Project description:This SuperSeries is composed of the following subset Series: GSE35701: CP001: Modulation of glutamine metabolism by the PI3K-PKB/c-akt-FOXO network regulates autophagy GSE35703: CP003: Modulation of glutamine metabolism by the PI3K-PKB/c-akt-FOXO network regulates autophagy Refer to individual Series
Project description:Neuroblastoma is a pediatric tumor of the peripheral sympathetic nervous system with a highly variable prognosis. Activation of the PI3K/AKT pathway in neuroblastoma is correlated with poor patient prognosis, but the precise downstream effectors mediating this effect have not been determined. Here, we identify the forkhead transcription factor FOXO3a as a key target of the PI3K/AKT pathway in neuroblastoma. FOXO3a expression was elevated in low stage neuroblastoma tumors and normal embryonal neuroblasts, but reduced in late stage neuroblastoma. Inactivation of FOXO3a by AKT was essential for neuroblastoma cell survival. Treatment of neuroblastoma cells with the dual PI3K/mTOR inhibitor PI-103 activated FOXO3a and triggered apoptosis. This effect was rescued by FOXO3a silencing. Conversely, apoptosis induced by PI-103 or the AKT inhibitor MK-2206 was potentiated by FOXO3a overexpression. Further, levels of total or phosphorylated FOXO3a correlated closely with apoptotic sensitivity to MK-2206. In clinical specimens, there was an inverse relationship between gene expression signatures regulated by PI3K signaling and FOXO3a transcriptional activity. Moreover, high PI3K activity and low FOXO3a activity were each associated with an extremely poor prognosis. Our work indicates that expression of FOXO3a and its targets offer useful prognostic markers as well as biomarkers for PI3K/AKT inhibitor efficacy in neuroblastoma. Affymetrix U133 Plus 2.0 profiling of SY5Y-TetR-FOXO3A cells treated with doxycycline and/or the PI3K/mTOR inhibitor PI-103. Each condition profiled in triplicate.
Project description:The high frequency of aberrant PI3K pathway activation in hormone receptor-positive (HR+) breast cancer has led to the development, clinical testing, and approval of the p110a-selective PI3K inhibitor alpelisib. The limited clinical efficacy of alpelisib and other PI3K inhibitors is partially attributed to the functional antagonism between PI3K and estrogen receptor (ER) signaling, which is mitigated via combined PI3K inhibition and endocrine therapy. We and others have previously demonstrated chromatin-associated mechanisms by which PI3K supports cancer development and antagonizes ER signaling through the modulation of the H3K4 methylation axis; inhibition of KDM5A promoter H3K4 demethylation and KMT2D/MLL4-directed enhancer H3K4 methylation. Here we show that inhibition of the H3K4 histone methyltransferase MLL1 in combination with PI3K inhibition impairs HR+ breast cancer clonogenicity and cell proliferation. While combined PI3K/MLL1 inhibition reduces PI3K/AKT signaling and H3K4 methylation, MLL1 inhibition increases PI3K/AKT signaling and dysregulates the expression of processes that lead to AKT activation. These data reveal a feedback loop between MLL1 and AKT whereby MLL1 inhibition reactivates AKT. We show that combined PI3K and MLL1 inhibition synergizes to cause cell death in in vitro and in vivo models of HR+ breast cancer, which is enhanced by the additional genetic ablation of the H3K4 methyltransferase and AKT target KMT2D/MLL4. Together, our data provide evidence of a feedback mechanism connecting histone methylation with AKT and may support the preclinical development and testing of pan-MLL inhibitors.
Project description:The high frequency of aberrant PI3K pathway activation in hormone receptor-positive (HR+) breast cancer has led to the development, clinical testing, and approval of the p110a-selective PI3K inhibitor alpelisib. The limited clinical efficacy of alpelisib and other PI3K inhibitors is partially attributed to the functional antagonism between PI3K and estrogen receptor (ER) signaling, which is mitigated via combined PI3K inhibition and endocrine therapy. We and others have previously demonstrated chromatin-associated mechanisms by which PI3K supports cancer development and antagonizes ER signaling through the modulation of the H3K4 methylation axis; inhibition of KDM5A promoter H3K4 demethylation and KMT2D/MLL4-directed enhancer H3K4 methylation. Here we show that inhibition of the H3K4 histone methyltransferase MLL1 in combination with PI3K inhibition impairs HR+ breast cancer clonogenicity and cell proliferation. While combined PI3K/MLL1 inhibition reduces PI3K/AKT signaling and H3K4 methylation, MLL1 inhibition increases PI3K/AKT signaling and dysregulates the expression of processes that lead to AKT activation. These data reveal a feedback loop between MLL1 and AKT whereby MLL1 inhibition reactivates AKT. We show that combined PI3K and MLL1 inhibition synergizes to cause cell death in in vitro and in vivo models of HR+ breast cancer, which is enhanced by the additional genetic ablation of the H3K4 methyltransferase and AKT target KMT2D/MLL4. Together, our data provide evidence of a feedback mechanism connecting histone methylation with AKT and may support the preclinical development and testing of pan-MLL inhibitors.
