Assignment of the BLID gene to 11q24.1 by fluorescence in situ hybridization

Hypoxia-activated neuropeptide Y/Y5 receptor/RhoA pathway triggers chromosomal instability and bone metastasis in Ewing sarcoma

Adverse prognosis in Ewing sarcoma (ES) is associated with the presence of metastases, particularly in bone, tumor hypoxia and chromosomal instability (CIN). Yet, a mechanistic link between these factors remains unknown. We demonstrate that in ES, tumor hypoxia selectively exacerbates bone metastasis. This process is triggered by hypoxia-induced stimulation of the neuropeptide Y (NPY)/Y5 receptor (Y5R) pathway, which leads to RhoA over-activation and cytokinesis failure. These mitotic defects result in the formation of polyploid ES cells, the progeny of which exhibit high CIN, an ability to invade and colonize bone, and a resistance to chemotherapy. Blocking Y5R in hypoxic ES tumors prevents polyploidization and bone metastasis. Our findings provide evidence for the role of the hypoxia-inducible NPY/Y5R/RhoA axis in promoting genomic changes and subsequent osseous dissemination in ES, and suggest that targeting this pathway may prevent CIN and disease progression in ES and other cancers rich in NPY and Y5R.

Ewing sarcoma tumour cells frequently metastasize to the bone but the molecular mechanisms governing this process are not well understood. Here, the authors show that neuropeptide Y/Y5 receptor pathway is activated in the hypoxic tumour microenvironment, which results in cytokinesis defects and chromosomal instability, leading to bone invasion.

Exosomal transfer of miR-501 confers doxorubicin resistance and tumorigenesis via targeting of BLID in gastric cancer

Exosomal transfer of oncogenic miRNAs can enhance recipient cell growth, metastasis and chemoresistance. Currently we found that microRNA-501-5p (miR-501) was overexpressed in doxorubicin-resistant gastric cancer (GC) SGC7901/ADR cell-secreted exosomes (ADR Exo) than that in SGC7901 cell-secreted exosomes (7901 Exo). ADR Exo was internalized by SGC7901, and a Cy3-miR-501 mimic was transferred from SGC7901/ADR to SGC7901 via exosomes. ADR Exo conferred doxorubicin resistance, proliferation, migration and invasion abilities to negative control miRNA inhibitor-expressing GC cells, whereas it inhibited apoptosis. MiR-501 knockdown or BH3-like motif-containing protein, cell death inducer (BLID) overexpression could reverse the effects of ADR Exo on recipient cells. SGC7901 cells cocultured with SGC7901/ADR prior to treatment with GW4869 or transfection of a miR-501 inhibitor were sensitive to doxorubicin and exhibited attenuated proliferation, migration and invasion and increased apoptosis. The intratumoral injection of ADR Exo into negative control miRNA inhibitor-expressing SGC7901 cells induced rapid subcutaneous tumor growth and resistance to doxorubicin compared to that of miR-501 knockdown or BLID-overexpressing cells. This effect is possibly achieved by exosomal miR-501-induced downregulation of BLID, subsequent inactivation of caspase-9/-3 and phosphorylation of Akt. Exosomal miR-501 might be a therapeutic target for GC.

BLID: A Novel Tumor-Suppressor Gene

BLID (BH3-like motif containing, cell death inducer), also known as breast cancer cell 2 (BRCC2), was first reported in the human breast cancer cell line in 2004. BLID is a BH3-like motif containing apoptotic member of the Bcl-2 family. Recently, the BLID tumor-suppressor roles have been fully established. Several studies have found that BLID is frequently downregulated in many human cancers and the downregulation is often associated with tumor progression. Multivariate analysis indicated that BLID is an independent prognostic factor for overall survival and distant metastasis-free survival. Moreover, BLID can inhibit breast cancer cell growth and metastasis and promote apoptosis. BLID can regulate the expression of various tumor-related genes and proteins, such as AKT and MMP. In this review, we provide an overview of current knowledge concerning the role of BLID in tumor development and progression. To our knowledge, this is the first review about the role of this novel tumor-suppressor gene in tumor development and progression.

