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- Deng, Hua, et al.
(författare)
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Over-accumulation of nuclear IGF-1 receptor in tumor cells requires elevated expression of the receptor and the SUMO-conjugating enzyme Ubc9
- 2011
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 404:2, s. 667-671
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Tidskriftsartikel (refereegranskat)abstract
- The insulin-like growth factor 1 receptor (IGF-1R) plays crucial roles in tumor cell growth and is overexpressed in many cancers. IGF-1R's trans-membrane kinase signaling pathways have been well characterized. Very recently, we showed that SUMOylation mediates nuclear translocation of the IGF-1R, and that nuclear IGF-1R (nIGF-1R) binds to enhancer regions and activates transcription. We identified three lysine residues in the beta-subunit of the receptor and that mutation of these blocks nuclear translocation and gene activation. Furthermore, accumulation of nIGF-1R was proven strongly dependent on the specific SUMO-conjugating enzyme Ubc9. Here we show that nIGF-1R originates solely from the cell membrane and that phosphorylation of the core tyrosine residues of the receptor kinase is crucial for nuclear accumulation. We also compared the levels of nIGF-1R, measured as nuclear/membrane ratios, in tumor and normal cells. We found that the breast cancer cell line MCF-7 has 13-fold higher amounts of nIGF-1R than breast epithelial cells (IME) which showed only a small amount of nIGF-1R. In comparison, the total expression of IGF-1R was only 3.7-higher in MCF-7. Comparison of several other tumor and normal cell lines showed similar tumor cell over-accumulation of nIGF-1R, exceeding the total receptor expression substantially. Ectopic overexpression (>10-fold) of the receptor increased nIGF-1R in IME cells but not to that high level as in wild type MCF-7. The levels of Ubc9 were higher in all tumor cell lines, compared to the normal cells, and this probably contributes to over-accumulation of nIGF-1R. Over-accumulation of nIGF-1R may contribute to deregulated gene expression and therewith play a pathophysiological role in cancer cells.
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| 2. |
- Hashemi, Jamileh, et al.
(författare)
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Molecular Characterization of Acquired Tolerance of Tumor Cells to Picropodophyllin (PPP)
- 2011
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:3, s. e14757-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Picropodophyllin (PPP) is a promising novel anti-neoplastic agent that efficiently kills tumor cells in vitro and causes tumor regression and increased survival in vivo. We have previously reported that PPP treatment induced moderate tolerance in two out of 10 cell lines only, and here report the acquired genomic and expression alterations associated with PPP selection over 1.5 years of treatment. Methodology/Principal Findings: Copy number alterations monitored using metaphase and array-based comparative genomic hybridization analyses revealed largely overlapping alterations in parental and maximally tolerant cells. Gain/amplification of the MYC and PVT1 loci in 8q24.21 were verified on the chromosome level. Abnormalities observed in connection to PPP treatment included regular gains and losses, as well as homozygous losses in 10q24.1-q24.2 and 12p12.3-p13.2 in one of the lines and amplification at 5q11.2 in the other. Abnormalities observed in both tolerant derivatives include amplification/gain of 5q11.2, gain of 11q12.1-q14.3 and gain of 13q33.3-qter. Using Nexus software analysis we combined the array-CGH data with data from gene expression profilings and identified genes that were altered in both inputs. A subset of genes identified as downregulated (ALDH1A3, ANXA1, TLR4 and RAB5A) or upregulated (COX6A1, NFIX, ME1, MAPK and TAP2) were validated by siRNA in the tolerant or parental cells to alter sensitivity to PPP and confirmed to alter sensitivity to PPP in further cell lines. Conclusions: Long-term PPP selection lead to altered gene expression in PPP tolerant cells with increase as well as decrease of genes involved in cell death such as PTEN and BCL2. In addition, acquired genomic copy number alterations were observed that were often reflected by altered mRNA expression levels for genes in the same regions.
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| 3. |
- Ulfarsson, Elfar, et al.
