The Hippo kinases LATS1 and 2 control human breast cell fate via crosstalk with ERα

miR-372 promotes breast cancer cell proliferation by directly targeting LATS2

MicroRNAs (miRs) have previously been demonstrated to be important in the tumorigenesis and progression of breast cancer. miR-372 was previously revealed to be involved in various types of human cancer, however its function in breast cancer remains largely unknown. The present study demonstrated that miR-372 is frequently overexpressed in breast cancer cell lines and tissues. The downregulation of miR-372 markedly inhibited cell proliferation, arrested the cell cycle in the G1/S phase, and increased the apoptosis of breast cancer cells. Consistently, an in vivo xenograft study also demonstrated the suppressive effects of miR-372 knockdown on tumor growth. Further studies revealed that miR-372 modulated the expression of large tumor suppressor kinase 2 (LATS2) by directly targeting its 3'-untranslated region in breast cancer cells. Furthermore, silencing of LATS2 was able to rescue the effect of the miR-372 inhibitor. Overall, the results suggest that miR-372 functions as an oncogenic miRNA in breast cancer by targeting LATS2.

NEDD4 promotes cell growth and motility in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. In China, the situation is even worse as cancer incidence and mortality continue to increase rapidly. Although tremendous progress has been made toward HCC treatments, the benefits for liver cancer patients are still limited. Therefore, it is necessary to identify and develop novel therapeutic methods. Neuronally expressed developmentally downregulated 4 (NEDD4), an E3 ubiquitin ligase, plays a critical role in the development and progression of various types of human cancers. In our study, NEDD4 acts as an oncoprotein in both QGY7703 and SMMC7721 liver cancer cell lines. We found that depletion of NEDD4 by siRNA transfection led to inhibition of cell growth, invasion and migration, and promotion of apoptosis. In contrast, overexpression of NEDD4 via plasmid transfection resulted in facilitated cell proliferation, invasion and migration, and decreased apoptosis. Importantly, we observed that tumor suppressor LATS1, also a core component of Hippo pathway, was negatively regulated by NEDD4 in liver cancer cells. Our findings suggested that NEDD4 may be involved in the HCC progression via regulating LATS1 associated signaling pathway. Therefore, targeting NEDD4-LATS1 signaling could be a potential therapeutic option for HCC treatment.

The Hippo pathway in organ development, homeostasis, and regeneration

The Hippo pathway is a universal governor of organ size, tissue homeostasis, and regeneration. A growing body of work has advanced our understanding of Hippo pathway regulation of cell proliferation, differentiation, and spatial patterning not only in organ development but also upon injury-induced regeneration. The pathway's central role in stem cell biology thus implicates its potential for therapeutic manipulation in mammalian organ regeneration. In this review, we survey recent literature linking the Hippo pathway to the development, homeostasis, and regeneration of various organs, including Hippo-independent roles for YAP, defined here as YAP functions that are not regulated by the Hippo pathway kinases LATS1/2.

Predicted molecular targets and pathways for germacrone, curdione, and furanodiene in the treatment of breast cancer using a bioinformatics approach

Germacrone, curdione, and furanodiene have been shown to be useful in the treatment of breast cancer but the pharmacological mechanism of action is unclear. In this paper, we explored a new method to study the molecular network and function of Traditional Chinese Medicine (TCM) herbs and their corresponding ingredients with bioinformatics tools, including PubChem Compound Database, BATMAN-TCM, SystemsDock, Coremine Medical, Gene ontology, and KEGG. Eleven targeted genes/proteins, 4 key pathways, and 10 biological processes were identified to participate in the mechanism of action in treating breast cancer with germacrone, curdione, and furanodiene. The information achieved by the bioinformatics tools was useful to interpretation the molecular mechanism for the treatment of germacrone, curdione, and furanodiene on breast cancers.

Proof of region-specific multipotent progenitors in human breast epithelia

We have devised a culture system with conditions that allow primary breast myoepithelial cells (MEPs) to be passaged in a manner that sustains either nonmyodifferentiated or myodifferentiated cell populations without permitting contaminating luminal cells to grow. We show that progenitor activity and potency of MEPs to generate luminal cells in culture and in vivo rely on maintenance of myodifferentiation. Specific isolation and propagation of topographically distinct MEPs reveal the existence of multipotent progenitors in terminal duct lobular units. These findings have important implications for our understanding of the emergence of candidate luminal precursor cells to human breast cancer.

