Synergistic Antitumor Effect of Combined Radiotherapy and Engineered Salmonella typhimurium in an Intracranial Sarcoma Mouse Model

Intracranial sarcoma is an uncommon aggressive cancer with a poor prognosis and a high recurrence rate. Although postoperative adjuvant radiotherapy (RT) is the most recommended treatment strategy, it does not significantly improve survival rates. In this study, we used an attenuated Salmonella typhimurium strain engineered to secrete Vibrio vulnificus flagellin B (SLpFlaB) as an immunotherapy to assist with the antitumor effects of RT on intracranial sarcoma. In vitro, the expression of γH2AX and cleaved caspase-3 was analyzed by Western blot. In vivo detection of SLpFlaB colonization time in tumors was measured using an in vivo imaging system (IVIS). Tumor growth delay and elimination were demonstrated in an intracranial mouse model, and the distribution of macrophages, M1 macrophages, and CD8⁺ cells after treatment was measured using FACS analysis. Our findings in vitro suggest that combination therapy increases S-180 radiosensitivity, the expression of DNA double-strand breaks, and programmed cell death. In vivo, combination treatment causes intracranial sarcoma to be eliminated without tumor recurrence and redistribution of immune cells in the brain, with data showing the enhanced migration and infiltration of CD8⁺ T cells and macrophages, and an increased proportion of M1 macrophage polarization. Compared to RT alone, the combination therapy enhanced the radiosensitivity of S-180 cells, promoted the recruitment of immune cells at the tumor site, and prevented tumor recurrence. This combination therapy may provide a new strategy for treating intracranial sarcomas.

A systematic review of the clinicopathological features and prognostic outcomes of DICER1-mutant malignant brain neoplasms

OBJECTIVE

DICER1-mutant malignant brain neoplasms are very rare tumors, and published data have relied on case reports or small case series. In this review, the authors aimed to systematically summarize the types and distribution patterns of DICER1 mutations, clinicopathological characteristics, and prognostic outcomes of these tumors.

METHODS

The authors searched PubMed and Web of Science for relevant studies. They included studies if they provided individual patient data of primary malignant brain tumors carrying DICER1 mutations.

RESULTS

The authors found 16 studies consisting of 9 embryonal tumors with multilayered rosettes (ETMRs), 30 pineoblastomas, 52 primary intracranial sarcomas, and 27 pituitary blastomas. Pineoblastoma, ETMR, and pituitary blastoma were more likely to carry DICER1 germline mutations, while only a small subset of primary intracranial sarcomas harbored these mutations (p < 0.001). Nearly 80% of tumors with germline mutations also had another somatic mutation in DICER1. ETMR and primary intracranial sarcoma were associated with an increased risk for tumor progression and relapse compared with pituitary blastoma and pineoblastoma (p = 0.0025), but overall survival (OS) was not significantly different. Gross-total resection (GTR) and radiotherapy administration were associated with prolonged OS.

CONCLUSIONS

ETMR, pineoblastoma, primary intracranial sarcoma, and pituitary blastoma should be considered rare phenotypes of the DICER1 syndrome, and families should be counseled and screened for associated tumors. ETMR and primary intracranial sarcoma had a higher risk of relapse. GTR and radiotherapy appeared to improve the OS of patients with DICER1-mutant malignant intracranial tumors.