SLC25A22 Promotes Proliferation And Metastasis Of Osteosarcoma Cells By Regulating PTEN Signaling Pathway

ObjectiveOsteosarcoma is the most common primary bone malignancy in children and adolescents.Prior to 1970,for the treatment of limbless osteosarcoma without amputation,the 5-year survival rate was still less than 20%.After considerable progress in MRI imaging,limb salvage surgery,and neoadjuvant chemotherapy,the clinical diagnosis and treatment of osteosarcoma has once again entered a plateau.Because the mechanism of cell proliferation,metastasis,and neovascularization of osteosarcoma is extremely complex and involves many signal transduction pathways,with the in-depth understanding of the pathogenesis of osteosarcoma,the emergence of new drugs,new methods,and further improvement in prognosis are still needed.MethodsFirstly,the expression of SLC25A22 mRNA and protein in osteosarcoma and paracancerous tissures was preliminarily detected.Forty pairs of osteosarcoma and paracancerous tissures and their clinical features were colletcted,the expression levels of SLC25A22 in 40 pairs of tissue specimens was detected by immunohistochemistry,and the correlation between SLC25A22 levels and clincal features were analzed,besides,Kaplan-Meier survival analysis was performed to analyze survival distribution.Next,we slected U2 OS,Saos-2 and HOS cells as research models,and performed shRNA knockown of LSC25A22 gene in U2 OS and Saos-2 cells,and performed overexpression of SLC25A22 in HOS cells.MTT,clone formation,wound healing test and transwell were performed to evelate the ability of osteosarcoma cells to proliferate and transfer,cell cycle and apotosis of osteosarcoma cell lines were detected via flow cytometry.The experimental method for subcutaneous transplantation of tumors was to implant osteosarcoma cells into the skin of BALB/c nude mice,for the purpose to assess the effect of SLC25A22 on the proliferation and apoptosis of osteosarcoma.The lung metastasis model was established by injecting the treated Saos-2 cells into the BALB/c mice via the tail vein,for the purpose to assess the effect of SLC25A22 on the metastasis of osteosarcoma.Western blot was used to detect the changes of cell cycle and apoptosis-related proteins.STRING was used to predict SLC25A22 interacting proteins and possible signaling pathways.Results(1)The mRNA level of SLC25A22 was highly expressed in osteosarcoma tissues compared to adjacent tissues,besides,we lysed tissue specimens and examined the protein levels of SLC25A22 by immunohistochemistry and found that SLC25A22 protein is highly expressed in tumor tissues,the difference is statistically significant.We divided the 40 tumor tissues into high-expression group and low-expression group according to immunohistochemistry scores,the results showed that SLC25A22 was closely related to the patient’s ennecking stage and distal metastasis(P=0.0011 and P=0.003),but not related to the patient’s gender,histology and tumor location;however,higher SLC25A22 expression indicated poor prognosis,the patients with high SLC25A22 expression had more death than those with low SLC25A22 expression after 6 year follow-up.(2)Next,we found that SLC25A22 is highly expressed in U2 OS and Saos-2 cells,and is low in 143 B and HOS cells;Knockdown of SLC25A22 by shRNA significantly slowed cell proliferation and clone formation,however,SLC25A22 overexpression promoted cell proliferation and clone formation;Knockdown or overexpression of SLC25A22 could changed the E-cadherin、Vimentin and MMP-9 levels;Tumor forming and pulmonary metastasis ability of SLC25A22 knockdown cells was significantly reduced,and the tumor size and weight of the tumors were significantly smaller than those of the control group,in contrast,the HOS cells tumorigenicity,tumor volume and weight increased after SLC25A22 overexpression,and the pulmonary metastasis ability increased as well.(3)The expression of PTEN in SLC25A22 knockdown U2 OS and Saos-2 cells increased,and the expression of p-AKT and p-FAK decreased,and the SLC25A22 expression of osteosarcoma tissues was closely related to PTEN expression.ConculsionSLC25A22 was highly expressed in osteosarcoma and was associated with clinical stage and disatant metastasis;SLC25A22 promotes the proliferation,metastasis and invastion of osteosarcoma;SLC25A22 promotes proliferation and metastasis of osteosarcoma cells by regulating PTEN signaling pathway.