During development and in the context of different morphogenetic events, epithelial cells undergo a process called epithelial to mesenchymal transition or transdifferentiation (EMT). In this process, the cells lose their epithelial characteristics, including their polarity and specialized cell-cell contacts, and acquire a migratory behavior, allowing them to move away from their epithelial cell community and to integrate into surrounding tissue, even at remote locations. EMT illustrates the differentiation plasticity during development and is complemented by another process, called mesenchymal to epithelial transition (MET). While being an integral process during development, EMT is also recapitulated under pathological conditions, prominently in fibrosis and in invasion and metastasis of carcinomas. Accordingly, EMT is considered as an important step in tumor progression. TGF-β signaling has been shown to play an important role in EMT. In fact, adding TGF-β to epithelial cells in culture is a convenient way to induce EMT in various epithelial cells. Although much less characterized, epithelial plasticity can also be regulated by TGF-β-related bone morphogenetic proteins (BMPs), and BMPs have been shown to induce EMT or MET depending on the developmental context. In this review, we will discuss the induction of EMT in response to TGF-β, and focus on the underlying signaling and transcription mechanisms.

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TGF-beta-induced epithelial to mesenchymal transition.

Phosphoinositide 3-kinases (PI3Ks) function early in intracellular signal transduction pathways and affect many biological functions. A further level of complexity derives from the existence of eight PI3K isoforms, which are divided into class I, class II and class III PI3Ks. PI3K signalling has been implicated in metabolic control, immunity, angiogenesis and cardiovascular homeostasis, and is one of the most frequently deregulated pathways in cancer. PI3K inhibitors have recently entered clinical trials in oncology. A better understanding of how the different PI3K isoforms are regulated and control signalling could uncover their roles in pathology and reveal in which disease contexts their blockade could be most beneficial.

The emerging mechanisms of isoform-specific PI3K signalling

The phosphatidylinositol 3-kinase (PI3K) signaling axis impacts on cancer cell growth, survival, motility, and metabolism. This pathway is activated by several different mechanisms in cancers, including somatic mutation and amplification of genes encoding key components. In addition, PI3K signaling may serve integral functions for noncancerous cells in the tumor microenvironment. Consequently, therapeutics targeting the PI3K pathway are being developed at a rapid pace, and preclinical and early clinical studies are beginning to suggest specific strategies to effectively use them. However, the central role of PI3K signaling in a large array of diverse biologic processes raises concerns about its use in therapeutics and increases the need to develop sophisticated strategies for its use. In this review, we will discuss how PI3K signaling affects the growth and survival of tumor cells. From this vantage, we will consider how inhibitors of the PI3K signaling cascade, either alone or in combination with other therapeutics, can most effectively be used for the treatment of cancer.

The PI3K Pathway As Drug Target in Human Cancer

Treatment decisions for patients with lung cancer have historically been based on tumour histology. Some understanding of the molecular composition of tumours has led to the development of targeted agents, for which initial findings are promising. Clearer understanding of mutations in relevant genes and their effects on cancer cell proliferation and survival, is, therefore, of substantial interest. We review current knowledge about molecular subsets in non-small-cell lung cancer that have been identified as potentially having clinical relevance to targeted therapies. Since mutations in EGFR and KRAS have been extensively reviewed elsewhere, here, we discuss subsets defined by so-called driver mutations in ALK, HER2 (also known as ERBB2), BRAF, PIK3CA, AKT1, MAP2K1, and MET. The adoption of treatment tailored according to the genetic make-up of individual tumours would involve a paradigm shift, but might lead to substantial therapeutic improvements.

