High STMN1 Expression is Associated with Cancer Progression and Chemo-Resistance in Lung Squamous Cell Carcinoma.

BACKGROUND: Known as a microtubule-destabilizing protein, STMN1 (gene symbol: STMN1) regulates the dynamics of microtubules, cell cycle progress, and chemo-resistance against taxane agents. It is highly expressed in various human cancers and involved in cancer progression as well as poor prognosis. METHODS: Expression of STMN1 was examined by immunohistochemistry using FFPE tissue sections from 186 patients with lung squamous cell carcinoma (LSCC). Analysis of STMN1 suppression was performed for STMN1 small interfering RNA (siRNA)-transfected LSCC cell lines to determine the change in proliferation, invasive and apoptosis abilities, and paclitaxel sensitivity. RESULTS: The cytoplasmic STMN1 expression in LSCC was higher than in normal tissues. The high expression was significantly associated with vascular invasion (P = 0.0477) and poor prognosis. In addition, the proliferating and invasive abilities were decreased, and the apoptosis ability and paclitaxel sensitivity were increased in STMN1-suppressed LSCC cells compared with control cells. CONCLUSION: The results suggest that STMN1 is a prognostic factor that also is associated with caner progression and chemo-resistance. Therefore, STMN1 could be a predictor for poor prognosis and a potential therapeutic target in LSCC.

ANKHD1 silencing inhibits Stathmin 1 activity, cell proliferation and migration of leukemia cells.

ANKHD1 is highly expressed in human acute leukemia cells and potentially regulates multiple cellular functions through its ankyrin-repeat domains. In order to identify interaction partners of the ANKHD1 protein and its role in leukemia cells, we performed a yeast two-hybrid system screen and identified SIVA, a cellular protein known to be involved in proapoptotic signaling pathways. The interaction between ANKHD1 and SIVA was confirmed by co-imunoprecipitation assays. Using human leukemia cell models and lentivirus-mediated shRNA approaches, we showed that ANKHD1 and SIVA proteins have opposing effects. While it is known that SIVA silencing promotes Stathmin 1 activation, increased cell migration and xenograft tumor growth, we showed that ANKHD1 silencing leads to Stathmin 1 inactivation, reduced cell migration and xenograft tumor growth, likely through the inhibition of SIVA/Stathmin 1 association. In addition, we observed that ANKHD1 knockdown decreases cell proliferation, without modulating apoptosis of leukemia cells, while SIVA has a proapoptotic function in U937 cells, but does not modulate proliferation in vitro. Results indicate that ANKHD1 binds to SIVA and has an important role in inducing leukemia cell proliferation and migration via the Stathmin 1 pathway. ANKHD1 may be an oncogene and participate in the leukemia cell phenotype.

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.

MicroRNA-9 inhibits vasculogenic mimicry of glioma cell lines by suppressing Stathmin expression.

The purpose of this study was to investigate the functions of microRNA-9, which is a tissue-specific microRNA in central nervous system, in the vasculogenic mimicry (VM) of glioma cell lines in vitro and in vivo. Glioma cell lines U87MG, U251 and SHG44 were transfected with microRNA-9 mimic, microRNA-9 inhibitor or scramble sequences. The amount of microRNA-9 and Stathmin (STMN1) mRNA was determined by quantitative real-time PCR, and the protein expression of STMN1 was determined by western blot. Cell proliferation and apoptosis were assessed. The interactions between the 3'UTR of STMN1 and miR-9 was determined by luciferase reporter assay. The VM capacity in vitro was evaluated using VM formation assay, and the rescue experiment of STMN1 was carried out in U251 cells. The in vivo experiment was applied with animal models implanted with U87MG cells.MicroRNA-9 mimic transfection reduced proliferation and increased apoptosis in glioma cell lines (p < 0.05). MicroRNA-9 mimic up-regulated STMN1 mRNA levels but reduced its protein levels (p < 0.05), and luciferase activity of STMN1 was suppressed by microRNA-9 mimic transfection (p < 0.05). Furthermore, microRNA-9 mimic transfection suppressed tumor volume growth, as well as VM both in vitro and in vivo. The cell viability and microtube density were upregulated in U251 cells after STMN1 up-regulation (p < 0.05). STMN1 is a target of microRNA-9, and microRNA-9 could modulate cell proliferation, VM and tumor volume growth through controlling STMN1 expression. MicroRNA-9 and its targets may represent a novel panel of molecules for the development of glioma treatment.

