ABCC2 and in situ carcinoma: Cancer cells develop different forms of resistance to CIS, and the most important of these are the repair of damaged DNA via DNA repair systems [8], decreased drug uptake [7], increased reflux by drug transporters of the ABC family such as ABCC2 (MRP2) [9], and increased drug inactivation by sulfhydryl-containing molecules such as metallothioneins [10] and glutathione [11].