressed significantly higher levels of Cyclin D1 and CDK4 proteins because of upregulated protein synthesis.Silencing Cyclin D1 or CDK4 led to cell cycle arrest while silencing Cyclin E1 or CDK2 restored the sensitivity to palbociclib.Furthermore,PI3K/mTOR pathway was hyper-activated in palbociclib-resistant cells,leading to more phosphorylated 4E-BP1 and higher levels of Cyclin D1 and CDK4 translation.Targeting PI3K/mTOR pathway with a specific PI3Kαinhibitor(BYL719)or an mTOR inhibitor(everolimus)reduced the protein levels of Cyclin D1 and CDK4,and restored the sensitivity to palbociclib.The tumor samples expressed significantly higher levels of Cyclin D1,CDK4,p-AKT and p-4E-BP1 after progression on palbociclib treatment.In conclusion,our findings suggest that overexpressed Cyclin D1 and CDK4 proteins lead to the resistance to CDK4/6 inhibitor and PI3K/mTOR inhibitors are able to restore the sensitivity to CDK4/6 inhibitors,which provides the biomarker and rationale for the combinational use of CDK4/6 inhibitors and PI3K/mTOR inhibitors after CDK4/6 inhibitor resistance in breast cancer.