Inhibition of Akt signaling in hepatoma cells induces apoptotic cell death independent of Akt activation status (original) (raw)

Active form of AKT controls cell proliferation and response to apoptosis in hepatocellular carcinoma

Oncology Reports, 2013

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related mortality worldwide. Deregulation of the AKT signaling pathway has been found in HCC. However, the effect of AKT activation on the proliferation and apoptosis in HCC is not clear. Herein, expression of phosphorylated form of AKT (Ser 473) was investigated in HCC tumor (n=73), cirrhosis (n=17), normal liver (n=22) samples and in HCC cell lines (n=8). The results showed that expression of p-AKT was higher in tumor (53%) than in cirrhotic tissues (12%) while it was absent in normal liver (p<0.0001). p-AKT expression was also associated with number of tumor nodules and differentiation status (p<0.05). LY294002 induced cell cycle arrest at G0/G1 in SNU-449 and Mahlavu cells by decreasing expression of CDK2, CDK4, CycD1, CycD3, CycE, CycA and increasing expression of p21 and p27 as well; it also caused a decrease in the E2F1 transcriptional activity through declining phosphorylated Rb. LY294002 did not affect the basal level of apoptosis; however, it amplified cisplatin-induced apoptosis in SNU-449 cells. When the p-AKT level was decreased specifically after transfection with the DN-AKT plasmid, SNU-449 cells became more sensitive to cisplatin-induced apoptosis. HuH-7 cells with no basal p-AKT, were markedly affected by the treatment of doxorubicin. Thus, Akt signaling controls growth and chemical-induced apoptosis in HCC and p-AKT may be a potential target for therapeutic interventions in HCC patients.

The AKT inhibitor MK-2206 is cytotoxic in hepatocarcinoma cells displaying hyperphosphorylated AKT-1 and synergizes with conventional chemotherapy

Oncotarget, 2013

Hepatocellular carcinoma (HCC) is one of the most common potentially lethal human malignancies worldwide. Advanced or recurrent HCC is frequently resistant to conventional chemotherapeutic agents and radiation. Therefore, targeted agents with tolerable toxicity are mandatory to improve HCC therapy and prognosis. In this neoplasia, the PI3K/Akt signaling network has been frequently shown to be aberrantly up-regulated. To evaluate whether Akt could represent a target for treatment of HCC, we studied the effects of the allosteric Akt inhibitor, MK-2206, on a panel of HCC cell lines characterized by different levels of Akt-1 activation. The inhibitor decreased cell viability and induced cell cycle arrest in the G0/G1 phase of the cell cycle, with a higher efficacy in cells with hyperphosphorylated Akt-1. Moreover, MK-2206 induced apoptosis, as documented by Annexin V labeling, and also caused autophagy, as evidenced by increased levels of the autophagy marker LC3A/B. Autophagy was shown...

A kinase-independent function of AKT promotes cancer cell survival

35 induced cell death in a PH-domain dependent manner. An AKT kinase domain mutant 36 found in human melanoma (G161V) lacked enzymatic activity in-vitro and in AKT1/AKT2 37 double knockout cells, but promoted growth-factor independent survival of primary 38 human melanocytes. ATP-competitive AKT inhibitors failed to block the kinase-39 independent function of AKT, a liability that limits their effectiveness compared to 40 allosteric AKT inhibitors. Our results broaden the current view of AKT function and have 41 important implications for the development of AKT inhibitors for cancer. 42 43 44 45 46 47 48 49 50 51 52 53 3

Targeting Akt in Hepatocellular Carcinoma and Its Tumor Microenvironment

International Journal of Molecular Sciences

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related deaths worldwide, and its incidence is rising. HCC develops almost exclusively on the background of chronic liver inflammation, which can be caused by chronic alcohol consumption, viral hepatitis, or an unhealthy diet. The key role of chronic inflammation in the process of hepatocarcinogenesis, including in the deregulation of innate and adaptive immune responses, has been demonstrated. The inhibition of Akt (also known as Protein Kinase B) directly affects cancer cells, but this therapeutic strategy also exhibits indirect anti-tumor activity mediated by the modulation of the tumor microenvironment, as demonstrated by using Akt inhibitors AZD5363, MK-2206, or ARQ 092. Moreover, the isoforms of Akt converge and diverge in their designated roles, but the currently available Akt inhibitors fail to display an isoform specificity. Thus, selective Akt inhibition needs to be better explored in the context of ...

Tumor cell sensitization to apoptotic stimuli by selective inhibition of specific Akt/PKB family members

Molecular Cancer Therapeutics, 2005

Recent studies indicate that dysregulation of the Akt/PKB family of serine/threonine kinases is a prominent feature of many human cancers. The Akt/PKB family is composed of three members termed Akt1/PKBa, Akt2/PKBh, and Akt3/ PKBg. It is currently not known to what extent there is functional overlap between these family members. We have recently identified small molecule inhibitors of Akt. These compounds have pleckstrin homology domaindependent, isozyme-specific activity. In this report, we present data showing the relative contribution that inhibition of the different isozymes has on the apoptotic response of tumor cells to a variety of chemotherapies. In multiple cell backgrounds, maximal induction of caspase-3 activity is achieved when both Akt1 and Akt2 are inhibited. This induction is not reversed by overexpression of functionally active Akt3. The level of caspase-3 activation achieved under these conditions is equivalent to that observed with the phosphatidylinositol-3-kinase inhibitor LY294002. We also show that in different tumor cell backgrounds inhibition of mammalian target of rapamycin, a downstream substrate of Akt, is less effective in inducing caspase-3 activity than inhibition of Akt1 and Akt2. This shows that the survival phenotype conferred by Akt can be mediated by signaling pathways independent of mammalian target of rapamycin in some tumor cell backgrounds. Finally, we show that inhibition of both Akt1 and Akt2 selectively sensitizes tumor cells, but not normal cells, to apoptotic stimuli. [Mol Cancer Ther 2005;4(2):271 -9] Received

The potential role of Akt phosphorylation in human cancers.

