PO-170 Dissecting the role of IFITM1 in response to anticancer treatment

IntroductionConstitutive expression of interferons (IFNs) and their downstream signalling pathways play a critical role in host responses to cell transformation in the tumour microenvironment. Induction of IFNs initiates the transcription of a variety of genes, so called IFN- stimulated genes (ISGs). Although expression of ISGs is classically associated with tumour suppression, a subset defined as the IRDS (Interferon - Related DNA- Damage Resistance Signature), is elevated in response to endogenous IFN, self-DNA and RNA exposure in the tumour microenvironment acquiring radiation and chemotherapy resistance. INF induced transmembrane receptor (IFITM1) is thought to participate in proliferating signalling and oncogenesis. Three out of five IFITM genes (IFITM1,2,3) share high amino-acid homology, however, IFITM1 has a unique C-terminal domain, a 13 amino-acid extension, and a shorter N-terminal amino-acid sequence.Material and methodsTo analyse the impact of IFITM1 loss, or mutation, on signalling and phenotypic events such as growth, viability and drug resistance, knock – out, knock – in and domain mutants were generated using Crispr/Cas9 mediated gene – editing. To identify the effects of radiation in the growth of wild type and mutant IFITM1 cells, proliferation assays were conducted while immunoassays were used to check for activation of the IRDS pathway. The gene edited cell lines were used in Mass Spectrometry proteomic approaches to discover IFITM1 interacting proteins under normal growth conditions as well as in INF treated and/or radiated cells.Results and discussionsIrradiation of glioma stem cells, results in a substantial increase in the expression of IFITM1 and an activation of the IRDS pathway which suggests a potential mechanism by which cancer stem cells escape chemotherapy. Deletion of IFITM1 in SiHa cells results in sensitivity to chemo- and radiation therapy, while loss of both IFITM1 and IFITM3 function generates chemoresistant cancer cells suggesting a potential interaction between IFITM1 and IFITM3.Structure-function analysis has shown that the C-terminal regulatory domain of IFITM1 is required for its ability to promote cell growth and to localise to the membrane.ConclusionWe have identified IFITM1 as an upstream regulator of the IRDS which promotes cancer cell survival and mediates chemoresistance. The C-terminal domain of IFITM1 is important for its proliferative activity in cancer and lay the foundation for future research aiming to