(författare)
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Expression and growth dependency of the insulin-like growth factor I receptor in craniopharyngioma cells : A novel therapeutic approach
- 2005
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Ingår i: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 11:13, s. 4674-4680
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Tidskriftsartikel (refereegranskat)abstract
- Craniopharyngioma is a rare benign intracranial epithelial tumor that, however, often recurs and sometimes kills the affected patients, one-third of which are children. In many cases, the patients acquire growth hormone deficiency and postoperatively need substitution. Generally, growth hormone promotes local release of insulin-like growth factor I (IGF-I), which in turn activates the IGF-I receptor (IGF-IR) if present. Together, these circumstances raise the question whether IGF-IR may be involved in craniopharyngioma growth. To address this issue, we analyzed phenotypically well-characterized primary low-passage craniopharyngioma cell lines from nine different patients for IGF-IR expression and IGF-I dependency. Two of the cell lines showed no/very low expression of the receptor and was independent on IGF-I, whereas five cell lines exhibited a strong expression and was clearly contingent on IGF-I. The two remaining cell lines had low receptor expression and IGF-I dependency. Upon treatment with an IGF-IR inhibitor, cells with high IGF-IR expression responded promptly with decreased Akt phosphorylation followed by growth arrest. These responses were not seen in cells with no/very low receptor expression. Growth of cell lines with tow IGF-IR expression was only slightly affected by IGF-IR inhibition. Taken together, our data suggest that IGF-IR may be involved in the growth of a subset of craniopharyngiomas and points to the possibility of the involvement of IGF-IR inhibitors as a treatment modality to obtain complete tumor-free conditions before growth hormone substitution. © 2005 American Association for Cancer Research.
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| 4. |
- Vasilcanu, Daiana
(författare)
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IGF-1R inhibition : a tool for functional studies of insulin-like growth factor family in malignant cells
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cancer cells generally posses the capability of overusing normal extracellular signaling for proliferation and/or anti-apoptosis to create growth advantage over the normal cells. Major players in extracellular signaling are the growth factor receptors. Among them, an activated IGF-1R is important for the establishment of a malignant cell phenotype. Interestingly, the targeting of IGF-1R can reverse the malignant phenotype in cancer cells and render them sensitive to apoptosis, without seriously affecting the biology of normal cells. For these reasons, IGF-1R seems to be a very promising target in cancer therapy. Recently, we demonstrated that the cyclolignan PPP efficiently inhibited phosphorylation of IGF-1R without interfering with insulin receptor activity. This thesis is centered on: (1) functional studies of IGF-1R using PPP as a tool, with focus on importance for survival and proliferation of malignant cells as well as possible mechanisms of PPP action; (2) possible caveats in clinical applications of PPP (e.g. resistance, side effects secondary to IGF-1R inhibition, effects on glucose uptake). Using a IGF-1R tyrosine kinase construct, isolated by immunoprecipitation and amplified in insect cells, we found that PPP decreased phosphorylation of tyrosine residue (Y) 1136 in the activation loop of the IGF-1R kinase domain. Studies using dominant-negative constructs of IGF-1R (in which specific tyrosine residues are replaced by phenylalanine) suggest that the inhibition of Y 1136 phosphorylation may be important for the inhibition of Akt phosphorylation seen in PPP treated cell cultures. Whether PPP directly or indirectly (e.g. by interfering with IGF-1R associated proteins) inhibits Y1136 phosphorylation is still unknown. It was confirmed that inhibitions of downstream reactions of the phosphatyl inositol-3 kinase/anti-apoptotic pathway (e.g. attenuated Bad phosphorylation, PARP cleavage, caspase activation) were a consequence of the PPP-induced inhibition of IGF-1R. (Paper 1) We demonstrated the presence and growth dependence of IGF-1R in primary cultured craniopharyngioma cells from a subset of affected patients (5 out of 9). Upon treatment with PPP, cells with high IGF-1R expression responded promptly with decreased Akt phosphorylation followed by cell growth inhibition, whereas these responses did not appear in cells with low receptor expression. Our data points to the possibility of using IGF-1R inhibitors (e.g. PPP) as a treatment modality to obtain complete tumor-free conditions before growth hormone substitution. (Paper 2) A general concern with antitumor agents is development of resistance. In light of this problem we aimed to investigate whether malignant cells may develop serious resistance to PPP. After trying to select several malignant cell lines, only two out of 10 survived an 80-week selection. We could observe a temporary and limited increase in IGF-I R expression but there were no rearrangements or amplification of the IGF-1R gene. The resistant cell lines did not exhibit cross-resistance to known cytostatic dugs. In conclusion, no or slight resistance to PPP occurred. (Paper 3) Finally, we confirmed that PPP does not inhibit activity of the highly related insulin receptor and induce diabetogenic effects (like high blood glucose). Instead, in vivo and in vitro studies showed that PPP treatment reduces the blood glucose levels in mice and induces increase of glucose uptake in cells expressing the insulin-dependent glucose-transporter GLUT-4. (Paper 4)
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