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How moderate changes in Akt T-loop phosphorylation impact on tumorigenesis and insulin resistance.

Wullschleger S, Sakamoto K, Johnstone L, Duce S, Fleming S, Alessi DR - Dis Model Mech (2010)

Bottom Line: Using insulin-resistant PDK1(K465E/K465E) PH domain knock-in mice, we found that introducing the PTEN(+/-) mutation to slightly stimulate Akt restored normal insulin sensitivity.This was also accompanied by slower growth of B cell follicular lymphomas, as monitored by magnetic resonance imaging.Our findings imply that signal transduction inhibitors that lead to a modest reduction in Akt activity would not only delay onset of tumours possessing elevated phosphoinositide 3-kinase pathway activity but would also reduce the growth rate of developed tumours.

View Article: PubMed Central - PubMed

Affiliation: MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.

ABSTRACT
The Akt signalling pathway plays vital roles in controlling cellular responses to insulin as well as in proliferation and survival. Inhibition of Akt signalling leads to insulin resistance and type 2 diabetes, whereas hyperactivation of Akt promotes tumorigenesis. In this study, we investigate how modest changes in the activity of the Akt signalling pathway, to an extent that might be achieved by drug treatment, would impact on insulin resistance and tumorigenesis. Using insulin-resistant PDK1(K465E/K465E) PH domain knock-in mice, we found that introducing the PTEN(+/-) mutation to slightly stimulate Akt restored normal insulin sensitivity. Introducing the PDK1(K465E/K465E) PH domain knock-in mutation into cancer-prone PTEN(+/-) mice, lowered Akt activity only by about 50%, but led to a delay in tumour onset of ∼4 months in a broad range of tumours. This was also accompanied by slower growth of B cell follicular lymphomas, as monitored by magnetic resonance imaging. Our findings imply that signal transduction inhibitors that lead to a modest reduction in Akt activity would not only delay onset of tumours possessing elevated phosphoinositide 3-kinase pathway activity but would also reduce the growth rate of developed tumours.

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Delayed tumour formation in PDK1K465E/K465EPTEN+/− mice. (A) Incidence curve of tumour formation. Mice were maintained under standard husbandry conditions and the percentage of mice at each age with visible tumours recorded (B cell follicular lymphoma). The broken lines indicate mean age for 50% of animals to develop tumours. P-values were obtained by Fisher’s exact test comparing PDK1+/+ PTEN+/− with PDK1K465E/K465E PTEN+/− mice: P<0.003 for each data point from 7 to 12 months, P<0.05 for each data point from 12.5 to 13.5 months. PDK1+/+ PTEN+/+ n=28, PDK1+/+ PTEN+/− n=27, PDK1K465E/K465E PTEN+/+ n=27, PDK1K465E/K465E PTEN+/− n=26. (B) Representative sections of H&E (hematoxylin and eosin) staining (2× and 20× objective) and immunohistochemisty of lymphomas using the indicated antibodies. The lymphomas were all classified as B cell follicular lymphoma by the Bethesda criteria. (C) Representative sections of H&E staining of intestinal polyps (2× and 20× objective), phaeochromocytoma (20× objective) and prostate carcinoma (20×objective).
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f3-0040095: Delayed tumour formation in PDK1K465E/K465EPTEN+/− mice. (A) Incidence curve of tumour formation. Mice were maintained under standard husbandry conditions and the percentage of mice at each age with visible tumours recorded (B cell follicular lymphoma). The broken lines indicate mean age for 50% of animals to develop tumours. P-values were obtained by Fisher’s exact test comparing PDK1+/+ PTEN+/− with PDK1K465E/K465E PTEN+/− mice: P<0.003 for each data point from 7 to 12 months, P<0.05 for each data point from 12.5 to 13.5 months. PDK1+/+ PTEN+/+ n=28, PDK1+/+ PTEN+/− n=27, PDK1K465E/K465E PTEN+/+ n=27, PDK1K465E/K465E PTEN+/− n=26. (B) Representative sections of H&E (hematoxylin and eosin) staining (2× and 20× objective) and immunohistochemisty of lymphomas using the indicated antibodies. The lymphomas were all classified as B cell follicular lymphoma by the Bethesda criteria. (C) Representative sections of H&E staining of intestinal polyps (2× and 20× objective), phaeochromocytoma (20× objective) and prostate carcinoma (20×objective).