The human breast parenchyma consists of collecting ducts and terminal duct lobular units (TDLUs). The TDLU is the site of origin of most breast cancers. The reason for such focal susceptibility to cancer remains poorly understood. Here, we take advantage of a region-specific heterogeneity in luminal progenitors to interrogate the differentiation repertoire of candidate stem cells in TDLUs. We show that stem-like activity in serial passage culture and in vivo breast morphogenesis relies on the preservation of a myoepithelial phenotype. By enrichment for region-specific progenitors, we identify bipotent and multipotent progenitors in ducts and TDLUs, respectively. We propose that focal breast cancer susceptibility, at least in part, originates from region-specific myoepithelial progenitors.

Exercise-Induced Catecholamines Activate the Hippo Tumor Suppressor Pathway to Reduce Risks of Breast Cancer Development

Strong epidemiologic evidence documents the protective effect of physical activity on breast cancer risk, recurrence, and mortality, but the underlying mechanisms remain to be identified. Using human exercise-conditioned serum for breast cancer cell incubation studies and murine exercise interventions, we aimed to identify exercise factors and signaling pathways involved in the exercise-dependent suppression of breast cancer. Exercise-conditioned serum from both women with breast cancer (n = 20) and healthy women (n = 7) decreased MCF-7 (hormone-sensitive) and MDA-MB-231 (hormone-insensitive) breast cancer cell viability in vitro by 11% to 19% and reduced tumorigenesis by 50% when preincubated MCF-7 breast cancer cells were inoculated into NMRI-Foxn1^nu mice. This exercise-mediated suppression of cell viability and tumor formation was completely blunted by blockade of β-adrenergic signaling in MCF-7 cells, indicating that catecholamines were the responsible exercise factors. Both epinephrine (EPI) and norepinephrine (NE) could directly inhibit breast cancer cell viability, as well as tumor growth in vivo EPI and NE activate the tumor suppressor Hippo signaling pathway, and the suppressive effect of exercise-conditioned serum was found to be mediated through phosphorylation and cytoplasmic retention of YAP and reduced expression of downstream target genes, for example, ANKRD1 and CTGF. In parallel, tumor-bearing mice with access to running wheels showed reduced growth of MCF-7 (-36%, P < 0.05) and MDA-MB-231 (-66%, P < 0.01) tumors and, for the MCF-7 tumor, increased regulation of the Hippo signaling pathway. Taken together, our findings offer a mechanistic explanation for exercise-dependent suppression of breast cancer cell growth. Cancer Res; 77(18); 4894-904. ©2017 AACR.

Circular RNA_LARP4 inhibits cell proliferation and invasion of gastric cancer by sponging miR-424-5p and regulating LATS1 expression

BACKGROUND

Non-coding RNAs (ncRNAs) have been shown to regulate gene expression involved in tumor progression of multiple malignancies. Our previous studies indicated that large tumor suppressor kinase 1 (LATS1), a core part of Hippo signaling pathway, functions as a tumor suppressor in gastric cancer (GC). But, the underlying molecular mechanisms by which ncRNAs modulate LATS1 expression in GC remain undetermined.

METHODS

The correlation of LATS1 and has-miR-424-5p (miR-424) expression with clinicopathological characteristics and prognosis of GC patients was analyzed by TCGA RNA-sequencing data. A novel circular RNA_LARP4 (circLARP4) was identified to sponge miR-424 by circRNA expression profile and bioinformatic analysis. The binding site between miR-424 and LATS1 or circLARP4 was verified using dual luciferase assay and RNA immunoprecipitation (RIP) assay. The expression and localization of circLARP4 in GC tissues were investigated by fluorescence in situ hybridization (FISH). MTT, colony formation, Transwell and EdU assays were performed to assess the effects of miR-424 or circLARP4 on cell proliferation and invasion.

RESULTS

Increased miR-424 expression or decreased LATS1 expression was associated with pathological stage and unfavorable prognosis of GC patients. Ectopic expression of miR-424 promoted proliferation and invasion of GC cells by targeting LATS1 gene. Furthermore, circLARP4 was mainly localized in the cytoplasm and inhibited biological behaviors of GC cells by sponging miR-424. The expression of circLARP4 was downregulated in GC tissues and represented an independent prognostic factor for overall survival of GC patients.

