Abstract 6649: Tumor treating fields (TTFields) induce an anti-tumor immune response in a pancreatic cancer mouse model
Authors: Kan Tal , Khalil Tharwat Haj , Barsheshet Yiftah , Voloshin Tali , Vorontsov Avital , Brant Boris , Koren Lilach , Blatt Roni , Cahal Shay , Zemer-Tov Efrat , Paz Rom , Klein-Goldberg Anat , Tempel Brami Catherine , Jacobovitch Sara , Volodin Alexandra , Koltun Bella , David Cfir , Haber Adi , Giladi Moshe , Weinberg Uri , Palti Yoram 
Published: March 2024

Abstract
Background: Pancreatic ductal adenocarcinoma (PDAC) is a deadly malignancy with few therapeutic options. Tumor Treating Fields (TTFields) are low-intensity electric fields that disrupt cellular processes critical for cancer cell division and tumor progression and are approved for the treatment of glioblastoma and pleural mesothelioma. A phase 3 clinical trial is in progress to test the efficacy and safety of TTFields concomitant with standard-of-care gemcitabine and nab-paclitaxel (GnP) as front-line treatment of locally advanced PDAC. TTFields have been shown to induce immunogenic cell death (ICD) in cancer cells and elicit a systemic anti-cancer immune response. Accordingly, the benefit of applying TTFields together with immune checkpoint inhibitors (ICI) was demonstrated in a phase 3 study in patients with non-small cell lung carcinoma. This preclinical study investigated TTFields-induced immune responses in PDAC.
Methods: An orthotopic PDAC tumor model was established by inoculating 4 × 105 Panc02 pancreatic cancer cells with stable luciferase expression into the pancreas tail of immune-competent C57BL/6 mice. The mice were randomized into four groups following bioluminescence detection of tumor volume: control, TTFields (150 kHz, 10 days), GnP (50 mg/kg for each drug, i.p. injected once a week for a total of two administrations), and GnP + TTFields. At the end of treatment, tumor volume was measured using caliper, and blood was collected for spectral flow cytometry-based immunophenotyping and ELISA testing for the ICD marker HMGB-1. In vitro, Panc02 cells were treated for 72h with TTFields (150 kHz, 1.62 V/cm RMS) and examined by flow cytometry for apoptosis and ATP secretion (using quinacrine staining) and surface exposure of calreticulin.
Results: TTFields markedly reduced the tumor size in Panc02 tumor-bearing mice compared to control mice. Analysis of peripheral blood effector (CD62L-CD44+) and central (CD62L+CD44+) memory T cells demonstrated the induction of circulating effector-memory cytotoxic CD8+ T cells. Additionally, serum HMGB-1 concentrations were significantly elevated in mice treated with TTFields compared to control mice, implying the involvement of ICD in the response to TTFields. In vitro, TTFields application induced apoptosis of Panc02 cells and increased ICD, as indicated by increased surface exposure of calreticulin and ATP depletion. When TTFields were used in Panc02 tumor bearing mice concomitantly with GnP, a substantial reduction in tumor size was detected, and a complete tumor regression was observed in a number of mice.
Conclusions: Our results suggest that TTFields may enhance the effects of standard-of-care chemotherapy for the treatment of PDAC. Furthermore, TTFields were shown to induce ICD and activate an antitumor immune response in PDAC, supporting future studies evaluating the efficacy of TTFields together with ICI in PDAC.
Citation Format: Tal Kan, Tharwat Haj Khalil, Yiftah Barsheshet, Tali Voloshin, Avital Vorontsov, Boris Brant, Lilach Koren, Roni Blatt, Shay Cahal, Efrat Zemer-Tov, Rom Paz, Anat Klein-Goldberg, Catherine Tempel Brami, Sara Jacobovitch, Alexandra Volodin, Bella Koltun, Cfir David, Adi Haber, Moshe Giladi, Uri Weinberg, Yoram Palti. Tumor treating fields (TTFields) induce an anti-tumor immune response in a pancreatic cancer mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6649.