Oncological Sciences and Dermatology

This work presents evidence on the association of active DDC molecules with membranes in mammalian brain. L-DOPA decarboxylase (DDC) is generally considered to be a cytosolic enzyme. Membrane-associated DDC was detected by immunoblotting and enzymatic assay experiments. DDC activity and immunoreactivity could be partially extracted from mammalian brain membranes by detergent. Fractionation of membranes by temperature-induced phase separation in Triton X-114, resulted in the recovery of membrane-associated DDC in separation phases where integral and hydrophobic membrane proteins separate. Treatment of membranes with phosphatidylinositol-specific phospholipase C or proteinase K, did not elute membrane-associated DDC activity, suggesting that a population of DDC molecules exist embedded within membranes. The elucidation of the functional significance of the enzyme's association with membranes could provide us with new information leading to the better understanding of the biological pathways that DDC is involved in.

Purpose: mTOR (mammalian target of rapamycin) plays a central role in regulating cell growth and cell cycle progression and is regarded as a promising therapeutic target. We examined whether mTOR inhibition by RAD001 (everolimus) is therapeutically efficacious in the treatment of ovarian cancer as a single agent and in combination with cisplatin. Experimental Design: Using four human ovarian cancer cell lines, we determined the effect of RAD001 by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Western blot, and apoptosis assays. We evaluated the association between phospho-AKT/mTOR activity and RAD001sensitivity. We also determined the effect of RAD001on tumor growth and malignancy using mice inoculated with human ovarian cancer cells.

Tumors with mutant BRAF and some with mutant RAS are dependent upon ERK signaling for proliferation, and their growth is suppressed by MAPK/ERK kinase (MEK) inhibitors. In contrast, tumor cells with human EGF receptor (HER) kinase activation proliferate in a MEK-independent manner. These findings have led to the development of RAF and MEK inhibitors as anticancer agents. Like MEK inhibitors, the RAF inhibitor PLX4032 inhibits the proliferation of BRAF V600E tumor cells but not that of HER kinase-dependent tumors. However, tumors with RAS mutation that are sensitive to MEK inhibition are insensitive to PLX4032. MEK inhibitors inhibit ERK phosphorylation in all normal and tumor cells, whereas PLX4032 inhibits ERK signaling only in tumor cells expressing BRAF V600E . In contrast, the drug activates MEK and ERK phosphorylation in cells with wildtype BRAF. In BRAF V600E tumor cells, MEK and RAF inhibitors affect the expression of a common set of genes. PLX4032 inhibits ERK signaling output in mutant BRAF cells, whereas it transiently activates the expression of these genes in tumor cells with wild-type RAF. Thus, PLX4032 inhibits ERK signaling output in a mutant BRAFselective manner. These data explain why the drug selectively inhibits the growth of mutant BRAF tumors and suggest that it will not cause toxicity resulting from the inhibition of ERK signaling in normal cells. This selectivity may lead to a broader therapeutic index and help explain the greater antitumor activity observed with this drug than with MEK inhibitors.

The neurofibromatosis type 2 NF2 gene product, merlin, is a tumor suppressor frequently inactivated in malignant mesothelioma (MM). To investigate a possible correlation between merlin inactivation and MM invasiveness, we restored merlin expression in NF2-deficient MM cells. Re-expression of merlin markedly inhibited cell motility, spreading and invasiveness, properties connected with the malignant phenotype of MM cells. To test directly whether merlin inactivation promotes invasion in a nonmalignant system, we used small interfering RNA to silence Nf2 in mouse embryonic fibroblasts (MEFs) and found that downregulation of merlin resulted in enhanced cell spreading and invasion. To delineate signaling events connected with this phenotype, we investigated the effect of merlin expression on focal adhesion kinase (FAK), a key component of cellular pathways affecting migration and invasion. Expression of merlin attenuated FAK phosphorylation at the critical phosphorylation site Tyr397 and disrupted the interaction of FAK with its binding partners Src and p85, the regulatory subunit of phosphatidylinositol-3-kinase. In addition, NF2-null MM cells stably overexpressing FAK showed increased invasiveness, which decreased significantly when merlin expression was restored. Collectively, these findings suggest that merlin inactivation is a critical step in MM pathogenesis and is related, at least in part, with upregulation of FAK activity.

