Reduced STMN2 and pathogenic TDP-43, two hallmarks of ALS, synergize to accelerate motor decline in mice

Pathological TDP-43 loss from the nucleus and cytoplasmic aggregation occurs in almost all cases of ALS and half of frontotemporal dementia patients. Stathmin2 (Stmn2) is a key target of TDP-43 regulation and aberrantly spliced Stmn2 mRNA is found in patients with ALS, frontotemporal dementia, and Alzheimer's Disease. STMN2 participates in the axon injury response and its depletion in vivo partially replicates ALS-like symptoms including progressive motor deficits and distal NMJ denervation. The interaction between STMN2 loss and TDP-43 dysfunction has not been studied in mice because TDP-43 regulates human but not murine Stmn2 splicing. Therefore, we generated trans-heterozygous mice that lack one functional copy of Stmn2 and express one mutant TDP-43Q331K knock-in allele to investigate whether reduced STMN2 function exacerbates TDP-43-dependent pathology. Indeed, we observe synergy between these two alleles, resulting in an early onset, progressive motor deficit. Surprisingly, this behavioral defect is not accompanied by detectable neuropathology in the brain, spinal cord, peripheral nerves or at neuromuscular junctions (NMJs). However, the trans-heterozygous mice exhibit abnormal mitochondrial morphology in their distal axons and NMJs. As both STMN2 and TDP-43 affect mitochondrial dynamics, and neuronal mitochondrial dysfunction is a cardinal feature of many neurodegenerative diseases, this abnormality likely contributes to the observed motor deficit. These findings demonstrate that partial loss of STMN2 significantly exacerbates TDP-43-associated phenotypes, suggesting that STMN2 restoration could ameliorate TDP-43 related disease before the onset of degeneration.

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.

STNM1 in human cancers: role, function and potential therapy sensitizer

STMN1 belongs to the stathmin gene family, it encodes a cytoplasmic phosphorylated protein, stathmin1, which is commonly observed in vertebrate cells. STMN1 is a structural microtubule-associated protein (MAP) that binds to microtubule protein dimers rather than microtubules, with each STMN1 binding two microtubule protein dimers and preventing their aggregation, leading to microtubule instability. STMN1 expression is elevated in a number of malignancies, and inhibition of its expression can interfere with tumor cell division. Its expression can change the division of tumor cells, thereby arresting cell growth in the G2/M phase. Moreover, STMN1 expression affects tumor cell sensitivity to anti-microtubule drug analogs, including vincristine and paclitaxel. The research on MAPs is limited, and new insights on the mechanism of STMN1 in different cancers are emerging. The effective application of STMN1 in cancer prognosis and treatment requires further understanding of this protein. Here, we summarize the general characteristics of STMN1 and outline how STMN1 plays a role in cancer development, targeting multiple signaling networks and acting as a downstream target for multiple microRNAs, circRNAs, and lincRNAs. We also summarize recent findings on the function role of STMN1 in tumor resistance and as a therapeutic target for cancer.

A systematic analysis of microtubule-destabilizing factors during dendrite pruning in Drosophila

It has long been thought that microtubule disassembly, one of the earliest cellular events, contributes to neuronal pruning and neurodegeneration in development and disease. However, how microtubule disassembly drives neuronal pruning remains poorly understood. Here, we conduct a systematic investigation of various microtubule-destabilizing factors and identify exchange factor for Arf6 (Efa6) and Stathmin (Stai) as new regulators of dendrite pruning in ddaC sensory neurons during Drosophila metamorphosis. We show that Efa6 is both necessary and sufficient to regulate dendrite pruning. Interestingly, Efa6 and Stai facilitate microtubule turnover and disassembly prior to dendrite pruning without compromising the minus-end-out microtubule orientation in dendrites. Moreover, our pharmacological and genetic manipulations strongly support a key role of microtubule disassembly in promoting dendrite pruning. Thus, this systematic study highlights the importance of two selective microtubule destabilizers in dendrite pruning and substantiates a causal link between microtubule disassembly and neuronal pruning.

A review on the role of tau and stathmin in gastric cancer metastasis

Gastric cancer is resistant to chemotherapy, especially in the later stages. The prevalence of gastric cancer increases after the age of 40, and its peak is in the 7th decade of life. The proteins tau (tubulin associated unit) and stathmin are overexpressed in gastric cancer and contribute to the progression of the disease by increasing cancer cell proliferation, invasion, and inducing drug resistance. This review summarizes the current knowledge on the expression of tau protein and stathmin in gastric cancer and their roles in drug resistance. Medline and PubMed databases were searched from 1990 till February 2021 for the terms "tau protein", "stathmin", and "gastric cancer." Two reviewers screened all articles and assessed prognostic studies on the role of tau and stathmin proteins in gastric cancer progression. Collectively, studies reported that both proteins are expressed at different concentrations in gastric cancer and could be significant molecular biomarkers for prognosis. Both proteins could be good candidates for targeted therapy of gastric cancer and are associated with resistance to taxanes.

The effect of fish oil on social interaction memory in total sleep-deprived rats with respect to the hippocampal level of stathmin, TFEB, synaptophysin and LAMP-1 proteins

Fish oil (FO) is one of the richest natural sources of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). DHA is essential for brain functions and EPA has been approved for brain health. On the other hand, stathmin, TFEB, synaptophysin and LAMP-1 proteins are involved in synaptic plasticity, lysosome biogenesis and synaptic vesicles biogenesis. In this study, we aimed to investigate the effect of FO on social interaction memory in sleep-deprived rats with respect to level of stathmin, TFEB, synaptophysin and LAMP-1 in the hippocampus of rats. All rats received FO through oral gavage at the doses of 0.5, 0.75 and 1 mg/kg. The water box was used to induce total sleep deprivation (TSD) and the three-chamber paradigm test was used to assess social behavior. Hippocampal level of proteins was assessed using Western blot. The results showed, FO impaired social memory at the dose of 1 mg/kg in normal and sham groups. SD impaired social memory and FO did not restore this effect. Furthermore, FO at the dose of 0.75 mg/kg decreased social affiliation and social memory in all groups of normal rats, compared with related saline groups, and at the dose of 1 mg/kg impaired social memory for stranger 2 compared with saline group. In sham groups, FO at the dose of 1 mg/kg impaired social memory for stranger 2 compared with saline group. SD decreased hippocampal level of all proteins (except stathmin), and FO (1 mg/kg) restored these effects. In conclusion, FO negatively affects social interaction memory in rats.

