Abstract
HER2-positive and triple-negative breast cancers (TNBC) are difficult to treat and associated with poor prognosis. Despite showing initial response, HER2-positive breast cancers often acquire resistance to HER2-targeted therapies, and TNBC lack effective therapies. To overcome these clinical challenges, we evaluated the therapeutic utility of co-targeting TrkA and JAK2/STAT3 pathways in these breast cancer subtypes. Here, we report the novel combination of FDA-approved TrkA inhibitors (Entrectinib or Larotrectinib) and JAK2 inhibitors (Pacritinib or Ruxolitinib) synergistically inhibited in vitro growth of HER2-positive breast cancer cells and TNBC cells. The Entrectinib-Pacritinib combination inhibited the breast cancer stem cell subpopulation, reduced expression of stemness genes, SOX2 and MYC, and induced apoptosis. The Entrectinib-Pacritinib combination suppressed orthotopic growth of HER2-positive Trastuzumab-refractory breast cancer xenografts and basal patient-derived xenograft (PDXs), reduced tumoral SOX2 and MYC, and induced apoptosis in both mouse models. The Entrectinib-Pacritinib combination inhibited overall metastatic burden, and brain and bone metastases of intracardially inoculated TNBC cells without toxicity. Together, our results demonstrate for the first time that co-inhibition of TrkA and JAK2 synergistically suppresses breast cancer growth and metastasis, thereby providing preclinical evidence that supports future clinical evaluations.