Overcoming EGFR T790M-based Tyrosine Kinase Inhibitor Resistance with an Allele-specific DNAzyme

Area of Science:

• Molecular Biology
• Genetics
• Oncology

Background:

• Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are standard treatments for non-small-cell lung cancer (NSCLC) with activating EGFR mutations.
• Acquired resistance to EGFR-TKIs, often driven by the T790M mutation, limits long-term patient survival.
• Targeting the T790M mutation is crucial for overcoming therapeutic resistance in NSCLC.

Purpose of the Study:

• To develop an allele-specific DNAzyme (DzT) capable of selectively silencing EGFR T790M mutant messenger RNA.
• To evaluate the efficacy of DzT, and its modified form (cDzT), in inhibiting T790M-mutant NSCLC cells.
• To assess the synergistic potential of cDzT in combination with a second-generation EGFR-TKI.

Main Methods:

• Design and synthesis of an allele-specific DNAzyme (DzT) targeting EGFR T790M mRNA.
• Modification of DzT with a cholesterol-triethylene glycol group (cDzT) to enhance efficacy.
• In vitro assessment of DzT and cDzT on NSCLC cell lines harboring T790M mutations.
• In vivo evaluation of combined cDzT and BIBW-2992 treatment in xenograft tumor models.

Main Results:

• DzT demonstrated allele-specific silencing of EGFR T790M mRNA and downstream signaling, inducing apoptosis in T790M-positive NSCLC cells.
• Cholesterol modification (cDzT) significantly improved efficacy, increasing growth inhibition from 46% to 79% in H1975(TM/LR) cells.
• Combined treatment with cDzT and BIBW-2992 exhibited synergistic effects, suppressing tumor growth in vivo.

Conclusions:

• The allele-specific DNAzyme DzT is a potential therapeutic agent for overcoming EGFR T790M-mediated TKI resistance in NSCLC.
• cDzT enhances the therapeutic efficacy of allele-specific gene silencing for NSCLC.
• Combination therapy with cDzT and EGFR-TKIs represents a promising strategy for managing resistant NSCLC.