Stathmin Regulates Spatiotemporal Variation in the Memory Loop in Single-Prolonged Stress Rats

Posttraumatic stress disorder (PTSD) is closely related to brain structures of the memory loop such as the hippocampus, amygdala, and medial prefrontal cortex (mPFC). The fear gene stathmin plays an important role in regulating fear memory. However, whether the fear gene stathmin is related to fear memory loop anomalies caused by PTSD is unclear. A single-prolonged stress (SPS) rat model of PTSD was constructed. Wistar rats were randomly divided into 5 groups: the control group, SPS 1-day group, SPS 4-day group, SPS 7-day group, and SPS 14-day group. Then, we measured the protein and mRNA expression of stathmin, p-stathmin (Ser16, Ser25, Ser38, and Ser63), β-tubulin, and MAP-1B in the hippocampus, amygdala, and mPFC in the 5 groups by immunohistochemistry, Western blotting, and qRT-PCR. The expression of the stathmin protein in the hippocampus, mPFC, and amygdala of the rat memory loop decreased gradually in the SPS 1-day group, the SPS 4-day group, and the SPS 7-day group, in which it was the lowest, and then increased. The trend of the expression of stathmin mRNA in the three areas of the memory loop was consistent with the trend of the expression of the stathmin protein. The trend of the protein expression of p-stathmin (Ser25 and Ser38) was opposite of that of stathmin; it reached a peak on the 7th day, and then decreased in the hippocampus. The protein expression of p-stathmin (Ser63) showed the same trend in the mPFC. The protein and mRNA expression of β-tubulin and MAP-1B was consistent with that of p-stathmin; it reached a peak on the 7th day, and then decreased in the rat hippocampus, mPFC, and amygdala. Stathmin in the memory loop, especially in the hippocampus, regulates microtubule structure through its phosphorylation at Ser25 and Ser38 and thereby participates in the mediation of fear memory abnormalities in PTSD.

Karyopherin α2-dependent import of E2F1 and TFDP1 maintains protumorigenic stathmin expression in liver cancer

Background

Members of the karyopherin superfamily serve as nuclear transport receptors/adaptor proteins and provide exchange of macromolecules between the nucleo- and cytoplasm. Emerging evidence suggests a subset of karyopherins to be dysregulated in hepatocarcinogenesis including karyopherin-α2 (KPNA2). However, the functional and regulatory role of KPNA2 in liver cancer remains incompletely understood.

Methods

Quantitative proteomics (LC-MS/MS, ~ 1750 proteins in total) was used to study changes in global protein abundance upon siRNA-mediated KPNA2 knockdown in HCC cells. Functional and mechanistic analyses included colony formation and 2D migration assays, co-immunoprecipitation (CoIP), chromatin immunoprecipitation (ChIP), qRT-PCR, immmunblotting, and subcellular fractionation. In vitro results were correlated with data derived from a murine HCC model and HCC patient samples (3 cohorts, n > 600 in total).

Results

The proteomic approach revealed the pro-tumorigenic, microtubule (MT) interacting protein stathmin (STMN1) among the most downregulated proteins upon KPNA2 depletion in HCC cells. We further observed that KPNA2 knockdown leads to reduced tumor cell migration and colony formation of HCC cells, which could be phenocopied by direct knockdown of stathmin. As the underlying regulatory mechanism, we uncovered E2F1 and TFDP1 as transport substrates of KPNA2 being retained in the cytoplasm upon KPNA2 ablation, thereby resulting in reduced STMN1 expression. Finally, murine and human HCC data indicate significant correlations of STMN1 expression with E2F1/TFPD1 and with KPNA2 expression and their association with poor prognosis in HCC patients.

Conclusion

Our data suggest that KPNA2 regulates STMN1 by import of E2F1/TFDP1 and thereby provide a novel link between nuclear transport and MT-interacting proteins in HCC with functional and prognostic significance.

The human T-cell leukemia virus type-1 tax oncoprotein dissociates NF-κB p65RelA-Stathmin complexes and causes catastrophic mitotic spindle damage and genomic instability

Genomic instability is a hallmark of many cancers; however, the molecular etiology of chromosomal dysregulation is not well understood. The human T-cell leukemia virus type-1 (HTLV-1) oncoprotein Tax activates NF-κB-signaling and induces DNA-damage and aberrant chromosomal segregation through diverse mechanisms which contribute to viral carcinogenesis. Intriguingly, Stathmin/oncoprotein-18 (Op-18) depolymerizes tubulin and interacts with the p65^RelA subunit and functions as a cofactor for NF-κB-dependent transactivation. We thus hypothesized that the dissociation of p65^RelA-Stathmin/Op-18 complexes by Tax could lead to the catastrophic destabilization of microtubule (MT) spindle fibers during mitosis and provide a novel mechanistic link between NF-κB-signaling and genomic instability. Here we report that the inhibition of Stathmin expression by the retroviral latency protein, p30^II, or knockdown with siRNA-stathmin, dampens Tax-mediated NF-κB transactivation and counters Tax-induced genomic instability and cytotoxicity. The Tax-G148V mutant, defective for NF-κB activation, exhibited reduced p65^RelA-Stathmin binding and diminished genomic instability and cytotoxicity. Dominant-negative inhibitors of NF-κB also prevented Tax-induced multinucleation and apoptosis. Moreover, cell clones containing the infectious HTLV-1 ACH. p30^II mutant provirus, impaired for p30^II production, exhibited increased multinucleation and the accumulation of cytoplasmic tubulin aggregates following nocodozole-treatment. These findings allude to a mechanism whereby NF-κB-signaling regulates tubulin dynamics and mitotic instability through the modulation of p65^RelA-Stathmin/Op-18 interactions, and support the notion that p30^II enhances the survival of Tax-expressing HTLV-1-transformed cells.

Stathmin regulates the proliferation and odontoblastic/osteogenic differentiation of human dental pulp stem cells through Wnt/β-catenin signaling pathway

Odontoblastic/osteogenic differentiation of human dental pulp stem cells (hDPSCs) is a key factor in tooth and pulp regeneration, but its mechanism still remains unknown. The purpose of this research is to look into the mechanism by which Stathmin affects the proliferation and odontoblastic/osteogenic differentiation of hDPSCs, and whether the Wnt/β- catenin is related to this regulation. First, the Stathmin expression was inhibited by lentiviral vector, after that the transcriptome sequencing technology was used to screen the differentially expressed genes, then we found Wnt5a which related to the regulation of Wnt/β-catenin was regulated. Comparing with hDPSC in the control group, the shRNA-Stathmin group inhibited proliferation and odontoblastic/osteogenic differentiation. The result of molecular analysis indicated that the Wnt/β-catenin was inhibited when Stathmin was silenced. After that, the shRNA-Stathmin group were added with LiCl (activator of Wnt/β-catenin), and the Wnt/β-catenin was significantly activated in β-catenin. After activation of the Wnt/β-catenin, the proliferation of hDPSCs was significantly increased and the expression of genes related to odontoblastic/osteogenic differentiation was also significantly increased. Taken together, these findings reveal for the first time that the Stathmin-Wnt/β-catenin plays a positive regulatory role in hDPSC proliferation and odontoblastic/osteogenic differentiation. SIGNIFICANCE: Transcriptome sequencing revealed that Stathmin interacts with Wnt/β-catenin signaling pathway-related proteins such as Wnt5a. At the same time, experiments have confirmed that Stathmin protein can affect the proliferation and odontogenetic differentiation of hDPSCs.The innovation of this paper is to link the Stathmin and Wnt/β-catenin signaling pathways for the first time, to explore the interaction of Stathmin and Wnt/β-catenin signaling pathways and the mechanism of this regulation on human dental pulp stem cells (hDPSCs) of odontoblastic/osteogenic differentiation and proliferation function. Especially for the regulation of odontoblastic/osteogenic differentiation, we have verified this mechanism at the molecular level and characterization leveland this regulation also provides new ideas for dental pulp tissue engineering. At the same time, more than 3000 proteins related to the change of Stathmin level were screened by transcriptome sequencing technology, which provided a possibility to further exploration of the regulation mechanism of Stathmin on various aspects of cell biological characteristics.

