Recombinant IGF-I: Past, present and future

Anti-Gene IGF-I Vaccines in Cancer Gene Therapy: A Review of a Case of Glioblastoma

OBJECTIVE

Vaccines for the deadliest brain tumor - glioblastoma (GBM) - are generally based on targeting growth factors or their receptors, often using antibodies. The vaccines described in the review were prepared to suppress the principal cancer growth factor - IGF-I, using anti-gene approaches either of antisense (AS) or of triple helix (TH) type. Our objective was to increase the median survival of patients treated with AS and TH cell vaccines.

METHODOLOGY

The cells were transfected in vitro by both constructed IGF-I AS and IGF-I TH expression episomal vectors; part of these cells was co-cultured with plant phytochemicals, modulating IGF-I expression. Both AS and TH approaches completely suppressed IGF-I expression and induced MHC-1 / B7 immunogenicity related to the IGF-I receptor signal.

RESULTS

This immunogenicity proved to be stronger in IGF-I TH than in IGF-I AS-prepared cell vaccines, especially in TH / phytochemical cells. The AS and TH vaccines generated an important TCD8+ and TCD8+CD11b- immune response in treated GBM patients and increased the median survival of patients up to 17-18 months, particularly using TH vaccines; in some cases, 2- and 3-year survival was reported. These clinical results were compared with those obtained in therapies targeting other growth factors.

CONCLUSION

The anti-gene IGF-I vaccines continue to be applied in current GBM personalized medicine. Technical improvements in the preparation of AS and TH vaccines to increase MHC-1 and B7 immunogenicity have, in parallel, allowed to increase in the median survival of patients.

Short stature related to Growth Hormone Insensitivity (GHI) in childhood

Linear growth during childhood is the result of the synergic contribution of different factors. The best growth determinant system during each period of life is represented by the growth hormone-insulin-like growth factor axis (GH-IGF), even if several other factors are involved in normal growth. Within the broad spectrum of growth disorders, an increased importance has been placed on growth hormone insensitivity (GHI). GHI was reported for the first time by Laron as a syndrome characterized by short stature due to GH receptor (GHR) mutation. To date, it is recognized that GHI represents a wide diagnostic category, including a broad spectrum of defects. The peculiar characteristic of GHI is the low IGF-1 levels associated with normal or elevated GH levels and the lack of IGF-1 response after GH administration. Recombinant IGF-1 preparations may be used in the treatment of these patients.

Alterations in Stem Cell Populations in IGF-1 Deficient Pediatric Patients Subjected to Mecasermin (Increlex) Treatment

Pathway involving insulin-like growth factor 1 (IGF-1) plays significant role in growth and development. Crucial role of IGF-1 was discovered inter alia through studies involving deficient patients with short stature, including Laron syndrome individuals. Noteworthy, despite disturbances in proper growth, elevated values for selected stem cell populations were found in IGF-1 deficient patients. Therefore, here we focused on investigating role of these cells-very small embryonic-like (VSEL) and hematopoietic stem cells (HSC), in the pathology. For the first time we performed long-term observation of these populations in response to rhIGF-1 (mecasermin) therapy. Enrolled pediatric subjects with IGF-1 deficiency syndrome were monitored for 4-5 years of rhIGF-1 treatment. Selected stem cells were analyzed in peripheral blood flow cytometrically, together with chemoattractant SDF-1 using immunoenzymatic method. Patients' data were collected for correlation of experimental results with clinical outcome. IGF-1 deficient patients were found to demonstrate initially higher levels of VSEL and HSC compared to healthy controls, with their gradual decrease in response to therapy. These changes were significantly associated with SDF-1 plasma levels. Correlations of VSEL and HSC were also reported in reference to growth-related parameters, and IGF-1 and IGFBP3 values. Noteworthy, rhIGF-1 was shown to efficiently induce development of Laron patients achieving at least proper rate of growth (compared to healthy group) in 80% of subjects. In conclusion, here we provided novel insight into stem cells participation in IGF-1 deficiency in patients. Thus, we demonstrated basis for future studies in context of stem cells and IGF-1 role in growth disturbances.

