Transcription initiation arising from E-cadherin/CDH1 intron2: a novel protein isoform that increases gastric cancer cell invasion and angiogenesis†

Abstract

Disruption of E-cadherin (CDH1 gene) expression, subcellular localization or function arises during initiation and progression of almost 90% of all epithelial carcinomas. Nevertheless, the mechanisms through which this occurs are largely unknown. Previous studies showed the importance of CDH1 intron 2 sequences for proper gene and protein expression, supporting these as E-cadherin cis-modulators. Through RACE and RT-PCR, we searched for transcription events arising from CDH1 intron 2 and discovered several new transcripts. One, named CDH1a, with high expression in spleen and absent from normal stomach, was demonstrated to be translated into a novel isoform, differing from canonical E-cadherin in its N-terminal, as determined by mass spectrometry. Quantitative and functional assays showed that when overexpressed in an E-cadherin negative context, CDH1a replaced canonical protein interactions and functions. However, when co-expressed with canonical E-cadherin, CDH1a increased cell invasion and angiogenesis. Further, interferon-induced gene IFITM1 and IFI27 levels were increased upon CDH1a overexpression. Effects on invasion and IFITM1 and IFI27 expression were reverted upon CDH1a-specific knockdown. Importantly, CDH1a was de novo expressed in gastric cancer cell lines. This study presents a new mechanism by which E-cadherin functions are impaired by cis-regulatory mechanisms possibly with the involvement of inflammatory machinery. If confirmed in other cancer models, our data enclose potential for designing targeted therapies to rescue E-cadherin function.

Expression analysis and clinical significance of eIF4E, VEGF-C, E-cadherin and MMP-2 in colorectal adenocarcinoma

“…Contrary to MMP-2, E-cadherin participates in cell adhesions through the E-cadherin-catenin complex. Down-regulation of E-cadherin expression is associated with tumor invasion and results in poor prognosis in many human malignancies including colon cancer [20–25]. Down-regulation of E-cadherin in colorectal adenocarcinoma have been demonstrated to be related to tumor growth and development [24].…”

Digital PCR identifies changes in CDH1 (E-cadherin) transcription pattern in intestinal-type gastric cancer

“…Small regulatory RNAs (micro-RNAs) have also been associated with a decrease of E-cadherin expression in IGC; in particular, the loss of miR-101 results in the up-regulation of EZH2, an inhibitor of E-cadherin, thus reducing its expression and promoting tumor progression [13]. In addition to genetic determinants and miRNAs, an intron-mediated mechanism of CDH1 regulation has also been identified [13, 14, 15]. Indeed, intron 2, harboring an exceptionally high number of repetitive elements involved in exonization, can act as a cis -modulator of E-cadherin gene and protein expression [6, 14, 16].…”

Rescue of wild-type E-cadherin expression from nonsense-mutated cancer cells by a suppressor-tRNA

“…We used the pIRES-EGFP2 backbone carrying either the CDH1 cDNA sequence (WTcDNA) 26 or a CDH1 mini-gene (WTint) in which a minimal intronic sequence from canonical CDH1 intron 15 was introduced (R Bordeira-Carric¸o et al, unpublished). The inclusion of an intronic sequence in this construct generated an artificial CDH1 pre-mRNA that underwent splicing and endogenous quality control ( Figure 1c).…”

“…WTcDNA pIRES-EGFP2 vector, previously designed in our lab, 26 was used to obtain a CDH1 WT mini-gene (WTint), enclosing an intron 15 minimal sequence (291 bp) between CDH1 exons 15 (L34788.1) and 16 (L34789.1).…”