Silencing PCMT1 enhances the sensitivity of breast cancer cells to paclitaxel through the PI3K/Akt/STMN1 pathway.

This study aimed to investigate whether silencing Protein L-isoaspartate (D-aspartate) O-methyltransferase (PCMT1) expression can enhance the sensitivity of breast cancer cells to paclitaxel and its possible mechanism. Tumor tissues and adjacent histologically normal tissues were collected from patients with breast cancer admitted to our hospital. Human normal breast epithelial cells MCF10A, human breast cancer cells MCF-7, and paclitaxel-resistant breast cancer cells MCF-7/PR were purchased. MCF-7/PR cells were further grouped into negative control (NC) group, si-PCMT1 group (transfected with si-PCMT1), 740Y-P group (treated with 740Y-P, an activator of phosphatidylinositol 3-kinase (PI3K)/ v-Akt Murine Thymoma Viral Oncogene (AKT) signaling pathway), and si-PCMT1 + 740Y-P group (transfected with si-PCMT1 and then treated with 740Y-P). The expression level of PCMT1 in tissues and cells was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Western blot analysis was used to detect the protein expression level of PCMT1 in tissues and cells as well as the protein level of p-PI3K, PI3K, p-Akt, Akt, and Stathmin1 (STMN1) in cells. 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide (MTT) and colony formation assays were used to determine cell viability, scratch assay was used to assess the migration ability of cells, and Transwell assay was used to assess the invasion ability of cells. The expression of PCMT1 was remarkably up-regulated in breast cancer tissues and MCF-7/PR cells. Silencing PCMT1 expression significantly inhibited the proliferation, migration, and invasion of MCF-7/PR cells, and alleviated the resistance of cancer cells to paclitaxel. Additionally, silencing PCMT1 expression also inhibited the activation of PI3K/Akt/STMN1 pathway in MCF-7/PR cells, while activating PI3K/Akt/STMN1 pathway significantly reversed the effect of silencing PCMT1 expression on MCF-7/PR cells. PCMT1 is highly expressed in breast cancer tissues and MCF-7/PR cells, and silencing PCMT1 expression can not only inhibit the development of breast cancer but also enhance paclitaxel sensitivity. Its mechanism of action may be achieved by inhibiting PI3K/Akt/STMN1 signaling.

Paris saponin VII inhibits triple-negative breast cancer by targeting the MEK/ERK/STMN1 signaling axis.

BACKGROUND: Triple-negative breast cancer (TNBC) is a category of breast cancer characterized with high molecular heterogeneity. Owing to the lack of effective therapeutic strategies, patients with TNBC have a poor prognosis. Paris saponin VII (PSⅦ), a steroidal saponin extracted from the rhizome of Trichillium tschonoskii Maxim, exhibits excellent anti-cancer activity in a variety of solid tumors. However, the role and potential mechanism of PSⅦ against TNBC remain unexplored. PURPOSE: This study aimed to elucidate the therapeutic effects of PSⅦ against TNBC and explore the potential mechanism of action. METHODS: We combined the analysis of public single-cell sequencing data with weighted gene co-expression network analysis (WGCNA) to identity differentially expressed genes (DEGs) that distinguished malignant and normal epithelial cells in TNBC. Subsequently, the biological features of DEGs in TNBC were evaluated. Gene set enrichment analysis (GSEA) was used to define potential pathways associated with the DEGs. The pharmacological activity of PSⅦ for TNBC was evidenced via in vitro and in vivo experiments, and molecular docking, molecular dynamics (MD), surface plasmon resonance (SPR) assay and western blotting were employed to confirm the relative mechanisms. RESULTS: Single-cell sequencing and WGCNA revealed STMN1 as a pivotal biomarker of TNBC. STMN1 overexpression in TNBC was associated with poor patient prognosis. GSEA revealed a significant accumulation of STMN1 within the MAPK signaling pathway. Furthermore, In vitro experiments showed that PSⅦ showed significantly suppressive actions on the proliferation, migration and invasion abilities for TNBC cells, while inducing apoptosis. Molecular docking, MD analysis and SPR assay indicated a robust interaction between PSⅦ and the MEK protein. Western blotting revealed that PSⅦ may inhibit tumor progression by suppressing the phosphorylation of MEK1/2 and the downstream phosphorylation of ERK1/2 and STMN1. Intraperitoneal injection of PSⅦ (10 mg/kg) notably reduced tumor growth by 71.26 % in a 4T1 xenograft model. CONCLUSION: In our study, the systems biology method was used to identify potential therapeutic targets for TNBC. In vitro and in vivo experiments demonstrated PSⅦ suppresses cancer progression by targeting the MEK/ERK/STMN1 signaling axis. For the first time, the inhibition of STMN1 phosphorylation has been indicated as a possible mechanism for the anticancer effects of PSⅦ. These results emphasize the potential value of PSⅦ as a promising anti-cancer drug candidate for further development in the field of TNBC therapeutics.

