Glioblastoma (GBM) is the most aggressive type of cancer. Its current first‐line postsurgery regimens are radiotherapy and temozolomide (TMZ) chemotherapy, both of which are DNA damage‐inducing therapies but show very limited efficacy and a high risk of resistance. There is an urgent need to develop novel agents to sensitize GBM to DNA‐damaging treatments. Here it is found that the triterpene compound stellettin B (STELB) greatly enhances the sensitivity of GBM to ionizing radiation and TMZ in vitro and in vivo. Mechanistically, STELB inhibits the expression of homologous recombination repair (HR) factors BRCA1/2 and RAD51 by promoting the degradation of PI3K α through the ubiquitin‐proteasome pathway; and the induced HR deficiency then leads to augmented DNA damage and cell death. It is further demonstrated that STELB has the potential to rapidly penetrate the blood‐brain barrier to exert anti‐GBM effects in the brain, based on zebrafish and nude mouse orthotopic xenograft tumor models. The study provides strong evidence that STELB represents a promising drug candidate to improve GBM therapy in combination with DNA‐damaging treatments.

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A novel method for the synthesis of 3-unsubstituted oxindoles by the reductive dephosphorylation of 3-(diethylphosphoryloxy)oxindoles with hydroiodic acid was developed. This synthetic strategy involved a twostep procedure including a phospha-Brook rearrangement of isatins with diethyl phosphite and a reductive dephosphorylation of the phosphorylated oxindoles.

CS5931 is a novel anticancer agent isolated from the sea squirt Ciona savignyi. However, its content in the species is very low, and developing a novel approach for production of the polypeptide is promising. In the present study, we expressed and purified the polypeptide from E. coli, and the fermentation conditions were studied using response surface methodology. The yield of CS5931 was increased from 2.0 to 7.5 mg/L. The denaturing and renaturation conditions were also studied. Using the optimized renaturation condition, the anticancer activity of refolding CS5931 was increased significantly; the value of IC50 was decreased from 23.2 to 11.6 μM. In vivo study using xenograft nude mice bearing HCT116 cancer cells revealed that CS5931 was able to inhibit the growth of tumor significantly. The study provides a useful approach for obtaining enough amount of CS5931 for further study. This study is also important for developing the polypeptide as a novel anticancer agent.

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