Published online Nov 14, 2020. doi: 10.3748/wjg.v26.i42.6556
Peer-review started: August 29, 2020
First decision: September 12, 2020
Revised: September 24, 2020
Accepted: October 20, 2020
Article in press: October 20, 2020
Published online: November 14, 2020
In the last two decades, the vision of a unique carcinogenesis model for colorectal carcinoma (CRC) has completely changed. In addition to the adenoma to carcinoma transition, colorectal carcinogenesis can also occur via the serrated pathway. Small non-coding RNA, known as microRNAs (miRNAs), were also shown to be involved in progression towards malignancy. Furthermore, increased expression of certain miRNAs in premalignant sessile serrated lesions (SSLs) was found, emphasizing their role in the serrated pathway progression towards colon cancer. Since miRNAs function as post-transcriptional gene regulators, they have enormous potential to be used as useful biomarkers for CRC and screening in patients with SSLs particularly. In this review, we have summarized the most relevant information about the specific role of miRNAs and their relevant signaling pathways among different serrated lesions and polyps as well as in serrated adenocarcinoma. Additional focus is put on the correlation between gut immunity and miRNA expression in the serrated pathway, which remains unstudied.
Core Tip: In addition to the adenoma to carcinoma transition, colorectal carcinogenesis can also occur via the serrated pathway. In most serrated polyps, the pathway is believed to include the acquisition of a mutation in a gene that regulates mitogen-activated protein kinase (MAPK) pathway, disruptions to the Wnt signaling pathway and widespread methylation of CpG islands. Moreover, there are less data about different microRNAs (miRNAs) expression profiling in serrated adenomas with different grades of dysplasia. In contrast to the conventional colorectal carcinogenesis, the pivotal role of miRNAs and their relevant signaling pathways in the serrated pathway of carcinogenesis is still to be elucidated because of an insufficient number of studies conducted to clarify separate steps in the process.