Characterising a role for EDI3 in metastasis in vivo

• Applicant: Professor Dr. Jan G. Hengstler
• Subject Area: Public Health, Healthcare Research, Social and Occupational Medicine
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 279671858

Recently, we identified the glycerophosphodiesterase, Endometrial cancer Differential 3 (EDI3; GPCPD1) as part of a larger study with the goal to characterise markers of endometrial cancer metastasis. We observed that primary tumours that went on to metastasize expressed approximately six times higher EDI3 than the non-metastasizing tumours. In addition, EDI3 was associated with worse prognosis. These observations were also confirmed in a cohort of ovarian cancer patients, suggesting that EDI3 is a promising marker of metastasis. Our initial work also characterised EDI3 as a glycerophosphodiesterase, which hydrolyses its substrate glycerophosphocholine (GPC) to choline and glycerol-3-phosphate. Interest in choline metabolism has recently increased due to several reports showing that choline metabolites, in particular phosphocholine, are elevated in particularly aggressive cancer types. Furthermore, choline is needed for the production of phosphatidylcholine, the most abundant phospholipid in the membrane of cells, and precursor to several signalling lipids. Glycerol-3-phosphate, the second EDI3 product, is further metabolised to signalling lipids phosphatidic acid (PA), and lysophosphatidic acid (LPA). It can also be converted to glyceraldehyde-3-phosphate, an early metabolite in glycolysis, which too is altered in cancer. Knocking down EDI3 with siRNA in several cancer cells reversed phosphocholine levels to that found in non-transformed cells, and altered many key lipid metabolites, including PA and LPA. Further characterisation of EDI3 identified a critical role in cellular migration, a step necessary for metastasis. Interestingly, two other processes - cell adhesion and spreading - which occur during metastatic dissemination and are dependent on signalling mechanisms similar to those involved in migration, are also influenced by EDI3. However, all of the results described on EDI3 so far were performed using in vitro cell culture models, which allowed us to study the basic functions of EDI3, but lacked the complexity of the in vivo microenvironment and the multitude of cell types present. Therefore, the current proposal will use an established model of breast cancer to study the influence of EDI3 on metastasis in vivo. An orthotopic model of breast cancer will be developed in mice with tumour cells expressing either high or low levels of EDI3. Both the primary tumour and resulting metastases in different tissues will be analysed for EDI3 expression, markers of proliferation and migration, behaviour of the tumour cells within the tumour and the microenvironment, and choline metabolism. The overall goal is that we gain a better understanding of the role of EDI3 in the metastasis process, and ultimately its suitability as a metastatic marker and therapeutic target.

• DFG Programme: Research Grants
• Co-Investigator: Rosemarie Marchan, Ph.D.