Heat shock factor 1 inhibition enhances the effects of modulated electro hyperthermia in a triple negative breast cancer mouse model

Abstract

Female breast cancer is the most diagnosed cancer worldwide. Triple negative breast cancer (TNBC) is the most aggressive type and there is no existing endocrine or targeted therapy. Modulated electro-hyperthermia (mEHT) is a non-invasive complementary cancer therapy using an electromagnetic field generated by amplitude modulated 13.56 MHz frequency that induces tumor cell destruction. However, we have demonstrated a strong induction of the heat shock response (HSR) by mEHT, which can result in thermotolerance. We hypothesized that inhibition of the heat shock factor 1 (HSF1) can synergize with mEHT and enhance tumor cell-killing. Thus, we either knocked down the HSF1 gene with a CRISPR/Cas9 lentiviral construct or inhibited HSF1 with a specific small molecule inhibitor: KRIBB11 in vivo. Wild type or HSF1-knockdown 4T1 TNBC cells were inoculated into the mammary gland’s fat pad of BALB/c mice. Four mEHT treatments were performed every second day and the tumor growth was followed by ultrasound and caliper. KRIBB11 was administrated intraperitoneally at 50 mg/kg daily for 8 days. HSF1 and Hsp70 expression were assessed. HSF1 knockdown sensitized transduced cancer cells to mEHT and reduced tumor growth. HSF1 mRNA expression was significantly reduced in the KO group when compared to the empty vector group, and consequently mEHT-induced Hsp70 mRNA upregulation diminished in the KO group. Immunohistochemistry (IHC) confirmed the inhibition of Hsp70 upregulation in mEHT HSF1-KO group. Demonstrating the translational potential of HSF1 inhibition, combined therapy of mEHT with KRIBB11 significantly reduced tumor mass compared to either monotherapy. Inhibition of Hsp70 upregulation by mEHT was also supported by qPCR and IHC. In conclusion, we suggest that mEHT-therapy combined with HSF1 inhibition can be a possible new strategy of TNBC treatment with great translational potential.

Ivermectin Synergizes with Modulated Electro-hyperthermia and Improves Its Anticancer Effects in a Triple-Negative Breast Cancer Mouse Model

“…In our previous studies, we demonstrated that mEHT-induced a heat shock response (HSR) with the upregulation of HSF1 and HSP70. The concomitant inhibition of this HSR improved the anticancer effects of mEHT. , However, the drugs applied in those studies have limitations, such as the enhancement of HSPB1 phosphorylation (e.g., quercetin) and the lack of clinical application (e.g., KRIBB11) . Thus, to improve the clinical translational potency of this strategy, inhibition of mEHT-induced HSPs by FDA-approved drugs is needed.…”

“…Modulated electro-hyperthermia (mEHT) is a noninvasive adjuvant cancer treatment approved for clinical use in different cancer types. − mEHT uses an amplitude-modulated, 13.56 MHz radiofrequency electromagnetic field by capacitive coupling between two electrodes surrounding the cancer. , Due to the difference in bioelectrical properties between cancerous and healthy tissues, , the electromagnetic field energy is absorbed mainly by cancer tissues, resulting in cancer-specific tissue damage. , At the cellular level, mEHT generates heat, leading to cellular stress and upregulation of HSPs . We previously demonstrated enhanced anticancer effects of mEHT by inhibiting HSP70 in vitro and heat shock factor 1 (HSF1) in vivo, utilizing the small molecule inhibitors of the heat shock response central regulator (i.e., HSF1): quercetin and KRIBB11, and by knocking down HSF1 production of the tumor cells with a CRISPR/Cas9 construct . However, quercetin and its derivatives enhance HSPB1 phosphorylation that supports cancer cell survival .…”