The Multifaceted Role of FUT8 in Tumorigenesis: From Pathways to Potential Clinical Applications.

FUT8, the sole glycosyltransferase responsible for N-glycan core fucosylation, plays a crucial role in tumorigenesis and development. Aberrant FUT8 expression disrupts the function of critical cellular components and triggers the abnormality of tumor signaling pathways, leading to malignant transformations such as proliferation, invasion, metastasis, and immunosuppression. The association between FUT8 and unfavorable outcomes in various tumors underscores its potential as a valuable diagnostic marker. Given the remarkable variation in biological functions and regulatory mechanisms of FUT8 across different tumor types, gaining a comprehensive understanding of its complexity is imperative. Here, we review how FUT8 plays roles in tumorigenesis and development, and how this outcome could be utilized to develop potential clinical therapies for tumors.

Implication of BAG5 downregulation in metabolic reprogramming of cisplatin-resistant ovarian cancer cells via mTORC2 signaling pathway.

Ovarian cancer is the most frequent cause of gynecologic malignancies associated death. Primary or acquired cisplatin resistance is frequently occurred during ovarian cancer therapy. Cancer stem cells (CSC) tend to form minimal residual disease after chemotherapy and are implicated in relapse. The ability of cancer cells to reprogram their metabolism has recently been related with maintenance of CSC and resistance to chemotherapies. The current study found that BAG5 expression was decreased in cisplatin-resistant ovarian cancer cells and clinical tissues. Our data demonstrated that BAG5 knockdown was implicated in metabolic reprogramming and maintenance of cancer stem cell (CSC)-like features of ovarian cancer cells via regulation of Rictor and subsequent mTORC2 signaling pathway. In addition, the current study demonstrated that Bcl6 upregulation was responsible for repression of BAG5 transactivation via recruitment on the BAG5 promoter in cisplatin-resistant ovarian cancer. The current study also demonstrated reverse correlations between BAG5 and Bcl6, BAG5 and Rictor in ovarian serous adenocarcinoma tissues. Collectively, the current study identified the implication of Bcl6/BAG5/Rictor-mTORC2 signaling pathway in metabolic reprograming and maintenance of CSC-like features in cisplatin-resistant ovarian cancer cells. Therefore, further studies on the mechanism underlying regulation of metabolic reprogramming and CSC-like characteristics of cisplatin-resistant ovarian cancer cells may contribute to the establishment of novel therapeutic strategy for cisplatin-resistance.

BAG3 epigenetically regulates GALNT10 expression via WDR5 and facilitates the stem cell-like properties of platin-resistant ovarian cancer cells.

Ovarian cancer is the most lethal gynecologic malignant cancer, frequently due to its late diagnosis and high recurrence. Cancer stem cells (CSCs) from different malignancies including ovarian cancer have been linked to chemotherapy resistance and poor prognosis. Therefore, identifying the molecular mechanisms mediating therapy resistance is urgent to finding novel targets for therapy-resistant tumors. Aberrant O-glycosylation ascribed to subtle alteration of GALNT family members during malignant transformation facilitate metastasis in various cancers. The current study demonstrated that BAG3 was upregulated in platin-resistant ovarian cancer tissues and cells, and high BAG3 predicted dismal disease-free survival of patients with ovarian cancer. In addition, the current study showed that BAG3 facilitated CSC-like properties of ovarian cancer cells via regulation of GALTN10. In a term of mechanism, BAG3 epigenetically regulated GALNT10 transactivation via histone H3 lysine 4 (H3K4) presenter WDR5. We demonstrated that WDR5 increased H3K4 trimethylation (H3K4me3) modification at the promoter regions of GALNT10, facilitating recruitment of transcription factor ZBTB2 to the GALNT10 promoter. Collectively, our study uncovers an epigenetic upregulation of GALNT10 by BAG3 via WDR5 to facilitate CSCs of platin-resistant ovarian cancers, providing additional information for further identification of attractive targets with therapeutic significance in platin-resistant ovarian cancer.

TRIM29 alters bioenergetics of pancreatic cancer cells via cooperation of miR-2355-3p and DDX3X recruitment to AK4 transcript.

