| 1. |
- Akhoondi, Shahab, et al.
(författare)
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FBXW7/hCDC4 is a general tumor suppressor in human cancer
- 2007
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Ingår i: Cancer Research. - 0008-5472 .- 1538-7445. ; 67:19, s. 9006-9012
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Tidskriftsartikel (refereegranskat)abstract
- The ubiquitin-proteasome system is a major regulatory pathway of protein degradation and plays an important role in cellular division. Fbxw7 (or hCdc4), a member of the F-box family of proteins, which are substrate recognition components of the multisubunit ubiquitin ligase SCF (Skpl-Cdc53/ Cullin-F-box-protein), has been shown to mediate the ubiquitin-dependent proteolysis of several oncoproteins including cyclin El, c-Myc, c-Jun, and Notch. The oncogenic potential of Fbxw7 substrates, frequent allelic loss in human cancers, and demonstration that mutation of FBXW7 cooperates with p53 in mouse tumorigenesis have suggested that Fbxw7 could function as a tumor suppressor in human cancer. Here, we carry out an extensive genetic screen of primary tumors to evaluate the role of FBXW7 as a tumor suppressor in human tumorigenesis. Our results indicate that FBXW7 is inactivated by mutation in diverse human cancer types with an overall mutation frequency of ∼ 6%. The highest mutation frequencies were found in tumors of the bile duct (cholangio-carcinomas, 35%), blood (T-cell acute lymphocytic leukemia, 31%), endometrium (9%), colon (9%), and stomach (6%). Approximately 43% of all mutations occur at two mutational "hotspots," which alter Arg residues (Arg465 and Arg479) that are critical for substrate recognition. Furthermore, we show that Fbxw7Arg465 hotspot mutant can abrogate wild-type Fbxw7 function through a dominant negative mechanism. Our study is the first comprehensive screen of FBXW7 mutations in various human malignancies and shows that FBXW7 is a general tumor suppressor in human cancer.
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| 2. |
- Almuzzaini, Bader, et al.
(författare)
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In beta-actin knockouts, epigenetic reprogramming and rDNA transcription inactivation lead to growth and proliferation defects
- 2016
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Ingår i: The FASEB Journal. - 0892-6638 .- 1530-6860. ; 30:8, s. 2860-2873
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Tidskriftsartikel (refereegranskat)abstract
- Actin and nuclear myosin 1 (NM1) are regulators of transcription and chromatin organization. Using a genome-wide approach, we report here that beta-actin binds intergenic and genic regions across the mammalian genome, associated with both protein-coding and rRNA genes. Within the rDNA, the distribution of beta-actin correlated with NM1 and the other subunits of the B-WICH complex, WSTF and SNF2h. In beta-actin(-/-) mouse embryonic fibroblasts (MEFs), we found that rRNA synthesis levels decreased concomitantly with drops in RNA polymerase I (Pol I) and NM1 occupancies across the rRNA gene. Reintroduction of wild-type beta-actin, in contrast to mutated forms with polymerization defects, efficiently rescued rRNA synthesis underscoring the direct role for a polymerization-competent form of beta-actin in Pol I transcription. The rRNA synthesis defects in the beta-actin(-/-) MEFs are a consequence of epigenetic reprogramming with up-regulation of the repressive mark H3K4me1 (mono-methylation of lys4 on histone H3) and enhanced chromatin compaction at promoter-proximal enhancer (T0 sequence), which disturb binding of the transcription factor TTF1. We propose a novel genome-wide mechanism where the polymerase-associated beta-actin synergizes with NM1 to coordinate permissive chromatin with Pol I transcription, cell growth, and proliferation.
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| 3. |
- Bolin, Sara, 1988-, et al.