Mentions: We next sought to define how a modest reduction in Akt signalling, which results from introducing the PDK1-PH domain K465E mutation, impinges on tumour development in PTEN+/− animals. We monitored groups of ∼25 PDK1+/+PTEN+/+, PDK1K465E/K465EPTEN+/+, PDK1+/+PTEN+/− and PDK1K465E/K465EPTEN+/− animals for tumour development. Animals were sacrificed when they exhibited large externally palpable tumours, reduced body weight, became unwell, or reached 14 months of age. A necropsy was performed, the tissues fixed in 10% formalin and subjected to a detailed histopathological examination. By 14 months of age, wild-type PDK1+/+PTEN+/+ and PDK1K465E/K465EPTEN+/+ mice displayed no significant tumours (Fig. 3A). Consistent with previous work (Podsypanina et al., 1999), tumour development in PDK1+/+PTEN+/− mice was observed at ∼5 months of age, and by 10 months of age ∼90% had one or more tumours. Strikingly, the PDK1K465E/K465EPTEN+/− mice developed tumours significantly later, commencing at 7 months of age. At 10 months of age, only ∼35% of the PDK1K465E/K465EPTEN+/− mice had developed tumours (Fig. 3A). These data demonstrate that tumour initiation in PDK1K465E/K465EPTEN+/− was delayed by 3–4 months compared with PDK1+/+PTEN+/− mice. The types and morphology of tumours arising in PTEN+/− mice with either wild-type PDK1 or PDK1-PH domain mutation were similar (Table 1). Comparing the incidence of detected tumours in much younger PDK1+/+PTEN+/−mice with older PDK1K465E/K465EPTEN+/− animals did not suggest a major difference in the frequency of different tumours. We detected a significant difference in tumour formation in B cell follicular lymphomas, which were found at ∼25% lower incidence in the older PDK1K465E/K465EPTEN+/− mice compared with younger PDK1+/+PTEN+/− animals (Table 1). We also found a lower incidence rate for the formation of intestinal polyps, phaeochromocytoma and prostate carcinoma in PDK1K465E/K465EPTEN+/− mice compared with PDK1+/+PTEN+/− mice (Table 1), indicating that inhibition of Akt activity might have a broad spectrum of action in tumour formation.


How moderate changes in Akt T-loop phosphorylation impact on tumorigenesis and insulin resistance.

Wullschleger S, Sakamoto K, Johnstone L, Duce S, Fleming S, Alessi DR - Dis Model Mech (2010)

Delayed tumour formation in PDK1K465E/K465EPTEN+/− mice. (A) Incidence curve of tumour formation. Mice were maintained under standard husbandry conditions and the percentage of mice at each age with visible tumours recorded (B cell follicular lymphoma). The broken lines indicate mean age for 50% of animals to develop tumours. P-values were obtained by Fisher’s exact test comparing PDK1+/+ PTEN+/− with PDK1K465E/K465E PTEN+/− mice: P<0.003 for each data point from 7 to 12 months, P<0.05 for each data point from 12.5 to 13.5 months. PDK1+/+ PTEN+/+ n=28, PDK1+/+ PTEN+/− n=27, PDK1K465E/K465E PTEN+/+ n=27, PDK1K465E/K465E PTEN+/− n=26. (B) Representative sections of H&E (hematoxylin and eosin) staining (2× and 20× objective) and immunohistochemisty of lymphomas using the indicated antibodies. The lymphomas were all classified as B cell follicular lymphoma by the Bethesda criteria. (C) Representative sections of H&E staining of intestinal polyps (2× and 20× objective), phaeochromocytoma (20× objective) and prostate carcinoma (20×objective).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3008965&req=5

