Chemo-Cryo Combination Therapy: An Adjunctive Model for the Treatment of Prostate Cancer

Abstract

Despite continuing research and the development of alternate therapeutic options, prostate cancer remains problematic. Chemotherapy has played a minor role as a treatment option due to its lack of efficacy. Whereas cryotherapy has received renewed attention as a treatment modality, it too fails to offer an absolute curative option. Previously, we reported on the utilization of a therapeutic model, which, in combination, increases cell death in a canine renal cell model. Based upon that study, we investigated a combination therapy model as an alternative for the treatment modality for prostate cancer. We hypothesized that the combination of chemotherapy and cryosurgery would result in enhanced cell death, thereby presenting a more effective treatment of prostate cancer. A human prostate cancer cell (PC-3) model was exposed to 5-fluorouracil (5-FU) for 2 and 4 days (prefreeze), freezing (−5 to −100°C), or a combination of the two treatments, and each was assessed for effectiveness over a 2-week posttreatment period. Additionally, investigation into the mechanisms of cell death initiated by the respective therapies was performed through DNA cleavage analysis. For chemotherapy, cultures exposed to 5-FU (2–4 days) yielded a 15–25% loss in cell survival. For cryotherapy, cultures exposed to a temperature window of −5 to −20°C yielded an initial 5–70% loss of viability but cells propagated over time. Cultures exposed to temperatures of −25 to −80°C yielded a 90–99% (±4.5%) initial loss in viability with repopulation observed by 12 days postthaw. Cells frozen to −100°C yielded 100% (±0.3%) loss of viability and exhibited no signs of propagation. For chemo-cryo therapy, combination treatment at milder temperatures (−5 to −25°C) resulted in an enhanced loss of cell viability compared to that for either treatment alone. Combination treatment at lower temperatures (−40 to −80°C) resulted in a complete loss of cell viability. DNA fragmentation analysis at 48 h posttreatment revealed that dead (detached) cells treated with 5-FU died primarily through apoptosis, whereas dead cells from freezing (−15°C) alone died primarily through freeze-rupture and necrosis. Detached cell analysis from combination treatment at −15°C revealed the presence of apoptotic, necrotic, and freeze-rupture cell death. Scanning electron micrographs of cells exposed to freezing contributing to cell death. These data demonstrate that the combination of 5-FU at sublethal doses and freezing temperatures improves human prostate cancer cell death efficacy. Further, we suggest that chemo-cryo therapy offers a potential alternative treatment for the control and eradication of prostate cancer.