Introduction:
Cancer is the most common health problem, with high morbidity and mortality. Cancer is the second leading cause of death worldwide. Poor understanding of the disease and the minimal number of treatment modalities have led to increased mortality rates. Gene editing has been a remarkable tool in biotechnology and medicine. Gene editing is made possible in vivo with high accuracy. Gene editing is used in gene therapy and involves changing the existing DNA in the cell. It will help allow genetic material to be added, removed, or altered at specific locations inside the genome.
Gene editing can be done with a controlled modification under precision. Most commonly used gene-editing enzymes are zinc-finger nucleases (ZNF), clustered regularly interspaced short palindromic repeats (CRISPR) or CRISPR-associated nuclease-9 (Cas9), homing meganucleases, and transcription activator-like effector nucleases (TALENs). CRISPR is a widely used tool and has helped in treating cancer along with many diseases like Duchenne muscular dystrophy, cystic fibrosis, and thalassemia that are difficult to cure completely.
How Is Gene Editing Done?
The Cas9 enzyme does not require reengineering for each individually targeted sequence, but the rest of the enzymes need it. To target genes at a particular site in the genome of the organism, HR (homologous recombinant) has been used. It will create templates (homologous DNA constructs) that resemble the target gene sequence.
Oncolytic virotherapy is a recently identified treatment strategy and is highly efficient for treating certain cancer types. This uses oncolytic viruses, which are genetically modified or native, and they replicate selectively inside cancer cells excluding normal cells.
Herpes simplex virus type 1 (HSV-1) is an oncolytic virus that has been used as a vector in treating cancer with cancer therapy. The CRISPR technique has helped fasten the genetic manipulation of oncolytic viruses compared to conventional techniques.
The vector can be administered by injection into a specific tissue, where individual cells uptake it, or by intravenous (IV) infusion. Another approach is to remove a sample of the patient's cells and expose them to the vector in a laboratory setting. After the cells uptake the vector, they are returned to the patient. If successful, the vector will deliver a new gene that produces a functional protein or editing molecules that correct a DNA error and restore protein function.
What Are the Methods of Editing Tumor Cells?
There are four methods, mainly:
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Gene knockout is a potential yet simple and common method to edit pathogenic genes. One example of gene editing involves editing the CCR5 gene in CD4+ T cells of individuals who have been infected with HIV. This approach helps combat HIV infection.
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Targeted insertion of DNA fragments will help restore the normal sequence by correcting the mutation.
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Translocation of chromosomal segments is seen in close association with tumorigenesis. This has helped in extensive research on cancer pathogenesis.
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Base editing is useful in obtaining the point mutation during various gene editing steps like monitoring, screening, etc.
What Is the Significance of CRISPR?
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CRISPR-Cas9 is an easy and flexible engineering technology.
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This system is a naturally occurring immunity and happens when there is an external viral invasion or invasion of genetic materials.
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To protect themselves, microbes will capture the intruder's DNA as snippets. These snippets of DNA are stored away as segments called CRISPR.
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When the same invasion occurs again, these DNA fragments will help the Cas enzyme to separate the invader’s DNA.
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Hence it was widely used in editing the mammalian genome with accuracy and designing specific breaks in the DNA (deoxyribonucleic acid) double helix.
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Hence, it is considered a promising treatment method as it helps in understanding gene participation, initiation of disease, and its progression.
The CRISPR tool is made up of two main components, a DNA-cutting enzyme and a guide RNA. The most common DNA-cutting enzyme is Cas9. The guide RNA is designed by scientists to mimic the gene to be edited, also known as the target. The Cas cuts or slices up the DNA once the guide RNA matches with the target’s DNA. The efficacy of delivery of the CRISPR has been challenging in cancer treatment. To overcome this, nanoparticles were used. Nanoparticles have been used recently to target PLK-1 in melanoma in the form of a gold or lipid-CRISPR system. Again, there is a challenge in developing nano careers that are safe and efficient inside the body.
What Are the Limitations of the CRISPR-Cas9 System?
CRISPR has been a novel method and is a wonder according to biological scientists, as it has extensive applications in the screening and therapeutic management of many diseases including cancer and genetic diseases. The efficacy of CRISPR-Cas9 technology can be challenging in terms of editing effectiveness and the fitness of modified cells. When the editing efficiency is more, the number of cell populations with the necessary genetic alterations increases, while fewer modified cells result from poor editing efficiency. Edited cells often have fitness disadvantages compared to unedited cells, which will further reduce their therapeutic effects.
Fighting cancer requires a decreased initial quantity of edited cells, but if the edited cells are more flexible than unedited cells, there is an advantage. Additionally, delivery techniques and potential off-target effects can pose challenges. Off-target editing refers to modification happening in healthy non-cancer cells. Scientists are worried that this can modify healthy cells into cancerous cells.
Conclusion:
Cancer has become a world-level burden and the need for its eradication has increased exponentially. Gene mutations have also increased along with the fast-developing world and industrialization. Thanks to the development in molecular biology, there are newer developments like gene therapy to slow down cancer progression. Gene therapy has found its irreplaceable position in cancer therapy. Due to its high precision and ease of use, CRISPR is the most commonly used tool and is considered a game changer. CRISPR-Cas9 has been found to provide excellent results in cancer treatment due to its efficiency and precision. More research is still under process to improve the existing results and reduce the shortcomings.