Phosphorylation at Ser10 triggered p27 degradation and promoted gallbladder carcinoma cell migration and invasion by regulating stathmin1 under glucose deficiency.

Gallbladder carcinoma (GBC) is a considerable challenge because of its high metastatic potential. The tumor microenvironment is characterized by nutrient starvation, which promotes tumor metastasis. Stathmin1, an important microtubuleregulating protein, is overexpressed and promotes metastasis in GBC. It remains unclear how the harsh tumor microenvironment regulates stathmin1 expression to affect GBC metastasis. We employed glucose deficiency to mimic nutrient starvation and found that glucose deficiency upregulated stathmin1 transcription. However, glucose deficiency also promoted p27 degradation. There was a significant negative correlation between stathmin1 and p27 protein levels under glucose deficiency. Further study revealed that, under glucose deficiency, human kinase interacting with stathmin (hKIS) induced phosphorylation at Ser10 of p27 and its translocation to the cytoplasm for degradation, which upregulated the transcription factor E2F1 to promote stathmin1 transcription. hKIS knockdown significantly inhibited p27 cytoplasmic translocation and its consequent degradation. Stathmin1 knockdown significantly inhibited GBC cell migration and invasion in vitro. Our study revealed the role of the hKIS/p27/E2F1 axis in upregulating stathmin1 transcription to promote GBC cell migration and invasion under glucose deficiency conditions.

Involvement of stathmin 1 in the neurotrophic effects of PACAP in PC12 cells.

Rat pheochromocytoma PC12 cells have been widely used to investigate the neurotrophic activities of pituitary adenylate cyclase-activating polypeptide (PACAP). In particular, PACAP has been shown to promote differentiation and to inhibit apoptosis of PC12 cells. In order to identify the mechanisms mediating these effects, we sought for proteins that are phosphorylated upon PACAP treatment. High-performance liquid chromatography and 2D gel electrophoresis analysis, coupled with mass spectrometry, revealed that stathmin 1 is strongly phosphorylated within only 5 min of exposure to PACAP. Western blot experiments confirmed that PACAP induced a robust phosphorylation of stathmin 1 in a time-dependent manner. On the other hand, PACAP decreased stathmin 1 gene expression. Investigations of the signaling mechanisms known to be activated by PACAP revealed that phosphorylation of stathmin 1 was mainly mediated through the protein kinase A and mitogen-activated protein kinase pathways. Blockage of stathmin 1 expression with small interfering RNA did not affect PC12 cell differentiation induced by PACAP but reduced the ability of the peptide to inhibit caspase 3 activity and significantly decreased its neuroprotective action. Taken together, these data demonstrate that stathmin 1 is involved in the neurotrophic effect of PACAP in PC12 cells.

Overexpression of stathmin1 in the diffuse type of gastric cancer and its roles in proliferation and migration of gastric cancer cells.

BACKGROUND: Stathmin1 is a microtubule-regulating protein that has an important role in the assembly and disassembly of the mitotic spindle. The roles of stathmin1 in carcinogenesis of various cancers, including prostate and breast cancer, have been explored. However, its expression and roles in gastric cancer have not yet been described. METHODS: Stathmin1 expression in paraffin-embedded tissue sections from 226 patients was analysed by immunohistochemistry. Roles of stathmin1 were studied using a specific small interfering RNA (siRNA). RESULTS: The expression of stathmin1 was positively correlated with lymph node metastasis, TNM stages and vascular invasion, and negatively with recurrence-free survival, in the diffuse type of gastric cancer. The median recurrence-free survival in patients with a negative and positive expression of stathmin1 was 17.0 and 7.0 months, respectively (P=0.009). When the expression of stathmin1 was knocked down using siRNA, the proliferation, migration and invasion of poorly differentiated gastric cancer cells in vitro were significantly inhibited. Moreover, stathmin1 siRNA transfection significantly slowed the growth of xenografts in nude mice. CONCLUSION: These results suggest that stathmin1 can be a good prognostic factor for recurrence-free survival rate and is a therapeutic target in diffuse-type gastric cancer.

Interphase-specific phosphorylation-mediated regulation of tubulin dimer partitioning in human cells.

