Lower serum insulin-like growth factor 2 level in patients with bipolar disorder is associated with the severity of manic symptoms during manic episodes

Objective

Accumulating evidence has indicated that neurodevelopmental defects may underlie the pathophysiology of bipolar disorder (BD). Insulin-like growth factors (IGFs) are a family of neurotrophic factors that are essential for the survival and development of neurons. The present study aims to investigate whether IGF-2 signaling is implicated in the pathophysiological processes of BD.

Method

50 healthy controls and 78 patients with BD, including 23 patients who diagnosed acute depressive episode and 55 patients who diagnosed acute manic episode, were recruited in this study. The 17-item Hamilton Depression Rating Scale (HAMD-17) and the Young Mania Rating Scale (YMRS) were used to assess the severity of the depressive and manic symptoms, respectively. The serum IGF-2 level was determined by an enzyme-linked immunosorbent assay (ELISA). The Kolmogorov-Smirnov and Mann-Whitney U tests were used for between-group comparisons and spearman analysis was used to analyze correlations.

Results

Patients with BD had lower serum IGF-2 levels (66.08 ± 21.22 ng/ml) when compared to healthy controls (88.72 ± 31.55 ng/ml). BD patients were divided into manic episode and depressive episode subgroups. We found that serum IGF-2 levels were reduced in both the mania and depression subgroups (mania: 67.19 ± 21.52 ng/ml, depression: 63.43 ± 20.67 ng/ml; P < 0.001), while no significant difference was observed between two groups (P > 0.05). Spearman correlation analyses revealed that the levels of serum IGF-2 were negatively correlated with the YMRS scores in BD patients (r = -0.522, P < 0.001). Furthermore, IGF-2 was found to be an independent contributor to the severity of symptoms in patients with manic episodes (B = -0.610, t = -5.299, P < 0.001).

Conclusion

Lower serum IGF-2 levels were found in BD patients and correlated with the severity of the manic symptoms in these patients during manic episodes. These results suggest that reduced IGF-2 levels might be involved in the pathophysiology of BD, and serum IGF-2 could be a peripheral biomarker for the evaluation of the severity of manic symptoms in BD patients.

A systematic review of literature on Insulin-like growth factor-2-mediated hypoglycaemia in non-islet cell tumours

INTRODUCTION

Insulin-like growth factor-2 (IGF-2)-mediated hypoglycemia is a rare yet clinically significant entity with considerable morbidity and mortality. Existing literature is limited and fails to offer a comprehensive understanding of its clinical trajectory, management and prognostication.

METHODS

Systematic review of English-language articles reporting primary patient data on IMH was searched using electronic databases (PubMed, Scopus and Embase) from any date up to 21 December 2022. Data were analysed in STATA-16.

RESULTS

The systematic review contains 172 studies, including 1 Randomised controlled trial, 1 prospective observational study, 5 retrospective observational studies, 150 case reports, 11 case series and 4 conference abstracts. A total of 233 patients were analysed, averaging 60.6 ± 17.1 years in age, with comparable proportions of males and females. The commonest tumours associated with Insulin-like Growth Factor-2-mediated hypoglycaemia were fibrous tumours (N = 124, 53.2%), followed by non-fibrous tumours originating from the liver (N = 21, 9%), hemangiopericytomas (N = 20, 8.5%) and mesotheliomas (N = 11, 4.7%). Hypoglycaemia was the presenting feature of NICT in 42% of cases. Predominant clinical features included loss of consciousness (26.7%) and confusion (21%). The mean IGF-2 and IGF-1 levels were 882.3 ± 630.6 ng/dL and 41.8 ± 47.8, respectively, with no significant correlation between these levels and patient outcomes. Surgical removal was the most employed treatment modality (47.2%), followed by medication therapy. The recovery rate was 77%, with chronic liver disease (CLD) significantly associated with a poor outcome (OR: 7.23, P: 0.03). Tumours originating from fibrous tissues were significantly associated with recovery (p < .001). In the logistic regression model, CLD remained a significant predictor of poor outcomes.

CONCLUSION

This systematic review highlights that most non-islet-cell tumour-hypoglycaemia (NICTH) is due to fibrous tumours. NICTs demonstrate a variable prognosis, which is fair if originating from fibrous tissue. Management such as octreotide, corticosteroids, diazoxide, embolization, radiotherapy and surgical resection have disparate success rates.

