Cancer Breakthroughs Unleashed by CRISPR

The discovery and development of the CRISPR-Cas9 system from a bacterial adaptive immune system to a powerful gene-editing tool has revolutionized genome engineering. The CRISPR system is flexible, efficient, and simple, allowing precise and targeted changes to genetic sequences to be made. The technology has now been utilized in numerous fields, but in particular, the use of CRISPR has opened up a realm of possibilities for oncology, changing the way we approach the diagnosis, treatment, and prevention of cancer. This article looks at the application of CRISPR in oncology and some of the breakthroughs that CRISPR has made possible.

Enhancing precision medicine

CRISPR is being used to refine precision medicine techniques by disrupting specific oncogenes or activating specific tumor suppressors—for example, KRAS is the most frequently mutated oncogene in human cancers and so represents an important therapeutic target. By using CRISPR to specifically knock out mutant KRAS in cancer cells, Kim et al., were able to inhibit cancer cell proliferation both in vitro and in vivo.¹ More recently, Jang et al., successfully used a universal CRISPR-mediated prime editor gRNA to correct 12 types of KRAS mutations that account for 94% of all known mutations to this oncogene.² By targeting the genetic mutations responsible for driving tumor growth and metastasis, CRISPR holds the potential to offer personalized and more effective treatment options in the realm of cancer care.

Engineering immunotherapies

Immunotherapy has emerged as a promising approach to treating cancer by using the body's own immune system to target and destroy cancer cells. Using CRISPR, scientists can precisely engineer T cells to express CARs (chimeric antigen receptors) that specifically recognize and attack cancer cells, enhancing the efficacy of these therapies and reducing potential side effects. Rupp et al., successfully utilized CRISPR to engineer T cells to express CARs targeting CD19 in patients with B-cell lymphoma leading to durable remissions in a significant proportion of treated patients.³ CRISPR has also been used to develop non-autologous, or “universal” CAR-T cells that could be used in any patient without the need for HLA matching—thereby reducing costs and making CAR T-cell therapy accessible to those patients without the sufficient numbers of healthy T cells required for treatment.⁴

Overcoming drug resistance

One of the major challenges in cancer treatment is the development of drug resistance to therapeutic agents, which can lead to treatment failure and disease relapse. Knock out of key genes with CRISPR has been shown to overcome drug resistance in cancer cells—by using CRISPR to target a gene encoding a glycoprotein responsible for transporting multiple types of chemotherapeutic agents out of cells and so cause multidrug resistance, Yang et al., was able to significantly increase sensitivity to chemotherapy drugs.⁵

CRISPR has also provided researchers with a powerful tool to better understand the biological mechanisms that underpin drug resistance and identify potential strategies to overcome it. CRISPR can be used to create animal and cellular models to accurately mimic drug-resistant phenotypes, as well as perform whole-genome screening to aid in the discovery of new therapeutic targets and the development of more effective drugs. For example, a whole-genome CRISPR screen in 324 human cancer cell lines from 30 cancer types was used to develop a data-driven framework to successfully identify novel therapeutic targets and provide prioritization of those candidates for drug discovery.⁶

Early cancer detection

CRISPR-based technologies are also being applied in cancer diagnostics, enabling the detection of early-stage tumors with high accuracy and sensitivity, and potentially at point-of-care without the requirement for special instrumentation. A study published in Science demonstrated the use of DETECTR, a highly sensitive and specific CRISPR-based assay that can detect human papillomavirus (HPV) in patient samples that could aid in the early detection of HPV-associated cervical cancer.⁷

Unleashing gene therapy

Gene therapy holds immense promise in the field of oncology, with the potential to correct genetic defects responsible for cancer development. But CRISPR has also been utilized to leverage the tumor cells themselves to treat cancer, by using gene editing to make tumor cells or therapeutic tumor cells (ThTCs) that are resistant to interferon-β and release immunomodulatory agents such as IFN-β and granuloycte-macrophage colony-stimulating factor (GM-CSF). ThTCs were then able to eliminate glioblastoma tumors in mice as well as provide immunity from cancer.⁸

Revolutionizing oncology with CRISPR

The breakthroughs made possible by CRISPR gene editing have demonstrated the potential for more targeted and effective therapies, sensitive and accurate diagnostics, enhanced precision medicine approaches, and enabled the discovery of new therapeutic targets. As CRISPR continues to evolve, we can anticipate even more advancements that will revolutionize cancer diagnosis and treatment, for improved patient outcomes.

Key Takeaways

• Cancer is primarily a genetic disease, with mutations to the genome changing the way cells grow and divide—therefore correcting those changes by manipulating DNA is an attractive means with which to treat and prevent cancer
• Previous gene-editing technologies such as ZFNs and TALENs were technically challenging to use and expensive—but have since been superseded by the development of CRISPR
• CRISPR gene-editing technology now offers a simple and flexible way to precisely make targeted changes virtually anywhere in the genome, including gene knockout, modulating gene expression with CRISPRi and CRISPRa, as well as base editing and prime editing
• This revolutionary gene-editing tool has opened up a realm of possibilities for targeted cancer therapies, as well as changed the way we look to treat and prevent cancer

References

1. Kim, Wonjoo et al. “Targeting mutant KRAS with CRISPR-Cas9 controls tumor growth.” Genome research, vol. 28,3 374–382. 11 Jan. 2018, doi:10.1101/gr.223891.117

2. Jang, Gayoung et al. “CRISPR prime editing for unconstrained correction of oncogenic KRAS variants.” Communications biology vol. 6,1 681. 30 Jun. 2023, doi:10.1038/s42003-023-05052-1

3. Rupp, Levi J et al. “CRISPR/Cas9-mediated PD-1 disruption enhances anti-tumor efficacy of human chimeric antigen receptor T cells.” Scientific reports vol. 7,1 737. 7 Apr. 2017, doi:10.1038/s41598-017-00462-8

4. Benjamin, Reuben et al. “Genome-edited, donor-derived allogeneic anti-CD19 chimeric antigen receptor T cells in paediatric and adult B-cell acute lymphoblastic leukaemia: results of two phase 1 studies.” Lancet (London, England) vol. 396,10266 (2020): 1885-1894. doi:10.1016/S0140-6736(20)32334-5

5. Yang, Yang et al. “Targeting ABCB1-mediated tumor multidrug resistance by CRISPR/Cas9-based genome editing.” American journal of translational research vol. 8,9 3986-3994. 15 Sep. 2016

6. Behan, Fiona M et al. “Prioritization of cancer therapeutic targets using CRISPR-Cas9 screens.” Nature vol. 568,7753 (2019): 511-516. doi:10.1038/s41586-019-1103-9

8. Chen, Janice S et al. “CRISPR-Cas12a target binding unleashes indiscriminate single-stranded DNase activity.” Science (New York, N.Y.) vol. 360,6387 (2018): 436-439. doi:10.1126/science.aar6245

9. Chen, Kok-Siong et al. “Bifunctional cancer cell-based vaccine concomitantly drives direct tumor killing and antitumor immunity.” Science translational medicine vol. 15,677 (2023): eabo4778. doi:10.1126/scitranslmed.abo4778