Hormone dependence in premalignant mammary progression

Area of Science:

• Oncology
• Endocrinology
• Genetics

Background:

• Estrogen receptor (ER) negative breast cancers are linked to poor patient survival.
• The BALB/c p53-null mouse model replicates key features of human breast cancer, with p53 gene deletion increasing tumor risk.

Purpose of the Study:

• To investigate the role of ovarian hormones in the progression of premalignant mammary tissue in a p53-null mouse model.
• To determine if estrogen and progesterone influence tumorigenesis in p53-null mammary epithelium.

Main Methods:

• Utilized the BALB/c p53-null mouse model for mammary gland studies.
• Examined the impact of estrogen and progesterone on normal and premalignant mammary epithelium.
• Investigated the role of the progesterone receptor in hormone-driven tumorigenesis.
• Generated and characterized immortalized premalignant outgrowth lines (PN).

Main Results:

• While both p53-null and wild-type epithelia require ovarian hormones for growth, estrogen and progesterone significantly enhance tumorigenesis in p53-null cells.
• Deletion of the progesterone receptor abolished progesterone's enhancement of tumorigenesis.
• Premalignant outgrowth lines (PN) showed strong dependence on ovarian hormones for growth and tumorigenesis, even when ER positive.
• Hormonal stimulation was a potent promoter of tumorigenesis in p53-null cells, exceeding the effect of a chemical carcinogen.

Conclusions:

• p53-null mammary cells are highly sensitive to ovarian hormones during normal and premalignant stages, leading to a high incidence of ER-negative tumors.
• This p53-null mouse model is suitable for evaluating chemopreventive agents against both ER-negative and ER-positive mammary tumors.