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Inhibiting PI3K reduces mammary tumor growth and induces hyperglycemia in a mouse model of insulin resistance and hyperinsulinemia.

Gallagher EJ, Fierz Y, Vijayakumar A, Haddad N, Yakar S, LeRoith D - Oncogene (2011)

Bottom Line: NVP-BKM120 treatment decreased phosphorylation of Akt and S6 ribosomal protein (S6rp); no change in Erk1/2 phosphorylation was seen.Therefore, we examined whether the oral PI3K/mTOR inhibitor NVP-BEZ235 augmented the tumor suppressing effects of PI3K inhibition.We also investigated the effect of targeted PI3K/mTOR inhibition on PI3K/Akt/mTOR and Erk1/2 signaling, and the potential effects on glycemia.

View Article: PubMed Central - PubMed

Affiliation: Division of Endocrinology, Diabetes and Bone Disease, Mount Sinai School of Medicine, New York, NY 10029, USA.

ABSTRACT
Women with type 2 diabetes mellitus (T2DM) are at a greater risk of developing and dying from breast cancer than women without T2DM. Insulin resistance and hyperinsulinemia underlie the pathogenesis of T2DM. In the MKR mouse model of insulin resistance, we have previously shown increased activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR pathway in association with accelerated mammary tumor growth. In this study, we demonstrate that inhibiting PI3K with the oral pan-class I PI3K inhibitor, NVP-BKM120 reduced the growth of Met-1 and MCNeuA mammary tumor orthografts in the MKR mouse. NVP-BKM120 treatment decreased phosphorylation of Akt and S6 ribosomal protein (S6rp); no change in Erk1/2 phosphorylation was seen. Hyperglycemia, hypertriglyceridemia and greater hyperinsulinemia developed in the MKR mice treated with NVP-BKM120. We previously reported reduced tumor growth using intraperitoneal rapamycin in the MKR mouse, with the development of hyperglycemia and hypertriglyceridemia. Therefore, we examined whether the oral PI3K/mTOR inhibitor NVP-BEZ235 augmented the tumor suppressing effects of PI3K inhibition. We also investigated the effect of targeted PI3K/mTOR inhibition on PI3K/Akt/mTOR and Erk1/2 signaling, and the potential effects on glycemia. NVP-BEZ235 suppressed the growth of Met-1 and MCNeuA tumor orthografts, and decreased Akt and S6rp phosphorylation, despite increased Erk1/2 phosphorylation in Met-1 orthografts of MKR mice. Less marked hyperglycemia and hyperinsulinemia developed with NVP-BEZ235 than NVP-BKM120. Overall, the results of this study demonstrated that inhibiting PI3K/Akt/mTOR signaling with the oral agents NVP-BKM120 and NVP-BEZ235 decreased mammary tumor growth in the hyperinsulinemic MKR mouse. Inhibiting PI3K alone led to more severe metabolic derangement than inhibiting both PI3K and mTOR. Therefore, PI3K may be an important target for the treatment of breast cancer in women with insulin resistance. Monitoring for hyperglycemia and dyslipidemia should be considered when using these agents in humans, given the metabolic changes detected in this study.

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Treatment with NVP-BKM120 reduced serine phosphorylation of Akt and S6 ribosomal protein in MCNeuA and Met-1 tumors treated with NVP- BKM120. Protein extracts from MCNeuA and Met-1 tumors from WT and MKR mice were size fractionated and immunoblotted against phospho(Ser 473) and total Akt, phospho(Ser 235/236) and total S6 ribosomal protein, phospho(Thr202/Tyr204)and total Erk1/2 (2A, 2B, 2G, 2H). Representative western blot analyses are displayed for MCNeuA tumors (2A and 2G) and Met-1 tumors (2B and 2H). Figures 2C–2F, 2I, 2J display the densitometric analyses of phosphorylated Akt normalized to total Akt, phosphorylated S6rp normalized to total S6rp levels, and phosphorylated Erk1/2 normalized to total Erk1/2, for MCNeuA and Met-1 tumors. Data in 2C–2F, 2I, 2J are presented as a fold change in the mean (±SEM) of each group compared to the WT vehicle treated group. * P<0.05 between groups. Statistically significant increases in Akt phosphorylation normalized to total Akt in MCNeuA and Met-1 tumors rom the MKR V mice compared to the WT V mice (not marked with asterisk in Fig 2C and 2E). (WT = wild type, V = vehicle treated, BKM = NVP-BKM120 treated).
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Figure 2: Treatment with NVP-BKM120 reduced serine phosphorylation of Akt and S6 ribosomal protein in MCNeuA and Met-1 tumors treated with NVP- BKM120. Protein extracts from MCNeuA and Met-1 tumors from WT and MKR mice were size fractionated and immunoblotted against phospho(Ser 473) and total Akt, phospho(Ser 235/236) and total S6 ribosomal protein, phospho(Thr202/Tyr204)and total Erk1/2 (2A, 2B, 2G, 2H). Representative western blot analyses are displayed for MCNeuA tumors (2A and 2G) and Met-1 tumors (2B and 2H). Figures 2C–2F, 2I, 2J display the densitometric analyses of phosphorylated Akt normalized to total Akt, phosphorylated S6rp normalized to total S6rp levels, and phosphorylated Erk1/2 normalized to total Erk1/2, for MCNeuA and Met-1 tumors. Data in 2C–2F, 2I, 2J are presented as a fold change in the mean (±SEM) of each group compared to the WT vehicle treated group. * P<0.05 between groups. Statistically significant increases in Akt phosphorylation normalized to total Akt in MCNeuA and Met-1 tumors rom the MKR V mice compared to the WT V mice (not marked with asterisk in Fig 2C and 2E). (WT = wild type, V = vehicle treated, BKM = NVP-BKM120 treated).

