Irrespective of the position taken, the consensus is that more basic research needs to be performed to address progesterone's fundamental role in mammary development and tumorigenesis.
These results support our thesis that compensatory growth induced during an allometric growth phase improves mammary development and energy and protein metabolic status of dairy heifers.
Here, we discuss the influence of the GH IGF-I axis in normal mammary development and homeostasis, its putative role in breast tumoriGH IGF-Iaxisins inormaltions with estrogen signalling.
MMTV-Wnt1 and MMTV-ΔN89β-catenin induce precocious mammary development and adenocarcinoma formation [13], [17].
Hh pathway repression is essential for embryonic mammary development and repression remains critical to homeostasis in the postnatal gland [37].
Multiple lines of evidence demonstrate roles for Wnt/β-catenin signaling in mammary development and breast cancer [4], [5].
We have previously shown that Lrp5 is required for ductal stem cell activity and that loss of Lrp5 delays normal mammary development and Wnt1-induced tumorigenesis.
Pathway activation distorts mammary development, and is found in both epithelial and stromal compartments of human breast cancers [37], [43] [46].
Mice expressing Wnt inhibitors, or deficient in Lef-1, show defective embryonic mammary development, and loss of the Wnt coreceptor, LRP5/6, impairs postnatal development [6] [9].
Based on previous reports, we predicted that overexpression of Id1 in the luminal epithelial cells of the mammary gland would dramatically alter mammary development and pregnancy-related maturation.
We have previously shown that Id1 cooperates with oncogenic Ras in mammary tumourigenesis and metastasis in vivo [16], but the role for Id1 overexpression alone in mammary development and neoplasia has not been investigated.