The relationship between stathmin-2 level and metabolic parameters in newly diagnosed type 2 diabetes mellitus patients.

BACKGROUND: Stathmin is a phosphoprotein that plays a role in intercellular and intracellular signaling, inflammation, and differentiation. Our aim was to evaluate the stathmin-2 level and its relationship with the metabolic parameters of newly diagnosed type 2 diabetes mellitus (nT2DM) patients. MATERIAL AND METHOD: This case-control study included 76 patients with nT2DM and 76 healthy individuals with a normal oral glucose tolerance test who were matched for body mass index (BMI), age, and gender. In addition to laboratory and anthropometric measurements related to type 2 diabetes mellitus (T2DM), stathmin-2 levels were determined using an enzyme-linked immunosorbent assay. RESULTS: We observed significantly higher circulating stathmin-2 levels in subjects with T2DM compared to the control group (6.39±1.60 ng/mL and 4.66±0.80 ng/mL, p<0.0001). In patients with metabolic syndrome, circulating stathmin-2 levels were significantly elevated compared to those without metabolic syndrome in both the T2DM and control groups (T2DM: 7.16±1.24 vs 5.06±1.24 ng/mL, p<0.001; Control: 3.84±1.40 vs 3.82±1.40 ng/mL). In both groups, we observed a positive correlation between stathmin-2 levels and BMI and circumference. Moreover, stathmin-2 showed a positive correlation with high-sensitivity C-reactive protein (hs-CRP), homeostatic model assessment of insulin resistance, insulin, fasting blood glucose, hemoglobin A1c, BMI, low-density lipoprotein cholesterol, and total cholesterol. A negative correlation was observed with stathmin-2 and high-density lipoprotein cholesterol. Stathmin-2 did not show any correlation with age, triglyceride, and lactate dehydrogenase. CONCLUSIONS: Stathmin-2 levels were found to be elevated in patients with nT2DM and exhibited positive correlations with hyperinsulinaemia, hyperglycaemia, HOMO-IR and hs-CRP levels. These results indicate that stathmin-2 may play a role in T2DM pathogenesis.

Identification of an immune-related gene signature for predicting prognosis and immunotherapy efficacy in liver cancer via cell-cell communication.

