Genetic loss or systemic delivery of ASOs targeting MALAT1 in the mouse mammary tumor virus-PyMT (MMTV) carcinoma model resulted in slower tumor growth, significant differentiation into cystic tumors and metastasis reduction; furthermore, MALAT1 loss decreased branching morphogenesis in MMTV-PyMT and Her2/neu-amplified tumor organoids, increased cell adhesion, and reduced migration. The gene discussed is ERBB2; the disease is neoplasm.