The lung is the most frequent site of distant melanoma metastases. Metastases of melanoma in the lungs oﬀer a very poor prognosis, with a 5-year survival rate of below 10%. Hyperthermic therapies including modulated electro-hyperthermia (mEHT) in clinical settings have been used to improve the eﬃcacy of radiotherapy, chemotherapy, and immunotherapy of tumors. In this study, we focused primarily on the optimization of mEHT for targeted lung treatment of mice lungsburdenedwithB16F10melanomapulmonarymetastases,withaparticularfocusonelucidating the mechanism of action of mEHT on treated melanoma cells while investigating any potential treatment-relatedsideeﬀectsonnormallungtissue. mEHTshowedevidenceofsigniﬁcantanti-tumor eﬀects as demonstrated by the reduced number of pulmonary metastatic nodules, DNA damage response, downregulation of Ki67 expression, higher immune cell inﬁltration, and upregulation of p21waf1 expression in mEHT-treated tumors.
Modulated electro-hyperthermia (mEHT) is a novel complementary therapy in oncology which is based on the higher conductivity and permittivity of cancerous tissues due to their enhanced glycolytic activity and ionic content compared to healthy normal tissues. We aimed to evaluate the potential of mEHT, inducing local hyperthermia, in the treatment of pulmonary metastatic melanoma. Our primary objective was the optimization of mEHT for targeted lung treatment as well as to identify the mechanism of its potential anti-tumor eﬀect in the B16F10 mouse melanoma pulmonarymetastasesmodelwhileinvestigatingthepotentialtreatment-relatedsideeﬀectsofmEHT on normal lung tissue. Repeated treatment of tumor-bearing lungs with mEHT induced signiﬁcant anti-tumor eﬀects as demonstrated by the lower number of tumor nodules and the downregulation of Ki67 expression in treated tumor cells. mEHT treatment provoked signiﬁcant DNA double-strand breaks indicated by the increased expression of phosphorylated H2AX protein in treated tumors, although treatment-induced elevation of cleaved/activated caspase-3 expression was insigniﬁcant, suggesting the minimal role of apoptosis in this process. The mEHT-related signiﬁcant increase in p21waf1 positive tumor cells suggested that p21waf1-mediated cell cycle arrest plays an important role in the anti-tumor eﬀect of mEHT on melanoma metastases. Signiﬁcantly increased CD3+, CD8+ T-lymphocytes, and F4/80+CD11b+ macrophage density in the whole lung and tumor of treated animals emphasizes the mobilizing capability of mEHT on immune cells. In conclusion, mEHT can reduce the growth potential of melanoma, thus oﬀering itself as a complementary therapeutic option to chemo- and/or radiotherapy.