Activation of AKT and overexpression of fatty acid synthase (FAS) are frequently observed in human ovarian cancer. To explore a possible connection between AKT and FAS, immunohistochemical analyses were conducted on an ovarian cancer tissue microarray, which revealed a significant correlation between phosphorylated AKT (phospho-AKT) and expression of FAS. To investigate the relationship between phospho-AKT and FAS in vitro, a variety of experiments employing a specific phosphatidylinositol 3-OH kinase (PI3K) inhibitor (LY294002), inducible PTEN expression in PTEN-null cells, or AKT1 siRNA demonstrated that phosphatidylinositol-3 kinase (PI3K)/AKT signaling modulates FAS expression. In contrast, inhibition of FAS activity by the drug C75 resulted in downregulation of phospho-AKT and increased cell death. To explore the functional relationship between phospho-AKT and FAS, we used SKOV3, C200, and OVCAR10 ovarian carcinoma cells, which have constitutively active AKT, and OVCAR5 cells, which have very low basal phospho-AKT levels. Treatment with LY294002 abolished AKT activity and potentiated apoptosis induced by FAS inhibitors cerulenin or C75 only in cells with constitutively active AKT, suggesting that constitutive activation of AKT protects against FAS inhibitor-induced cell death. Furthermore, inhibition of FAS activity by cerulenin or C75 resulted in downregulation of phospho-AKT, which preceded the induction of apoptosis. To investigate the relationship between phospho-AKT and FAS in vivo, severe combined immunodeficient mice injected intraperitoneally with SKOV3 cells were treated with C75. Growth of SKOV3 xenografts was markedly inhibited by C75. Analysis of the levels of phospho-AKT and FAS in C75-treated tumors revealed concordant downregulation of phospho-AKT and FAS. Collectively, our findings are consistent with a working model in which AKT activation regulates FAS expression, at least in part, whereas FAS activity modulates AKT activation.

Tumors with mutant BRAF are dependent on the RAF/MEK/ERK signaling pathway for their growth1 -3. We found that ATP-competitive RAF inhibitors inhibit ERK signaling in cells with mutant BRAF, but unexpectedly enhance signaling in cells with wild-type BRAF.

Activated RAS promotes dimerization of members of the RAF kinase family 1-3 . ATP-competitive RAF inhibitors activate ERK signaling 4-7 by transactivating RAF dimers 4 . In melanomas with mutant BRAF(V600E), levels of RAS activation are low and these drugs bind to BRAF(V600E) monomers and inhibit their activity. This tumor-specific inhibition of ERK signaling results in a

To test second-line personalized medicine combination therapies, based on genomic and proteomic data, in patient-derived xenograft (PDX) models. We established 12 PDX from BRAF inhibitor progressed melanoma patients. Following expansion, PDX were analyzed using targeted sequencing and reverse phase protein arrays (RPPA). By using multi-arm pre-clinical trial designs, we identified efficacious precision medicine approaches. We identified alterations previously described as drivers of resistance: NRAS mutations in 3 PDX, MAP2K1 (MEK1) mutations in 2, BRAF amplification in 4, and aberrant PTEN in 7. At the protein level, re-activation of phospho MAPK predominated, with parallel activation of PI3K in a subset. Second line efficacy of the pan-PI3K inhibitor BKM120 with either BRAF (encorafenib) /MEK (binimetinib) inhibitor combination or the ERK inhibitor VX-11e was confirmed in vivo. Amplification of MET was observed in 3 PDX models, a higher frequency than expected and a possible novel...