title: Addition of anticancer agents enhances freezing-induced prostate cancer cell death: implications of mitochondrial involvement.
abstract: Recent evidence suggests that the successful treatment of prostate cancer may require adjuvant therapies. Accordingly, a better understanding of the molecular mechanisms involved in current treatments may lead to enhanced efficacy by providing a basis for adjuvant therapies. In this study, we demonstrate that the combination of sub-lethal concentrations of chemotherapeutic agents prior to freezing (-15 degrees C) in a prostate cancer cell (PC-3) model results in enhanced efficacy over either treatment alone. Morphological analysis revealed that necrosis appeared to be the prevalent mode of cell death following adjuvant (in vitro) modeling, yet molecular analysis indicated that freezing and chemotherapy differentially activated apoptotic cascades through modulating opposing members of the Bcl-2 protein family. Freezing results in a time-dependent increase of the antiapoptotic Bcl-2 protein, while chemotherapy results in an increase of the pro-apoptotic Bax protein. Anti-apoptotic Bcl-2 protein levels increase over 3-fold following exposure to freezing. 5-Fluorouracil (5-FU) causes pro-apoptotic Bax levels to increase 2-fold during the drug exposure. The increase in Bax was also apparent following the combination of 5-FU/freezing, while Bcl-2 levels were maintained at or below control levels. This led to a shift in the Bcl-2 to Bax ratio to a pro-death tendency. Other effective cryo/chemo combinations were also found to provide similar effects. The combination of cisplatin/freezing resulted in a 4-fold increase in the ratio of Bax to Bcl-2 when compared to controls, which represented a 2-fold increase over the 5-FU/freezing-combination model. This increase may contribute to the continued reduction in cell number observed during the 13-day recovery period. Additionally, the addition of an apoptotic caspase inhibitor was not able to protect cultures from cell death following combination treatment. In conclusion, the data suggest that both Bcl-2 and Bax may, not only, play an important role in the efficacy of the cryo/chemo combination, but also the balance between the two may determine the role and extent of system destruction.
authors.affiliation: Institute of Biomedical Technology, State University of New York, Binghamton, NY 13902-6000, USA.
authors.forename: Dominic M
authors.initials: DM
authors.lastname: Clarke
authors.forename: John M
authors.initials: JM
authors.lastname: Baust
authors.forename: Robert G
authors.initials: RG
authors.lastname: Van Buskirk
authors.forename: John G
authors.initials: JG
authors.lastname: Baust
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D017024:Chemotherapy, Adjuvant; D002945:Cisplatin / Q000627:therapeutic use; D003452:Cryosurgery; D005472:Fluorouracil / Q000627:therapeutic use; D005615:Freezing; D006801:Humans; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009336:Necrosis; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology / Q000601:surgery*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051028:bcl-2-Associated X Protein
chemical_list: D000970:Antineoplastic Agents; C494826:BAX protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D002945:Cisplatin; D005472:Fluorouracil