Poster abstracts
Poster number 20 submitted by Safiya Khurshid
Metabolic starvation in tumors regulates Alternative Splicing to potentiate tumorigenicity
SAFIYA KHURSHID (Nationwide Childrens Hospital/ Ohio State University), Claudia Kelly (Nationwide Childrens Hospital/ Ohio State University), Ruoning Wang (Nationwide Childrens Hospital/ Ohio State University), Dawn Chandler (Nationwide Childrens Hospital/ Ohio State University)
Abstract:
Malignant cells especially cells inside the tumor core, subsist in a unique microenvironment, which is hypoxic and metabolically starved. Overwhelming data indicates that tumor cells have developed exclusive mechanisms to overcome this hostile microenvironment and potentiate tumorigenesis. My data suggests that tumor cells respond to metabolic stress by modulating their alternative splicing (AS), resulting in a dynamic overexpression of oncogenic isoforms.
Insulin receptor undergoes AS to produce two isoforms: the full-length IR-B and exon-11 skipped IR-A isoform. While IR-B has high affinity for insulin, IR-A binds both insulin and IGF2 with high affinity and as such exploits the IGF pathway to accelerate the onset of tumor-cell hallmarks like proliferation, migration & angiogenesis. Our data suggests that hypoxic stress as well as treating cells with Glucose (G) & Glutamine (Q) starved media, changes the AS of IR to express more IR-A. This phenotype is exclusively demonstrated by cancer cells whereas normal cells succumb to this hostile microenvironment, suggesting that tumor cells actively adapt to reinforce survival. Our hypothesis is that metabolic stress alters the expression of splicing factors, leading to the generation of oncogenic isoforms such as IR-A, which contributes to cancer progression. Phospho-proteomic analysis of cells treated with GQ starvation enlists ‘insulin-receptor-signaling-pathway’ and ‘spliceosomal-pathway’ to be among the top 6 altered pathways. Additionally, the phosphorylation levels of multiple SR proteins are changed on metabolic starvation. Towards that end, we analyzed the expression of SR protein kinases SRPK1 & 2 and found that expression of both kinases decreased in cells treated with metabolic starvation. Direct-RNA nanopore sequencing revealed Eef2 and the RNA helicase DDX5 to be significantly altered in GQ starved vs control conditions.
The existing data delineates an unexplored role of AS in metabolic starvation. We have established Splice Switching Oligonucleotides (SSOs) that reverse the splicing change of IR & reinstate the normal growth of cells, undermining tumorigenesis and providing a new therapeutic alternative.
Keywords: Cancer, Metabolic starvation, Alternative splicing