Systematic Reviews
Copyright ©The Author(s) 2022. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastrointest Oncol. Mar 15, 2022; 14(3): 734-745
Published online Mar 15, 2022. doi: 10.4251/wjgo.v14.i3.734
Association of Blastocystis hominis with colorectal cancer: A systematic review of in vitro and in vivo evidences
Vinoth Kumarasamy, Wahib Mohammed Atroosh, Deepa Anbazhagan, Mona Mohamed Ibrahim Abdalla, Meram Azzani
Vinoth Kumarasamy, Deepa Anbazhagan, Department of Microbiology and Parasitology, Faculty of Medicine, Bioscience and Nursing, MAHSA University, Jenjarom 42610, Selangor, Malaysia
Vinoth Kumarasamy, Department of Preclinical Sciences, Faculty of Medicine and Health Sciences, Universiti Tunku Abdul Rahman, Kajang 43000, Selangor, Malaysia
Wahib Mohammed Atroosh, Department of Parasitology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur 50603, Wilayah Persekutuan, Malaysia
Wahib Mohammed Atroosh, Department of Microbiology and Parasitology, Faculty of Medicine and Health Sciences, University of Aden, Aden 00, Yemen
Mona Mohamed Ibrahim Abdalla, Human Biology Department, International Medical University, Bukit Jalil 57000, Kuala Lumpur, Malaysia
Meram Azzani, Department of Community Medicine, Faculty of Medicine, Bioscience and Nursing, MAHSA University, Jenjarom 42610, Selangor, Malaysia
Author contributions: Azzani M designed the research, performed the literature search and extracted the data; Kumarasamy V wrote the discussion and extracted the data; Atroosh WM wrote the methodology and extracted the data; Anbazhagan D wrote the results and extracted the data; Abdalla M wrote the introduction and extracted the data; All authors read and approved the final manuscript.
Conflict-of-interest statement: Dr. Azzani has nothing to disclose.
PRISMA 2009 Checklist statement: The authors have read the PRISMA 2009 Checklist, and the manuscript was prepared and revised according to the PRISMA 2009 Checklist.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Meram Azzani, PhD, Senior Lecturer, Department of Community Medicine, Faculty of Medicine, Bioscience and Nursing, MAHSA University, Bandar Saujana Putra, Jenjarom 42610, Selangor, Malaysia. dr_memeazzani@yahoo.com
Received: May 17, 2021
Peer-review started: May 17, 2021
First decision: July 4, 2021
Revised: July 16, 2021
Accepted: February 22, 2022
Article in press: February 22, 2022
Published online: March 15, 2022
Processing time: 296 Days and 23.8 Hours
Abstract
BACKGROUND

Recently, there have been several findings that showed intestinal colonisation of Blastocystis hominis (Blastocystis) as a risk factor to the worsening of colorectal cancer (CRC). However, studies have shown controversial results in the pathogenicity of Blastocystis.

AIM

To review systematically the evidence available on the association between CRC and Blastocystis and the prevalence of Blastocystis in CRC patients and to investigate cytopathic and immunological effects of Blastocystis in in vitro and in vivo studies.

METHODS

PRISMA guidelines were utilised in conducting this systematic review. Original articles published before February 2, 2020 were included. PubMed, Science Direct, Scopus and Google scholar databases were searched. Manual searching was carried out to find articles missed during the online search.

RESULTS

Out of 12 studies selected for this systematic review, seven studies confirmed the prevalence of Blastocystis and found it to be between 2%-28% in CRC patients, whereby subtype 1 and subtype 3 were predominantly seen. A total of four studies employing in vitro human colorectal carcinoma cell line study models showed significant cytopathic and immunological effects of Blastocystis. In addition, one in vivo experimental animal model study showed that there was a significant effect of infection with Blastocystis on exacerbation of colorectal carcinogenesis.

CONCLUSION

Blastocystis is a commonly identified microorganism in CRC patients. These studies have provided supportive data that Blastocystis could exacerbate existing CRC via alteration in host immune response and increased oxidative damage. Future studies of CRC and Blastocystis should attempt to determine the various stages of CRC that are most likely to be associated with Blastocystis and its relationship with other intestinal bacteria.

Keywords: Blastocystis hominis; Colorectal cancer; Cytopathic effect; Immunological effect

Core Tip: Certain gut microorganisms are known to be important factors associated with initiation and development of colorectal cancer (CRC). However, data on the roles of parasites are vague and restricted. Blastocystis hominis (Blastocystis) is one of the most commonly recovered microorganisms in faecal specimens, and its widespread presence is found in CRC patients. This systematic review aims to quantify the studies published so far that revealed the association of Blastocystis and CRC. We sought to identify the prevalence of Blastocystis and its subtypes among CRC patients, in vitro studies using Blastocystis antigen and in vivo studies using animal models.