TRIM29 is dysregulated in pancreatic cancer and implicated in maintenance of stem-cell-like characters of pancreatic cancer cells. However, the exact mechanisms underlying oncogenic function of TRIM29 in pancreatic cancer cells remain largely unclarified. Using a global screening procedure, the current study found that adenylate kinase 4 (AK4) was profoundly reduced by TRIM29 knockdown. In addition, our data demonstrated that TRIM29 knockdown altered bioenergetics and suppressed proliferation and invasion of pancreatic cancer cells via downregulation of AK4 at the posttranscriptional level. The current study demonstrated that upregulation of microRNA-2355-3p (miR-2355-3p) upregulated AK4 expression via facilitating DDX3X recruitment to the AK4 transcript, and TRIM29 knockdown thereby destabilized the AK4 transcript via miR-2355-3p downregulation. Collectively, our study uncovers posttranscriptional stabilization of the AK4 transcript by miR-2355-3p interaction to facilitate DDX3X recruitment. Regulation of AK4 by TRIM29 via miR-2355-3p thereby provides additional information for further identification of attractive targets for therapy with pancreatic cancer.

Single-nucleotide methylation specifically represses type I interferon in antiviral innate immunity.

Frequent outbreaks of viruses have caused a serious threat to public health. Previous evidence has revealed that DNA methylation is correlated with viral infections, but its role in innate immunity remains poorly investigated. Additionally, DNA methylation inhibitors promote IFN-I by upregulating endogenous retrovirus; however, studies of intrinsically demethylated tumors do not support this conclusion. This study found that Uhrf1 deficiency in myeloid cells significantly upregulated Ifnb expression, increasing resistance to viral infection. We performed whole-genome bisulfite sequencing and found that a single-nucleotide methylation site in the Ifnb promoter region disrupted IRF3 recruitment. We used site-specific mutant knock-in mice and a region-specific demethylation tool to confirm that this methylated site plays a critical role in regulating Ifnb expression and antiviral responses. These findings provide essential insight into DNA methylation in the regulation of the innate antiviral immune response.

m6A-YTHDF1-mediated TRIM29 upregulation facilitates the stem cell-like phenotype of cisplatin-resistant ovarian cancer cells.

Ovarian cancer is the deadliest gynaecologic malignancy, and the five-year survival rate of patients is less than 35% worldwide. Cancer stem cells (CSCs) are a population of cells with stem-like characteristics that are thought to cause chemoresistance and recurrence. TRIM29 is aberrantly expressed in various cancers and associated with cancer development and progression. Previous studies showed that the upregulation of TRIM29 expression in pancreatic cancer is related to stem-like characteristics. However, the role of TRIM29 in ovarian cancer is poorly understood. In this study, we found that TRIM29 expression was increased at the translational level in both the cisplatin-resistant ovarian cancer cells and clinical tissues. Increased TRIM29 expression was associated with a poor prognosis of patients with ovarian cancer. In addition, TRIM29 could enhance the CSC-like characteristics of the cisplatin-resistant ovarian cancer cells. Recruitment of YTHDF1 to m6A-modified TRIM29 was involved in promoting TRIM29 translation in the cisplatin-resistant ovarian cancer cells. Knockdown of YTHDF1 suppressed the CSC-like characteristics of the cisplatin-resistant ovarian cancer cells, which could be rescued by ectopic expression of TRIM29. This study suggests TRIM29 may act as an oncogene to promote the CSC-like features of cisplatin-resistant ovarian cancer in an m6A-YTHDF1-dependent manner. Due to the roles of TRIM29 and YTHDF1 in the promotion of CSC-like features, they may become potential therapeutic targets to combat the recurrence of ovarian cancer.

ISG15 suppresses translation of ABCC2 via ISGylation of hnRNPA2B1 and enhances drug sensitivity in cisplatin resistant ovarian cancer cells.

