The natural product pectolinarigenin exerts anti-inflammatory activity and anti-tumor effects, and exhibits different biological functions, particularly in autophagy and cell cycle regulation. However, the antineoplastic effect of pectolinarigenin on glioblastoma (GBM) remains unclear. In the present study, we found that pectolinarigenin inhibits glioblastoma proliferation, increases autophagic flux, and induces cell cycle arrest by inhibiting ribonucleotide reductase subunit M2 (RRM2), which can be reversed by RRM2 overexpression plasmid. Additionally, pectolinarigenin promoted RRM2 protein degradation via autolysosome-dependent pathway by increasing autophagic flow. RRM2 knockdown promoted the degradation of CDK1 protein through autolysosome-dependent pathway by increasing autophagic flow, thereby inhibiting the proliferation of glioblastoma by inducing G2/M phase cell cycle arrest. Clinical data analysis revealed that RRM2 expression in glioma patients was inversely correlated with the overall survival. Collectively, pectolinarigenin promoted the degradation of CDK1 protein dependent on autolysosomal pathway through increasing autophagic flux by inhibiting RRM2, thereby inhibiting the proliferation of glioblastoma cells by inducing G2/M phase cell cycle arrest, and RRM2 may be a potential therapeutic target and a prognosis and predictive biomarker in GBM patients.

Background: Since the mutation of isocitrate dehydrogenase 1 was confirmed to be different in the tumor microenvironment of multiple cancer types, several researchers have included it in the study of tumor-infiltrating immune cells. Interferon-stimulated exonuclease gene 20 (ISG20) plays a role in the modulation of immunity and inflammation, and its abnormally high expression is conducive for the progression of tumor malignancy. However, whether ISG20 is associated with isocitrate dehydrogenase 1 mutation during tumorigenesis and cancer progression remains unknown to date. Methods: TIMER2.0, ONCOMINE, GEPIA2, TCGA and CGGA were applied to assess the clinical significance of ISG20 and its correlation with tumor-infiltrating immune cells in glioma. cBioPortal and MethSurv databases were used to observe the genetic and DNA methylation changes of ISG20, respectively. Visualization of data was mostly achieved by R language. Quantitative real-time PCR (qRT-PCR) and Immunohistochemistry (IHC) was performed to evaluate the mRNA and protein expression.Results: ISG20 expression was significantly different in most cancers. However, when we combined ISG20 with isocitrate dehydrogenase 1 mutation, we found significant differences only in glioblastoma (GBM). The clinical values of ISG20 in glioblastoma showed that the ISG20 overexpression was strongly associated with a worse overall survival (OS). Additionally, ISG20 was altered in 9% of samples of patients with GBM, and ISG20 expression was negatively correlated with its DNA methylation level. More importantly, ISG20 expression was associated with macrophage alternatively activated (M2) polarization in glioblastoma. Conclusions: ISG20 overexpression is conducive to malignant phenotype but adverse to OS, suggesting that ISG20 is a potential therapeutic target and prognosis and predictive biomarker in patients with GBM.