However, subsequent work showed that some drug-resistant P. falciparum strains do not encode mutated or overexpressed pfmdr [40, 41] , and that other genetic events must therefore be important. In parallel once again to tumor drug resistance, at the same time an increasing importance of the overexpression of other genes (e.g., ion transporter and mutant pro-and antiapoptotic genes) was recognized for MDR tumor cells [42, 43] . Similar to P. falciparum multidrug resistance (PfMDR) protein versus malarial multidrug resistance (see later), the precise role of HsMDR1 protein in tumor multidrug resistance has been questioned for some time as pathology data have not correlated HsMDR1 overexpression with clinically relevant tumor multidrug resistance as strongly as was initially suspected [36, 43, 44] .