Expression of XPG protein in human normal and tumor tissues.

XPG (Xeroderma pigmentosum group G complementing factor) is a protein associated with DNA repair and transcription. Point mutations in ERCC5, the gene coding for XPG, cause the cancer-prone disorder xeroderma pigmentosum (XP) while truncation mutations give rise to individuals with the combined clinical features of XP and Cockayne syndrome. Polymorphisms of ERCC5 or alterations in XPG mRNA expression were also associated to an increase risk of different cancers types and to prognosis of cancer patients.

Molecular pharmacology and antitumor activity of Zalypsis in several human cancer cell lines.

Zalypsis is a new synthetic alkaloid tetrahydroisoquinoline antibiotic that has a reactive carbinolamine group. This functionality can lead to the formation of a covalent bond with the amino group of selected guanines in the DNA double helix, both in the absence and in the presence of methylated cytosines. The resulting complex is additionally stabilized by the establishment of one or more hydrogen bonds with adjacent nucleotides in the opposite strand as well as by van der Waals interactions within the minor groove.

Activation of phosphatidylinositol 3-kinase by membrane localization of p110alpha predisposes mammary glands to neoplastic transformation.

Phosphatidylinositol 3-kinases (PI3K) constitute important regulators of various signaling pathways with relevance in cancer. Enhanced activation of p110alpha, the catalytic subunit of PI3K, was found in a high proportion of many human tumor types. We generated a mouse model in which PI3K is activated by forced recruitment of p110alpha to the membrane.

Characterization of the p53 response to oncogene-induced senescence.

Background: P53 activation can trigger various outcomes, among them reversible growth arrest or cellular senescence. It is a live debate whether these outcomes are influenced by quantitative or qualitative mechanisms. Furthermore, the relative contribution of p53 to Ras-induced senescence is also matter of controversy.

Loss-of-function genetic screening identifies a cluster of ribosomal proteins regulating p53 function.

Introduction of conditional murine p53 (p53val135) and oncogenic ras into double p53/p21-null mouse embryonic fibroblasts (MEFs) showed that p21waf1 was not required for combined ras/p53-induced senescent-like growth arrest. We used this cellular system to identify key players in the ras-p53-induced senescence in the absence of p21. Applying a retroviral-based genetic screen, we obtained mRNA antisense fragments against a cluster of 14 different ribosomal proteins which loss of function bypasses p53-induced growth arrest.

The PTEN/PI3K/AKT signalling pathway in cancer, therapeutic implications.

PTEN/PI3K/AKT constitutes an important pathway regulating the signaling of multiple biological processes such as apoptosis, metabolism, cell proliferation and cell growth. PTEN is a dual protein/lipid phosphatase which main substrate is the phosphatidyl-inositol,3,4,5 triphosphate (PIP3), the product of PI3K. Increase in PIP3 recruits AKT to the membrane where it is activated by other kinases also dependent on PIP3.

PPP1CA contributes to the senescence program induced by oncogenic Ras.

Ectopic expression of conditional murine p53 (p53val135) and oncogenic ras is enough to induce a senescent-like growth arrest at the restrictive temperature. We took advantage of this cellular system to identify new key players in the ras/p53-induced senescence. Applying a retroviral-based genetic screen, we obtained an antisense RNA fragment against PPP1CA, the catalytic subunit of protein phosphatase 1alpha, whose loss of function bypasses ras/p53-induced growth arrest and senescence.

MAP17 inhibits Myc-induced apoptosis through PI3K/AKT pathway activation.

MAP17 is a non-glycosylated membrane-associated protein that has been shown to be over-expressed in human carcinomas, suggesting a possible role of this protein in tumorigenesis. However, very little is known about the molecular mechanism mediating the possible tumor promoting properties of MAP17. To analyze the effect of MAP17 on cell survival, we used Rat1 fibroblasts model where Myc over-expression promotes apoptosis in low serum conditions.

MAP17 enhances the malignant behavior of tumor cells through ROS increase.

Tumorigenesis occurs when the mechanisms involved in the control of tissue homeostasis are disrupted and cells stop responding to physiological signals. Therefore, genes capable of desensitizing tumoral cells from physiological signals may provide a selective advantage within the tumoral mass and influence the outcome of the disease. We undertook a large-scale genetic screen to identify genes able to alter the cellular response to physiological signals and provide selective advantage once tumorigenesis has begun.

Levels of p27(kip1) determine Aplidin sensitivity.

