ABSTRACT
BACKGROUND: Temozolomide (TMZ) is the first-line chemotherapeutic drug for gliomas treatment. However, the clinical efficacy of TMZ in glioma patients was very limited. Therefore, it is urgently needed to discover a novel approach to increase the sensitivity of glioma cells to TMZ. METHODS: Western blot, immunohistochemical staining, and qRT-PCR assays were used to explore the mechanisms underlying TMZ promoting DKK1 expression and andrographolide (AND) inhibiting DKK1 expression. HPLC was used to detect the ability of andrographolide (AND) to penetrate the blood-brain barrier. MTT assay, bioluminescence images, magnetic resonance imaging (MRI) and H&E staining were employed to measure the proliferative activity of glioma cells and the growth of intracranial tumors. RESULTS: TMZ can promote DKK1 expression in glioma cells and brain tumors of an orthotopic model of glioma. DKK1 could promote glioma cell proliferation and tumor growth in an orthotopic model of glioma. Mechanistically, TMZ increased EGFR expression and subsequently induced the activation of its downstream MEK-ERK and PI3K-Akt pathways, thereby promoting DKK1 expression in glioma cells. Andrographolide inhibited TMZ-induced DKK1 expression through inactivating MEK-ERK and PI3K-Akt pathways. Andrographolide can cross the blood-brain barrier, the combination of TMZ and andrographolide not only improved the anti-tumor effects of TMZ but also showed a survival benefit in an orthotopic model of glioma. CONCLUSION: Andrographolide can enhance anti-tumor activity of TMZ against glioma by inhibiting DKK1 expression.
Subject(s)
Antineoplastic Agents, Alkylating , Brain Neoplasms , Cell Proliferation , Diterpenes , Glioma , Intercellular Signaling Peptides and Proteins , Temozolomide , Diterpenes/pharmacology , Diterpenes/therapeutic use , Temozolomide/pharmacology , Glioma/drug therapy , Glioma/pathology , Glioma/genetics , Glioma/metabolism , Intercellular Signaling Peptides and Proteins/genetics , Intercellular Signaling Peptides and Proteins/metabolism , Humans , Animals , Brain Neoplasms/drug therapy , Brain Neoplasms/pathology , Brain Neoplasms/metabolism , Brain Neoplasms/genetics , Cell Line, Tumor , Mice , Antineoplastic Agents, Alkylating/pharmacology , Antineoplastic Agents, Alkylating/therapeutic use , Cell Proliferation/drug effects , Xenograft Model Antitumor Assays , Blood-Brain Barrier/drug effects , Blood-Brain Barrier/metabolism , Mice, Nude , Gene Expression Regulation, Neoplastic/drug effects , Drug Synergism , ErbB Receptors/genetics , ErbB Receptors/antagonists & inhibitors , Signal Transduction/drug effectsABSTRACT
Autofluorescent bovine serum albumin (BSA) hydrogel microspheres were prepared through the spray-drying of glutaraldehyde cross-linked BSA nanoparticles and then used for a proteinase K based degradation study in an aqueous solution. Experimental results and empirical models are presented to characterize the kinetics of BSA hydrogel microsphere degradation, as well as the accompanying release of synthesized fluorophore. The BSA gel degradation dynamics is primarily controlled by the concentration of proteinase K within the Tris buffer. The coupling of swelling dynamics and the transient distributions of fluorophore are traced by confocal microscopy. Models are developed based on the linear theory of elastic deformation coupled to enzyme and fluorophore transport. This study represents a fundamental investigation of the degradation and release kinetics of protein-based materials, which can potentially be applied for the dynamic and photostable tracking of relevant in vivo systems.
Subject(s)
Endopeptidase K/metabolism , Fluorescent Dyes/chemistry , Microspheres , Proteolysis , Serum Albumin, Bovine/chemistry , Serum Albumin, Bovine/metabolism , Animals , Cattle , Glutaral/chemistry , Hydrogels/chemistry , Models, Molecular , Protein ConformationABSTRACT
Bulk solutions of therapeutic proteins are often frozen for long-term storage. During the freezing process, proteins in liquid solution redistribute and segregate in the interstitial space between ice crystals. This is due to solute exclusion from ice crystals, higher viscosity of the concentrated solution, and space confinement between crystals. Such segregation may have a negative impact on the native conformation of protein molecules. To better understand the mechanisms, we developed a phase-field model to describe the growth of ice crystals and the dynamics of freeze concentration at the mesoscale based on mean field approximation of solute concentration and the underlying heat, mass and momentum transport phenomena. The model focuses on evolution of the interfaces between liquid solution and ice crystals, and the degree of solute concentration due to partition, diffusive, and convective effects. The growth of crystals is driven by cooling of the bulk solution, but suppressed by a higher solute concentration due to increase of solution viscosity, decrease of freezing point, and the release of latent heat. The results demonstrate the interplay of solute exclusion, space confinement, heat transfer, coalescence of crystals, and the dynamic formation of narrow gaps between crystals and Plateau border areas along with correlations of thermophysical properties in the supercooled regime.