BACKGROUND: Liver cancer is one of the deadliest malignant tumors worldwide. Immunotherapy has provided hope to patients with advanced liver cancer, but only a small fraction of patients benefit from this treatment due to individual differences. Identifying immune-related gene signatures in liver cancer patients not only aids physicians in cancer diagnosis but also offers personalized treatment strategies, thereby improving patient survival rates. Although several methods have been developed to predict the prognosis and immunotherapeutic efficacy in patients with liver cancer, the impact of cell-cell interactions in the tumor microenvironment has not been adequately considered. AIM: To identify immune-related gene signals for predicting liver cancer prognosis and immunotherapy efficacy. METHODS: Cell grouping and cell-cell communication analysis were performed on single-cell RNA-sequencing data to identify highly active cell groups in immune-related pathways. Highly active immune cells were identified by intersecting the highly active cell groups with B cells and T cells. The significantly differentially expressed genes between highly active immune cells and other cells were subsequently selected as features, and a least absolute shrinkage and selection operator (LASSO) regression model was constructed to screen for diagnostic-related features. Fourteen genes that were selected more than 5 times in 10 LASSO regression experiments were included in a multivariable Cox regression model. Finally, 3 genes (stathmin 1, cofilin 1, and C-C chemokine ligand 5) significantly associated with survival were identified and used to construct an immune-related gene signature. RESULTS: The immune-related gene signature composed of stathmin 1, cofilin 1, and C-C chemokine ligand 5 was identified through cell-cell communication. The effectiveness of the identified gene signature was validated based on experimental results of predictive immunotherapy response, tumor mutation burden analysis, immune cell infiltration analysis, survival analysis, and expression analysis. CONCLUSION: The findings suggest that the identified gene signature may contribute to a deeper understanding of the activity patterns of immune cells in the liver tumor microenvironment, providing insights for personalized treatment strategies.

STMND1 is a phylogenetically ancient stathmin which localizes to motile cilia and exhibits nuclear translocation that is inhibited when soluble tubulin concentration increases.

Stathmins are small, unstructured proteins that bind tubulin dimers and are implicated in several human diseases, but whose function remains unknown. We characterized a new stathmin, STMND1 (Stathmin Domain Containing 1) as the human representative of an ancient subfamily. STMND1 features a N-terminal myristoylated and palmitoylated motif which directs it to membranes and a tubulin-binding stathmin-like domain (SLD) that contains an internal nuclear localization signal. Biochemistry and proximity labeling showed that STMND1 binds tubulin, and live imaging showed that tubulin binding inhibits translocation from cellular membranes to the nucleus. STMND1 is highly expressed in multiciliated epithelial cells, where it localizes to motile cilia. Overexpression in a model system increased the length of primary cilia. Our study suggests that the most ancient stathmins have cilium-related functions that involve sensing soluble tubulin.

Baicalein targets STMN1 to inhibit the progression of nasopharyngeal carcinoma via regulating the Wnt/ß-catenin pathway.

BACKGROUNDS: Nasopharyngeal carcinoma is a common malignancy in the head and neck. Baicalein has been reported to exert the anticancer effects on various cancers. In this study, our aim was to explore the function of baicalein in the development of nasopharyngeal carcinoma and further investigate the potential underlying mechanisms. METHODS: Cell Counting Kit (CCK)-8 assay, EdU assay, sphere formation assay, flow cytometry, and transwell invasion assay were conducted to determine cell proliferation, stemness, apoptosis, and invasion, respectively. Western blot was performed to examine the protein levels of PCNA, MMP9, STMN1, ß-catenin, and Wnt3A. The mRNA level of STMN1 was assessed using real-time quantitative polymerase chain reaction (RT-qPCR). Xenograft tumor model was carried out to evaluate the effects of baicalein on tumor growth in vivo. Immunohistochemistry (IHC) assay was used to detect the levels of PCNA, MMP9, and STMN1 in tumor tissues from mice. RESULTS: Baicalein significantly induced cell apoptosis and impeded cell proliferation, invasion, and stemness of nasopharyngeal carcinoma cells. STMN1 was highly expressed in nasopharyngeal carcinoma, and baicalein could directly downregulate STMN1 expression. STMN1 knockdown hampered the progression of nasopharyngeal carcinoma cells. Moreover, the effects of baicalein on cell proliferation, stemness, invasion, and apoptosis in nasopharyngeal carcinoma cells were harbored by STMN1 overexpression. Baicalein regulated STMN1 to inhibit the activation of the Wnt/ß-catenin pathway. SKL2001, an agonist of the Wnt/ß-catenin pathway, could reverse the effects of STMN1 knockdown on the progression of nasopharyngeal carcinoma. In addition, baicalein markedly impeded tumor growth in vivo. CONCLUSION: Baicalein regulated the STMN1/Wnt/ß-catenin pathway to restrain the development of nasopharyngeal carcinoma.

