Correction to "Digoxin-Mediated Inhibition of Potential Hypoxia-Related Angiogenic Repair in Modulated Electro-Hyperthermia (mEHT)-Treated Murine Triple-Negative Breast Cancer Model".

[This corrects the article DOI: 10.1021/acsptsci.3c00296.].

Modulated Electro-Hyperthermia Accelerates Tumor Delivery and Improves Anticancer Activity of Doxorubicin Encapsulated in Lyso-Thermosensitive Liposomes in 4T1-Tumor-Bearing Mice.

Modulated electro-hyperthermia (mEHT) is an adjuvant cancer therapy that enables tumor-selective heating (+2.5 °C). In this study, we investigated whether mEHT accelerates the tumor-specific delivery of doxorubicin (DOX) from lyso-thermosensitive liposomal doxorubicin (LTLD) and improves its anticancer efficacy in mice bearing a triple-negative breast cancer cell line (4T1). The 4T1 cells were orthotopically injected into Balb/C mice, and mEHT was performed on days 9, 12, and 15 after the implantation. DOX, LTLD, or PEGylated liposomal DOX (PLD) were administered for comparison. The tumor size and DOX accumulation in the tumor were measured. The cleaved caspase-3 (cC3) and cell proliferation were evaluated by cC3 or Ki67 immunohistochemistry and Western blot. The LTLD+mEHT combination was more effective at inhibiting tumor growth than the free DOX and PLD, demonstrated by reductions in both the tumor volume and tumor weight. LTLD+mEHT resulted in the highest DOX accumulation in the tumor one hour after treatment. Tumor cell damage was associated with cC3 in the damaged area, and with a reduction in Ki67 in the living area. These changes were significantly the strongest in the LTLD+mEHT-treated tumors. The body weight loss was similar in all mice treated with any DOX formulation, suggesting no difference in toxicity. In conclusion, LTLD combined with mEHT represents a novel approach for DOX delivery into cancer tissue.

Digoxin-Mediated Inhibition of Potential Hypoxia-Related Angiogenic Repair in Modulated Electro-Hyperthermia (mEHT)-Treated Murine Triple-Negative Breast Cancer Model.

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer type with no targeted therapy and hence limited treatment options. Modulated electrohyperthermia (mEHT) is a novel complementary therapy where a 13.56 MHz radiofrequency current targets cancer cells selectively, inducing tumor damage by thermal and electromagnetic effects. We observed severe vascular damage in mEHT-treated tumors and investigated the potential synergism between mEHT and inhibition of tumor vasculature recovery in our TNBC mouse model. 4T1/4T07 isografts were orthotopically inoculated and treated three to five times with mEHT. mEHT induced vascular damage 4-12 h after treatment, leading to tissue hypoxia detected at 24 h. Hypoxia in treated tumors induced an angiogenic recovery 24 h after the last treatment. Administration of the cardiac glycoside digoxin with the potential hypoxia-inducible factor 1-α (HIF1-α) and angiogenesis inhibitory effects could synergistically augment mEHT-mediated tumor damage and reduce tissue hypoxia signaling and consequent vascular recovery in mEHT-treated TNBC tumors. Conclusively, repeated mEHT induced vascular damage and hypoxic stress in TNBC that promoted vascular recovery. Inhibiting this hypoxic stress signaling enhanced the effectiveness of mEHT and may potentially enhance other forms of cancer treatment.

Enhancing therapeutic efficacy in triple-negative breast cancer and melanoma: synergistic effects of modulated electro-hyperthermia (mEHT) with NSAIDs especially COX-2 inhibition in in vivo models.

