New edition of Science News reports finding that in mice, so called HOX genes
determine normal development of mammary tissue during pregnancy - 3 genes
involved - in mice with all 3 genes mutated, researchers found that mice had
inadequate cell proliferation to form normal ductal tissue ( Feng Chen & MR
Capecchi Jan 19 Proc. Nat. Acad. Sciences).  The note infers that in these
mutated mice, the pre-pregnant mammary tissue appeared normal.

Also note on pesticides - Danish study of 18 pesticides known to be stored in
fat tissue - correlated higher serum levels of 2 of these pesticides with
increase in breast cancer.  The note states the researchers accounted for
"well-known" breast-cancer risks such as pregnancy, but doesn't mention
lactation history.  Would be interesting to know if those women who had nursed
the more extensively had the lower serum levels of these chemicals ( would
lose some chemical load through breastmilk).

Researcher found small increase in risk with beta-hexachlorocyclohexane and a
doubling of risk with highest vs lowest levels of dieldrin, a US-banned
environmental estrogen or estrogen-mimic. (Lancet Dec 5, 1998)

Of course I wonder if these HOX breast genes' actions can be modified
(suppressed, stimulated, etc.) by hormone-like chemicals.

Sheila Humphrey
BSc RN IBCLC
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