Gertrud Forika1, Andrea Balogh2, Tamás Vancsik1, Zoltán Benyó2, Tibor Krenács1
1Semmelweis University, 1st Department of Pathology and Experimental Cancer Research, Budapest, Hungary
2Semmelweis University, Institute of Clinical Experimental Research, Budapest, Hungary
Introduction: Modulated electro-hyperthermia (mEHT) is a non-invasive therapy form using impedance-coupled radiofrequency and generate 42°C heat in malignant tissues. mEHT has been used as a complementary to chemo-and radiotherapy.
Gemcitabine, a thymidylate synthase inhibitor of DNA replication, is commonly used for treating metastatic pancreas adenocarcinoma.
Aims: Using a radioresistant adenocarcinoma cell line Panc1, we tested the efficiency of mEHT, gemcitabine and radiotherapy alone compared to their combinations.
Method: Treatment groups of adherent Panc1 cultures were as follows: untreated control (C); mEHT treated for 60 min (mEHT); irradiated with 2 Gy using 137Cs (R), gemcitabine-treated with 10µM/ml (G); irradiated followed by mEHT (mEHT+R) or gemcitabine during mEHT (mEHT+G). 24 hours after treatments cell morphology, the proportion of apoptotic and necrotic (AnnexinV/propidium iodide positive) cells, tumor cell viability, ALDH1+ tumor stem cell fractions (CSC), tumor colony formation, DNA-double-strand brakes (H2Axγ clusters), the cell stress marker calreticulin, were tested using flow cytometry and immunocytochemistry.
Results: 24 hours post-mEHT treatment a significant tumor destruction was observed featured by elevated number of tumor cells with nuclear shrinkage, chromatin condensation and apoptotic bodies. The apoptotic ratio was the highest in groups receiving combined treatments followed by mEHT and gemcitabine-treated groups. The ALDH1+ tumor progenitor/stem cell number also reduced significantly in mEHT, gemcitabine, mEHT+G and mEHT+R treated groups but not in the irradiated group. These were in agreement with the CSCs fraction resulted from the colony formation test. Furthermore, H2Axγ and calreticulin positive cell fractions, indicating DNA double strand-brakes and ER-stress, respectively, were also significantly increased in the mEHT, G, mEHT+G and mEHT+R treated groups.
Conclusion: mEHT treatment alone can induce cell stress and DNA double-strand breaks Panc1 tumor cells leading to massive apoptosis. Single mEHT treatment was as effective as gemcitabine treatment. Irradiation alone had not major effect on Panc1 cells including CSCs.
This study was funded by NKFIH-NVKP_16-1-2016-0042
Doctoral School: PATHOLOGICAL SCIENCES
Program: Experimental Oncology
Supervisor: Tibor Krenács
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