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Effective use of PI3K and MEK inhibitors to treat mutant Kras G12D and PIK3CA H1047R murine lung cancers.

Engelman JA, Chen L, Tan X, Crosby K, Guimaraes AR, Upadhyay R, Maira M, McNamara K, Perera SA, Song Y, Chirieac LR, Kaur R, Lightbown A, Simendinger J, Li T, Padera RF, García-Echeverría C, Weissleder R, Mahmood U, Cantley LC, Wong KK - Nat. Med. (2008)

Bottom Line: Somatic mutations that activate phosphoinositide 3-kinase (PI3K) have been identified in the p110-alpha catalytic subunit (encoded by PIK3CA).They are most frequently observed in two hotspots: the helical domain (E545K and E542K) and the kinase domain (H1047R).Treatment of these tumors with NVP-BEZ235, a dual pan-PI3K and mammalian target of rapamycin (mTOR) inhibitor in clinical development, led to marked tumor regression as shown by positron emission tomography-computed tomography, magnetic resonance imaging and microscopic examination.

View Article: PubMed Central - PubMed

ABSTRACT
Somatic mutations that activate phosphoinositide 3-kinase (PI3K) have been identified in the p110-alpha catalytic subunit (encoded by PIK3CA). They are most frequently observed in two hotspots: the helical domain (E545K and E542K) and the kinase domain (H1047R). Although the p110-alpha mutants are transforming in vitro, their oncogenic potential has not been assessed in genetically engineered mouse models. Furthermore, clinical trials with PI3K inhibitors have recently been initiated, and it is unknown if their efficacy will be restricted to specific, genetically defined malignancies. In this study, we engineered a mouse model of lung adenocarcinomas initiated and maintained by expression of p110-alpha H1047R. Treatment of these tumors with NVP-BEZ235, a dual pan-PI3K and mammalian target of rapamycin (mTOR) inhibitor in clinical development, led to marked tumor regression as shown by positron emission tomography-computed tomography, magnetic resonance imaging and microscopic examination. In contrast, mouse lung cancers driven by mutant Kras did not substantially respond to single-agent NVP-BEZ235. However, when NVP-BEZ235 was combined with a mitogen-activated protein kinase kinase (MEK) inhibitor, ARRY-142886, there was marked synergy in shrinking these Kras-mutant cancers. These in vivo studies suggest that inhibitors of the PI3K-mTOR pathway may be active in cancers with PIK3CA mutations and, when combined with MEK inhibitors, may effectively treat KRAS mutated lung cancers.

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Combined PI3K and MEK inhibition dramatically shrinks K-Ras G12D induced lung tumors(a,b) LSL K-Ras mice were induced to develop tumors by adenoviral Cre inhalation. After the establishment of sizeable tumors (determined by MRI), mice were treated with either placebo, NVP-BEZ235 35mg/kg once daily, ARRY-142886 25mg/kg twice daily, or NVP-BEZ235 35mg/kg once daily and ARRY-142886 25mg/kg once daily for two weeks. (a) Representative axial MRIs of the chest are shown. Scales is 4.5 mm. (b) The average tumor volumes of three mice in each treatment group after 2 weeks are shown relative to pretreatment tumor volumes. (c,d) Mice were treated as in (a) for 1.5 days. Six hours after their dose on day two of treatment, the animals were sacrificed. (c) One lung was snap-frozen in liquid nitrogen and assessed by western blotting using the indicated antibodies. (d) The other lung was fixed in formalin and assessed by immunohistochemistry (IHC) with the indicated antibodies. Microscopy was performed at two magnifications for the P-Akt IHC. The scale for the high magnification P-Akt IHC images is 25μM. The scale is 100μM for the other images. Hematoxylin and Eosin stains of the nodules examined by IHC are shown in the Supplemental Material (Supplementary Fig. 6).
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Figure 4: Combined PI3K and MEK inhibition dramatically shrinks K-Ras G12D induced lung tumors(a,b) LSL K-Ras mice were induced to develop tumors by adenoviral Cre inhalation. After the establishment of sizeable tumors (determined by MRI), mice were treated with either placebo, NVP-BEZ235 35mg/kg once daily, ARRY-142886 25mg/kg twice daily, or NVP-BEZ235 35mg/kg once daily and ARRY-142886 25mg/kg once daily for two weeks. (a) Representative axial MRIs of the chest are shown. Scales is 4.5 mm. (b) The average tumor volumes of three mice in each treatment group after 2 weeks are shown relative to pretreatment tumor volumes. (c,d) Mice were treated as in (a) for 1.5 days. Six hours after their dose on day two of treatment, the animals were sacrificed. (c) One lung was snap-frozen in liquid nitrogen and assessed by western blotting using the indicated antibodies. (d) The other lung was fixed in formalin and assessed by immunohistochemistry (IHC) with the indicated antibodies. Microscopy was performed at two magnifications for the P-Akt IHC. The scale for the high magnification P-Akt IHC images is 25μM. The scale is 100μM for the other images. Hematoxylin and Eosin stains of the nodules examined by IHC are shown in the Supplemental Material (Supplementary Fig. 6).

