The phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of the rapamycin (mTOR) signalling pathway is hyperactivated or altered in many cancer types and regulates a broad range of cellular processes including survival, proliferation, growth, metabolism, angiogenesis and metastasis. The PI3K/AKT/mTOR pathway is regulated by a wide-range of upstream signalling proteins and it regulates many downstream effectors by collaborating with various compensatory signalling pathways, primarily with RAF/MEK/ERK pathway. Limited clinical success of the available targeted therapeutic agents and challenges mediated by tumour heterogeneity across different cancer types emphasize the importance of alterations in the PI3K/AKT/mTOR pathway in the design of effective personalized treatment strategies. Here we report a comprehensive PI3K/AKT/mTOR network that represents the intricate crosstalk between compensatory pathways, which can be utilized to study the AKT signalling mechanism in detail and improve the personalized combinatorial therapeutic strategies.

The serine/threonine kinase Akt, a downstream effector of phosphatidylinositol 3-kinase (PI3K), is involved in cell survival and anti-apoptotic signaling. Akt has been shown to be constitutively expressed in a variety of human tumors including hepatocellular carcinoma (HCC). In this report we analyzed the status of Akt pathway in three HCC cell lines, and tested cytotoxic effects of Akt pathway inhibitors LY294002, Wortmannin and Inhibitor VIII. In Mahlavu human hepatoma cells Akt was constitutively activated, as demonstrated by its Ser473 phosphorylation, downstream hyperphosphorylation of BAD on Ser136, and by a specific cell-free kinase assay. In contrast, Huh7 and HepG2 did not show hyperactivation when tested by the same criteria. Akt enzyme hyperactivation in Mahlavu was associated with a loss of PTEN protein expression. Akt signaling was inhibited by the upstream kinase inhibitors, LY294002, Wortmannin, as well as by the specific Akt Inhibitor VIII in all three hepatoma cell lines. Cytotoxicity assays with Akt inhibitors in the same cell lines indicated that they were all sensitive, but with different IC50 values as assayed by RT-CES. We also demonstrated that the cytotoxic effect was through apoptotic cell death. Our findings provide evidence for its constitutive activation in one HCC cell line, and that HCC cell lines, independent of their Akt activation status respond to Akt inhibitors by apoptotic cell death. Thus, Akt inhibition may be considered as an attractive therapeutic intervention in liver cancer.

e Insults to cellular health cause p53 protein accumulation, and loss of p53 function leads to tumorigenesis. Thus, p53 has to be tightly controlled. Here we report that the BTB/POZ domain transcription factor PATZ1 (MAZR), previously known for its transcriptional suppressor functions in T lymphocytes, is a crucial regulator of p53. The novel role of PATZ1 as an inhibitor of the p53 protein marks its gene as a proto-oncogene. PATZ1-deficient cells have reduced proliferative capacity, which we assessed by transcriptome sequencing (RNA-Seq) and real-time cell growth rate analysis. PATZ1 modifies the expression of p53 target genes associated with cell proliferation gene ontology terms. Moreover, PATZ1 regulates several genes involved in cellular adhesion and morphogenesis. Significantly, treatment with the DNA damage-inducing drug doxorubicin results in the loss of the PATZ1 transcription factor as p53 accumulates. We find that PATZ1 binds to p53 and inhibits p53-dependent transcription activation. We examine the mechanism of this functional inhibitory interaction and demonstrate that PATZ1 excludes p53 from DNA binding. This study documents PATZ1 as a novel player in the p53 pathway. Wild-type (WT) p53 is a stress-responsive, sequence-specific transcription factor that inhibits the cell cycle, promotes senescence, and, if the insult to cellular health is not resolved, induces apoptotic death (1). p53 mutations that allow cells to escape this death are the most common genetic event in human cancer (2). Alternative mechanisms of escape rely on the overexpression of MDM2 and MDMX, major negative regulators of p53 that keep p53 levels low under unstressed conditions through ubiquitination-mediated degradation (3). Moreover, many DNA tumor viruses encode proteins that can inactivate p53 (2). However, the list of p53 regulators is far from complete. Various stress conditions result in the upregulation of p53, controlled by feedback loops, posttranslational modifications, and epigenetic changes. In the present study, we aimed to find new players that modify p53 function.p53 is composed of an N-terminal transactivation domain (through which it interacts with MDM2), a proline-rich domain, central DNA binding and tetramerization domains, and a C-terminal regulatory domain. p53 binds response elements (REs) in nuclear DNA, which results in stress-induced changes (either upor downregulation) in gene expression. Tetrameric p53 binds REs that are composed of two half-sites, each with a consensus of RR RCWWGYYY, separated by 0 to 21 bases (where R is a purine, Y is a pyrimidine, and W is either an A or T) (4). p53 REs can be subcategorized as those that respond to low levels of wild-type p53, those that respond to stabilized p53 after stress, and those that respond to p53 with mutations in its DNA binding domain. A recent study found 160 p53 REs controlling 129 genes in the human genome (5). Another study using chromatin immunoprecipitation (ChIP) with paired-end ditag (PET) sequencing identified 542 functional p53 binding sites...

More rapid and accurate high-throughput screening in molecular cellular biology research has become possible with the development of automated microscopy imaging, for which cell nucleus segmentation commonly constitutes the core step. Although several promising methods exist for segmenting the nuclei of monolayer isolated and less-confluent cells, it still remains an open problem to segment the nuclei of more-confluent cells, which tend to grow in overlayers. To address this problem, we propose a new model-based nucleus segmentation algorithm. This algorithm models how a human locates a nucleus by identifying the nucleus boundaries and piecing them together. In this algorithm, we define four types of primitives to represent nucleus boundaries at different orientations and construct an attributed relational graph on the primitives to represent their spatial relations. Then, we reduce the nucleus identification problem to finding predefined structural patterns in the constructed graph and also use the primitives in region growing to delineate the nucleus borders. Working with fluorescence microscopy images, our experiments demonstrate that the proposed algorithm identifies nuclei better than previous nucleus segmentation algorithms.