(författare)
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Dormant SOX9-positive cells behind MYC-driven medulloblastoma recurrence
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Tidskriftsartikel (refereegranskat)abstract
- Tumor recurrence is a slow biological process involving therapy resistance, immune escape, and metastasis and is the leading cause of death in medulloblastoma, the most frequent malignant pediatric brain tumor. By studying paired primary-recurrent patient samples and patient-derived xenografts we identified a significant accumulation of SOX9-positive cells in relapses and metastases. They exist as rare, quiescent cells in Group 3 and Group 4 patients that constitute two-thirds of medulloblastoma. To follow relapse at the single-cell level we developed an inducible dual Tet model of MYC-driven MB, where MYC can be directed from treatment-sensitive bulk cells to resistant, dormant SOX9-positive cells by doxycycline. SOX9 promoted immune es-cape, DNA repair suppression and was essential for recurrence. Tumor cell dormancy was non-hierarchical, migratory, and depended on MYC suppression by SOX9 to promote relapse. By using computational modeling and treatment we further showed how doxorubicin and MGMT inhibitors are specifically targeting relapsing cells.
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| 4. |
- Borgenvik, Anna, 1987-, et al.
(författare)
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Dormant SOX9-Positive Cells Facilitate MYC-Driven Recurrence of Medulloblastoma
- 2022
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Ingår i: Cancer Research. - : AMER ASSOC CANCER RESEARCH. - 0008-5472 .- 1538-7445. ; 82:24, s. 4586-4603
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Tidskriftsartikel (refereegranskat)abstract
- Relapse is the leading cause of death in patients with medulloblas-toma, the most common malignant pediatric brain tumor. A better understanding of the mechanisms underlying recurrence could lead to more effective therapies for targeting tumor relapses. Here, we observed that SOX9, a transcription factor and stem cell/glial fate marker, is limited to rare, quiescent cells in high-risk medulloblastoma with MYC amplification. In paired primary-recurrent patient samples, SOX9-positive cells accumulated in medulloblastoma relapses. SOX9 expression anti-correlated with MYC expression in murine and human medulloblastoma cells. However, SOX9-positive cells were plastic and could give rise to a MYC high state. To follow relapse at the single-cell level, an inducible dual Tet model of medulloblastoma was developed, in which MYC expression was redirected in vivo from treatment-sensitive bulk cells to dormant SOX9-positive cells using doxycycline treatment. SOX9 was essential for relapse initiation and depended on suppression of MYC activity to promote therapy resistance, epithelial-mesenchymal transition, and immune escape. p53 and DNA repair pathways were downregulated in recurrent tumors, whereas MGMT was upregulated. Recurrent tumor cells were found to be sensitive to treatment with an MGMT inhibitor and doxorubicin. These findings suggest that recurrence-specific targeting coupled with DNA repair inhibition comprises a potential therapeutic strategy in patients affected by medulloblastoma relapse.Significance: SOX9 facilitates therapy escape and recurrence in medulloblastoma via temporal inhibition of MYC/MYCN genes, revealing a strategy to specifically target SOX9-positive cells to prevent tumor relapse.
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| 5. |
- Lagging, Martin, 1965, et al.
(författare)
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Treatment of hepatitis C virus infection: updated Swedish Consensus recommendations.
- 2009
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Ingår i: Scandinavian journal of infectious diseases. - : Informa UK Limited. - 1651-1980 .- 0036-5548. ; 41:6-7, s. 389-402
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Tidskriftsartikel (refereegranskat)abstract
- In a recent expert meeting, Swedish recommendations for the treatment of HCV infection were upgraded. The panel recommends vaccination against both hepatitis A and B in patients with HCV. Therapy for symptomatic acute HCV infection should be initiated if spontaneous resolution has not occurred within 12 weeks, whereas asymptomatic acute HCV should be treated upon detection. Patients with genotype 2/3 infection should generally be treated for 24 weeks. In patients with a very rapid viral response (vRVR), i.e. HCV RNA below 1000 IU/ml on d 7, treatment can be shortened to 12-16 weeks, provided that no dose reduction has been made. For genotype 1 patients with rapid viral response (RVR), 24 weeks treatment is recommended. For patients with a complete early viral response (cEVR), 48 weeks treatment is recommended, whereas 72 weeks treatment should be considered for patients with partial early viral response (pEVR). For patients with difficult-to-treat disease and with pronounced anaemia, erythropoietin can be used to maintain the ribavirin dose. In HCV-HIV coinfected patients, combination therapy for HCV should, if possible, be initiated before anti-retroviral therapy (ART) is indicated. For liver transplant patients pre-emptive therapy is not recommended; hence, treatment should be deferred until histological recurrence.
