Cryoinjury Enhancement of Breast Cancer Cells by Use of a Molecular Adjuvant (TNF-alpha)

Cryoinjury of human breast cancer cells (MCF7) in engineered tissue equivalents and the enhancement of the cryoinjury by use of a molecular adjuvant (tumor necrosis factor alpha, TNF-α) was studied. Tissue equivalents (TEs) were constructed by seeding MCF7 cells in collagen solutions at the concentration of 100,000 cells/ml. After cultured in vitro for 2 days, the TEs were exposed with 100ng/ml TNF-α and cultured for 24 hours, and then underwent a single freeze-thaw cycle by a cryosurgery simulator. With the concentration and duration of TNF-α treatment studied, no apoptotic or necrotic cell death was observed by the administration of TNF-α only. After a freeze/thaw, MCF7 cells within the frozen region of the TEs were significantly injured immediately (i.e. ≤ 20% survival), but gradually repopulated and reached approximately 80% survival in Day3 without TNF-α pre-treatment. MCF7 with TNF-α pre-treatment showed the slight enhancement of immediate injury in the frozen region (i.e. ≤ 10% survival), and the repopulation was significantly inhibited so the viability remained below 40% even in Day 3. These results imply that TNF-α can be a potent adjuvant for cryosurgery.