Abstract 6735: Identifying the role of novel driver TREX subcomplex in medulloblastoma growth and progression
Authors: Abdulsahib Shahad M. , Timilsina Santosh , Rao Manjeet 
Published: April 2023

Background: Medulloblastoma (MB) is the most common malignant brain cancer in children. Despite the progress made in treating MB, the 5-year survival rate for high-risk tumors remains poor and risk of recurrence within 2 years of treatment is still high. Almost all MB deaths are attributed to leptomeningeal dissemination (LMD) as MB spreads exclusively through cerebrospinal fluid (CSF) to spinal and intracranial leptomeninges. Unfortunately, patients who do survive have reduced quality of life because of the highly toxic side effects of radiation and chemotherapy. Those facts underline the importance of identifying new drivers of medulloblastoma and understanding the mechanism by which those drivers may promote medulloblastoma. Towards that goal, I aim to identify novel drivers of MB and characterize novel therapies for treating (LMD-MB). Using an unbiased genome-wide screen, we discovered THO complex as one of the highly differentially expressed genes that may provide survival advantage to MB cells. THO is a subcomplex of the TREX complex, is known to couple mRNA transcription, processing and nuclear export associated with spliced mRNA.

Methods: Recent work in our lab utilizing various genomes and proteomics identified THO complex as a possible target. Transfection agents were used to knockdown part of the TREX subcomplex expression in several MB cells. Western blot and qPCR verified the knockdown. The cell viability was measured using Cell Titer Glo, and cell proliferation was evaluated with an IncuCyte. Cells were seeded at a low density and cultured until colonies formed then were fixed and stained with crystal violet. In addition, cells were seeded in a serum-free medium and allowed to migrate to complete media before being fixed and stained. Flow cytometry was used to examine cells for apoptosis and cell cycle. For apoptosis, cells were stained with propidium iodide (PI) and Annexin FTIC, and for the cell cycle, cells were stained and followed by PI.

Results: The Cancer Dependency Map (Dep-Map) meta-analysis revealed that MB strongly depends on The TREX subcomplex. Significantly, increased THO complex expression was associated with a worse overall survival rate in MB patients. Our findings indicated that part of the TREX subcomplex depletion decreased MB cell survival in the short- and long-term proliferation, migration, and invasion. Furthermore, part of TREX subcomplex depletion promoted apoptosis in MB cells. I propose that THO complex may be a new driver of MB and that strategies aiming to reduce part of TREX subcomplex levels and activity might benefit MB patients.

Conclusion: TREX subcomplex parts depletion has been demonstrated to reduce MB cells in vitro in various experiments. Future research, including CRISPR-CAS9-based knockout models, single-cell sequencing, and metabolomics, will further elucidate the mechanism(s) and utility of the TREX subcomplex axis in LMD-MB.

Citation Format: Shahad M. Abdulsahib, Santosh Timilsina, Manjeet Rao. Identifying the role of novel driver TREX subcomplex in medulloblastoma growth and progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6735.