Transcriptional co-activators YAP/TAZ: Potential therapeutic targets for metastatic breast cancer

Identification of PTPN12 Phosphatase as a Novel Negative Regulator of Hippo Pathway Effectors YAP/TAZ in Breast Cancer

The Hippo pathway plays crucial roles in governing various biological processes during tumorigenesis and metastasis. Within this pathway, upstream signaling stimuli activate a core kinase cascade, involving MST1/2 and LATS1/2, that subsequently phosphorylates and inhibits the transcriptional co-activators YAP and its paralog TAZ. This inhibition modulates the transcriptional regulation of downstream target genes, impacting cell proliferation, migration, and death. Despite the acknowledged significance of protein kinases in the Hippo pathway, the regulatory influence of protein phosphatases remains largely unexplored. In this study, we conducted the first gain-of-functional screen for protein tyrosine phosphatases (PTPs) regulating the Hippo pathway. Utilizing a LATS kinase biosensor (LATS-BS), a YAP/TAZ activity reporter (STBS-Luc), and a comprehensive PTP library, we identified numerous novel PTPs that play regulatory roles in the Hippo pathway. Subsequent experiments validated PTPN12, a master regulator of oncogenic receptor tyrosine kinases (RTKs), as a previously unrecognized negative regulator of the Hippo pathway effectors, oncogenic YAP/TAZ, influencing breast cancer cell proliferation and migration. In summary, our findings offer valuable insights into the roles of PTPs in the Hippo signaling pathway, significantly contributing to our understanding of breast cancer biology and potential therapeutic strategies.

TMEM120B strengthens breast cancer cell stemness and accelerates chemotherapy resistance via β1-integrin/FAK-TAZ-mTOR signaling axis by binding to MYH9

BACKGROUND

Breast cancer stem cell (CSC) expansion results in tumor progression and chemoresistance; however, the modulation of CSC pluripotency remains unexplored. Transmembrane protein 120B (TMEM120B) is a newly discovered protein expressed in human tissues, especially in malignant tissues; however, its role in CSC expansion has not been studied. This study aimed to determine the role of TMEM120B in transcriptional coactivator with PDZ-binding motif (TAZ)-mediated CSC expansion and chemotherapy resistance.

METHODS

Both bioinformatics analysis and immunohistochemistry assays were performed to examine expression patterns of TMEM120B in lung, breast, gastric, colon, and ovarian cancers. Clinicopathological factors and overall survival were also evaluated. Next, colony formation assay, MTT assay, EdU assay, transwell assay, wound healing assay, flow cytometric analysis, sphere formation assay, western blotting analysis, mouse xenograft model analysis, RNA-sequencing assay, immunofluorescence assay, and reverse transcriptase-polymerase chain reaction were performed to investigate the effect of TMEM120B interaction on proliferation, invasion, stemness, chemotherapy sensitivity, and integrin/FAK/TAZ/mTOR activation. Further, liquid chromatography-tandem mass spectrometry analysis, GST pull-down assay, and immunoprecipitation assays were performed to evaluate the interactions between TMEM120B, myosin heavy chain 9 (MYH9), and CUL9.

RESULTS

TMEM120B expression was elevated in lung, breast, gastric, colon, and ovarian cancers. TMEM120B expression positively correlated with advanced TNM stage, lymph node metastasis, and poor prognosis. Overexpression of TMEM120B promoted breast cancer cell proliferation, invasion, and stemness by activating TAZ-mTOR signaling. TMEM120B directly bound to the coil-coil domain of MYH9, which accelerated the assembly of focal adhesions (FAs) and facilitated the translocation of TAZ. Furthermore, TMEM120B stabilized MYH9 by preventing its degradation by CUL9 in a ubiquitin-dependent manner. Overexpression of TMEM120B enhanced resistance to docetaxel and doxorubicin. Conversely, overexpression of TMEM120B-∆CCD delayed the formation of FAs, suppressed TAZ-mTOR signaling, and abrogated chemotherapy resistance. TMEM120B expression was elevated in breast cancer patients with poor treatment outcomes (Miller/Payne grades 1-2) than in those with better outcomes (Miller/Payne grades 3-5).

CONCLUSIONS

Our study reveals that TMEM120B bound to and stabilized MYH9 by preventing its degradation. This interaction activated the β1-integrin/FAK-TAZ-mTOR signaling axis, maintaining stemness and accelerating chemotherapy resistance.

