ERBB2 and breast cancer: This fact, together with the key role of microtubule dynamics in cancer growth, led to the concept that PTXNR-TTZ directly inhibits actin polymerization causing apoptosis in cancer cells. Using the densitometry of Western blot results, we show that HER2 + breast cancer cells treated with PTXNR-TTZ contained a reduction in actin polymerization by ∼60% compared with untreated cells.