p27kip1 at the crossroad between actin and microtubule dynamics

The p27^kip1 protein, mainly known as a negative regulator of cell proliferation, has also been involved in the control of other cellular processes, including the regulation of cytoskeleton dynamics. Notably, these two functions involve distinct protein domains, residing in the N- and C-terminal halves, respectively. In the last two decades, p27^kip1 has been reported to interact with microtubule and acto-myosin cytoskeletons, both in direct and indirect ways, overall drawing a picture in which several factors play their role either in synergy or in contrast one with another. As a result, the role of p27^kip1 in cytoskeleton dynamics has been implicated in cell migration, both in physiologic and in neoplastic contexts, modulating cytokinesis, lipid raft trafficking, and neuronal development. Recently, two distinct papers have further reported a central role for p27^kip1 in the control of microtubule stability and post-translational modifications, dissecting the interaction between p27^kip1 and α-tubulin-acetyl-transferase (α-TAT), an enzyme involved in the stability of microtubules, and protein-regulator of cytokinesis 1 (PRC1), a nuclear regulator of the central spindle during mitosis. In light of these recent evidences, we will comment on the role of p27^kip1 on cytoskeleton regulation and its implication for cancer progression.

Characterization of Microtubule-Associated Proteins (MAPs) and Tubulin Interactions by Isothermal Titration Calorimetry (ITC)

Microtubules are highly dynamic structures which play a central role in many cellular processes such as cell division, intracellular transport, and migration. Their dynamics is tightly regulated by stabilizing and destabilizing microtubule-associated proteins (MAPs), such as tau and stathmin. Many approaches have been developed to study interactions between tubulin and MAPs. However, isothermal titration calorimetry (ITC) is the only direct thermodynamic method that enables a full thermodynamic characterization of the interaction after a single titration experiment. We provide here the protocols to apply ITC to tubulin interaction with either stathmin or tau, which will help to avoid the common pitfalls in this very powerful and sensitive method.

Stathmin recruits tubulin to Listeria monocytogenes-induced actin comets and promotes bacterial dissemination

The tubulin cytoskeleton is one of the main components of the cytoarchitecture and is involved in several cellular functions. Here, we examine the interplay between Listeria monocytogenes (Lm) and the tubulin cytoskeleton upon cellular infection. We show that non-polymeric tubulin is present throughout Lm actin comet tails and, to a less extent, in actin clouds. Moreover, we demonstrate that stathmin, a regulator of microtubule dynamics, is also found in these Lm-associated actin structures and is required for tubulin recruitment. Depletion of host stathmin results in longer comets containing less F-actin, which may be correlated with higher levels of inactive cofilin in the comet, thus suggesting a defect on local F-actin dynamics. In addition, intracellular bacterial speed is significantly reduced in stathmin-depleted cells, revealing the importance of stathmin/tubulin in intracellular Lm motility. In agreement, the area of infection foci and the total bacterial loads are also significantly reduced in stathmin-depleted cells. Collectively, our results demonstrate that stathmin promotes efficient cellular infection, possibly through tubulin recruitment and control of actin dynamics at Lm-polymerized actin structures.

The effect of downregulation of Stathmin gene on biological behaviors of U373 and U87-MG glioblastoma cells

Background

Stathmin as a critical protein involved in microtubule polymerization, is necessary for survival of cancer cells. However, extremely little is known about Stathmin in glioblastoma. So, this study was designed to elucidate the function of Stathmin gene in the tumorigenesis and progression of glioblastoma cells.

Method

The lentiviral interference vector pLV3-si-Stathmin targeting Stathmin gene and the control vector pLV3-NC were established for the co-transfection of 293T cells together with the helper plasmids. Viral titer was determined via limiting dilution assay. Then pLV3-si-Stathmin and pLV3-NC were stably co-transfected into U373 and U87-MG glioblastoma cells. Expression levels of Stathmin protein in each group were determined by using Western Blot, and the proliferation and migration ability of the cells with downregulated Stathmin were evaluated through CCK8 assay and transwell invasion assay, respectively. Cell cycles and cell apoptosis were detected with flow cytometry. Finally, the effect of Stathmin in tumor formation was determined in nude mice.

Result

DNA sequencing and viral titer assay indicated that the lentiviral interference vector was successfully established with a viral titer of 4 × 10⁸ TU/ml. According to the results from Western Blotting, Stathmin protein expression level decreased significantly in the U373 and U87-MG cells after transfected with pLV3-si-Stathmin, respectively, compared with those transfected with pLV3-NC. In glioblastoma cells, the cell proliferation and migration were greatly inhibited after the downregulation of Stathmin protein. Flow cytometry showed that much more cells were arrested in G2/M phasein Stathmin downregulated group, compared with the non-transfection group and NC group. But Stathmin downregulation did not induce significant cell apoptosis. Tumor formation assay in nude mice showed that tumor formation was delayed after Stathmin downregulation, with a reduction in both tumor formation rate and tumor growth velocity.

Conclusion

Stathmin downregulation affected the biological behaviors of U373 and U87-MG glioblastoma cells, inhibiting the proliferation and migration of tumor cells. Stathmin gene may serve as a potential target in gene therapy for glioblastoma.

