Abstract
Although colorectal cancer (CRC) is the third most frequent cause of cancer related death in Europe, clinically relevant biomarkers for therapy guidance and prognosis are insufficiently reliable. Long non-coding RNAs (lncRNAs) are RNAs over 200 nucleotides long that are not translated into proteins but can influence biological processes. There is emerging evidence for their involvement in solid cancer as oncogenes, tumour suppressors or regulators of cell proliferation and metastasis development. The goal of this study was to evaluate the prognostic effect of selected lncRNAs in a retrospective study on CRC patients from the Czech Republic. We used a quantitative PCR approach to measure the expression in paired non-malignant and tumour tissue samples of CRC patients of nine lncRNAs previously shown to be involved in cancer progression—ANRIL, CCAT1, GAS5, linc-ROR, MALAT1, MIR155HG, PCAT1, SPRY4-IT1 and TUG1. Associations between expression and expression ratios and clinical characteristics and survival were assessed by using univariable Cox proportional hazards models, Kaplan-Meier estimations with the Gehan-Wilcoxon test, the Mann-Whitney U test, the Kruskal-Wallis test and Spearman’s correlations. A comparison of expression in tumour tissue (TT) and non-malignant mucosa tissue (MT) showed significant upregulation of CCAT1 and linc-ROR in TT (p < 0.001 and p = 0.001, respectively) and downregulation of ANRIL, MIR155HG and MALAT1 (p = 0.001, p = 0.010, p = 0.001, respectively). Linc-ROR was significantly associated with the presence of synchronous metastases (p = 0.033). For individual tissue types, lower MIR155HG expression in TT was correlated with both shorter overall survival (p = 0.008) and shorter disease-free survival (p = 0.040). In MT, expression ratios of CCAT1/ANRIL and CCAT1/MIR155HG were associated with overall survival (p = 0.005 and p = 0.006, respectively). Our results revealed that changes in expression of lncRNAs between MT and TT hold potential to be used as prognostic biomarkers in CRC patients. Moreover, the ratios of CCAT1 to ANRIL and MIR155HG in MT also exhibit potential for prognosis assessment without tumour sampling. Our results also indicate that cancer progression is associated with detrimental system-wide changes in patient tissue, which might govern patient survival even after successful elimination of tumour or cancerous cells.
Highlights
In 2017, colorectal cancer (CRC) was predicted to be the second and third leading cause of cancer-related death in men and women, respectively, in Europe [1]
We used a quantitative PCR approach to measure the expression in paired non-malignant and tumour tissue samples of CRC patients of nine Long non-coding RNAs (lncRNAs) previously shown to be involved in cancer progression—ANRIL, CCAT1, GAS5, linc-ROR, MALAT1, MIR155HG, PCAT1, SPRY4-IT1 and TUG1
Our results revealed that changes in expression of lncRNAs between mucosa tissue (MT) and tumour tissue (TT) hold potential to be used as prognostic biomarkers in CRC patients
Summary
In 2017, colorectal cancer (CRC) was predicted to be the second and third leading cause of cancer-related death in men and women, respectively, in Europe [1]. Diagnosis has a severe impact on 5 year survival rate, dropping from 90% for localized disease to 12% for patients with distant metastasis [2,3,4] This threat makes it more pressing to discover new biomarkers for all disease stages and potential therapeutic targets in order to better predict disease evolution and understand the epigenetic regulation of gene expression that promotes metastasis. Recent studies have attempted to uncover functionalities of lncRNAs related to their regulation of gene expression, apoptosis, or proliferation as well as their role in the metastatic potential of cancer cells [7,8,9,10,11,12,13].
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