Genotype-phenotype relationships in studies of a polymorphism in NAD(P)H :quinone oxidoreductase 1

The NAD(P)H:quinone oxidoreductase 1 (NQO1) genotype-phenotype relationship was examined in individuals with a polymorphism in NQO1, The polymorphism comprises a C to T base change at position 609 of the human NQO1 cDNA (C609 T) and codes for a proline to serine substitution in the amino acid structu re of the NQO1 protein. Genotyping was performed by polymerase chain reacti on-restriction fragment length polymorphism analysis of genomic DNA. Phenot yping was performed using enzyme activity assays and/or immunoblotting of h uman tumor cell lines and of saliva and bone marrow samples from healthy do nors. Phenotyping of uninvolved lung and lung tumors from archived biopsy m aterial was performed by immunohistochemistry. NQO1 activity and protein co uld be detected in wild-type (C/C) human tumor cells (HT-29) under conditio ns where NQO1 protein could not be detected in cells (BE) homozygous for th e C609T change (T/T). Trace levels of NQO1 protein could be detected in BE cells; however, when immunoblots were subjected to chemiluminescence detect ion for prolonged periods. In saliva samples from 11 individuals carrying t he homozygous C609T change (T/T), no NQO1 protein could be detected even af ter prolonged chemiluminescence detection. The amount of NQO1 protein prese nt in saliva was quantified and found to be significantly less in heterozyg ous individuals (C/T) than in wild-type individuals (C/C), In bone marrow s tromal cultures, both NQO1 activity and protein could be detected in hetero zygotes (C/T) and in wild-type (C/C) samples. In a bone marrow stromal cult ure from an individual genotyped as T/T at position 609, no NQO1 protein or activity could be detected. NQO1 is elevated in non-small cell lung cancer s and could be readily observed as intense immunostaining throughout lung a denocarcinomas genotyped as C/C but no immunostaining could be detected in adenocarcinomas genotyped as T/T at position 609. NQO1 is expressed in norm al human lung but is localized to respiratory epithelium and to vascular en dothelium. In normal lung tissue from individuals genotyped as T/T, no or f aint immunostaining for NQO1 could be detected in either respiratory epithe lium or vascular endothelium. These results demonstrate that tissues from i ndividuals homozygous for the C609T change have no detectable or, at best, only trace amounts of NQO1 protein and are devoid of NQO1 activity. Pharmac ogenetics 9:113-121 (C) 1999 Lippincott Williams & Wilkins.