Functional activity of multidrug resistance (MDR) markers (total activity of
ABC-transporters,
P-glycoprotein (Pgp) and
multidrug resistance-associated protein (MRP) activities) in human
colon adenocarcinoma and normal mucosa was examined. Functional activity of
ABC-transporters was revealed in all colon
tumors and in 70% of normal mucosa samples investigated. Expression of Pgp and MRP functional activity was determined in about 50% and 70% of colon
tumors respectively. Pgp+MRP+ phenotype was determined in 36% of normal mucosa and
adenocarcinoma samples. Expression of Pgp+MRP- phenotype was practically the same in normal mucosa and
tumors (in 10 and 18% of samples respectively). Pgp-MRP+ phenotype was revealed two times more often in
tumors than in mucosa--in 36 and 18% respectively. On the contrary, Pgp-MRP- phenotype was detected more rarely in
tumors than in mucosa (in 10 and 36% of samples respectively). Transporters different from Pgp and MRP were also determined in some
tumors and normal mucosa. At the patients with expression of Pgp function in normal mucosa the activity of the transporter was revealed in 25% of
tumor samples only. On the contrary, at the patients with expression of MRP function in normal mucosa the activity of the transporter was revealed in 70% of
tumor samples. At the patients with no expression of Pgp or MRP activity in normal mucosa the function of the transporters in
tumors was determined in 60% and 70% of samples respectively. It is concluded that functional activity of various
ABC-transporters (Pgp, MRP and other different from Pgp and MRP) is expressed in human
colon adenocarcinoma; expression of
ABC-transporters functional activity in normal mucosa does not predict MDR phenotype of the
tumor.