The Hippo-YAP/TAZ pathway mediates geranylgeranylation signaling in breast cancer progression

Targeting Dysregulated Lipid Metabolism in Cancer with Pharmacological Inhibitors

Metabolic plasticity is recognised as a hallmark of cancer cells, enabling adaptation to microenvironmental changes throughout tumour progression. A dysregulated lipid metabolism plays a pivotal role in promoting oncogenesis. Oncogenic signalling pathways, such as PI3K/AKT/mTOR, JAK/STAT, Hippo, and NF-kB, intersect with the lipid metabolism to drive tumour progression. Furthermore, altered lipid signalling in the tumour microenvironment contributes to immune dysfunction, exacerbating oncogenesis. This review examines the role of lipid metabolism in tumour initiation, invasion, metastasis, and cancer stem cell maintenance. We highlight cybernetic networks in lipid metabolism to uncover avenues for cancer diagnostics, prognostics, and therapeutics.

Interplay Among Metabolism, Epigenetic Modifications, and Gene Expression in Cancer

Epigenetic modifications and metabolism are two fundamental biological processes. During tumorigenesis and cancer development both epigenetic and metabolic alterations occur and are often intertwined together. Epigenetic modifications contribute to metabolic reprogramming by modifying the transcriptional regulation of metabolic enzymes, which is crucial for glucose metabolism, lipid metabolism, and amino acid metabolism. Metabolites provide substrates for epigenetic modifications, including histone modification (methylation, acetylation, and phosphorylation), DNA and RNA methylation and non-coding RNAs. Simultaneously, some metabolites can also serve as substrates for nonhistone post-translational modifications that have an impact on the development of tumors. And metabolic enzymes also regulate epigenetic modifications independent of their metabolites. In addition, metabolites produced by gut microbiota influence host metabolism. Understanding the crosstalk among metabolism, epigenetic modifications, and gene expression in cancer may help researchers explore the mechanisms of carcinogenesis and progression to metastasis, thereby provide strategies for the prevention and therapy of cancer. In this review, we summarize the progress in the understanding of the interactions between cancer metabolism and epigenetics.

Aberrant super-enhancer-driven oncogene ENC1 promotes the radio-resistance of breast carcinoma

Poor response of tumors to radiotherapy is a major clinical obstacle. Because of the dynamic characteristics of the epigenome, identification of possible epigenetic modifiers may be beneficial to confer radio-sensitivity. This research was set to examine the modulation of ectodermal-neural cortex 1 (ENC1) in radio-resistance in breast carcinoma (BC). In silico identification and immunohistochemical staining revealed that overexpression of ENC1 promoted BC metastasis to the bone and brain. Moreover, its overexpression promoted the translocation of YAP1/TAZ into the nucleus and enhanced expression of GLI1, CTGF, and FGF1 through the Hippo pathway. ENC1 expression was controlled by a ~10-kb long SE. ENC1-SEdistal deletion reduced ENC1 expression and inhibited the malignant behavior of BC cells and their resistance to radiotherapy. The binding sites on the ENC1-SE region enriched the shared sequence between TCF4 and ENC1 promoter. Knocking-down TCF4 inhibited luciferase activity and H3K27ac-enriched binding of the ENC1-SE region. Additionally, SE-driven ENC1 overexpression mediated by TCF4 may have clinical implications in radio-resistance in BC patients. Our findings indicated that ENC1 overexpression is mediated by SE and the downstream TCF4 to potentiate the Hippo/YAP1/TAZ pathway. Targeting this axis might be a therapeutic strategy for overcoming BC radio-resistance.

The Role of the Hippo Pathway in Breast Cancer Carcinogenesis, Prognosis, and Treatment: A Systematic Review

Background

The Hippo pathway is a developmental pathway recently discovered in Drosophila melanogaster; in mammals it normally controls organ development and wound healing. Hippo signaling is deregulated in breast cancer (BC). MST1/2 and LATS1/2 kinases are the upstream molecular elements of Hippo signaling which phosphorylate and regulate the two effectors of Hippo signaling, YAP1 and TAZ cotranscriptional activators. The two molecular effectors of the Hippo pathway facilitate their activity through TEAD transcription factors. Several molecular pathways with known oncogenic functions cross-talk with the Hippo pathway.

Methods

A systematic review studying the correlation of the Hippo pathway with BC tumorigenesis, prognosis, and treatment was performed.

Results

Recent literature highlights the critical role of Hippo signaling in a wide spectrum of biological mechanisms in BC.

Discussion

The Hippo pathway has a crucial position in BC molecular biology, cellular behavior, and response to treatment. Targeting the Hippo pathway could potentially improve the prognosis and outcome of BC patients.

MiR-591 functions as tumor suppressor in breast cancer by targeting TCF4 and inhibits Hippo-YAP/TAZ signaling pathway

Background

MicroRNAs have been involved in regulating crucial biological function in some tumors. However, the clinical role and functional effects of miR-591 in breast cancer remain unknown.

Methods

The expression of miR-591 was detected in breast cancer tissues and their paired normal tissues by qRT-PCR. Functional assays were performed to confirm the effects of miR-591 on the proliferation and invasion of breast cancer. Bioinformatics analysis, luciferase reporter assays, western blot and in vitro assays were used to confirm that TCF4 was a target gene of miR-591. Western blot analysis was carried out to analyze the relationship between miR-591 expression and YAP1 expression in breast cancer.

