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- Alkharusi, Amira Said Mohammed
(författare)
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Conditions associated with increased growth hormone and prolactin sensitivity
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Growth Hormone (GH) and Prolactin (PRL) are critical regulators of body growth and metabolism. Secretion and actions of GH and PRL are regulated at several levels and by different factors. The biological actions of these hormones are initiated by their binding to the respective membrane bound receptors of GH and PRL (GHR and PRLR). Several hormone systems are characterized by changes in target tissue sensitivity. Key factors in hormone sensitivity include the number of particular receptors and the duration of receptor activated intracellular signals. A common theme concerning this is e.g. that tyrosine phosphorylated intracellular proteins become inactivated by tyrosine phosphatases or by proteasomal breakdown. In this thesis a particular focus is put on two different proteins, Suppressors of Cytokine Signaling2 (SOCS2) and Tuberous Sclerosis Complex2 (TSC2) that uniquely impinge on JAK-STAT activation and on mTOR activation. Study I. We explored the influence of SOCS2 on glucose metabolism by using a mouse model of diabetes induced by multiple low dose streptozotocin (MLDSTZ). Pancreatic islets from untreated SOCS2-/- mice appeared larger than in wild-type (WT) controls, which could explain the augmented serum insulin levels observed in SOCS2-/- mice. Pancreatic islets, derived from SOCS2-/- mice showed increased GHR and PRLR staining, which suggest a higher sensitivity to GH/PRL-STAT5 signals in SOCS2-/- than in WT-derived β-cells. Our results suggest that SOCS2 ablation can partly overcome β-cell destruction induced by MLDSTZ. Study II and III. In these studies we aimed to investigate the relevance of PRL in two different human tumors, i.e. lymphangioleiomyomatosis (LAM) and glioblastoma (GBM), by analyzing features of the PRLR and the effect of a novel PRLR antagonist (PRLRA) in such tumors. Reduction of TSC2 (the disease causing gene in LAM) increased PRLR levels in LAM cells and PRL stimulated LAM cell proliferation; an effect that could be blocked with the PRLRA. In GBM, PRLR was detectable in cultured GBM cells as well as in tissue sections from patients with GBM. In cell culture GBM studies, PRL treatment increased STAT5 phosphorylation as well as cell invasion and both effects could be blocked by the PRLRA. In summary, our studies indicate that the tissue sensitivity to GH/PRL is regulated by SOCS2 and TSC2 proteins. Since both SOCS2 and TSC2 have links to different disorders, an increased GH/PRL sensitivity in such conditions could play a functional role. To block an increased PRL sensitivity we have developed a novel PRLRA and demonstrated its efficacy in cell cultures.
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| 2. |
- Alkharusi, Amira, et al.
(författare)
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Stimulation of prolactin receptor induces STAT-5 phosphorylation and cellular invasion in glioblastoma multiforme
- 2016
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Ingår i: Oncotarget. - : Impact Journals LLC. - 1949-2553. ; 7:48, s. 79558-79569
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Tidskriftsartikel (refereegranskat)abstract
- Glioblastoma multiforme (GBM) is the most common and aggressive primary brain tumor in humans and is characterized with poor outcome. In this study, we investigated components of prolactin (Prl) system in cell models of GBM and in histological tissue sections obtained from GBM patients. Expression of Prolactin receptor (PrlR) was detected at high levels in U251-MG, at low levels in U87-MG and barely detectable in U373 cell lines and in 66% of brain tumor tissues from 32 GBM patients by immunohistochemical technique. In addition, stimulation of U251-MG and U87-MG cells but not U373 with Prl resulted in increased STAT5 phosphorylation and only in U251-MG cells with increased cellular invasion. Furthermore, STAT5 phosphorylation and cellular invasion induced in Prl stimulated cells were significantly reduced by using a Prl receptor antagonist that consists of Prl with four amino acid replacements. We conclude that Prl receptor is expressed at different levels in the majority of GBM tumors and that blocking of PrlR in U251-MG cells significantly reduce cellular invasion.
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| 3. |
- Yu, Shengze, et al.
(författare)
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An in vivo half-life extended prolactin receptor antagonist can prevent STAT5 phosphorylation
- 2019
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Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 14:5
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Tidskriftsartikel (refereegranskat)abstract
- Increasing evidence suggests that signaling through the prolactin/prolactin receptor axis is important for stimulation the growth of many cancers including glioblastoma multiforme, breast and ovarian carcinoma. Efficient inhibitors of signaling have previously been developed but their applicability as cancer drugs is limited by the short in vivo half-life. In this study, we show that a fusion protein, consisting of the prolactin receptor antagonist PrlRA and an albumin binding domain for half-life extension can be expressed as inclusion bodies in Escherichia coli and efficiently refolded and purified to homogeneity. The fusion protein was found to have strong affinity for the two intended targets: the prolactin receptor (K-D = 2.3 +/- 0.2 nM) and mouse serum albumin (K-D = 0.38 +/- 0.01 nM). Further investigation showed that it could efficiently prevent prolactin mediated phosphorylation of STAT5 at 100 nM concentration and above, similar to the PrlRA itself, suggesting a potential as drug for cancer therapy in the future. Complexion with HSA weakened the affinity for the receptor to 21 +/- 3 nM, however the ability to prevent phosphorylation of STAT5 was still prominent. Injection into rats showed a 100-fold higher concentration in blood after 24 h compared to PrlRA itself.
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