A contrasting function for miR-137 in embryonic mammogenesis and adult breast carcinogenesis

Role of T-box transcription factor 3 in gastric cancers

The expression of T-box transcription factor 3 (TBX3) has been identified in various cancers, including gastric cancers. Its role in breast cancers and melanomas has been intensively studied, and its contribution to the progression of cancers through suppressing senescence and promoting epithelial-mesenchymal transition has been reported. Recent reports on the role of TBX3 in gastric cancers have implied its involvement in gastric carcinogenesis. Considering its pivotal role in the initiation and progression of cancers, TBX3 could be a promising therapeutic target for gastric cancers.

MicroRNAs: A Link between Mammary Gland Development and Breast Cancer

Breast cancer is among the most common cancers in women, second to skin cancer. Mammary gland development can influence breast cancer development in later life. Processes such as proliferation, invasion, and migration during mammary gland development can often mirror processes found in breast cancer. MicroRNAs (miRNAs), small, non-coding RNAs, can repress post-transcriptional RNA expression and can regulate up to 80% of all genes. Expression of miRNAs play a key role in mammary gland development, and aberrant expression can initiate or promote breast cancer. Here, we review the role of miRNAs in mammary development and breast cancer, and potential parallel roles. A total of 32 miRNAs were found to be expressed in both mammary gland development and breast cancer. These miRNAs are involved in proliferation, metastasis, invasion, and apoptosis in both processes. Some miRNAs were found to have contradictory roles, possibly due to their ability to target many genes at once. Investigation of miRNAs and their role in mammary gland development may inform about their role in breast cancer. In particular, by studying miRNA in development, mechanisms and potential targets for breast cancer treatment may be elucidated.

Potential miRNAs for miRNA-Based Therapeutics in Breast Cancer

MicroRNAs (miRNAs) are small non-coding RNAs that can post-transcriptionally regulate the genes involved in critical cellular processes. The aberrant expressions of oncogenic or tumor suppressor miRNAs have been associated with cancer progression and malignancies. This resulted in the dysregulation of signaling pathways involved in cell proliferation, apoptosis and survival, metastasis, cancer recurrence and chemoresistance. In this review, we will first (i) provide an overview of the miRNA biogenesis pathways, and in vitro and in vivo models for research, (ii) summarize the most recent findings on the roles of microRNAs (miRNAs) that could potentially be used for miRNA-based therapy in the treatment of breast cancer and (iii) discuss the various therapeutic applications.

miRNA expression profiling of hereditary breast tumors from BRCA1- and BRCA2-germline mutation carriers in Brazil

Background

MicroRNAs (miRNAs) are small non-coding RNAs involved in post-transcriptional gene expression regulation and have been described as key regulators of carcinogenesis. Aberrant miRNA expression has been frequently reported in sporadic breast cancers, but few studies have focused on profiling hereditary breast cancers. In this study, we aimed to identify specific miRNA signatures in hereditary breast tumors and to compare with sporadic breast cancer and normal breast tissues.

Methods

Global miRNA expression profiling using NanoString technology was performed on 43 hereditary breast tumors (15 BRCA1, 14 BRCA2, and 14 BRCAX), 23 sporadic breast tumors and 8 normal breast tissues. These normal breast tissues derived from BRCA1- and BRCA2- mutation carriers (n = 5) and non-mutation carriers (n = 3). Subsequently, we performed receiver operating characteristic (ROC) curve analyses to evaluate the diagnostic performance of differentially expressed miRNAs. Putative target genes of each miRNAs considered as potential biomarkers were identified using miRDIP platform and used for pathway enrichment analysis.

Results

miRNA expression analyses identified several profiles that were specific to hereditary breast cancers. A total of 25 miRNAs were found to be differentially expressed (fold change: > 2.0 and p < 0.05) and considered as potential biomarkers (area under the curve > 0.75) in hereditary breast tumors compared to normal breast tissues, with an expressive upregulation among BRCAX cases. Furthermore, bioinformatic analysis revealed that these miRNAs shared target genes involved in ErbB, FoxO, and PI3K-Akt signaling pathways.

Conclusions

Our results showed that miRNA expression profiling can differentiate hereditary from sporadic breast tumors and normal breast tissues. These miRNAs were remarkably deregulated in BRCAX hereditary breast cancers. Therefore, miRNA signatures can be used as potential novel diagnostic biomarkers for the prediction of BRCA1/2- germline mutations and may be useful for future clinical management.

Downregulated NOX4 underlies a novel inhibitory role of microRNA-137 in prostate cancer

Prostate cancer is the second highest caused by cancer-related death among males. microRNAs (miRs) have been reported to participate in carcinogenesis, yet their roles in prostate cancer are rarely studied or investigated. Therefore, the present study attempted to explore the effect of miR-137 in prostate cancer via regulating NADPH oxidase 4 (NOX4). Initially, microarray analysis was performed to obtain prostate cancer-related differentially expressed genes and miRs that regulated NOX4, followed by detecting the expression of miR-137 and NOX4 and its target relationship. Moreover, PC-3 cells were transfected with small interfering RNA (siNOX4) and miR-137 mimic for exploring the effect of miR-137 on glycolysis, cell proliferation, and apoptosis in prostate cancer by evaluating lactate production, glucose uptake, adenosine triphosphate (ATP) production, viability rate, and expression of cleaved caspases 3, 8, and 9, cytochrome c, cleaved poly ADP ribose polymerase (PARP), Bax, and Bcl-2. miR-137 was vital to prostate cancer progression via regulating NOX4. Besides, miR-137 expressed poorly while NOX4 expressed highly in prostate cancer. NOX4 was the target gene of miR-137. Additionally, overexpression of miR-137 and silencing of NOX4 were observed to decrease NOX4 and Bcl-2 protein expression, but increase cleaved caspases 3, 8, and 9, cytochrome c, cleaved-PARP, and Bax protein expression. Furthermore, miR-137 overexpression and NOX4 silencing contributed to decreased lactate production, glucose uptake, ATP production, and cell proliferation, but increased apoptosis rate. Collectively, the present study showed that miR-137 repressed glycolysis in prostate cancer through knockdown of NOX4, which might be a potential theoretical target for prostate cancer treatment.

