Tubb3 regulation by the Erk and Akt signaling pathways: a mechanism involved in the effect of arginine ADP-ribosyltransferase 1 (Art1) on apoptosis of colon carcinoma CT26 cells

ART1 knockdown decreases the IL-6-induced proliferation of colorectal cancer cells

Colorectal cancer (CRC) is a worldwide health concern. Chronic inflammation is a risk factor for CRC, and interleukin-6 (IL-6) plays a pivotal role in this process. Arginine-specific mono-ADP-ribosyltransferase-1 (ART1) positively regulates inflammatory cytokines. ART1 knockdown reduces the level of glycoprotein 130 (gp130), a key transducer in the IL-6 signalling pathway. However, the relationship between ART1 and IL-6 and the resulting effects on IL-6-induced proliferation in CRC cells remain unclear. The aims of this study were to investigate the effects of ART1 knockdown on IL-6-induced cell proliferation in vitro and use an in vivo murine model to observe the growth of transplanted tumours. The results showed that compared with the control, ART1-sh cancer cells induced by IL-6 exhibited reduced viability, a lower rate of colony formation, less DNA synthesis, decreased protein levels of gp130, c-Myc, cyclin D1, Bcl-xL, and a reduced p-STAT3/STAT3 ratio (P < 0.05). Moreover, mice transplanted with ART1-sh CT26 cells that had high levels of IL-6 displayed tumours with smaller volumes (P < 0.05). ART1 and gp130 were colocalized in CT26, LoVo and HCT116 cells, and their expression was positively correlated in human CRC tissues. Overall, ART1 may serve as a promising regulatory factor for IL-6 signalling and a potential therapeutic target for human CRC.

Novel 8-Methoxycoumarin-3-Carboxamides with potent anticancer activity against liver cancer via targeting caspase-3/7 and β-tubulin polymerization

In the present study, we explored the potential of coumarin-based compounds, known for their potent anticancer properties, by designing and synthesizing a novel category of 8-methoxycoumarin-3-carboxamides. Our aim was to investigate their antiproliferative activity against liver cancer cells. Toward this, we developed a versatile synthetic approach to produce a series of 8-methoxycoumarin-3-carboxamide analogues with meticulous structural features. Assessment of their antiproliferative activity demonstrated their significant inhibitory effects on the growth of HepG2 cells, a widely studied liver cancer cell line. Among screened compounds, compound 5 exhibited the most potent antiproliferative activity among the screened compounds (IC50 = 0.9 µM), outperforming the anticancer drug staurosporine (IC50 = 8.4 µM), while showing minimal impact on normal cells. The flow cytometric analysis revealed that compound 5 induces cell cycle arrest during the G1/S phase and triggers apoptosis in HepG2 cells by increasing the percentage of cells arrested in the G2/M and pre-G1 phases. Annexin V-FITC/PI screening further supported the induction of apoptosis without significant necrosis. Further, compound 5 exhibited the ability to activate caspase3/7 protein and substantially inhibited β-tubulin polymerization activity in HepG2 cells. Finally, molecular modelling analysis further affirmed the high binding affinity of compound 5 toward the active cavity of β-tubulin protein, suggesting its mechanistic involvement. Collectively, our findings highlight the therapeutic potential of the presented class of coumarin analogues, especially compound 5, as promising candidates for the development of effective anti-hepatocellular carcinoma agents.

