Tumor suppressor candidate 2 (TUSC2, also known as FUS1) was identified as a candidate tumor suppressor gene located in a region on chromosome 3p21.3 that undergoes allelic loss in lung and breast cancers. Loss of TUSC2 expression has been reported in various cancers and is associated with poor survival. Evidence to date indicates that TUSC2 behaves as a tumor suppressor in lung cancer; however, its role as a tumor suppressor in other tumor types has not been fully established. Since the mechanism for gliomagenesis is still unclear, we investigated the role of TUSC2 in the development and progression of glioblastoma (GBM), the most common and deadliest brain cancer in adults. Here, we found that forced TUSC2 expression suppressed neurosphere-forming capability of glioma stem cells, regardless of molecular subtypes. Forced expression of TUSC2 in GBM cell lines inhibited their ability to form colonies and neurospheres. To further determine whether TUSC2 plays a tumor suppressive role in GBM, we knocked down TUSC2 expression in TUSC2-expressing GBM cells using siRNA and CRISPR/Cas9, and found TUSC2 knockdown to significantly enhance neurosphere formation of GBM cells. Using an orthotopic GBM xenograft mouse model, we further observed that CRISPR/Cas9-mediated TUSC2 knockout significantly promoted the intracranial growth of GBM tumors. To gain inisghts into the mechanisms underlying TUSC2’s tumor suppressive function in GBM, we conducted RNA-Seq using control and TUSC2-knockout GBM cell lines, and identified a number of genes whose expression was altered in response to TUSC2 loss. Ongoing studies are being conducted to validate idenified genes, and elucidate their involvement in gliomagenesis and GBM progression. Furthermore, we speculated that TUSC2 may interact with cellular proteins leading to tumor suppression. To test this hypothesis, we conducted protein interactome analysis using immunoprecipitaton followed by mass spectrometry in which cell lysates from GBM cells and human astrocytes (a cell-of-origin for GBM) were used. This study has identified approximately 40 proteins that differentially interact with TUSC2 in GBM cells versus human astrocytes. Roles of these TUSC2-interacting proteins in GBM suppression and gliomagenesis are being examined in onging studies. Finally, we have generated conditional TUSC2-knockout mice to further address the role that TUSC2 plays in gliomagenesis. Collectively, these findings support a novel role that TUSC2 plays in GBM progression and gliomagenesis, thereby advancing our understanding of GBM pathobiology.
Citation Format: Tadas K. Rimkus, Dongqin Zhu, Richard L. Carpenter, Ivy Paw, Austin Arrigo, Sherona Sirkisoon, Daniel Doheny, Noah Aguayo, Jingyun Lee, Guangxu Jin, Eric Spooner, Boris Pasche, Waldemar Debinski, Hui-Wen Lo. Roles of tumor suppressor candidate 2 (TUSC2) in glioblastoma progression and gliomagenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3481.