Specific targeting of point mutations in EGFR L858R-positive lung cancer by CRISPR/Cas9

Area of Science:

• Genetics
• Molecular Biology
• Oncology

Background:

• Cancer cells possess unique genetic mutations, often single nucleotide substitutions, which present therapeutic targets.
• Current targeted therapies face limitations in gene targeting range and acquired resistance.
• Oligonucleotide-based strategies offer a potential solution for specific cancer targeting.

Purpose of the Study:

• To develop and evaluate a CRISPR/Cas9 system for specifically targeting the EGFR L858R point mutation.
• To assess the specificity and efficacy of this strategy in differentiating cancer mutations from wild-type sequences.

Main Methods:

• Utilized CRISPR/Cas9 system with an oligonucleotide guide targeting the EGFR L858R mutation.
• Employed protospacer-adjacent motif (PAM) sequence for precise DNA cleavage differentiation.
• Validated selective genome cleavage using Sanger sequencing and T7 Endonuclease I assay.
• Quantified targeting efficiency via digital PCR and assessed downstream effects on EGFR expression, cell proliferation, and tumor growth in vivo.

Main Results:

• The CRISPR/Cas9 strategy demonstrated high specificity, targeting only L858R mutant cells at the single nucleotide substitution level.
• Selective genome cleavage was confirmed in L858R mutant cells, with wild-type cells remaining unaffected.
• Treated mutant cells exhibited reduced EGFR expression, decreased cell proliferation, and smaller tumor volumes in vivo.
• The approach successfully targeted approximately 37.9% of L858R gene copies in mutant cells.

Conclusions:

• This oligonucleotide-based CRISPR/Cas9 strategy offers a highly specific method for targeting cancer-defining mutations, including single nucleotide substitutions.
• The PAM-dependent cleavage mechanism provides a robust way to differentiate mutant from wild-type alleles.
• This approach holds promise for treating a significant fraction of cancers with specific point mutations, potentially minimizing off-target effects and overcoming resistance.