https://www.thelancet.com/pdfs/journals/lanonc/PIIS1470-2045(10)70087-5.pdf

New driver mutations in non-small-cell lung cancer

In a screen for gene copy-number changes in mouse mammary tumors, we identified a tumor with a small 350-kb amplicon from a region that is syntenic to a much larger locus amplified in human cancers at chromosome 11q22. The mouse amplicon contains only one known gene, Yap, encoding the mammalian ortholog of Drosophila Yorkie (Yki), a downstream effector of the Hippo(Hpo)-Salvador(Sav)-Warts(Wts) signaling cascade, recently identified in flies as a critical regulator of cellular proliferation and apoptosis. In nontransformed mammary epithelial cells, overexpression of human YAP induces epithelial-to-mesenchymal transition, suppression of apoptosis, growth factor-independent proliferation, and anchorage-independent growth in soft agar. Together, these observations point to a potential oncogenic role for YAP in 11q22-amplified human cancers, and they suggest that this highly conserved signaling pathway identified in Drosophila regulates both cellular proliferation and apoptosis in mammalian epithelial cells.

https://www.pnas.org/content/pnas/103/33/12405.full.pdf

Transforming properties of YAP, a candidate oncogene on the chromosome 11q22 amplicon

Mutations in the PIK3CA gene, which encodes the p110α catalytic subunit of phosphatidylinositol 3-kinase (PI3K), have been reported in human cancers, including colorectal cancer. Most of the mutations cluster at hotspots within the helical and kinase domains. Whereas H1047R, one of the hotspot mutants, is reported to have elevated lipid kinase activity, the functional consequences of other mutations have not been examined. In this study, we examined the effects of colon cancer–associated PIK3CA mutations on the lipid kinase activity in vitro, activation of the downstream targets Akt and p70S6K in vivo and NIH 3T3-transforming ability. Of eight mutations examined, all showed increased lipid kinase activity compared with wild-type p110α. All the mutants strongly activated Akt and p70S6K compared with wild-type p110α as determined by immunoblotting using phospho-specific antibodies. These mutants also induced morphologic changes, loss of contact inhibition, and anchorage-independent growth of NIH 3T3 cells. The hotspot mutations examined in this study, E542K, E545K, and H1047R, all had high enzymatic and transforming activities. These results show that almost all the colon cancer–associated PIK3CA mutations are functionally active so that they are likely to be involved in carcinogenesis.

https://cancerres.aacrjournals.org/content/canres/65/11/4562.full.pdf

Functional analysis of PIK3CA gene mutations in human colorectal cancer.

The interaction between the chemokine receptor CXCR4 and its specific ligand, stromal cell–derived factor-1 (SDF-1/CXCL12), mediates several cellular functions. In cancer, SDF-1-positive or CXCR4-positive cells of various lineages are detected within tumor tissues. Recent intensive research has indicated the possibility that blocking CXCR4 could reduce the metastatic potential of cancer cells. Here, we show that the inhibition of the SDF-1/CXCR4 axis decreases the growth of s.c. gastrointestinal tumors through the suppression of tumor neoangiogenesis. The neutralization of CXCR4 suppressed the growth in vivo of tumors derived from mouse Colon38 and PancO2 cells, whereas it did not affect the growth of Colon38 and PancO2 cells in vitro . This attenuation of tumor growth was found to be independent of the expression of CXCR4 by the cancer cells themselves, because CXCR4 knocked-down Colon38 cells grew similarly to control cells. Furthermore, CD31-positive tumor capillaries were reduced to 45% ( P P

https://cancerres.aacrjournals.org/content/canres/65/13/5864.full.pdf

Blockade of the Stromal Cell–Derived Factor-1/CXCR4 Axis Attenuates In vivo Tumor Growth by Inhibiting Angiogenesis in a Vascular Endothelial Growth Factor–Independent Manner

https://www.gastrojournal.org/article/S0016-5085(05)02538-2/pdf

Hepatitis C Virus Core Protein Is a Potent Inhibitor of RNA Silencing-Based Antiviral Response

