Influence of SLCO1B3 haplotype-tag SNPs on docetaxel disposition in Chinese nasopharyngeal cancer patients.

AIMS To completely screen the SLCO1B3 gene in three distinct healthy Asian populations (Chinese, Malay and Indian, n = 168) and investigate the influence of haplotype-tag SNPs (htSNPs) on docetaxel disposition in 50 nasopharyngeal carcinoma patients. METHODS Genomic DNA of individuals was screened for SLCO1B3 polymorphisms by direct sequencing. htSNPs were derived based on the sequence clustering algorithm and profiled in the patients. Population based genetic association analysis was performed using Haplostats package implemented in R and PLINK. RESULTS A strong linkage disequilibrium pattern was detected across a total of 88 polymorphisms and 15-htSNPs were identified. The SLCO1B3 haplotypic region comprising seven htSNPs was found to be significantly associated with docetaxel clearance (P = 0.003). Conditional haplotype analyses revealed that the haplotypic constructs comprising the IVS4+ 76G> A, 699G> A(Met233Ile), IVS12-5676A> G, and * 347_* 348insA polymorphisms were critical determinants of variability in docetaxel disposition [ clearance and area under the plasma concentration-time curve (AUC(0,)): r2 = 29% and 22%, respectively]. Patients harbouring the GAG* 347insA haplotype were significantly associated with a 30% decrease in clearance and a 40% increase in AUC(0,) of docetaxel compared with patients harbouring the reference haplotype, GGA* 347wt (P = 0.025 and 0.018, respectively). In contrast, a 50% higher clearance was observed in patients carrying the GAG* 347wt haplotype compared with those with the reference haplotype (P = 0.002). The functional SLCO1B3 haplotypic constructs included the widely studied Met233Ile variant and * 347_* 348insA located in the putative miR-890 binding site in the 3'-untranslated region which may influence the transport characteristics of SLCO1B3. CONCLUSIONS This study highlights the importance of SLCO1B3 polymorphic variations in influencing docetaxel disposition in nasopharyngeal carcinoma patients.