Abstract
BackgroundOsteosarcoma is a malignant tumor of bone and soft tissue in adolescents. Due to its tumor biological behavior pattern, osteosarcoma usually generates poor prognosis. Autophagy is an important self-defense mechanism in osteosarcoma.MethodsCell viability in IC50 testing and reverse assays was examined by the MTT assay. Cell apoptosis conditions were examined by flow cytometry, Hoechst 33,342 staining and apoptosis-related protein immunoblotting. Autophagy conditions were tested by autophagy-related protein immunoblotting, transmission electron microscopic observation and dual fluorescence autophagy flux detection. The possible targets of aloin were screened out by network pharmacology and bioinformatic methods. Osteosarcoma xenografts in nude BALB/c mice were the model for in vivo research on tumor suppression, autophagy induction, pathway signaling and toxicity tests. In vivo bioluminescence imaging systems, immunohistochemical assays, and gross tumor volume comparisons were applied as the main research methods in vivo.ResultsAloin induced osteosarcoma apoptosis in a dose-dependent manner. Its possible effects on the PI3K/AKT pathway were screened out by network pharmacology methods. Aloin increased autophagic flux in osteosarcoma by downregulating the PI3K/AKT pathway. Aloin promoted autophagic flux in the osteosarcoma cell lines HOS and MG63 in a dose-dependent manner by promoting autophagosome formation. Chloroquine reversed the apoptosis-promoting and autophagy-enhancing effects of aloin. Autophagy induced by starvation and rapamycin significantly enhanced the autophagic flux and apoptosis induced by aloin, which verified the role of the PI3K/AKT axis in the pharmacological action of aloin. Therapeutic effects, autophagy enhancement and regulatory effects on the PI3K/AKT/mTOR pathway were demonstrated in a nude mouse xenogeneic osteosarcoma transplantation model.ConclusionsAloin inhibited the proliferation of osteosarcoma by inhibiting the PI3K/AKT/mTOR pathway, increasing autophagic flux and promoting the apoptosis of osteosarcoma cells.
Highlights
Most osteosarcomas originate from primitive mesenchymal cells, which are derived from skeletal tissues [1, 2]
We considered the autophagy process, which is closely related to the Phosphatidylinositol 3 kinase (PI3K)/Protein kinase B (AKT)/Mammalian target of rapamycin (mTOR) pathway, to be the keystone to study the antitumor mechanism of aloin
Our experiments show that aloin-related PI3K/AKT/mTOR axis regulation inhibited the growth of tumor cells and induced autophagy
Summary
Most osteosarcomas originate from primitive mesenchymal cells, which are derived from skeletal tissues [1, 2]. Osteosarcoma mainly harms adolescents and results in poor prognosis, which causes great social harm, and there is a second smaller peak incidence in the elderly population [3, 4]. He et al Chinese Medicine (2021) 16:123. Exploring important aspects of the autophagy mechanism in osteosarcoma may provide new ideas and insights for the treatment of osteosarcoma. Autophagy is activated as a cytoprotective mechanism, providing nutrition and energy to tumor cells under starvation, increasing their resistance to common chemotherapy drugs.
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