We compared determined IC50 values for breast and prostate cancers and we observed that for those cancer cell lines that overexpress EGFR (MDA MB 231, SKBR3, LNCaP and PC-3 (Matusewicz and Ligas, [24])) IC50 values for simvastatin were lower than 10 μM in comparison to cells without or with low EGFR expression (MCF7 and BT474) for which IC50 values were 50 μM or more. The gene discussed is EGFR; the disease is prostate cancer.