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| 6. |
- Lerner, Mikael, et al.
(författare)
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The RBCC gene RFP2 (leu5) encodes a novel transmembrane E3 ubiquitin ligase involved in ERAD
- 2007
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Ingår i: Molecular Biology of the Cell. - 1059-1524 .- 1939-4586. ; 18:5, s. 1670-1682
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Tidskriftsartikel (refereegranskat)abstract
- RFP2, a gene frequently lost in various malignancies, encodes a protein with RING finger, B-box, and coiled-coil domains that belongs to the RBCC/TRIM family of proteins. Here we demonstrate that Rfp2 is an unstable protein with auto-polyubiquitination activity in vivo and in vitro, implying that Rfp2 acts as a RING E3 ubiquitin ligase. Consequently, Rfp2 ubiquitin ligase activity is dependent on an intact RING domain, as RING deficient mutants fail to drive polyubiquitination in vitro and are stabilized in vivo. Immunopurification and tandem mass spectrometry enabled the identification of several putative Rfp2 interacting proteins localized to the endoplasmic reticulum (ER), including valosin-containing protein (VCP), a protein indispensable for ER-associated degradation (ERAD). Importantly, we also show that Rfp2 regulates the degradation of the known ER proteolytic substrate CD3-delta, but not the N-end rule substrate Ub-R-YFP (yellow fluorescent protein), establishing Rfp2 as a novel E3 ligase involved in ERAD. Finally, we show that Rfp2 contains a C-terminal transmembrane domain indispensable for its localization to the ER and that Rfp2 colocalizes with several ER-resident proteins as analyzed by high-resolution immunostaining. In summary, these data are all consistent with a function for Rfp2 as an ERAD E3 ubiquitin ligase.
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| 7. |
- Malyukova, Alena, et al.
(författare)
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Sequential drug treatment targeting cell cycle and cell fate regulatory programs blocks non-genetic cancer evolution in acute lymphoblastic leukemia
- 2024
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Ingår i: Genome Biology. - 1474-7596 .- 1474-760X. ; 25:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Targeted therapies exploiting vulnerabilities of cancer cells hold promise for improving patient outcome and reducing side-effects of chemotherapy. However, efficacy of precision therapies is limited in part because of tumor cell heterogeneity. A better mechanistic understanding of how drug effect is linked to cancer cell state diversity is crucial for identifying effective combination therapies that can prevent disease recurrence. Results: Here, we characterize the effect of G2/M checkpoint inhibition in acute lymphoblastic leukemia (ALL) and demonstrate that WEE1 targeted therapy impinges on cell fate decision regulatory circuits. We find the highest inhibition of recovery of proliferation in ALL cells with KMT2A-rearrangements. Single-cell RNA-seq and ATAC-seq of RS4;11 cells harboring KMT2A::AFF1, treated with the WEE1 inhibitor AZD1775, reveal diversification of cell states, with a fraction of cells exhibiting strong activation of p53-driven processes linked to apoptosis and senescence, and disruption of a core KMT2A-RUNX1-MYC regulatory network. In this cell state diversification induced by WEE1 inhibition, a subpopulation transitions to a drug tolerant cell state characterized by activation of transcription factors regulating pre-B cell fate, lipid metabolism, and pre-BCR signaling in a reversible manner. Sequential treatment with BCR-signaling inhibitors dasatinib, ibrutinib, or perturbing metabolism by fatostatin or AZD2014 effectively counteracts drug tolerance by inducing cell death and repressing stemness markers. Conclusions: Collectively, our findings provide new insights into the tight connectivity of gene regulatory programs associated with cell cycle and cell fate regulation, and a rationale for sequential administration of WEE1 inhibitors with low toxicity inhibitors of pre-BCR signaling or metabolism.