The Interaction between ADK and SCG10 Regulate the Repair of Nerve Damage.

The cytoskeleton must be remodeled during neurite outgrowth, and Superior Cervical Ganglion 10 (SCG10) plays a critical role in this process by depolymerizing Microtubules (MTs), conferring highly dynamic properties to the MTs. However, the precise mechanism of action of SCG10 in the repair of injured neurons remains largely uncertain. Using transcriptomic identification, we discovered that SCG10 expression was downregulated in neurons after Spinal Cord Injury (SCI). Additionally, through mass spectrometry identification, immunoprecipitation, and pull-down assays, we established that SCG10 could interact with Adenosine Kinase (ADK). Furthermore, we developed an excitotoxicity-induced neural injury model and discovered that ADK suppressed injured neurite re-growth, whereas, through overexpression and small molecule interference experiments, SCG10 enhanced it. Moreover, we discovered ADK to be the upstream of SCG10. More importantly, the application of the ADK inhibitor called 5-Iodotubercidin (5-ITu) was found to significantly enhance the recovery of motor function in mice with SCI. Consequently, our findings suggest that ADK plays a negative regulatory role in the repair of injured neurons. Herein, we propose a molecular interaction model of the SCG10-ADK axis to regulate neuronal recovery.

STMN1 Promotes Tumor Metastasis in Non-small Cell Lung Cancer Through Microtubule-dependent And Nonmicrotubule-dependent Pathways.

The relationship between STMN1 and cancer metastasis is controversial. The purpose of this study was to explore the role and mechanism of STMN1 in NSCLC metastasis. In this study, we reported that STMN1 was highly expressed in NSCLC tissues and associated with poor prognosis. Both in vivo and in vitro functional assays confirmed that STMN1 promoted NSCLC metastasis. Further studies confirmed that STMN1 promoted cell migration by regulating microtubule stability. The results of Co-IP and LC‒MS/MS illustrated that STMN1 interacts with HMGA1. HMGA1 decreases microtubule stability by regulating the phosphorylation level of STMN1 at Ser16 and Ser38 after interacting with STMN1. This result suggested that STMN1 could be activated by HMGA1 to further promote NSCLC metastasis. Meanwhile, it has been found that STMN1 could promote cell migration by activating the p38MAPK/STAT1 signaling pathway, which is not dependent on microtubule stability. However, activating p38MAPK can decrease microtubule stability by promoting the dephosphorylation of STMN1 at ser16. A positive feedback loop was formed between STMN1 and p38MAPK to synergistically promote cell migration. In summary, our study demonstrated that STMN1 could promote NSCLC metastasis through microtubule-dependent and nonmicrotubule-dependent mechanisms. STMN1 has the potential to be a therapeutic target to inhibit metastasis.

WP1066, a small molecule inhibitor of STAT3, chemosensitizes paclitaxel-resistant ovarian cancer cells to paclitaxel by simultaneously inhibiting the activity of STAT3 and the interaction of STAT3 with Stathmin.

Paclitaxel is widely used to treat cancer, however, drug resistance limits its clinical utility. STAT3 is constitutively activated in some cancers, and contributes to chemotherapy resistance. Currently, several STAT3 inhibitors including WP1066 are used in cancer clinical trials. However, whether WP1066 reverses paclitaxel resistance and the mechanismremains unknown. Here, we report that in contrast to paclitaxel-sensitive parental cells, the expressions of several pro-survival BCL2 family members such as BCL-2, BCL-XL and MCL-1 are higher in paclitaxel-resistant ovarian cancer cells. Meanwhile, STAT3 is constitutively activated while stathmin loses its activity in paclitaxel-resistant cells. Importantly, WP1066 amplifies the inhibition of cell proliferation, colony-forming ability and apoptosis of ovarian cancer cells induced by paclitaxel. Mechanistically, WP1066, on the one hand, interferes the STAT3/Stathmin interaction, causing unleash of STAT3/Stathmin from microtubule, thus destroying microtubule stability. This process results in reduction of Ac-α-tubulin, further causing MCL-1 reduction. On the other hand, WP1066 inhibits phosphorylation of STAT3 by JAK2, and blocks its nuclear translocation, therefore repressing the transcription of pro-survival targets such as BCL-2, BCL-XL and MCL-1. Finally, the two pathways jointly promote cell death. Our findings reveal a new mechanism wherein WP1066 reverses paclitaxel-resistance of ovarian cancer cells by dually inhibiting STAT3 activity and STAT3/Stathmin interaction, which may layfoundation for WP1066 combined with paclitaxel in treating paclitaxel-resistant ovarian cancer.