Clinicopathological significance of TUBB3 in upper tract urothelial carcinoma and possible application in urine cytology

βIII-Tubulin, encoded by the TUBB3 gene, is a microtubule protein. We previously reported that TUBB3 is overexpressed in renal cell carcinoma. We investigated the clinicopathological significance of TUBB3 in upper tract urothelial carcinoma (UTUC) by immunohistochemistry. In normal tissue, TUBB3 expression was weak or absent. In contrast, TUBB3 overexpression was observed in urothelial carcinoma (UC) tissues in 51 (49%) of 103 UTUC cases. TUBB3 overexpression was associated with nodular/flat morphology, high-grade disease, high T stage, and a poor prognosis. Similar results were obtained in The Cancer Genome Atlas bladder cancer cohort. TUBB3 expression was also associated with high Ki-67 labeling index, CD44v9, HER2, EGFR, and p53 expression in UTUC. Among representative cancer-related molecules, TUBB3 was an independent predictor of progression-free survival and high-grade UC. Finally, using urine cytology samples, we analyzed TUBB3 expression by immunocytochemistry. TUBB3 expression was more frequently found in UC cells than in nonneoplastic cells. The diagnostic accuracy of urine cytology was improved when combined with TUBB3 immunostaining. The findings suggest the importance of TUBB3 in tumor progression and its potential application as a biomarker for high-grade disease and the prognosis of UC. Moreover, combination with TUBB3 immunostaining might improve the diagnostic accuracy of urine cytology.

Identification of the role of mono-ADP-ribosylation in colorectal cancer by integrated transcriptome analysis

Our previous study clarified the carcinogenic properties of arginine-specific mono-ADP-ribosyltransferase 1 (ART1), which results in a critical post-translational modification that changes the structure and function of proteins and is widely involved in important processes. This study provides, for the first time, a comprehensive transcriptomic analysis of colorectal cancer cells with ART1 silencing by Illumina RNA-Seq and related verification experiments. Lentiviral infection was used to construct a CT-26 cell line with stable knockdown of the ART1 gene, and a whole transcriptome sequencing technique was performed to identify differentially expressed genes (DEGs). GO and KEGG classification/enrichment analyses and verification experiments were performed to determine the role of ART1 in the progression of colorectal cancer. A total of 5552 DEGs, GO functions and KEGG pathways with the highest enrichment, various SNPs, and diverse splicing patterns were identified. Importantly, knockdown of ART1 affected the splicing of certain key genes related to tumor cell growth and downregulated the expression of the key gene PTBP1 for alternative splicing. The overall attenuation of the endoplasmic reticulum unfolded protein response (UPR) signaling pathway caused by the inhibition of mono-ADP-ribosylation of GRP78 could disrupt UPR signaling, leading to the occurrence of apoptosis to impede tumorigenesis. ART1, which is clustered in organelles, may promote the development of colorectal cancer by participating in a variety of new mechanisms, including endoplasmic reticulum stress regulation and alternative splicing, and may be a good clinical drug target for targeted therapy of CRC.

βIII-tubulin overexpression in cancer: Causes, consequences, and potential therapies

Class III β-tubulin (βIII-tubulin) is frequently overexpressed in human tumors and is associated with resistance to microtubule-targeting agents, tumor aggressiveness, and poor patient outcome. Understanding the mechanisms regulating βIII-tubulin expression and the varied functions βIII-tubulin may have in different cancers is vital to assess the prognostic value of this protein and to develop strategies to enhance therapeutic benefits in βIII-tubulin overexpressing tumors. Here we gather all the available evidence regarding the clinical implications of βIII-tubulin overexpression in cancer, describe factors that regulate βIII-tubulin expression, and discuss current understanding of the mechanisms underlying βIII-tubulin-mediated resistance to microtubule-targeting agents and tumor aggressiveness. Finally, we provide an overview of emerging therapeutic strategies to target tumors that overexpress βIII-tubulin.

Exosomes Derived from Human Urine-Derived Stem Cells Inhibit Intervertebral Disc Degeneration by Ameliorating Endoplasmic Reticulum Stress

Objective

This study is aimed at determining the effects of human urine-derived stem cell-derived exosomes (USCs-exos) on pressure-induced nucleus pulposus cell (NPC) apoptosis and intervertebral disc degeneration (IDD) and on the ERK and AKT signaling pathways.

