In contrast, in estrogen receptor-negative mammary tumors in MMTV-polyoma middle T (PyMT) mouse model, the use of SAHA together with triterpenoid significantly delays the initial development of tumors partially due to decreased macrophage infiltration into the mammary gland 172, indicating that HDAC inhibition contributes to tumor repression in PyMT mouse model. Here, HDAC9 is linked to neoplasm.