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| 8. |
- Rahmanto, Aldwin Suryo, et al.
(författare)
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FBW7 suppression leads to SOX9 stabilization and increased malignancy in medulloblastoma
- 2016
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Ingår i: EMBO Journal. - : EMBO. - 0261-4189 .- 1460-2075. ; 35:20, s. 2192-2212
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Tidskriftsartikel (refereegranskat)abstract
- SOX9 is a master transcription factor that regulates development and stem cell programs. However, its potential oncogenic activity and regulatory mechanisms that control SOX9 protein stability are poorly understood. Here, we show that SOX9 is a substrate of FBW7, a tumor suppressor, and a SCF (SKP1/CUL1/F-box)-type ubiquitin ligase. FBW7 recognizes a conserved degron surrounding threonine 236 (T236) in SOX9 that is phosphorylated by GSK3 kinase and consequently degraded by SCFFBW7 alpha. Failure to degrade SOX9 promotes migration, metastasis, and treatment resistance in medulloblastoma, one of the most common childhood brain tumors. FBW7 is either mutated or downregulated in medulloblastoma, and in cases where FBW7 mRNA levels are low, SOX9 protein is significantly elevated and this phenotype is associated with metastasis at diagnosis and poor patient outcome. Transcriptional profiling of medulloblastoma cells expressing a degradation-resistant SOX9 mutant reveals activation of pro-metastatic genes and genes linked to cisplatin resistance. Finally, we show that pharmacological inhibition of PI3K/AKT/mTOR pathway activity destabilizes SOX9 in a GSK3/FBW7-dependent manner, rendering medulloblastoma cells sensitive to cytostatic treatment.
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| 9. |
- Rahmanto, Aldwin Suryo, et al.
(författare)
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Targeting SOX9 for degradation to inhibit chemoresistance, metastatic spread, and recurrence
- 2017
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Ingår i: Molecular & Cellular Oncology. - : Taylor & Francis. - 2372-3556. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- Cancer cells with stem-like properties are believed to contribute to treatment resistance, dissemination, and recurrence. SOX9 controls stem cell plasticity and its deregulation may provide a basis for tumor progression. Here, we summarize our findings of targeted SOX9 destruction by SCFFBW7 (Skp1/Cul1/F-box) in medulloblastoma and its potential for therapeutic intervention.
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| 10. |
- Sangfelt, Olle
(författare)
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Effects of interferon on cellular proliferation and apoptosis
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Interferon (IFN) therapy is today a well-established treatment in many diseases, including various malignancies. How IFN exerts antitumor activity is not known, but several mechanisms have been suggested. Previous studies have shown a correlation between the in vitro susceptibility of primary malignant cells to IFN and the clinical response of the patient to IFN therapy, supporting the idea that the antitumor activity of IFN results from direct effects of IFN on the tumor cells. The studies in the present thesis have dealt with the cellular effects of IFN on both malignant and normal cells, with the focus on how IFN modulates proliferation and apoptosis. In addition to their well-known antiviral effects, IFNs can exert pleiotropic effects on cells, including potent cell growth inhibition of many cell types. Studies on various tumor cell lines and normal cells, as well as primary tumor cells, have established the antiproliferative effect as an important contributor to the decreased number of tumor cells commonly observed following IFN treatment. The role of apoptosis with regard to IFN's anti-cellular effects has so far been poorly defined. Using as a model system a number of hematopoietic cell lines, we showed that IFN-[alpha] in vitro is a potent inducer of apoptotic cell death, and that IFN-[alpha] -mediated growth arrest and apoptosis are independent responses to IFN-[alpha]. IFN-[alpha] induces remissions in