Akt/protein kinase B (PKB) is a serine/threonine kinase which is implicated in mediating a variety of biological responses including cell growth, proliferation and survival. Akt is activated by phosphorylation on two critical residues, namely threonine 308 (Thr308) and serine 473 (Ser473). Several studies have found Akt2 to be amplified or overexpressed at the mRNA level in various tumor cell lines and in a number of human malignancies such as colon, pancreatic and breast cancers. Nevertheless, activation of Akt isoforms by phosphorylation appears to be more clinically significant than Akt2 amplification or overexpression. Many studies in the past 4-5 years have revealed a prognostic and/or predictive role of Akt phosphorylation in breast, prostate and non-small cell lung cancer. Several publications suggest a role of phosphorylated Akt also in endometrial, pancreatic, gastric, tongue and renal cancer. However, different types of assays were used in these studies. Before assessment of P-Akt can be incorporated into routine clinical practice, all aspects of the assay methodology will have to be standardized.

Pleiotropic Effects of PI‐3′ Kinase/Akt Signaling in Human Hepatoma Cell Proliferation and Drug‐Induced Apoptosis

Annals of the New York Academy of Sciences, 2006

IGF-II and type I-IGF receptor (IGF-IR) gene expression is increased in primary liver tumors, and transgenic mice overexpressing IGF-II in the liver develop hepatocellular carcinoma (HCC) spontaneously, suggesting that alterations of IGF-IR signaling in vivo may play a role in the auto/paracrine control of hepatocarcinogenesis. We have addressed the contribution of PI-3 K/Akt signaling on the proliferation of HepG 2 human hepatoma cells and on their protection against doxorubicin-induced apoptosis. Both basal HepG 2 cell DNA replication and that stimulated by IGF-IR signaling were inhibited by the specific PI-3 K inhibitor Ly294002 (Ly). In the former case, PI-3 K signaling overcame cell cycle arrest in G 1 via increased cyclin D 1 protein and decreased p27 kip1 gene expression. Doxorubicin treatment induced apoptosis in HepG 2 cells and was concomitant with the proteolytic cleavage of Akt-1 and-2. Drug-induced apoptosis was reversed by IGF-I and this effect was (i) dependent on Akt-1 and-2 phosphorylation and (ii) accompanied by the inhibition of initiator caspase-9 activity, suggesting that IGF-IR signaling interferes with mitochondria-dependent apoptosis. Accordingly, Ly enhanced doxorubicin-induced apoptosis and suppressed its reversal by IGF-I. Altogether, the data emphasize the crucial role of PI-3 K/Akt signaling (i) in basal as well as IGF-IR-stimulated HepG 2 cell proliferation and (ii) in controlling both doxorubicin-induced apoptosis

Cytotoxic activity of the novel small molecule AKT inhibitor SC66 in hepatocellular carcinoma cells

Oncotarget, 2015

Hepatocellular carcinoma (HCC) is characterized by limited response to current drug therapies. Here, we report that SC66, a novel AKT inhibitor, reduced cell viability in a dose- and time-dependent manner, inhibited colony formation and induced apoptosis in HCC cells. SC66 treatment led to a reduction in total and phospho-AKT levels. This was associated with alterations in cytoskeleton organization, a reduction in expression levels of E-cadherin, β-catenin and phospho-FAK, together with up-regulation of Snail protein levels. All these alterations were coupled with anoikis cell death induction. In addition, SC66 induced the production of reactive oxygen species (ROS) and DNA damage. Pre-treatment with the ROS scavenger N-Acetyl-cysteine (NAC) prevented SC66-induced cell growth inhibition and anoikis. SC66 significantly potentiated the effects of both conventional chemotherapeutic and targeted agents, doxorubicin and everolimus, respectively. In vivo, SC66 inhibited tumor growth of He...

Akt is transferred to the nucleus of cells treated with apoptin, and it participates in apoptin-induced cell death

Cell Proliferation, 2007

Objectives : The phosphatidylinositol 3-kinase (PI3-K)/Akt pathway is well known for the regulation of cell survival, proliferation, and some metabolic routes. Meterials and Methods : In this study, we document a novel role for the PI3-K/Akt pathway during cell death induced by apoptin, a tumour-selective inducer of apoptosis. Results : We show for the first time that apoptin interacts with the p85 regulatory subunit, leading to constitutive activation of PI3-K. The inhibition of PI3-K activation either by chemical inhibitors or by genetic approaches severely impairs cell death induced by apoptin. Downstream of PI3-K, Akt is activated and translocated to the nucleus together with apoptin. Direct interaction between apoptin and Akt is documented. Co-expression of nuclear Akt significantly potentiates cell death induced by apoptin. Thus, apoptin-facilitated nuclear Akt, in contrast to when in its cytoplasmic pool, appears to be a positive regulator, rather than repressor of apoptosis. Conclusions : Our observations indicate that PI3-K/Akt pathways have a dual role in both survival and cell death processes depending on the stimulus. Nuclear Akt acts as apoptosis stimulator rather than as a repressor, as it likely gains access to a new set of substrates in the nucleus. The implicated link between survival and cell death pathways during apoptosis opens new pharmacological opportunities to modulate apoptosis in cancer, for example through the manipulation of Akt's cellular localization.