DEAR1, a novel tumor suppressor, negative regulator of epithelial-mesenchymal transition, and prognostic factor in non-small cell lung cancer.

Abstract

10506 Background: DEAR1, also known as TRIM62, maps to 1p.35, a genomic interval within which loss of heterozygosity occurs at high frequency in carcinomas. DEAR1 has been proposed as a regulator of cell polarity in vitro. Methods: We genetically engineered mice lacking DEAR1 alleles at murine chromosome 4. To study the impact of DEAR1 loss in lung cancer, DEAR1 deficient mice were crossed to mice carrying the latent mutant K-rasG12D allele (K-rasLA1). Results: No survival difference was observed between DEAR1+/─ and DEAR1─/─ mice (729 vs 699 days, p=0.98) but they were markedly shorter than that of DEAR1 wild-type littermates (803 days, p=0.01). Over 90% of mice developed tumors, mainly adenocarcinomas, including invasive and/or metastatic lung cancer in 23% of cases. DEAR1-deficient K-rasLA1 mice had reduced life span compared with DEAR1+/+:K-ras+/LA1 littermates (184 vs 291 days, p<0.0001). The survival of DEAR1+/─:K-ras+/LA1 and DEAR1─/─:K-ras+/LA1 mice were similar (180 vs 153 days, p=0.38) and qPCR and IHC analyses suggested loss of the wild-type DEAR1 allele. The survival of DEAR1-deficient K-rasLA1 mice was also shorter than that of control p53+/─:K-ras+/LA1 mice (240 days; p=0.01). The metastasis incompetent K-rasLA1–positive LKR13 cell line after shRNA DEAR1 knock-down and cell lines derived from DEAR1-deficient K-rasLA1 tumors recapitulated an invasive phenotype in transwell migration and 3D culture assays and a metastatic phenotype on SC or IV injection into immunocompetent wild-type littermates. The latter was associated with epithelial-mesenchymal transition involving loss of E-cadherin and DEAR1 expression and upregulation of vimentin, Twist, and CD44. DEAR1 downregulation was very prevalent in a non-small cell lung cancer (NSCLC) tissue array with 214 samples. Patients with early stage NSCLC and loss of DEAR1 expression had a markedly shorter time to relapse compared to those retaining DEAR1 expression (5.1 vs 2.87 years, p=0.049) and worse 5-year relapse-free and overall survival rates. Conclusions: DEAR1 is a novel tumor suppressor that negatively regulates EMT and promotes lung cancer metastasis. DEAR1 loss is a poor prognostic factor in NSCLC.