approximately 15% of patients with multiple myeloma. We have previously shown that IFN-[alpha] exerts a direct cytotoxic effect on myeloma cells from some patients. Analysis of expression of the apoptosis-inhibitory protein, Bcl-2, in pre-treatment bone-marrow samples from patients with myeloma revealed a significant association (p=0.012) between high levels of Bcl-2 and resistance to IFN-[alpha] therapy. These data indicate that over-expression of Bcl-2 may be a cause for resistance to IFN-[alpha] therapy in myeloma, and that one possible mechanism for IFN's antitumor effect in this disease may be induction of apoptosis. In addition to these cytoreductive effects, IFNs have also in some systems been shown to protect malignant cells from apoptosis induced by different stimuli. In a study of p53-induced apoptosis, IFN-[gamma], but not IFN-[alpha], was found to protect cells from apoptosis. In other studies, the molecular mechanism behind IFN-[alpha] induced cell growth arrest was examined. The effect of IFN-[alpha] on expression of members of the cyclin-dependent kinase inhibitor (CKI) families was investigated in sensitive and resistant tumor cell lines, as well as in normal IL-2-stimulated T-cells. The results demonstrated that IFN-[alpha] is a potent regulator of several CK1s, both from the INK4 family (p15) and the CIP/KIP family (p21 and p27). In sensitive tumor cell lines, a primary response to IFN-[alpha] is induction and binding of p21 to the Gl cyclin dependent kinases (CDKS) CDK4 and CDK2, causing inhibition of these kinases. Secondary events include the increased expression and accumulation of p27 in these G1 CDK complexes, rather than loss of the Gl kinase cyclin components, as well as dephosphorylation of the different pocket proteins. Importantly, in a resistant cell line, p21 protein was not expressed, despite high levels of p21 mRNA following IFN-[alpha] treatment. In normal IL-2 -stimulated T-cells, IFN-[alpha] was found to prevent entry into S-phase, correlating with profound inhibition of IL-2 -induced changes in G 1 regulatory proteins, including the prevention of n-litogen-induced reduction of p27 levels and upregulation of G l cyclins and CDKS.
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| 11. |
- Sangfelt, Per, et al.
(författare)
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A low-dose intradermal hepatitis B vaccine programme in health-care workers and students is highly effective and cost saving : a retrospective follow-up survey in the clinical setting
- 2008
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Ingår i: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 0036-5521 .- 1502-7708. ; 43:4, s. 465-472
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To evaluate compliance, serologic response and the cost-benefit of a low-dose intradermal hepatitis B vaccination programme, followed by intramuscular boosters in non-responders. MATERIAL AND METHODS: The study comprised a retrospective survey of 1521 health-care workers and 968 students. Response was defined as hepatitis B antibody titres > or =10 IU/L. Non-response included vaccinees with undetectable antibodies and a hypo-response if antibodies were detectable. RESULTS: Overall, 2145/2489 (86%) subjects completed the intradermal series, whereof 1840/2489 (74%) complied with the serological check-up. Response was achieved in 1517/1840 (82.5%), whereas 107/1840 (5.8%) had a hypo-response and 216/1840 (11.7%) had an undetectable response. In a logistic regression model, younger age (odds ratio 0.73 (95% CI: 0.65-0.82, p<0.001)) and female gender (odds ratio 2.16 (95% CI: 1.67-2.80; p<0.001)) were predictive of response. In hypo-responders and those with undetectable responses, 43/46 (94%) and 71/136 (52%), respectively, had a response after the first intramuscular booster. Hence, in compliant vaccinees an overall seroprotection rate of 94% was reached after a single intramuscular booster. A cost-benefit analysis indicated a cost reduction exceeding 50% compared to a standard intramuscular vaccine regimen. CONCLUSIONS: In the clinical setting, a low-dose intradermal hepatitis B vaccination programme, followed by intramuscular boosters to non-responders, is effective and cost saving.