CONCLUSION

circLARP4 may act as a novel tumor suppressive factor and a potential biomarker in GC.

Melatonin and Hippo Pathway: Is There Existing Cross-Talk?

Melatonin is an indolic hormone that regulates a plethora of functions ranging from the regulation of circadian rhythms and antioxidant properties to the induction and maintenance of tumor suppressor pathways. It binds to specific receptors as well as to some cytosolic proteins, leading to several cellular signaling cascades. Recently, the involvement of melatonin in cancer insurgence and progression has clearly been demonstrated. In this review, we will first describe the structure and functions of melatonin and its receptors, and then discuss both molecular and epidemiological evidence on melatonin anticancer effects. Finally, we will shed light on potential cross-talk between melatonin signaling and the Hippo signaling pathway, along with the possible implications for cancer therapy.

MiR-590-3p promotes proliferation and metastasis of colorectal cancer via Hippo pathway

Studies reported that miR-590-3p was involved in human cancer progression. However, its roles of oncogene or anti-oncogene in malignancies still remain elusive. This study was aimed to investigate the effect of miR-590-3p on the cell proliferation and metastasis via Hippo pathway in colorectal cancer (CRC). In our study, miR-590-3p was demonstrated highly expressed in CRC tissues, compared with adjacent normal tissues (P<0.05). In addition, miR-590-3p was positively associated with TNM stage and distant metastasis. Survival analysis showed that high miR-590-3p was related with poor overall survival rate. Then, over-expressed miR-590-3p was demonstrated to promote proliferation, invasion and migration of colon caner cells. What’s more, MST1, LATS1 and SAV1 mRNA were showed lowly expressed and YAP1 expression in mRNA and protein levels were highly expressed in CRC tissues, compared with adjacent normal tissues (all P<0.05). miR-590-3p expression was negatively associated with LATS1 and SAV1 mRNA respectively and positively related with YAP1 mRNA in CRC tissues, meanwhile, there was no relationship between miR-590-3p and MST1 mRNA. Furthermore, over-expressing miR-590-3p inhibited expressions of LATS1 and SAV1, promoted YAP1 expression and didn’t effect MST1 expression in colon cancer cells. And luciferase assay showed that miR-590-3p over-expression inhibited the luciferase activity of LATS1 and SAV1 3’UTR, meanwhile it had no effect on the mutated form of these two plasmids. Taken together, these data suggest that highly-expressed miR-590-3p promotes biological effect of proliferation and metastasis via targeting Hippo pathway, and predicts worse clinical outcomes of CRC patients.

The LATS1 and LATS2 tumor suppressors: beyond the Hippo pathway

Proper cellular functionality and homeostasis are maintained by the convergent integration of various signaling cascades, which enable cells to respond to internal and external changes. The Dbf2-related kinases LATS1 and LATS2 (LATS) have emerged as central regulators of cell fate, by modulating the functions of numerous oncogenic or tumor suppressive effectors, including the canonical Hippo effectors YAP/TAZ, the Aurora mitotic kinase family, estrogen signaling and the tumor suppressive transcription factor p53. While the basic functions of the LATS kinase module are strongly conserved over evolution, the genomic duplication event leading to the emergence of two closely related kinases in higher organisms has increased the complexity of this signaling network. Here, we review the LATS1 and LATS2 intrinsic features as well as their reported cellular activities, emphasizing unique characteristics of each kinase. While differential activities between the two paralogous kinases have been reported, many converge to similar pathways and outcomes. Interestingly, the regulatory networks controlling the mRNA expression pattern of LATS1 and LATS2 differ strongly, and may contribute to the differences in protein binding partners of each kinase and in the subcellular locations in which each kinase exerts its functions.

Cancer: a new role for non-canonical Hippo signaling

The molecular mechanisms governing self-renewal and differentiation of the mammary epithelium are incompletely defined; a better understanding of the events implicated in the specification and expansion of luminal progenitors is of particular importance as many breast cancers originate from their transformation. Britschgi et al. found that, in addition to phosphorylating and inactivating YAP, LATS functions as a scaffold to facilitate estrogen receptor-α ubiquitylation by the E3 ligase CRL4 and consequently suppresses luminal progenitor specification and expansion.

Papers of note in Nature (7638)

This week’s articles are about peptides that mediate communication between viruses, how microglia induce reactive astrocytes that contribute to neuronal cell death, and how kinases of the Hippo pathway influence breast cell fate.