PO-169 Involvement of neurotensin and neurotrophins pathways in human colorectal cancer cells 5-fluorouracil treatment resistance

Introduction Colorectal cancer (CRC) is one of the leading causes of cancer-related deaths. Surgical resection is the only curative treatment. Depending on disease stage, chemotherapies and targeted therapies are available. Despite considerable progress, recidive cases remain frequent. Studies lead in our laboratory on different cancer models, such as CRC, highlighted the importance of neuropeptides in cancer cells survival and progression: neurotrophines (NT) and neurotensin (NTS). NT is a family of four growth factors, BDNF, NT4/5, NT3 and NGF respectively binding a specific Tropomyosin Receptor Kinase (Trk A, B or C), tyrosin kinase receptors, with a strong affinity. NT can all bind another receptor, p75NTR, with low affinity, as well as the Sortilin, a TRK co-receptor, a NT and NTS intracellular trafficking regulator and also known as Neurotensin Receptor 3 (NTR3). Neurotensin can also bind two other receptors: NTR1 with strong affinity and 2 with low affinity; both are G protein coupled receptors. Very few is known about NT and NTS pathways in CRC cells resistance to chemotherapies, 5-Fluorouracil (5FU) being the backbone of any chemotreatments. The aim of my project is to understand if and how these pathways could be involved in 5FU CRC cell resistance and survival. Material and methods Two human CRC cell lines from different disease stages (WiDr, SW620) were treated with 8 µM of 5FU to obtain stably 5FU resistant cell lines. Both cell lines were also xenografted in Nude mice which were treated with 5FU. Protein expressions were assessed by western blot. Cell activation was assessed by flow cytometry. Stable knockdown cell lines (NTR3) were obtained by shRNA transfection. Exosomes were purified from culture supernatants by ultracentrifugation. Results and discussions Preliminary results show that NTSR3 protein expression is increased after 5FU treatment both in whole cell lysates and exosomes especially in the most agressive cell line (SW620). The same results were obtained in vitro and in vivo . Moreover, 5FU treatment induces a decrease of tumour size only for the least agressive line (WiDr). Indeed, the 5FU induces a quiescence state of these cells. Conclusion It is the first time that, in CRC, the NTSR3 seems to be overexpressed in 5FU-resistant tumour cells (from primary and advanced stages), in vitro and in vivo . This receptor could constitute a new potential therapeutic target.