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| 2. |
- Ehlén, Åsa, et al.
(författare)
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Expression of the RNA-binding protein RBM3 is associated with a favourable prognosis and cisplatin sensitivity in epithelial ovarian cancer
- 2010
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Ingår i: Journal of Translational Medicine. - : Springer Science and Business Media LLC. - 1479-5876 .- 1479-5876. ; 8, s. 78-
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Tidskriftsartikel (refereegranskat)abstract
- Background: We recently demonstrated that increased expression of the RNA-binding protein RBM3 is associated with a favourable prognosis in breast cancer. The aim of this study was to examine the prognostic value of RBM3 mRNA and protein expression in epithelial ovarian cancer (EOC) and the cisplatin response upon RBM3 depletion in a cisplatin-sensitive ovarian cancer cell line. Methods: RBM3 mRNA expression was analysed in tumors from a cohort of 267 EOC cases (Cohort I) and RBM3 protein expression was analysed using immunohistochemistry (IHC) in an independent cohort of 154 prospectively collected EOC cases (Cohort II). Kaplan Meier analysis and Cox proportional hazards modelling were applied to assess the relationship between RBM3 and recurrence free survival (RFS) and overall survival (OS). Immunoblotting and IHC were used to examine the expression of RBM3 in a cisplatin-resistant ovarian cancer cell line A2780-Cp70 and its cisplatin-responsive parental cell line A2780. The impact of RBM3 on cisplatin response in EOC was assessed using siRNA-mediated silencing of RBM3 in A2780 cells followed by cell viability assay and cell cycle analysis. Results: Increased RBM3 mRNA expression was associated with a prolonged RFS (HR = 0.64, 95% CI = 0.47-0.86, p = 0.003) and OS (HR = 0.64, 95% CI = 0.44-0.95, p = 0.024) in Cohort I. Multivariate analysis confirmed that RBM3 mRNA expression was an independent predictor of a prolonged RFS, (HR = 0.61, 95% CI = 0.44-0.84, p = 0.003) and OS (HR = 0.62, 95% CI = 0.41-0.95; p = 0.028) in Cohort I. In Cohort II, RBM3 protein expression was associated with a prolonged OS (HR = 0.53, 95% CI = 0.35-0.79, p = 0.002) confirmed by multivariate analysis (HR = 0.61, 95% CI = 0.40-0.92, p = 0.017). RBM3 mRNA and protein expression levels were significantly higher in the cisplatin sensitive A2780 cell line compared to the cisplatin resistant A2780-Cp70 derivative. siRNA-mediated silencing of RBM3 expression in the A2780 cells resulted in a decreased sensitivity to cisplatin as demonstrated by increased cell viability and reduced proportion of cells arrested in the G2/M-phase. Conclusions: These data demonstrate that RBM3 expression is associated with cisplatin sensitivity in vitro and with a good prognosis in EOC. Taken together these findings suggest that RBM3 may be a useful prognostic and treatment predictive marker in EOC.
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| 4. |
- Ehlén, Åsa
(författare)
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The role of RNA-binding motif 3 in epithelial ovarian cancer: A biomarker discovery approach
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Epithelial ovarian cancer (EOC) is the most lethal of all gynaecological malignancies and there is an urgent need to develop new prognostic and treatment predictive biomarkers for a more efficient therapy. The discovery of the RNA-binding motif protein 3 (RBM3) as a putative cancer biomarker was based on its differential expression in various cancer forms in the Human Protein Atlas (HPA). Further investigations demonstrated an association between high nuclear RBM3 expression and improved survival in breast cancer. In this thesis, the prognostic value of RBM3 was examined at the mRNA and protein levels in two independent EOC cohorts, whereby increased expression of RBM3 was found to be associated with a favorable prognosis. Further in vitro studies revealed a sensitizing effect of RBM3 to the platinum compound cisplatin. With the aim to indentify underlying biological processes associated with RBM3 expression in EOC we performed a gene set enrichment analysis and uncovered an association between RBM3 expression and several cellular processes involved in the maintenance of DNA integrity, including DNA replication, chromatin remodeling and DNA integrity checkpoint. The RBM3 regulated genes were subsequently screened in the HPA and proteins displaying a differential expression pattern among EOC samples were further analyzed in EOC cell lines. An inverse correlation was observed between RBM3 and MCM3, Chk1 and Chk2. The prognostic value of theses markers was investigated in two EOC cohorts revealing an association between Chk1, Chk2 and MCM3 expression and an impaired survival. In addition, we investigated a possible involvement of RBM3 in the cell cycle process and observed a delay in S-phase progression upon downregulation of RBM3 in a synchronized cell population, suggesting a possible role of RBM3 in DNA replication.