Cryptic splicing of stathmin-2 and UNC13A mRNAs is a pathological hallmark of TDP-43-associated Alzheimer's disease.

Nuclear clearance and cytoplasmic accumulations of the RNA-binding protein TDP-43 are pathological hallmarks in almost all patients with amyotrophic lateral sclerosis (ALS) and up to 50% of patients with frontotemporal dementia (FTD) and Alzheimer's disease. In Alzheimer's disease, TDP-43 pathology is predominantly observed in the limbic system and correlates with cognitive decline and reduced hippocampal volume. Disruption of nuclear TDP-43 function leads to abnormal RNA splicing and incorporation of erroneous cryptic exons in numerous transcripts including Stathmin-2 (STMN2, also known as SCG10) and UNC13A, recently reported in tissues from patients with ALS and FTD. Here, we identify both STMN2 and UNC13A cryptic exons in Alzheimer's disease patients, that correlate with TDP-43 pathology burden, but not with amyloid-ß or tau deposits. We also demonstrate that processing of the STMN2 pre-mRNA is more sensitive to TDP-43 loss of function than UNC13A. In addition, full-length RNAs encoding STMN2 and UNC13A are suppressed in large RNA-seq datasets generated from Alzheimer's disease post-mortem brain tissue. Collectively, these results open exciting new avenues to use STMN2 and UNC13A as potential therapeutic targets in a broad range of neurodegenerative conditions with TDP-43 proteinopathy including Alzheimer's disease.

The knockdown of stathmin with si-RNA inhibits invasion of mesothelioma.

BACKGROUND: To investigate the mechanism of action of stathmin1 (STMN1) in mesothelioma (MSM) and whether it has any role in its treatment. METHODS: STMN1 expression was examined using immunohistochemistry in biopsy tissues taken from MSM patients. The relationships between the levels of STMN1 expression in the pathology preparations of MSM patients, and the clinicopathological characteristics of these patients, and their survival times were investigated. Transfection of STMN1-specific siRNA into SPC212 cells was compared to negative control siRNAs. The mRNA levels of genes that may play a role in invasion, apoptosis, and autophagy were evaluated by RT-PCR. RESULTS: The expression of STMN1 was shown to be high in MSM tissues (p < 0.05). It was found that the only independent predictor factor affecting the survival time of MSM patients was the disease stage (p < 0.05). STMN1 was significantly reduced after siRNA intervention (81.5%). STMN1 with specific siRNA has been shown to suppress invasion by reducing the mRNA levels of cadherin-6 (CDH6), fibroblast growth factor-8 (FGF8), hypoxia-inducible factor 1 (HIF1A), matrix metallopeptidase 1-2 (gelatinase A) (MMP1-2), and TIMP metallopeptidase inhibitor 2 (TIMP2), which are important markers for invasion. Although the expression of apoptosis and autophagy-related genes, caspase-2 (Casp2) and LC-3, was reduced by silencing STMN1 with specific siRNA in western blot analysis, this effect was not observed in PCR results. CONCLUSIONS: Immunohistochemical analysis of STMN1 may contribute to the differential diagnosis of MSM, and STMN1 may also be considered as a potential therapeutic target in the early invasive stage of MSM therapy.

