Human and mouse mesotheliomas exhibit elevated AKT/PKB activity, which can be targeted pharmacologically to inhibit tumor cell growth.
Malignant mesotheliomas (MMs) are very aggressive tumors that respond poorly to standard chemotherapeutic approaches. The phosphatidylinositol 3-kinase (PI3K)/AKT pathway has been implicated in tumor aggressiveness, in part by mediating cell survival and reducing sensitivity to chemotherapy. Using antibodies recognizing the phosphorylated/activated form of AKT kinases, we observed elevated phospho-AKT staining in 17 of 26 (65%) human MM specimens. In addition, AKT phosphorylation was consistently observed in MMs arising in asbestos-treated mice and in MM cell xenografts. Consistent with reports implicating hepatocyte growth factor (HGF)/Met receptor signaling in MM, all 14 human and murine MM cell lines had HGF-inducible AKT activity. One of nine human MM cell lines had elevated AKT activity under serum-starvation conditions, which was associated with a homozygous deletion of PTEN, the first reported in MM. Treatment of this cell line with the mTOR inhibitor rapamycin resulted in growth arrest in G1 phase. Treatment of MM cells with the PI3K inhibitor LY294002 in combination with cisplatin had greater efficacy in inhibiting cell proliferation and inducing apoptosis than either agent alone. Collectively, these data indicate that MMs frequently express elevated AKT activity, which may be targeted pharmacologically to enhance chemotherapeutic efficacy. These findings also suggest that mouse models of MM may be useful for future preclinical studies of pharmaceuticals targeting the PI3K/AKT pathway.
Altomare
Deborah A
DA
Human Genetics Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA.
You
Huihong
H
Xiao
Guang-Hui
GH
Ramos-Nino
Maria E
ME
Skele
Kristine L
KL
De Rienzo
Assunta
A
Jhanwar
Suresh C
SC
Mossman
Brooke T
BT
Kane
Agnes B
AB
Testa
Joseph R
JR
D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival; D004195:Disease Models, Animal; D004790:Enzyme Induction; D020869:Gene Expression Profiling; D006801:Humans; D008654:Mesothelioma / Q000201:enzymology* / Q000503:physiopathology*; D051379:Mice; D051059:PTEN Phosphohydrolase; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010744:Phosphoric Monoester Hydrolases / Q000502:physiology; D010766:Phosphorylation; D011494:Protein Kinases / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000502:physiology
D000081082:Phosphoinositide-3 Kinase Inhibitors; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; D011494:Protein Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases; D010744:Phosphoric Monoester Hydrolases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human