Also known as -164A>C or -163C>A, is a SNP encoding the CYP1A2*1F allele of the CYP1A2 gene.

AA = CYP1A2*1F = Fast Metabolizer

CC, AC = CYP1A2*1C = Slow Metabolizer

The C allele is considered the wild-type, even though it is the rarer allele in most populations.

The CYP1A2 gene encodes a member of the cytochrome p450 family of proteins, which metabolize nutrients and drugs. One well known substrate of CYP1A2 is caffeine. The same amount of caffeine will therefore tend to have more stimulating effect on CYP1A2 slow metabolizers than on CYP1A2 fast metabolizers.

The minor C allele:

  • Slow metabolizers (A;C) (C;C)

The Major A allele:

  • Fast metabolizer (A;A) 

Drinkers of 3 or more cups of coffee per day tended to have lower breast volume (smaller breasts), but only if they had at least one C allele (p(interaction)=0.02), which was said to be consistent with reports that coffee protects only C-allele carriers against breast cancer [R].

Women (about 1/2 of the total study) who drank 2 or more cups of coffee per day tended to have a later age at diagnosis of breast cancer compared with low coffee consumption (59.8 versus 52.6 years, p = 0.0004). These patients were also more likely to have ER- tumors than patients with low consumption (14.7% versus 0%, p = 0.018) (A;A).  Coffee consumption had no associations in carriers of the (C) allele [R].

Women with at least one (C) allele who consumed coffee had a 64% reduction in breast cancer risk, compared with women who never consumed coffee (odds ratio 0.36, CI: 0.18-0.73). No such protective effect was seen in (A;A) women.[R]

A study of 2,000 Costa Ricans who survived a first heart attack observed a general trend between coffee consumption and increased risk among carriers of (C) alleles, i.e. more coffee led to increased nonfatal heart attack risk. No association was seen for (A;A) individuals.[R]

Association of genotypes with breast cancer risk was evaluated using multivariate logistic regression, which suggested an altered risk for the following SNP:  homozygote carriers of rs762551 [CYP1A2, OR = 2.75 (1.47-5.14)]. In addition, a stratified analysis by menopausal status indicated that the association of the CYP1A2 (rs762551) and CYP17 (rs743572) polymorphisms with breast cancer risk were mainly evident in premenopausal.These findings suggest that CYP1A2 and CYP17 polymorphisms may play an important role in estrogen metabolism and modify individual susceptibility to breast cancer in Thai women.[R]


Parent Gene: CYP1A2

Importance: 5
Less common allele: C = 37%
More common allele: A = 63%
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