The microtubule cytoskeleton is differentially regulated by a diverse array of proteins during interphase and mitosis. Op18/stathmin (Op18) and microtubule-associated protein (MAP)4 have been ascribed opposite general microtubule-directed activities, namely, microtubule destabilization and stabilization, respectively, both of which can be inhibited by phosphorylation. Here, using three human cell models, we depleted cells of Op18 and/or MAP4 by expression of interfering hairpin RNAs and we analyzed the resulting phenotypes. We found that the endogenous levels of Op18 and MAP4 have opposite and counteractive activities that largely govern the partitioning of tubulin dimers in the microtubule array at interphase. Op18 and MAP4 were also found to be the downstream targets of Ca(2+)- and calmodulin-dependent protein kinase IV and PAR-1/MARK2 kinase, respectively, that control the demonstrated counteractive phosphorylation-mediated regulation of tubulin dimer partitioning. Furthermore, to address mechanisms regulating microtubule polymerization in response to cell signals, we developed a system for inducible gene product replacement. This approach revealed that site-specific phosphorylation of Op18 is both necessary and sufficient for polymerization of microtubules in response to the multifaceted signaling event of stimulation of the T cell antigen receptor complex, which activates several signal transduction pathways.

Stathmin-2 Mediates Glucagon Secretion From Pancreatic α-Cells.

Inhibition of glucagon hypersecretion from pancreatic α-cells is an appealing strategy for the treatment of diabetes. Our hypothesis is that proteins that associate with glucagon within alpha cell secretory granules will regulate glucagon secretion, and may provide druggable targets for controlling abnormal glucagon secretion in diabetes. Recently, we identified a dynamic glucagon interactome within the secretory granules of the α cell line, αTC1-6, and showed that select proteins within the interactome could modulate glucagon secretion. In the present study, we show that one of these interactome proteins, the neuronal protein stathmin-2, is expressed in αTC1-6 cells and in mouse pancreatic alpha cells, and is a novel regulator of glucagon secretion. The secretion of both glucagon and Stmn2 was significantly enhanced in response to 55 mM K+, and immunofluorescence confocal microscopy showed co-localization of stathmin-2 with glucagon and the secretory granule markers chromogranin A and VAMP-2 in αTC1-6 cells. In mouse pancreatic islets, Stathmin-2 co-localized with glucagon, but not with insulin, and co-localized with secretory pathway markers. To show a function for stathmin-2 in regulating glucagon secretion, we showed that siRNA-mediated depletion of stathmin-2 in αTC1-6 cells caused glucagon secretion to become constitutive without any effect on proglucagon mRNA levels, while overexpression of stathmin-2 completely abolished both basal and K+-stimulated glucagon secretion. Overexpression of stathmin-2 increased the localization of glucagon into the endosomal-lysosomal compartment, while depletion of stathmin-2 reduced the endosomal localization of glucagon. Therefore, we describe stathmin-2 as having a novel role as an alpha cell secretory granule protein that modulates glucagon secretion via trafficking through the endosomal-lysosomal system. These findings describe a potential new pathway for the regulation of glucagon secretion, and may have implications for controlling glucagon hypersecretion in diabetes.

Oncoprotein 18 is necessary for malignant cell proliferation in bladder cancer cells and serves as a G3-specific non-invasive diagnostic marker candidate in urinary RNA.

BACKGROUND: Urine-based diagnostics indicated involvement of oncoprotein 18 (OP18) in bladder cancer. In cell culture models we investigated the role of OP18 for malignant cell growth. METHODS: We analyzed 113 urine samples and investigated two human BCa cell lines as a dual model: RT-4 and ECV-304, which represented differentiated (G1) and poorly differentiated (G3) BCa. We designed specific siRNA for down-regulation of OP18 in both cell lines. Phenotypes were characterized by cell viability, proliferation, and expression of apoptosis-related genes. Besides, sensitivity to cisplatin treatment was evaluated. RESULTS: Analysis of urine samples from patients with urothelial BCa revealed a significant correlation of the RNA-ratio OP18:uroplakin 1A with bladder cancer. High urinary ratios were mainly found in moderately to poorly differentiated tumors (grade G2-3) that were muscle invasive (stage T2-3), whereas samples from patients with more differentiated non-invasive BCa (G1) showed low OP18:UPK1A RNA ratios. Down-regulation of OP18 expression in ECV-304 shifted its phenotype towards G1 state. Further, OP18-directed siRNA induced apoptosis and increased chemo-sensitivity to cisplatin. CONCLUSIONS: This study provides conclusive experimental evidence for the link between OP18-derived RNA as a diagnostic marker for molecular staging of BCa in non-invasive urine-based diagnostics and the patho-mechanistic role of OP18 suggesting this gene as a therapeutic target.

