Treatment with anti-CSPG4-SB-Saporin for 4 days decreased tumor cell viability in CSPG4-high A375 and A2058 melanoma cell lines, while it had low toxic effects on the CSPG4-low SBCL-2 melanoma and SKBR-3 breast cancer cells. The gene discussed is CSPG4; the disease is breast carcinoma.