Stathmin inhibits proliferation and differentiation of dental pulp stem cells via sonic hedgehog/Gli

The mineralization of dental pulp stem cells is an important factor in the tissue engineering of teeth, but the mechanism is not yet obvious. This study aimed to identify the effect of Stathmin on the proliferation and osteogenic/odontoblastic differentiation of human dental pulp stem cells (hDPSCs) and to explore whether the Shh signalling pathway was involved in this regulation. First, Stathmin was expressed in the cytoplasm and on the cell membranes of hDPSCs by cell immunofluorescence. Then, by constructing a lentiviral vector, the expression of Stathmin in hDPSCs was inhibited. Treatment with Stathmin shRNA (shRNA‐Stathmin group) inhibited the ability of hDPSCs to proliferate, as demonstrated by a CCK8 assay and flow cytometry analysis, and suppressed the osteogenic/odontoblastic differentiation ability, as demonstrated by alizarin red S staining and osteogenic/odontoblastic differentiation‐related gene (ALP, BSP, OCN, DSPP) activity, compared to that of hDPSCs from the control shRNA group. Molecular analyses showed that the Shh/GLI1 signalling pathway was inhibited when Stathmin was silenced, and purmorphamine, the Shh signalling pathway activator, was added to hDPSCs in the shRNA‐Stathmin group, real‐time PCR and Western blotting confirmed that expression of Shh and its downstream signalling molecules PTCH1, SMO and GLI1 increased significantly. After activating the Shh signalling pathway, the proliferation of hDPSCs increased markedly, as demonstrated by a CCK8 assay and flow cytometry analysis; osteogenic/odontoblastic differentiation‐related gene (ALP, BSP, OCN, DSPP) expression also increased significantly. Collectively, these findings firstly revealed that Stathmin‐Shh/GLI1 signalling pathway plays a positive role in hDPSC proliferation and osteogenic/odontoblastic differentiation.

Increased stathmin correlates with advanced stage and poor survival of non-small cell lung cancer

BACKGROUND

Previous studies show that overexpression of stathmin involved in the malignant biological behavior of lung cancer. This investigation is to disclose the expression status of stathmin in non-small cell lung cancer (NSCLC) and its clinical value for the diagnosis and prognosis to lung cancer.

METHODS

The expression of stathmin in cells and tissues of NSCLC was examined using immunohistochemistry (IHC), in-situ hybridization (ISH), and Western blot. The correlation between stathmin expression and survival of lung cancer patients was evaluated by a Kaplan-Meier method and the multiple regression analysis.

RESULTS

NSCLC tissues and cells showed an overexpression of stathmin compared with normal lung tissues and cells (p< 0.05). And the expression level of stathmin was significantly associated with lung adenocarcinoma (LAC) (p< 0.05), lymphatic invasion (p< 0.05) and advanced stages of NSCLC (p< 0.05). Moreover, overexpression of stathmin predicted a reduced survival (p<0.05).

CONCLUSION

Increased stathmin correlated with pathologic grade, lymphatic invasion, advanced stage and poor survival of NSCLC, which indicated that stathmin could serve as a potential biomarker of NSCLC.

Standardized Cannabis sativa extract attenuates tau and stathmin gene expression in the melanoma cell line

Objective(s):

Metastasis is the main cause of death in patients with melanoma. Cannabis-based medicines are effective adjunctive drugs in cancer patients. Tau and Stathmin proteins are the key proteins in cancer metastasis. Here we have investigated the effect of a standardized Cannabis sativa extract on cell migration and Tau and Stathmin gene expression in the melanoma cell line.

Materials and Methods:

In the treatment group, melanoma (B1617) was treated 48 hr with various concentrations of standardized C. sativa extract. Cells with no treatment were considered as the control group, then study was followed by Quantitative RT-Real Time PCR assay. Relative gene expression was calculated by the ΔΔct method. Migration assay was used to evaluate cancer metastasis.

Results:

Tau and stathmin gene expression was significantly decreased compared to the control group. Cell migration was also significantly reduced compared to controls.

Conclusion:

C. sativa decreased tau and stathmin gene expression and cancer metastasis. The results may have some clinical relevance for the use of cannabis-based medicines in patients with metastatic melanoma.

Stathmin decreases cholangiocarcinoma cell line sensitivity to staurosporine-triggered apoptosis via the induction of ERK and Akt signaling

Cholangiocarcinoma is a rare, but highly fatal malignancy. However, the intrinsic mechanism involved in its tumorigenesis remains obscure. An urgent need remains for a promising target for cholangiocarcinoma biological therapies. Based on comparative proteomical technologies, we found 253 and 231 different spots in gallbladder tumor cell lines and cholangiocarcinoma cell lines, respectively, relative to non-malignant cells. Using Mass Spectrometry (MS) and database searching, we chose seven differentially expressed proteins. High Stathmin expression was found in both cholangiocarcinoma and gallbladder carcinoma cells. Stathmin expression was validated using immunohistochemistry and western blot in cholangiocarcinoma tissue samples and peritumoral tissue. It was further revealed that high Stathmin expression was associated with the repression of staurosporine-induced apoptosis in the cholangiocarcinoma cell. Moreover, we found that Stathmin promoted cancer cell proliferation and inhibited its apoptosis through protein kinase B (Akt) and extracellular signal-regulated kinase (ERK) signaling. Integrin, β1 appears to serve as a partner of Stathmin induction of ERK and Akt signaling by inhibiting apoptosis in the cholangiocarcinoma cell. Understanding the regulation of anti-apoptosis effect by Stathmin might provide new insight into how to overcome therapeutic resistance in cholangiocarcinoma.

Stathmin is overexpressed and regulated by mutant p53 in oral squamous cell carcinoma

Background

The aim of this study was to investigate the oncogenic function and regulatory mechanism of stathmin in oral squamous cell carcinoma (OSCC).

Methods

Two-dimensional electrophoresis and liquid chromatography-tandem mass chromatography were applied to screen differentiated proteins during carcinogenesis in OSCC. Cell Counting Kit-8 (CCK-8) assays, colony formation, migration, flow cytometry, immunofluorescence and a xenograft model were used to detect the function of stathmin. The correlation between stathmin and p53 expression was analyzed using immunohistochemistry. Mutant/wild type p53 plasmids and small interfering RNA were used to examine the regulation of stathmin. Chromatin immunoprecipitation assays and luciferase assays were performed to detect the transcriptional activation of stathmin by p53.

Results

Overexpression of stathmin was screened and confirmed in OSCC patients and cell lines. Silencing expression of stathmin inhibited proliferation, colony formation and migration and promoted apoptosis. Poly ADP ribose polymerase (PARP) and cyclin-dependent kinase 1 (cdc2) were activated after silencing the expression of stathmin. Suppression of tumorigenicity was also confirmed in vivo. Mutant p53 transcriptionally activated the expression of stathmin in HN6 and HN13 cancer cells, but not in HN30 cells harboring wild type p53.

Conclusions

These results suggest that stathmin acts as an oncogene and is transcriptionally regulated by mutant p53, but not by wild-type p53. Stathmin could be a potential anti-tumor therapeutic target in OSCC.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0575-4) contains supplementary material, which is available to authorized users.

