Tgfbr2 inactivation facilitates cellular plasticity and development of Pten-null prostate cancer

ATXN3 promotes prostate cancer progression by stabilizing YAP

BACKGROUND

Prostate cancer (PC) is the most common neoplasm and is the second leading cause of cancer-related deaths in men worldwide. The Hippo tumor suppressor pathway is highly conserved in mammals and plays an important role in carcinogenesis. YAP is one of major key effectors of the Hippo pathway. However, the mechanism supporting abnormal YAP expression in PC remains to be characterized.

METHODS

Western blot was used to measure the protein expression of ATXN3 and YAP, while the YAP target genes were measured by real-time PCR. CCK8 assay was used to detect cell viability; transwell invasion assay was used to measure the invasion ability of PC. The xeno-graft tumor model was used for in vivo study. Protein stability assay was used to detect YAP protein degradation. Immuno-precipitation assay was used to detect the interaction domain between YAP and ATXN3. The ubiquitin-based Immuno-precipitation assays were used to detect the specific ubiquitination manner happened on YAP.

RESULTS

In the present study, we identified ATXN3, a DUB enzyme in the ubiquitin-specific proteases family, as a bona fide deubiquitylase of YAP in PC. ATXN3 was shown to interact with, deubiquitylate, and stabilize YAP in a deubiquitylation activity-dependent manner. Depletion of ATXN3 decreased the YAP protein level and the expression of YAP/TEAD target genes in PC, including CTGF, ANKRD1 and CYR61. Further mechanistic study revealed that the Josephin domain of ATXN3 interacted with the WW domain of YAP. ATXN3 stabilized YAP protein via inhibiting K48-specific poly-ubiquitination process on YAP protein. In addition, ATXN3 depletion significantly decreased PC cell proliferation, invasion and stem-like properties. The effects induced by ATXN3 depletion could be rescued by further YAP overexpression.

CONCLUSIONS

In general, our findings establish a previously undocumented catalytic role for ATXN3 as a deubiquitinating enzyme of YAP and provides a possible target for the therapy of PC. Video Abstract.

Plasticity within aldehyde dehydrogenase-positive cells determines prostate cancer radiosensitivity

Tumor heterogeneity and cellular plasticity are key determinants of tumor progression, metastatic spread and therapy response driven by the cancer stem cell (CSC) population. Within the present study, we analyzed irradiation-induced plasticity within the aldehyde dehydrogenase (ALDH)-positive population in prostate cancer (PCa). The radiosensitivity of xenograft tumors derived from ALDH+ and ALDH- cells was determined with local tumor control analyses and demonstrated different dose-response profiles, time to relapse and focal adhesion signaling. The transcriptional heterogeneity was analyzed in pools of ten DU145 and PC3 cells with multiplex gene expression analyses and illustrated a higher degree of heterogeneity within the ALDH+ population that even increases upon irradiation in comparison to ALDH- cells. Phenotypic conversion and clonal competition were analyzed with fluorescence protein-labeled cells to distinguish cellular origins in competitive 3D cultures and xenograft tumors. We found that the ALDH+ population outcompetes ALDH- cells and drives tumor growth, in particular upon irradiation. The observed dynamics of the cellular state compositions between ALDH+ and ALDH- cells in vivo before and after tumor irradiation was reproduced by a probabilistic Markov compartment model that incorporates cellular plasticity, clonal competition and phenotype-specific radiosensitivities. Transcriptional analyses indicate that the cellular conversion from ALDH- into ALDH+ cells within xenograft tumors under therapeutic pressure was partially mediated through induction of the transcriptional repressor SNAI2. In summary, irradiation-induced cellular conversion events are present in xenograft tumors derived from PCa cells and may be responsible for radiotherapy failure.

Long non-‑coding RNA SNHG16 functions as a tumor activator by sponging miR‑373‑3p to regulate the TGF‑β‑R2/SMAD pathway in prostate cancer