Neuroprotective effects of insulin-like growth factor-2 in 6-hydroxydopamine-induced cellular and mouse models of Parkinson's disease

Skin-derived precursor Schwann cells have been reported to play a protective role in the central nervous system. The neuroprotective effects of skin-derived precursor Schwann cells may be attributable to the release of growth factors that nourish host cells. In this study, we first established a cellular model of Parkinson's disease using 6-hydroxydopamine. When SH-SY5Y cells were pretreated with conditioned medium from skin-derived precursor Schwann cells, their activity was greatly increased. The addition of insulin-like growth factor-2 neutralizing antibody markedly attenuated the neuroprotective effects of skin-derived precursor Schwann cells. We also found that insulin-like growth factor-2 levels in the peripheral blood were greatly increased in patients with Parkinson's disease and in a mouse model of Parkinson's disease. Next, we pretreated cell models of Parkinson's disease with insulin-like growth factor-2 and administered insulin-like growth factor-2 intranasally to a mouse model of Parkinson's disease induced by 6-hydroxydopamine and found that the level of tyrosine hydroxylase, a marker of dopamine neurons, was markedly restored, α-synuclein aggregation decreased, and insulin-like growth factor-2 receptor down-regulation was alleviated. Finally, in vitro experiments showed that insulin-like growth factor-2 activated the phosphatidylinositol 3 kinase (PI3K)/AKT pathway. These findings suggest that the neuroprotective effects of skin-derived precursor Schwann cells on the central nervous system were achieved through insulin-like growth factor-2, and that insulin-like growth factor-2 may play a neuroprotective role through the insulin-like growth factor-2 receptor/PI3K/AKT pathway. Therefore, insulin-like growth factor-2 may be an useful target for Parkinson's disease treatment.

Severe Hypoglycemia Caused by a Giant Borderline Phyllodes Tumor of the Breast: A Case Report and Literature Review

A case of hypoglycemic coma caused by a giant borderline phyllodes tumor of the breast has been described. The patient, a 63-year-old woman, was admitted with recurrent unconsciousness. She had a giant breast tumor with decreased blood glucose, insulin, and C-peptide. The patient's hypoglycemia resolved rapidly after resection of the breast tumor. Pathological examination indicated a borderline phyllodes tumor of the breast, and immunohistochemistry suggested high expression of insulin-like growth factor-2 (IGF-2) in the tumor tissue. A literature review is also included to summarize the clinical characteristics of such patients and to serve as a unique resource for clinical diagnosis and treatment of similar cases.

Insulin-like growth factor-2 regulates basal retinal insulin receptor activity

The retinal insulin receptor (IR) exhibits basal kinase activity equivalent to that of the liver of fed animals, but unlike the liver, does not fluctuate with feeding and fasting; it also declines rapidly after the onset of insulin-deficient diabetes. The ligand(s) that determine basal IR activity in the retina has not been identified. Using a highly sensitive insulin assay, we found that retinal insulin concentrations remain constant in fed versus fasted rats and in diabetic versus control rats; vitreous fluid insulin levels were undetectable. Neutralizing antibodies against insulin-like growth factor 2 (IGF-2), but not insulin-like growth factor 1 (IGF-1) or insulin, decreased IR kinase activity in normal rat retinas, and depletion of IGF-2 from serum specifically reduced IR phosphorylation in retinal cells. Immunoprecipitation studies demonstrated that IGF-2 induced greater phosphorylation of the retinal IR than the IGF-1 receptor. Retinal IGF-2 mRNA content was 10-fold higher in adults than pups and orders of magnitude higher than in liver. Diabetes reduced retinal IGF-2, but not IGF-1 or IR, mRNA levels, and reduced IGF-2 and IGF-1 content in vitreous fluid. Finally, intravitreal administration of IGF-2 (mature and pro-forms) increased retinal IR and Akt kinase activity in diabetic rats. Collectively, these data reveal that IGF-2 is the primary ligand that defines basal retinal IR activity and suggest that reduced ocular IGF-2 may contribute to reduced IR activity in response to diabetes. These findings may have importance for understanding the regulation of metabolic and prosurvival signaling in the retina.

