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Overcoming Chemoresistance in Pancreatic Cancer: Targeting the Apoptotic Protein Machinery using Raloxifene
Author(s) -
Chand Pritika,
Ho Jenny,
Burunova Esther,
Kardashova Tatyana,
Malhotra Ashim
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.785.8
Subject(s) - raloxifene , apoptosis , pancreatic cancer , cancer research , immunoprecipitation , chemistry , estrogen receptor , tamoxifen , antiestrogen , microbiology and biotechnology , biology , medicine , cancer , antibody , biochemistry , breast cancer , immunology
Pancreatic cancer is chemoresistant, with the lowest 5‐year survival rate of all cancers (5%). We hypothesized that differential regulation of apoptotic proteins contributed to chemoresistance in pancreatic cancer. Preliminary data showed that raloxifene, a Selective Estrogen Receptor Modulator, induced apoptosis in the human pancreatic cancer cell line MIA PaCa‐2. We investigated whether raloxifene treatment altered the 1) interaction between anti‐ and pro‐apoptotic proteins, and 2) their mitochondrial recruitment. Briefly, following a 72 hour treatment with 0, 0.05, 0.5, 5, or 20 µM raloxifene, we immunoprecipitated Bax from MIA PaCa‐2 cells, and probed the immunoprecipiate with anti‐Mcl1 L monoclonal antibody. Our results show a dose‐dependent reduction in interaction between Bax and Mcl‐1 L , indicating that raloxifene specifically reduced the recruitment of Mcl‐1 L to this protein complex. In similar experiments, but with the immunoprecipitating event reversed, immunoprecipitated anti‐apoptotic Bcl‐2, evinced increased co‐precipitated Bim. Further, raloxifene induced dose‐dependent mitochondrial translocation of Bax. Taken together, these data suggest a selective pro‐apoptotic protein effect of raloxifene. Raloxifene also resulted in cytochrome c release into the cytoplasm, and PARP, and caspase‐9 cleavage confirming activation of the mitochondrial apoptotic pathway. In conclusion, raloxifene altered mitochondrial recruitment and molecular interaction between pro‐ and anti‐apoptotic proteins.