Long non‑coding RNAs (lncRNAs) are involved in the pathogenesis of prostate cancer (PCa) as competitive endogenous RNA. The present study aimed to investigate the molecular mech--anisms of lncRNA small nucleolar RNA host gene 16 (SNHG16) in the proliferation and metastasis of PCa cells. Cancer tissues and adjacent normal tissues were collected from 80 patients with PCa who did not receive any treatment. Reverse transcription‑quantitative PCR analysis was performed to detect the expression levels of SNHG16, hsa‑microRNA (miRNA/miR)‑373‑3p and transforming growth factor‑β receptor type 2 (TGF‑β‑R2), and Spearman's correlation coefficient analysis was performed to assess the correlations between these molecules. Furthermore, the effects of SNHG16 knockdown and overexpression on the biological functions of DU‑145 PCa cells and TGF‑β‑R2/SMAD signaling were analyzed. The dual‑luciferase reporter assay was performed to assess the associations between SNHG16 and miR‑373‑3p, and TGF‑β‑R2 and miR‑373‑3p, the effects of which were verified via rescue experiments. The results demonstrated that the expression levels of SNHG16 and TGF‑β‑R2 were significantly upregulated in PCa tissues, whereas miR‑373‑3p expression was significantly downregulated (P<0.001). In addition, negative correlations were observed between SNHG16 and miR‑373‑3p (rho, ‑0.631) and miR‑373‑3p and TGF‑β‑R2 (rho, ‑0.516). Overexpression of SNHG16 significantly promoted the proliferation, migration and invasion of PCa cells (P<0.05), and significantly increased the protein expression levels of TGF‑β‑R2, phosphorylated (p)‑SMAD2, p‑SMAD3, c‑Myc and E2F4 (P<0.001). Notably, the results revealed that miR‑373‑3p is a target of SNHG16, and miR‑373‑3p knockdown rescued short hairpin (sh)‑SNHG16‑suppressed cellular functions by promoting TGF‑β‑R2/SMAD signaling. The results also revealed that miR‑373‑3p targets TGF‑β‑R2. Notably, transfection with miR‑373‑3p inhibitor rescued sh‑TGF‑β‑R2‑suppressed cell proliferation and migration. Taken together, the results of the present study suggest that SNHG16 promotes the proliferation and migration of PCa cells by targeting the miR‑373‑3p/TGF‑β‑R2/SMAD axis.

Imbalance of TGF-β1/BMP-7 pathways induced by M2-polarized macrophages promotes hepatocellular carcinoma aggressiveness

The transforming growth factor-beta (TGF-β) signaling pathway is the predominant cytokine signaling pathway in the development and progression of hepatocellular carcinoma (HCC). Bone morphogenetic protein (BMP), another member of the TGF-β superfamily, has been frequently found to participate in crosstalk with the TGF-β pathway. However, the complex interaction between the TGF-β and BMP pathways has not been fully elucidated in HCC. We found that the imbalance of TGF-β1/BMP-7 pathways was associated with aggressive pathological features and poor clinical outcomes in HCC. The induction of the imbalance of TGF-β1/BMP-7 pathways in HCC cells could significantly promote HCC cell invasion and stemness by increasing inhibitor of differentiation 1 (ID1) expression. We also found that the microRNA (miR)-17-92 cluster, originating from the extracellular vesicles (EVs) of M2-polarized tumor-associated macrophages (M2-TAMs), stimulated the imbalance of TGF-β1/BMP-7 pathways in HCC cells by inducing TGF-β type II receptor (TGFBR2) post-transcriptional silencing and inhibiting activin A receptor type 1 (ACVR1) post-translational ubiquitylation by targeting Smad ubiquitylation regulatory factor 1 (Smurf1). In vivo, short hairpin (sh)-MIR17HG and ACVR1 inhibitors profoundly attenuated HCC cell growth and metastasis by rectifying the imbalance of TGF-β1/BMP-7 pathways. Therefore, we proposed that the imbalance of TGF-β1/BMP-7 pathways is a feasible prognostic biomarker and recovering the imbalance of TGF-β1/BMP-7 pathways might be a potential therapeutic strategy for HCC.

Regulation of stem/progenitor cell maintenance by BMP5 in prostate homeostasis and cancer initiation

Tissue homeostasis relies on the fine regulation between stem and progenitor cell maintenance and lineage commitment. In the adult prostate, stem cells have been identified in both basal and luminal cell compartments. However, basal stem/progenitor cell homeostasis is still poorly understood. We show that basal stem/progenitor cell maintenance is regulated by a balance between BMP5 self-renewal signal and GATA3 dampening activity. Deleting Gata3 enhances adult prostate stem/progenitor cells self-renewal capacity in both organoid and allograft assays. This phenotype results from a local increase in BMP5 activity in basal cells as shown by the impaired self-renewal capacity of Bmp5-deficient stem/progenitor cells. Strikingly, Bmp5 gene inactivation or BMP signaling inhibition with a small molecule inhibitor are also sufficient to delay prostate and skin cancer initiation of Pten-deficient mice. Together, these results establish BMP5 as a key regulator of basal prostate stem cell homeostasis and identifies a potential therapeutic approach against Pten-deficient cancers.