Insight into the differential toxicity of PFOA and PFBA based on a 3D-cultured MDA-MB-231 cell model

Perfluoroalkyl substances (PFASs) are a category of high-concerned emerging contaminants which are suspected to correlate with various human adverse health outcomes including tumors. It is also a question whether short-chain PFASs are qualified alternatives under the regulation of long-chain PFASs. In this study, a three-dimensional (3D) culture system based on Gelatin methacrylate (GelMA) hydrogel matrix was used to investigate the impacts of 120-h perfluorooctanoic acid (PFOA) and perfluorobutanoic acid (PFBA) exposure of MDA-MB-231 cells. The results showed that PFOA exposure promoted the proliferation, migration, and invasion of MDA-MB-231 cells in an environmentally relevant concentration range (0.1 to 10 μM), exhibiting a clear malignant-promoting risk. In contrast, PFBA only showed a trend to induce non-invasive cell migration. Hippo/YAP signaling pathway was identified as the contributor to the differences between the two PFASs. PFOA but PFBA reduced YAP phosphorylation and increased the nuclear content of YAP, which further facilitated abundant key factors of epithelial-mesenchymal transition (EMT) process. Our results provided a new idea for the carcinogenicity of PFOA using a 3D-based paradigm. Although the effects by PFBA were much milder than PFOA in the current test duration, the cell model suitable for longer exposure is still necessary to better assess the safety of alternative short-chain PFASs.

Unleashing the Power of Yes-Associated Protein in Ferroptosis and Drug Resistance in Breast Cancer, with a Special Focus on Therapeutic Strategies

The YAP protein is a critical oncogenic mediator within the Hippo signaling pathway and has been implicated in various cancer types. In breast cancer, it frequently becomes activated, thereby contributing to developing drug-resistance mechanisms. Recent studies have underscored the intricate interplay between YAP and ferroptosis within the breast tumor microenvironment. YAP exerts a negative regulatory effect on ferroptosis, promoting cancer cell survival and drug resistance. This review offers a concise summary of the current understanding surrounding the interplay between the YAP pathway, ferroptosis, and drug-resistance mechanisms in both bulk tumor cells and cancer stem cells. We also explore the potential of natural compounds alone or in combination with anticancer therapies for targeting the YAP pathway in treating drug-resistant breast cancer. This approach holds the promise of enhancing the effectiveness of current treatments and paving the way for developing novel therapeutics.

Recent progress on the effect of extracellular matrix on occurrence and progression of breast cancer

Breast cancer (BC) metastasis is an enormous challenge targeting BC therapy. The extracellular matrix (ECM), the principal component of the BC metastasis niche, is the pivotal driver of breast tumor development, whose biochemical and biophysical characteristics have attracted widespread attention. Here, we review the biological effects of ECM constituents and the influence of ECM stiffness on BC metastasis and drug resistance. We provide an overview of the relative signal transduction mechanisms, existing metastasis models, and targeted drug strategies centered around ECM stiffness. It will shed light on exploring more underlying targets and developing specific drugs aimed at ECM utilizing biomimetic platforms, which are promising for breast cancer treatment.

The anticancer mechanism of action of selected polyphenols in triple-negative breast cancer (TNBC)

Breast cancer is a leadingcause of cancer-related deaths in women globally, with triple-negative breast cancer (TNBC) being an aggressive subtype that lacks targeted therapies and is associated with a poor prognosis. Polyphenols, naturally occurring compounds in plants, have been investigated as a potential therapeutic strategy for TNBC. This review provides an overview of the anticancer effects of polyphenols in TNBC and their mechanisms of action. Several polyphenols, including resveratrol, quercetin, kaempferol, genistein, epigallocatechin-3-gallate, apigenin, fisetin, hesperetin and luteolin, have been shown to inhibit TNBC cell proliferation, induce cell cycle arrest, promote apoptosis, and suppress migration/invasion in preclinical models. The molecular mechanisms underlying their anticancer effects involve the modulation of several signalling pathways, such as PI3K/Akt, MAPK, STATT, and NF-κB pathways. Polyphenols also exhibit synergistic effects with chemotherapy drugs, making them promising candidates for combination therapy. The review also highlights clinical trials investigating the potential use of polyphenols, individually or in combination therapy, against breast cancer. This review deepens the under-standing of the mechanism of action of respective polyphenols and provides valuable insights into the potential use of polyphenols as a therapeutic strategy for TNBC, and lays the groundwork for future research in this area.

