Investigation of subcellular trafficking of prostate specific membrane antigen (PSMA) and development of optimised aptamer therapeutics targeting PSMA.

• Applicant: Dr. Sven Kruspe
• Subject Area: Biochemistry
• Term: from 2015 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 280017680

Prostate specific membrane antigen (PSMA) is a prominent cell surface marker of prostate cancer cells. Its expression rate is strongly correlated to the severity code of the tumor, in particular to its metastatic behaviour. However the molecular mechanisms behind this correlation remain almost totally unclear. Two properties of PSMA are suspected to account for increased tumor growth and tumor cell migration. (1) Its enzymatic activity of a carboxypeptidase and (2) its internalisation into the tumor cell. Both features are addressed by targeting PSMA with the RNA aptamer A9g, which inhibits PSMA activity and is taken up into the cell bound to PSMA. Recently, the hosting laboratory found that A9g also exhibits an anti-metastatic effect on human prostate cancer cells in an in vivo xenograft model in mice.The present project focusses on the subcellular trafficking of PSMA and the RNA aptamer A9g. The insights derived from this study will shed light on the intracellular actions of PSMA and are intended to unravel the contradictory observations reported for PSMAs subcellular pathway. The applicant will examine the hypothesis, that internalised PSMA is in part transferred into the cytoplasm and proteolysed to yield the non-membrane form PSM', which is predominantly found in normal prostate cells. The majority of the intended methods has formerly been established by the applicant or by the hosting laboratory. These include flow cytometry, RT-qPCR, confocal fluorescence microscopy and pulldown-assays.The deduced information about the intracellular traffic will also be used for the development of optimised A9g based therapeutics. Herein combinatorial secondary (and tertiary) drug loads (e.g. chemotherapeutics) will be conjugated to A9g with the choice of drug being in respect to their site of action within the cell. As a result a trimodal therapeutic is intended by combining (1) A9g's anti-metastatic ability with (2) siRNAs against crucial tumor genes and (3) the aforementioned site-specific drug load.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professorin Paloma Giangrande, Ph.D.