Aneugenic activity of Op18/stathmin is potentiated by the somatic Q18-->e mutation in leukemic cells.

Op18/stathmin (Op18) is a phosphorylation-regulated microtubule destabilizer that is frequently overexpressed in tumors. The importance of Op18 in malignancy was recently suggested by identification of a somatic Q18-->E mutation of Op18 in an adenocarcinoma. We addressed the functional consequences of aberrant Op18 expression in leukemias by analyzing the cell cycle of K562 cells either depleted of Op18 by expression of interfering hairpin RNA or induced to express wild-type or Q18E substituted Op18. We show here that although Op18 depletion increases microtubule density during interphase, the density of mitotic spindles is essentially unaltered and cells divide normally. This is consistent with phosphorylation-inactivation of Op18 during mitosis. Overexpression of wild-type Op18 results in aneugenic activities, manifest as aberrant mitosis, polyploidization, and chromosome loss. One particularly significant finding was that the aneugenic activity of Op18 was dramatically increased by the Q18-->E mutation. The hyperactivity of mutant Op18 is apparent in its unphosphorylated state, and this mutation also suppresses phosphorylation-inactivation of the microtubule-destabilizing activity of Op18 without any apparent effect on its phosphorylation status. Thus, although Op18 is dispensable for mitosis, the hyperactive Q18-->E mutant, or overexpressed wild-type Op18, exerts aneugenic effects that are likely to contribute to chromosomal instability in tumors.

Silencing of stathmin induces tumor-suppressor function in breast cancer cell lines harboring mutant p53.

Cancers harboring dominant-negative p53 mutations are often aggressive and difficult to treat. Direct attempts to restore wild-type p53 function have produced little clinical benefit. We investigated whether targeting a p53-target gene could induce certain tumor-suppressor characteristics. We found that inhibition of stathmin, a microtubule regulator that can be transcriptionally repressed by wild-type p53, restored certain wild-type functions to cancer cells with mutant p53. Silencing of stathmin by small interfering RNA (siRNA) in mutant p53 cell lines lowered expression to that observed following activation of wild-type p53 by DNA damage in wild-type p53 cell lines. siRNA-induced repression of stathmin decreased cell proliferation, viability and clonogenicity in mutant p53 cell lines. Furthermore, knockdown of stathmin partially restored cell-cycle regulation and activation of apoptosis. Therefore, targeting stathmin, a gene product that is overexpressed in the presence of mutant p53, may represent a novel approach to treating cancers with aberrant p53 function.

Synergistic antiangiogenic effects of stathmin inhibition and taxol exposure.

Stathmin is one of the key regulators of the microtubule cytoskeleton and the mitotic spindle in eukaryotic cells. It is expressed at high levels in a wide variety of human cancers and may provide an attractive target for cancer therapy. We had previously shown that stathmin inhibition results in the abrogation of the malignant phenotype. The microtubule-interfering drug, taxol, has both antitumorigenic and antiangiogenic properties. We had also shown that the antitumor activities of taxol and stathmin inhibition are synergistic. We hypothesized that taxol and stathmin inhibition may also have synergistic antiangiogenic activities. A replication-deficient bicistronic adenoviral vector that coexpresses green fluorescent protein and an anti-stathmin ribozyme was used to target stathmin mRNA. Exposure of endothelial cells to anti-stathmin adenovirus alone resulted in a dose-dependent inhibition of proliferation, migration, and differentiation into capillary-like structures. This inhibition was markedly enhanced by exposure of transduced endothelial cells to very low concentrations of taxol, which resulted in a virtually complete loss of proliferation, migration, and differentiation of endothelial cells. In contrast, exposure of nontransduced endothelial cells to taxol alone resulted in a modest inhibition of proliferation, migration, and differentiation. Our detailed analysis showed that the antiangiogenic effects of the combination of stathmin inhibition and taxol exposure are synergistic. Our studies also showed that the mechanism of this synergistic interaction is likely to be mediated through the stabilization of microtubules. Thus, this novel combination may provide an attractive therapeutic strategy that combines a synergistic antitumor activity with a synergistic antiangiogenic activity.