An Insulin-like Growth Factor-1 Conjugated Bombyx mori Silk Fibroin Film for Diabetic Wound Healing: Fabrication, Physicochemical Property Characterization, and Dosage Optimization In Vitro and In Vivo

This study aimed to develop a silk fibroin (SF)-film for the treatment of chronic diabetic wounds. Silk fibroin was purified through a newly developed heating degumming (HD) process and casted on a hydrophobic surface to form SF-films. The process allowed the fabricated film to achieve a 42% increase in transparency and a 32% higher proliferation rate for BALB/3T3 fibroblasts compared to that obtained by conventional alkaline degumming treatment. Fourier transform infrared analysis demonstrated that secondary structure was retained in both HD- and alkaline degumming-derived SF preparations, although the crystallinity of beta-sheet in SF-film after the HD processing was slightly increased. This study also investigated whether conjugating insulin-like growth factor-1 (IGF-1) would promote diabetic wound healing and what the optimal dosage is. Using BALB/3T3 cells grown in hyperglycemic medium as a model, it was demonstrated that the optimal IGF-1 dosage to promote the cell growth was approximately 0.65 pmol. Further analysis of wound healing in a diabetic mouse model indicated that SF-film loaded with 3.25 pmol of IGF-1 showed significantly superior wound closure, a 13% increase at the 13th day after treatment relative to treatment with 65 pmol of free IGF-1. Improvement in diabetic wound healing was exerted synergistically by SF-film and IGF-1, as reflected by parameters including levels of re-epithelialization, epithelial tissue area, and angiogenesis. Finally, IGF-1 increased the epithelial tissue area and micro-vessel formation in a dose-dependent manner in a low dosage range (3.25 pmol) when loaded to SF-films. Together, these results strongly suggest that SF-film produced using HD and loaded with a low dosage of IGF-1 is a promising dressing for diabetic wound therapy.

Sustained Release of Insulin-Like Growth Factor-1 from Bombyx mori L. Silk Fibroin Delivery for Diabetic Wound Therapy

The goals of this study are to develop a high purity patented silk fibroin (SF) film and test its suitability to be used as a slow-release delivery for insulin-like growth factor-1 (IGF-1). The release rate of the SF film delivering IGF-1 followed zero-order kinetics as determined via the Ritger and Peppas equation. The release rate constant was identified as 0.11, 0.23, and 0.09% h^-1 at 37 °C for SF films loaded with 0.65, 6.5, and 65 pmol IGF-1, respectively. More importantly, the IGF-1 activity was preserved for more than 30 days when complexed with the SF film. We show that the IGF-1-loaded SF films significantly accelerated wound healing in vitro (BALB/3T3) and in vivo (diabetic mice), compared with wounds treated with free IGF-1 and an IGF-1-loaded hydrocolloid dressing. This was evidenced by a six-fold increase in the granulation tissue area in the IGF-1-loaded SF film treatment group compared to that of the PBS control group. Western blotting analysis also demonstrated that IGF-1 receptor (IGF1R) phosphorylation in diabetic wounds increased more significantly in the IGF-1-loaded SF films group than in other experimental groups. Our results suggest that IGF-1 sustained release from SF films promotes wound healing through continuously activating the IGF1R pathway, leading to the enhancement of both wound re-epithelialization and granulation tissue formation in diabetic mice. Collectively, these data indicate that SF films have considerable potential to be used as a wound dressing material for long-term IGF-1 delivery for diabetic wound therapy.

