Cancer Genetics and Epigenetics, 2025, Vol.13, No.1, 41-49 http://medscipublisher.com/index.php/cge 42 role of this tool in identifying potential therapeutic targets and improving existing treatment methods will also be evaluated, and the development trend of individualized treatment models in the context of the era of precision medicine will be further prospected. The relevant research results are expected to bring about substantial improvements in the clinical diagnosis and treatment effects. 2 Biology of HER2-Positive Breast Cancer 2.1 Molecular basis and functional effects of HER2 gene amplification Her2-driven breast cancer is characterized by the abnormal amplification and overexpression of the HER2 gene. Such cases account for approximately 15%~30% of all breast cancers. Such genetic variations are the core drivers of tumor development, accelerating cell proliferation and inhibiting apoptosis by activating downstream signal networks (Wang et al., 2017). CRISPR gene editing technology has been successfully applied to eliminate the HER2 gene in breast cancer cells and to analyze the resulting molecular cascade reaction. The experimental results showed that the transcriptional characteristics of cells changed significantly after gene inactivation, confirming the key role of HER2 in maintaining the malignant phenotype of cancer cells. Abnormalities of the HER2 gene lead to overexpression of the tyrosine kinase receptor encoded by it, continuously activating important signaling networks such as MAPK/ERK and PI3K/AKT. These pathways not only regulate cell survival and growth, but also enhance the invasive characteristics of HER2-positive tumors. It is notable that CRISPR-mediated gene intervention can block signal transduction by introducing dominant negative mutations, and its mechanism of action is different from traditional therapies such as herceptin, providing the possibility for the innovation of therapeutic strategies (Wang and Sun, 2017; Chen, 2024). 2.2 Clinical manifestations and therapeutic responses of HER2-positive tumors Compared with other types of breast cancer, the HER2-positive subtype usually has stronger invasiveness, a higher recurrence rate and a relatively poorer prognosis. The excessive expression of HER2 protein can significantly shorten the overall survival time of patients and significantly increase the risk of recurrence. Therefore, it is particularly important to develop precise therapeutic intervention methods (Wang et al., 2017). The high malignancy exhibited by this subtype of tumor is mainly attributed to the abnormal activation of the HER2 signaling pathway, which promotes the rapid growth of cancer cells and their spread to other tissues. Although the targeted drugs currently in use have shown some efficacy in the treatment of this type of tumor, drug resistance remains the main problem faced in clinical practice. The application of CRISPR technology can deeply analyze the drug resistance mechanism, provide an effective means for finding key therapeutic targets, and help improve the therapeutic effect (Wang et al., 2017). Through detailed research on the molecular characteristics of HER2-positive tumors, clinical personnel can formulate more precise individualized treatment plans. 2.3 Current situation and challenges of HER2-targeted therapy The current standard treatment regimens include targeted drugs such as trastuzumab (Herceptin) and lapatinib. The former blocks signal transduction and activates immune clearance by binding to the HER2 receptor, while the latter interferes with intracellular signal transduction as a kinase inhibitor. Both significantly improve patient survival (Wang and Sun, 2017). However, such therapies have obvious limitations: The development of drug resistance often leads to the failure of treatment. The drug resistance mechanism involves complex factors such as HER2 receptor variation or activation of alternative pathways. CRISPR technology provides a new approach for drug resistance research at the genetic level and helps identify potential intervention targets (Wang and Sun, 2017; Wang et al., 2017). Breaking through these limitations is expected to develop more durable treatment regimens and improve the clinical outcomes of patients. 3 A Review of CRISPR/Cas9 Technology 3.1 The core mechanism of CRISPR gene editing is associated with breast cancer research CRISPR/Cas9, as a breakthrough genomic regulation tool, can precisely modify specific DNA sequences. In the
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