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| 5. |
- Ehlén, Åsa, et al.
(författare)
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Tumors with non-functional RB1 are killed by reduced gamma-tubulin levels.
- 2012
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 287:21, s. 17241-17247
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Tidskriftsartikel (refereegranskat)abstract
- In various tumors inactivation of growth control is achieved by interfering with the RB1 signaling pathway. Here, we describe that RB1 and γ tubulin proteins moderate each other's expression by binding to their respective gene promoters. Simultaneous reduction of RB1 and γ tubulin protein levels result in an E2F1-dependent upregulation of apoptotic genes such as caspase 3. We report that in various tumors types, there is an inverse correlation between the expression levels of γ tubulin and RB1 and that in tumor cell lines with a non-functioning RB1, reduction of γ tubulin protein levels leads to induction of apoptosis. Thus, the RB1/γ tubulin signal network can be considered as a new target for cancer treatment.
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| 6. |
- Eklund, Greta, et al.
(författare)
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The nuclear localization of γ-tubulin is regulated by SadB-mediated phosphorylation.
- 2014
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 289:31, s. 21360-21373
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Tidskriftsartikel (refereegranskat)abstract
- γ-tubulin is an important cell division regulator that arranges microtubule assembly and mitotic spindle formation. Cytosolic γ-tubulin nucleates α- and β-tubulin in a growing microtubule by forming the ring-shaped protein complex γTuRC. Nuclear γ-tubulin also regulates S-phase progression by moderating the activities of E2Fs. The mechanism that regulates localization of γ-tubulin is currently unknown. Here, we describe that the human Ser/Thr kinase SadB short localizes to chromatin and centrosomes. We found that SadB-mediated phosphorylation of γ-tubulin on Ser 385 triggered formation of chromatin associated γ-tubulin complexes that moderates gene expression. In this way, the C terminal region of γ-tubulin regulates S-phase progression. In addition, chromatin levels of γ-tubulin were decreased by reduction of SadB levels or expression of a non-phosphorylatable Ala-385-γ-tubulin, but were enhanced by expression of SadB, wild-type γ-tubulin, or a phosphomimetic Asp-385-γ-tubulin mutant. Our results demonstrate that SadB kinases regulate the cellular localization of γ-tubulin and thereby control S-phase progression.
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| 7. |
- Jang, Sung-Wuk, et al.
(författare)
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Serine/arginine protein-specific kinase 2 promotes leukemia cell proliferation by phosphorylating acinus and regulating cyclin A1
- 2008
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Ingår i: Cancer Research. - 1538-7445 .- 0008-5472. ; 68:12, s. 4559-4570
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Tidskriftsartikel (refereegranskat)abstract
- Serine/arginine (SR) protein-specific kinase (SRPK), a family of cell cycle-regulated protein kinases, phosphorylate SR domain-containing proteins in nuclear speckles and mediate the pre-mRNA splicing. However, the physiologic roles of this event in cell cycle are incompletely understood. Here, we show that SRPK2 binds and phosphorylates acinus, an SR protein essential for RNA splicing, and redistributes it from the nuclear speckles to the nucleoplasm, resulting in cyclin A1 but not A2 up-regulation. Acinus S422D, an SRPK2 phosphorylation mimetic, enhances cyclin A1 transcription, whereas acinus S422A, an unphosphorylatable mutant, blocks the stimulatory effect of SRPK2. Ablation of acinus or SRPK2 abrogates cyclin A1 expression in leukemia cells and arrest cells at G, phase. Overexpression of acinus or SRPK2 increases leukemia cell proliferation. Furthermore, both SRPK2 and acinus are overexpressed in some human acute myelogenous leukemia patients and correlate with elevated cyclin A1 expression levels, fitting with the oncogenic activity of cyclin A1 in leukemia. Thus, our findings establish a molecular mechanism by which SR splicing machinery regulates cell cycle and contributes to leukemia tumorigenesis.
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