A rationale for the treatment of short stature in children with the combination of recombinant human growth hormone (rhGH) and recombinant human insulin-like growth factor-I (rhIGF-I)

Both rhGH and rhIGF-I are signaling molecules with the capacity to restore the rate of growth in certain subsets of slowly growing children. In some instances, heights attained at or near the time of cessation of linear growth are indistinguishable from the height distribution of the community as a whole or from the height distribution expected based on the heights of biological parents. The GH: IGF-I signaling system is sequential, forming a continuous loop wherein GH will stimulate production of IGF-I and IGF-I will inhibit production of GH. This feature suggests that a deficiency of GH will be accompanied by a deficiency of IGF-I and that treatment of GH deficiency with rhGH will restore IGF-I and the subnormal growth of combined GH: IGF-I deficiency. Although logical, this proposition is not always true. rhGH and rhIGF-I are distinct polypeptides, with distinct cell surface receptors and distinct intracellular signaling pathways both capable of amplifying distinct, yet overlapping, patterns of gene replication, protein synthesis and metabolic activities. These features suggest that neither treatment with rhGH nor rhIGF-I alone will invariably recapitulate the combined activities of the GH: IGF-I system, At the present time, this proposition appears both logical and true. The possibility that combined rhGH and rhIGF-I treatment can accomplish that which neither monotherapy can has been examined in gene knock-out experiments in animals and direct comparisons of GH, IGF-I and combined GH: IGF- treatments in animals and in children with short stature, normal GH and low IGF-I (primary IGF-I deficiency). In these experimental models, the growth rates with combined rhGH and rhIGF-I treatment exceed those of either monotherapy. The extent to which this proposition can be generalized to various short stature populations remains to be determined.

Homozygous receptors for insulin and not IGF-1 accelerate intimal hyperplasia in insulin resistance and diabetes

Insulin and IGF-1 actions in vascular smooth muscle cells (VSMC) are associated with accelerated arterial intima hyperplasia and restenosis after angioplasty, especially in diabetes. To distinguish their relative roles, we delete insulin receptor (SMIRKO) or IGF-1 receptor (SMIGF1RKO) in VSMC and in mice. Here we report that intima hyperplasia is attenuated in SMIRKO mice, but not in SMIGF1RKO mice. In VSMC, deleting IGF1R increases homodimers of IR, enhances insulin binding, stimulates p-Akt and proliferation, but deleting IR decreases responses to insulin and IGF-1. Studies using chimeras of IR(extracellular domain)/IGF1R(intracellular-domain) or IGF1R(extracellular domain)/IR(intracellular-domain) demonstrate homodimer IRα enhances insulin binding and signaling which is inhibited by IGF1Rα. RNA-seq identifies hyaluronan synthase2 as a target of homo-IR, with its expression increases by IR activation in SMIGF1RKO mice and decreases in SMIRKO mice. Enhanced intima hyperplasia in diabetes is mainly due to insulin signaling via homo-IR, associated with increased Has2 expression.

Dual growth factor-immobilized bioactive injection material for enhanced treatment of glottal insufficiency

With increasing demand for treatment of glottal insufficiency, several injection materials have been examined. However, biological resorption, degradation of injected materials, and the subsequent need to perform multiple injections still remain major clinical problems. In this study, we fabricated two different growth factor (GF) [single basic fibroblast growth factor (bFGF), single hepatocyte growth factor (HGF), or dual bFGF/HGF]-immobilized polycaprolactone (PCL)/Pluronic F127 microspheres. These materials were investigated for their potential use as bioactive injection laryngoplasty agents. HGF was found to be continuously released over 20 days and the bFGF was found to be continuously released over 25 days, as demonstrated by ELISA assay. Human vocal fold fibroblasts (hVFFs) showed significantly higher proliferative ability on dual GF-immobilized microspheres. GF-immobilized microspheres (bFGF, HGF, and dual GF) were injected into paralyzed vocal folds of New Zealand white rabbits. Through endoscopic observation and H&E staining, we identified that the microspheres remained localized at the injection site, resulting in constant volume augmentation of the paralyzed vocal fold without significant loss of the initial volume after 4 weeks. The expression of genes related to the extracellular matrix (ECM) in the vocal fold was upregulated by dual GF-immobilized microspheres. Furthermore, dual GF-immobilized microspheres inhibited muscle degeneration and upregulation of myogenic-related genes. In conclusion, dual GF-immobilized microspheres passively augmented the volume of the paralyzed vocal fold while actively inducing ECM synthesis at the injected vocal fold and preserving muscle tissue. Dual GF-immobilized microspheres could be a new and promising injection material for paralyzed vocal folds. STATEMENT OF SIGNIFICANCE: Limitation of prolonged augmentation of vocal fold and degeneration of vocal fold tissue still remain as major clinical problems in the treatment of vocal fold paralysis. Herein, we fabricated the polycaprolactone (PCL)/Pluronic F127 microspheres to augment volume of paralyzed vocal folds. On top of that, we additionally immobilized the growth factors (bFGF, HGF, or dual bFGF/HGF) on the surface of these microspheres. We highlight the efficacy of the dual GF-immobilized microspheres which augmented the volume of the paralyzed vocal fold passively, induced ECM synthesis actively at the injected vocal fold and preserved laryngeal muscle tissue. Our results suggest that the dual GF-immobilized microsphere could be a new promising injection material for injection laryngoplasty to treat paralyzed vocal fold.

