TY - JOUR
T1 - PDK1 attenuation fails to prevent tumor formation in PTEN-deficient transgenic mouse models
AU - Ellwood-Yen, Katharine
AU - Keilhack, Heike
AU - Kunii, Kaiko
AU - Dolinski, Brian
AU - Connor, Yamicia
AU - Hu, Kun
AU - Nagashima, Kumiko
AU - O'Hare, Erin
AU - Erkul, Yusuf
AU - Di Bacco, Alessandra
AU - Gargano, Diana
AU - Shomer, Nirah H.
AU - Angagaw, Minilik
AU - Leccese, Erica
AU - Andrade, Paula
AU - Hurd, Melissa
AU - Shin, Myung K.
AU - Vogt, Thomas F.
AU - Northrup, Alan
AU - Bobkova, Ekaterina V.
AU - Kasibhatla, Shailaja
AU - Bronson, Roderick T.
AU - Scott, Martin L.
AU - Draetta, Giulio
AU - Richon, Victoria
AU - Kohl, Nancy
AU - Blume-Jensen, Peter
AU - Andersen, Jannik N.
AU - Kraus, Manfred
PY - 2011/4/15
Y1 - 2011/4/15
N2 - PDK1 activates AKT suggesting that PDK1 inhibition might suppress tumor development. However, while PDK1 has been investigated intensively as an oncology target, selective inhibitors suitable for in vivo studies have remained elusive. In this study we present the results of in vivo PDK1 inhibition through a universally applicable RNAi approach for functional drug target validation in oncogenic pathway contexts. This approach, which relies on doxycycline-inducible shRNA expression from the Rosa26 locus, is ideal for functional studies of genes like PDK1 where constitutive mouse models lead to strong developmental phenotypes or embryonic lethality. We achieved more than 90% PDK1 knockdown in vivo, a level sufficient to impact physiological functions resulting in hyperinsulinemia and hyperglycemia. This phenotype was reversible on PDK1 reexpression. Unexpectedly, longterm PDK1 knockdown revealed a lack of potent antitumor efficacy in 3 different mouse models of PTENdeficient cancer. Thus, despite efficient PDK1 knockdown, inhibition of the PI3K pathway was marginal suggesting that PDK1 was not a rate limiting factor. Ex vivo analysis of pharmacological inhibitors revealed that AKT and mTOR inhibitors undergoing clinical development are more effective than PDK1 inhibitors at blocking activated PI3K pathway signaling. Taken together our findings weaken the widely held expectation that PDK1 represents an appealing oncology target.
AB - PDK1 activates AKT suggesting that PDK1 inhibition might suppress tumor development. However, while PDK1 has been investigated intensively as an oncology target, selective inhibitors suitable for in vivo studies have remained elusive. In this study we present the results of in vivo PDK1 inhibition through a universally applicable RNAi approach for functional drug target validation in oncogenic pathway contexts. This approach, which relies on doxycycline-inducible shRNA expression from the Rosa26 locus, is ideal for functional studies of genes like PDK1 where constitutive mouse models lead to strong developmental phenotypes or embryonic lethality. We achieved more than 90% PDK1 knockdown in vivo, a level sufficient to impact physiological functions resulting in hyperinsulinemia and hyperglycemia. This phenotype was reversible on PDK1 reexpression. Unexpectedly, longterm PDK1 knockdown revealed a lack of potent antitumor efficacy in 3 different mouse models of PTENdeficient cancer. Thus, despite efficient PDK1 knockdown, inhibition of the PI3K pathway was marginal suggesting that PDK1 was not a rate limiting factor. Ex vivo analysis of pharmacological inhibitors revealed that AKT and mTOR inhibitors undergoing clinical development are more effective than PDK1 inhibitors at blocking activated PI3K pathway signaling. Taken together our findings weaken the widely held expectation that PDK1 represents an appealing oncology target.
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U2 - 10.1158/0008-5472.CAN-10-2282
DO - 10.1158/0008-5472.CAN-10-2282
M3 - Article
C2 - 21493594
AN - SCOPUS:79954588932
SN - 0008-5472
VL - 71
SP - 3052
EP - 3065
JO - Cancer Research
JF - Cancer Research
IS - 8
ER -