The no-observed-adverse-effect level of phthalates promotes proliferation and cell cycle progression in normal human breast cells

OBJECTIVE

The data on the association between phthalates and breast cancer risk remains inconsistent. This study aimed to explore the possible mechanism of low-dose exposures of phthalates, including Butyl benzyl phthalate (BBP), di(n-butyl) phthalate (DBP), and di(20ethylhexyl) phthalate (DEHP), on breast tumorigenesis.

METHODS AND METHODS

MCF-10A normal breast cells were treated with phthalates (10 and 100 nM) and 17β-estradiol (E2, 10 nM), which were co-cultured with fibroblasts from normal mammary tissue. Cell viability, cycle, and apoptosis were detected by MTT assay, flow cytometry, and TUNEL assay respectively. The expression levels of related proteins were determined by Western blot.

RESULTS

Like E2, both 10 nM and 100 nM phthalates exerted significantly higher cell viability, lower apoptosis, and increased cell numbers in the S and G2/M phases with up-regulation of cyclin D/CDK4, cyclin E/CDK2, cyclin A/CDK2, cyclin A/CDK1, and cyclin B/CDK1, compared with the control group. Significant increase in PDK1, P13K, p-AKT, p-mTOR, and BCL-2 expression and a decrease in Bax protein, cytochrome C, caspase 8, and caspase 3 levels were noted in cells treated with 10 nM and 100 nM phthalates and E2, compared with the control group and MCF-10A cells co-cultured with fibroblasts. The effects of the three phthalates were noted to be dose-dependent.

CONCLUSIONS

The results indicate that phthalates at a level below its no-observed-adverse-effect concentration, as defined by the current standards, still induce cell cycle progression and proliferation as well as inhibit apoptosis of normal breast cells. Thus, the possibility of breast tumorigenesis through chronic phthalate exposure should be considered.

Identification of FOXN4 as a tumor suppressor of breast carcinogenesis via the activation of TP53 and deactivation of Notch signaling

OBJECTIVE

Fork head domain-containing transcription factor family (FOX), is comprised of >20 members. Members of FOX family have been implicated in a wide range of physiological and/or diseased conditions. Many of FOX members have been shown to be involved in tumorigenesis and progression. The potential roles in carcinogenesis of FOXN4, a member as one of the vast FOX family, remains relatively unknown.

METHOD

Here, we explored the potential involvement of FOXN4 in breast cancer.

RESULTS

First, observed that a higher FOXN4 was identified in the normal adjacent breast tissue as compared to that in the breast cancer samples; an increased FOXN4 level was associated with a better prognosis in patients with breast cancer. In addition, ectopically expression of FOXN4 led to the decreased cell proliferation, reduced colony formation and metastatic abilities (EMT, migration and invasion) in breast cancer cell lines. Furthermore, we showed the direct interaction between FOXN4 and TP53 and FOXN4 binding led to the increased activity of TP53. Silencing FOXN4 led to reduced TP53 and increased expression of Dll4, Notch and survivin, providing a link between FOXN4 and Notch signaling. Finally, we used patient-derived xenograft mouse model to demonstrate the tumor inhibitory effects of Notch-inhibitor, PF-3084014. We found that PF-3084014 treatment led to a significantly smaller tumor burden and higher survival ratio in patient-derived xenograft mice as compared to the vehicle. This tumor suppressive effect was accompanied by the increased expression of TP53, FOXN4 and decreased Dll4 and Notch.

CONCLUSION

Collectively, our data strongly suggested the tumor suppressive roles of FOXN4 in breast tumorigenesis via the activation of TP53 while suppressing Notch signaling. Future studies are warranted to explore the clinical application of PF-3084104 (Notch inhibitor) for the treatment of breast cancer patients.

The peroxidase PRDX1 inhibits the activated phenotype in mammary fibroblasts through regulating c-Jun N-terminal kinases

Background

Reactive oxygen species (ROS), including hydrogen peroxide, drive differentiation of normal fibroblasts into activated fibroblasts, which can generate high amounts of hydrogen peroxide themselves, thereby increasing oxidative stress in the microenvironment. This way, activated fibroblasts can transition into cancer-associated fibroblasts (CAFs).

Methods

Mammary fibroblasts from either female 8 weeks old PRDX1 knockout and wildtype mice or Balb/c mice were studied for characteristic protein expression using immunofluorescence and immunoblotting. Cancer-associated fibroblasts was examined by transwell migration and invasion assays. The binding of PRDX1 to JNK1 was assessed by co-immuneprecipitation and JNK regulation of CAF phenotypes was examined using the JNK inhibitor SP600125. Extracellular hydrogen peroxide levels were measured by chemiluminescence via the reaction between hypochlorite and luminol. Statistical analyses were done using Students t-test.

