Table 2. Allele frequencies and in vitro effects of UGT1A variants examined in pharmacogenetic studies of anticancer drugs.

UGT	Expression	UGT alleles	Nucleotide change (amino acid change)	In vitro effect	Frequency
UGT1A1	Hepatic	UGT1A1*1		Normal activity	61–72% in Caucasians, 45–52% in black populations, 90–98% in Japanese populations, 87–93% in Koreans and 84% in Chinese populations [9,56]
		UGT1A1*6	211G>A(G71R) [223;	Reduced activity [18,57]	0–1% in Caucasians, 0% in black populations, 13–18% in Japanese populations, 21–24% in Koreans and 23% in Chinese populations [9,56,67]
		UGT1A1*27	686C>A (P229Q) [223	Reduced activity [18]	0% in Caucasians and black populations and 1–4% in Asians [23,71]
		UGT1A1*28	A(TA)6TAA>A(TA)7TAA [28]	Reduced activity [16,28,224]	29–39% in Caucasians, 35–45% in black populations, 9–13% in Japanese populations, 7–13% in Koreans and 16% in Chinese populations [9,56]
		UGT1A1*60	−3279T>G [225]	Reduced activity [30,71]	44–55% in Caucasians, 85% in African–Americans, 17–26% in Japanese populations, 24–33% in Koreans and 30% in Chinese populations [30,56]
		UGT1A1*93	−3156G>A [225]	Reduced activity [30]	30–31% in Caucasians, 29% in African–Americans and 10% in Asians [30,68]
UGT1A4	Hepatic	UGT1A4*1a		Normal activity
		UGT1A4*2	70C>A (P24T) [186]	Substrate-dependent effect [186,226]	8% in Caucasians [186]
		UGT1A4*3b	142T>G (L48V) [186]	Decreased or no activity [186]	9% in Caucasians and 13% in Japanese populations [186,227]
UGT1A7	Extrahepatic	UGT1A7*1a		High activity	34–42% in Caucasians, 38% in African–Americans and 59% in Japanese populations [9]
		UGT1A7*2	387T>G/391C>A/392G>A (N129K/R131K) [23]	High activity [18,23]	24–34% in Caucasians, 39% in African–Americans, 15% in Japanese populations and 27% in Taiwanese Chinese populations [9,77]
		UGT1A7*3	387T>G/391C>A/392G>A/622T>C (N129K/R131K/W208R) [23]	Low activity [18,23]	23–36% in Caucasians, 23% in African–Americans, 26% in Japanese populations and 15% in Taiwanese Chinese populations [9,77]
		UGT1A7*4	622T>C (W208R) [23]	Low activity [18,23]	1–2% in Caucasians, 1% in black populations, 0% in Japanese populations and 0% in Taiwanese Chinese populations [9,77]
UGT1A8	Extrahepatic	UGT1A8*1a		Normal activity	55% in unknown population [228]
		UGT1A8*2	UGT1A8*2 (518G>C, A173G) [228]	Similar activity to UGT1A8*1a [228]	15% in unknown population [228]
		UGT1A8*3	UGT1A8*3 (830G>A, C277Y) [228,229]	Severely reduced activity [228,229]	2% in unknown population [228]
UGT1A9	Hepatic	UGT1A9*1a
		UGT1A9*1b	−118(dT)9>10 [72]	Luciferase activity increased in one study [72], but another study [74] did not find a significant change in luciferase activity or an association with hepatic UGT1A9 protein content	36–41% in Caucasians, 44% in black populations and 51–60% in Asians [68,72,75,230]
		I399C>T	I399C>T [73]	Increased protein expression and activity in one study [73]. No association with gene expression and activity in another study [75]	38–49% in Caucasians, 42% in Africans and 64% in Japanese populations [73,75,83]
UGT1A10	Extrahepatic	UGT1A10*1a		Normal activity
		UGT1A10*2a	415G>A (E139K) [231]		0% in Caucasians, 3–5% in black populations and 0% in Asians [231]
UGT2B7	Hepatic	UGT2B7*1a			46–51% in Caucasians and 73% in Asian–Americans and Japanese populations [9]
		UGT2B7*2a	802C>T (H268Y) [232]	No change in substrate activity for most substrates [148,232-234], increased activity for very few substrates [233]	49–54% in Caucasians and 27% in Asian–Americans and Japanese populations [9]
		−161T>C	−161T>C (relative to the ATG) [151]	Decreased activity [151]	49% in Caucasians and 69% in African–Americans [151]
UGT2B17	Hepatic	UGT2B17*1			68–69% in Caucasians and 79% in African–Americans [235,240]
		UGT2B17*2	Deletion of a 150-kbp region spanning the UGT2B17 gene [235,236]	Reduced activity in the homozygous state [237-241]	19–33% in Caucasians, 21% in African–Americans, 22% in Yorubans and 84% in Japanese populations and Chinese populations [235,239,240,242,243]

UGT: Uridine 5′-diphosphoglucuronosyltransferase.