N6-Methyladenosine modification of the TRIM7 positively regulates tumorigenesis and chemoresistance in osteosarcoma through ubiquitination of BRMS1

Abstract

Background Metastasis is the leading cause of death in patients with osteosarcoma. Some of these patients fail to respond to chemotherapy and die of metastasis within a short period. Therefore, it is important to identify novel biomarkers to improve the diagnosis and treatment of osteosarcoma. TRIM7 is a member of the tripartite motif (TRIM) family protein that is involved in various pathological conditions including cancer; however, its role in osteosarcoma remains elusive. Methods Cell proliferation, invasion and migration were measured by CCK-8 and Transwell. Immunoprecipitation and mass spectrometry analysis were used to identify candidate proteins associated with TRIM7. Immunoprecipitation, immunofluorescence, pull down and ubiquitination assay were performed to examine the regulation between TRIM7 and its candidate protein. m6A modification of TRIM7 was measured by RNA immunoprecipitation. Findings TRIM7 expression was upregulated in osteosarcoma tissues and was an independent risk factor in predicting poor prognosis. TRIM7 regulates osteosarcoma cell migration and invasion through ubiquitination of breast cancer metastasis suppressor 1 (BRMS1). Moreover, chemoresistance was readily observed in osteosarcoma cells and in patient-derived xenograft (PDX) mice with higher TRIM7 levels. Loss of TRIM7 m6A modification was observed in osteosarcoma tissues. METTL3 and YTHDF2 were the main factors involved in the aberrant m6A modification of TRIM7. Interpretation Overall, our findings show that TRIM7 plays a key role in regulating metastasis and chemoresistance in osteosarcoma through ubiquitination of BRMS1. Funding This work was financially supported by grants of NSFC (81001192, 81672658 and 81972521) and National Key Research Project of Science and Technology Ministry (2016YFC0106204).

Regulatory Role of N6-methyladenosine (m6A) Modification in Osteosarcoma

“…METTL3/14 also plays an important role in modulating the chemoresistance of osteosarcoma. METTL3 and METTL14 decrease the RNA level of tripartite motif 7 (TRIM7), while the upregulation of TRIM7 can increase metastasis and the chemoresistance of osteosarcoma by regulating ubiquitination of breast cancer metastasis suppressor 1 (BRMS1) (69). The transcriptome-wide m 6 A sequencing result of chemoresistant osteosarcoma stem cells revealed that over-expression of METTL3 and low METTL14 expression are associated with doxorubicin chemoresistance and stemness of osteosarcoma cells (70).…”

“…Additionally, HNRNPC and HNRNPA2B1 are found only in the nucleus (63). YTHDF2 can directly bind to the 3'-UTR of TRIM7 mRNA and negatively regulate the expression of TRIM7 in osteosarcoma HOS and MG63 cells (69). ELAVL1 (also known as HuR) is a recently discovered m 6 A reader, which is located in the nucleus.…”

“…On the other hand, m 6 A may also serve as a novel therapeutic target in osteosarcoma. M 6 A modification is pivotal in almost all pathophysiological processes of osteosarcoma, including tumorigenesis, invasion, and metastasis (64,68,69,71). The small molecule inhibitor of m 6 A regulators has been regarded as a kind of potential anti-cancer agent (91,92).…”

“…METTL3 and ALKBH5 expression levels are upregulated in doxorubicin-resistant osteosarcoma cells, while METTL14 expression is downregulated (70). YTHDF2 knockdown can significantly increase the expression of TRIM7 and cause resistance to doxorubicin and methotrexate treatment (69). Therefore, targeting dysregulated m 6 A enzymes represents an attractive strategy for cancer therapy.…”

No Association Between FTO Gene Polymorphisms and Central Nervous System Tumor Susceptibility in Chinese Children

“… 28 The aberrant m 6 A modifications mediated by FTO expression contributed to the development of cancers. 29–31 m 6 A RNA methylation regulators are crucial participants in the malignant progression of CNS tumor. FTO may preferentially mediate demethylation of different methylation targets in CNS tumor.…”