Interaction index (Ix) based on isobologram curve for MCF-7, SKBR3 and MCF-7/HER2 breast cancer cells with cerulenin combined with rapamycin treatment showed the combination treatment could produce synergetic cytotoxicity.

<p>In MCF-7/HER2 cells, the IC50 was 1.85 and the Ix was 0.4888. In MCF-7 cells, the IC50 was 3.06 and the Ix was 0.6389. In SKBR3 cells, the IC50 was 2.25 and the Ix was 0.5451.