Methods

The NPCs were obtained from patients with herniated lumbar discs. Western blot analysis (WB) and quantitative real-time polymerase chain reaction (qRT-PCR) were used to determine endoplasmic reticulum (ER) stress levels of NPCs under stress. Human USCs were identified using an inverted microscope, three-line differentiation experiments, and flow cytometry. A transmission microscope, nanoparticle size analysis, and WB procedures were used to identify the extracted exosomes and observe NPC uptake. A control group, a 48 h group, and a USCs-exos group were established. The control group was untreated, and the 48 h group was pressure-trained for 48 h, while the USCs-exos group was pressure-trained for 48 h and treated with USCs-exos. WB, qRT-PCR, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis were used to determine the ER stress levels in stress conditions and after exosomal treatment. The AKT and ERK pathways were partially detected. Magnetic Resonance Imaging (MRI) and computed tomography (CT) were used to evaluate cell degeneration while exosomal effects on the intervertebral disc (IVD) tissue were determined by hematoxylin and eosin (HE) staining, Safranin O-fast green staining, immunohistochemical staining (IHC), nuclear magnetic resonance (NMR), spectrometric detection, and total correlation spectroscopy (TOCSY). IVD metabolites were also identified and quantified.

Results

After pressure culture, ER stress markers (GRP78 and C/EBP homologous protein (CHOP)) in the NPCs were significantly elevated with time (p < 0.05). Human USCs are short and spindle-shaped. They can successfully undergo osteogenic, adipogenic, and chondrogenic differentiation. In this study, these stem cells were found to be positive for CD29, CD44, and CD73. The exosomes were centrally located with a diameter of 50-100 nm. CD63 and Tsg101 were highly expressed while the expression of Calnexin was suppressed. The exosomes can be ingested by NPCs. USCs-exos significantly improved ER stress responses and inhibited excessive activation of the unfolded protein response (UPR) as well as cell apoptosis and disc degeneration through the AKT and ERK signaling pathways (p < 0.05).

Conclusion

Through the AKT and ERK signaling pathways, USCs-exos significantly inhibit ER stress-induced cell apoptosis and IDD under pressure conditions. It is, therefore, a viable therapeutic strategy.

TUBB3 Is Associated with High-Grade Histology, Poor Prognosis, p53 Expression, and Cancer Stem Cell Markers in Clear Cell Renal Cell Carcinoma

BACKGROUND

βIII-Tubulin, encoded by the TUBB3 gene, is a microtubule protein. Several studies have shown that overexpression of TUBB3 is linked to poor prognosis and is involved in taxane resistance in some cancers.

OBJECTIVE

The aim of this study was to analyze the expression and function of TUBB3 in clear cell renal cell carcinoma (ccRCC).

METHODS

The expression of TUBB3 was determined using immuno-histochemistry in ccRCC specimens. The effects of TUBB3 knockdown on cell growth and invasion were evaluated in RCC cell lines. We analyzed the interaction between TUBB3, p53, cancer stem cell markers, and PD-L1.

RESULTS

In 137 cases of ccRCC, immunohistochemistry showed that 28 (20%) of the ccRCC cases were positive for TUBB3. High TUBB3 expression was significantly correlated with high nuclear grade, high T stage, and N stage. A Kaplan-Meier analysis showed that high expression of TUBB3 was associated with poor overall survival after nephrectomy. In silico analysis also showed that high TUBB3 expression was correlated with overall survival. Knockdown of TUBB3 suppressed cell growth and invasion in 786-O and Caki-1 cells. High TUBB3 expression was associated with CD44, CD133, PD-L1, and p53 in ccRCC. We generated p53 knockout cells using the CRISPR-Cas9 system. Western blotting revealed that p53 knockout upregulated the expression of TUBB3.

CONCLUSION

These results suggest that TUBB3 may play an oncogenic role and could be a potential therapeutic target in ccRCC.