Siva 1 inhibits proliferation, migration and invasion by phosphorylating Stathmin in ovarian cancer cells

Ovarian cancer is one of the most common types of gynecologic malignant tumor, with high incidence and high mortality rates. It is difficult to diagnose ovarian cancer early due to the complex structure and function of the ovaries. Siva 1 is a well-known pro-apoptosis protein that functions in multiple types of cancer cells: There are several studies demonstrating that Siva 1 arrests apoptosis and facilitates cancer development in osteosarcoma and non-small cell lung cancer. Whether Siva 1 functions in ovarian cancer remains unknown. In the present study, it was established that Siva 1 was stably overexpressed in ovarian cancer cell lines, and demonstrated that the overexpression of Siva 1 inhibited proliferation, promoted apoptosis and suppressed migration and invasion by facilitating phosphorylation of Stathmin and polymerization of α-tubulin in ovarian cancer cells. These data provide specific novel insights into the molecular mechanism of ovarian cancer, and may be of significance for the clinical diagnosis and therapy of ovarian cancer.

High stathmin expression is a marker for poor clinical outcome in endometrial cancer: An NRG oncology group/gynecologic oncology group study

OBJECTIVE

Gynecologic Oncology Group (GOG) 177 demonstrated that addition of paclitaxel to a backbone of adriamycin/cisplatin improves overall survival (OS) and progression-free survival (PFS) for patients with advanced or recurrent endometrial cancer. Using patient specimens from GOG-177, our objective was to identify potential mechanisms underlying the improved clinical response to taxanes. Stathmin (STMN1) is a recognized poor prognostic marker in endometrial cancer that functions as a microtubule depolymerizing protein, allowing cells to transit rapidly through mitosis. Therefore, we hypothesized that one possible mechanism underlying the beneficial effects of paclitaxel could be to counter the impact of stathmin.

METHODS

We analyzed the expression of stathmin by immunohistochemistry (IHC) in 69 specimens from patients enrolled on GOG-177. We also determined the correlation between stathmin mRNA expression and clinical outcomes in The Cancer Genome Atlas (TCGA) dataset for endometrial cancer.

RESULTS

We first established that stathmin expression was significantly associated with shorter PFS and OS for all analyzed cases in both GOG-177 and TCGA. However, subgroup analysis from GOG-177 revealed that high stathmin correlated with poor PFS and OS particularly in patients who received adriamycin/cisplatin only. In contrast, there was no statistically significant association between stathmin expression and OS or PFS in patients treated with paclitaxel/adriamycin/cisplatin.

CONCLUSIONS

Our findings demonstrate that high stathmin expression is a poor prognostic marker in endometrial cancer. Paclitaxel may help to negate the impact of stathmin overexpression when treating high risk endometrial cancer cases.

p27kip1: An all-round tumor suppressor

Our recent study has uncovered an additional mechanism by which the cell cycle inhibitor p27kip1 controls cell proliferation. Through its effect on the activity of the microtubule destabilizing protein Stathmin, p27kip1 modulates full H-Ras activation and, as a consequence, the MAPK signaling cascade. This regulatory mechanism influences the cell cycle in vitro and tissue and/or organ growth in mice, in vivo and, when unbalanced, may lead to uncontrolled proliferation and tumor onset.

Stathmin-dependent molecular targeting therapy for malignant tumor: the latest 5 years' discoveries and developments

Knowledge of the molecular mechanisms on malignant tumors is very critical for the development of new treatment strategies like molecularly targeted therapies. In last 5 years, many investigations suggest that stathmin is over-expressed in a variety of human malignant tumors, and potentially promotes the occurrence and development of tumors. Rather, down-regulation of stathmin can reduce cell proliferation, motility and metastasis and induce apoptosis of malignant tumors. Thus, a stathmin antagonist, such as a specific inhibitor (antibody, small molecule compound, peptide, or siRNA), may be a novel strategy of molecular targeted therapy. This review summarizes the research progress of recent 5 years on the role of stathmin in tumorigenesis, the molecular mechanisms and development of anti-stathmin treatment, which suggest that continued investigations into the function of stathmin in the tumorigenesis could lead to more rationally designed therapeutics targeting stathmin for treating human malignant tumors.

Neurofilament depletion improves microtubule dynamics via modulation of Stat3/stathmin signaling

In neurons, microtubules form a dense array within axons, and the stability and function of this microtubule network is modulated by neurofilaments. Accumulation of neurofilaments has been observed in several forms of neurodegenerative diseases, but the mechanisms how elevated neurofilament levels destabilize axons are unknown so far. Here, we show that increased neurofilament expression in motor nerves of pmn mutant mice, a model of motoneuron disease, causes disturbed microtubule dynamics. The disease is caused by a point mutation in the tubulin-specific chaperone E (Tbce) gene, leading to an exchange of the most C-terminal amino acid tryptophan to glycine. As a consequence, the TBCE protein becomes instable which then results in destabilization of axonal microtubules and defects in axonal transport, in particular in motoneurons. Depletion of neurofilament increases the number and regrowth of microtubules in pmn mutant motoneurons and restores axon elongation. This effect is mediated by interaction of neurofilament with the stathmin complex. Accumulating neurofilaments associate with stathmin in axons of pmn mutant motoneurons. Depletion of neurofilament by Nefl knockout increases Stat3–stathmin interaction and stabilizes the microtubules in pmn mutant motoneurons. Consequently, counteracting enhanced neurofilament expression improves axonal maintenance and prolongs survival of pmn mutant mice. We propose that this mechanism could also be relevant for other neurodegenerative diseases in which neurofilament accumulation and loss of microtubules are prominent features.

The phosphorylation-specific association of STMN1 with GRP78 promotes breast cancer metastasis

Metastasis is a major cause of death in patients with breast cancer. Stathmin1 (STMN1) is a phosphoprotein associated with cancer metastasis. It exhibits a complicated phosphorylation pattern in response to various extracellular signals, but its signaling mechanism is poorly understood. In this study, we report that phosphorylation of STMN1 at Ser25 and Ser38 is necessary to maintain cell migration capabilities and is associated with shorter disease-free survival (DFS) in breast cancer. In addition, we report that glucose-regulated protein of molecular mass 78 (GRP78) is a novel phospho-STMN1 binding protein upon STMN1 Ser25/Ser38 phosphorylation. This phosphorylation-dependent interaction is regulated by MEK kinase and is required for STMN1-GRP78 complex stability and STMN1-mediated migration. We also propose a prognostic model based on phospho-STMN1 and GRP78 to assess metastatic risk in breast cancer patients.

A randomized phase II non-comparative study of PF-04691502 and gedatolisib (PF-05212384) in patients with recurrent endometrial cancer

OBJECTIVE

PF-04691502 and gedatolisib (PF-05212384) are potent, dual PI3K/mTOR inhibitors. This phase II study (B1271004) was conducted in patients with recurrent endometrial cancer following platinum-containing chemotherapy. The primary endpoint was to assess clinical benefit response (complete or partial response, or stable disease for ≥16weeks) following treatment with PF-04691502 or gedatolisib.

