The Footsteps of the New Era in Cancer: CRISPR

Cancer is one of the major causes of disease-associated mortality, considering the rising incidence globally. On the other hand time, advancements in cancer prevention and treatment have led to increased survival times or even cancer cures. Enhanced knowledge of the underlying tumour biology has been a major key to innovation in cancer therapy. As a result of this insight, small molecules and antibodies that target specific proteins in oncogenic signalling pathways have been developed1.

Cancer has hallmark qualities as multiple genetic and epigenetic alterations in oncogenes and tumour-suppressor genes2. Each cancer patient is seen as a distinctive case since everyone’s genetic makeup is individual, and cancer is based on mutations. Since discovering that DNA alterations are the primary cause of cancer, researchers have been looking for a simple method to reverse these alterations by manipulating DNA3.

In 2013, a group of researchers demonstrated how the gene-editing tool CRISPR-Cas9 technology could modify the DNA of human cells highly precisely and simply.  The new technology has completely changed the parameters of what is feasible and what is unfeasible in the scientific community. Cancer researchers seized the opportunity to utilize CRISPR as soon as3. Recent developments in CRISPR technology have also enabled human T cells, a kind of immune cell, to modify their DNA effectively, which holds enormous potential to enhance the effectiveness of cancer therapy4.

Figure 1: The CRISPR-Cas9 Complex (blue and yellow) can precisely cut DNA (red)1.
(Alfred Pasieka/Science Photo Library).

According to the last article published in Nature, a new clinical trial has demonstrated that scientists may utilize CRISPR gene editing to change immune cells so altered immune cells will recognize mutated proteins unique to a person’s tumours. Then, those can be safely released into the body to locate and eliminate their target. This is the first attempt to integrate two remarkable areas of cancer research: manipulating T cells more effectively target tumours, and using gene editing to provide individualized treatments. The method was evaluated on 16 individuals who had solid tumours, including breast and colon tumours5.

Despite all these remarkable CRISPR advances, researchers walk on thin ice due to potential hazards such as DNA fragment alterations than targeted, and off-target CRISPR activity3.

The Mechanism of CRISPR

First discovered in E. coli in 1987, clustered regularly interspersed short palindromic repeats (CRISPR) have now been discovered in numerous other bacterial species. These sequences were linked to phage DNA by various groups in 2005, leading to the hypothesis that they represent a component of bacterial adaptive immunity6.

These investigations were then expanded to experimentally prove the connection between CRISPR and its CRISPR-associated proteins (Cas) and the adaptive immunity that specifically targets foreign virus DNA. Specifically, two different RNAs—the trans-activating RNA (tracrRNA) and the CRISPR targeting (crRNA) RNA—activate and direct Cas proteins to bind viral DNA sequences, which are then cleaved6.

A subset of these CRISPR systems is especially appealing for use in genome editing since it only needs one Cas protein to target a specific DNA sequence. The technique was made even simpler by combining crRNAs and tracrRNAs into a single guide RNA (sgRNA). The first time that the Cas protein acquired from Streptococcus pyogenes (SpCas9) was utilized for RNA-guided DNA cleavage in mammalian cells was in 2013, setting the stage for the adoption of CRISPR-Cas9 as a commonly used genome-editing tool. The Cas9 nuclease changes conformation upon sgRNA binding and is guided to its target site before cleaving the target DNA. A 20-nucleotide sequence identifies the binding specificity. Two nuclease domains introduce a double-strand break (DSB) in the target sequence, after unwinding the DNA. Two distinct processes of repair are used by the host cell in response to a DSB. An error-prone repair technique called non-homologues end joining (NHEJ) frequently results in insertions or deletions. This process may result in premature stop codons, frameshift mutations, or non-sense-mediated decay to the target gene, leading to loss of function. These pose the potential dangers of CRISPR3. In contrast, homology-directed repair (HDR) reassembles cleaved DNA through aided recombination of DNA donor templates6.

Figure 2: CRISPR-Cas9 function and different repair mechanisms2

A New Clinical Trial

Initially, Ribas and the team sequenced DNA from tumour tissues and blood samples to search for mutations that are present in the tumour. Each tumour has a unique set of mutations. Therefore, meticulous teamwork has been demonstrated so far. The researchers then applied algorithms to estimate which mutations were most likely to have the ability to activate T cells. The researchers utilized CRISPR genome editing to implant the genes encoding these receptors into each participant’s T cells after conducting a variety of analyses to create T-cell receptors-proteins that are capable of detecting cancer alterations. After the injection of the engineered cells, each participant was required to take medicine to lower the number of immune cells they produced. Engineered T cells with up to three different targets were given to each of the 16 individuals. Following treatment, the modified cells were discovered circulating in their blood and were more abundant near tumors than non-edited cells had been before the therapy. Five of the patients had stable disease after one-month treatment, meaning their tumors had not become bigger. Only two persons reported adverse effects, which were probably brought on by the T cells’ activity after being altered5.