TUBB3 Reverses Resistance to Docetaxel and Cabazitaxel in Prostate Cancer

Recent studies have reported that TUBB3 overexpression is involved in docetaxel (DTX) resistance in prostate cancer (PCa). The aim of this study was to clarify the role of TUBB3 in DTX and cabazitaxel (CBZ) resistance, and cross-resistance between DTX and CBZ in PCa. We analyzed the effect of TUBB3 knockdown on DTX and CBZ resistance and examined the interaction between TUBB3 and PTEN. We also investigated the role of phosphoinositide 3-kinases (PI3K) inhibitor (LY294002) in DTX and CBZ resistance. TUBB3 expression was upregulated in DTX-resistant and CBZ-resistant cells. TUBB3 knockdown re-sensitized DTX-resistant cells to DTX and CBZ-resistant cells to CBZ. Additionally, TUBB3 knockdown re-sensitized DTX-resistant cell lines to CBZ, indicating that TUBB3 mediates cross-resistance between DTX and CBZ. Knockdown of TUBB3 enhanced PTEN expression, and PTEN knockout enhanced TUBB3 expression. LY294002 suppressed TUBB3 expression in DTX-resistant and CBZ-resistant cell lines. LY294002 re-sensitized DTX-resistant cell lines to DTX and CBZ-resistant cell lines to CBZ. These results suggest that TUBB3 is involved in DTX resistance and CBZ resistance. A combination of LY294002/DTX and that of LY294002/CBZ could be potential strategies for PCa treatment.

Overview of the mammalian ADP-ribosyl-transferases clostridia toxin-like (ARTCs) family

Mono-ADP-ribosylation is a reversible post-translational protein modification that modulates the function of proteins involved in different cellular processes, including signal transduction, protein transport, transcription, cell cycle regulation, DNA repair and apoptosis. In mammals, mono-ADP-ribosylation is mainly catalyzed by members of two different classes of enzymes: ARTCs and ARTDs. The human ARTC family is composed of four structurally related ecto-mono-ARTs, expressed at the cell surface or secreted into the extracellular compartment that are either active mono-ARTs (hARTC1, hARTC5) or inactive proteins (hARTC3, hARTC4). The human ARTD enzyme family consists of 17 multidomain proteins that can be divided on the basis of their catalytic activity into polymerases (ARTD1-6), mono-ART (ARTD7-17), and the inactive ARTD13. In recent years, ADP-ribosylation was intensively studied, and research was dominated by studies focusing on the role of this modification and its implication on various cellular processes. The aim of this review is to provide a general overview of the ARTC enzymes. In the following sections, we will report the mono-ADP-ribosylation reactions that are catalysed by the active ARTC enzymes, with a particular focus on hARTC1 that recently has been intensively studied with the discovery of new targets and functions.

Exosomes from mesenchymal stem cells modulate endoplasmic reticulum stress to protect against nucleus pulposus cell death and ameliorate intervertebral disc degeneration in vivo

Objectives: Intervertebral disc degeneration (IDD) is widely accepted as a cause of low back pain and related degenerative musculoskeletal disorders. Nucleus pulposus (NP) cell apoptosis which is related to excessive endoplasmic reticulum (ER) stress in the intervertebral disc (IVD) could aggravate IDD progression. Many studies have shown the therapeutic potential of exosomes derived from bone marrow mesenchymal stem cells (MSC-exos) in degenerative diseases. We hypothesized that the delivery of MSC-exos could modulate ER stress and inhibit excessive NP cell apoptosis during IDD.

Methods: The ER stress levels were measured in normal or degenerative NP tissues for contrast. The effects of MSC-exos were testified in advanced glycation end products (AGEs) -induced ER stress in human NP cells. The mechanism involving AKT and ERK signaling pathways was investigated using RNA interference or signaling inhibitors. Histological or immunohistochemical analysis and TUNEL staining were used for evaluating MSC-exos therapeutic effects in vivo.

