MET mutations in cancers of unknown primary origin (CUPs).

Cancer of unknown primary origin (CUP) defines metastatic disease of unknown origin, accounting for 3-5% of all cancers. Growing evidence demonstrates that inappropriate execution of a genetic program named "invasive growth," driven by the MET oncogene, is implicated in the metastatic process. MET activation in cancers is mainly consequent to overexpression, whereas mutations are rarely found. We reasoned that the occurrence of MET somatic mutations might sustain premature occult dissemination of cancer cells, such as that observed in CUPs. We sequenced MET in genomic DNA obtained from 47 early metastatic cancers. By extensive immunohistochemical analysis a primary site was afterward postulated in 24 patients, whereas 23 cases remained of unknown primary (CUPs). MET somatic mutations were found in seven cases, all belonging to the CUP cohort. Mutational incidence (30%) was thus significantly higher than the expected one (4%), in the absence of high mutational background. Several nucleotide changes were novel and clustered either in the kinase domain or in the extracellular semaphorin domain. Mutated receptors were functional and sustained the transformed phenotype, suggesting that MET activating mutations are genetic markers associated with the CUP syndrome.

Hepatocyte growth factor sensitizes human ovarian carcinoma cell lines to paclitaxel and cisplatin.

The hepatocyte growth factor (HGF) receptor, encoded by the MET oncogene, is expressed in approximately 70% of human ovarian carcinomas and overexpressed in 30% of cases. Because HGF is known to protect cells from apoptosis, we investigated whether receptor expression modifies ovarian cancer cell response to chemotherapy. The apoptotic effect of the front-line chemotherapeutic drugs paclitaxel and cisplatin on cells treated with HGF was studied. In ovarian cancer cell lines, pretreatment with HGF surprisingly enhances the apoptotic response to low doses of paclitaxel and cisplatin. HGF empowers specifically the intrinsic apoptotic pathway, whereas it protects cells from extrinsic Fas-induced apoptosis. Chemotherapy sensitization is specific for HGF because another growth factor (e.g., epidermal growth factor) increases ovarian cancer cell survival. In nonovarian cancer cell models, as expected, HGF provides protection from drug-induced apoptosis. These data show that HGF sensitizes ovarian carcinoma cells to low-dose chemotherapeutic agents. This suggests that HGF may be used to improve response to chemotherapy in a set of human ovarian carcinomas molecularly classified based on the MET oncogene expression.

High speed DSC (hyper-DSC) as a tool to measure the solubility of a drug within a solid or semi-solid matrix.

Conventional differential scanning calorimetry (DSC) techniques are commonly used to quantify the solubility of drugs within polymeric-controlled delivery systems. However, the nature of the DSC experiment, and in particular the relatively slow heating rates employed, limit its use to the measurement of drug solubility at the drug's melting temperature. Here, we describe the application of hyper-DSC (HDSC), a variant of DSC involving extremely rapid heating rates, to the calculation of the solubility of a model drug, metronidazole, in silicone elastomer, and demonstrate that the faster heating rates permit the solubility to be calculated under non-equilibrium conditions such that the solubility better approximates that at the temperature of use. At a heating rate of 400 degrees C/min (HDSC), metronidazole solubility was calculated to be 2.16 mg/g compared with 6.16 mg/g at 20 degrees C/min.

Cell surface-associated Tat modulates HIV-1 infection and spreading through a specific interaction with gp120 viral envelope protein.

Human immunodeficiency virus-1 (HIV-1) Tat, a nuclear transactivator of viral gene expression, has the unusual property of being released by infected cells. Recent studies suggest that extracellular Tat is partially sequestered by heparan sulfate proteoglycans. As a consequence, Tat is concentrated on the cell surface and protected from proteolytic degradation, thus remaining in a biologically active form. We show that Tat binds the surfaces of both HIV-1-infected and surrounding uninfected cells. We provide evidence for a specific interaction between Tat and the HIV-1 glycoprotein 120 (gp120) envelope protein, which enhances virus attachment and entry into cells. We map the interacting sites of both Tat and gp120 and show that synthetic peptides mimicking the gp120 site inhibit HIV-1 infection. Our data demonstrate that membrane-associated Tat is a novel modulator of virus entry and suggest that the Tat-gp120 interaction represents a critical step in HIV-1 spreading during the course of infection.