Abstract A024: Cellular and molecular characterization of cancer stem-like cells isolated from the sub-ventricular zone of glioblastoma patients and treated with Tumor Treating Fields (TTFields)
Authors: Munoz Yamhilette Licon , Sidebottom Rachel B. , Varela Samantha , Bowers Christian A. , Piccirillo Sara G.M. 
Published: March 2024

Abstract
Treatment of glioblastoma (GBM) is challenging due to its heterogeneous nature, invasive potential, and poor response to standard of care treatments. As a result, GBM inevitably recurs and only approximately 7% of patients survive 5 years post-diagnosis. Areas of residual disease represent the source of the recurrent tumor that is fatal for GBM patients. However, targeting the residual disease is not offered as part of the standard of care because these areas are difficult to identify and, to date, they have not been characterized during disease progression. Our laboratory was the first to identify and characterize residual disease in the sub-ventricular zone (SVZ) of the lateral ventricles of GBM patients. Specifically, our work revealed that in 65% of the cases the SVZ contains treatment-resistant cancer stem-like cells (CSCs) that seed the recurrent tumor, thus investigating residual disease in this area may hold the key to developing a valid therapeutic target for many patients. In this study, we are examining the impact of Tumor Treating Fields (TTFields) on treatment-resistant CSCs isolated from the SVZ of GBM patients using molecular techniques, such as single-cell transcriptomics and functional phenotyping analysis. To date, we have isolated and characterized 12 CSCs. These cells are maintained in conditions that preserve the molecular profile of the original patient tumor, thus representing bona fide models to study the impact of TTFields on GBM residual disease. We observed that: (i) CSCs isolated from the SVZ of individual GBM patients show different sensitivity to TTFields, (ii) the anti-proliferative effects of TTFields are maintained at different plating cell densities and among different patients, (iii) as the frequency of TTFields increases from 50 kHz to 200 kHz, CSCs from some patients undergo morphological changes, such as fewer spheres, more round-shaped cells, and fewer connections between cells. Apoptosis is also observed at 150 and 200 kHz. To determine the impact of TTFields on treatment-resistant cancer stem-like cells, we used 100 µM Temozolomide and ionizing radiation (10 Gy) mimicking the standard of care of GBM patients, and (iv) the growth of the treatment-resistant cancer stem-like cells is inhibited by TTFields when this treatment is used at 200 kHz. Ongoing work focuses on single-cell transcriptomics and functional assays of CSCs to elucidate the mechanisms whereby TTFields impact the proliferation of CSCs in the SVZ of GBM patients. In the long run, the results of this work will allow the identification of SVZ-specific targets for the development of novel and more effective treatments for GBM patients.
Citation Format: Yamhilette Licon Munoz, Rachel B. Sidebottom, Samantha Varela, Christian A. Bowers, Sara G.M. Piccirillo. Cellular and molecular characterization of cancer stem-like cells isolated from the sub-ventricular zone of glioblastoma patients and treated with Tumor Treating Fields (TTFields) [abstract]. In: Proceedings of the AACR Special Conference on Brain Cancer; 2023 Oct 19-22; Minneapolis, Minnesota. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_1):Abstract nr A024.