101 Vitamin D3 cryosensitization in androgen insensitive prostate cancer

Abstract

Cryoablation is increasingly utilized as both a primary and salvage treatment option for prostate cancer (PC). The dynamic nature of a cryolesion provides a temperature gradient which correlates with complete cell death at the core of the iceball to a heterogeneous zone of live cells at the elevated temperatures near the periphery. The utilization of molecular adjuvants aims to achieve an increased ablative zone at these warmer isotherms. Previous studies have confirmed the synergistic effects of chemotherapeutic drugs in combination with freezing temperatures associated with the periphery of a cryogenic lesion (−10 °C through −25 °C). More recently we have utilized the active metabolite of vitamin D3 (calcitriol) as a cryosensitizing agent in numerous in vitro models. In both murine and human studies we found that calcitriol pre-treatment yielded a significant increase in cell death over freezing alone. Additionally, both androgen sensitive (AS) and androgen insensitive (AI) human PC models respond to calcitriol cryosensitization. Given the difficulty in treating AIPC clinically, we further investigated the sensitization capabilities of calcitriol in this model. Specifically, in the AIPC line PC-3, 24 h calcitriol pre-treatment yielded a 36% increase in cell death at the −15 °C isotherm compared to temperature-matched controls (60% viable vs. 96%, respectively). In addition to 2D in vitro modeling, studies were also conducted using a novel 3D prostate tissue engineered model (pTEM) system. PC-3 cells grown in this 3D matrix were frozen using a novel supercritical nitrogen (SCN) device in the presence or absence of calcitriol as a cryosensitizer and the effectiveness of calcitriol pre-treatment was evaluated. Results indicate that the zone of cellular ablation was increased by 20% with the addition of calcitriol as compared to non-treated frozen samples, illustrating an increase in cell death while simultaneously reducing the need for an enlarged positive freeze margin. These studies demonstrate the in vitro effectiveness of a combinatorial approach to AIPC treatment utilizing calcitriol and cryotherapy and thus illustrate the potential for future clinical applications. Source of funding: CPSI Biotech. Conflict of interest: None declared. ksantucci@cpsibiotech.com