The production of estrogen from androgen via the estrogen biosynthesis path
way is catalyzed by aromatase P450 (cyp19), We have assessed the frequency
of allelic variants of the CYP19 intron 4 [TTTA](n) repeat in 327 breast ca
ncer cases and 253 controls from southern England. Previous studies have su
ggested that the [TTTA](10) repeat and [TTTA](12) repeat variants represent
low penetrance breast cancer susceptibility alleles, Compared with control
s our breast cancer cases had a statistically significant positive associat
ion with the [TTTA](10) allele (1.5 versus 0.2%, P = 0.028) and the [TTTA](
8) allele (13.5 versus 8.7%, P = 0.012). The frequency of the [TTTA](12) al
lele was not significantly elevated in our study group compared with contro
ls (2.3 versus 2.2%, P = 1.00), The CYP19 intron 4 [TTTA](n) repeat is unli
kely to have a functional effect on aromatase activity and it is more likel
y that the [TTTA](8) and [TTTA](10) variants are in linkage disequilibrium
with other functional CYP19 variants.