Plasma concentration and uterine and ovarian expressions of insulin-like growth factor-2 in dogs with cystic endometrial hyperplasia-pyometra

The objective of this study was to investigate the plasma concentrations of insulin-like growth factor-2 (IGF-2) as well as its expression in the uterus and ovary of healthy dogs and those with cystic endometrial hyperplasia (CEH)-pyometra complex. Group 1 (n = 10) included bitches with open cervix pyometra, while Group 2 (n = 7) consisted of clinically healthy bitches in dioestrus. The number of IGF-2 immunopositive interstitial cells was significantly higher in Group 1, whereas in Group 2 there were only two cases in which a few cells were IGF-2 immunopositive. IGF-2 immunopositivity was observed in the endometrial glandular epithelium in both groups. Additionally, interstitial fibroblasts and macrophages in the endometrium were also positive in Group 1. The concentration of plasma IGF-2 was higher in Group 1 than in Group 2 (P < 0.05). The concentration was positively correlated with IGF-2 expression in the endometrial glands (r = 0.926; P < 0.001) in Group 1. However, a negative correlation was present between plasma IGF-2 concentration and IGF-2 expression in the interstitial endocrine cells of the ovary in Group 1 (r = -0.652; P < 0.05). The results suggest that IGF-2 plays an important role during the inflammatory process occurring in bitches with CEH-pyometra complex as well as in the endometrium of healthy bitches in dioestrus.

Novel peptide derived from IGF-2 displays anti-angiogenic activity in vitro and inhibits retinal angiogenesis in a model of oxygen-induced retinopathy

BACKGROUND

Retinopathy of prematurity (ROP), a major cause of significant visual morbidity and blindness in preterm infants, is closely related to pathological angiogenesis. The aim of the study is to evaluate the effect of a new 12-aa peptide (named peptide CW-703) from human insulin-like growth factor-2, against angiogenesis in ROP.

METHODS

In order to evaluate the inhibitory effect of CW-703 on the proliferation, migration, tube formation and apoptosis of human umbilical vein endothelial cells (ScienCell) in vitro, we used MTS assays, a modified Boyden chamber, Matrigel system and TUNEL assays. Effects in vivo were assayed using chorioallantoic membrane assays and oxygen-induced retinopathy (OIR) models in mice. We also performed eletrophysiological and histologic examinations to evaluate the possible toxicity of the peptide. Real-time PCR, ELISA and western blotting were used to elucidate the mechanism of CW-703.

RESULTS

CW-703 inhibited angiogenesis in vitro by suppressing endothelial cell proliferation, migration and tube formation. CW-703 also prevented angiogenesis in chicken chorioallantoic membrane assays and OIR assays in mice. No evident functional or morphologic abnormalities in neuroretina after CW-703 injection were revealed in electrophysiological tests and histological examinations. Moreover, we elucidated that CW-703 competed for binding to IGF-1R and inhibited angiogenesis by inhibiting IGF-1R/PI3K/AKT activation and downregulating vascular endothelial growth factor expression.

CONCLUSION

The novel peptide CW-703 may act as an effective inhibitor of ocular pathologic angiogenesis, especially in treating ROP.

Changes of Serum Insulin-like Growth Factor-2 Response to Negative Symptom Improvements in Schizophrenia Patients Treated with Atypical Antipsychotics

Accumulating evidence suggests that a disruption of early brain development, in which insulin-like growth factor-2 (IGF-2) has a crucial role, may underlie the pathophysiology of schizophrenia. Our previous study has shown that decreased serum IGF-2 was correlated with the severity of psychopathology in patients with schizophrenia. Here we conducted a prospective observation trial to investigate the effects of atypical antipsychotics on serum IGF-2 level and its relationship with clinical improvements in schizophrenia patients. Thirty-one schizophrenia patients with acute exacerbation and 30 healthy individuals were recruited in this study. Psychiatric symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS) and serum IGF-2 levels were determined using ELISA. We found that schizophrenia patients with acute exacerbation had lower serum IGF-2 levels than control individuals at baseline (P<0.05). After 2 months of atypical antipsychotic treatment, a significant improvement in each PANSS subscore and total score was observed in patients (all P<0.01), and the serum IGF-2 levels of patients were significantly increased compared with those at baseline (203.13±64.62 vs. 426.99±124.26 ng/mL; t =-5.044, P<0.001). Correlation analysis revealed that the changes of serum IGF-2 levels in patients were significantly correlated with the improvements of negative symptoms (r=-0.522, P=0.006). Collectively, our findings demonstrated changes of serum IGF-2 response to improvements of negative symptoms in schizophrenia patients treated with atypical antipsychotics, suggesting that serum IGF-2 might be a treatment biomarker for schizophrenia.