Therapeutic interactions between stathmin inhibition and chemotherapeutic agents in prostate cancer.

Limitations of prostate cancer therapy may be overcome by combinations of chemotherapeutic agents with gene therapy directed against specific proteins critical for disease progression. Stathmin is overexpressed in many types of human cancer, including prostate cancer. Stathmin is one of the key regulators of the microtubule network and the mitotic spindle and provides an attractive therapeutic target in cancer therapy. We recently showed that adenovirus-mediated gene transfer of anti-stathmin ribozyme could suppress the malignant phenotype of prostate cancer cells in vitro. In the current studies, we asked whether the therapeutic effects of stathmin inhibition could be further enhanced by exposure to different chemotherapeutic agents. Exposure of uninfected LNCaP human prostate cancer cells or cells infected with a control adenovirus to Taxol, etoposide, 5-fluorouracil (5-FU), or Adriamycin resulted in modest decrease in proliferation and clonogenicity. Interestingly, exposure of cells infected with an anti-stathmin adenovirus to Taxol or etoposide resulted in a complete loss of proliferation and clonogenicity, whereas exposure of the same cells to 5-FU or Adriamycin potentiated the growth-inhibitory effects of the anti-stathmin ribozyme, but the cells continued to proliferate. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling analysis of uninfected cells or cells infected with a control adenovirus showed modest induction of apoptosis in the presence of different drugs. In contrast, cells infected with the anti-stathmin adenovirus showed a marked increase in apoptosis on exposure to Taxol or etoposide and a modest increase on exposure to 5-FU or Adriamycin. Overall, the effects of combinations of anti-stathmin ribozyme with Taxol or etoposide were synergistic, whereas the effects of combinations of anti-stathmin ribozyme with 5-FU or Adriamycin were additive. Moreover, triple combination of anti-stathmin ribozyme with low noninhibitory concentrations of Taxol and etoposide resulted in a profound synergistic inhibition of proliferation, clonogenicity, and marked induction of apoptosis. This synergy might be very relevant for the treatment of prostate cancer because Taxol and etoposide are two of the most effective agents in this disease. Thus, this combination may provide a novel form of prostate cancer therapy that would avoid toxicities associated with the use of multiple chemotherapeutic agents at full therapeutic doses.

Stathmin mediates neuroblastoma metastasis in a tubulin-independent manner via RhoA/ROCK signaling and enhanced transendothelial migration.

Neuroblastoma, the most common solid tumor of young children, frequently presents with aggressive metastatic disease and for these children the 5-year survival rates are dismal. Metastasis, the movement of cancer cells from one site to another, involves remodeling of the cytoskeleton including altered microtubule dynamics. The microtubule-destabilizing protein, stathmin, has recently been shown to mediate neuroblastoma metastasis although precise functions remain poorly defined. In this study we investigated stathmin's contribution to the metastatic process and potential mechanism(s) by which it exerts these effects. Stathmin suppression significantly reduced neuroblastoma cell invasion of 3D tumor spheroids into an extracellular matrix. Moreover, inhibiting stathmin expression significantly reduced transendothelial migration in two different neuroblastoma cell lines in vitro. Inhibition of ROCK, a key regulator of cell migration, in neuroblastoma cells highlighted that stathmin regulates transendothelial migration through ROCK signaling. Reduced stathmin expression in neuroblastoma cells significantly increased the activation of the RhoA small GTPase. Notably, re-expression of either wild type or a phospho-mimetic stathmin mutant (4E) made defective in tubulin binding returned cell migration and transendothelial migration back to control levels, indicating that stathmin may influence these processes in neuroblastoma cells independent of tubulin binding. Finally, stathmin suppression in neuroblastoma cells significantly reduced whole body, lung, kidney and liver metastases in an experimental metastases mouse model. In conclusion, stathmin suppression interferes with the metastatic process via RhoA/ROCK signaling in neuroblastoma cells. These findings highlight the importance of stathmin to the metastatic process and its potential as a therapeutic target for the treatment of neuroblastoma.

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.

Preclinical Biodistribution and Safety Evaluation of a pbi-shRNA STMN1 Lipoplex after Subcutaneous Delivery.