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| 12. |
- Sangfelt, Per, et al.
(författare)
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Serum ALT levels as a surrogate marker for serum HBV DNA levels in HBeAg-negative pregnant women
- 2004
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Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 36:3, s. 182-185
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Tidskriftsartikel (refereegranskat)abstract
- In Stockholm, Sweden, the majority of pregnant women positive for hepatitis B surface antigen (HBsAg) are hepatitis Be antigen (HBeAg) negative. Newborns to HBeAg positive mothers receive vaccination and hepatitis B immunoglobulin (HBIg). Newborns to HBeAg negative mothers receive vaccine and HBIg only if the mothers have elevated ALT levels. The aim of this study was to retrospectively evaluate ALT levels as a surrogate marker for HBV DNA levels in HBeAg negative carrier mothers. Altogether 8947 pregnant women were screened for HBV markers from 1999 to 2001 at the Virology Department, Karolinska Hospital. Among mothers screened 192 tested positive for HBsAg (2.2%). 13 of these samples could not be retrieved. Of the remaining 179 sera, 8 (4%) tested positive for HBeAg and 171 (95.5%) were HBeAg negative. Among the HBeAg negative mothers, 9 had HBV DNA levels > 10(5) copies/ml, and of these 7 had normal ALT levels indicating low sensitivity of an elevated ALT level as a surrogate marker for high HBV DNA level. Furthermore, no correlation was found between ALT and HBV DNA levels. Hence, it is concluded that the use of ALT as a surrogate marker for high viral replication in HBeAg negative mothers could be questioned.
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| 13. |
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| 14. |
- Vashisht, Ajay A., et al.
(författare)
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Control of Iron Homeostasis by an Iron-Regulated Ubiquitin Ligase
- 2009
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 326:5953, s. 718-721
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Tidskriftsartikel (refereegranskat)abstract
- Eukaryotic cells require iron for survival and have developed regulatory mechanisms for maintaining appropriate intracellular iron concentrations. The degradation of iron regulatory protein 2 (IRP2) in iron-replete cells is a key event in this pathway, but the E3 ubiquitin ligase responsible for its proteolysis has remained elusive. We found that a SKP1-CUL1-FBXL5 ubiquitin ligase protein complex associates with and promotes the iron-dependent ubiquitination and degradation of IRP2. The F-box substrate adaptor protein FBXL5 was degraded upon iron and oxygen depletion in a process that required an iron-binding hemerythrin-like domain in its N terminus. Thus, iron homeostasis is regulated by a proteolytic pathway that couples IRP2 degradation to intracellular iron levels through the stability and activity of FBXL5.
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| 15. |
- Vidarsdottir, Linda, et al.
(författare)
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PTENP1-AS contributes to BRAF inhibitor resistance and is associated with adverse clinical outcome in stage III melanoma
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- BRAF inhibitors (BRAFi) selectively target oncogenic BRAFV600E/K and are effective in 80% of advanced cutaneous malignant melanoma cases carrying the V600 mutation. However, the development of drug resistance limits their clinical efficacy. Better characterization of the underlying molecular processes is needed to further improve treatments. We previously demonstrated that transcription of PTEN is negatively regulated by the PTEN pseudogene antisense RNA, PTENP1-AS, and here we investigated the impact of this transcript on clinical outcome and BRAFi resistance in melanoma. We observed that increased expression levels of PTENP1-AS in BRAFi resistant cells associated with enrichment of EZH2 and H3K27me3 at the PTEN promoter, consequently reducing the expression levels of PTEN. Further, we showed that targeting of the PTENP1-AS transcript sensitized resistant cells to BRAFi treatment and that high expression of PTENP1-AS in stage III melanoma correlated with poor survival. Collectively, the data presented here show that PTENP1-AS is a promising target for re-sensitizing cells to BRAFi and also a possible prognostic marker for clinical outcome in stage III melanoma.
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