USP7 promotes the malignant progression of osteosarcoma through the KPNA2/PKLR axis

Osteosarcoma, a common primary bone malignancy, poses significant challenges in clinical treatment due to its high metastatic potential and resistance to chemotherapy. The karyopherin subunit alpha 2 (KPNA2) is a member of the karyopherin family and has been implicated in the regulation of various cellular processes. However, the role of KPNA2 in osteosarcoma development and progression remains unclear.

The expression levels of KPNA2 and pyruvate kinase L/R (PKLR) mRNA were assessed using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Protein expression of KPNA2, ubiquitin-specific peptidase 7 (USP7), and PKLR was determined via western blotting. Cell viability, proliferation, apoptosis, invasion, and migration were evaluated using CCK-8, EdU, flow cytometry, transwell invasion, and wound-healing assays, respectively. Glucose consumption and lactate production were measured using colorimetric assays. The interaction between USP7 and KPNA2 was identified through co-immunoprecipitation (Co-IP) and immunofluorescence co-localization assays. In vivo experiments were conducted to validate the effects of KPNA2 silencing and PKLR overexpression on osteosarcoma cell growth. The positive expression rates of Ki67 and PKLR were assessed using immunohistochemistry (IHC) assays.

KPNA2 expression was upregulated in osteosarcoma tissues and cells. Silencing KPNA2 suppressed osteosarcoma cell proliferation, invasion, migration, and glycolysis, while inducing apoptosis. USP7 stabilized KPNA2 through its deubiquitinating activity, and USP7 silencing inhibited the malignant phenotypes of osteosarcoma cells by regulating KPNA2. Additionally, KPNA2 upregulated PKLR expression, and overexpression of PKLR mitigated the effects of KPNA2 silencing on the malignant progression of osteosarcoma cells both in vitro and in vivo.

The deubiquitination of KPNA2 by USP7 promoted the malignant progression of osteosarcoma by increasing PKLR expression. This study highlights the clinical significance of targeting the KPNA2-USP7-PKLR axis as a potential therapeutic strategy for the treatment of osteosarcoma.