Tracking the evolution of therapy resistance in colorectal cancer.

• Applicant: Soulafa Mamlouk, Ph.D.
• Subject Area: Gastroenterology ; Hematology, Oncology
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 446321395

Resistance to cancer therapies is one of the main reasons patients do not survive their disease. Essentially, cancer treatments (whether cytotoxic, targeted or immunotherapy) are capable of destroying a tumor cell. Their job is to hinder DNA repair mechanisms, inhibit a molecular pathway, or shake up the immune system to attack and eliminate diseased cells. The reason these treatments often fail is due to the escape routes, which tumor cells find to become resistant to the therapeutic assault. When we understand the evolutionary development of cancer we begin to appreciate the large amount of escape mechanisms which can be utilized by a tumor made of trillions of cells multiplying at high rates. In addition, we begin to appreciate the danger of maximum dose treatment schemes, where all but the most resistant tumor cells are eliminated leaving the oncologist with limited options and a highly dangerous growth.In this project we will investigate the evolution of resistance in colorectal cancer cells while they are adapting to therapy, specifically chemotherapy. To accomplish this we will first identify the molecular pathways which dominate the sub-clonal trajectories that develop under therapy resistance. These pathways will be studied at DNA, RNA and methylation levels using 3D patient derived organoid cultures from CRC patients and modern technologies including single cell sequencing of fluorescent labelled barcodes. Secondly, we will characterize the fitness-cost of pre-existing resistance in the tumor compared to resistance which needs to evolve de-novo while under therapy. To achieve this we will utilize CRISPR/Cas9 gene editing to insert or repair alterations which confer resistance in cell lines. Thirdly, we will investigate whether tumor cells will always follow the same resistance mechanism if placed under the same therapy and identical environmental pressures. In all instances of this project, cells will be sampled continuously resulting in a biobank of frozen samples from progression to resistance, allowing us to access any stage along the resistance spectrum for validation of our results.This project aims to inhibit the development of resistance to chemotherapy. The main problem facing cancer treatment is not its incapability of attacking tumor cells, but its failure to inhibit their escape mechanism while they evolve resistance. Therefore, understanding the molecular background of such evolutionary escape processes in cancer we can stay one step ahead of the development of complete resistance to cancer treatment.

• DFG Programme: Research Grants