Cisplatin-based chemotherapies have long been considered as a standard chemotherapy in ovarian cancer. However, cisplatin resistance restricts beneficial therapy for patients with ovarian cancer. The ubiquitin-like protein interferon-stimulated gene 15 (ISG15) encodes a 15-kDa protein, that is implicated in the post-translational modification of diverse proteins. In this work, we found that ISG15 was downregulated in cisplatin resistant tissues and cell lines of ovarian cancer. Functional studies demonstrated that overexpression of wild type (WT) ISG15, but not nonISGylatable (Mut) ISG15 increased cell responses to cisplatin in resistant ovarian cancer cells. Furthermore, we found that WT ISG15 decreased ABCC2 expression at the protein level. Importantly, overexpression of ABCC2 blocked sensitizing effect of ISG15 on cisplatin. In addition, we identified that hnRNPA2B1 was recruited to 5'UTR of ABCC2 mRNA and promoted its translation, which was blocked by ISG15. We further demonstrated that hnRNPA2B1 could be ISGylated, and ISGylation blocked its recruitment to ABCC2 mRNA, thereby suppressed translation of ABCC2. Altogether, our data support targeting ISG15 might be a potential therapeutic strategy for patients with cisplatin-resistant ovarian cancer.

Loss of TRIM29 suppresses cancer stem cell-like characteristics of PDACs via accelerating ISG15 degradation.

TRIM family proteins are defined as E3 ubiquitin ligases because of their RING-finger domains. The ubiquitin-like protein interferon-stimulated gene 15 (ISG15) encodes a 15-kDa protein, that is implicated in the posttranslational modification of diverse proteins. Both TRIM29 and ISG15 play both pro-tumoral and anti-tumoral functions in cancer cells derived from different histology. In the current study, we demonstrated that correlation expression of TRIM29 and ISG15 in pancreatic ductal adenocarcinomas (PDACs). The current study demonstrated that TRIM29 knockdown destabilized ISG15 protein via promoting its processing by calpain 3 (CAPN3). Importantly, the current study found that TRIM29 knockdown suppressed cancer stem cell-like features of PDACs, which can be rescued by ISG15 independent of its conjugation function. In addition, the current study demonstrated that extracellular free ISG15 played an important role in maintenance of cancer stem cell-like features of PDACs. Thereby, the current study displayed a novel mechanism by which TRIM29 modulates ISG15 stability via CAPN3-mediated processing, and subsequently extracellular ISG15 maintains the cancer stem cell-like features of PDAC via autocrine mode of action.

p53-dependent transcriptional suppression of BAG3 protects cells against metabolic stress via facilitation of p53 accumulation.

Solid tumour frequently undergoes metabolic stress during tumour development because of inadequate blood supply and the high nutrient expenditure. p53 is activated by glucose limitation and maintains cell survival via triggering metabolic checkpoint. However, the exact downstream contributors are not completely identified. BAG3 is a cochaperone with multiple cellular functions and is implicated in metabolic reprogramming of pancreatic cancer cells. The current study demonstrated that glucose limitation transcriptionally suppressed BAG3 expression in a p53-dependent manner. Importantly, hinderance of its down-regulation compromised cellular adaptation to metabolic stress triggered by glucose insufficiency, supporting that BAG3 might be one of p53 downstream contributors for cellular adaptation to metabolic stress. Our data showed that ectopic BAG3 expression suppressed p53 accumulation via direct interaction under metabolic stress. Thereby, the current study highlights the significance of p53-mediated BAG3 suppression in cellular adaptation to metabolic stress via facilitating p53 accumulation.

BAG3-positive pancreatic stellate cells promote migration and invasion of pancreatic ductal adenocarcinoma.

BAG3 is constitutively expressed in multiple types of cancer cells and its high expression is associated with tumour progression and poor prognosis of PDAC. However, little is known about the role of BAG3 in the regulation of stromal microenvironment of PDAC. The current study demonstrated that beside PDAC tumour cells, BAG3 was also expressed in some activated stroma cells in PDAC tissue, as well as in activated PSCs. In addition, the current study demonstrated that BAG3 expression in PSCs was involved in maintenance of PSCs activation and promotion of PDACs invasion via releasing multiple cytokines. The current study demonstrated that BAG3-positive PSCs promoted invasion of PDACs via IL-8, MCP1, TGF-ß2 and IGFBP2 in a paracrine manner. Furthermore, BAG3 sustained PSCs activation through IL-6, TGF-ß2 and IGFBP2 in an autocrine manner. Thereby, the current study provides a new insight into the involvement of BAG3 in remodelling of stromal microenvironment favourable for malignant progression of PDAC, indicating that BAG3 might serve as a potential target for anti-fibrosis of PDAC.

