Abstract
BackgroundCap-dependent mRNA translation is essential for the translation of key oncogenic proteins at optimal levels and is highly regulated by the rate limiting, initiation step in protein synthesis. Eukaryotic Translation Initiation Factor 4 Gamma 1 (EIF4G1) serves as a scaffold for assembly of cap-dependent translation components in EIF4F complex formation. In the current study, we analyzed the role and expression of EIF4G1 in Pan human cancer panels through various approaches.MethodsImmunohistochemistry analysis of EIF4G1 protein was done on high-density multi-organ Human Cancer tissue microarray (TMA) derived from the patient samples from different cancers. We used multiple clinical cohorts to analyze the EIF4G1 mRNA expression across human cancers. TCGA data analysis of EIF4G1 was done through Ualcan and c-bioportal web servers. Western blots for EIF4G1 protein was done for different cell lines in representing the multiple cancer types. Dependency score was calculated through Cancer Dependency Map. Clonogenic, tumorosphere assay and cell invasion assay were done with EIF4G complex inhibitor. Association of EIF4G1 mRNA and Kaplan–Meier survival analysis was done on available TCGA datasets.ResultsWe observed an increase in EIF4G1 protein levels in tissue sections from different cancers as compared to their respective normal tissue. Our analysis of the TCGA data revealed that EIF4G1 mRNA expression is significantly increased in tumor tissues compared to respective control tissues across human cancers and variable expression was observed among different datasets. We discovered that alteration frequency in EIF4G1 is prevalent in human cancers e.g. prostate cancer (~ 25%), ovarian cancer (~ 15%), Head and Neck cancer (~ 13%) and cervical cancer (~ 12.5%). EIF4G1 mRNA and protein levels were high across cancer cell lines from multiple organs. Our analysis of DepMap datasets utilizing depletion assays revealed that EIF4G1 is critical for cancer cell survival. Treatment with EIF4G complex inhibitor impaired clonogenic, tumorosphere formation potential and inhibited cell invasion. Moreover, higher EIF4G1 mRNA level was associated with a lower median survival of patients in multiple tumor types.ConclusionsThese studies show that EIF4G1 is amplified/over-expressed in multiple cancers and plays an essential role in cancer cell survival, as such EIF4G1 could serve as a novel potential target for therapeutic intervention across many cancers.
Highlights
Cap-dependent messenger RNAs (mRNA) translation is essential for the translation of key oncogenic proteins at optimal levels and is highly regulated by the rate limiting, initiation step in protein synthesis
Our results showed that mRNA level of Eukaryotic Translation Initiation Factor 4 Gamma 1 (EIF4G1) in primary tumor was universally high compared to normal tissue of bladder (p = 3.09E−07), breast (p = 1.62E−12), cervix (p = 1.27E−2), cholangiocarcinoma (p = 3.67E−08), colon (p = 3.99E−14), esophagus (p = 8.24E−05), glioblastoma (p = 3.80E−03), head and neck (p = 1.62E−12), kidney renal papillary cell (p = 1.35E−04), liver (p = 1.62E−12), lung (p = 1.62E−12), rectum (p = 1.12E−03), stomach (p = 2.43E−12), thyroid (p = 4.01E−04) and endometrial (p < 1E−12) cancer (Fig. 2a–o)
EIF4G complex inhibitor impairs clonogenic activity, 3D tumorosphere formation and inhibits cell invasion We further explored the functional role of EIF4G1 in cancer cells, we did the clonogenic and tumorosphere assays with 4EGI-1, a known inhibitor of the EIF4G-EIF4E complex in two model cell lines viz. Mia PaCa-2 and enzalutamide resistance cell lines derived from C4-2B cells (C42B ENZR)
Summary
Cap-dependent mRNA translation is essential for the translation of key oncogenic proteins at optimal levels and is highly regulated by the rate limiting, initiation step in protein synthesis. Eukaryotic Translation Initiation Factor 4 Gamma 1 (EIF4G1) serves as a scaffold for assembly of cap-dependent translation components in EIF4F complex formation. To meet the criteria for enormous protein synthesis and mRNAs translation of different oncogenes, cancer cells rely on cap-dependent translation. Capdependent translation initiation starts at 5′cap (m7GTP) moiety of eukaryotic initiation factor 4 F (EIF4F) complex which has the cap-binding protein EIF4E, EIF4A (helicase) and EIF4G (scaffolding protein). EIF4G serves as a scaffold for the assembly of the translation initiation complex to initiate translation machinery at the 40S ribosome binding to the mRNA. They recruit 40S ribosome to mRNA by 43S initiation complex formation [6]
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