Stathmin 1 deficiency induces erythro-megakaryocytic defects leading to macrocytic anemia and thrombocythemia in Stathmin 1 knock out mice.

Stathmin 1 (STMN1) is a cytosolic phosphoprotein that was discovered as a result of its high level of expression in leukemic cells. It plays an important role in the regulation of mitosis by promoting depolymerization of the microtubules that make up the mitotic spindle and, aging has been shown to impair STMN1 levels and change microtubule stability. We have previously demonstrated that a high level of STMN1 expression during early megakaryopoiesis is necessary for proliferation of megakaryocyte progenitors and that down-regulation of STMN1 expression during late megakaryopoiesis is important for megakaryocyte maturation and platelet production. In this report, we examined the effects of STMN1 deficiency on erythroid and megakaryocytic lineages in the mouse. Our studies show that STMN1 deficiency results in mild thrombocytopenia in young animals which converts into profound thrombocythemia as the mice age. STMN1 deficiency also lead to macrocytic changes in both erythrocytes and megakaryocytes that persisted throughout the life of STMN1 knock-out mice. Furthermore, STMN1 knock-out mice displayed a lower number of erythroid and megakaryocytic progenitor cells and had delayed recovery of their blood counts after chemotherapy. These studies show an important role for STMN1 in normal erythro-megakaryopoietic development and suggests potential implications for disorders affecting these hematopoietic lineages.

Stathmin/Op18 depletion induces genomic instability and leads to premature senescence in human normal fibroblasts.

Stathmin/oncoprotein18 regulates microtubule dynamics and participates in mitotic entry and exit. We isolated stathmin as a physically interacting partner of KIFC1, a minus-end-directed kinesin functioning in bipolar spindle formation and maintenance. We found that stathmin depletion leads to multipolar spindle formation in IMR-90 normal human fibroblasts. Stathmin-depleted IMR-90 cells showed early mitotic delay but managed to undergo chromosome segregation by forming multiple poles or pseudo-bipoles. Consistent with these observations, lagging chromosomes, and micronuclei were elevated in stathmin-depleted IMR-90 cells, demonstrating that stathmin is essential for maintaining genomic stability during mitosis in human cells. Genomic instability induced by stathmin depletion led to premature senescence without any indication of cell death in normal IMR-90 cells. Double knock-down of both stathmin and p53 also did not induce cell death in IMR-90 cells, while the stathmin knock-down triggered apoptosis in p53-proficient human lung adenocarcinoma cells. Our results suggest that stathmin is essential in bipolar spindle formation to maintain genomic stability during mitosis, and the depletion of stathmin prevents the initiation of chromosome instability by inducing senescence in human normal fibroblasts.

High expression of karyopherin-α2 and stathmin 1 is associated with proliferation potency and transformation in the bile duct and gall bladder epithelia in the cases of pancreaticobiliary maljunction.

BACKGROUNDS AND OBJECTIVES: Pancreaticobiliary maljunction (PBM) may be associated with an increased frequency of gall bladder cancer with no bile duct dilation. Karyopherin-α2 (KPNA2) and stathmin 1 (STMN1) were reported to play important roles in carcinogenesis and cancer progression. METHODS: Fifteen patients with PBM who underwent surgical resection between 1999 and 2014 were included in this study. Using immunohistochemistry, we investigated the expression of p53, Ki-67, KPNA2, and STMN1 in normal biliary tract epithelium, hyperplastic epithelium, and cholangiocarcinoma (CC) tissues. RESULTS: Nuclear expression of KPNA2, p53, and Ki-67 expression was detected in hyperplastic epithelium and CC tissues. High KPNA2 expression was significantly associated with gender (P = 0.04), p53 nuclear accumulation (P = 0.00435), and Ki-67 expression (P = 0.0443) in the gall bladder and bile duct of PBM. On the other hand, STMN1 was only expressed in CC tissues and was not observed in normal bile duct and hyperplastic epithelia. CONCLUSIONS: KPNA2 might be a useful marker of hyperplasia, dysplasia, and carcinogenicity in patients with PBM. STMN1 evaluation might be a cancer-specific marker for CC patients with PBM similar as that for other cancers. J. Surg. Oncol. 2016;114:462-468. © 2016 Wiley Periodicals, Inc.

Regulation of Oncoprotein 18/Stathmin Signaling by ERK Concerns the Resistance to Taxol in Nonsmall Cell Lung Cancer Cells.

