Abstract 3309: Tumor-treating fields decrease proliferation and clonogenicity of patient-derived WHO grade IV glioma cell lines

Abstract

Abstract Despite decades of research, efficacious treatments for malignant glioma tumors are limited. Tumor-treating fields (TTFields) are FDA-approved for the treatment of newly-diagnosed and recurrent glioblastoma. In this study, in vitro experiments comparing TTFields to untreated controls were performed on patient-derived grade IV glioma cell lines to determine the effects of TTFields on cell proliferation and clonogenicity. Methods: Studies utilizing patient tumor specimens were approved by the Wayne State University Institutional Review Board and written informed consent was obtained from participants. Patient tumor specimens (glioblastoma and gliosarcoma) were collected immediately following microsurgical resection. Single-cell suspensions from the tumor tissues were prepared by enzymatic and mechanical disruption. Equal numbers of cells were plated on plastic coverslips in DMEM/F12 media supplemented with 10% fetal bovine serum. TTFields were applied at 200 kHz to half of the coverslips. Culture media was replaced every day. At the conclusion of the 2 week treatment, cell proliferation was assessed with the XTT assay and cells were harvested and replated for clonogenic assays (10,000 cells/well). The resulting colonies were fixed and stained with crystal violet and counted with an automated colony counter. Control vs. TTFields treated groups were compared by two-tailed t-tests. Results: The two-week TTFields treatment significantly reduced cell proliferation in both the glioblastoma (41.6 ± 11.1 % control; n=4; p<0.001) and in the gliosarcoma (41.6 ± 16.6 % control; n=4; p<0.002) as measured by XTT assay. The clonogenic assay revealed that the number of colonies generated from both cell lines was reduced by TTFields treatment. For the glioblastoma cell line, control cells yielded 847 colonies with an average diameter of 462.8 ± 5.6 µM while TTFields-treated cells yielded 561 colonies with an average diameter of 435.1 ± 7.3 µM, which was a statistically significant decrease (p=0.0022). For the gliosarcoma cell line, control cells yielded 809 colonies vs. 144 colonies from the TTFields treated cells, although the average diameter of the colonies was unchanged between groups (control 375.1 ± 176.1 µM; TTFields 362.9 ± 196.0 µM). Conclusions: In vitro application of TTFields markedly reduced cell proliferation and clonogenicity in both patient-derived WHO grade IV glioblastoma and gliosarcoma cell lines. This is the first report on the in vitro effects of TTFields on gliosarcoma. Citation Format: Sharon K. Michelhaugh, Sam Kiousis, Adrianne Wallace-Povirk, Sandeep Mittal. Tumor-treating fields decrease proliferation and clonogenicity of patient-derived WHO grade IV glioma cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3309. doi:10.1158/1538-7445.AM2017-3309