Project description:Alterations of the tumor suppressor TP53, one of the most common events in cancer, alone are insufficient for tumor development but serve as drivers of transformation. We sought to identify cooperating events through genomic analyses of a novel somatic Trp53R245W mouse model (equivalent to the TP53R248W hot spot mutation in human cancers) that recapitulates metastatic breast cancer development. We identified cooperating lesions similar to those found in human breast cancers. Moreover, we identified activation of the Pi3k/Akt/mTOR pathway in most tumors via mutations in Pten, Erbb2, Kras and/or a recurrent Pip5k1c mutation that stabilizes the Pip5k1c protein to activate Pi3k/Akt/mTOR signaling. Another PIP5K1C family member, PIP5K1A, is co-amplified with PI4KB in 18% of human breast cancer patients and both encode kinases that are responsible for production of the PI3K substrate, phosphatidylinositol 4,5-bisphosphate. Thus, the TP53R248W mutation and PI3K/Akt/mTOR signaling are major cooperative events driving breast cancer development. Additionally, we demonstrated that the upregulation of oxidative phosphorylation by Pi3k/Akt/mTOR signaling is a vulnerability in murine as well as human breast cancer cell lines. These findings advance our understanding of mutant p53-driven breast tumors and expand testable targets for breast cancer treatment.
Project description:Neuroblastoma is a pediatric tumor of the peripheral sympathetic nervous system with a highly variable prognosis. Activation of the PI3K/AKT pathway in neuroblastoma is correlated with poor patient prognosis, but the precise downstream effectors mediating this effect have not been determined. Here, we identify the forkhead transcription factor FOXO3a as a key target of the PI3K/AKT pathway in neuroblastoma. FOXO3a expression was elevated in low stage neuroblastoma tumors and normal embryonal neuroblasts, but reduced in late stage neuroblastoma. Inactivation of FOXO3a by AKT was essential for neuroblastoma cell survival. Treatment of neuroblastoma cells with the dual PI3K/mTOR inhibitor PI-103 activated FOXO3a and triggered apoptosis. This effect was rescued by FOXO3a silencing. Conversely, apoptosis induced by PI-103 or the AKT inhibitor MK-2206 was potentiated by FOXO3a overexpression. Further, levels of total or phosphorylated FOXO3a correlated closely with apoptotic sensitivity to MK-2206. In clinical specimens, there was an inverse relationship between gene expression signatures regulated by PI3K signaling and FOXO3a transcriptional activity. Moreover, high PI3K activity and low FOXO3a activity were each associated with an extremely poor prognosis. Our work indicates that expression of FOXO3a and its targets offer useful prognostic markers as well as biomarkers for PI3K/AKT inhibitor efficacy in neuroblastoma.
Project description:Hyperactivation of the phosphatydil-inositol-3' phosphate kinase (PI3K)/AKT pathway is observed in most NSCLCs, promoting proliferation, migration, invasion and resistance to therapy. AKT can be activated through several mechanisms that include loss of the negative regulator PTEN, activating mutations of the catalytic subunit of PI3K (PIK3CA) and/or mutations of AKT1 itself. However, number and identity of downstream targets of activated PI3K/AKT pathway are poorly defined. To identify the genes that are targets of constitutive PI3K/AKT signalling in lung cancer cells, we performed a comparative transcriptomic analysis of human lung epithelial cells (BEAS-2B) expressing active mutant AKT1 (AKT1-E17K), active mutant PIK3CA (PIK3CA-E545K) or that are silenced for PTEN. For each sample, 500 ng of total RNA were used to synthesize biotinylated cRNA with Illumina RNA Amplification Kit (Ambion, Austin, TX). Synthesis was carried out according to the manufacturersâ instructions. From each sample, technical triplicates were produced and 750 ng cRNA were hybridized for 18h to Human HT-12_V3_0_R1 Expression BeadChips (Illumina, San Diego, CA). Hybridized chips were washed and stained with streptavidin-conjugated Cy3 (GE Healthcare, Milan, Italy). BeadChips were dried and scanned with an Illumina Bead Array Reader (Illumina).