DDR1 regulates thyroid cancer cell differentiation via IGF-2/IR-A autocrine signaling loop

Patients with thyroid cancers refractory to radioiodine (RAI) treatment show a limited response to various therapeutic options and a low survival rate. The recent use of multikinase inhibitors has also met limited success. An alternative approach relies on drugs that induce cell differentiation, as the ensuing increased expression of the cotransporter for sodium and iodine (NIS) may partially restore sensitivity to radioiodine. The inhibition of the ERK1/2 pathway has shown some efficacy in this context. Aggressive thyroid tumors overexpress the isoform-A of the insulin receptor (IR-A) and its ligand IGF-2; this IGF-2/IR-A loop is associated with de-differentiation and stem-like phenotype, resembling RAI-refractory tumors. Importantly, IR-A has been shown to be positively modulated by the non-integrin collagen receptor DDR1 in human breast cancer. Using undifferentiated human thyroid cancer cells, we now evaluated the effects of DDR1 on IGF-2/IR-A loop and on markers of cell differentiation and stemness. DDR1 silencing or downregulation caused significant reduction of IR-A and IGF-2 expression, and concomitant increased levels of differentiation markers (NIS, Tg, TSH, TPO). Conversely, markers of epithelial-to-mesenchymal transition (Vimentin, Snail-2, Zeb1, Zeb2 and N-Cadherin) and stemness (OCT-4, SOX-2, ABCG2 and Nanog) decreased. These effects were collagen independent. In contrast, overexpression of either DDR1 or its kinase-inactive variant K618A DDR1-induced changes suggestive of less differentiated and stem-like phenotype. Collagen stimulation was uneffective. In conclusion, in poorly differentiated thyroid cancer, DDR1 silencing or downregulation blocks the IGF-2/IR-A autocrine loop and induces cellular differentiation. These results may open novel therapeutic approaches for thyroid cancer.

Insulin receptor in the brain: Mechanisms of activation and the role in the CNS pathology and treatment

While the insulin receptor (IR) was found in the CNS decades ago, the brain was long considered to be an insulin-insensitive organ. This view is currently revisited, given emerging evidence of critical roles of IR-mediated signaling in development, neuroprotection, metabolism, and plasticity in the brain. These diverse cellular and physiological IR activities are distinct from metabolic IR functions in peripheral tissues, thus highlighting region specificity of IR properties. This particularly concerns the fact that two IR isoforms, A and B, are predominantly expressed in either the brain or peripheral tissues, respectively, and neurons express exclusively IR-A. Intriguingly, in comparison with IR-B, IR-A displays high binding affinity and is also activated by low concentrations of insulin-like growth factor-2 (IGF-2), a regulator of neuronal plasticity, whose dysregulation is associated with neuropathologic processes. Deficiencies in IR activation, insulin availability, and downstream IR-related mechanisms may result in aberrant IR-mediated functions and, subsequently, a broad range of brain disorders, including neurodevelopmental syndromes, neoplasms, neurodegenerative conditions, and depression. Here, we discuss findings on the brain-specific features of IR-mediated signaling with focus on mechanisms of primary receptor activation and their roles in the neuropathology. We aimed to uncover the remaining gaps in current knowledge on IR physiology and highlight new therapies targeting IR, such as IR sensitizers.

A novel functional crosstalk between DDR1 and the IGF axis and its relevance for breast cancer