METHODS

The main study consisted of four independent arms based on a Simon two-stage design. Patients were assigned to putative PI3K-basal (PF-04691502 or gedatolisib) or PI3K-activated (PF-04691502 or gedatolisib) arms based on stathmin-low or stathmin-high tumor expression, respectively. Japanese patients were also enrolled in a separate lead-in cohort.

RESULTS

In stage 1 (main study), eighteen patients were randomized to PF-04691502 and 40 to gedatolisib. The two PF-04691502 arms were discontinued early due to unacceptable toxicity, including pneumonia and pneumonitis. The most common treatment-related adverse events associated with gedatolisib were nausea (53%), mucosal inflammation (50%), decreased appetite (40%), diarrhea (38%), fatigue (35%), and dysgeusia and vomiting (each 30%). Clinical benefit response rate was 53% (10/19) in the gedatolisib/stathmin-low arm and 26% (5/19) in the gedatolisib/stathmin-high arm. Safety profile and pharmacokinetic characteristics of both drugs in the Japanese lead-in cohort were comparable to the Western population.

CONCLUSIONS

Gedatolisib administered by weekly intravenous infusion demonstrated acceptable tolerability and moderate activity in patients with recurrent endometrial cancer. PF-04691502 daily oral dosing was not well tolerated. Clinical benefit response criteria for proceeding to stage 2 were only met in the gedatolisib/stathmin-low arm. Stathmin-high expression did not correlate with greater treatment efficacy. ClinicalTrials.gov registration ID: NCT01420081.

Stathmin involvement in the maternal embryonic leucine zipper kinase pathway in glioblastoma

Background

Maternal Embryonic Leucine Zipper Kinase (MELK) is a serine/threonine kinase involved in cell cycle, differentiation, proliferation, and apoptosis. These multiple features are consistent with it being a potential anticancer target. Nevertheless, the MELK pathway in tumorigenesis is not yet completely understood. This study aims to identify proteins associated with MELK pathway in astrocytomas. To this end, proteomic data of the human glioma cell line U87MG transfected with siRNA for MELK were compared with non-target transfected control cells and compared with oligonucleotide microarray data.

Results

In both assays, we identified stathmin/oncoprotein 18 (STMN1), involved in cell cycle. STMN1 gene expression was further assessed in a series of 154 astrocytomas and 22 non-neoplastic brain samples by qRT-PCR. STMN1 expression was significantly increased in malignant diffusely infiltrative astrocytomas compared with pilocytic astrocytoma (p < 0.0001). A strong correlation between MELK and STMN1 expressions was observed (r = 0.741, p < 0.0001) in glioblastoma (GBM) samples. However, no difference on survival times was found when compared GBM cases with upregulated and downregulated STMN1 (Breslow = 0.092, median survival time: 11 and 13 months, respectively). Functional assays knocking down MELK by siRNA in GBM cell line showed that gene and protein expression of both MELK and stathmin were diminished. On the other hand, when the same analysis was performed for STMN1, only stathmin gene and protein was silenced.

Conclusions

The results presented herein point stahtmin as a downstream target in the MELK pathway that plays a role in malignant progression of astrocytomas.

Electronic supplementary material

The online version of this article (doi:10.1186/s12953-016-0094-9) contains supplementary material, which is available to authorized users.

Stathmin is enriched in the developing corticospinal tract

Understanding the intra- and extracellular proteins involved in the development of the corticospinal tract (CST) may offer insights into how the pathway could be regenerated following traumatic spinal cord injury. Currently, however, little is known about the proteome of the developing corticospinal system. The present study, therefore, has used quantitative proteomics and bioinformatics to detail the protein profile of the rat CST during its formation in the spinal cord. This analysis identified increased expression of 65 proteins during the early ingrowth of corticospinal axons into the spinal cord, and 36 proteins at the period of heightened CST growth. A majority of these proteins were involved in cellular assembly and organization, with annotations being most highly associated with cytoskeletal organization, microtubule dynamics, neurite outgrowth, and the formation, polymerization and quantity of microtubules. In addition, 22 proteins were more highly expressed within the developing CST in comparison to other developing white matter tracts of the spinal cord of age-matched animals. Of these differentially expressed proteins, only one, stathmin 1 (a protein known to be involved in microtubule dynamics), was both highly enriched in the developing CST and relatively sparse in other developing descending and ascending spinal tracts. Immunohistochemical analyses of the developing rat spinal cord and fetal human brain stem confirmed the enriched pattern of stathmin expression along the developing CST, and in vitro growth assays of rat corticospinal neurons showed a reduced length of neurite processes in response to pharmacological perturbation of stathmin activity. Combined, these findings suggest that stathmin activity may modulate axonal growth during development of the corticospinal projection, and reinforces the notion that microtubule dynamics could play an important role in the generation and regeneration of the CST.

Deceivingly dynamic: Learning-dependent changes in stathmin and microtubules

Microtubules, one of the major cytoskeletal structures, were previously considered stable and only indirectly involved in synaptic structure and function in mature neurons. However, recent evidence demonstrates that microtubules are dynamic and have an important role in synaptic structure, synaptic plasticity, and memory. In particular, learning induces changes in microtubule turnover and stability, and pharmacological manipulation of microtubule dynamics alters synaptic plasticity and long-term memory. These learning-induced changes in microtubules are controlled by the phosphoprotein stathmin, whose only known cellular activity is to negatively regulate microtubule formation. During the first eight hours following learning, changes in the phosphorylation of stathmin go through two phases causing biphasic shifts in microtubules stability/instability. These shifts, in turn, regulate memory formation by controlling in the second phase synaptic transport of the GluA2 subunit of AMPA receptors. Improper regulation of stathmin and microtubule dynamics has been observed in aged animals and in patients with Alzheimer's disease and depression. Thus, recent work on stathmin and microtubules has identified new molecular players in the early stages of memory encoding.

Stathmin 1 and p16(INK4A) are sensitive adjunct biomarkers for serous tubal intraepithelial carcinoma

OBJECTIVE

To credential Stathmin 1 (STMN1) and p16(INK4A) (p16) as adjunct markers for the diagnosis of serous tubal intraepithelial carcinoma (STIC), and to compare STMN1 and p16 expression in p53-positive and p53-negative STIC and invasive high-grade serous carcinoma (HGSC).

METHODS

Immunohistochemistry (IHC) was used to examine STMN1 and p16 expression in fallopian tube specimens (n=31) containing p53-positive and p53-negative STICs, invasive HGSCs, and morphologically normal FTE (fallopian tube epithelium). STMN1 and p16 expression was scored semiquantitatively by four individuals. The semiquantitative scores were dichotomized, and reported as positive or negative. Pooled siRNA was used to knockdown p53 in a panel of cell lines derived from immortalized FTE and HGSC.