Mentions: Recently, it has become evident that cancers respond dramatically to therapies targeting receptor tyrosine kinases (RTKs) when inhibition of the RTK leads to loss of both PI3K and ERK signaling 12-15. To recapitulate this effect in the K-Ras mutant lung tumors, we treated the mice with a combination of a PI3K and a MEK inhibitors. Whereas treatment of the K-Ras mutant mice with the MEK inhibitor, ARRY-142886 16, led to only modest tumor regression, the combination led to marked synergistic tumor regression (Figs. 4a,b), and pathological analyses at the completion of treatment revealed only scant remnants of tumor nodules (Supplementary Fig. 5b). After two days of the combination treatment, there was marked downregulation of PI3K, Erk and downstream signaling as indicated by western blot analyses and IHC (Figs. 4c,d). Of note, we invariably detected low level P-Akt staining in the K-Ras G12D nodules that was impressively lost upon treatment of the mouse with NVP-BEZ235 (Fig. 4d).


Effective use of PI3K and MEK inhibitors to treat mutant Kras G12D and PIK3CA H1047R murine lung cancers.

Engelman JA, Chen L, Tan X, Crosby K, Guimaraes AR, Upadhyay R, Maira M, McNamara K, Perera SA, Song Y, Chirieac LR, Kaur R, Lightbown A, Simendinger J, Li T, Padera RF, García-Echeverría C, Weissleder R, Mahmood U, Cantley LC, Wong KK - Nat. Med. (2008)

Combined PI3K and MEK inhibition dramatically shrinks K-Ras G12D induced lung tumors(a,b) LSL K-Ras mice were induced to develop tumors by adenoviral Cre inhalation. After the establishment of sizeable tumors (determined by MRI), mice were treated with either placebo, NVP-BEZ235 35mg/kg once daily, ARRY-142886 25mg/kg twice daily, or NVP-BEZ235 35mg/kg once daily and ARRY-142886 25mg/kg once daily for two weeks. (a) Representative axial MRIs of the chest are shown. Scales is 4.5 mm. (b) The average tumor volumes of three mice in each treatment group after 2 weeks are shown relative to pretreatment tumor volumes. (c,d) Mice were treated as in (a) for 1.5 days. Six hours after their dose on day two of treatment, the animals were sacrificed. (c) One lung was snap-frozen in liquid nitrogen and assessed by western blotting using the indicated antibodies. (d) The other lung was fixed in formalin and assessed by immunohistochemistry (IHC) with the indicated antibodies. Microscopy was performed at two magnifications for the P-Akt IHC. The scale for the high magnification P-Akt IHC images is 25μM. The scale is 100μM for the other images. Hematoxylin and Eosin stains of the nodules examined by IHC are shown in the Supplemental Material (Supplementary Fig. 6).
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Related In: Results  -  Collection

