Tian et al. (2017) recently discovered that VPA and hydroxyurea (a ribonucleotide reductase inhibitor) can limit the proliferation of MCF-7 BC cells synergistically by inhibiting RPA2 and increasing the Rad51-mediated homologous recombination DNA repair pathway. By suppressing the activity of HDAC1 and modifying the methylation state of H19 by induction of the enzyme DNA methyltransferase 1 (DNMT1) expression, Hao et al. (2017) found that VPA may induce death in A549 BC cells and reduce the production of the H19 oncogene. This evidence concerns the gene HDAC1 and breast cancer.