RESULTS

STMN1 and p16 were expressed in the majority of p53-positive and p53-negative STICs and concomitant invasive HGSCs, but only scattered positive cells were present in morphologically normal FTE. Both proteins were expressed consistently across multiple STICs from the same patient and in concomitant invasive HGSC. Knockdown of p53 in immortalized FTE cells and in four HGSC-derived cell lines expressing different missense p53 mutations did not affect STMN1 protein levels.

CONCLUSIONS

This study demonstrates that STMN1 and p16 are sensitive and specific adjunct biomarkers that, when used with p53 and Ki-67, improve the diagnostic accuracy of STIC. The addition of STMN1 and p16 helps to compensate for practical limitations of p53 and Ki-67 that complicate the diagnosis in up to one third of STICs.

Anti-STMN1 therapy improves sensitivity to antimicrotubule drugs in esophageal squamous cell carcinoma

Stathmin (STMN1) regulates microtubule dynamics by promoting depolymerization of microtubules and/or preventing polymerization of tubulin heterodimers. Several studies have shown that overexpression of STMN1 has been linked to chemoresistance of paclitaxel and vinblastine in tumor cells. This study aimed to investigate the effects of STMN1 silencing on chemosensitivities of paclitaxel or vinblastine in esophageal squamous cell carcinoma (ESCC). Immunocytochemistry and immunofluorescence assays showed that STMN1 gene was highly expressed in Eca109 and TE-1 cells. We demonstrated that lentiviral-mediated STMN1 short hairpin RNA (shRNA) specifically and efficiently downregulated STMN1 expression in Eca109 and TE-1 cells. The sensitivity of STMN1-silencing shRNA-transfected Eca109 and TE-1 cells increased 191.4- and 179.3-fold to paclitaxel, and 21.3- and 28.4-fold to vincristine, respectively. Flow cytometry and mitotic index assays showed that knockdown of STMN1 in Eca109 and TE-1 cells led to cell cycle arrest in G2/M phase. After treatment with paclitaxel or vincristine, STMN1-silencing shRNA-transfected Eca109 and TE-1 cells were more likely to enter G2 but less likely to enter mitosis than control cells. Therefore, these data suggests that silencing STMN1 gene could increase sensitivity of ESCC to paclitaxel and vincristine through G2/M phase block.

Clinical significance of serum Stathmin in esophageal squamous cell carcinoma

AIM: To detect serum Stathmin in patients with esophageal squamous cell carcinoma (ESCC) and evaluate its correlation with clinicopathological parameters in ESCC.

METHODS: Serum levels of Stathmin were measured by enzyme-linked immunosorbent assay (ELISA) in 74 patients with ESCC and 81 healthy individuals. Serum levels of Cyfra21-1 were measured by ELISA, and those of CEA, CA19-9 and CA72-4 were measured by chemiluminescence.

RESULTS: Serum levels of Stathmin in ESCC patients were significantly higher than those in healthy controls (P < 0.001). Serum levels of Stathmin were correlated with lymph node metastasis (P = 0.036), but not with age, gender, tumor differentiation, TNM stage or tumor size. According to the ROC curve, the sensitivity and specificity of serum Stathmin were significantly higher than those of Cyfra21-1 for diagnosis of esophageal squamous cell carcinoma. The sensitivity of serum Stathmin for diagnosis of ESCC was 94.6%.

CONCLUSION: Serum Stathmin levels increase in ESCC patients. Detection of serum Stathmin is helpful for diagnosis and prognostic evaluation of esophageal cancer. Stathmin may serve as a new potential serum tumor marker for clinical detection, therapy and prognostic evaluation of ESCC.

Rlim, an E3 ubiquitin ligase, influences the stability of Stathmin protein in human osteosarcoma cells

Stathmin is an oncoprotein and is expressed at high levels in a wide variety of human malignancies, which plays important roles in maintenance of malignant phenotypes. The regulation of Stathmin gene overexpression has been wildly explored, but the exact mechanism still needs to be elucidated. It is believed that regulation of an oncogene protein abundance through post-translational modifications is essential for maintenance of malignant phenotypes. Here we identified the Rlim, a Ring H2 zinc finger protein with intrinsic ubiquitin ligase activity, as a Stathmin-interacting protein that could increase Stathmin turnover through binding with this targeted protein and then induce its degradation by proteasome in a ubiquitin-dependent manner. Inhibition of endogenous Rlim expression by siRNA could increase the level of Stathmin protein, which further led to cell proliferation and cell cycle changes in human osteosarcoma cell lines. On the other hand, forced overexpression of Rlim could decrease the level of Stathmin protein. These results demonstrate that Rlim is involved in the negative regulation of Stathmin protein level through physical interaction and ubiquitin-mediated proteolysis. Hence, Rlim is a novel regulator of Stathmin protein in a ubiquitin-dependent manner, and represents a new pathway for malignant phenotype turnover by modulating the level of Stathmin protein in human osteosarcomas.

FOXM1 mediates resistance to docetaxel in gastric cancer via up-regulating Stathmin

Docetaxel is commonly used as an effective chemotherapeutic drug for gastric cancer patients recently. With the increasing emergence of docetaxel resistance nowadays, identification of suitable biomarkers for predicting chemosensitivity to docetaxel may be a key role for improving therapeutic effects for gastric cancer patients. In this study, we investigated the correlation between the expression of transcription factor forkhead box protein M1 (FOXM1) and chemotherapy response to docetaxel in gastric cancer, the possible mechanism for which was further explored. As a result, FOXM1 overexpression was shown to mediate resistance to docetaxel in gastric cancers. It altered microtubule dynamics to protect tumour cells from docetaxel-induced apoptosis. Mechanistic investigations revealed that tubulin-destabilizing protein Stathmin, which mediated docetaxel resistance in FOXM1-silenced gastric cancer cells, is a direct down-stream target of FOXM1, whereas another microtubule dynamics protein mitotic centromere–associated kinesin (MCAK), shown to be related to docetaxel resistance in gastric cancer cells, is not associated with FOXM1 expression significantly. These results were further provided by immunohistochemical analysis, indicating that FOXM1 and Stathmin expression levels were correlated in 103 post-operational gastric cancer specimens. Moreover, when we attenuated FOXM1 expression with FOXM1 inhibitor thiostrepton, docetaxel resistance in gastric cancers was found to be reversed, simultaneously with the down-regulation of FOXM1 and Stathmin. Therefore, FOXM1 can be a useful marker for predicting and monitoring docetaxel response. Through the inhibition of FOXM1, docetaxel resistance can be reversed, and thus FOXM1 could be a new therapeutic target in docetaxel-resistant gastric cancer.

cAMP-dependent protein kinase and c-Jun N-terminal kinase mediate stathmin phosphorylation for the maintenance of interphase microtubules during osmotic stress

