The FBXO32/ATR/ATM axis acts as a molecular switch to control the sensitivity of osteosarcoma cells to irradiation through its regulation of EXO1 expression.

Osteosarcoma (OS) is the most common primary bone cancer in children and adolescents. In clinical treatments, the insensitivity of OS to conventional radiotherapy regimens significantly contributes to poor patient prognosis and survival. EXO1 is responsible for DNA repair pathways and telomere maintenance. Meanwhile, ATM and ATR are considered switches because they can regulate the expression of EXO1. However, their expression and interaction in OS cells under irradiation (IR) remain unclear. This study aims to investigate the roles of FBXO32, ATM, ATR and EXO1 in OS radiotherapy insensitivity and poor patient prognosis and explore potential pathogenic mechanisms. Bioinformatics is employed to analyse differential gene expression and correlations with prognosis in OS. Cell counting kit 8 assay, clone formation assay, and flow cytometry are used to evaluate cell survival and apopotosis under IR. Co-IP assay is used to detect protein‒protein interactions. Bioinformatics analysis reveals that EXO1 is closely related to survival, apoptosis and poor prognosis in OS. Silencing of EXO1 suppresses cell proliferation and increases the sensitivity of OS cells. Molecular biological experiments show that ATM and ATR act as switches to regulate EXO1 expression under IR. Higher expression of EXO1, which is closely correlated with IR insensitivity and poorer prognosis, might be used as a prognostic indicator for OS. Phosphorylated ATM enhances the expression of EXO1, and phosphorylated ATR induces the degradation of EXO1. More importantly, FBXO32 degrades ATR via ubiquitination in a time-dependent manner. Our data may provide a reference for future research in the mechanisms, clinical diagnosis, and treatment of OS.

A rat model to study Blastocytis subtype 1 infections.

Blastocytis sp. is the most common enteric protozoan in human, but its pathogenesis is still unclear. To study the infectious effects of Blastocytis sp. on tissue damage, we orally challenged the Sprague Dawley (SD) rats with different doses of Blastocytis subtype1 (ST1) and examined the histological changes. We found that there was no difference of disease incidence among the Blastocytis ST1-infected groups challenged with different doses of the protozoan. Histological results showed that the lamina propria was infected by Blastocytis ST1 in the vacuolar form, along with the mucus membrane slough and inflammatory cell infiltration into the lamina propria. Compared to the uninfected group, the histological scores were significantly higher in the infected groups. However, groups infected with various doses of Blastocystis ST1 showed no difference in terms of histological scores. In conclusion, this study indicates that the SD rats can be easily infected with Blastocytis ST1 even with low dose of cysts, and the histopathological effects of the infection in the intestine of the infected rats show individual differences.

Inhibition of FNDC1 suppresses gastric cancer progression by interfering with Gßγ-VEGFR2 complex formation.

Gastric cancer (GC) is a prevalent digestive tract malignant tumor characterized by an insidious onset, ease of metastasis, rapid growth, and poor prognosis. Here, we report that fibronectin type III domain containing 1 (FNDC1) has high expression in GC and indicates poor outcomes in patients with GC. FNDC1 over-expression or knockdown promotes or inhibits tumorigenesis and metastasis, respectively. The expression of FNDC1 is upregulated by TWIST1, strengthening its interaction with Gßγ and VEGFR2. The formation of the trimers, TWIST1 plus Gßγ and VEGFR2, increases VEGFR2 phosphorylation and Gßγ trafficking, which activates RAS-MAPK and PI3K-AKT signaling, benefiting GC progression. In this study, we demonstrated that arsenite can efficiently suppress FNDC1 expression, attenuating the formation of the trimers and downstream pathways. Altogether, our results indicate that FNDC1 might be a promising target for clinical treatment and prognostic judgment, while FNDC1 inhibition by arsenite provides a new opportunity for overcoming this fatal disease.

Chondrocyte-derived Exosomal miR-195 Inhibits Osteosarcoma Cell Proliferation and Anti-Apoptotic by Targeting KIF4A in vitro and in vivo.

BACKGROUND: Osteosarcoma (OS) is a primary malignant tumor of the bone that occurs in adolescents and is characterized by a young age at onset, high malignancy, high rate of metastasis, and poor prognosis. However, the factors influencing disease progression and prognosis remain unclear. METHODS: In this study, we aimed to investigate the role of chondrocyte-derived exosomal miR-195 in OS. We used normal human chondrocytes to form miR-195-carrying exosomes to deliver miR-195 into OS cells. Xenograft tumor experiments were performed in mice intratumorally injected with exosomal miR-195. We found that kinesin superfamily protein 4A (KIF4A) promoted OS tumor progression and anti-apoptotic. RESULES: We demonstrated that miR-195 inhibited the expression of KIF4A by directly targeting its 3'-untranslated region. Moreover, we observed that exosomal miR-195 successfully inhibited OS cell tumor growth and antiapoptotic in vitro and suppressed tumor growth in vivo. CONCLUSION: Collectively, these results demonstrate that normal human chondrocyte-derived exosomal miR-195 can be internalized by OS cells and inhibit tumor growth and antiapoptotic by targeting KIF4A, providing a new direction for clarifying the molecular mechanism underlying OS development.

Kinesin superfamily proteins: roles in osteosarcoma.

Background: Osteosarcoma is a common bone tumor with extremely high malignancy, occurring mostly in children and adolescents. At present, the survival rate of osteosarcomas has made progress in some aspects; however, this can only be regarded as a partial success because substantial progress has not been made in the last few decades. Object: The kinesin superfamily is a group of proteins that play regulatory roles in various metabolic processes and are closely related to tumor metastasis. Increasing evidence shows that kinesins play key roles in the occurrence and development of human cancer. Purpose: This review summarizes the roles of the kinesin superfamily proteins in osteosarcoma and related functions.

[miR-125b suppresses the aerobic glycolysis of osteosarcoma HOS cells by downregulating the expression of hexokinase-2].

Objective To investigate the effect of miR-125b on the aerobic glycolysis of osteosarcoma HOS cells and its underlying mechanism. Methods Real-time quantitative PCR was performed to detect the expression of miR-125b in HOSB normal human osteoblast cells and HOS osteosarcoma cells. The glucose uptake rate was assessed with 3H-2 deoxyglucose (3H-2DG) and lactate production was tested with the kits to observe the effect of miR-125b-mimics on the aerobic glycolysis of osteosarcoma HOS cells. Hexokinase-2 (HK2) protein was detected by Western blot analysis. Dual luciferase reporter gene assay was used to determine whether HK2 was the direct target of miR-125b. Results Compared with HOSB normal human osteoblast cells, the expression of miR-125b was significantly lower in HOS cells. The glucose uptake and lactate production were downregulated in HOS cells transfected with miR-125b-mimics. Aerobic glycolysis of HOS cells was markedly inhibited. Protein level of HK2 was significantly inhibited in HOS cells transfected with miR-125b-mimics. Luciferase assay indicated that HK2 was the direct target of miR-125b. Conclusion miR-125b is down-regulated in HOS cells, and it inhibits the aerobic glycolysis of HOS cells by directly regulating the expression of HK2.