Mentions: Our previous studies have demonstrated an increase in phosphorylation of IRβ(Tyr1150/1151) /IGF-IRβ(Tyr1135/1136) and Akt(Ser473) in Met-1 and MCNeuA tumors inoculated into MKR mice, compared to those injected into WT FVB/N mice (Novosyadlyy 2010). No change was seen in phosphorylation of Akt(Ser473) in response to treatment with the mTOR inhibitor rapamycin (Fierz 2010). In this study, we again observed a statistically significant increase in Akt(Ser473 phosphorylation in the MKR vehicle treated group compared to the WT vehicle treated groups (Figure 2A, 2B, this difference is not marked with an asterisk on the densitometry 2C and 2E). Inhibiting PI3K resulted in decreased phosphorylation of Akt(Ser473) in both WT and MKR mice, along with decreased phosphorylation of S6 ribosomal protein(Ser235/236) (Figure 2A–2F). No change in Erk1/2(Thr202/204) phosphorylation was seen in either WT or MKR mice treated with NVP-BKM120 (Figure 2 G–J). Overall, NVP-BKM120 successfully reduces phosphorylation of Akt and S6 ribosomal protein in tumors from the MKR mouse that is known to have increased activation of Akt signaling.. No change in Erk1/2 signaling was seen after treatment with NVP-BKM120 in either cell type in MKR or WT mice.


Inhibiting PI3K reduces mammary tumor growth and induces hyperglycemia in a mouse model of insulin resistance and hyperinsulinemia.

Gallagher EJ, Fierz Y, Vijayakumar A, Haddad N, Yakar S, LeRoith D - Oncogene (2011)

Treatment with NVP-BKM120 reduced serine phosphorylation of Akt and S6 ribosomal protein in MCNeuA and Met-1 tumors treated with NVP- BKM120. Protein extracts from MCNeuA and Met-1 tumors from WT and MKR mice were size fractionated and immunoblotted against phospho(Ser 473) and total Akt, phospho(Ser 235/236) and total S6 ribosomal protein, phospho(Thr202/Tyr204)and total Erk1/2 (2A, 2B, 2G, 2H). Representative western blot analyses are displayed for MCNeuA tumors (2A and 2G) and Met-1 tumors (2B and 2H). Figures 2C–2F, 2I, 2J display the densitometric analyses of phosphorylated Akt normalized to total Akt, phosphorylated S6rp normalized to total S6rp levels, and phosphorylated Erk1/2 normalized to total Erk1/2, for MCNeuA and Met-1 tumors. Data in 2C–2F, 2I, 2J are presented as a fold change in the mean (±SEM) of each group compared to the WT vehicle treated group. * P<0.05 between groups. Statistically significant increases in Akt phosphorylation normalized to total Akt in MCNeuA and Met-1 tumors rom the MKR V mice compared to the WT V mice (not marked with asterisk in Fig 2C and 2E). (WT = wild type, V = vehicle treated, BKM = NVP-BKM120 treated).
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Figure 2: Treatment with NVP-BKM120 reduced serine phosphorylation of Akt and S6 ribosomal protein in MCNeuA and Met-1 tumors treated with NVP- BKM120. Protein extracts from MCNeuA and Met-1 tumors from WT and MKR mice were size fractionated and immunoblotted against phospho(Ser 473) and total Akt, phospho(Ser 235/236) and total S6 ribosomal protein, phospho(Thr202/Tyr204)and total Erk1/2 (2A, 2B, 2G, 2H). Representative western blot analyses are displayed for MCNeuA tumors (2A and 2G) and Met-1 tumors (2B and 2H). Figures 2C–2F, 2I, 2J display the densitometric analyses of phosphorylated Akt normalized to total Akt, phosphorylated S6rp normalized to total S6rp levels, and phosphorylated Erk1/2 normalized to total Erk1/2, for MCNeuA and Met-1 tumors. Data in 2C–2F, 2I, 2J are presented as a fold change in the mean (±SEM) of each group compared to the WT vehicle treated group. * P<0.05 between groups. Statistically significant increases in Akt phosphorylation normalized to total Akt in MCNeuA and Met-1 tumors rom the MKR V mice compared to the WT V mice (not marked with asterisk in Fig 2C and 2E). (WT = wild type, V = vehicle treated, BKM = NVP-BKM120 treated).
Mentions: Our previous studies have demonstrated an increase in phosphorylation of IRβ(Tyr1150/1151) /IGF-IRβ(Tyr1135/1136) and Akt(Ser473) in Met-1 and MCNeuA tumors inoculated into MKR mice, compared to those injected into WT FVB/N mice (Novosyadlyy 2010). No change was seen in phosphorylation of Akt(Ser473) in response to treatment with the mTOR inhibitor rapamycin (Fierz 2010). In this study, we again observed a statistically significant increase in Akt(Ser473 phosphorylation in the MKR vehicle treated group compared to the WT vehicle treated groups (Figure 2A, 2B, this difference is not marked with an asterisk on the densitometry 2C and 2E). Inhibiting PI3K resulted in decreased phosphorylation of Akt(Ser473) in both WT and MKR mice, along with decreased phosphorylation of S6 ribosomal protein(Ser235/236) (Figure 2A–2F). No change in Erk1/2(Thr202/204) phosphorylation was seen in either WT or MKR mice treated with NVP-BKM120 (Figure 2 G–J). Overall, NVP-BKM120 successfully reduces phosphorylation of Akt and S6 ribosomal protein in tumors from the MKR mouse that is known to have increased activation of Akt signaling.. No change in Erk1/2 signaling was seen after treatment with NVP-BKM120 in either cell type in MKR or WT mice.

