Current melanoma treatments can be toxic and become ineffective, especially when the cancer has spread. Salmonella therapy using shRNA technology bypasses many of the complications associated with standard treatments while directly targeting tumors. The treatment relies on the natural affinity of Salmonella for hypoxic regions of tumor combined with the specificity of shRNA against tumor-promoting factors, such as the immunosuppressive molecule indoleamine 2,3-dioxygenase (IDO). We found that using an attenuated Salmonella strain ,YS1646, carrying an shRNA plasmid against IDO (shIDO-ST), could control the growth of subcutaneous B16F10 melanoma. We wanted to repeat this process using pEQ-shIDO, which uses a different shRNA sequence against IDO, to rule out the possibility that the effect was caused by off targets. We found that pEQ-shIDO also caused IDO knockdown by western blot analysis. We then transformed the plasmid into YS1646 (pEQ-ST). If we observe identical control of B16F10 by pEQ-ST, this would allow us to conclude that the original shIDO-ST led to decreased tumor size by specifically interfering with IDO expression.