mRNA profiling of the cancer degradome in oesophago-gastric adenocarcinoma

Abstract

Background: Degradation of the extracellular matrix is fundamental to tumour development, invasion and metastasis. Several protease families have been implicated in the development of a broad range of tumour types, including oesophago-gastric (OG) adenocarcinoma. The aim of this study was to analyse the expression levels of all core members of the cancer degradome in OG adenocarcinoma and to investigate the relationship between expression levels and tumour/patient variables associated with poor prognosis.

Methods: Comprehensive expression profiling of the protease families (matrix metalloproteinases (MMPs), members of the ADAM metalloproteinase-disintegrin family (ADAMs)), their inhibitors (tissue inhibitors of metalloproteinase), and molecules involved in the c-Met signalling pathway, was performed using quantitative real-time reverse transcription polymerase chain reaction in a cohort of matched malignant and benign peri-tumoural OG tissue (n=25 patients). Data were analysed with respect to clinico-pathological variables (tumour stage and grade, age, sex and pre-operative plasma C-reactive protein level).

Results: Gene expression of MMP1, 3, 7, 9, 10, 11, 12, 16 and 24 was upregulated by factors >4-fold in OG adenocarcinoma samples compared with matched benign tissue (P<0.01). Expression of ADAM8 and ADAM15 correlated significantly with tumour stage (P=0.048 and P=0.044), and ADAM12 expression correlated with tumour grade (P=0.011).

Conclusion: This study represents the first comprehensive quantitative analysis of the expression of proteases and their inhibitors in human OG adenocarcinoma. These findings implicate elevated ADAM8, 12 and 15 mRNA expression as potential prognostic molecular markers.

Figure 1

Box-and-whisker plots of the gene expression (relative to 18S rRNA) of the most highly expressed degradome components in malignant compared with benign OG tissue (P<0.01). Y-axes show relative mRNA expression compared with 18S rRNA expression (y-axes limited for visual clarity). Each of these degradome components was expressed in malignant tissue at levels >4-fold that are seen in benign tissue (range 3.65–20.18). Data were compared using Wilcoxon signed-rank test.●=Outlier (value >1.5 times the interquartile range beyond the quartiles).

Figure 2

Relationship between relative gene expression and tumour stage and grade. (A) ADAM8 expression associated positively with tumour stage (P=0.048). (B) ADAM15 expression associated positively with tumour stage (P=0.044). (C) ADAM12 expression associated positively with worsening tumour grade (P=0.011). Horizontal bars show median values. Comparisons were performed using Kruskal–Wallis test. Extreme values are not shown for visual clarity.