Predictive pharmacogenetic biomarkers for breast cancer recurrence prevention by simvastatin

Figures & data

Figure 1. Transporter proteins and metabolic enzymes involved in the disposition of simvastatin. Administered simvastatin lactone (SVL) is hydrolyzed in the gut to simvastatin acid (SVA). SVA enters hepatocytes via OATP1B1 (encoded by the polymorphic SLCO1B1 gene). SVA is oxidized by CYP3A4 and CYP3A5 (encoded by eponymous polymorphic genes) into oxidized metabolites (SVOx), which are eliminated. In addition, the P-glycoprotein transporter (P-gp; encoded by the polymorphic ABCB1 gene) drives efflux of SVA from hepatocytes into the bile.

Table 1. Summary of gene variant characteristics and their distribution among controls.

Gene/ RefSNP	Assay	MAF observed (expected)^a	Genotype distribution among controls observed (expected)^b			Hardy-Weinberg
			wt/wt	wt/var	var/var	p Value^c
ABCB1 rs2032582^d	TaqMan	0.43	46	64	27	.60
	C_11711720C_30	(0.42)	(44.4)	(67.2)	(25.4)
	C_11711720D_40
CYP3A4 rs35599367	TaqMan	0.06	130	15	1	.39
	C_59013445_10	(0.03)	(129.5)	(16.0)	(0.5)
CYP3A5 rs776746	TaqMan	0.07	120	20	0	1
	C_26201809_30	(0.04)	(120.7)	(18.6)	(0.7)
SLCO1B1 rs4149056	TaqMan	0.15	105	41	1	.31
	C_30633906_10	(0.13)	(107.1)	(36.7)	(3.1)

MAF: minor allele frequency.

^a Expected minor allele frequencies in the European population were ascertained from the dbSNP database maintained by the U.S. National Library of Medicine (https://www.ncbi.nlm.nih.gov/snp/).

^b Expected genotype frequencies under Hardy-Weinberg equilibrium.

^c Haldane’s exact test for Hardy-Weinberg equilibrium.

^d For this tri-allelic variant, the “A” allele was very rare, and therefore combined with the “T” variant in the genotype categories.

Table 2. Characteristics of breast cancer recurrence cases and matched controls. Denmark, 2004–2010.

	Recurrences		Controls
Characteristic	n = 151 (%)		n = 147 (%)
Age at diagnosis
<50	7	(4.6)	11	(7.5)
50–59	41	(27)	38	(26)
60–69	59	(39)	69	(47)
70–79	38	(25)	25	(17)
≥80	6	(4.0)	4	(2.7)
Menopausal status
pre-menopausal	14	(9.3)	17	(12)
post-menopausal	137	(91)	130	(88)
Stage of primary breast cancer
I	37	(25)	40	(27)
II	84	(56)	74	(50)
III	30	(20)	33	(22)
Type of breast cancer surgery
mastectomy	76	(50)	68	(46)
lumpectomy	75	(50)	79	(54)
Estrogen receptor status and receipt of endocrine therapy
ER–/ET–	19	(13)	19	(13)
ER+/ET–	24	(16)	27	(18)
ER+/ET+	108	(72)	101	(69)
Chemotherapy
received	31	(21)	40	(27)
did not receive	120	(80)	107	(73)
Duration of simvastatin exposure
≤1 year	74	(49)	77	(52)
2–3 years	49	(33)	46	(31)
4–5 years	20	(13)	16	(11)
≥6 years	8	(5.3)	8	(5.4)

ER: estrogen receptor; ET: endocrine therapy.

Table 3. Associations between variants in simvastatin transport and metabolism genes and breast cancer recurrence among simvastatin-exposed breast cancer patients. Denmark, 2004–2010.

Genes and genotypes	Cases/ controls^a	Conditional OR^b (95% CI)		Adjusted OR^c (95% CI)
ABCB1 rs2032582
0 variant alleles	48/46	1	ref	1	ref
1 variant allele	68/64	0.97	(0.53, 1.8)	0.97	(0.54, 1.7)
2 variant alleles	21/27	0.84	(0.41, 1.7)	0.69	(0.31, 1.5)
CYP3A4 rs35599367
0 variant alleles	135/130	1	ref	1	ref
≥1 variant allele	12/16	0.83	(0.36, 1.9)	0.68	(0.28, 1.6)
CYP3A5  rs776746
0 variant alleles	130/120	1	ref	1	ref
≥1 variant allele	13/20	0.43	(0.16, 1.1)	0.75	(0.33, 1.7)
CYP3A4/5
0 variant alleles	116/108	1	ref	1	ref
≥1 variant allele	25/34	0.63	(0.33, 1.2)	0.72	(0.38, 1.4)
SLCO1B1 rs4149056
0 variant alleles	113/105	1	ref	1	ref
≥1 variant allele	35/42	0.79	(0.46, 1.4)	0.80	(0.45, 1.4)

^a Case and control frequencies sum to less than the totals from Table 2 due to genotyping assay failure in a small number of samples.

^b Accounting for matched factors (UICC stage, ER/ET status, calendar period of breast cancer diagnosis, and duration of simvastatin exposure during the recurrence risk period).

^c Adjusted for the matching factors and for age at diagnosis, receipt of chemotherapy, and type of breast cancer surgery.

Figure 2. Associations between variants in simvastatin transport and metabolism genes and breast cancer recurrence among simvastatin-exposed breast cancer patients, stratified by duration of simvastatin use after breast cancer diagnosis. Denmark, 2004–2010.

ABCB1: ORs compare ‘2 variant alleles’ group with ‘no variant alleles’ group.

CYP3A4/5 and SLCO1B1: ORs compare ‘≥1 variant allele’ group with ‘no variant alleles’ group.