Introduction The incidence of oesophageal adenocarcinoma (OAC) has quadrupled in the last 30 years and outcomes remain poor. We have previously identified TRIM44 as an independent prognostic gene commonly amplified in OAC and breast cancer. However, the exact biology of TRIM44 and its role in epithelial cancers remain unclear

Methods Gene set enrichment analysis (GSEA) was performed on gene expression microarray data of oesophageal (n = 146) and breast cancers (METABRIC, n = 1980) to identify signalling pathways activated by TRIM44 amplification and overexpression. Mass spectrometry was used to identify binding partners of TRIM44 in both endogenous and overexpression settings. Validation of the mass spectrometry results were performed using reciprocal co-immunoprecipitations experiments

Results GSEA performed on OAC samples identified 14 pathway signatures that were significantly enriched with TRIM44 overexpression. To validate these results, GSEA was performed on the METABRIC dataset and this revealed that the PI3K-AKT-mTOR signalling was the only pathway out of the 14 identified signatures to be significantly overenriched in samples with TRIM44 amplification in OAC and breast cancer (p < 0.05). Mass spectrometry of immunoprecipitated TRIM44 identified 2 novel binding partners of TRIM44 -- a ring finger protein associated with activation of c-jun and a tumour metastatic gene shown to directly activate the PI3K-AKT-mTOR signalling pathway. Validation of these two binding partners was successfully performed with endogenous co-immunoprecipitation of TRIM44 in HSC-39, a cell line with high level amplifications of TRIM44; demonstrating that both binding partners associate with TRIM44 in the endogenous setting.

Conclusion Integrative genomic analysis and GSEA provided an insight into the pathways activated by TRIM44. The mTOR pathway was consistently associated with TRIM44 amplification and overexpression. A proteomics approach identified two potential mechanistic explanations how TRIM44 activates the mTOR pathway. Clinically, these findings open up the possibilities of using mTOR inhibitors or peptides disrupting TRIM44 protein interactions to treat TRIM44 amplified tumours.

Disclosure of Interest None Declared.