Pre-conditioning cryosurgery: cellular and molecular mechanisms and dynamics of TNF-α enhanced cryotherapy in an in vivo prostate cancer model system.

Cryosurgery is increasingly being used to treat prostate cancer; however, a major limitation is local recurrence of disease within the previously frozen tissue. We have recently demonstrated that tumor necrosis factor alpha (TNF-α), given 4h prior to cryosurgery can yield complete destruction of prostate cancer within a cryosurgical iceball. The present work continues the investigation of the cellular and molecular mechanisms and dynamics of TNF-α enhancement on cryosurgery. In vivo prostate tumor (LNCaP Pro 5) was grown in a dorsal skin fold chamber (DSFC) on a male nude mouse. Intravital imaging, thermography, and post-sacrifice histology and immunohistochemistry were used to assess iceball location and the ensuing biological effects after cryosurgery with and without TNF-α pre-treatment. Destruction was specifically measured by vascular stasis and by the size of histologic zones of injury (i.e., inflammatory infiltrate and necrosis). TNF-α induced vascular pre-conditioning events that peaked at 4h and diminished over several days. Early events (4-24 h) include upregulation of inflammatory markers (nuclear factor-κB (NFκB) and vascular cell adhesion molecule-1 (VCAM)) and caspase activity in the tumor prior to cryosurgery. TNF-α pre-conditioning resulted in recruitment of an augmented inflammatory infiltrate at day 3 post treatment vs. cryosurgery alone. Finally, pre-conditioning yielded enhanced cryosurgical destruction up to the iceball edge at days 1 and 3 vs. cryosurgery alone. Thus, TNF-α pre-conditioning enhances cryosurgical lesions by vascular mechanisms that lead to tumor cell injury via promotion of inflammation and leukocyte (esp. neutrophil) recruitment.