Dynamic microtubule changes after a cell stress challenge are required for cell survival and adaptation. Stathmin (STMN), a cytoplasmic microtubule-destabilizing phosphoprotein, regulates interphase microtubules during cell stress, but the signaling mechanisms involved are poorly defined. In this study ectopic expression of single alanine-substituted phospho-resistant mutants demonstrated that STMN Ser-38 and Ser-63 phosphorylation were specifically required to maintain interphase microtubules during hyperosmotic stress. STMN was phosphorylated on Ser-38 and Ser-63 in response to hyperosmolarity, heat shock, and arsenite treatment but rapidly dephosphorylated after oxidative stress treatment. Two-dimensional PAGE and Phos-tag gel analysis of stress-stimulated STMN phospho-isoforms revealed rapid STMN Ser-38 phosphorylation followed by subsequent Ser-25 and Ser-63 phosphorylation. Previously, we delineated stress-stimulated JNK targeting of STMN. Here, we identified cAMP-dependent protein kinase (PKA) signaling as responsible for stress-induced STMN Ser-63 phosphorylation. Increased cAMP levels induced by cholera toxin triggered potent STMN Ser-63 phosphorylation. Osmotic stress stimulated an increase in PKA activity and elevated STMN Ser-63 and CREB (cAMP-response element-binding protein) Ser-133 phosphorylation that was substantially attenuated by pretreatment with H-89, a PKA inhibitor. Interestingly, PKA activity and subsequent phosphorylation of STMN were augmented in the absence of JNK activation, indicating JNK and PKA pathway cross-talk during stress regulation of STMN. Taken together our study indicates that JNK- and PKA-mediated STMN Ser-38 and Ser-63 phosphorylation are required to preserve interphase microtubules in response to hyperosmotic stress.

Microtubule-associated proteins and tubulin interaction by isothermal titration calorimetry

Microtubules play an important role in a number of vital cell processes such as cell division, intracellular transport, and cell architecture. The highly dynamic structure of microtubules is tightly regulated by a number of stabilizing and destabilizing microtubule-associated proteins (MAPs), such as tau and stathmin. Because of their importance, tubulin-MAPs interactions have been extensively studied using various methods that provide researchers with complementary but sometimes contradictory thermodynamic data. Isothermal titration calorimetry (ITC) is the only direct thermodynamic method that enables a full thermodynamic characterization (stoichiometry, enthalpy, entropy of binding, and association constant) of the interaction after a single titration experiment. This method has been recently applied to study tubulin-MAPs interactions in order to bring new insights into molecular mechanisms of tubulin regulation. In this chapter, we review the technical specificity of this method and then focus on the use of ITC in the investigation of tubulin-MAPs binding. We describe technical issues which could arise during planning and carrying out the ITC experiments, in particular with fragile proteins such as tubulin. Using examples of stathmin and tau, we demonstrate how ITC can be used to gain major insights into tubulin-MAP interaction.

Relationship among expression of β-tubulin Ⅲ, Stathmin and P-gp proteins, response to paclitaxel chemotherapy, and prognosis in ESCC

AIM: To investigate the relationship among the expression of β-tubulin Ⅲ, Stathmin and P-gp proteins, and response to paclitaxel chemotherapy, and prognosis in esophageal squamous cell carcinoma (ESCC).

METHODS: Seventy-six ESCC patients were enrolled in this study and their tumor samples were collected for analysis. The expression of β-tubulin Ⅲ, Stathmin, and P-gp proteins in these ESCC samples and 40 normal esophageal mucosal samples was detected by immunohistochemistry. The correlation among the expression of these proteins, response to paclitaxel chemotherapy, and prognosis was then analyzed.

RESULTS: The positive rates of β-tubulin Ⅲ, Stathmin, and P-gp in ESCC were significantly higher than those in normal esophageal mucosal tissue (63.2% vs 10.0%, 54% vs 10%, 64.5% vs 20.0%, all P < 0.05). Increased expression of β-tubulin Ⅲ, Stathmin, and P-gp was significantly correlated with poor tumor differentiation, lymph node metastasis, and advanced tumor stage (all P < 0.05). In 64 cases treated by paclitaxel chemotherapy, the response rate was significantly lower in patients who had positive expression of β-tubulin Ⅲ, Stathmin, and P-gp than in those who had negative expression (P = 0.024, 0.024, 0.012).

CONCLUSION: The expression of β-tubulin Ⅲ, Stathmin, P-gp is increased in ESCC. Increased expression of β-tubulin Ⅲ, Stathmin, and P-gp is associated with high malignancy and poor prognosis.

Transactivation of the TIEG1 confers growth inhibition of transforming growth factor-β-susceptible hepatocellular carcinoma cells

AIM: To investigate the role of transforming growth factor (TGF)-β-inducible early gene 1 (TIEG1) in TGF-β-induced growth inhibition in hepatocellular carcinoma (HCC) cells.

METHODS: Human hepatocyte and HCC cell lines with varied susceptibilities to TGF-β1 were tested by methylthiazoletetrazolium (MTT) assay. The expression changes of Smad2, Smad3, Smad4, Smad7, TIEG1 and TIEG2 gene following treatment with TGF-β1 in a TGF-β-sensitive hepatocyte cell line (MIHA), a TGF-β-sensitive hepatoma cell line (Hep3B) and two TGF-β-insensitive hepatoma cell lines (HepG2 and Bel7404) were examined. SiRNA targeting TIEG1 was transfected into Hep3B cells and the sensitivity of cells to TGF-β1 was examined. Overexpression of TIEG1 was induced by lentiviral-mediated transduction in TGF-β1-resistant hepatoma cell lines (Bel7404 and HepG2). MTT assay and 4’,6-Diamidino-2-phenylindole staining were used to identify cell viability and apoptosis, respectively. The expression level of stathmin was measured by reverse transcriptase polymerase chain reaction and Western-blotting analysis, and stathmin promoter activity by TIEG1 was monitored by a luciferase reporter gene system.

RESULTS: TIEG1 was significantly upregulated by TGF-β1 in the TGF-β1-sensitive HCC cell line, Hep3B, but not in the resistant cell lines. The suppression of TIEG1 by siRNAs decreased the sensitivity of Hep3B cells to TGF-β1, whereas the overexpression of TIEG1 mediated growth inhibition and apoptosis in TGF-β1-resistant HCC cell lines, which resembled those of TGF-β1-sensitive HCC cells treated with TGF-β1. Our data further suggested that stathmin was a direct target of TIEG1, as stathmin was significantly downregulated by TIEG1 overexpression, and stathmin promoter activity was inhibited by TIEG1 in a dose-dependent manner.

CONCLUSION: Our data suggest that transactivation of TIEG1 conferred growth inhibition of TGF-β-susceptible human HCC cells.