Stathmin-1 (STMN1) is a microtubule-destabilizing protein which is overexpressed in cancer. Its overexpression is associated with poor prognosis and also serves as a predictive marker to taxane therapy. We have developed a proprietary bi-functional shRNA (bi-shRNA) platform to execute RNA interference (RNAi)-mediated gene silencing and a liposome-carrier complex to systemically deliver the pbi-shRNA plasmids. In vitro and in vivo testing demonstrated efficacy and specificity of pbi-shRNA plasmid in targeting STMN1 (Phadke, A. P., Jay, C. M., Wang, Z., Chen, S., Liu, S., Haddock, C., Kumar, P., Pappen, B. O., Rao, D. D., Templeton, N. S., et al. (2011). In vivo safety and antitumor efficacy of bifunctional small hairpin RNAs specific for the human Stathmin 1 oncoprotein. DNA Cell Biol. 30, 715-726.). Biodistribution and toxicology studies in bio-relevant Sprague Dawley rats with pbi-shRNA STMN1 lipoplex revealed that the plasmid DNA was delivered to a broad distribution of organs after a single subcutaneous injection. Specifically, plasmid was detected within the first week using QPCR (threshold 50 copies plasmid/1 µg genomic DNA) at the injection site, lung, spleen, blood, skin, ovary (limited), lymph nodes, and liver. It was not detected in the heart, testis or bone marrow. No plasmid was detected from any organ 30 days after injection. Treatment was well tolerated. Minimal inflammation/erythema was observed at the injection site. Circulating cytokine response was also examined by ELISA. The IL-6 levels were induced within 6 h then declined to the vehicle control level 72 h after the injection. TNFα induction was transiently observed 4 days after the DNA lipoplex treatment. In summary, the pbi-shRNA STMN1 lipoplex was well tolerated and displayed broad distribution after a single subcutaneous injection. The pre-clinical data has been filed to FDA and the pbi-shRNA STMN1 lipoplex is being investigated in a phase I clinical study.

Silencing Op18/stathmin by RNA Interference Promotes the Sensitivity of Nasopharyngeal Carcinoma Cells to Taxol and High-Grade Differentiation of Xenografted Tumours in Nude Mice.

Nasopharyngeal carcinoma (NPC) is a refractory tumour, and chemotherapy is one of the primary treatment modalities. Oncoprotein 18 (Op18)/stathmin is a conserved small cytosolic phosphoprotein and highly expressed in tumours, which plays a vital role in maintaining the malignant phenotype of tumours. Taxol is a clinically widely used chemotherapeutic agent for a broad range of taxol-resistant tumours. This study showed that Op18/stathmin silencing by RNA interference (RNAi) combined taxol cooperatively improved cellular apoptosis in CNE1 cells mainly via initiating endogenous death receptor pathway, impaired the capabilities of cellular proliferation and cellular migration and down-regulated the half maximal inhibitory concentration (IC50 ) of taxol, meanwhile decreased the expression of the upstream extracellular regulated kinase 1 (ERK1) in vitro. Evidence also showed that taxol cytotoxicity was markedly augmented for Op18/stathmin RNAi in other NPC cells. In vivo animal experiments have demonstrated that early combination of Op18/stathmin silencing and taxol evidently inhibited tumourigenicity of CNE1 cells and growth of xenografted tumours in nude mice. Remarkably, silencing Op18/stathmin by RNAi still promoted transformation of late-stage CNE1 cells in NPC-xenografted tumours from moderately to highly differentiated and inhibited the pleiotropic cytokine interleukin-10 (IL-10) autocrine by transplanted tumours. These findings suggest that silencing Op18/stathmin by RNAi promotes chemosensitization of NPC to taxol and reverses malignant phenotypes of NPC, which provides a new clue for treating drug-resistant tumours.

Stathmin 1 in normal and malignant hematopoiesis.

Stathmin 1 is a microtubule destabilizer that plays an important role in cell cycle progression, segregation of chromosomes, clonogenicity, cell motility and survival. Stathmin 1 overexpression has been reported in malignant hematopoietic cells and Stathmin 1 inhibition reduces the highly proliferative potential of leukemia cell lines. However, during the differentiation of primary hematopoietic cells, Stathmin 1 expression decreases in parallel to decreases in the proliferative potential of early hematopoietic progenitors. The scope of the present review is to survey the current knowledge and highlight future perspectives for Stathmin 1 in normal and malignant hematopoiesis, with regard to the expression, function and clinical implications of this protein.