Ethanol ablation reliably achieves an anti-metastatic response after modulating tumor acidity and regulatory T cells

Objectives: Ethylcellulose (ECE) injections are a low-cost, accessible ablation method for patients with localized tumors. In order to increase the immunogenicity of the tumor microenvironment in triple-negative breast cancers, cyclophosphamide (cyclo) and sodium bicarbonate (bicarb) were used to prime the immune system prior to ECE injections in pre-clinical models of cancer. Cyclo specifically depletes pro-tumor regulatory T cells when once at a low-dose of 200 mg/kg (human equivalent dose of 16 mg/kg). Daily oral bicarb has been shown to reduce tumor pH and enhance infiltration of cytotoxic T cells into the tumor. Methods: Immunocompetent BALB/c mice were injected with orthotopic triple-negative (P53-null) breast cancer cell lines (4T1, 67NR). Tumor-bearing mice were treated with combinations of ECE, cyclo, and bicarb. On day 7 after tumor inoculation bicarb at 200 mM was added to the drinking water, on day 9 cyclo at 200 mg/kg IP was given, and on day 10 ECE ablation was performed with an intratumoral injection of 150 mL. Tumor growth rates, overall survival, and metastatic burden after treatment were quantified (n=5-7). To quantify metastatic disease, lungs were harvested at day 60 or earlier if the humane tumor burden limit of 2 cms was exceeded. HE however, the addition of ECE to cyclo+bicarb significantly decreased the metastatic burden at death (Fig. 1C, P Download : Download high-res image (101KB) Download : Download full-size image Conclusions: The addition of cyclo+bicarb to ECE produced a potent systemic anti-tumor response reducing the size of the primary tumors and metastases in vivo.