Abstract 2191: Reduced clonogenic potential of patient-derived lung adenocarcinoma brain metastasis cells after in vitro application of Tumor Treating Fields (TTFields)
Authors: Michelhaugh Sharon K. , Kiousis Sam , Mittal Sandeep 
Published: August 2019

Up to 40% of all non-small cell lung cancer (NSCLC) patients will develop brain metastases during their disease, with ~25% of patients presenting with brain metastases at the time of their initial lung cancer diagnosis. For the latter patient population, median survival is a dismal 8 months. Systemic therapies are typically ineffective at treating the brain metastases, even in cases when the extracranial disease responds to the therapy. Clinical trials utilizing TTFields therapy in patients with lung cancer brain metastases are underway. For these trials, TTFields are delivered at 150 kHz, as that is the frequency that has been determined for the treatment of primary lung cancer. In contrast, for the FDA-approved treatment of the most common malignant primary brain tumor, glioblastoma, TTFields are delivered at 200 kHz. In our previous study, we found that 150 kHz TTFields decreased proliferation of patient-derived lung adenocarcinoma brain metastasis cells to a greater degree than 200 kHz. In this study, patient-derived lung adenocarcinoma brain metastasis cells were assessed for clonogenic potential after in vitro TTFields application at either 150 or 200 kHz and compared to untreated control cells. Methods: Use of patient tumor tissue for this study was approved by the Institutional Review Board and written informed consent was obtained from the patient. A lung adenocarcinoma brain metastasis tumor was collected immediately following microsurgical resection. A single-cell suspension from the tumor tissue was prepared by enzymatic and mechanical disruption. After 3-6 passages in vitro, cells were plated on plastic coverslips (5x104each) in DMEM/F12 media supplemented with 10% fetal bovine serum. TTFields were applied at ~1.6 V/cm at 150 or 200 kHz (groups n=3-6) with one control group. Culture media was replaced every day. After 14 days of in vitro TTFields application, cells were assayed for lactase dehydrogenase (LDH) release into the media and cells were harvested and replated for the clonogenic assay. Control vs. TTFields-treated groups were compared with one-way ANOVA. Results: TTFields application reduced LDH in the media ~15% at 150 kHz and ~30% at 200 kHz (p=0.0011). In the clonogenic assay, cell counts were markedly reduced after TTFields in both the 150 kHz (142.4±120.1) and 200 kHz (457.2±431.9) compared to the controls (9136±2735; p=0.0007) although the post-hoc Tukey analysis found no statistical difference between the two TTFields-treated groups. Conclusions: Application of TTFields in vitro at 150 and 200 kHz reduced LDH release into the media as well as the clonogenic potential of the patient-derived lung adenocarcinoma brain metastasis cells.

Citation Format: Sharon K. Michelhaugh, Sam Kiousis, Sandeep Mittal. Reduced clonogenic potential of patient-derived lung adenocarcinoma brain metastasis cells after in vitro application of Tumor Treating Fields (TTFields) [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 2191.