Research Overview

My working group focusses on three key aspects of extracellular vesicles (EV) summarized in the graphical abstract and explained below:

1. Identification, purification and characterization of cancer-specific EV carrying the majority of dsDNA with clinical biomarker and functional utility.
2. Mechanism(s) of EV dsDNA transfer into the recipient cells.
3. Functional consequence of EV dsDNA transfer into recipient cells on metastatic cancer progression.

Identification and purification of cancer specific EV carrying the majority of dsDNA with clinical biomarker and functional utility
In this project, we aim to dissect the heterogeneity of EVs derived from the mixture of healthy and cancerous cells in the blood plasma of cancer patients in order to obtain EVs with high biomarker potential and functional relevance. We believe that EV surface marker immune capturing-based techniques to enrich DNA-containing EV-subpopulations will further increase the sensitivity of mutational analysis. Using pediatric AML model in collaboration with (Prof. Dr. Bernd Giebel, Transfusion Medicine, UK Essen) we have now established bead based capturing method to isolate and analyze homogenous EV population. Characterization of homogenous leukemia EVs revealed enrichment of leukemia specific mutations in homogenous EV captured by bead capturing. In the next step, we are analyzing a large cohort of pediatric AML and healthy plasma samples for establishing EV DNA based biomarker for minimum residual disease primary responsible for relapse in pediatric patients.

Mechanism of EV dsDNA transfer into the recipient cells
Besides establishing the diagnostic potential of dsDNA in cancer EVs, our lab aims to investigate the mechanism by which tumor EV dsDNA (EV-DNA) is untaken by the healthy recipient cells in the pre-metastatic niche. Key topics related to the study are (i) to understand the molecular pathways explored by the cancer EVs to introduce the DNA inside the recipient cells and (ii) the communication of EV-DNA with the intracellular organelle inside the recipient cells. Detailed functional characterization of the molecular machinery involved in the EV-DNA uptake by distant recipient cells and the interaction of EV-DNA with the cytoplasmic and nuclear components of these recipient cells in the tumor microenvironment will improve our understanding on the biology of cancer metastasis.

Functional consequence of EV dsDNA transfer in recipient cells on metastatic cancer progression
Our data indicating the uptake of EV-DNA by the recipient cells motivates us to explore the function of EV-DNA in pre-metastatic niche immuno-modulation. Our working hypothesis is that EV-DNA modulates immune cell response and can influence the distant metastatic cells towards pro-inflammation. Indeed, our preliminary data suggest the activation of the cytosolic DNA-sensing pathway cGAS/STING (cyclic GMP-AMP synthase—stimulator of interferon genes), resulting in cell cycle arrest or apoptosis in lung fibroblast cells when educated with breast cancer-derived EV-DNA. We believe that increased EV-DNA production by cancer cells and its uptake by immune cells, like dendritic cells in circulation, lead to activation of cGAS/STING signaling. These activated dendritic cells when recruited to the cells in the pre-metastatic niche can induce the whole circuit of inflammatory pathways potentially responsible for the recruitment of tumor cells to the distant organ in the process of metastasis.
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