Opposing roles and potential antagonistic mechanism between TGF-β and BMP pathways: Implications for cancer progression

The transforming growth factor β (TGF-β) superfamily participates in tumour proliferation, apoptosis, differentiation, migration, invasion, immune evasion and extracellular matrix remodelling. Genetic deficiency in distinct components of TGF-β and BMP-induced signalling pathways or their excessive activation has been reported to regulate the development and progression of some cancers. As more in-depth studies about this superfamily have been conducted, more evidence suggests that the TGF-β and BMP pathways play an opposing role. The cross-talk of these 2 pathways has been widely studied in kidney disease and bone formation, and the opposing effects have also been observed in some cancers. However, the antagonistic mechanisms are still insufficiently investigated in cancer. In this review, we aim to display more evidences and possible mechanisms accounting for the antagonism between these 2 pathways, which might provide some clues for further study in cancer.

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Describe the basics of TGF-β and BMP signalling

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Summarize the potential mechanisms accounting for the antagonism between TGF-β and BMP pathways

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Provide some evidence about the antagonistic effects between pathways observed in some cancers

TMEFF1 overexpression and its mechanism for tumor promotion in ovarian cancer

Background

Transmembrane protein with epidermal growth factor-like and two follistatin-like domains 1 (TMEFF1) has an anticarcinogenic effect in brain tumors. However, little is known about the role of TMEFF1 in epithelial ovarian cancer (EOC).

Materials and methods

TMEFF1 expression in EOC was detected by immunohistochemistry; its relationship with clinical pathological parameters and its influence on prognosis were analyzed. The MTT, scratch, Transwell assays, and flow cytometry were used to assess the malignant behavior of ovarian cancer cell. Changes in node proteins in MAPK and PI3K/AKT signaling pathways and the expression of epithelial–mesenchymal transformation markers were measured by Western blot. The regulatory effect of p53 on TMEFF1 was verified by chromatin immunoprecipitation (ChIP) assay and Western blot.

Results

TMEFF1 expression was higher in the EOC group than in the borderline and benign tumor groups and normal ovary group; its high expression was significantly related to International Federation of Gynecology and Obstetrics stage (P=0.024) and independently predicted shorter overall survival (P<0.01). TMEFF1 overexpression in ovarian cancer cells induced increased cellular proliferation, migration, and invasion but reduced apoptosis. In addition, the percentage of phosphorylated node proteins in MAPK and PI3K/AKT signaling pathways increased significantly. The expression of E-cadherin decreased but that of vimentin and N-cadherin increased. After the addition of MAPK (PD98059) and PI3K (GDC-0941) pathway inhibitors, ovarian cancer cells overexpressing TMEFF1 showed suppressed malignant behavior. TMEFF1 protein expression in an ovarian cancer cell lines (CAOV3 and ES-2) was downregulated after the inhibition of TP53. The transcription factor, p53, bound the promoter region of the TMEFF1 gene according to ChIP.

Conclusion

TMEFF1 is a carcinogenic gene in ovarian cancer and can be regulated by p53 transcription. Through MAPK and PI3K/AKT signaling pathways, TMEFF1 promotes the malignant behavior in EOC. Therefore, TMEFF1 may be considered as a potential therapeutic target for ovarian cancer.

Neural Transcription Factors in Disease Progression

Progression to the malignant state is fundamentally dependent on transcriptional regulation in cancer cells. Optimum abundance of cell cycle proteins, angiogenesis factors, immune evasion markers, etc. is needed for proliferation, metastasis or resistance to treatment. Therefore, dysregulation of transcription factors can compromise the normal prostate transcriptional network and contribute to malignant disease progression.The androgen receptor (AR) is considered to be a key transcription factor in prostate cancer (PCa) development and progression. Consequently, androgen pathway inhibitors (APIs) are currently the mainstay in PCa treatment, especially in castration-resistant prostate cancer (CRPC). However, emerging evidence suggests that with increased administration of potent APIs, prostate cancer can progress to a highly aggressive disease that morphologically resembles small cell carcinoma, which is referred to as neuroendocrine prostate cancer (NEPC), treatment-induced or treatment-emergent small cell prostate cancer. This chapter will review how neuronal transcription factors play a part in inducing a plastic stage in prostate cancer cells that eventually progresses to a more aggressive state such as NEPC.