Accelerated mammary maturation and differentiation, and delayed MMTVneu-induced tumorigenesis of K303R mutant ERalpha transgenic mice

Estrogen receptor-α signaling in post-natal mammary development and breast cancers

17β-estradiol controls post-natal mammary gland development and exerts its effects through Estrogen Receptor ERα, a member of the nuclear receptor family. ERα is also critical for breast cancer progression and remains a central therapeutic target for hormone-dependent breast cancers. In this review, we summarize the current understanding of the complex ERα signaling pathways that involve either classical nuclear “genomic” or membrane “non-genomic” actions and regulate in concert with other hormones the different stages of mammary development. We describe the cellular and molecular features of the luminal cell lineage expressing ERα and provide an overview of the transgenic mouse models impacting ERα signaling, highlighting the pivotal role of ERα in mammary gland morphogenesis and function and its implication in the tumorigenic processes. Finally, we describe the main features of the ERα-positive luminal breast cancers and their modeling in mice.

G9a-mediated methylation of ERα links the PHF20/MOF histone acetyltransferase complex to hormonal gene expression

The euchromatin histone methyltransferase 2 (also known as G9a) methylates histone H3K9 to repress gene expression, but it also acts as a coactivator for some nuclear receptors. The molecular mechanisms underlying this activation remain elusive. Here we show that G9a functions as a coactivator of the endogenous oestrogen receptor α (ERα) in breast cancer cells in a histone methylation-independent manner. G9a dimethylates ERα at K235 both in vitro and in cells. Dimethylation of ERαK235 is recognized by the Tudor domain of PHF20, which recruits the MOF histone acetyltransferase (HAT) complex to ERα target gene promoters to deposit histone H4K16 acetylation promoting active transcription. Together, our data suggest the molecular mechanism by which G9a functions as an ERα coactivator. Along with the PHF20/MOF complex, G9a links the crosstalk between ERα methylation and histone acetylation that governs the epigenetic regulation of hormonal gene expression.

The histone methyltransferase G9a methylates histone H3K9 to repress gene expression, but it also acts as a coactivator for some nuclear receptors. Here, Zhang et al. show that methylation of ERα by G9a recruits the PHF20/MOF complex that deposits histone H4K16 acetylation promoting active transcription.

Estrogen receptor (ER) α mutations in breast cancer: hidden in plain sight

The idea that somatic ERα mutations could play an important role in the evolution of hormone-dependent breast cancers was proposed some years ago (Fuqua J Mammary Gland Biol Neoplasia 6(4):407-417, 2001; Dasgupta et al. Annu Rev Med 65:279-292, 2013), but has remained controversial until recently. A significant amount of new data has confirmed these initial observations and shown their significance, along with much additional work relevant to the treatment of breast cancer. Thus, it is the purpose of this review to summarize the research to date on the existence and clinical consequences of ERα mutations in primary and metastatic breast cancer.

Recombinant human bone morphogenetic protein type 2 jaw reconstruction in patients affected by giant cell tumor

Giant cell tumor (GCT) is a relatively common skeletal tumor. Mandibular localization of this tumor is usually treated with resection of the tumor area. Several autogenous bone-grafting techniques are available for the restoration of large continuity defects of the mandible. However, these procedures are associated with limitations involving postoperative morbidity, difficulty in ambulation (hip graft), and pain. The development of a technique of surgical reconstruction not involving autogenous bone would offer new opportunities for facial bone reconstruction, particularly of the mandible. This study aims to underline the effect of recombinant human bone morphogenetic protein type 2 (rhBMP-2) in a collagen carrier with concomitant bone grafting material in the restoration of continuity critical-size defects after GCT resection in the mandible. The rhBMP-2 was used with absorbable collagen sponge. A total dose of 4 to 8 mg of rhBMP-2 was delivered to the surgical site in concentrations of 1.5 mg/mL. The patient was followed up over a period from 6 to 18 months. Occlusal function was initially restored with conventional prosthesis. Bone formation in the surgical area could be palpated at the end of 3 to 4 months and identified radiographically at the end of 5 to 6 months. The results clearly indicated that the use of rhBMP-2 without concomitant bone grafting materials in large critical-size mandibular defects secondary to GCT produced excellent regeneration of the area, establishing the basis for the return of prosthodontic function.