The crispr revolution in cancer research and therapy

Narges Rashidi,1 Amirhossein ahmadi,2,* Seyed javad hosseini,3

1. Department of Biology, Faculty of Science, Persian Gulf University, Bushehr, Iran
2. Department of Biology, Faculty of Science, Persian Gulf University, Bushehr, Iran
3. Department of Biology, Faculty of Science, Persian Gulf University, Bushehr, Iran

Abstract

Introduction

Cancer is a complex disease that arises from various genetic and epigenetic alterations which drive cellular transformation, tumor growth, cell invasion and metastasis. although several drugs have developed for cancer treatment so far, mortality and morbidity is still a major problem in all around the world. this may mainly attribute to the fact that the cancer biology, genetics and mechanisms of drug resistance remain to be fully understood. despite the large amount of data available on thousands of gene mutations in different cancers, much less is known about their function due to laborious and time consuming functional analysis techniques. however, introduction of crispr as a genome editing tool could revolutionize the cancer research and treatment. the clustered regulatory interspaced short palindromic repeats (crispr) and an endonuclease named crispr associated protein (cas) was first discovered as the defense system against bacteriophages in e.coli. in this system the cas endonuclease is guided by a targeting rna and induce a double strand break (dsb) in target site. crispr/cas9 system from streptococcus pyogenes together with a small guide rna (sgrna) was first used as a genome editing tool in 2013 in mammalian and now become a widely applicable dna editing system. in this system host cell could repair dsb through non-homologues end joining (nhej) or homology directed repair (hdr) which results in insertion/deletion or recombination respectively. the second way be exploited to introduce well defined mutations by transferring altered donor templates into targeted cells.

Methods

Pubmed a freely available search engine for the medline database was selected as literature search tool. a keyword of cacer combined with crispr retrieved original articles which were used to review and write this article.

Results

Crispr/cas9 technology opens new avenues for cancer research and therapy as follow: 1) target discovery by crispr/cas9 screens: in this method a cell population with diverse gene knockouts is generated and this knockout cell pools are mainly used to find genotype-specific vulnerabilities and drug targets in cancer researches. indeed, those genes which their functional depletion leads to a reduced viability can be potential drug targets. another application of crispr/cas9 screening is to find how cancer responds to drug treatment. 2) investigation of non-coding genome of cancer: the most part of the human dna consists of non-coding regions. these regions could be regulatory elements such as enhancers or non-coding rnas. the expression of non-coding rnas is known to be dysregulated in cancer. in addition, the transcription of oncogenes can be controlled by enhancer elements. therefore, the comprehensive understanding of non-coding elements will provide deeper insights into cancer biology. recently, crispr/cas9 has shown its potential for the interrogation of noncoding elements. 3) generation of organoid cancer model: adult stem cell derived organoids are now popular in vitro model of healthy and diseased human epithelia. in this method stem cells from multiple adult tissue types are isolated and cultivated in 3d and finally form organoids in a cell culture dish. organoids provides the study of tumor development and progression in vitro. crispr/cas9 is the useful tool to development of cancerous organoid models. 4) genome editing and clinical application: the ability to edit genes, in humans, has been discussed long before genome editing technologies had been developed. the first clinical trial using crispr for cancer therapy has enrolled the first patient at sichuan university’s west china hospital in chengdu in 2016. in this trial the safety of programmed cell death protein-1 (pd-1) knockout engineered t cells ex vivo is evaluated in treating metastatic non-small cell lung cancer. this trials can be regarded as first proof-of-concept study for applying ex vivo crispr/cas9 knockout in cancer treatment.

Conclusion

Altogether, since its development into a genome editing tool, the crispr/cas9 technology has revolutionized biology by providing a simple and versatile method to manipulate the genome, transcriptome and epigenome across a broad range of organisms. the potential of crispr/cas9 for both basic and translational cancer research is yet beginning to unfold.

Keywords

Cancer, crispr, organoid, target discovery