Targeting AKT with the proapoptotic peptide, TAT-CTMP: a novel strategy for the treatment of human pancreatic adenocarcinoma.
Pancreatic adenocarcinoma carries an ominous prognosis and has little effective treatment. Several studies have demonstrated that the potently antiapoptotic phosphatidyl inositol 3'-kinase (PI3K)-protein kinase B/AKT pathway is active in pancreas cancer. A recent study identified an endogenous AKT antagonist, carboxyl terminal modulator protein (CTMP). CTMP inhibits the phosphorylation of AKT, preventing full activation of the kinase. We screened several cell permeable peptides from the N-terminal domain of CTMP (termed TAT-CTMP1-4) in vitro and found one that caused significant apoptosis in pancreatic adenocarcinoma cell lines. An inactive variant of this peptide was synthesized and used as a negative control. In all cell lines tested, TAT-CTMP4 induced a dose-dependent increase in apoptosis as detected by %-TUNEL positive cells and %-active caspase-3 (% active caspase-3 ranged from 31.2 to 61.9 at the highest dose tested (10 microM). A screening of various cell and tissue types revealed that the proapoptotic activity was highest in pancreatic adenocarcinoma. TAT-CTMP induced similar levels of active caspase-3 as several other known inducers of apoptosis: gemcitabine, radiation therapy, wortmannin and recombinant tumor necrosis factor (TNF)-alpha. No apoptosis was observed in donor human peripheral blood mononuclear cells (PBMC, p < 0.01). We further showed that TAT-CTMP4 could augment either gemcitabine chemotherapy or radiation therapy, standard therapies for pancreas cancer. Pancreatic adenocarcinoma xenografts treated with a single dose of TAT-CTMP4 demonstrated a marked increase in caspase-3 positive tumor cells when compared with untreated controls. Additionally, pancreatic adenocarcinoma allografts treated with intratumoral TAT-CTMP and systemic gemcitabine displayed a significantly smaller tumor burden while undergoing treatment than mice in control groups (p < 0.001). These data indicate that inhibiting AKT with CTMP may be of therapeutic benefit in the treatment of pancreatic adenocarcinoma and, when combined with established therapies, may result in an increase in tumor cell death.
Simon
Peter O
PO
Department of Surgery, Washington University School of Medicine, St Louis, MO 63110, USA.
McDunn
Jonathan E
JE
Kashiwagi
Hiroyuki
H
Chang
Katherine
K
Goedegebuure
Peter S
PS
Hotchkiss
Richard S
RS
Hawkins
William G
WG
D048868:Adaptor Proteins, Signal Transducing / Q000494:pharmacology*; D000230:Adenocarcinoma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D007124:Immunoenzyme Techniques; D020287:In Situ Nick-End Labeling; D008565:Membrane Proteins / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010446:Peptide Fragments / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011836:Radiation Tolerance / Q000187:drug effects; D013869:Thiolester Hydrolases; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays; D054322:tat Gene Products, Human Immunodeficiency Virus; D000093542:Gemcitabine
D048868:Adaptor Proteins, Signal Transducing; D000964:Antimetabolites, Antineoplastic; D008565:Membrane Proteins; D010446:Peptide Fragments; D054322:tat Gene Products, Human Immunodeficiency Virus; D003841:Deoxycytidine; C494918:AKT1 protein, human; D051057:Proto-Oncogene Proteins c-akt; C437985:THEM4 protein, human; D013869:Thiolester Hydrolases; D020169:Caspases; D000093542:Gemcitabine