Sestrin 2 protects against metabolic stress in a p53-independent manner.

Glucose limitation activates p53, which functions as an adaptive response to maintain cell survival. However, p53 is frequently deleted or mutated in a variety of tumors, while most cancer cells can acclimatize themselves to metabolically unfavorable surrounding, indicating that alternative mechanisms other than p53 transactivation underly adaptive response of cancer cells with p53 deletion or mutation to metabolically hostile environment. Sestrin 2 (SESN2) is a p53 downstream target, which plays a protective role against various stressful stimuli, such as genotoxic, energetic, and oxidative stress. In the current study, we demonstrated that SESN2 transcript was stabilized by glucose limitation at the posttranscriptional level irrespective of p53 status. Importantly, SESN2 also protected cells from metabolic stress triggered by glucose limitation in a p53-independent manner. Our data indicated that stabilization of SESN2 transcript might be an alternative adaptive response to metabolic stress other than p53 activation. Thereby, the current study highlights the significance of stabilization of SESN2 transcript in adaptation of cells with p53 deletion or mutation to metabolic stress.

BAG3 promotes autophagy and glutaminolysis via stabilizing glutaminase.

Bcl-2 associated athanogene 3 (BAG3) is an important molecule that maintains oncogenic features of cancer cells via diverse mechanisms. One of the important functions assigned to BAG3 is implicated in selective macroautophagy/autophagy, which attracts much attention recently. However, the mechanism underlying regulation of autophagy by BAG3 has not been well defined. Here, we describe that BAG3 enhances autophagy via promotion of glutamine consumption and glutaminolysis. Glutaminolysis initiates with deamination of glutamine by glutaminase (GLS), by which yields glutamate and ammonia in mitochondria. The current study demonstrates that BAG3 stabilizes GLS via prohibition its interaction with SIRT5, thereby hindering its desuccinylation at Lys158 and Lys164 sites. As an underlying molecular mechanism, we demonstrate that BAG3 interacts with GLS and decreases SIRT5 expression. The current study also demonstrates that occupation by succinyl at Lys158 and Lys164 sites prohibits its Lys48-linked ubiquitination, thereby preventing its subsequent proteasomal degradation. Collectively, the current study demonstrates that BAG3 enhances autophagy via stabilizing GLS and promoting glutaminolysis. For the first time, this study reports that succinylation competes with ubiquitination to regulate proteasomal GLS degradation.

BAG3 promotes stem cell-like phenotype in breast cancer by upregulation of CXCR4 via interaction with its transcript.

BAG3 is an evolutionarily conserved co-chaperone expressed at high levels and has a prosurvival role in many tumor types. The current study reported that BAG3 was induced under specific floating culture conditions that enrich breast cancer stem cell (BCSC)-like cells in spheres. Ectopic BAG3 overexpression increased CD44+/CD24- CSC subpopulations, first-generation and second-generation mammosphere formation, indicating that BAG3 promotes CSC self-renewal and maintenance in breast cancer. We further demonstrated that mechanically, BAG3 upregulated CXCR4 expression at the post-transcriptional level. Further studies showed that BAG3 interacted with CXCR4 mRNA and promoted its expression via its coding and 3'-untranslational regions. BAG3 was also found to be positively correlated with CXCR4 expression and unfavorable prognosis in patients with breast cancer. Taken together, our data demonstrate that BAG3 promotes BCSC-like phenotype through CXCR4 via interaction with its transcript. Therefore, this study establishes BAG3 as a potential adverse prognostic factor and a therapeutic target of breast cancer.

Induction of epithelial-mesenchymal transition (EMT) by Beclin 1 knockdown via posttranscriptional upregulation of ZEB1 in thyroid cancer cells.