Insulin-like growth factor 1 promotes cochlear synapse regeneration after excitotoxic trauma in vitro

In the context of acquired sensorineural hearing loss (SNHL), cochlear hair cells have long been thought to be among the most vulnerable elements in mammalian cochleae. However, recent studies have indicated that the synaptic connection between inner hair cells (IHC) and spiral ganglion neurons (SGN) can be an important target for the treatment of SNHL. Our previous studies in patients with sudden SNHL demonstrated delayed and gradual hearing recovery following topical application of insulin-like growth factor 1 (IGF-1), suggesting that not only protective but also regenerative mechanisms may account for hearing recovery after treatment with IGF-1. We then hypothesized that IGF-1 has the potential to drive the regeneration of IHC-SGN synapses. To test this hypothesis, we investigated the effects of IGF-1 on IHC-SGN synapses using cochlear explant cultures from postnatal day 2 mice that had been damaged by exposure to the excitatory amino acids N-methyl-d-aspartate and kainate. Cochlear explants that lost IHC-SGN synapses upon exposure to excitatory amino acids were cultured with exogenous IGF-1 for an additional 48 h. We observed increased numbers of IHC-SGN synapses after exogenous IGF-1 application. Pharmacological inhibition of the IGF-1 receptor attenuated the restoration of IHC-SGN synapses by exogenous IGF-1. These findings indicated that IGF-1 induces regeneration of IHC-SGN synapses in cochlear explant cultures from postnatal day 2 mice. Therefore, in a future study we will perform in vivo experiments using adult mice to ascertain the effects of IGF-1 on the regeneration of IHC-SGN synapses.

Analysis of the IGF-system in milk from farm animals - Occurrence, regulation, and biomarker potential

IGFs and IGF-binding proteins (IGFBPs) are abundantly present in milk and in dairy products. Compared to the IGFs, the IGFBP have received less attention in milk, although truncated IGFBPs and IGFBP-glycosylation have been described in milk. Thereby, complex control of local IGF-effects can be assumed on the levels of IGFBPs, proteases, and protease inhibitors. The present review collects the current knowledge both on presence and regulation of IGFs and IGFBPs in milk particularly from dairy animal species. As a rule higher levels of IGF-I, IGF-II, and IGFBPs are measured around parturition if compared to later time-points of lactation. In all farm animal species included in this review, it is found that the relative abundancies of IGFBPs in milk and serum are similar, with IGFBP-3 and -2 characterized by higher concentrations if compared to IGFBP-4 or -5. The concentrations of IGFs and IGFBPs in milk or dairy products can be altered by hormones, dairy processing, or fermentation. Because milk can be used for non-invasive biomarker research, quality management, and health monitoring, we discuss novel directions of IGF-analysis and potential on-site biomarker research in milk.