PPP4R4 and breast cancer: The location of the mutated genes on 23 pairs of chromosomes and the prevalence of CNVs on HRRGs are shown in Fig. 1C. HRRG expression levels differed between tumor and normal samples, as shown in Fig. 1D. Some HRRGs, such as HFM1 and PPP4R4, were higher expressed significantly in tumors, while some genes, such as EME2 and MUS81, were lower expressed in tumors, which reminded us that BC may be triggered and progressed by differences in HRRG expression.