Bottom Line: NVP-BKM120 treatment decreased phosphorylation of Akt and S6 ribosomal protein (S6rp); no change in Erk1/2 phosphorylation was seen.Therefore, we examined whether the oral PI3K/mTOR inhibitor NVP-BEZ235 augmented the tumor suppressing effects of PI3K inhibition.We also investigated the effect of targeted PI3K/mTOR inhibition on PI3K/Akt/mTOR and Erk1/2 signaling, and the potential effects on glycemia.

View Article: PubMed Central - PubMed

Affiliation: Division of Endocrinology, Diabetes and Bone Disease, Mount Sinai School of Medicine, New York, NY 10029, USA.

ABSTRACT
Women with type 2 diabetes mellitus (T2DM) are at a greater risk of developing and dying from breast cancer than women without T2DM. Insulin resistance and hyperinsulinemia underlie the pathogenesis of T2DM. In the MKR mouse model of insulin resistance, we have previously shown increased activation of the phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR pathway in association with accelerated mammary tumor growth. In this study, we demonstrate that inhibiting PI3K with the oral pan-class I PI3K inhibitor, NVP-BKM120 reduced the growth of Met-1 and MCNeuA mammary tumor orthografts in the MKR mouse. NVP-BKM120 treatment decreased phosphorylation of Akt and S6 ribosomal protein (S6rp); no change in Erk1/2 phosphorylation was seen. Hyperglycemia, hypertriglyceridemia and greater hyperinsulinemia developed in the MKR mice treated with NVP-BKM120. We previously reported reduced tumor growth using intraperitoneal rapamycin in the MKR mouse, with the development of hyperglycemia and hypertriglyceridemia. Therefore, we examined whether the oral PI3K/mTOR inhibitor NVP-BEZ235 augmented the tumor suppressing effects of PI3K inhibition. We also investigated the effect of targeted PI3K/mTOR inhibition on PI3K/Akt/mTOR and Erk1/2 signaling, and the potential effects on glycemia. NVP-BEZ235 suppressed the growth of Met-1 and MCNeuA tumor orthografts, and decreased Akt and S6rp phosphorylation, despite increased Erk1/2 phosphorylation in Met-1 orthografts of MKR mice. Less marked hyperglycemia and hyperinsulinemia developed with NVP-BEZ235 than NVP-BKM120. Overall, the results of this study demonstrated that inhibiting PI3K/Akt/mTOR signaling with the oral agents NVP-BKM120 and NVP-BEZ235 decreased mammary tumor growth in the hyperinsulinemic MKR mouse. Inhibiting PI3K alone led to more severe metabolic derangement than inhibiting both PI3K and mTOR. Therefore, PI3K may be an important target for the treatment of breast cancer in women with insulin resistance. Monitoring for hyperglycemia and dyslipidemia should be considered when using these agents in humans, given the metabolic changes detected in this study.

Show MeSH
Related in: MedlinePlus