Beclin 1 has emerged as a haploinsufficient tumor suppression gene in a variety of human carcinomas. In order to clarify the role of Beclin 1 in thyroid cancer, Beclin 1 was knockdown in thyroid cancer cell lines. The current study demonstrated that knockdown of Beclin 1 resulted in morphological and molecular changes of thyroid cancer cells consistent with epithelial-mesenchymal transition (EMT), a morphogenetic procedure during which cells lose their epithelial characteristics and acquire mesenchymal properties concomitantly with gene expression reprogramming. In addition, the current study presented evidence demonstrating that Beclin 1 knockdown triggered this prometastatic process via stabilization of the EMT inducer ZEB1 mRNA through upregulation of AU-binding factor 1 (AUF1), which is recruited to the 3'-untranslated region (UTR) of the ZEB1 mRNA and decreases its degradation. We also found a negative correlation of Beclin 1 with AUF1 or ZEB1 in thyroid cancer tissues. These results indicated that at least some tumor suppressor functions of Beclin 1 were mediated through posttranscriptional regulation of ZEB1 via AUF1 in thyroid cancers.

BAG3 elevation inhibits cell proliferation via direct interaction with G6PD in hepatocellular carcinomas.

Bcl-2 associated athanogene 3 (BAG3) contains multiple protein-binding motifs to mediate potential interactions with chaperons and/or other proteins, which is possibly ascribed to the multifaceted functions assigned to BAG3. The current study demonstrated that BAG3 directly interacted with glucose 6 phosphate dehydrogenase (G6PD), the rate-limiting enzyme of the pentose phosphate pathway (PPP). BAG3 suppressed the PPP flux, de novo DNA synthesis and cell growth in hepatocellular carcinomas (HCCs). The growth defect of HCCs with forced BAG3 expression can be rescued by enforced G6PD expression. However, BAG3 elevation did not cause a reduction in cellular NADPH concentrations, another main product of G6PD. In addition, supplement of nucleosides alone was sufficient to recover the growth defect mediated by BAG3 elevation. Collectively, the current study established a tumor suppressor-like function of BAG3 via direct interaction with G6PD in HCCs at the cellular level.

BAG3 is upregulated by c-Jun and stabilizes JunD.

BAG3 plays a regulatory role in a number of cellular processes, including cell proliferation, apoptosis, adhesion and migration, epithelial-mesenchymal transition (EMT), autophagy activation, and virus infection. The AP-1 transcription factors are implicated in a variety of important biological processes including cell differentiation, proliferation, apoptosis and oncogenesis. Recently, it has been reported that AP-1 protein c-Jun inhibits autophagy and enhances apoptotic cell death mediated by starvation. However, the molecular mechanisms remain unclear. For the first time, the current study demonstrated that serum starvation downregulated BAG3 at the transcriptional level via c-Jun. In addition, the current study reported that BAG3 stabilized JunD mRNA, which was, at least in part, responsible for the promotion of serum starvation mediated-growth inhibition by BAG3.

BAG3 sensitizes cancer cells exposed to DNA damaging agents via direct interaction with GRP78.

Bcl-2 associated athanogene 3 (BAG3) has a modular structure that contains a BAG domain, a WW domain, a proline-rich (PxxP) domain to mediate potential interactions with chaperons and other proteins that participate in more than one signal transduction. In search for novel interacting partners, the current study identified that 78kDa glucose-regulated protein (GRP78) was a novel partner interacting with BAG3. Interaction between GRP78 and BAG3 was confirmed by coimmunoprecipitation and glutathione S-transferase (GST) pulldown. We also identified that the ATPase domain of GRP78 and BAG domain of BAG3 mediated their interaction. Counterintuitive for a prosurvival protein, BAG3 was found to promote the cytotoxicity of breast cancer MCF7, thyroid cancer FRO and glioma U87 cells subjected to genotoxic stress. In addition, the current study demonstrated that BAG3 interfered with the formation of the antiapoptotic GRP78-procaspase-7 complex, which resulted in an increased genotoxic stress-induced cytotoxicity in cancer cells. Furthermore, overexpression of GRP78 significantly blocked the enhancing effects of BAG3 on activation of caspase-7 and induction of apoptosis by genotoxic stress. Overall, these results suggested that through direct interaction BAG3 could prevent the antiapoptotic effect of GRP78 upon genotoxic stress.

