Selective segregation of DNA strands persists in long label retaining mammary cells during pregnancy

Breast Cancer Research

Table 2 Percentages of LREC within the receptor positive cell population

Time point	% ER-α-positive LREC population^a	% ER-α-positive total population^a	Ratio of % ER-α-positive LREC to total % ER-α-positive population^a	% PR-positive LREC population^a	% PR-positive total population^a	Ratio of PR-positive LREC to total PR-positive population^a
Non-pregnant	11.4 ± 3.2	16.1 ± 2.45	11.4/16.1 = 0.7081	14.1 ± 4.1	21.9 ± 5.96	14.1/21.9 = 0.6438
Group 1	10.1 ± 2.4	20.6 ± 5.92	10.1/20.6 = 0.4903	19.3 ± 5.9	22.4 ± 4.20	19.3/22.4 = 0.8616
Group 2	12.8 ± 7.9	16.1 ± 7.74	12.8/16.1 = 0.7950	18.0 ± 7.4	19.5 ± 4.23	18.0/19.5 = 0.9424
Group 3	13.7 ± 5.3	20.1 ± 5.64	13.7/20.1 = 0.6816	18.3 ± 10.1	14.3 ± 4.92^*†	18.3/14.3 = 1.2797
Group 4	18.3 ± 8.1	6.62 ± 2.17*	18.3/6.62 = 2.7644	19.3 ± 9.4	6.5 ± 1.47^*†	19.3/6.5 = 2.9692

One thousand cells were counted in mammary gland sections stained for 5BrdU and ER-α or 5BrdU and PR. ([³H]-thymidine and steroid receptors were counted for Group 4). Group 1 tissue was collected at day 3 of pregnancy, Group 2 tissue was collected at day 4 of pregnancy, Group 3 tissue was collected at day 6 of pregnancy, and Group 4 tissue was collected at day 13 of pregnancy after second 5BrdU dose at day 4. Values are expressed as mean ± standard deviation, or as %/% = ratio. ^aDouble positive for 5BrdU and receptor/total receptor positive. *P < 0.05 versus virgin control; ^†P < 0.05 versus group 1. 5BrdU, 5-bromodeoxyuridine; ER, estrogen receptor; LREC, label-retaining epithelial cells; PR, progesterone receptor.

ISSN: 1465-542X