Aberrant BLID expression is associated with breast cancer progression

In our previous study, we have found that BH3-like motif containing, cell death inducer (BLID) was a tumor suppressor in breast cancer, and its downregulation was correlated with both poor disease-free and overall survival. In the present study, we aimed to explore the possible role of BLID in breast cancer progression. We found that BLID was strongly expressed in all normal breast tissues, and it became lower and wreaker gradually in the progression from normal, UDH (usual ductal hyperplasia), ADH (atypical ductal hyperplasia), and DCIS (ductal carcinoma in situ) to breast cancer. Statistical analysis demonstrated significant different BLID expressions between proliferative and cancerous breast lesions. Our data suggested that loss of BLID may contribute to the progression of intraductal proliferation lesions to breast cancer. Our finding gives a new clue that BLID might be a potential indicator for progression of breast cancer in the future.

BRCC2 inhibits breast cancer cell growth and metastasis in vitro and in vivo via downregulating AKT pathway

In our previous study, we demonstrated that the BRCC2 (breast cancer cell 2) gene is a proapoptotic molecule that interacts with Bcl-X_L. BRCC2 downregulation is associated with poor disease-free and overall survival in breast cancer. In this study, we aimed to investigate the role of BRCC2 in tumor suppression in breast cancer. In clinical breast cancer samples, we found that BRCC2 expression was significantly downregulated in cancer lesions compared with paired normal breast tissues. By silencing or overexpressing BRCC2 in breast cancer cells, we found that BRCC2 could inhibit cell growth and metastasis in vitro. An in vivo assay showed that BRCC2 not only dramatically inhibited breast cancer cell xenograft formation and growth but also inhibited breast cancer cell metastasis in a lung metastasis model. Moreover, we demonstrated that BRCC2 inhibited breast cancer metastasis via regulation of the Akt pathway. Thus, our study provided evidence that BRCC2 functions as a novel tumor suppressor in breast cancer and may be a potential therapeutic target for breast cancer management.

The nuclear coactivator amplified in breast cancer 1 maintains tumor-initiating cells during development of ductal carcinoma in situ

The key molecular events required for the formation of Ductal Carcinoma in Situ (DCIS) and its progression to invasive breast carcinoma have not been defined. Here we show that the nuclear receptor coactivator Amplified In Breast cancer 1 (AIB1) is expressed at low levels in normal breast but is highly expressed in DCIS lesions. This is of significance since reduction of AIB1 in human MCFDCIS cells restored a more normal 3D mammary acinar structure. Reduction of AIB1 in MCFDCIS cells, both prior to DCIS development or in existing MCFDCIS lesions in vivo, inhibited tumor growth and led to smaller, necrotic lesions. AIB1 reduction in MCFDCIS cells was correlated with significant reduction in the CD24−/CD44+ Breast Cancer Initiating Cells (BCIC) population, and a decrease in myoepithelial progenitor cells in the DCIS lesions in vitro and in vivo. Loss of AIB1 in MCFDCIS cells was also accompanied by a loss of expression of NOTCH 2, 3 and 4, JAG2, HES1, GATA3, HER2 and HER3 in vivo. These signaling molecules have been associated with differentiation of breast epithelial progenitor cells. These data indicate that AIB1 plays a central role in the initiation and maintenance of DCIS and that reduction of AIB1 causes loss of BCIC, loss of components of the NOTCH, HER2 and HER3 signaling pathways and fewer DCIS myoepithelial progenitor cells in vivo. We propose that increased expression of AIB1, through maintenance of BCIC, facilitates formation of DCIS, a necessary step prior to development of invasive disease.

Frequent loss of the BLID gene in early-onset breast cancer

The BH3-like motif-containing inducer of cell death (BLID) is an intronless gene localized on 11q24.1. Loss of that region has frequently been reported in early-onset breast cancer and is significantly associated with poor prognosis and reduced survival. Downregulation of BLID is associated with younger age, triple-negative phenotype, and reduced disease-free and overall survival of breast cancer patients. In this study, we investigated allelic loss of BLID in breast tumor specimens from 78 women with invasive breast cancer using 2 dinucleotide polymorphic markers closely linked to the BLID gene (no intragenic marker for BLID is available). Seventy-three cases were informative. Overall, loss of heterozygosity (LOH) at the BLID locus was detected in 32% of the informative cases (23/73). However, in patients 40 years old and younger, LOH was detected in 50% of the cases (9/18). Patients aged 40 years and younger were significantly more likely to experience LOH than those aged 41-55 years (p = 0.04). Specifically, the odds of BLID loss for patients aged 40 years and younger were 3.7 times the odds of loss for patients aged 41-55 years (95% CI, 1.1-13). Our findings suggest a tumor suppressor role of the BLID gene in early-onset breast cancer.