Deficiency of copper responsive gene stmn4 induces retinal developmental defects.

As part of the central nervous system (CNS), the retina senses light and also conducts and processes visual impulses. The damaged development of the retina not only causes visual damage, but also leads to epilepsy, dementia and other brain diseases. Recently, we have reported that copper (Cu) overload induces retinal developmental defects and down-regulates microtubule (MT) genes during zebrafish embryogenesis, but whether the down-regulation of microtubule genes mediates Cu stress induced retinal developmental defects is still unknown. In this study, we found that microtubule gene stmn4 exhibited obviously reduced expression in the retina of Cu overload embryos. Furthermore, stmn4 deficiency (stmn4-/-) resulted in retinal defects similar to those seen in Cu overload embryos, while overexpression of stmn4 effectively rescued retinal defects and cell apoptosis occurred in the Cu overload embryos and larvae. Meanwhile, stmn4 deficient embryos and larvae exhibited reduced mature retinal cells, the down-regulated expression of microtubules and cell cycle-related genes, and the mitotic cell cycle arrests of the retinal cells, which subsequently tended to apoptosis independent on p53. The results of this study demonstrate that Cu stress might lead to retinal developmental defects via down-regulating expression of microtubule gene stmn4, and stmn4 deficiency leads to impaired cell cycle and the accumulation of retinal progenitor cells (RPCs) and their subsequent apoptosis. The study provides a certain referee for copper overload in regulating the retinal development in fish.

AKT/FOXM1/STMN1 signaling pathway activation by SMC1A promotes tumor growth in breast cancer.

BACKGROUND: Upregulation of SMC1A (Structural maintenance of chromosomes 1A) is linked with many types of cancer and its oncogenic function, which has been associated with crucial cellular mechanisms (cell division, cell cycle checkpoints regulation and DNA repair). Recent studies have shown that SMC1A was involved in breast cancer, although the exact mechanisms of SMC1A remain to be determined. METHODS: Using The Cancer Genome Atlas (TCGA) database, we examined SMC1A expression and its relation to other genes, including FOXM1 and STMN1. Short hairpin RNA was used to subsequently examine the biological roles of SMC1A in MDA-MB-231 and MDA-MB-468 cell lines. Bioinformatics were performed to identify the SMC1A-related gene FOXM1. RESULTS: Here, we used the TCGA database to show that SMC1A is overexpressed in breast cancer. Later investigations showed SMC1A's role in breast cancer cell survival, apoptosis and invasion. Using bioinformatics and western blot assays, we confirmed that FOXM1 acted as the downstream of SMC1A, and SMC1A knockdown significantly downregulated the FOXM1 expression via the AKT signal pathway. Interestingly, the inhibition effects induced by SMC1A downregulation could be reversed by FOXM1 overexpression. In the clinic, SMC1A expression is favorably linked with FOXM1 expression in breast cancer tumor tissues. CONCLUSIONS: Collectively, our results not only enhance our knowledge of SMC1A's molecular pathways in breast cancer, but also suggest a potential new therapeutic target.

Stathmin-2 loss leads to neurofilament-dependent axonal collapse driving motor and sensory denervation.

The mRNA transcript of the human STMN2 gene, encoding for stathmin-2 protein (also called SCG10), is profoundly impacted by TAR DNA-binding protein 43 (TDP-43) loss of function. The latter is a hallmark of several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Using a combination of approaches, including transient antisense oligonucleotide-mediated suppression, sustained shRNA-induced depletion in aging mice, and germline deletion, we show that stathmin-2 has an important role in the establishment and maintenance of neurofilament-dependent axoplasmic organization that is critical for preserving the caliber and conduction velocity of myelinated large-diameter axons. Persistent stathmin-2 loss in adult mice results in pathologies found in ALS, including reduced interneurofilament spacing, axonal caliber collapse that drives tearing within outer myelin layers, diminished conduction velocity, progressive motor and sensory deficits, and muscle denervation. These findings reinforce restoration of stathmin-2 as an attractive therapeutic approach for ALS and other TDP-43-dependent neurodegenerative diseases.

