In Vitro Investigation of Renal Cell Carcinoma Response to Combination Sorafenib and Cryoablation Treatment

Abstract

The 5-year survival rate for localized kidney cancer is 93%, but only 13% for those presenting with metastatic disease (2019 SEER data). Cryosurgery is an established treatment modality for renal cell cancer (RCC), with outcomes showing equipoise to radiofrequency ablation (RFA) and partial nephrectomy. Sorafenib is a targeted therapy for RCC utilized in more advanced stage diseases. Given the success of both cryoablation and sorafenib as monotherapies for RCC, in this study, we investigated the cellular response of RCC to combinatorial sorafenib pre-treatment and cryoablation in vitro using cell culture and tissue-engineered tumor models. In vitro samples were exposed to a single or repeat (double) 5-minute freeze at -10°C, -15°C, or -20°C representing temperatures within the periphery of a cryolesion. A repeat freeze to -20°C was necessary to fully ablate samples yielding day 1 viability of 2.9% (±0.2) with no recovery observed over the 7 days post-treatment culture. These findings were consistent with published data on the lethal temperature in RCC, suggesting that -25°C is necessary to destroy RCC following a single freeze event. Pre-treatment of samples with sorafenib at concentrations of 10.61 and 21.21 µM (½ clinical and clinical dose, respectively) was combined with a single or repeat 5-minute freeze to -10°C, -15°C, or -20°C. At the time of drug removal (day 0/pre-freeze), 10.61 µM sorafenib treated samples yielded 25.3% (±0.4) viability, yet samples regrew to control levels by day 7. Following combination freeze and sorafenib exposure, sample viability was found to be 27.5% (±0.7), 2.9% (±0.4), and 0.2% (±0.02) following a single freeze and 15.6% (±0.5), 0.7% (±0.1), and 0.1% (±0.01) following a repeat (double freeze), respectively. Regrowth was observed over the 7-day assessment period in samples exposed to a -10°C single or double freeze and a -15°C single freeze, but not in the -20°C single freeze or -15°C double freeze conditions. Thus, pre-treatment with 10.61 µM sorafenib was found to increase the minimum lethal temperature from the reported -25°C to -20°C following a single freeze event and from -20°C to -15°C following a double freeze. Results of the cell culture studies were confirmed in the 3D tissue-engineered tumor model, wherein the combination of 10.61 µM sorafenib and freezing was found to further increase the lethal temperature from <-20°C to -15°C following a single freeze event. This increased freeze susceptibility yielded a 32% improvement in the overall ablative volume of the ice ball following combinatorial treatment versus freezing alone. These in vitro results suggest that the combination of sorafenib and cryoablation may provide a possible combinatorial treatment path for RCC.