Selenocysteine inhibits human osteosarcoma cells growth through triggering mitochondrial dysfunction and ROS-mediated p53 phosphorylation

Osteosarcoma represents the most common primary malignant bone tumor in children and adolescents, which shows severe resistance toward standard chemotherapy because of high invasive capacity and growing incidence. Selenocysteine (SeC) is a naturally available Se-containing amino acid that displays splendid anticancer activities against several human tumors. However, little information about SeC-induced growth inhibition against human osteosarcoma is available. Herein, the anticancer efficiency and underlying mechanism of SeC against human osteosarcoma were evaluated in vitro and in vivo. The results revealed that SeC significantly inhibited MG-63 human osteosarcoma cells growth in vitro through induction of S-phase arrest and apoptosis, as reflected by the decrease of cyclin A and CDK-2, PARP cleavage, and caspases activation. SeC treatment also resulted in mitochondrial dysfunction through affecting Bcl-2 family expression. Moreover, SeC triggered p53 phosphorylation by inducing reactive oxygen species (ROS) overproduction. ROS inhibition effectively blocked SeC-induced cytotoxicity and p53 phosphorylation. Importantly, MG-63 human osteosarcoma xenograft growth in nude mice was significantly suppressed in vivo through triggering apoptosis and p53 phosphorylation. These results indicated that SeC had the potential to inhibit human osteosarcoma cells growth in vitro and in vivo through triggering mitochondrial dysfunction and ROS-mediated p53 phosphorylation, which validated the potential application of Se-containing compounds in treatment of human osteosarcoma.

Effects of the Long Non-Coding RNA HOST2 On the Proliferation, Migration, Invasion and Apoptosis of Human Osteosarcoma Cells

Background/Aims: This study aimed to explore the effects of the long non-coding RNA HOST2 (lnc-HOST2) on the proliferation, migration, invasion and apoptosis of osteosarcoma cells. Methods: Osteosarcoma tissues and adjacent normal tissues from 52 patients were selected. Human osteosarcoma cell lines (SaOS2, HOS, U2OS and MG-63) were collected and cultured; MG-63 cells had the highest lnc-HOST2 expression and thus were used in subsequent experiments. Then, MG-63 cells were transfected and divided into the blank (no transfection), si-CON (transfected with negative control siRNA) and si-lnc-HOST2 (transfected with small interference lnc-HOST2 siRNA) groups. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to determine the expression of lnc-HOST2 in primary tissues and cells. Cell growth was detected using the CCK-8 and colony formation assays. Cell doubling time was detected. Cell migration and invasion were observed using the scratch test and Transwell assays. Cell apoptosis and cell cycle progression of osteosarcoma cells were detected using flow cytometry with annexin V/PI double staining and PI staining, respectively. Results: The level of lnc-HOST2 expression in the si-lnc-HOST2 group was significantly decreased compared to that in the blank and si-CON groups. The OD values in the si-lnc-HOST2 group were significantly lower than those in the blank and si-CON groups. Compared to the blank and si-CON groups, the si-lnc-HOST2 group presented significant decreases in the colony number and healing rates after scratching. The number of invasive cells in the si-lnc-HOST2 group was significantly less than that in the blank and si-CON groups. In the si-lnc-HOST2 group, the cell cycle was mainly halted in the G1 phase, and the apoptosis rate and doubling time in this group were significantly higher than those in the blank group and si-CON group. Conclusions: Inhibition of lnc-HOST2 could suppress the proliferation, migration, and invasion and promote the apoptosis of osteosarcoma cells.

Pressure-Induced Electronic Transition in Black Phosphorus

In a semimetal, both electrons and holes contribute to the density of states at the Fermi level. The small band overlaps and multiband effects engender novel electronic properties. We show that a moderate hydrostatic pressure effectively suppresses the band gap in the elemental semiconductor black phosphorus. An electronic topological transition takes place at approximately 1.2 GPa, above which black phosphorus evolves into a semimetal state that is characterized by a colossal positive magnetoresistance and a nonlinear field dependence of Hall resistivity. The Shubnikov-de Haas oscillations detected in magnetic field reveal the complex Fermi surface topology of the semimetallic phase. In particular, we find a nontrivial Berry phase in one Fermi surface that emerges in the semimetal state, as evidence of a Dirac-like dispersion. The observed semimetallic behavior greatly enriches the material property of black phosphorus and sets the stage for the exploration of novel electronic states in this material.

MicroRNA-150 Inhibits Cell Invasion and Migration and Is Downregulated in Human Osteosarcoma

miR-150 expression in osteosarcoma (OS) cell lines and human osteoblast cells was detected, and OS cell models were transfected with exogenous miR-150 to investigate its role in cell proliferation, invasion, and apoptosis. Our results showed that miR-150 expression in OS cells (MG63, Saos-2, SOSP-9607, and U2OS) was significantly lower compared to the osteoblast hFOB1.19 cell line (all p < 0.01). The expression level of miR-150 in MG63 cells that were transfected with exogenous miR-150 mimics was markedly upregulated, while the miR-150 expression level in the inhibitor group was significantly downregulated (both p < 0.01). Similar results were also found in SOSP-9607 cells. Importantly, exogenous miR-150 expression stimulated cell apoptosis and inhibited proliferation, invasion, and migration. A luciferase reporter assay displayed that miR-150 also regulated Sp1 expression by targeting its 3'-UTR, and qRT-PCR and Western blotting showed that elevated levels of miR-150 may reduce Sp1 protein expression. The mRNA and protein levels of Sp1 were upregulated after transfection with a Sp1-expression plasmid and partially reversed the inhibitory effects of miR-150 on cell proliferation, invasion, and metastasis in MG63 and SOSP-9607 cells, as well as promoted cell apoptosis. In conclusion, miR-150 inhibits cell proliferation, invasion, and metastasis and stimulates cell apoptosis by regulating the expression of Sp1. Therefore, miR-150 may be a potential clinical target for the treatment of OS patients.