Interplay Between MicroRNAs and Breast Cancer Therapies: Personalized Therapeutic Potential for HER2-Low Breast Cancer

HER2-low breast cancer has been recognized as a heterogenous group of tumors influenced by hormone receptor (HR) expression, giving rise to tumors with either a luminal-like phenotype or features resembling triple-negative breast cancer (TNBC). Despite the development of HER2-targeted therapies, several studies have demonstrated their limited efficacy in patients diagnosed with HER2-low breast cancer. However, recent research has led to the development of antibody-drug conjugates (ADCs), such as trastuzumab emtansine (T-DM1) and trastuzumab deruxtecan (T-DXd), with the latter showing promising results in treating these patients. Despite this breakthrough, the availability of a single effective therapy fails to account for tumor heterogeneity and may contribute to the emergence of therapy resistance, leaving HER2-low patients without treatment options. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at a post-transcriptional level and are capable of modulating key cellular processes. Recent studies have highlighted their potential as therapeutic targets, contributing to the advancement of personalized, patient-center therapies. In this context, the interplay between miRNAs and HER2-targeted therapies, particularly their modulation of common essential genes and signaling pathways, could reshape HER2-low therapy strategies to transform current practices aimed at improving the overall patient outcomes. Therefore, this review aims to elucidate the mechanisms underlying current HER2-targeted therapy and explore a potential crosstalk with miRNAs, ultimately serving as a guide for the development of personalized therapeutic strategies.