Results

We show here PRDX1 activity as an essential switch in regulating the activated phenotype as loss of PRDX1 results in the development of a CAF-like phenotype in mammary fibroblasts. We also show that PRDX1 regulates JNK kinase signaling thereby inhibiting CAF-like markers and CAF invasion. Inhibition of JNK activity reduced these behaviors.

Conclusions

These data suggest that PRDX1 repressed the activated phenotype of fibroblasts in part through JNK inhibition which may present a novel therapeutic option for CAF-enriched cancers such as breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-6031-4) contains supplementary material, which is available to authorized users.

RANKL/RANK/OPG system beyond bone remodeling: involvement in breast cancer and clinical perspectives

RANKL/RANK/OPG system consists of three essential signaling molecules: i) the receptor activator of nuclear factor (NF)-kB-ligand (RANKL), ii) the receptor activator of NF-kB (RANK), and iii) the soluble decoy receptor osteoprotegerin (OPG). Although this system is critical for the regulation of osteoclast differentiation/activation and calcium release from the skeleton, different studies have elucidated its specific role in mammary gland physiology and hormone-driven epithelial proliferation during pregnancy. Of note, several data suggest that progesterone induces mammary RANKL expression in mice and humans. In turn, RANKL controls cell proliferation in breast epithelium under physiological conditions typically associated with higher serum progesterone levels, such as luteal phase of the menstrual cycle and pregnancy. Hence, RANKL/RANK system can be regarded as a major downstream mediator of progesterone-driven mammary epithelial cells proliferation, potentially contributing to breast cancer initiation and progression. Expression of RANKL, RANK, and OPG has been detected in breast cancer cell lines and in human primary breast cancers. To date, dysregulation of RANKL/RANK/OPG system at the skeletal level has been widely documented in the context of metastatic bone disease. In fact, RANKL inhibition through the RANKL-blocking human monoclonal antibody denosumab represents a well-established therapeutic option to prevent skeletal-related events in metastatic bone disease and adjuvant therapy-induced bone loss in breast cancer. On the other hand, the exact role of OPG in breast tumorigenesis is still unclear. This review focuses on molecular mechanisms linking RANKL/RANK/OPG system to mammary tumorigenesis, highlighting pre-clinical and clinical evidence for the potential efficacy of RANKL inhibition as a prevention strategy and adjuvant therapy in breast cancer settings.

Examining the Role of Nuclear Receptors During In Vivo Chemical-Mediated Breast Tumorigenesis

The chemical carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) has been used for many decades to induce skin, mammary, and ovarian tumors in mice. There are however a wide range of doses and treatment regimens in the literature that sometimes confound comparative interpretations of different studies. Here we describe a proven method to generate in vivo DMBA-mediated murine mammary tumors to enable consistent studies of the cell targeted role of genes of interest during this process.

New paradigms for the Hedgehog signaling network in mammary gland development and breast Cancer

The Hedgehog signaling network regulates organogenesis, cell fate, proliferation, survival, and stem cell self-renewal in many mammalian tissues. Aberrant activation of the Hedgehog signaling network is present in ~25% of all cancers, including breast. Altered expression of Hedgehog network genes in the mammary gland can elicit phenotypes at many stages of development. However, synthesizing a cohesive mechanistic model of signaling at different stages of development has been difficult. Emerging data suggest that this difficulty is due, in part, to non-canonical and tissue compartment-specific (i.e., epithelial, versus stromal, versus systemic) functions of Hedgehog network components. With respect to systemic functions, Hedgehog network genes regulate development of endocrine organs that impinge on mammary gland development extrinsically. These new observations offer insight into previously conflicting data, and have bearing on the potential for anti-Hedgehog therapeutics in the treatment of breast cancer.

Embryonic signature in breast cancers; Pluripotency roots of cancer stem cells

Drug discovery programs for preclinical oncology typically select compounds which have a predilection for inducing cytotoxic effects in cancer cell lines and subsequently, for inhibiting the growth of the transplanted cancer cells in vivo (Winquist et al., 2010). Unfortunately, the cytotoxic effect in vitro and inhibition of tumor growth in animal models are not the end story for curing cancer in preclinical models. The reason behind that is the exciting of small sub type of cells that are relatively resistance to therapy and able to repopulate in vivo, called cancer stem cells (CSCs). O leis et al. recently reported that the pluripotency gene Sox2 but not Oct4 or Nanog is expressed in early stage of breast tumor. Furthermore, the authors demonstrated that Sox2 downregulation, inhibited mammosphere formation and delayed tumor formation in xenograft tumor initiation models (Leis et al., 2012). In this review, we will shed the light on the importance of Sox2 in breast and other tissue tumorigenesis and associated aggressiveness.