BAG3-dependent noncanonical autophagy induced by proteasome inhibition in HepG2 cells.

Emerging lines of evidence have shown that blockade of ubiquitin-proteasome system (UPS) activates autophagy. The molecular players that regulate the relationship between them remain to be elucidated. Bcl-2 associated athanogene 3 (BAG3) is a member of the BAG co-chaperone family that regulates the ATPase activity of heat shock protein 70 (HSP70) chaperone family. Studies on BAG3 have demonstrated that it plays multiple roles in physiological and pathological processes, including antiapoptotic activity, signal transduction, regulatory role in virus infection, cell adhesion and migration. Recent studies have attracted much attention on its role in initiation of autophagy. The current study, for the first time, demonstrates that proteasome inhibitors elicit noncanonical autophagy, which was not suppressed by inhibitors of class III phosphatidylinositol 3-kinase (PtdIns3K) or shRNA against Beclin 1 (BECN1). In addition, we demonstrate that BAG3 is ascribed to activation of autophagy elicited by proteasome inhibitors and MAPK8/9/10 (also known as JNK1/2/3 respectively) activation is also implicated via upregulation of BAG3. Moreover, we found that noncanonical autophagy mediated by BAG3 suppresses responsiveness of HepG2 cells to proteasome inhibitors.

Implication of Nrf2 and ATF4 in differential induction of CHOP by proteasome inhibition in thyroid cancer cells.

Proteasome inhibition may cause endoplasmic reticulum (ER) stress, which has been reported to be implicated in the antitumoral effects of proteasome inhibitors. CCAAT/enhancer-binding protein homologous protein (CHOP) is induced by a variety of adverse physiological conditions including ER stress and is involved in apoptosis. We have reported that distinct induction of CHOP contributes to the responsiveness of thyroid cancer cells to proteasome inhibitors. However, the mechanism underlying differential induction of CHOP by proteasome inhibitors in thyroid cancer cells has not been well characterized. In the current study, we characterized that proteasome inhibition primarily activated the amino acid response element 1 (AARE1) on the CHOP promoter. We also demonstrated that although proteasome inhibition caused similar accumulation of activating transcription factor 4 (ATF4) in a panel of thyroid cancer cells, distinct amounts of ATF4 were recruited to the AARE1 element of CHOP promoter. In addition, we demonstrated that NF-E2-related factor 2 (Nrf2) was also implicated in the induction of CHOP by precluding the binding of ATF4 to the CHOP promoter. This study highlights the molecular mechanisms by which ATF4 and Nrf2 can control CHOP induction in thyroid cancer cells by proteasome inhibition.

Involvement of JNK and NF-κB pathways in lipopolysaccharide (LPS)-induced BAG3 expression in human monocytic cells.

Lipopolysaccharide (LPS) is an outer-membrane glycolipid component of Gram-negative bacteria known for its fervent ability to activate monocytic cells and for its potent proinflammatory capabilities. Bcl-2-associated athanogene 3 (BAG3) is a survival protein that has been shown to be stimulated during cell response to stressful conditions, such as exposure to high temperature, heavy metals, proteasome inhibition, and human immunodeficiency virus 1 (HIV-1) infection. In addition, BAG3 regulates replication of Varicella-Zoster Virus (VZV) and Herpes Simplex Virus (HSV) replication, suggesting that BAG3 could participate in the host response to infection. In the current study, we found that LPS increased the expression of BAG3 in a dose- and time-dependent manner. Actinomycin D completely blocked the LPS-induced BAG3 accumulation, as well as LPS activated the proximal promoter of BAG3 gene, supported that the induction by LPS occurred at the level of gene transcription. LPS-induced BAG3 expression was blocked by JNK or NF-κB inhibition, suggesting that JNK and NF-κB pathways participated in BAG3 induction by LPS. In addition, we also found that induction of BAG3 was implicated in monocytic cell adhesion to extracellular matrix induced by LPS. Overall, the data support that BAG3 is induced by LPS via JNK and NF-κB-dependent signals, and involved in monocytic cell-extracellular matrix interaction, suggesting that BAG3 may have a role in the host response to LPS stimulation.