f3-0040095: Delayed tumour formation in PDK1K465E/K465EPTEN+/− mice. (A) Incidence curve of tumour formation. Mice were maintained under standard husbandry conditions and the percentage of mice at each age with visible tumours recorded (B cell follicular lymphoma). The broken lines indicate mean age for 50% of animals to develop tumours. P-values were obtained by Fisher’s exact test comparing PDK1+/+ PTEN+/− with PDK1K465E/K465E PTEN+/− mice: P<0.003 for each data point from 7 to 12 months, P<0.05 for each data point from 12.5 to 13.5 months. PDK1+/+ PTEN+/+ n=28, PDK1+/+ PTEN+/− n=27, PDK1K465E/K465E PTEN+/+ n=27, PDK1K465E/K465E PTEN+/− n=26. (B) Representative sections of H&E (hematoxylin and eosin) staining (2× and 20× objective) and immunohistochemisty of lymphomas using the indicated antibodies. The lymphomas were all classified as B cell follicular lymphoma by the Bethesda criteria. (C) Representative sections of H&E staining of intestinal polyps (2× and 20× objective), phaeochromocytoma (20× objective) and prostate carcinoma (20×objective).
Mentions: We next sought to define how a modest reduction in Akt signalling, which results from introducing the PDK1-PH domain K465E mutation, impinges on tumour development in PTEN+/− animals. We monitored groups of ∼25 PDK1+/+PTEN+/+, PDK1K465E/K465EPTEN+/+, PDK1+/+PTEN+/− and PDK1K465E/K465EPTEN+/− animals for tumour development. Animals were sacrificed when they exhibited large externally palpable tumours, reduced body weight, became unwell, or reached 14 months of age. A necropsy was performed, the tissues fixed in 10% formalin and subjected to a detailed histopathological examination. By 14 months of age, wild-type PDK1+/+PTEN+/+ and PDK1K465E/K465EPTEN+/+ mice displayed no significant tumours (Fig. 3A). Consistent with previous work (Podsypanina et al., 1999), tumour development in PDK1+/+PTEN+/− mice was observed at ∼5 months of age, and by 10 months of age ∼90% had one or more tumours. Strikingly, the PDK1K465E/K465EPTEN+/− mice developed tumours significantly later, commencing at 7 months of age. At 10 months of age, only ∼35% of the PDK1K465E/K465EPTEN+/− mice had developed tumours (Fig. 3A). These data demonstrate that tumour initiation in PDK1K465E/K465EPTEN+/− was delayed by 3–4 months compared with PDK1+/+PTEN+/− mice. The types and morphology of tumours arising in PTEN+/− mice with either wild-type PDK1 or PDK1-PH domain mutation were similar (Table 1). Comparing the incidence of detected tumours in much younger PDK1+/+PTEN+/−mice with older PDK1K465E/K465EPTEN+/− animals did not suggest a major difference in the frequency of different tumours. We detected a significant difference in tumour formation in B cell follicular lymphomas, which were found at ∼25% lower incidence in the older PDK1K465E/K465EPTEN+/− mice compared with younger PDK1+/+PTEN+/− animals (Table 1). We also found a lower incidence rate for the formation of intestinal polyps, phaeochromocytoma and prostate carcinoma in PDK1K465E/K465EPTEN+/− mice compared with PDK1+/+PTEN+/− mice (Table 1), indicating that inhibition of Akt activity might have a broad spectrum of action in tumour formation.

Bottom Line: Using insulin-resistant PDK1(K465E/K465E) PH domain knock-in mice, we found that introducing the PTEN(+/-) mutation to slightly stimulate Akt restored normal insulin sensitivity.This was also accompanied by slower growth of B cell follicular lymphomas, as monitored by magnetic resonance imaging.Our findings imply that signal transduction inhibitors that lead to a modest reduction in Akt activity would not only delay onset of tumours possessing elevated phosphoinositide 3-kinase pathway activity but would also reduce the growth rate of developed tumours.

View Article: PubMed Central - PubMed

Affiliation: MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.

ABSTRACT
The Akt signalling pathway plays vital roles in controlling cellular responses to insulin as well as in proliferation and survival. Inhibition of Akt signalling leads to insulin resistance and type 2 diabetes, whereas hyperactivation of Akt promotes tumorigenesis. In this study, we investigate how modest changes in the activity of the Akt signalling pathway, to an extent that might be achieved by drug treatment, would impact on insulin resistance and tumorigenesis. Using insulin-resistant PDK1(K465E/K465E) PH domain knock-in mice, we found that introducing the PTEN(+/-) mutation to slightly stimulate Akt restored normal insulin sensitivity. Introducing the PDK1(K465E/K465E) PH domain knock-in mutation into cancer-prone PTEN(+/-) mice, lowered Akt activity only by about 50%, but led to a delay in tumour onset of ∼4 months in a broad range of tumours. This was also accompanied by slower growth of B cell follicular lymphomas, as monitored by magnetic resonance imaging. Our findings imply that signal transduction inhibitors that lead to a modest reduction in Akt activity would not only delay onset of tumours possessing elevated phosphoinositide 3-kinase pathway activity but would also reduce the growth rate of developed tumours.

Show MeSH
Related in: MedlinePlus