The circadian clock protein Cryptochrome 1 is a direct target and feedback regulator of the Hippo pathway

Circadian clock controls daily behavior and physiology. The activity of various signaling pathways affects clock gene expression. Here, we show that the core circadian clock gene CRY1 is a direct target of the Hippo pathway effector YAP. YAP binds to TEADs and occupies the proximal promoter regions of CRY1, positively regulating its transcription. Interestingly, we further identified that CRY1 acts in a feedback loop to fine-tune Hippo pathway activation by modulating the expression of YAP and MOB1. Indeed, loss of CRY1 results in enhanced YAP activation. Consistently, we found that YAP levels and activity control clock gene expression and oscillation in synchronized cells. Furthermore, in breast cancer cells, CRY1 downregulation causes YAP/TAZ hyperactivation and enhanced DNA damage. Together, our findings provide a direct mechanistic link between the Hippo pathway and the circadian clock, where CRY1 and Hippo components form an orchestrated signaling network that influences cell growth and circadian rhythm.

YAP/TAZ: Molecular pathway and disease therapy

The Yes-associated protein and its transcriptional coactivator with PDZ-binding motif (YAP/TAZ) are two homologous transcriptional coactivators that lie at the center of a key regulatory network of Hippo, Wnt, GPCR, estrogen, mechanical, and metabolism signaling. YAP/TAZ influences the expressions of downstream genes and proteins as well as enzyme activity in metabolic cycles, cell proliferation, inflammatory factor expression, and the transdifferentiation of fibroblasts into myofibroblasts. YAP/TAZ can also be regulated through epigenetic regulation and posttranslational modifications. Consequently, the regulatory function of these mechanisms implicates YAP/TAZ in the pathogenesis of metabolism-related diseases, atherosclerosis, fibrosis, and the delicate equilibrium between cancer progression and organ regeneration. As such, there arises a pressing need for thorough investigation of YAP/TAZ in clinical settings. In this paper, we aim to elucidate the signaling pathways that regulate YAP/TAZ and explore the mechanisms of YAP/TAZ-induce diseases and their potential therapeutic interventions. Furthermore, we summarize the current clinical studies investigating treatments targeting YAP/TAZ. We also address the limitations of existing research on YAP/TAZ and propose future directions for research. In conclusion, this review aims to provide fresh insights into the signaling mediated by YAP/TAZ and identify potential therapeutic targets to present innovative solutions to overcome the challenges associated with YAP/TAZ.

HERC3 promotes YAP/TAZ stability and tumorigenesis independently of its ubiquitin ligase activity

YAP/TAZ transcriptional co-activators play pivotal roles in tumorigenesis. In the Hippo pathway, diverse signals activate the MST-LATS kinase cascade that leads to YAP/TAZ phosphorylation, and subsequent ubiquitination and proteasomal degradation by SCFβ-TrCP . When the MST-LATS kinase cascade is inactive, unphosphorylated or dephosphorylated YAP/TAZ translocate into the nucleus to mediate TEAD-dependent gene transcription. Hippo signaling-independent YAP/TAZ activation in human malignancies has also been observed, yet the mechanism remains largely elusive. Here, we report that the ubiquitin E3 ligase HERC3 can promote YAP/TAZ activation independently of its enzymatic activity. HERC3 directly binds to β-TrCP, blocks its interaction with YAP/TAZ, and thus prevents YAP/TAZ ubiquitination and degradation. Expression levels of HERC3 correlate with YAP/TAZ protein levels and expression of YAP/TAZ target genes in breast tumor cells and tissues. Accordingly, knockdown of HERC3 expression ameliorates tumorigenesis of breast cancer cells. Our results establish HERC3 as a critical regulator of the YAP/TAZ stability and a potential therapeutic target for breast cancer.

HMGB3 Targeted by miR-145-5p Impacts Proliferation, Migration, Invasion, and Apoptosis of Breast Cancer Cells

This study focused on the investigation into how HMGB3 works in breast cancer (BC) progression. Firstly, we analyzed the relationship between HMGB3 and BC patients through the TCGA database. We performed qRT-PCR for determining the HMGB3 mRNA level and Western blot for detecting the protein level of HMGB3 in BC cell lines. CCK-8, flow cytometry, transwell, and wound healing assays were utilized to detect the effect of HMGB3 on BC cell phenotypes. Next, the prediction of the binding site shared by miR-145-5p and HMGB3 was performed by the bioinformatics method. The targeting relationship between miR-145-5p and HMGB3 was validated by using dual-luciferase assay. Finally, rescue experiments were employed for assessing the effect of the miR-145-5p/HMGB3 axis on BC cells. HMGB3 was demonstrated to have a high-level expression in BC cell lines and facilitated BC progression. On the contrary, miR-145-5p was shown a low-level expression in BC cell lines, which could target HMGB3. miR-145-5p restrained the proliferation, migration, and invasion of BC cells via inhibiting HMGB3.

