The treatment of two cancer cell lines (the triple-positive breast cancer BT474 and the triple-negative breast cancer MDA-MB-453) that overexpress ErbB2 (receptor tyrosine-protein kinase erbB-2) at different doses of betulinic acid (BA), showed, in a dose-dependent form, an inhibition of cell growth, an increase in cell apoptosis, and a reduction in the expression of specific protein (Sp) transcription factors, with the consequent decrease in ErbB2 expression due to the repression of the YY1 gene regulated by Sp [127,128]. The gene discussed is ERBB2; the disease is triple-negative breast carcinoma.