Connecting the Missing Dots: ncRNAs as Critical Regulators of Therapeutic Susceptibility in Breast Cancer

SIMPLE SUMMARY: Despite considerable improvements in diagnosis and treatment, drug resistance remains the main cause of death in BC. Multiple lines of evidence demonstrated that ncRNAs play a vital role in BC resistance. Here, we summarized the molecular mechanisms by which miRNAs and lncRNAs may impact the therapeutic response in BC, highlighting that these molecules can be further exploited as predictive biomarkers and therapeutic targets. By merging data from various studies, we concluded that several ncRNAs, such as miR-221, miR-222, miR-451, UCA1, and GAS5 are strong candidates for pharmacological interventions since they are involved in resistance to all forms of therapies in BC. Therefore, we believe that our review provides an important reservoir of molecules that may translate into clinically useful biomarkers, laying the ground for the adoption of ncRNAs within mainstream routine oncology clinical practice. ABSTRACT: Whether acquired or de novo, drug resistance remains a significant hurdle in achieving therapeutic success in breast cancer (BC). Thus, there is an urge to find reliable biomarkers that will help in predicting the therapeutic response. Stable and easily accessible molecules such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are regarded as valuable prognostic biomarkers and therapeutic targets since they act as crucial regulators of the various mechanisms involved in BC drug resistance. Here, we reviewed the current literature on ncRNAs as mediators of resistance to systemic therapies in BC. Interestingly, upon integrating data results from individual studies, we concluded that miR-221, miR-222, miR-451, Urothelial Carcinoma Associated 1 (UCA1), and Growth arrest-specific 5 (GAS5) are strong candidates as prognostic biomarkers and therapeutic targets since they are regulating multiple drug resistance phenotypes in BC. However, further research around their clinical implications is needed to validate and integrate them into therapeutic applications. Therefore, we believe that our review may provide relevant evidence for the selection of novel therapeutic targets and prognostic biomarkers for BC and will serve as a foundation for future translational research in the field.