Hepatitis B virus X protein (HBx) has many cellular functions and is a major factor in hepatitis and hepatocellular carcinoma caused by HBV infection. A proteomic approach was used to search for HBx-interacting proteins in order to elucidate the molecular mechanism of hepatocarcinogenesis. HBx was attached to myc and flag tags (MEF tags) and expressed in 293T cells; the protein complex formed within the cells was purified and characterized by mass spectrometry. COP9 signalosome (CSN) subunits 3 and 4 were subsequently identified as HBx-interacting proteins. In addition, CSN subunit 5, Jun activation domain-binding protein 1 (Jab1), was shown to be a novel cellular target of HBx. In vivo and in vitro interactions between HBx and Jab1 were confirmed by standard immunoprecipitation and GST pull-down assays. An analysis of HBx deletion constructs showed that amino acids 30-125 of HBx were responsible for binding to Jab1. Confocal laser microscopy demonstrated that HBx was mainly localized in the cytoplasm, while Jab1 was found mainly in the nucleus and partially in the cytoplasm, and that the two proteins colocalized in the cytoplasm. The cotransfection of HBx and Jab1 resulted in substantial activator protein 1 (AP-1) activation and knockdown of endogenous Jab1 attenuated AP-1 activation caused by HBx. In addition, the coexpression of HBx and Jab1 potentiated phosphorylation of JNK, leading to the subsequent phosphorylation of c-Jun, whereas the level of c-Jun and JNK phosphorylation induced by HBx was decreased in Jab1 knockdown cells. These results suggest that the interaction between HBx and Jab1 enhances HBx-mediated AP-1 activation.

The hepatitis B virus X protein enhances AP-1 activation through interaction with Jab1.

HMGA1 proteins are architectural transcription factors that are overexpressed in a range of human malignancies, including pancreatic adenocarcinoma We hypothesized that HMGA1 expression is a determinant of cellular invasiveness and metastasis in pancreatic cancer Stable silencing of HMGA1 in MiaPaCa2 and PANC1 pancreatic adenocarcinoma cells was achieved by transfection of short hairpin RNA-generating vectors Additionally, stable overexpression of HMGA1 in MiaPaCa2 cells (characterized by low levels of inherent HMGA1 expression) was achieved HMGA1 silencing resulted in significant reductions in cellular invasiveness through Matrigel; in cellular matrix metalloproteinase-9 (MMP-9) activity, mRNA levels, and gene promoter activity; and in Akt phosphorylation at Ser(473) Conversely, forced HMGA1 overexpression resulted in significant increases in cellular invasiveness; in cellular MMP-9 activity, mRNA levels, and promoter activity; and in Akt phosphorylation at Ser(473) HMGA1 overexpression-induced increases in invasiveness were MMP-9 dependent The role of phosphatidylinositol-3 kinase (PI3K)/Akt in mediating HMGA1-dependent invasiveness was elucidated by a specific PI3K inhibitor (LY294002) and constitutively active and dominant-negative Akt adenoviral constructs Akt-dependent modulation of MMP-9 activity contributed significantly to HMGA1 overexpression-induced increases in invasive capacity Furthermore, HMGA1 silencing resulted in reductions in metastatic potential and tumor growth in vivo and in tumoral MMP-9 activity Our findings suggest that HMGA1 may be a novel molecular determinant of invasiveness and metastasis, as well as a potential therapeutic target, in pancreatic adenocarcinoma

https://cancerres.aacrjournals.org/content/canres/66/24/11613.full.pdf

Amarsanaa Jazag

Papers

Functional analysis of PIK3CA gene mutations in human colorectal cancer.

Blockade of the Stromal Cell–Derived Factor-1/CXCR4 Axis Attenuates In vivo Tumor Growth by Inhibiting Angiogenesis in a Vascular Endothelial Growth Factor–Independent Manner

Hepatitis C Virus Core Protein Is a Potent Inhibitor of RNA Silencing-Based Antiviral Response

The hepatitis B virus X protein enhances AP-1 activation through interaction with Jab1.

HMGA1 Is a Determinant of Cellular Invasiveness and In vivo Metastatic Potential in Pancreatic Adenocarcinoma