Genetic Polymorphism of Cytochrome P450–1B1 and Risk of Breast Cancer

DOI: Published February 2000

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Fig. 1.
Gel electrophoresis after RFLP analysis of the 650-bp CYP1B1 PCR product. Representative genotypes are shown in Lane 1 (homozygous for the Leu allele), Lane 2 (heterozygous for the Leu allele), and Lane 3 (homozygous for the Val allele).

Table 1

Comparison of cases and controls by selected demographics and breast cancer risk factors, Shanghai Breast Cancer Study, 1996–1998

	Cases (n = 186)^a	Controls (n = 200)^a	OR (95% CI)
Demographic factors
Age (yr)	47 (42, 53)^b	46 (41, 55)^b
Education ≥ high school	40.3	43.0	0.9 (0.6–1.3)
Major risk factors
First-degree relative with breast cancer	1.6	2.0	0.8 (0.2–3.6)
Ever diagnosed with breast fibroadenoma	9.7	4.0	2.6 (1.1–6.1)
No regular leisure physical activity	80.1	69.0	1.8 (1.1–2.9)
Waist:hip ratio ≥0.85	21.6	18.5	1.2 (0.7–2.0)
Body mass index ≥25	27.0	22.5	1.3 (0.8–2.0)
Age at menarche ≤12 yr	9.2	7.5	1.2 (0.6–2.6)
Age at menopause ≥50 yr^c	50.0	38.0	1.6 (0.8–3.2)
Age at first live birth ≥30 yr^d	25.6	16.0	1.8 (1.1–3.0)

Table 2

Associations of CYP1B1 genotype with breast cancer risk, Shanghai Breast Cancer Study, 1996–1998

CYP1B1 genotype	No. of cases (n = 186)	No. of controls (n = 200)	Unadjusted OR (95% CI)	Adjusted^a OR (95% CI)
All study participants
Val/Val	37	44	1.0	1.0
Val/Leu	101	127	0.9 (0.6–1.6)	1.0 (0.6–1.7)
Leu/Leu	48	29	2.0 (1.0–3.7)	2.3 (1.2–4.3)
Premenopausal women
Val/Val	26	26	1.0	1.0
Val/Leu	68	78	0.9 (0.5–1.6)	1.0 (0.5–1.9)
Leu/Leu	27	17	1.6 (0.7–3.6)	1.9 (0.8–4.3)
Postmenopausal women
Val/Val	11	18	1.0	1.0
Val/Leu	32	49	1.1 (0.4–2.6)	1.1 (0.4–2.6)
Leu/Leu	21	12	2.9 (1.0–8.0)	3.1 (1.0–9.1)

^a Adjusted for prior history of breast fibroadenoma, physical activity, and age at first pregnancy.

Table 3

Adjusted ORs for potential joint effect of CYP1B1 genotype with selected risk factors, Shanghai Breast Cancer Study, 1996–1998

Risk factors	CYP1B1 Val/Val + Val/Leu			CYP1B1 Leu/Leu
Risk factors		Case/control	OR (95% CI)^a	Case/control	OR (95% CI)^a
Ever diagnosed with breast fibroadenoma
No	123/165	1.0	45/27	2.4 (1.4–4.1)
Yes	15/6	3.2 (1.2–8.6)	3/2	2.1 (0.3–13.2)
Physical activity
High	24/53	1.0	13/9	3.5 (1.3–9.5)
Low	114/118	2.1 (1.2–3.6)	35/20	3.8 (1.8–7.9)
Age at first live birth (by median)^b
≤26 years	59/93	1.0	25/16	2.6 (1.3–5.3)
>26 years	74/72	1.5 (1.0–2.5)	21/11	2.8 (1.3–6.3)