PMPCA and breast cancer: Two compounds—Cpd3 and Cpd30—induced apoptosis of the three breast cancer cell lines with constitutive Stat3 activity—MDA-MB-468, MDA-MB-231 and MDA-MB-435 (Figure 5A, B and C)—with EC50 values ranging from 2.3 to 26.9 μM and from 6.4 to 92.2 μM, respectively (Table 3).