OTUB2 Regulates YAP1/TAZ to Promotes the Progression of Esophageal Squamous Cell Carcinoma

Objective

The effects of Otubain-2 (OTUB2) on the proliferation, invasion, and migration of esophageal squamous cell carcinoma (ESCC) were investigated by interfering with OTUB2 expression.

Methods

Bioinformatics analysis was used to analyze OTUB2 expression in esophageal carcinoma and interactions between OTUB2 and YAP1/TAZ. Paraffin-embedded ESCC tissues (n = 183) were selected for immunohistochemical staining to detect OTUB2, YAP1, TAZ, CTGF and their relationship with clinicopathological parameters, then the survival prognosis of ESCC patients was analyzed. Immunofluorescence, western blotting, and qRT-PCR were used to evaluate OTUB2 in ESCC cell lines. Cell lines with the highest expression of OTUB2 were transfected with lentivirus to knockdown OTUB2 levels. Changes in KYSE150 cell proliferation, migration, and invasion were measured using CCK-8, wound healing, and clone formation assays. The Transwell test and flow cytometry identified OTUB2 targets and explored roles and mechanisms involved in ESCC. Effects of OTUB2 on YAP1/TAZ signaling were also observed.

Results

Bioinformatics analysis revealed OTUB2 was highly expressed in esophageal cancer and was associated with YAP1/TAZ. Immunohistochemistry showed that OTUB2 expression was increased in ESCC samples compared to parcancerous tissue. YAP1 and TAZ were higher expression in ESCC tissues, mainly localized in the nucleus. Compared with controls, the proliferation, migration, and invasion ability of KYSE150 cells after OTUB2 knockdown were significantly reduced (P < 0.05). The protein expression levels of YAP1, TAZ and CTGF decreased after knocking down the expression of OTUB2 (P < 0.05). OTUB2 knockdown in ESCC cell lines suppressed YAP1/TAZ signaling.

Conclusions

OTUB2 regulated the protein expression of YAP1/TAZ to promote cell proliferation, migration, invasion, and tumor development. Therefore, OTUB2 may represent a biomarker for ESCC and a potential target for ESCC treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12575-022-00169-9.

Single-cell sequencing reveals the antifibrotic effects of YAP/TAZ in systemic sclerosis

Systemic sclerosis (SSc) is a heterogeneous disease with skin fibrosis. Yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) is associated with fibrotic response. This work attempted to determine the precise mechanism of YAP/TAZ in SSc. Single-cell sequencing (scRNA-seq) was used to analyse the differential gene expression between SSc patients and healthy volunteers, showing that the YAP/TAZ signalling pathway was enriched in the fibroblasts of SSc patients. Subsequently, enzyme-linked immunosorbent assay and immunohistochemical analyses were conducted to examine the levels of YAP and TAZ in mild and severe SSc patients. YAP and TAZ were highly expressed in the serum and skin tissues of mild and severe SSc patients, especially severe SSc patients. Additionally, an SSc mouse model was induced by bleomycin, and the impacts of YAP/TAZ knockdown on the pathological changes in skin and lung tissues were detected by haematoxylin and eosin staining and Masson staining. Knockdown of YAP and TAZ inhibited α-SMA mRNA and protein expression in skin and lung tissues of SSc mice. Inhibition of YAP and TAZ reduced skin inflammation and thickness and repressed lung inflammation and fibrosis in SSc mice. Importantly, knockdown of YAP and TAZ synergistically inhibited inflammation and fibrosis in skin and lung tissues in SSc mice. In conclusion, this work demonstrated that knockdown of YAP and TAZ exerted a synergistic effect on alleviating SSc in mice. Thus, this work suggests that YAP/TAZ is a potential target for SSc treatment.

