Chemical adjuvant cryosurgery with antifreeze proteins.

Background And Objectives: Imaging monitored cryosurgery is emerging as an important minimally invasive surgical technique for treatment of cancer. Although imaging allows excellent control over the process of freezing itself, recent studies show that at high subzero temperatures cells survive freezing. Antifreeze proteins (AFP) are chemical compounds that modify ice crystals to needle-like shapes that can destroy cells in cellular suspensions. The goal of this study was to determine whether these antifreeze proteins can also destroy cells in frozen tissue and serve as chemical adjuvants to cryosurgery.

Methods: Livers from six rats were excised, perfused with solutions of either phosphate-buffered saline (PBS) or PBS with 10 mg/ml AFP-I, and frozen with a special cryosurgery apparatus. Lobes were frozen with one or two freeze-thaw cycles and the cell viability was examined with a two stain fluorescent dye test and histological assessment.

Results: A significant percentage of hepatocytes survive freezing on the margin of a frozen cryolesion. AFP significantly increase cellular destruction in that region apparently through formation of intracellular ice.

Conclusions: This preliminary study demonstrates that antifreeze proteins may be effective chemical adjuvants to cryosurgery.