Triple-negative breast cancer (TNBC) is a leading cause of cancer mortality and lacks modern therapy options. Modulated electro-hyperthermia (mEHT) is an adjuvant therapy with demonstrated clinical efficacy for the treatment of various cancer types. In this study, we report that mEHT monotherapy stimulated interleukin-1 beta (IL-1ß) and interleukin-6 (IL-6) expression, and consequently cyclooxygenase 2 (COX-2), which may favor a cancer-promoting tumor microenvironment. Thus, we combined mEHT with nonsteroid anti-inflammatory drugs (NSAIDs): a nonselective aspirin, or the selective COX-2 inhibitor SC236, in vivo. We demonstrate that NSAIDs synergistically increased the effect of mEHT in the 4T1 TNBC model. Moreover, the strongest tumor destruction ratio was observed in the combination SC236 + mEHT groups. Tumor damage was accompanied by a significant increase in cleaved caspase-3, suggesting that apoptosis played an important role. IL-1ß and COX-2 expression were significantly reduced by the combination therapies. In addition, a custom-made nanostring panel demonstrated significant upregulation of genes participating in the formation of the extracellular matrix. Similarly, in the B16F10 melanoma model, mEHT and aspirin synergistically reduced the number of melanoma nodules in the lungs. In conclusion, mEHT combined with a selective COX-2 inhibitor may offer a new therapeutic option in TNBC.

Modulated Electro-Hyperthermia Induces a Prominent Local Stress Response and Growth Inhibition in Mouse Breast Cancer Isografts.

Modulated electro-hyperthermia (mEHT) is a selective cancer treatment used in human oncology complementing other therapies. During mEHT, a focused electromagnetic field (EMF) is generated within the tumor inducing cell death by thermal and nonthermal effects. Here we investigated molecular changes elicited by mEHT using multiplex methods in an aggressive, therapy-resistant triple negative breast cancer (TNBC) model. 4T1/4T07 isografts inoculated orthotopically into female BALB/c mice were treated with mEHT three to five times. mEHT induced the upregulation of the stress-related Hsp70 and cleaved caspase-3 proteins, resulting in effective inhibition of tumor growth and proliferation. Several acute stress response proteins, including protease inhibitors, coagulation and heat shock factors, and complement family members, were among the most upregulated treatment-related genes/proteins as revealed by next-generation sequencing (NGS), Nanostring and mass spectrometry (MS). pathway analysis demonstrated that several of these proteins belong to the response to stimulus pathway. Cell culture treatments confirmed that the source of these proteins was the tumor cells. The heat-shock factor inhibitor KRIBB11 reduced mEHT-induced complement factor 4 (C4) mRNA increase. In conclusion, mEHT monotherapy induced tumor growth inhibition and a complex stress response. Inhibition of this stress response is likely to enhance the effectiveness of mEHT and other cancer treatments.

Exhaustion of Protective Heat Shock Response Induces Significant Tumor Damage by Apoptosis after Modulated Electro-Hyperthermia Treatment of Triple Negative Breast Cancer Isografts in Mice.

Modulated electro-hyperthermia (mEHT) is a complementary antitumor therapy applying capacitive radiofrequency at 13.56 MHz. Here we tested the efficiency of mEHT treatment in a BALB/c mouse isograft model using the firefly luciferase-transfected triple-negative breast cancer cell line, 4T1. Tumors inoculated orthotopically were treated twice using a novel ergonomic pole electrode and an improved mEHT device (LabEHY 200) at 0.7 ± 0.3 W for 30 min. Tumors were treated one, two, or three times every 48 h. Tumor growth was followed by IVIS, caliper, and ultrasound. Tumor destruction histology and molecular changes using immunohistochemistry and RT-qPCR were also revealed. In vivo, mEHT treatment transitionally elevated Hsp70 expression in surviving cells indicating heat shock-related cell stress, while IVIS fluorescence showed a significant reduction of viable tumor cell numbers. Treated tumor centers displayed significant microscopic tumor damage with prominent signs of apoptosis, and major upregulation of cleaved/activated caspase-3-positive tumor cells. Serial sampling demonstrated substantial elevation of heat shock (Hsp70) response twelve hours after the treatment which was exhausted by twenty-four hours after treatment. Heat shock inhibitors Quercetin or KRIBB11 could synergistically amplify mEHT-induced tumor apoptosis in vitro. In conclusion, modulated electro-hyperthermia exerted a protective heat shock response as a clear sign of tumor cell stress. Exhaustion of the HSR manifested in caspase-dependent apoptotic tumor cell death and tissue damage of triple-negative breast cancer after mEHT monotherapy. Inhibiting the HSR synergistically increased the effect of mEHT. This finding has great translational potential.