Figure 3: Engineering of T cells using CRISPR-Cas9 in cancer patients3.

Despite the treatment’s poor efficiency, the safety of the method was established by the researchers using very low dosages of T cells, according to Ribas. The engineered cells will also spend less time being cultured outside of the body and may be more active when they are infused as researchers figure out ways to hasten the development of the medicines5.

Figure 4: The mechanism of CRISPR technology4.

Conclusion

Genome editing and gene therapy to alter immune specialization have the potential to increase the effectiveness and safety of engineered T cells. With the use of the strong gene-editing tool CRISPR and the CRISPR-Cas9 endonuclease, cancer immunotherapy may be improved by being able to target several genes in T cells4. Many researchers were worried about the off-target consequences of this technology in its initial phases. However, studies conducted over time have demonstrated the effectiveness and specificity of utilizing CRISPR in medical settings. Encouraging findings from research conducted all over the world suggest that it could one day prove to be a potent tool in the fight against cancer7.

References:

  1. Zhan, T., Rindtorff, N., Betge, J., Ebert, M. P., & Boutros, M. (2019). CRISPR/Cas9 for cancer research and therapy. Seminars in Cancer Biology, 55, 106-119. Retrieved December 18, 2022, from https://doi.org/10.1016/j.semcancer.2018.04.001
  2. Sánchez-Rivera, F. J., & Jacks, T. (2015, June 4). Applications of the CRISPR–cas9 system in cancer biology. Nature News. Retrieved December 18, 2022, from https://www.nature.com/articles/nrc3950
  3. NCI Staff. (2020, July 27). HOW CRISPR is Changing Cancer Research and treatment. National Cancer Institute. Retrieved December 18, 2022, from https://www.cancer.gov/news-events/cancer-currents-blog/2020/crispr-cancer-research-treatment
  4. Stadtmauer, E. A., Fraietta, J. A., Davis, M. M., Cohen, A. D., Weber, K. L., Lancaster, E., … & June, C. H. (2020, February 6).CRISPR-engineered T cells in patients with refractory cancer – science. Retrieved December 18, 2022, from https://www.science.org/doi/10.1126/science.aba7365
  5. Ledford, H. (2022, November 10). CRISPR cancer trial success paves the way for personalized treatments. Nature News. Retrieved December 18, 2022, from https://www.nature.com/articles/d41586-022-03676-7
  6. Rindtorff, N., Zhan, T., Betgeab, J., Ebertb, M. P., & Boutrosad, M. (2018, April 16). CRISPR/Cas9 for cancer research and therapy. Seminars in Cancer Biology. Retrieved December 18, 2022, from https://www.sciencedirect.com/science/article/pii/S1044579X17302742
  7. Full stack genome engineering. Synthego. (n.d.). Retrieved December 18, 2022, from https://www.synthego.com/crispr-cancer

Figure References:

  1. Ledford, H. (2022, November 10). CRISPR cancer trial success paves the way for personalized treatments. Nature News. Retrieved December 18, 2022, from https://www.nature.com/articles/d41586-022-03676-7
  2. Rindtorff, N., Zhan, T., Betgeab, J., Ebertb, M. P., & Boutrosad, M. (2018, April 16). CRISPR/Cas9 for cancer research and therapy. Seminars in Cancer Biology. Retrieved December 20, 2022, from https://www.sciencedirect.com/science/article/pii/S1044579X17302742
  3. Stadtmauer, E. A., Fraietta, J. A., Davis, M. M., Cohen, A. D., Weber, K. L., Lancaster, E., … & June, C. H. (2020, February 6).CRISPR-engineered T cells in patients with refractory cancer – science. Retrieved December 18, 2022, from https://www.science.org/doi/10.1126/science.aba7365
  4. Full stack genome engineering. Synthego. (n.d.). Retrieved December 18, 2022, from https://www.synthego.com/crispr-cancer

Inspector: Nadir KERESTECİ

Yorum bırakın

E-posta adresiniz yayınlanmayacak. Gerekli alanlar * ile işaretlenmişlerdir