Application of Echo Revolve Microscope in the Study of Acquired Resistance Mechanism in Targeted Therapy of Non-Small Cell Lung Cancer
During targeted therapy for non-small cell lung cancer (NSCLC), acquired resistance may occur. Although many drivers of acquired resistance have been discovered, the underlying molecular mechanisms that lead to tumor evolution during treatment are not fully understood, and it is unclear to what extent treatment actively promotes tumor development by promoting mutation processes. Therefore, scientists such as Hideko Isozaki and Ammal Abbasi from Massachusetts General Hospital in the United States published an article titled "APOBEC3A drives acquired resistance to targeted therapies in non-small cell lung cancer". The authors studied whether there are specific mutation mechanisms driving the genomic evolution of lung cancer during targeted therapy for NSCLC. The results show that targeted therapy-induced cytidine deaminase APOBEC3A (A3A) mutations may promote the development of acquired resistance in non-small cell lung cancer.
The authors found in their study that clinically used targeted therapies for lung cancer induce the expression of A3A, leading to persistent mutations in drug-resistant cancer cells. Induced A3A promotes the formation of double-strand DNA breaks (DSBs) in drug-treated cells, leading to chromosomal instability during the evolution of drug-resistant cells, such as copy number changes and structural variations. Preventing therapy-induced A3A mutations by gene deletion or RNAi-mediated inhibition can delay the emergence of resistance. Therefore, targeted therapy-induced A3A mutations may promote the development of acquired resistance in non-small cell lung cancer. Inhibiting the expression or enzyme activity of A3A may be a potential therapeutic strategy to prevent or delay the development of acquired resistance in lung cancer targeted therapy. Therefore, targeted therapy-induced A3A mutations may promote the development of acquired resistance in non-small cell lung cancer. Inhibiting the expression or enzyme activity of A3A may be a potential therapeutic strategy to prevent or delay the development of acquired resistance in lung cancer targeted therapy.
When double-strand DNA damage is formed, the Ser139 site of H2AX is rapidly phosphorylated to form γH2AX, which can be used as a marker for double-strand repair. In the article, the authors used immunofluorescence technology and ECHO Revolve inverted fluorescence microscope for immunofluorescence observation. After 2 weeks of osimertinib treatment, we observed an increase in the Ser139 phosphorylation level of the histone variant H2AX in PC9 cells (Figure 1), indicating that TKI-induced A3A mutations lead to genomic instability and promote the evolution of drug-resistant clones. Mapping γH2AX to the cell cycle distribution of TKI-treated PC9 cells showed that γH2AX was most prominently localized to a subpopulation of cells that resumed cell division and were in the G2 phase (Figure 2). Therefore, TKI treatment induces A3A-catalyzed genomic damage in proliferating drug-resistant cells.
Figure 1: PC9 cells were treated with 1 μM osimertinib for 0 or 14 days and stained with γH2AX to quantify DNA damage. NT, no treatment; Scale bar = 70 μm.
▲Figure 2: The left picture shows PC9 cells treated with 1 μM osimertinib for 14 days and stained with EdU/DAPI to distinguish the cell cycle, representing G1, S, and G2 cells; scale bar = 10 μm. The right picture is a scatter plot of the EdU cell cycle assay, with γH2AX used to quantify DNA damage. NT: untreated.
The authors' findings suggest that the acquisition of APOBEC mutation signatures after TKI treatment may indicate the evolutionary path of resistant clones and provide a new mechanism by which targeted therapy may inadvertently increase adaptive mutations in cancer cells during treatment. Therefore, blocking the expression or enzymatic activity of A3A may be a potential therapeutic strategy to prevent or delay acquired resistance in targeted lung cancer therapy.
Reference: H Isozaki, Abbasi A, Nikpour N, et al. APOBEC3A drives acquired resistance to targeted therapies in non-small cell lung cancer. 2021.
DOI:10.1101/2021.01.20.426852
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