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Figure 4: Combined PI3K and MEK inhibition dramatically shrinks K-Ras G12D induced lung tumors(a,b) LSL K-Ras mice were induced to develop tumors by adenoviral Cre inhalation. After the establishment of sizeable tumors (determined by MRI), mice were treated with either placebo, NVP-BEZ235 35mg/kg once daily, ARRY-142886 25mg/kg twice daily, or NVP-BEZ235 35mg/kg once daily and ARRY-142886 25mg/kg once daily for two weeks. (a) Representative axial MRIs of the chest are shown. Scales is 4.5 mm. (b) The average tumor volumes of three mice in each treatment group after 2 weeks are shown relative to pretreatment tumor volumes. (c,d) Mice were treated as in (a) for 1.5 days. Six hours after their dose on day two of treatment, the animals were sacrificed. (c) One lung was snap-frozen in liquid nitrogen and assessed by western blotting using the indicated antibodies. (d) The other lung was fixed in formalin and assessed by immunohistochemistry (IHC) with the indicated antibodies. Microscopy was performed at two magnifications for the P-Akt IHC. The scale for the high magnification P-Akt IHC images is 25μM. The scale is 100μM for the other images. Hematoxylin and Eosin stains of the nodules examined by IHC are shown in the Supplemental Material (Supplementary Fig. 6).
Mentions: Recently, it has become evident that cancers respond dramatically to therapies targeting receptor tyrosine kinases (RTKs) when inhibition of the RTK leads to loss of both PI3K and ERK signaling 12-15. To recapitulate this effect in the K-Ras mutant lung tumors, we treated the mice with a combination of a PI3K and a MEK inhibitors. Whereas treatment of the K-Ras mutant mice with the MEK inhibitor, ARRY-142886 16, led to only modest tumor regression, the combination led to marked synergistic tumor regression (Figs. 4a,b), and pathological analyses at the completion of treatment revealed only scant remnants of tumor nodules (Supplementary Fig. 5b). After two days of the combination treatment, there was marked downregulation of PI3K, Erk and downstream signaling as indicated by western blot analyses and IHC (Figs. 4c,d). Of note, we invariably detected low level P-Akt staining in the K-Ras G12D nodules that was impressively lost upon treatment of the mouse with NVP-BEZ235 (Fig. 4d).

Bottom Line: Somatic mutations that activate phosphoinositide 3-kinase (PI3K) have been identified in the p110-alpha catalytic subunit (encoded by PIK3CA).They are most frequently observed in two hotspots: the helical domain (E545K and E542K) and the kinase domain (H1047R).Treatment of these tumors with NVP-BEZ235, a dual pan-PI3K and mammalian target of rapamycin (mTOR) inhibitor in clinical development, led to marked tumor regression as shown by positron emission tomography-computed tomography, magnetic resonance imaging and microscopic examination.

View Article: PubMed Central - PubMed

ABSTRACT
Somatic mutations that activate phosphoinositide 3-kinase (PI3K) have been identified in the p110-alpha catalytic subunit (encoded by PIK3CA). They are most frequently observed in two hotspots: the helical domain (E545K and E542K) and the kinase domain (H1047R). Although the p110-alpha mutants are transforming in vitro, their oncogenic potential has not been assessed in genetically engineered mouse models. Furthermore, clinical trials with PI3K inhibitors have recently been initiated, and it is unknown if their efficacy will be restricted to specific, genetically defined malignancies. In this study, we engineered a mouse model of lung adenocarcinomas initiated and maintained by expression of p110-alpha H1047R. Treatment of these tumors with NVP-BEZ235, a dual pan-PI3K and mammalian target of rapamycin (mTOR) inhibitor in clinical development, led to marked tumor regression as shown by positron emission tomography-computed tomography, magnetic resonance imaging and microscopic examination. In contrast, mouse lung cancers driven by mutant Kras did not substantially respond to single-agent NVP-BEZ235. However, when NVP-BEZ235 was combined with a mitogen-activated protein kinase kinase (MEK) inhibitor, ARRY-142886, there was marked synergy in shrinking these Kras-mutant cancers. These in vivo studies suggest that inhibitors of the PI3K-mTOR pathway may be active in cancers with PIK3CA mutations and, when combined with MEK inhibitors, may effectively treat KRAS mutated lung cancers.

Show MeSH
Related in: MedlinePlus