Bone morphogenetic proteins mediate crosstalk between cancer cells and the tumour microenvironment at primary tumours and metastases (Review)

Upregulated bone morphogenetic protein 8A (BMP8A) in triple negative breast cancer (TNBC) and its involvement in the bone metastasis

Objective

The present study aimed to investigate the involvement of aberrant BMP8A expression in TNBC and bone metastasis.

Methods

Aberrant expression of BMP8A in breast cancer was first determined by analyzing The Cancer Genome Atlas breast cancer cohort (TCGA-BRCA) and an immunohistochemical (IHC) staining of BMP8A in a breast cancer tissue microarray (TMA). Clinical relevance of deregulated BMP8A in breast cancer was assessed using Kaplan-Meier online analysis. The influence of BMP8A on cellular functions of two TNBC cell lines was assessed using in vitro assays. Conditional medium (CM) collected from the supernatant of hFOB cells and bone matrix extract (BME) was applied to mimic the bone micro-environment to evaluate the role played by BMP8A in bone metastasis. Correlations with both osteolytic and osteoblastic markers were evaluated in the TCGA-BRCA cohort. Expression of certain responsive genes was quantified in the BMP8A overexpression cell lines. Additionally, signal transduction through both Smad-dependent and independent pathways was evaluated using Western blot assay.

Results

Compared to the adjacent normal tissues, BMP8A expression was significantly increased in primary tumors (p < 0.05) which was associated with shorter distant metastasis free survival (DMFS) in TNBC (p < 0.05). BMP8A was observed to enhance cell invasion and migration within TNBC cells. In the simulated bone milieu, both MDA-MB-231BMP8Aexp and BT549BMP8Aexp cells presented enhanced invasiveness. BMP8A level was strongly correlated with most osteolytic and osteoblastic markers, suggesting the potential involvement of BMP8A in bone metastasis in TNBC. Receptor activator of nuclear factor kappa-B ligand (RANKL) expression was significantly increased in BMP8A overexpressed triple-negative cell lines (MDA-MB-231 and BT549). Furthermore, enhanced phosphorylation of Smad3 and increased expression of epidermal growth factor receptor (EGFR) were observed in MDA-MB-231 cells overexpressing BMP8A.

Conclusion

BMP8A was upregulated in TNBC which was associated with poorer DMFS. BMP8A overexpression enhanced the invasion and migration of TNBC cells. With a putative role in osteolytic bone metastasis in TNBC, BMP8A represents a promising candidate for further investigation into its therapeutic potential.

Aberrant expression of bone morphogenetic proteins in the disease progression and metastasis of breast cancer

Background

Bone morphogenetic proteins (BMPs) play crucial roles in the tumorigenesis and metastasis of cancers. Controversy remains about the exact implications of BMPs and their antagonists in breast cancer (BC), due to their diverse and complex biological functions and signalling. A comprehensive study of the whole family and their signalling in breast cancer is provoked.

Methods

Aberrant expression of BMP, BMP receptors and antagonists in primary tumours in breast cancer were analysed by using TCGA-BRCA and E-MTAB-6703 cohorts. Related biomarkers including ER, HER, proliferation, invasion, angiogenesis, lymphangiogenesis and bone metastasis were involved to identify the relationship with BMPs in breast cancer.

Results

The present study showed BMP8B was significantly increased in breast tumours, while BMP6 and ACVRL1 were decreased in breast cancer tissues. The expressions of BMP2, BMP6, TGFBR1 and GREM1 were significantly correlated with BC patients' poor overall survival. Aberrant expression of BMPs, together with BMP receptors, were explored in different subtypes of breast cancer according to ER, PR and HER2 status. Furthermore, higher levels of BMP2, BMP6 and GDF5 were revealed in triple negative breast cancer (TNBC) whilst BMP4, GDF15, ACVR1B, ACVR2B and BMPR1B were relatively higher in Luminal type BC. ACVR1B and BMPR1B were positively correlated with ERα but were inversely correlated with ERβ. High expression of GDF15, BMP4 and ACVR1B were associated with poorer overall survival in HER2 positive BC. BMPs also play dual roles in tumour growth and metastasis of BC.

Conclusion

A shift pattern of BMPs was showed in different subtypes of breast cancer suggesting a subtype specific involvement. It provokes more research to shed light on the exact role of these BMPs and receptors in the disease progression and distant metastasis through a regulation of proliferation, invasion and EMT.

Targeting the stem cell niche micro-environment as therapeutic strategies in aging

Adult stem cells (ASCs) reside throughout the body and support various tissue. Owing to their self-renewal capacity and differentiation potential, ASCs have the potential to be used in regenerative medicine. Their survival, quiescence, and activation are influenced by specific signals within their microenvironment or niche. In better words, the stem cell function is significantly influenced by various extrinsic signals derived from the niche. The stem cell niche is a complex and dynamic network surrounding stem cells that plays a crucial role in maintaining stemness. Studies on stem cell niche have suggested that aged niche contributes to the decline in stem cell function. Notably, functional loss of stem cells is highly associated with aging and age-related disorders. The stem cell niche is comprised of complex interactions between multiple cell types. Over the years, essential aspects of the stem cell niche have been revealed, including cell-cell contact, extracellular matrix interaction, soluble signaling factors, and biochemical and biophysical signals. Any alteration in the stem cell niche causes cell damage and affects the regenerative properties of the stem cells. A pristine stem cell niche might be essential for the proper functioning of stem cells and the maintenance of tissue homeostasis. In this regard, niche-targeted interventions may alleviate problems associated with aging in stem cell behavior. The purpose of this perspective is to discuss recent findings in the field of stem cell aging, heterogeneity of stem cell niches, and impact of age-related changes on stem cell behavior. We further focused on how the niche affects stem cells in homeostasis, aging, and the progression of malignant diseases. Finally, we detail the therapeutic strategies for tissue repair, with a particular emphasis on aging.

Muscle and Bone Defects in Metastatic Disease

PURPOSE OF REVIEW

The present review addresses most recently identified mechanisms implicated in metastasis-induced bone resorption and muscle-wasting syndrome, known as cachexia.

RECENT FINDINGS

Metastatic disease in bone and soft tissues is often associated with skeletal muscle defects. Recent studies have identified a number of secreted molecules and extracellular vesicles that contribute to cancer cell growth and metastasis leading to bone destruction and muscle atrophy. In addition, alterations in muscle microenvironment including dysfunctions in hepatic and mitochondrial metabolism have been implicated in cancer-induced regeneration defect and muscle loss. Moreover, we review novel in vitro and animal models including promising new drug candidates for bone metastases and cancer cachexia. Preservation of bone health could be highly beneficial for maintaining muscle mass and function. Therefore, a better understanding of molecular pathways implicated in bone and muscle crosstalk in metastatic disease may provide new insights and identify new strategies to improve current anticancer therapeutics.