To verify if the chemotherapy-sensitizing effect shown by the CAIX inhibitor in melanoma cells is extendable even in other tumour histotypes, we treated MCF7 breast cancer cells with 90 nM (<IC50 dose) of Doxorubicin alone or in combination with 100 μM SLC-0111 for 48 h and observed that the combined therapy significantly increases cell death percentage. The gene discussed is CA9; the disease is neoplasm.