Mesothelioma is a rare cancer with approximately 3,000 new cases each year. There are three types of mesotheliomas including pleural (75%), pericardial (>1%) and peritoneal (20%). Mesothelioma occurs in the mesothelial cells, which form a protective barrier to multiple organs. Malignant peritoneal mesothelioma (MPM) is initiated in the peritoneum, a serous membrane that lines the inner walls of the abdominal cavity and the outside of the visceral organs and is a very receptive environment for malignancy and metastasis. MPM metastasizes to the abdominal cavity, affecting the omentum, liver, stomach, intestines, and kidneys. MPM is extremely difficult to diagnose due to its vague symptoms, such as abdominal distension, abdominal pain, weight loss, and nausea. Due to difficulty in diagnosis, most patients are diagnosed at an advanced disease (stage III or IV) with a very poor prognosis with a 9% 5-year survival rate. Asbestos exposure is a major risk factor for MPM with symptoms taking 20-50 years post- exposure to appear, making MPM prominent in aged adults. Mesothelin (MSLN), a 40 kDa protein, is normally expressed on the surface of mesothelial cells and manifests at abnormally high levels in several carcinomas including malignant peritoneal mesothelioma. The exact role of mesothelin is not yet fully understood as mesothelin knockout mice do not display an abnormal phenotype. However, there is some evidence to suggest that mesothelin is involved in tumor cell adhesion by binding to the tumor antigen MUC16. Mesothelin wild-type (WT) and knockout (KO) mice were used to investigate the role of host mesothelin expression on MPM metastasis. A MPM cell line was tagged with nuclear red fluorescence protein (RFP) and injected into the abdomen of female C57Bl/6, young (3-6 months) and aged (18-23 months), MSLN WT or KO mice. Disease progression was evaluated post injection of tumor cells by fluorescent in vivo imaging prior to end point dissection. The abdominal cavity was imaged in situ and tumor burden was evaluated using Image J. Overall, aged mice had increased abdominal tumor burden regardless of host MSLN expression. Aged MSLN KO mice displayed an increase in abdominal tumor burden compared to aged MSLN WT mice, however this difference was not significant. Interestingly, the immune profile of the abdominal cavity of tumor naive mice displays a decrease in natural killer (NK) cells and peritoneal macrophages in aged mice suggesting a role in regulating metastatic peritoneal mesothelioma and could possibly be targets for new immunotherapies. This study demonstrates host age increases tumor growth and metastatic success in peritoneal mesothelioma. Citation Format: Mykayla Miller. Aging increases malignant peritoneal mesothelioma metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1329.

Plants synthesize small molecule diterpenes comprised of twenty carbon from precursors isopentenyl diphosphate and dimethylallyl disphosphate, manufacturing diverse compounds used for defense, signaling, and other functions. Industrially, diterpenes are used as natural aromas and flavoring, as pharmaceuticals, and as natural insecticides or repellents. Despite diterpene ubiquity in plant systems, it remains unknown how plants control diterpene localization and transport. For many other small molecules, plant cells maintain transport proteins that control compound compartmentalization. However, for most diterpene compounds, specific transport proteins have not been identified, and so it has been hypothesized that diterpene may cross biological membranes passively. Through molecular simulation, we study membrane transport for three complex diterpenes from among the many made by members of the Lamiaceae family to determine their permeability coefficient across plasma membrane models. To facilitate accurate simulation, the intermolecular interactions for leubethanol, abietic acid, and sclareol were parameterized through the standard CHARMM methodology for incorporation into molecular simulations. To evaluate the effect of membrane composition on permeability, we simulate the three diterpenes in two membrane models derived from sorghum and yeast lipidomics data. We track permeation events within our unbiased simulations, and compare implied permeation coefficients with those calculated from Replica Exchange Umbrella Sampling calculations using the inhomogeneous solubility diffusion model. The diterpenes are observed to permeate freely through these membranes, indicating that a transport protein may not be needed to export these small molecules from plant cells. Moreover, the permeability is observed to be greater for plant-like membrane compositions when compared against animal-like membrane models. Increased permeability for diterpene molecules in plant membranes suggest that plants have tailored their membranes to facilitate low-energy transport processes for signaling molecules.

Plants synthesize small molecule diterpenes composed of 20 carbons from precursor isopentenyl diphosphate and dimethylallyl disphosphate, manufacturing diverse compounds used for defense, signaling, and other functions. Industrially, diterpenes are used as natural aromas and flavoring, as pharmaceuticals, and as natural insecticides or repellents. Despite diterpene ubiquity in plant systems, it remains unknown how plants control diterpene localization and transport. For many other small molecules, plant cells maintain transport proteins that control compound compartmentalization. However, for most diterpene compounds, specific transport proteins have not been identified, and so it has been hypothesized that diterpenes may cross biological membranes passively. Through molecular simulation, we study membrane transport for three complex diterpenes from among the many made by members of the Lamiaceae family to determine their permeability coefficient across plasma membrane models. To facilitate accurate simulation, the intermolecular interactions for leubethanol, abietic acid, and sclareol were parametrized through the standard CHARMM methodology for incorporation into molecular simulations. To evaluate the effect of membrane composition on permeability, we simulate the three diterpenes in two membrane models derived from sorghum and yeast lipidomics data. We track permeation events within our unbiased simulations, and compare implied permeation coefficients with those calculated from Replica Exchange Umbrella Sampling calculations using the inhomogeneous solubility diffusion model. The diterpenes are observed to permeate freely through these membranes, indicating that a transport protein may not be needed to export these small molecules from plant cells. Moreover, the permeability is observed to be greater for plant-like membrane compositions when compared against animal-like membrane models. Increased permeability for diterpene molecules in plant membranes suggest that plants have tailored their membranes to facilitate low-energy transport processes for signaling molecules.

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