Cell motility and invasion play an essential role in the development of metastasis. Evidence suggests that the enzyme phospholipase C;1 (PLC;1) may be involved in tumor progression and possibly development of metastasis. In this study, we show that down-regulation of PLC;1 expression severely impairs activation of the small GTP-binding protein Rac and cell invasion in breast cancer cell lines and U87 in vitro. Experimental metastasis assays in nude mice show that inducible knockdown of PLC;1 strongly inhibits development of MDA-MB-231-derived lung metastasis and reverts metastasis formation. In addition, analysis of 60 breast cancer patients' tissues revealed an increase of PLC;1 expression in metastasis compared with the primary tumor in 50% of tissues analyzed. These data show a critical role of PLC;1 in the metastatic potential of cancer cells, and they further indicate that PLC;1 inhibition has a therapeutic potential in the treatment of metastasis dissemination. [Cancer Res 2008;68(24):10187-96]

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Tumour-derived p53 mutants are thought to have acquired ‘gain-of-function’ properties that contribute to oncogenicity. We have tested the hypothesis that p53 mutants suppress p53-target gene expression, leading to enhanced cellular growth. Silencing of mutant p53 expression in several human cell lines was found to lead to the upregulation of wild-type p53-target genes such as p21, gadd45, PERP and PTEN. The expression of these genes was also suppressed in H1299-based isogenic cell lines expressing various hot-spot p53 mutants, and silencing of mutant p53, but not TAp73, abrogated the suppression. Consistently, these hot-spot p53 mutants were able to suppress a variety of p53-target gene promoters. Analysis using the proto-type p21 promoter construct indicated that the p53-binding sites are dispensable for mutant p53-mediated suppression. However, treatment with the histone deacetylase inhibitor trichostatin-A resulted in relief of mutant p53-mediated suppression, suggesting that mutant p53 may induce hypo-acetylation of target gene promoters leading to the suppressive effects. Finally, we show that stable down-regulation of mutant p53 expression resulted in reduced cellular colony growth in human cancer cells, which was found to be due to the induction of apoptosis. Together, the results demonstrate another mechanism through which p53 mutants could promote cellular growth.

BACKGROUND: Owing to its role in cancer, the phosphoinositide 3-kinase (PI3K)/Akt pathway is an attractive target for therapeutic intervention. We previously reported that the inhibition of Akt by inositol 1,3,4,5,6-pentakisphosphate (InsP 5 ) results in anti-tumour properties. To further develop this compound we modified its structure to obtain more potent inhibitors of the PI3K/Akt pathway. METHODS: Cell proliferation/survival was determined by cell counting, sulphorhodamine or acridine orange/ethidium bromide assay; Akt activation was determined by western blot analysis. In vivo effect of compounds was tested on PC3 xenografts, whereas in vitro activity on kinases was determined by SelectScreen Kinase Profiling Service.

The phosphatidylinositol-3-kinase (PI3K)/Akt/mTOR pathway is a major target for cancer therapy. As a strategy to induce the maximal inhibition of this pathway in cancer cells, we combined allosteric mTOR inhibitors (rapamycin and RAD001) with a dual PI3K/mTOR kinase inhibitor (PI-103). Both in vitro and in vivo, the combination exhibited more activity than single agents in human ovarian and prostate cancer cells that harbor alterations in the pathway. At the molecular level, combined inhibition of mTOR prevented the rebound activation of Akt that is seen after treatment with rapamycin and its analogues and caused more sustained inhibition of Akt phosphorylation. Furthermore, the combination strongly inhibited the expression of PI3K/Akt/ mTOR downstream proteins. In particular, it showed greater activity than the single agents in inhibiting the phosphorylation of 4EBP1, both in vitro and in vivo, resulting in selective inhibition of CAP-dependent translation. A proteomic approach was used to confirm the identification of c-Myc as the key regulator for the reduction in downstream proteins affected by the combined inhibition of mTOR. In conclusion, the combination of a catalytic and an allosteric inhibitor of mTOR shows greater activity, without a concomitant increase in toxicity, than either drug alone, and this may have therapeutic implications for inhibiting this pathway in the clinical setting. Cancer Res; 71(13); 4573-84. Ó2011 AACR.

Phisiological activation of PI3K pathway is necessary for cells to regulate many different physiological processes such as transcription, protein synthesis, metabolic responses and membrane trafficking. Abnormal activation of the PI3K pathway leads to an increased activity resulting in tumor onset, maintenance, progression and invasion. Both genetic and epigenetic alterations could affect the normal pathway's activation. Ovarian cancer is the leading cause of death from gynaecological malignancies in the western world. PI3K pathway has been recorded as one of the most deregulated signalling pathway in many tumors, including ovarian ones. So it could be considered an attractive target to be investigated with the various classes of chemical compounds already present or in development. In this rewiew we'll try to discuss the published data of the inhibitors targeting members of the PI3K/ akt/ mTOR pathway in the ovarian cancer setting from a preclinical and clinical point of view, with particular emphasis on drugs combination and strategies of administration. Relevant issues and limitations to the use of particular compounds will be also addressed.

Regulation of the p73 gene is complex due to the presence of two promoters and the very complex mRNA maturation in both the N-terminal and C-terminal parts of the protein. We have found an additional regulation mechanism for the p73-a form that occurs through proteolytic cleavage connected to the activity of the serine protease HtrA2. Following apoptotic stimuli, HtrA2 accumulates in the nucleus and cleaves p73a in the C-terminal portion, enabling the protein to increase its transactivation activity on the apoptotic gene bax but not on the cell-cycle regulator gene p21. In the presence of HtrA2, p73 is more prone to cause caspase activation and nuclei fragmentation: p73 needs HtrA2 to activate and enhance its apoptotic functions. This new relation between p73 and HtrA2 may help to understand the different behavior of the p73 protein in cell physiology and in the responses of cancer cells to chemotherapy.

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