Aplidin (plitidepsin) is a novel anticancer drug isolated from the marine tunicate Aplidium albicans. Aplidin shows potent antitumor activity in preclinical models against a wide variety of human tumors. Aplidin is currently in phase II clinical trials in a variety of solid tumors and hematologic malignancies.

MAP17 overexpression is a common characteristic of carcinomas.

We undertook a large-scale genetic screen to identify genes able to alter the cellular response to physiological signals and provide selective advantage once tumorigenesis has begun. We identified MAP17, a small 17 kDa non-glycosylated membrane protein previously identified, being overexpressed in carcinomas. We found that MAP17 is overexpressed in a great variety of human carcinomas.

Mst1, RanBP2 and eIF4G are new markers for in vivo PI3K activation in murine and human prostate.

Phosphatidylinositol 3-kinases (PI3Ks) constitute important regulators of signaling pathways. The PIK3CA gene encoding the p110-alpha catalytic subunit represents one of the highly mutated oncogenes identified in human cancer. Here, we report new markers for in vivo PI3K activation in prostate.

PTEN, more than the AKT pathway.

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN)/phosphatidylinositol 3-kinase (PI3K)/AKT constitute an important pathway regulating the signaling of multiple biological processes such as apoptosis, metabolism, cell proliferation and cell growth. PTEN is a dual protein/lipid phosphatase and its main substrate phosphatidyl-inositol 3,4,5 triphosphate (PIP3) is the product of PI3K. Increase in PIP3 recruits AKT to the membrane where is activated by other kinases also dependent on PIP3.

Mice expressing myrAKT1 in the mammary gland develop carcinogen-induced ER-positive mammary tumors that mimic human breast cancer.

AKT1/PKB is a serine/threonine protein kinase that regulates biological processes such as proliferation, apoptosis and growth in a variety of cell types. To assess the oncogenic capability of an activated form of AKT in vivo we have generated several transgenic mouse lines that overexpress in the mammary epithelium the murine Akt1 gene modified with a myristoylation signal, which renders active this protein by localizing it to the plasma membrane. We demonstrate that expression of myristoylated AKT in the mammary glands increases the susceptibility of these mice to the induction of mammary tumors of epithelial origin by the carcinogen 9,10-dimethyl-1,2 benzanthracene (DMBA).

Extreme sensitivity to Yondelis (Trabectedin, ET-743) in low passaged sarcoma cell lines correlates with mutated p53.

Yondelis (Trabectedin, ET-743) is a marine anticancer agent currently in Phase II/III development in patients with advanced pretreated soft tissue sarcoma. In the present study, we generated a panel of low passaged tumor cell lines from samples explanted from chemonaive sarcoma patients with different tumor types. We assessed in vitro sensitivity/resistance to Trabectedin and doxorubicin in a panel of sarcoma cell lines and examined the correlation between molecular alterations in DNA repair genes and sensitivity to Trabectedin.

Inhibition of phosphatidylinositol-3-kinase synergizes with gemcitabine in low-passage tumor cell lines correlating with Bax translocation to the mitochondria.

Apoptotic pathways, including the phosphatidylinositol-3-kinase (PI3K)/AKT survival pathway, are altered in most cancer cells in relation to their normal counterparts and these differences may present an excellent therapeutic window. To gain insight into the relevance of the PI3K pathway as a target for drug discovery we generated tumor cell lines from different tumor samples that we maintained at low passage. The characterization of these cell lines indicates that all of them have constitutively activated the PI3K pathway through different mechanisms.

Regulation of p53: intricate loops and delicate balances.

The p53 tumor suppressor protein provides a major anti-cancer defense mechanism, as underscored by the fact that the p53 gene is the most frequent target for genetic alterations in human cancer. Recent work has led to the realization that p53 lies at the hub of a very complex network of signaling pathways, which integrate a variety of intracellular and extracellular inputs. Part of this network consists of an array of autoregulatory feedback loops, where p53 exhibits very intricate interactions with other proteins known to play important roles in the determination of cell fate.

Cross-talk between Akt, p53 and Mdm2: possible implications for the regulation of apoptosis.

The p53 tumor suppressor protein and the Akt/PKB kinase play important roles in the transduction of pro-apoptotic and anti-apoptotic signals, respectively. We provide evidence that conflicting signals transduced by Akt and p53 are integrated via negative feedback between the two pathways. On the one hand, the combination of ionizing radiation and survival factor deprivation, which leads to rapid apoptosis of IL-3 dependent DA-1 cells, entails a caspase- and p53-dependent destruction of Akt.