Estrogen-induced miR-196a elevation promotes tumor growth and metastasis via targeting SPRED1 in breast cancer

BACKGROUND

Estrogen plays a critical role in breast cancer (BC) progression through estrogen receptor (ER)-mediated gene regulation. Emerging studies suggest that the malignant progress of BC cells is influenced by the cross talk between microRNAs (miRNAs) and ER-α signaling. However, the mechanism and functional linkage between estrogen and miRNAs remain unclear.

METHODS

The expression levels of miR-196a and SPRED1 in BC were tested by qRT-PCR in 46 paired BC and adjacent tissues and by the GEO datasets. The role of miR-196a in estrogen-induced BC development was examined by CCK-8 assay, wound healing assay, Matrigel invasion assay and tumorigenicity assay in nude mice. The binding site of ER-α in miR-196a promoter region was analyzed by ChIP-seq, ChIP assay and luciferase reporter assay. The potential targets of miR-196a in BC cells were explored using the luciferase reporter assay and western blot analysis, and the correlation between miR-196a and SPRED1 was analyzed by Spearman's correlation analysis in BC specimens and GEO dataset. TCGA BRCA data was used to characterize the ESR1 signatures according to MSigDB gene set.

RESULTS

The expression levels of miR-196a were higher in ER-positive (ER+) breast tumors compared to ER-negative (ER-) tumor tissue samples. Besides, miR-196a was involved in estrogen-induced BC cell proliferation, migration and invasion. Notably, the up-regulation of miR-196a was mediated by a direct interaction with estrogen receptor α (ER-α) but not estrogen receptor β (ER-β) in its promoter region, and miR-196a expression levels were positively correlated to ER-α signature scores. Furthermore, SPRED1 was a new direct target of miR-196a which participated in miR-196a-promoted BC development and was suppressed by ligand-activated ER-α signal pathway. Finally, forced expression of miR-196a induced tumor growth of MCF7 cells, while inhibition of miR-196a significantly suppressed the tumor progress in vivo.

CONCLUSIONS

Overall, the identification of estrogen/miR-196a/SPRED1 cascade will shed light on new molecular mechanism of estrogen signaling in BC development and therapy.

MiR-137 suppresses tumor growth and metastasis in clear cell renal cell carcinoma

BACKGROUND

The most frequent type of renal cell carcinoma is called clear-cell renal cell carcinoma (ccRCC) which is associated with a poor prognosis. It has been observed that miR-137 is aberrantly expressed in many different kinds of human malignancies including ccRCC. This research aims to examine the role of miR-137 in ccRCC.

METHODS

Quantitative RT-PCR (qRT-PCR) was applied to measure miR-137 expression in ccRCC and adjacent noncancerous tissue. Gene expression was determined by western blot. Cell Counting Kit-8 (CCK-8) assay, flow cytometry and Transwell assay were used to determine the effects of miR-137 on cell growth, apoptosis and invasion, respectively. Moreover, xenograft and pulmonary metastasis animal models were established to investigate the role of miR-137 in vivo.

RESULTS

Our findings show that there was significant downregulation of miR-137 in ccRCC tissue relative to corresponding non-cancerous tissue. Ectopic miR-137 expression in ccRCC cells led to suppression of cell growth and invasion, as well as apoptosis induction. In contrast, knockdown of miR-137 enhances proliferation and invasion, inhibits apoptosis. It also confirms that miR-137 plays a tumor supressor role in vivo. Mechanically, miR-137 directly targets the 3'-UTR of RLIP76 which is an established oncogene in ccRCC.

CONCLUSION

MiR-137 serves as a tumor suppressor, which can be considered a potential therapeutic target in ccRCC.

Oncogenic miR-137 contributes to cisplatin resistance via repressing CASP3 in lung adenocarcinoma

Although targeted therapy can prolong the survival of non-small cell lung cancer (NSCLC) patients with EGFR mutations, chemotherapy still is the choice for patients with wild-type EGFR or failure in targeted therapy. However, most of the patients will eventually develop chemoresistance. Our previous study showed that miR-137 is a risky microRNA and is associated with poor prognosis in NSCLC patients. Here we investigated the role of miR-137 in cisplatin resistance in lung adenocarcinoma patients. Our data indicated that miR-137 overexpression increases the survival of lung cancer cells exposed to cisplatin and decreases cisplatin-induced apoptosis. Through computational prediction and microarray, we identified caspase-3 (CASP3) as a potential target of miR-137. Luciferase reporter and site-directed mutagenesis assays demonstrated that miR-137 downregulates CASP3 through binding to its 3'-UTR. Moreover, the endogenous CASP3 can be modulated by overexpressing or silencing miR-137 in lung adenocarcinoma cell lines regardless of EGFR status. Suppression of CASP3 by miR-137 provides cancer cells with anti-apoptotic ability, leading to cisplatin resistance. Immunohistochemistry results revealed an inverse correlation between miR-137 and CASP3 expressions in lung adenocarcinoma patients. Together, our data provide a new chemoresistance mechanism in lung adenocarcinoma and a possible target to control chemoresistance in lung adenocarcinoma patients.