Taxol is a cytotoxic antiepithelioma chemotherapy drug widely used clinically, which results in appearing a broad range of taxol-resistant tumors. Oncoprotein 18 (Op18)/stathmin is a genetically highly conserved small-molecule cytosolic phosphoprotein and highly expressed in tumors. Extracellular signal-regulated kinase (ERK) is a main member of mitogen-activated protein kinases (MAPKs). The study demonstrated that combination of blockage of ERK signal by ERK inhibitor PD98059 and Taxol greatly promoted taxol-induced cellular apoptosis and growth inhibition, decreased the expression of Op18/stathmin and total levels of phosphor-Op18/stathmin, while weakened the cyclin-dependent kinase 2 (cdc2) activity and antiapoptotic protein Bcl-2 expression and inhibited IL-10 autocrine in taxol-resistant NCI-H1299 cells; Taxol-resistant NCI-H1299 cells expressed high levels of ERK and phosphor-ERK in contrast to taxol-sensitive CNE1 cells, and ERK mainly phosphorylated Op18/stathmin at Ser 25 site. These findings suggest that ERK-mediated Op18/stathmin is involved in taxol resistance of tumors; blockage of ERK signal improves the sensitivity of tumor cells to taxol, which provides new clues for treating taxol-resistant carcinomas.

Overexpression of SCLIP promotes growth and motility in glioblastoma cells.

SCLIP, a microtubule-destabilizing phosphoprotein, is known to be involved in the development of the central nervous system (CNS). It has been well established that there are notable parallels between normal development and tumorigenesis, especially in glioma. However, no studies have examined the significance of SCLIP in gliomagenesis. To address this, we investigated the expression of SCLIP and its roles in the development of gliomas. Notably, we found that SCLIP was highly expressed in various grades of glioma samples, as compared with normal brain tissues. Overexpression of SCLIP dramatically stimulated tumor cell migration and invasion as well as proliferation and downregulation of SCLIP showed opposite effects, establishing an important oncogenic role for this gene. Furthermore, we revealed that STAT3 was required to maintain SCLIP stability, suggesting that overexpression of STAT3 may be a critical step to facilitate microtubule dynamics and subsequently promotes migration and invasion of glioma cells. Taken together, our findings demonstrate that SCLIP plays an important role in glioma pathology, and may represent a novel therapeutic strategy against human glioma.

Op18/stathmin is involved in the resistance of taxol among different epithelial carcinoma cell lines.

PURPOSE: Taxol is an effective chemotherapeutic agent against epithelial-derived carcinomas, and resistance of carcinoma cells to taxol has developed with the wide prescription of the drug. In this study, five different epithelial carcinoma cell lines were randomly employed to screen the resistant cell line to taxol, and to explore the probable mechanism of taxol-resistant development. MATERIALS AND METHODS: Cells were grouped into the controls and the taxol treated. The treatment effects of five different epithelial carcinoma cell lines, including CNE1, Hep3B-2, MGC, MCF-7, and NCI-H1299, after being treated by taxol were analyzed through inspecting the ratios of cellular apoptosis, inhibition of cellular proliferation, the capability of cell colony formation and wound recovery, and the interference of cell motility and invasion, while western blot analysis and siRNA targeting Op18/stathmin were applied to explore the probable mechanism on the taxol resistance difference in these cells. RESULTS: Nonsmall cell lung cancer NCI-H1299 cells presented obvious taxol resistance, and the inhibition of cell motility and invasion was also the weakest in taxol-treated NCI-H1299 cells among these five cell lines. Microtubule dynamics analysis demonstrated that taxol treatment destroyed normal microtubule arrays and caused obvious microtubule collapse in CNE1, Hep3B-2, MGC, and MCF-7 rather than NCI-H1299, while the latter expressed high levels of microtubule-destabilizing protein Op18/stathmin. Inhibition of Op18/stathmin expression increased the sensitivity to taxol and promoted cellular apoptosis in NCI-H1299 cells. CONCLUSION: NCI-H1299 cells are evidently resistant to taxol-induced cellular apoptosis, inhibition of cellular proliferation and wound recovery, as well as cell migration and invasion interference, which are closely associated with the changes of microtubule dynamics. High expression of Op18/stathmin is perhaps a crucial determinant of taxol-resistant development in NCI-H1299 cells.

Stathmin 1 is involved in the highly proliferative phenotype of high-risk myelodysplastic syndromes and acute leukemia cells.

Stathmin 1 is an important cytoplasmic microtubule-destabilizing protein that plays critical roles in proliferation and accurate chromosome segregation through regulation of microtubule dynamics. High levels of Stathmin 1 expression have been reported in leukemia and solid tumors. However, Stathmin 1 has not been studied in myelodysplastic syndrome cells. We, herein, report that significantly higher Stathmin 1 levels were observed in proliferating hematopoietic cells, in high-risk MDS and acute leukemia cells. In addition, Stathmin 1 silencing in U937 and Namalwa leukemia cells reduced cell proliferation and clonogenicity. Our data suggest that Stathmin 1 expression may be related to the highly proliferative phenotype of hematopoietic cells and add new insights into the participation of Stathmin 1 in hematological malignancies.