Results

We found that miR-591 expression levels were significantly downregulated in breast cancer tissues compared to adjacent normal tumor tissues. Lower miR-591 expression notably related to lymph node metastasis and advanced TNM stage in patients with breast cancer. In vitro, cell proliferation and invasion were inhibited by transfection of miR-591 mimic in breast cancer cells, but were promoted by transfection of miR-591 inhibitor, compared to the controls. In vivo, we also found that miR-591 mimic significantly inhibited cell proliferation ability. Moreover, we identified that TCF4 was a direct target of miR-591 in breast cancer. TCF4 mediated the inhibiting effects of miR-591 on cell proliferation and invasion in breast cancer cells. In additional, we revealed that miR-591 overexpression significantly inhibited the Hippo-YAP/TAZ signaling pathway in breast cells by downregulated YAP1 expression in breast cells.

Conclusion

Together, these results indicated that miR-591 is downregulated in breast cancer and could act as a potential target of breast cancer treatment.

Low FAT4 expression is associated with a poor prognosis in gastric cancer patients

In this study, we investigated the role of Fat atypical cadherin 4 (FAT4) in gastric cancer (GC) progression. Immunohistochemical analysis showed lower FAT4 expression in tumor tissues from GC patients than in normal gastric epithelium. Lower FAT4 expression was associated with poor prognosis, tumor size and invasion, and lymph node and distant metastases. Multivariate analysis showed that TNM stage, lymph node and distant metastases, Lauren classification, and FAT4 expression were independent prognostic factors in GC. Methylation-specific PCR analysis showed increased FAT4 promoter methylation in GC tumor tissues and cell lines. Higher FAT4 promoter methylation was associated with low FAT4 expression and a poor prognosis. BGC-823 cells showed increased FAT4 expression upon treatment with 5-azacytidine, demethylating agent. FAT4 knockdown in BGC-823 cells led to increased cell proliferation, migration and invasiveness. Moreover, xenografts of BGC-823 cells with FAT4 knockdown showed enhanced tumor growth and metastasis in nude mice. These findings demonstrate that low FAT4 expression is associated with a poor prognosis in GC patients.

Significant association of YAP1 and HSPC111 proteins with poor prognosis in Chinese gastric cancer patients

Hippo-YAP1 is a tumor-suppressor signaling pathway that inhibits cell proliferation and accelerates apoptosis. However, the role of YAP1 in gastric cancer (GC) is still in dispute. Ribosomal biogenesis is closely correlated with human malignancies. HBV pre-S2 trans-regulated protein 3 (HSPC111) is a portion of an RNA-dependent complex and plays a crucial role in ribosome biosynthesis. Nevertheless, little is known about the expression and function of this factor in GC. In the present study, we evaluated the significance of YAP1 together with HSPC111 in gastric cancer. According to The Cancer Genome Atlas database, high YAP1 mRNA expression was significantly associated with poor prognosis of GC patients, and dramatically increased mRNA levels of HSPC111 are observed in GC tissues. Consistent with these findings, we detected increased expression of both YAP1 and HSPC111 in GC cell lines and clinical samples. Notably, nuclear expression of YAP1 was positively correlated with clinical stage (P = 0.041), tumor size (P = 0.023), and lymph node metastasis (P = 0.007), while HSPC111 expression was correlated with lymph node metastasis (P = 0.014). Our analyses also detected a correlation between HSPC111 expression and nuclear and cytoplasmic YAP1 in clinical samples (nuclear: r = 0.2615, P = 0.004; cytoplasm: r = -0.3721, P < 0.001) and cell lines. Finally, we showed that patients who were HSPC111- and nuclear YAP1-positive were associated with the worst prognosis (34.5 ± 4.8 months, p = 0.001), and that nuclear expression of YAP1 might act as an independent prognostic factor for GC patients.

In Vitro Validation of the Hippo Pathway as a Pharmacological Target for Canine Mammary Gland Tumors

Canine mammary tumors (CMTs) are the most common neoplasms in intact female dogs. Some clinical and molecular similarities between certain CMT subtypes and breast cancer make them a potential model for the study of the human disease. As misregulated Hippo signaling is thought to play an important role in breast cancer development and also occurs in CMTs, we sought to determine if Hippo represents a valid pharmacological target for the treatment of CMTs. Six CMT cell lines were assessed for their expression of the Hippo pathway effectors YAP and TAZ and for their sensitivity to verteporfin, an inhibitor of YAP-mediated transcriptional coactivation. Four cell lines that expressed YAP (CMT-9, -12, -28, -47) were found to be very sensitive to verteporfin treatment, which killed the cells through induction of apoptosis with ED50 values of 14-79 nM. Conversely, two YAP-negative cell lines (CF-35, CMT-25) were an order of magnitude more resistant to verteporfin. Verteporfin suppressed the expression of YAP/TAZ target genes, particularly CYR61 and CTGF, which play important roles in breast cancer development. Verteporfin was also able to inhibit cell migration and anchorage-independent growth. Likewise, verteporfin efficiently suppressed tumor cell invasiveness in the CMT-28 and -47 lines, but not in CF-35 cells. Together, our findings provide proof of principle that pharmacological targeting of the Hippo pathway compromises the viability and attenuates the malignant behavior of CMT cells. These results will serve as the basis for the development of novel chemotherapeutic approaches for CMTs that could translate to human medicine.