Role of Yes-Associated Protein in Psoriasis and Skin Tumor Pathogenesis

Psoriasis and skin tumors (such as basal cell carcinoma, squamous cell carcinoma, and melanoma) are chronic diseases that endanger physical and mental health, and yet the causes are largely unknown and treatment options limited. The development of targeted drugs requires a better understanding of the exact pathogenesis of these diseases, and Yes-associated protein (YAP), a member of the Hippo signaling pathway, is believed to play an important role. Psoriasis and skin tumors are characterized by excessive cell proliferation, abnormal differentiation, vasodilation, and proliferation. Here, we review the literature related to YAP-associated disease mechanisms and discuss the latest research. YAP regulates cell apoptosis, proliferation, and differentiation; inhibits cell density and intercellular contacts and angiogenesis; and maintains the three-dimensional structure of the skin. These mechanisms may be associated with the occurrence and development of psoriasis and skin tumors. The results of recent studies have shown that YAP expression is increased in psoriasis and skin tumors. High expression of YAP in psoriasis and skin tumors may indicate its positive functions in skin inflammation and malignancies and may play an important role in disease pathogenesis. The study of new drugs targeting YAP can provide novel approaches for the treatment of skin diseases.

Mechanistic insights expatiating the biological role and regulatory implications of estrogen and HER2 in breast cancer metastasis

Breast cancer (BCa) has become the leading cause of death in women worldwide. Irrespective of advancement in cancer treatments, e.g., surgery, radiation, chemotherapy, hormonal therapy, immunotherapy, and targeted therapy, recurrence leading to metastasis poses the greatest threat in BCa management. BCa receptors estrogen (ER), progesterone (PR), and human epidermal growth factor receptor-2 (HER2) hold significant reputations as prognostic and predictive biomarkers in therapeutic decision-making. Under normal physiological conditions, these receptors modulate critical biological functions, e.g., cell migration, proliferation, and apoptosis events, etc. However, aberrant expression causes deviations, triggering signaling course to adapt permanent switching "ON" mode. The later events induce rapid and unrestrained proliferation leading to cancer. As conventional ways of cancer management ultimately lead to resistance; therefore, recently targeted therapies have been extensively studied to conquer resistance. Targeting various small molecules in downstream signaling has become an area of interest in scientific society. The severity of cancer converts many folds soon after it takes on a migratory approach that eventually commences metastasis. Cancer migration comprises protrusion of cytoplasm at the leading edge of the migration forward-facing, establishing adhesions with the basic cell-matrix, disassembly of the adhesions at the back end of the cell, and actin-myosin fiber contractions to pull the bulk of the cytoplasm forward. On the other hand, metastatic progression comprises a cascade of events, including invasion, migration, and establishment of tumor microenvironment. The progression of BCa from early stage to metastatic development causes remarkable heterogeneity. Interference at any explicit level could hamper the process, and it has thus become an area of interest for scientists. Metastasis is the ultimate cause of spreading tumor cells to invade distant organs. Recently small molecule inhibitors of protein tyrosine kinases, which can cross the blood-brain barrier, have become a center point of research for investigators in developing novel treatment strategies against BCa management.

Utilizing the Hippo pathway as a therapeutic target for combating endocrine-resistant breast cancer

Drug resistance is always a great obstacle in any endocrine therapy of breast cancer. Although the combination of endocrine therapy and targeted therapy has been shown to significantly improve prognosis, refractory endocrine resistance is still common. Dysregulation of the Hippo pathway is often related to the occurrence and the development of many tumors. Targeted therapies of this pathway have played important roles in the study of triple negative breast cancer (TNBC). Targeting the Hippo pathway in combination with chemotherapy or other targeted therapies has been shown to significantly improve specific antitumor effects and reduce cancer antidrug resistance. Further exploration has shown that the Hippo pathway is closely related to endocrine resistance, and it plays a "co-correlation point" role in numerous pathways involving endocrine resistance, including related pathways in breast cancer stem cells (BCSCs). Agents and miRNAs targeting the components of the Hippo pathway are expected to significantly enhance the sensitivity of breast cancer cells to endocrine therapy. This review initially explains the possible mechanism of the Hippo pathway in combating endocrine resistance, and it concludes by recommending endocrine therapy in combination with therapies targeting the Hippo pathway in the study of endocrine-resistant breast cancers.

The Hippo Pathway: A Master Regulatory Network Important in Cancer

The Hippo pathway is pervasively activated and has been well recognized to play critical roles in human cancer. The deregulation of Hippo signaling involved in cancer development, progression, and resistance to cancer treatment have been confirmed in several human cancers. Its biological significance and deregulation in cancer have drawn increasing interest in the past few years. A fundamental understanding of the complexity of the Hippo pathway in cancer is crucial for improving future clinical interventions and therapy for cancers. In this review, we try to clarify the complex regulation and function of the Hippo signaling network in cancer development, including its role in signal transduction, metabolic regulation, and tumor development, as well as tumor therapies targeting the Hippo pathway.