Abstract 2270: Non-invasive radiofrequency increases the anticancer effect of gemcitabine in treating pancreatic cancer via autophagy

Abstract

Abstract Pancreatic cancer has a high mortality rate. Currently the main treatment for unresectable pancreatic adenocarcinoma is chemotherapy based on gemcitabine (GCB) use. Trials of GCB, combined with radiation therapy and other cytotoxic agents, did not produce a substantial improvement in patient response over GCB alone. This indicates that new therapeutic approaches should be developed for the treatment of this disease. In our laboratory we developed a new method based on the use of non-invasive radiofrequency (RF) field. Electromagnetic energy produced by 220 MHz was shown to have low tissue specific absorption rate and therefore, excellent whole body tissue penetration with documented safety in humans exposed to the RF field for several hours. The RF frequency of our device is lower, 13.56 MHz and generates mild hyperthermia. In the current study we used human Panc-1 tumor cells, known for their poor response to GCB, and studied the effect of RF on tumor cells with and without GCB. Combination of GCB with RF (GCB+RF) significantly inhibited proliferation of Panc-1 cells in vitro when compared with either treatment alone (P<0.005). Using orthotopic Panc-1 tumor mouse model, we were able to achieve significant (P<0.01) tumor growth arrest in mice that received GCB+RF treatment. Mice receiving RF or GCB alone showed no significant response. In these experiments mice received treatment with GCB at 70 mg/kg i.p. 24 hr prior to the 10-minute RF exposure once weekly for up to 8 weeks without evidence of toxicity. Immunohistochemical analysis of tumors for proliferation, apoptosis, and angiogenesis showed that proliferation index was the lowest only in the group receiving GCB+RF treatment when compared with untreated group or groups receiving any single treatment. Significant elevation of apoptosis and reduction of angiogenesis were observed in all treated groups when compared with untreated control, however, no significant difference was determined between treated groups, indicating that observed antiproliferative effect of combination treatment in vivo could be induced by another type of tumor cell death, for example, by autophagy or necroptosis. In fact, electron microscopy of Panc-1 cells treated with GCB+RF showed substantial elevation of autophagosomes in tumor cells when compared with either of the single treatments. Staining for autophagy with anti-LC3B antibody revealed the induction of autophagy in tumor cells 24 hr after RF exposure which was reversed within 24 hr after exposure. GCB treatment prevented tumor cells recovery from autophagocytosis after RF exposure and correlated with substantial elevation of tumor cells death. The obtained results demonstrate the ability of non-invasive RF treatment to stimulate autophagy in pancreatic tumor cells, which may play an important role improving anticancer effect of GCB. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2270. doi:1538-7445.AM2012-2270