title: Ectopically expressed perforin-1 is proapoptotic in tumor cell lines by increasing caspase-3 activity and the nuclear translocation of cytochrome C.
abstract: Perforin-1 (PRF), a cytotoxic lymphocyte pore-forming protein, plays an important role in the action of cytotoxic T cells and natural killer cells in that it causes the lysis of abnormal body cells and the elimination of virus-infected cells and tumors. Upon degranulation, PRF inserts itself into the target cell's plasma membrane, forming a pore. The subsequent translocation of pro-apoptotic granzymes (including granzyme B, A, M et al.) into the cytoplasm provides the proteases with access to numerous protein substrates that promote apoptosis after cleavage. These proteases are believed to be the main executioners of target cell apoptosis. Although the PRF and granzyme components are both critical to this process and in some way involved in inducing cell death in target cells, the inhibition of tumor growth could still be efficient in granzyme-deficient mice. It is unclear whether PRF alone can suppress tumors. In this study, we discovered that forced ectopic expression of PRF alone, in the absence of granzymes, could mediate cell death in cancer cells. Notably, transient expression of both full-length and truncated active-form PRF in human Hep G2, SK-BR-3, and HeLa cells was found to induce apparent cell growth inhibition and cell death, as evidenced by chromosome condensation and DNA fragmentation, increased caspase-3 activity, and the release of apoptosis inducing factor (AIF) and cytochrome c from the mitochondria. This PRF-induced cell death could be abrogated by pan-caspase inhibitor (Z-VAD) and mitochondria protector (TAT-BH4). The implication of these results is that ectopically expressed PRF has apoptosis-inducing abilities, and PRF alone is sufficient to induce apoptotic cell death in cells with ectopic expression. Taking this into consideration, our results suggest the possibility of using PRF as a pro-apoptotic gene for tumor therapeutics.
authors: State Key Laboratory of Cancer Biology, Departments of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fourth Military Medical University, Xi'an, China.
authors: Li-Feng
authors: LF
authors: Wang
authors: Fang
authors: F
authors: Wang
authors: Jun-Tang
authors: JT
authors: Li
authors: Wei-Hong
authors: WH
authors: Wen
authors: Jing
authors: J
authors: Zhao
authors: Lin-Tao
authors: LT
authors: Jia
authors: Yan-Ling
authors: YL
authors: Meng
authors: Yun-Xin
authors: YX
authors: Cao
authors: Li-Bo
authors: LB
authors: Yao
authors: Si-Yi
authors: SY
authors: Chen
authors: Yan-Ming
authors: YM
authors: Xu
authors: An-Gang
authors: AG
authors: Yang
mesh_terms: D017209:Apoptosis / Q000235:genetics / Q000502:physiology*; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D056945:Hep G2 Cells; D006801:Humans; D020287:In Situ Nick-End Labeling; D054353:Perforin / Q000235:genetics / Q000378:metabolism*; D010718:Phosphatidylserines / Q000494:pharmacology
chemical_list: D051033:Apoptosis Inducing Factor; D010718:Phosphatidylserines; D054353:Perforin; D045304:Cytochromes c; D053148:Caspase 3