Fig. 1.

Estrogen induced increased growth of ER-negative tumour during mammary involution. From 24 h post-weaning (Inv D1), OVX Inv mice were treated with estradiol valerate (E2V) or vehicle control (Ctrl). Mice were subsequently inoculated with 4 T1-Luc2 cells at the 9th abdominal mammary gland on Inv D2. Age-matched nulliparous (Null) were treated similarly. Mice were euthanized and tumour harvested at day 14 post-tumour cells inoculation. Estrogen treatment induces increased tumour growth in involuting mice but not in nulliparous; Tumour weight at 14 days post-inoculation, Null+Ctrl n = 8, Null+E2V n = 8, Inv + Ctrl n = 11, Inv + E2V n = 13. Data represented as mean ± SEM. An outlier in Inv + Ctrl group was identified using Grubbs’ test and was removed. Statistical significances determined using two-tailed unpaired student’s T-test