Inducible knockout of Twist1 in young and adult mice prolongs hair growth cycle and has mild effects on general health, supporting Twist1 as a preferential cancer target.

Twist1 promotes epithelial-mesenchymal transition, invasion, metastasis, stemness, and chemotherapy resistance in cancer cells and thus is a potential target for cancer therapy. However, Twist1-null mice are embryonic lethal, and people with one Twist1 germline mutant allele develop Saethre-Chotzen syndrome; it is questionable whether Twist1 can be targeted in patients without severe adverse effects. We found that Twist1 is expressed in several tissues, including fibroblasts of the mammary glands and dermal papilla cells of the hair follicles. We developed a tamoxifen-inducible Twist1 knockout mouse model; Twist1 knockout in 6-week-old female mice did not affect mammary gland morphogenesis and function during pregnancy and lactation. In both males and females, the knockout did not influence body weight gain, heart rate, or total lean and fat components. The knockout also did not alter blood pressure in males, although it slightly reduced blood pressure in females. Although Twist1 is not cyclically expressed in dermal papilla cells, knockout of Twist1 at postnatal day 13 (when hair follicles have developed) drastically extended the anagen phase and accelerated hair growth. These results indicate that Twist1 is not essential for maintaining an overall healthy condition in young and adult mice and that loss of function facilitates hair growth in adulthood, supporting Twist1 as a preferential target for cancer therapy.

NCOA1 Directly Targets M-CSF1 Expression to Promote Breast Cancer Metastasis.

In breast cancer, overexpression of the nuclear coactivator NCOA1 (SRC-1) is associated with disease recurrence and resistance to endocrine therapy. To examine the impact of NCOA1 overexpression on morphogenesis and carcinogenesis in the mammary gland (MG), we generated MMTV-hNCOA1 transgenic [Tg(NCOA1)] mice. In the context of two distinct transgenic models of breast cancer, NCOA1 overexpression did not affect the morphology or tumor-forming capability of MG epithelial cells. However, NCOA1 overexpression increased the number of circulating breast cancer cells and the efficiency of lung metastasis. Mechanistic investigations showed that NCOA1 and c-Fos were recruited to a functional AP-1 site in the macrophage attractant CSF1 promoter, directly upregulating colony-simulating factor 1 (CSF1) expression to enhance macrophage recruitment and metastasis. Conversely, silencing NCOA1 reduced CSF1 expression and decreased macrophage recruitment and breast cancer cell metastasis. In a cohort of 453 human breast tumors, NCOA1 and CSF1 levels correlated positively with disease recurrence, higher tumor grade, and poor prognosis. Together, our results define an NCOA1/AP-1/CSF1 regulatory axis that promotes breast cancer metastasis, offering a novel therapeutic target for impeding this process.

Metastatic progression with resistance to aromatase inhibitors is driven by the steroid receptor coactivator SRC-1.

Aromatase inhibitors (AI) are a standard-of-care treatment for postmenopausal, estrogen receptor-positive breast cancers. Although tumor recurrence on AI therapy occurs, the mechanisms underlying acquired resistance to AIs remain unknown. In this study, we examined a cohort of endocrine-treated breast cancer patients and used a cell line model of resistance to the AI letrozole. In patients treated with a first-line AI, hormone receptor switching between primary and resistant tumors was a common feature of disease recurrence. Resistant cells exhibited a switch from steroid-responsive growth to growth factor-responsive and endocrine-independent growth, which was accompanied by the development of a more migratory and disorganized phenotype. Both the resistant cells and tumors from AI-resistant patients showed high expression of the steroid receptor coactivator SRC-1. Direct interactions between SRC-1 and the transcription factor Ets2 regulated Myc and MMP9. SRC-1 was required for the aggressive and motile phenotype of AI-resistant cells. Interestingly, SRC-1 expression in primary and/or recurrent tumors was associated with a reduction in disease-free survival in treated patients. Moreover, there was a significant association between SRC-1 and Ets2 in the recurrent tissue compared with the matched primary tumor. Together, our findings elucidate a mechanism of AI-specific metastatic progression in which interactions between SRC-1 and Ets2 promote dedifferentiation and migration in hormone-dependent breast cancer.

The cytoplasmic tail dileucine motif LL572 determines the glycosylation pattern of membrane-type 1 matrix metalloproteinase.

Membrane-type 1 matrix metalloproteinase (MT1-MMP; MMP-14) drives fundamental physiological and pathological processes, due to its ability to process a broad spectrum of substrates. Because subtle changes in its activity can produce profound physiological effects, MT1-MMP is tightly regulated. Currently, many aspects of this regulation remain to be elucidated. It has recently been discovered that O-linked glycosylation defines the substrate spectrum of MT1-MMP. We hypothesized that a mutual interdependency exists between MT1-MMP trafficking and glycosylation. Lectin precipitation, metabolic labeling, enzymatic deglycosylation, and site-directed mutagenesis studies demonstrate that the LL(572) motif in the cytoplasmic tail of MT1-MMP influences the composition of the complex O-linked carbohydrates attached to the hinge region of the protein. This influence appears to be independent from major effects on cell surface trafficking. MT1-MMP undergoes extensive processing after its synthesis. The origins and the molecular characters of its multiple forms are incompletely understood. Here, we develop and present a model for the sequential, post-translational processing of MT1-MMP that defines stages in the post-synthetic pathway pursued by the protein.