Colorectal cancer is the third most common cancer. It first appears as adenomas, benign tumours, but often develops into locally invasive cancers and finally metastasises to spread to other tissues. Surgery and radio-chemotherapy are available, but once metastatic, it is considered incurable. So biomarkers for early diagnosis have become the holy grail of researchers.
Recently, non-coding circular RNAs are being widely explored as cancer biomarkers. Rajabrata Bhuyan from the Banasthali Vidyapith and Angshuman Bagchi from the University of Kalyani started searching for circular RNAs that can act as biomarkers.
Circular long non-coding RNAs are abundant and more stable than most linear RNAs. Comparing the transcriptome datasets of 10 pairs of colorectal cancer and normal colorectal cell lines, the researchers identified 122 circular RNAs that are differentially expressed in colorectal cancer. Eighty-five were highly up-regulated and the rest were down-regulated in colorectal cancer.
Using bioinformatic resources such as Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes, the team examined the related gene and gene products to understand their role in tumorigenic pathways.
The up-regulated circular RNAs were seen to be involved in regulating the expression of the proteins involved in cancer invasion, dissemination and metastasis. The down-regulated ones were tumour suppressor genes that inhibit cell growth and reduce tumorigenesis.
The duo also found 14 differently expressed circular RNAs which act as sponges in colorectal cancer. These ‘sponges’ can absorb 25 unique microRNAs and 117 RNA binding proteins, and thus inactivate them. This affects the expression of more than 2900 genes, which regulate different cancer-related pathways.
“We are slowly unravelling the complexity and molecular mechanisms of circular RNAs and their potential role in colorectal cancer development and progression”, says Rajbrata, Banasthali Vidyapith, Rajasthan.
“Further research on circular RNAs can help identify ideal biomarkers for detecting colorectal cancer”, says Angshuman, University of Kalyani, West Bengal.
The team believes that it is also possible to develop circular RNA as therapeutic targets for colorectal cancer.
Gene, 762: 145035 (2020)
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