Abstract: Purpose : To probe into the inherent and acquired expression of mdr21 gene on drug2resistance. Methods : Reverse transcription2polymerase chain reaction ( RT2PCR ) assay was used to detect the inherent and acquired expression of mdr21 in the peripheral lymphocytes of 51 patients with malignant tumours. Results : There were 66 % ( 11/ 51) inherent and 9. 8 % (5/ 51) acquired expression in negative groups , and 21 % ( 11/ 51) inherent and 60. 7 % (31/ 51) acquired in low positive groups , and 11. 8 % (6/ 51) inherent and 29 % (15/ 51) acquired expression in high positive groups. Obvious differences were demonstrated among the three groups ( P < 0. 01) . Conclution : The results showed that the mdr21 expression level can reflect the situation of drug2resistance. The method using RT2PCR assay to detect mdr21 expression in the peripheral lymphocytes is convenient for selecting sensitive drugs.

Key words: RT -PCR, drug2resistance, lymphocyte, mdr21