STMN1 promotes cell malignancy and bortezomib resistance of multiple myeloma cell lines via PI3K/AKT signaling.

BACKGROUND: This study investigates the biological functions of Stathmin1 (STMN1) involving drug resistance and cell proliferation in multiple myeloma (MM) and its related mechanisms. METHODS: Bone marrow aspirates were collected from 20 MM patients, and the bone marrow mononuclear cells (BMMCs) were separated by Ficoll-Hypaque density gradient centrifugation. Blood samples of 20 patients with monoclonal gammopathy of undetermined significance (MGUS) and 20 healthy donors were collected. Normal plasma cells sorted from the peripheral blood of MGUS patients and healthy subject as controls. Two bortezomib (BTZ)-resistant MM cell lines were established, namely NCI-H929/BTZ and KM3/BTZ cells, and then transfected with lentiviruses packaging sh-STMN1 to knock down STMN1 level in BTZ-resistant cells. Expression of STMN1 was assessed by RT-qPCR and western blotting. CCK-8 assays were performed to assess 50% growth inhibition (IC50) values. Green fluorescent protein in BTZ-resistant cells infected with lentiviruses was observed by fluorescence microscopy. Cell viability, proliferation, cell cycle, and apoptosis were evaluated through MTT assays, colony formation assays, flow cytometry analyses, and TUNEL staining. RESULTS: STMN1 was upregulated in MM cells and bone marrow aspirates of MM patients. Additionally, STMN1 depletion attenuated BTZ resistance in MM cells. Moreover, downregulation of STMN1 limited the malignant phenotypes of BTZ-resistant cells. Mechanistically, the PI3K/Akt signaling was inactivated by STMN1 downregulation in BTZ-resistant cells. CONCLUSION: STMN1 silencing inhibits cell proliferation and BTZ resistance in MM by inactivating the PI3K/Akt signaling.

Association Between High Expression of Phosphorylated-STMN1 and Mesenchymal Marker Expression and Cancer Stemness in Breast Cancer.

BACKGROUND/AIM: In patients with breast cancer, the expression of stathmin1 (STMN1) has been significantly related to a poor prognosis, cancer aggressiveness, and expression of cancer stem cell markers. The STMN1 protein is closely regulated by phosphorylation in four sites. However, few studies have investigated the relationship between the expression of phosphorylated STMN1 (pSTMN1) and clinicopathological findings, including tumor-aggressive biomarkers, in patients with breast cancer. MATERIALS AND METHODS: The expression levels of four pSTMN1 (Ser16, Ser25, Ser38, and Ser63) were immunohistochemically analyzed in 213 breast cancer cases. The clinicopathological factors evaluated included epithelial-mesenchymal transition (EMT) markers and cancer stem cell markers. RESULTS: The cytoplasmic expression of pSTMN1 (Ser16, Ser25, Ser38, and Ser63) in normal breast tissues was low. The positive expression ratios of Ser25 (54.5%) and Ser38 (39.0%) were high compared to those of Ser16 (25.8%) and Ser63 (23.9%). The overexpression of pSTMN1 (Ser38) was associated with tumor-aggressive characteristics, such as triple-negative breast cancer (TNBC) phenotypes, high mesenchymal marker, and expression of cancer stem cell markers. CONCLUSION: STMN1 phosphorylation might be associated with clinicopathological factors, breast cancer subtypes, and expression of mesenchymal markers and breast cancer stem cell markers through the regulation of STMN1 function. Ser38 phosphorylation of STMN1 may be a novel biomarker for high-grade TNBC associated with mesenchymal marker expression and cancer stemness.

A Novel Trojan Horse Nanotherapy Strategy Targeting the cPKM-STMN1/TGFB1 Axis for Effective Treatment of Intrahepatic Cholangiocarcinoma.