Results: The ER stress level and apoptotic rate was elevated in degenerative IVD tissues. MSC-exos could attenuate ER stress-induced apoptosis by activating AKT and ERK signaling. Moreover, delivery of MSC-exos in vivo modulated ER stress-related apoptosis and retarded IDD progression in a rat tail model.

Conclusions: These results highlight the therapeutic effects of exosomes in preventing IDD progression. Our work is the first to demonstrate that MSC-exos could modulate ER stress-induced apoptosis during AGEs-associated IVD degeneration.

The Potential of Combining Tubulin-Targeting Anticancer Therapeutics and Immune Therapy

Cancer immune therapy has recently shown tremendous promise to combat many different cancers. The microtubule is a well-defined and very effective cancer therapeutic target. Interestingly, several lines of evidence now suggest that microtubules are intimately connected to the body’s immune responses. This raises the possibility that the combination of microtubule inhibitors and immune therapy can be a highly effective option for cancer treatments. However, our understanding on this potentially important aspect is still very limited, due in part to the multifaceted nature of microtubule functions. Microtubules are not only involved in maintaining cell morphology, but also a variety of cellular processes, including the movement of secretory vesicles and organelles, intracellular macromolecular assembly, signaling pathways, and cell division. Microtubule inhibitors may be subdivided into two classes: Anti-depolymerization agents such as the taxane family, and anti-polymerization agents such as colchicine and vinka alkaloids. These two different classes may have different effects on immune cell subtypes. Anti-depolymerization agents can not only induce NK cells, but also appear to inhibit T regulatory (Treg) cells. However, different inhibitors may have different functions even among the same class. For example, the doxetaxel anti-depolymerization agent up-regulates cytotoxic T cells, while paclitaxel down-regulates them. Certain anti-polymerization agents such as colchicine appear to down-regulate most immune cell types, while inducing dendritic cell maturation and increasing M1 macrophage population. In contrast, the vinblastine anti-polymerization agent activates many of these cell types, albeit down-regulating Treg cells. In this review, we focus on the various effects of tubulin inhibitors on the activities of the body’s immune system, in the hope of paving the way to develop an effective cancer therapy by combining tubulin-targeting anticancer agents and immune therapy.

Targeted silencing of the ADP-ribosyltransferase 3 gene inhibits the migration ability of melanoma cells

Melanoma is the most common primary intraocular malignancy and metastasis of melanoma to other organs often results in a poor prognosis. ADP-ribosyltransferase 3 (ART3) is involved in cell division and DNA repair. However, its biological function in melanoma remains unclear. In the present study, it was identified that ART3 is highly expressed in melanoma cells and melanoma tissues compared with the normal RPE cell line, and adjacent normal tissue, respectively. Small interfering RNA and short hairpin RNA were used to silence ART3 gene expression, and the results revealed that the silencing of ART3 inhibits the migratory ability of melanoma cells. The present study indicates that ART3 serves a notable role in the metastasis of melanoma and provides a potential therapeutic target for this disease.

An Emerging Role for Tubulin Isotypes in Modulating Cancer Biology and Chemotherapy Resistance

Tubulin proteins, as components of the microtubule cytoskeleton perform critical cellular functions throughout all phases of the cell cycle. Altered tubulin isotype composition of microtubules is emerging as a feature of aggressive and treatment refractory cancers. Emerging evidence highlighting a role for tubulin isotypes in differentially influencing microtubule behaviour and broader functional networks within cells is illuminating a complex role for tubulin isotypes regulating cancer biology and chemotherapy resistance. This review focuses on the role of different tubulin isotypes in microtubule dynamics as well as in oncogenic changes that provide a survival or proliferative advantage to cancer cells within the tumour microenvironment and during metastatic processes. Consideration of the role of tubulin isotypes beyond their structural function will be essential to improving the current clinical use of tubulin-targeted chemotherapy agents and informing the development of more effective cancer therapies.