ERBB2 and breast cancer: When comparing MaTAR25 ASO-treated cells to mock or scrambled ASO (scASO)-treated 4T1 control cells after 72 h, we found a significant decrease in cell viability using cell counting assays (−45% for ASO1 and −38% for ASO2) (Supplementary Fig. 1f), and similar reduction phenotypes were also observed in cNeu (MMTV-Neu-NDL) cells treated with MaTAR25 ASOs (−50% for ASO1 and −41% for ASO2) (Supplementary Fig. 1g), consistent with our KO studies indicating that MaTAR25 has a role in mammary cancer cell proliferation.