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Blumen, Steven R.

Cell and Molecular Biology Program

2006

Ph. D.

Malignant pleural mesothelioma is a devastating disease that currently has no cure. The median survival time for patients is less than one year following diagnosis. Therapeutic treatments for mesothelioma include surgery, radiation therapy, and chemotherapy, and no current treatment has shown significant impact on patient survival times. Many chemotherapeutic drugs have been tried alone and in combinations to try to find an effective treatment, thus far without success. We reason that some of the problems with current chemotherapeutics include poor delivery to target cells, and ineffective uptake of the drugs by the cancer cells. Additionally, virtually all chemotherapeutics are characterized by adverse side effects and systemic toxicity. Here, we present a novel approach to treat mesothelioma that uses silica based mesoporous spheres as vehicles to carry compounds, specifically the widely used chemotherapeutic drug doxorubicin (DOX), in the treatment of mesothelioma. Acid prepared mesoporous silica spheres (APMS) have been developed and patented at UVM (Dr. Landry, Department of Chemistry) for use in medical and therapeutic applications. APMS were coated with tetraethylene glycol (TEG) externally and studied in vitro and after administration intrapleurally or intranasally to mice. In vitro studies showed that APMS, which were nontoxic alone to cells, increased the potency of killing by DOX when compared to identical concentrations of DOX added directly to culture medium. In in vivo studies, APMS alone, when administered 1X intrapleurally or intranasally were nontoxic, as determined by histopathology and differential cell counts or release of protein or lactate dehydrogenase (LDH) in bronchoalveolar lavage fluid or pleural lavage fluid at 1, 3 and 7 days post injection.
APMS were taken up by epithelial cells and macrophages in lung tissue and mesothelial cells of the rib and diaphragm. We also investigated the kinetics and possible mechanism of uptake by cells of the APMS using confocal scanning laser microscopy (CSLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). By loading APMS with a plasmid encoding red fluorescent protein or with DOX, we also investigated plasmid release from APMS in vitro and in vivo, and determined the effect of treating mesothelioma cells with APMS preloaded with DOX (APMS-DOX) on signaling pathways [nuclear factor-[kappa]B (NF-[kappa]B); extracellular signal regulated kinases (ERK1/2, ERK5); and phosphatidylinositol-3 kinase (PI3-W/AKT)] that are associated with apoptosis, proliferation and survival. In these experiments, NF-[kappa]B binding to DNA was inhibited in human mesothelioma (MM) cells. We also investigated whether the level of phosphorylation of histone protein H2AX ([gamma]H2AX), a marker of DNA double strand breaks, was altered and whether apoptosis inducing factor (ATF) was affected. After exposure to either APMS-DOX (80 nM) or 80 nM DOX alone, MM cells exhibited increased levels of [gamma]H2AX, which was not seen in cells exposed to APMS alone, but no changes in nuclear localization of AIF were detected. Our studies illustrate the biological potential of APMS as a novel mechanism for treatment of asbestos-induced mesotheliomas and lung cancers.