CRISPR Technology in Disease Modelling and Drug Discovery
By T. Chakraborty, Ph.D.
In the last couple of decades, genome editing techniques have revolutionized various aspects of biological research. With improvements in technology over time, the scientific community is now in a position like never-before to unravel the various mysteries surrounding biological systems. Gene editing has been used to answer simple questions, like a particular gene’s function, to complex conundrums such as deciphering the cause of drug-resistance in cancer. This rapidly evolving technology finds use in various disease-related fields, ranging from oncology to neurodegenerative, metabolic, and hematological diseases .
Clustered regularly interspaced short palindromic repeat/CRISPR-associated protein 9 (CRISPR/Cas9) is the latest technology that has gained a lot of prominence in gene editing in the last decade. The CRISPR-Cas9 gene-editing technology is simple to use and cheaper than its peers like TALENS and Zinc-finger Nucleases (ZFN). Further, this technology can edit multiple locations simultaneously, making it more efficient, scalable, and an indispensable tool in biological systems research. This technology’s impact was further validated when the Nobel Prize for Chemistry this year was bestowed upon two women scientists, Dr. Emmanuelle Charpentier and Dr. Jennifer A. Doudna, the pioneers of this technology .
CRISPR-Cas9 in Model Development for Drug Discovery
Pharmaceutical industries invest more than a billion-dollar for every drug from inception to approval. For every drug approved, they have to start with around 25 targets approximately. The cost associated increases as each drug move up the ladder, from the lead identification stage, through preclinical stages to clinical trials. Hence, identifying and using model systems that mimic the human system can reduce the associated cost in the long run. CRISPR-Cas9 technology has revolutionized the field of disease modeling both in cell culture and animal models.
On the eve of the World CRISPR day virtual meeting organized by Synthego Corporation, Dr. Benjamin Taylor from AstraZeneca noted that the CRISPR-Cas9 technology had enabled the pharmaceutical industries to develop hundreds of cell culture models to test the efficacy of cancer drugs in various mutated lines to mimic the mutations which are observed in cancer patients. This approach has led to the identification of drug-resistant and drug-sensitive mutations. The identification of these mutations early on in the process of drug discovery will reduce the cost immensely. CRISPR-Cas9 has been used to make complex point mutations to develop rodent models of lung cancer. Additionally, it has also been used to make novel disease models in invertebrates like Drosophila and C. elegans. These models have been used for genome-wide screens and drug screens to find novel targets for therapy .
CRISPR-Cas9 in Cancer Therapy
Initiatives led by the big and small pharma companies worldwide have helped cancer immunotherapy come to the forefront in recent years. Our immune system is capable of fighting the proliferating cancer cells. To bypass our immune system, the cancer cells can upregulate certain proteins called immune checkpoint proteins, which will reduce our body’s ability to fight these cells.
Chimeric Antigen Receptor-T cell (CAR-T) therapy is an immunotherapy that has recently been used to fight different kinds of hematological cancers with great success. The therapy involves deriving cells from a cancer patient, genetically manipulate them to express certain receptors capable of mounting an immune response, and then re-introduce back into the patients. Using the CRISPR-Cas9 technique, scientists have been able to perform genetic manipulations in the generation of CAR_T cells with precision. This type of CAR-T cell therapy can get expensive. Hence pharmaceutical companies like Hira labs are developing off-the-shelf, allogeneic CAR-T cell therapy, which is faster, cheaper, and easily accessible. The advancements in gene editing technologies like Cas-CLOVER, where two guide RNAs are used instead of one, greatly help develop these next-generation cancer therapies .
CAR-T therapies have not been largely successful in solid tumors due to an immunosuppressive environment and tumor heterogeneity combined with a lack of access. The recent development of CRISPR tools has allowed scientists to develop CAR-T cells that can use the host immune system and target solid tumors. Dr. Imran House from Peter MacCallum Cancer Centre, Melbourne, Australia, discussed the potential of using this genome editing technique in driving various inflammatory cytokines in the presence or absence of checkpoint inhibitory proteins. Inflammatory cytokines, if expressed untargeted, can have serious side effects. Dr. House demonstrated that CRISPR CAR-T cells could be targeted against the tumors to release pro-inflammatory cytokines like Interleukin 12 .
CRISPR-Cas9 for Studying SARS-CoV-2
The COVID-19 pandemic has infected more than 40 million people and has been responsible for the death of nearly 1.3 million people so far. Due to the advancement of CRISPR techniques, scientists have been able to develop innovative testing strategies and potential drugs in record-breaking time. CRISPR technique was recently used in the development of testing for SARS-CoV-2 in less than 5 minutes.
The test works by designing a guide RNA against the RNA genome of SARS-CoV-2. If the virus is present, the guide-RNA will bind to it and cut in the viral genome that leads to the release of a fluorophore. This rapid testing is easy to use and will reduce the transmission rate. Scientists, including Nobel laureate Dr. Doudna, are currently working on validating this testing approach .
CRISPR-Cas9 has also been used to generate protein-protein interaction maps, which have potentially identified novel drug targets for the treatment of COVID-19. Dr. Nevan Krogan, from the University of California, San Francisco, discussed these findings during the virtual conference held on October 20th. The worldwide collaboration among scientists in academia and various industries has led to discovering multiple drug targets for curing SARS-CoV-2 in a short span of time. Many of these targets are currently in clinical trials. Further, Dr. Krogan said that using CRISPR in combination with interaction maps will prepare us for pandemics that we may encounter in the future [2,5].
In the world of science, there exists a handful of technologies that have transformed and taken biology to new heights in a short amount of time. In less than a decade, CRISPR-Cas9 has advanced the field of biomedical sciences leaps and bounds and promises to deliver bigtime in fields with unmet medical needs.
Editor: Rajaneesh K. Gopinath, Ph.D.
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