To assure that the effects of CXCR4 attenuation on breast cancer cell migration and invasion was not due to decreased cell viability resulted from the treatment with the CXCR4 blocking mAb or the CXCR4 antagonist; we assessed the effect of CXCR4 blockade on cell viability with an MTT assay. The gene discussed is CXCR4; the disease is breast carcinoma.