Intrahepatic cholangiocarcinoma (ICC) is characterized by its dense fibrotic microenvironment and highly malignant nature, which are associated with chemotherapy resistance and very poor prognosis. Although circRNAs have emerged as important regulators in cancer biology, their role in ICC remains largely unclear. Herein, a circular RNA, cPKM is identified, which is upregulated in ICC and associated with poor prognosis. Silencing cPKM in ICC cells reduces TGFB1 release and stromal fibrosis, inhibits STMN1 expression, and suppresses ICC growth and metastasis, moreover, it also leads to overcoming paclitaxel resistance. This is regulated by the interactions of cPKM with miR-199a-5p or IGF2BP2 and by the ability of cPKM to stabilize STMN1/TGFB1 mRNA. Based on these findings, a Trojan horse nanotherapy strategy with co-loading of siRNA against cPKM (si-cPKM) and paclitaxel (PTX) is developed. The siRNA/PTX co-loaded nanosystem (Trojan horse) efficiently penetrates tumor tissues, releases si-cPKM and paclitaxel (soldiers), promotes paclitaxel sensitization, and suppresses ICC proliferation and metastasis in vivo. Furthermore, it alleviates the fibrosis of ICC tumor stroma and reopens collapsed tumor vessels (opening the gates), thus enhancing the efficacy of the standard chemotherapy regimen (main force). This novel nanotherapy provides a promising new strategy for ICC treatment.

The C-terminus of stathmin-like proteins governs the stability of their complexes with tubulin.

Microtubule dynamics is modulated by many cellular factors including stathmin family proteins. Vertebrate stathmins sequester two αß-tubulin heterodimers into a tight complex that cannot be incorporated in microtubules. Stathmins are regulated at the expression level during development and among tissues; they are also regulated by phosphorylation. Here, we study the dissociation kinetics of tubulin:stathmin assemblies in presence of different tubulin-binding proteins and identify a critical role of the C-terminus of the stathmin partner. Destabilizing this C-terminal region may represent an additional regulatory mechanism of the interaction with tubulin of stathmin proteins.

Hsa_circ_0119412 is a tumor promoter in hepatocellular carcinoma by inhibiting miR-526b-5p to upregulate STMN1.

Hepatocellular carcinoma (HCC) is always deemed a deadly malignancy worldwide. Non-coding RNAs, including circRNAs, are becoming more widely recognized as essential regulators of the malignant development of HCC. Thus, we elaborated the regulating role of hsa_circ_0119412 in HCC advancement. The qRT-PCR was done to estimate the expressions of hsa_circ_0119412, miR-526b-5p, and Stathmin 1 (STMN1) in HCC (clinical samples and cell lines), and immunoblotting was used to detect STMN1 protein level in HCC cell lines. The stability of the circRNA was checked by processing with ribonuclease R. The proliferative potential of HCC cells was examined via the CCK-8 assay and the migratory potential by the wound healing assay. Immunoblotting was done to examine Bax and Bcl-2 (apoptosis-related proteins). Luciferase and RIP assays were employed to establish the direct interactions among miR-526b-5p and hsa_circ 0119412/STMN1. In vivo tumor growth was measured by doing a xenograft tumor experiment. In the tissues of HCC patients and cell lines derived from HCC cells, hsa_circ_0119412 was distinctly over-expressed. Knocking down hsa_circ_0119412 impeded proliferation and migration while inducing apoptosis in HCC cells. Moreover, silencing hsa_circ_0119412 diminished tumor weight and volume in vivo. Interestingly, miR-526b-5p inhibition partially restored the anti-tumor effects of silencing hsa_circ_0119412. STMN1 expression was also abundant in HCC, suggesting that it play a tumor-promoting role. Mechanistically, hsa_circ_0119412 sponged miR-526b-5p, resulting in STMN1 upregulation and thus facilitating the progression of HCC. In conclusion, this study reveals that hsa_circ_0119412 knockdown attenuates the progression of HCC by targeting miR-526b-5p/STMN1 axis.