Differential expression of angiogenesis-related genes 'VEGF' and 'angiopoietin-1' in metastatic and EMAST-positive colorectal cancer patients.

Abnormal angiogenesis leads to tumor progression and metastasis in colorectal cancer (CRC). This study aimed to elucidate the association between angiogenesis-related genes, including VEGF-A, ANGPT-1, and ANGPT-2 with both metastatic and microsatellite alterations at selected tetranucleotide repeats (EMAST) subtypes of CRC. We conducted a thorough assessment of the ANGPT-1, ANGPT-2, and VEGF-A gene expression utilizing publicly available RNA sequencing and microarray datasets. Then, the experimental validation was performed in 122 CRC patients, considering their disease metastasis and EMAST+/- profile by using reverse transcription polymerase chain reaction (RT-PCR). Subsequently, a competing endogenous RNA (ceRNA) network associated with these angiogenesis-related genes was constructed and analyzed. The expression level of VEGF-A and ANGPT-2 genes were significantly higher in tumor tissues as compared with normal adjacent tissues (P-value < 0.001). Nevertheless, ANGPT-1 had a significantly lower expression in tumor samples than in normal colon tissue (P-value < 0.01). We identified a significantly increased VEGF-A (P-value = 0.002) and decreased ANGPT-1 (P-value = 0.04) expression in EMAST+ colorectal tumors. Regarding metastasis, a significantly increased VEGF-A and ANGPT-2 expression (P-value = 0.001) and decreased ANGPT-1 expression (P-value < 0.05) were established in metastatic CRC patients. Remarkably, co-expression analysis also showed a strong correlation between ANGPT-2 and VEGF-A gene expressions. The ceRNA network was constructed by ANGPT-1, ANGPT-2, VEGF-A, and experimentally validated miRNAs (hsa-miR-190a-3p, hsa-miR-374c-5p, hsa-miR-452-5p, and hsa-miR-889-3p), lncRNAs (AFAP1-AS1, KCNQ1OT1 and MALAT1), and TFs (Sp1, E2F1, and STAT3). Network analysis revealed that colorectal cancer is amongst the 82 significant pathways. We demonstrated a significant differential expression of VEGF-A and ANGPT-1 in colorectal cancer patients exhibiting the EMAST+ phenotype. This finding provides novel insights into the molecular pathogenesis of colorectal cancer, specifically in EMAST subtypes. Yet, the generalization of in silico findings to EMAST+ colorectal cancer warrants future experimental investigations. In the end, this study proposes that the EMAST biomarker could serve as an additional perspective on CMS4 biology which is well-defined by activated angiogenesis and worse overall survival.

High expression of ZEB1 is associated with EMAST & metastasis in colorectal cancer patients.

Background & objectives: Transforming growth factor-beta (TGF-ß) signalling pathway has been reported to be involved in metastasis and at the same time has been considered compellingly an important mediator of epithelial-to-mesenchymal transition (EMT). Besides, EMT process is maintained by zinc-finger E-box-binding homeobox 1 (ZEB1) gene which is induced by TGF-ß pathway. TGF-ß has been shown to be associated with elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) phenomenon, which is one of the prognostic biomarkers of colorectal cancer (CRC). This study was conducted to determine the link among ZEB1-induced TGF-ß, EMAST status and metastasis. Methods: The expression level of ZEB1 was evaluated using quantitative reverse transcription (qRT) real-time PCR in 122 formalin fixed paraffin-embedded tissues of CRC sample with known EMAST status and TGF-ß/Smad-dependent pathways. The association among ZEB1 expression, TGF-ß signalling pathway, EMAST status and metastatic behaviour was examined. Results: ZEB1 gene expression level was higher in tumour tissues as compared to normal samples (P<0.045). In addition, ZEB1 positive expression level was associated significantly with metastasis (P=0.05), EMAST+ status (P=0.052) and activated TGF-ß signalling pathway (P=0.002). Interpretation & conclusions: Our results validated significant association between activated TGF-ß signalling pathway and EMAST+ phenotype with higher expression of ZEB1 and higher level of metastasis.

High expression of Snail1 is associated with EMAST and poor prognosis in CRC patients.

AIM: This study aimed to determine the link between Snail1 expression and CRC patients' survival as well as its significant association with EMAST status. BACKGROUND: Snail1 is an evolutionary preserved zinc-finger transcription protein which contributes to Epithelial-to-mesenchymal transition (EMT). EMT initiates invasion and proliferation in many tumors. Elevated microsatellite alteration at selected tetranucleotide repeats (EMAST) is a marker of poor prognosis in patients with colorectal cancer (CRC). We hypothesized that Snail1 overexpression is an important mediator of metastasis and decreased survival in CRCs that characteristically have EMAST phenotype. METHODS: Quantitative real-time polymerase chain reactions were carried out to analyze the expression levels of Snail1 in both normal and tumor specimens from a total of 122 paraffin-embedded tissues (FFPE) of CRC sample with known EMAST status. The correlation between Snail1 expression and clinicopathological characteristics, survival, and EMAST status were examined. RESULTS: Snail1 overexpression was detected in tumor tissues in 32% of all examined patients and its positive expression was related to metastasis (p=0.001) and EMAST+ phenotype (P=0.017). Further, positive Snail1 expression correlates with poor overall survival in CRC patients (P=0.01). CONCLUSION: Our findings suggest that Snail1 overexpression is not only associated with EMAST but also with clinicopathological variables of poor prognosis. These results indicate that Snail1 expression levels may be useful for establishing novel therapeutic strategies and could help survival improvement in CRC patients.