Specific gene expression signatures induced by the multiple oncogenic alterations that occur within the PTEN/PI3K/AKT pathway in lung cancer

Abstract

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. We found that, altogether, aberrant PI3K/AKT signalling in lung epithelial cells regulated the expression of 1,960/20,436 genes (9%), though only 30 differentially expressed genes (DEGs) (15 up-regulated, 12 down-regulated and 3 discordant) out of 20,436 that were common among BEAS-AKT1-E17K, BEAS-PIK3CA-E545K and BEAS-shPTEN cells (0.1%). Conversely, DEGs specific for mutant AKT1 were 133 (85 up-regulated; 48 down-regulated), DEGs specific for mutant PIK3CA were 502 (280 up-regulated; 222 down-regulated) and DEGs specific for PTEN loss were 1549 (799 up-regulated, 750 down-regulated). The results obtained from array analysis were confirmed by quantitative RT-PCR on selected up- and down-regulated genes (n = 10). Treatment of BEAS-C cells and the corresponding derivatives with pharmacological inhibitors of AKT (MK2206) or PI3K (LY294002) further validated the significance of our findings. Moreover, mRNA expression of selected DEGs (SGK1, IGFBP3, PEG10, GDF15, PTGES, S100P, respectively) correlated with the activation status of the PI3K/AKT pathway assessed by S473 phosphorylation in NSCLC cell lines (n = 6). Finally, we made use of Ingenuity Pathway Analysis (IPA) to investigate the relevant BioFunctions enriched by the costitutive activation of AKT1-, PI3K- or PTEN-dependent signalling in lung epithelial cells. Expectedly, the analysis of the DEGs common to all three alterations highlighted a group of BioFunctions that included Cell Proliferation of tumor cell lines (14 DEGs), Invasion of cells (10 DEGs) and Migration of tumour cell lines (10 DEGs), with a common core of 5 genes (ATF3, CDKN1A, GDF15, HBEGF and LCN2) that likely represent downstream effectors of the pro-oncogenic activities of PI3K/AKT signalling. Conversely, IPA analysis of exclusive DEGs led to the identification of different downstream effectors that are modulated by mutant AKT1 (TGFBR2, CTSZ, EMP1), mutant PIK3CA (CCND2, CDK2, IGFBP2, TRIB1) and PTEN loss (ASNS, FHL2).These findings not only shed light on the molecular mechanisms that are activated by aberrant signalling through the PI3K/AKT pathway in lung epithelial cells, but also contribute to the identification of previously unrecognised molecules whose regulation takes part in the development of lung cancer.

ST6GAL1: A key player in cancer (Review)

“…The HCC in vitro studies suggested that overexpression of ST6GAL1 in HCC cells increased activation of the PI3K/Akt signalling pathway (42). Hyper-activation of the PI3K signalling cascade is well documented in several different cancer subtypes as regulating and promoting hyper-proliferation of oncogenic cells (47)(48)(49)(50). If ST6GAL1 can activate PI3K/Akt signalling, as suggested by Zhao et al (42) this may point towards mechanistic link between ST6GAL1 upregulation and increased cellular proliferation.…”

Effect of miR-21 on Apoptosis in Lung Cancer Cell Through Inhibiting the PI3K/ Akt/NF-κB Signaling Pathway in Vitro and in Vivo

“…A number of studies showed that PI3K/AKT was involved in human lung cancer [30-33]. Previous studies identified activation of the PI3K/AKT pathway and observed it in human lung carcinomas [34, 35]. Another study showed that PI3K/Akt regulated the expression of angiogenic factors in A549 lung cancer cells [36].…”

Effect of AKT1 (p. E17K) Hotspot Mutation on Malignant Tumorigenesis and Prognosis

“…The PI3K-AKT pathway in cancer has been shown to inhibit apoptosis (Zilberman et al, 2009 ). In previous studies, it has been proposed that AKT1(E17K) mutations induce proprioceptive activation by localizing to the stromal membrane in a PI3K-independent manner (Brugge et al, 2007 ; Do et al, 2008 ), promote regeneration and activation of the cell membrane (Furukawa et al, 2005 ; Shi and Hruban, 2012 ; Garcia-Carracedo et al, 2013 ), and stimulate PI3K-AKT signaling, resulting in uncontrolled cell proliferation, increased cell survival, and accelerated cellular invasion (Keniry and Parsons, 2008 ; Guo et al, 2010 ; Lauring et al, 2010 ; Mancini et al, 2016 ; De Marco et al, 2017 ). It was shown that the E17K mutation not only promotes membrane localization, but that in the absence of serum the mutant cells exhibit enhanced phosphorylation of serine 473 (Ser473) and threonine 308 (Thr308) [a conformational change after AKT-forming plasma membrane targeting that exposes two key amino acids (Vivanco and Sawyers, 2002 ; Landgraf et al, 2008 )], resulting in constitutive activation of Akt1 (Askham et al, 2010 ).…”

“…The AKT1(E17K) mutation promotes migration and invasion of human lung epithelial cells, enhancing their oncogenic and metastatic potential (De Marco et al, 2015 ). The formed tumors are able to spread in mice and colonize the lungs (Do et al, 2010 ; De Marco et al, 2017 ).…”