ESR1 and breast cancer: For cluster C (Fig. 1g), ESR1 mRNA expression (surrogate for ER status) was significantly positively associated with 15 out of 37 miRNAs, including hsa-miR-29c-5p expression, the hub of cluster C. Altogether, our analysis of miRNA expression in the three mimQTL-miRNA clusters clearly identified distinct signaling pathways and processes associated with different biological and molecular aspects of breast cancer.