elastin and Glioma

Exosomes appear to be effective inter-cellular communicators delivering several types of molecules, such as proteins and RNAs, suggesting that they could influence neural stem cell (NSC) differentiation. Our RNA sequencing studies demonstrated that the RNAs related to cell proliferation and astrocyte differentiation were upregulated in human mesenchymal stem cells (hMSC) when co-cultured with exosomes obtained from the culture medium of human glioma cells (U87). Metallothionein 3 and elastin genes, which are related to cell proliferation, increased 10 and 7.2 fold, respectively. Expression of genes for astrocyte differentiation, such as tumor growth factor alpha, induced protein 3 of the NOTCH1 family, colony stimulating factor and interleukin 6 of the STAT3 family and Hes family bHLH transcription factor 1 also increased by 2.3, 10, 4.7 and 2.9 fold, respectively. We further examined the effects of these exosomes on rat fetal neural stem cell (rNSC) differentiation using the secreted exosomes from U87 glioma cells or exosomes from U87 cells that were stimulated with interleukin 1β (IL-1β). The rNSCs, extracted from rat brains at embryonic day 14 (E14), underwent a culture protocol that normally leads to predominant (~90%) differentiation to ODCs. However, in the presence of the exosomes from untreated or IL-1β-treated U87 cells, significantly more cells differentiated into astrocytes, especially in the presence of exosomes obtained from the IL-1β-challenged glioma cells. Moreover, glioma-derived exosomes appeared to inhibit rNSC differentiation into ODCs or astrocytes as indicated by a significantly increased population of unlabeled cells. A portion of the resulting astrocytes co-expressed both CD133 and glial fibrillary acidic protein (GFAP) suggesting that exosomes from U87 cells could promote astrocytic differentiation of NSCs with features expected from a transformed cell. Our data clearly demonstrated that exosomes secreted by human glioma cells provide a strong driving force for rat neural stem cells to differentiate into astrocytes, uncovering potential pathways and therapeutic targets that might control this aggressive tumor type.

Topics: Animals; Astrocytes; Cell Differentiation; Cell Proliferation; Cells, Cultured; Coculture Techniques; Elastin; Exosomes; Gene Expression Regulation; Glioma; Humans; Interleukin-6; Metallothionein 3; Nerve Tissue Proteins; Neural Stem Cells; Neurons; Primary Cell Culture; Rats; STAT3 Transcription Factor

Elastin-like polypeptides (ELPs) are biopolymers of the pentapeptide repeat Val-Pro-Gly-Xaa-Gly that undergo an inverse temperature phase transition. They are soluble in aqueous solutions below their transition temperature (T1) but hydrophobically collapse and aggregate at temperatures greater than T1. We hypothesized that ELPs conjugated to drugs would enable thermally targeted drug delivery to solid tumors if their T1 were between body temperature and the temperature in a locally heated region. To test this hypothesis, we synthesized a thermally responsive ELP with a T1 of 41 degrees C and a thermally unresponsive control ELP in Escherichia coli using recombinant DNA techniques. In vivo fluorescence videomicroscopy and radiolabel distribution studies of ELP delivery to human tumors (SKOV-3 ovarian carcinoma and D-54MG glioma) implanted in nude mice demonstrated that hyperthermic targeting of the thermally responsive ELP for 1 h provides a approximately 2-fold increase in tumor localization compared to the same polypeptide without hyperthermia. We observed aggregates of the thermally responsive ELP by fluorescence videomicroscopy within the heated tumor microvasculature but not in control experiments, which demonstrates that the phase transition of the thermally responsive ELP carrier can be engineered to occur in vivo at a specified temperature. By exploiting the phase transition-induced aggregation of these polypeptides, this method provides a new way to thermally target polymer-drug conjugates to solid tumors.

Topics: Amino Acid Sequence; Animals; Base Sequence; Drug Stability; Elastin; Female; Glioma; Humans; Hyperthermia, Induced; Mice; Mice, Inbred BALB C; Mice, Nude; Microscopy, Fluorescence; Microscopy, Video; Molecular Sequence Data; Ovarian Neoplasms; Peptides; Protein Engineering; Temperature; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

We have recently shown that glioma cell lines, as well as cells of human malignant gliomas in situ, synthesize tropoelastin. In addition, glioma cells degrade tropoelastin using metalloproteinase(s), and the resulting peptides, incapable of assembling in the extracellular fibers, interact with the 67-kDa cell surface elastin binding protein (EBP), to transduce signals leading to up-regulation of cell proliferation. In this report, we show that exposure to the polysulfonated bis-naphthylurea suramin causes accumulation of physiologically active EBP molecules on the cell surface of a panel of glioma cell lines (U87, MG, U251 MG, U343 MG-A, U373 MG, SF 126, SF188, SF539), which results in an increase of cellular attachment to elastin-coated dishes and in an efficient binding of radiolabeled tropoelastin. Moreover, 100-200 microM suramin stimulates [3H]-thymidine incorporation by those tropoelastin-producing glioma cell lines, but not by A 2058 melanoma cells, which do not produce elastin. Treatment of all glioma cell lines with 100 microM suramin consistently increased expression of cyclin A and its cyclin-dependent kinase, cdk 2, to levels reached following the exposure to exogenous elastin-degradation products (kappa-elastin). Our data suggest that a suramin-stimulated accumulation of EBP molecules on the cell surface of glioma cells amplifies the elastin-derived signals, leading to their progression through the cell cycle.

Topics: Cell Division; Culture Media, Serum-Free; Cyclin-Dependent Kinases; Cyclins; Dose-Response Relationship, Drug; Elastin; Glioma; Humans; Intracellular Fluid; Laminin; Receptors, Cell Surface; Signal Transduction; Suramin; Thymidine; Tritium; Tropoelastin; Tumor Cells, Cultured; Up-Regulation