PGP and osteosarcoma: Cytostatic pretreatment can also be correlated with the presence of mdr1-mRNA and p-gp in the SK-MEL-3 tumor because the incidence of mdr1 expression has been observed to increase following previous chemotherapy, for example, in acute myeloic leucemia, plasmocytoma, or osteosarcoma, and adversely influences adversely remission rate and prognosis of relapsed tumors [21].