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Loss of function of GATA3 induces basal-like mammary tumors.

ABSTRACT: Purpose: GATA3 is a transcription factor essential for mammary luminal epithelial cell differentiation. Expression of GATA3 is absent or significantly reduced in basal-like breast cancers. Gata3 loss-of-function impairs cell proliferation, making it difficult to investigate the role of GATA3 deficiency in vivo. We previously demonstrated that CDK inhibitor p18^INK4c (p18) is a downstream target of GATA3 and restrains mammary epithelial cell proliferation and tumorigenesis. Whether and how loss-of-function of GATA3 results in basal-like breast cancers remains elusive. Methods: We generated mutant mouse strains with heterozygous germline deletion of Gata3 in p18 deficient backgrounds and developed a Gata3 depleted mammary tumor model system to determine the role of Gata3 loss in controlling cell proliferation and aberrant differentiation in mammary tumor development and progression. Results: Haploid loss of Gata3 reduced mammary epithelial cell proliferation with induction of p18, impaired luminal differentiation, and promoted basal differentiation in mammary glands. p18 deficiency induced luminal type mammary tumors and rescued the proliferative defect caused by haploid loss of Gata3. Haploid loss of Gata3 accelerated p18 deficient mammary tumor development and changed the properties of these tumors, resulting in their malignant and luminal-to-basal transformation. Expression of Gata3 negatively correlated with basal differentiation markers in MMTV-PyMT mammary tumor cells. Depletion of Gata3 in luminal tumor cells also reduced cell proliferation with induction of p18 and promoted basal differentiation. We confirmed that expression of GATA3 and basal markers are inversely correlated in human basal-like breast cancers. Conclusions: This study provides the first genetic evidence demonstrating that loss-of-function of GATA3 directly induces basal-like breast cancer. Our finding suggests that basal-like breast cancer may also originate from luminal type cancer.

SUBMITTER: Bai F

PROVIDER: S-EPMC8692904 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Previously, we have shown that the intraductal (i.duc) administration of pegylated liposomal doxorubicin (PLD) to Her2/neu transgenic mice is associated with mammary tumor regression and prevention. Exploring the mechanism underlying the protection afforded by PLD, we studied: the effects of i.duc PLD-treatment with a subsequent pregnancy on outgrowth of tumors in Her2/neu mice; whether the i.duc PLD antitumor effect was mediated partially through changes in normal mammary stem cells (MaSCs); and the long-term safety of i.duc PLD into the normal mouse mammary gland. Her2/neu mice were treated with two i.duc injections of PLD given four weeks apart; pregnancy was induced and mice were followed up for changes in physiology, and tumor formation. We found that all pups born to i.duc PLD-treated Her2/neu mice died without weight gain within 7 days after birth. Despite an additional pregnancy, compared to vehicle control PLD-treated Her2/neu mice had a significantly longer latency and lower frequency of tumor development. Mammary epithelial cells isolated from untreated and i.duc PLD-treated 6-8 months-old multiparous FVB/N mice were analyzed for their repopulating ability in mammary fat pads of naïve recipients. Mice were also monitored for abnormalities in mammary gland morphology and function, including tumor formation. PLD-treated FVB/N mice displayed histomorphologic changes and a significant reduction in the outgrowth potential of cells from the mammary glands. Thus, i.duc PLD administration altered the mammary gland structurally and functionally by reducing the MaSC population, which could compromise milk production. Followed long term, i.duc PLD-treated FVB/N mice developed malignant mammary tumors, confirming similar published findings on doxorubicin injected into the mammary gland of rats. Unless there are fundamental species differences in PLD metabolism in rodents and humans, this finding seriously limits the consideration of i.duc PLD use in the clinic for treatment or prevention of breast cancer.

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Loss of function of GATA3 induces basal-like mammary tumors.

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