In the last decades increasing importance has been attributed to the Insulin/Insulin-like Growth Factor signaling (IIGFs) in cancer development, progression and resistance to therapy. In fact, IIGFs is often deregulated in cancer. In particular, the mitogenic insulin receptor isoform A (IR-A) and the insulin-like growth factor receptor (IGF-1R) are frequently overexpressed in cancer together with their cognate ligands IGF-1 and IGF-2. Recently, we identified discoidin domain receptor 1 (DDR1) as a new IR-A interacting protein. DDR1, a non-integrin collagen tyrosine kinase receptor, is overexpressed in several malignancies and plays a role in cancer progression and metastasis. Herein, we review recent findings indicating that DDR1 is as a novel modulator of IR and IGF-1R expression and function. DDR1 functionally interacts with IR and IGF-1R and enhances the biological actions of insulin, IGF-1 and IGF-2. Conversely, DDR1 is upregulated by IGF-1, IGF-2 and insulin through the PI3K/AKT/miR-199a-5p circuit. Furthermore, we discuss the role of the non-canonical estrogen receptor GPER1 in the DDR1-IIGFs crosstalk. These data suggest a wider role of DDR1 as a regulator of cell response to hormones, growth factors, and signals coming from the extracellular matrix.

Receptors for Insulin-Like Growth Factor-2 and Androgens as Therapeutic Targets in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) occurs in 10-15% of all breast cancer patients, yet it accounts for about half of all breast cancer deaths. There is an urgent need to identify new antitumor targets to provide additional treatment options for patients afflicted with this aggressive disease. Preclinical evidence suggests a critical role for insulin-like growth factor-2 (IGF2) and androgen receptor (AR) in regulating TNBC progression. To advance this work, a panel of TNBC cell lines was investigated with all cell lines showing significant expression of IGF2. Treatment with IGF2 stimulated cell proliferation in vitro (p < 0.05). Importantly, combination treatments with IGF1R inhibitors BMS-754807 and NVP-AEW541 elicited significant inhibition of TNBC cell proliferation (p < 0.001). Based on Annexin-V binding assays, BMS-754807, NVP-AEW541 and enzalutamide induced TNBC cell death (p < 0.005). Additionally, combination of enzalutamide with BMS-754807 or NVP-AEW541 exerted significant reductions in TNBC proliferation even in cells with low AR expression (p < 0.001). Notably, NVP-AEW541 and BMS-754807 reduced AR levels in BT549 TNBC cells. These results provide evidence that IGF2 promotes TNBC cell viability and proliferation, while inhibition of IGF1R/IR and AR pathways contribute to blockade of TNBC proliferation and promotion of apoptosis in vitro.

Clinicopathological significance and impact on outcomes of the gene expression levels of IGF-1, IGF-2 and IGF-1R, IGFBP-3 in patients with colorectal cancer: Overexpression of the IGFBP-3 gene is an effective predictor of outcomes in patients with colorectal cancer

The insulin-like growth factors (IGF) system is involved in tumor proliferation, invasion and metastasis in cancer. The current study investigated the association of IGF-1, IGF-2 and IGF-1 receptor (IGF-1R), IGF binding proteins type 3 (IGFBP-3) mRNA expression levels with clinicopathological characteristics and outcomes of 202 patients with untreated colorectal cancer (CRC). IGF-1, IGF-2, IGF-1R and IGFBP-3 mRNA expression levels were analyzed in surgical specimens of cancer tissues and adjacent normal mucosa cells using reverse transcription-quantitative polymerase chain reaction. The IGF-1R gene expression level was significantly higher in cancer tissue compared with adjacent normal mucosa. By contrast, IGF-1 gene expression levels were reduced in cancer tissue compared with normal mucosa. IGF-2 and IGFBP-3 gene expression levels did not differ significantly between cancer tissue and adjacent normal mucosa. As for the association of gene expression and clinicopathological characteristics, IGFBP-3 gene expression was significantly associated with lymph node metastasis. High IGFBP-3 gene expression was associated with poor 5-year overall survival compared with patients with low IGFBP-3 expression. Furthermore, IGFBP-3 gene expression was identified as an independent prognostic factor using multivariate analysis. Overexpression of the IGFBP-3 gene is considered an effective independent predictor of outcomes in patients with CRC.

Serum IGFBP4 concentration decreased in dairy heifers towards day 18 of pregnancy

This study was conducted to determine if the main components of the somatotropic axis change during the early phase of pregnancy in the maternal blood system and whether differences exist on day 18 after pregnancy recognition by the maternal organism. Blood samples of pregnant heifers (Holstein Friesian; n = 10 after embryo transfer) were obtained on the day of ovulation (day 0), as well as on days 7, 14, 16 and 18 and during pregnant, non-pregnant and negative control cycles. The oncentrations of progesterone (P₄), oestrogen, growth hormone (GH), insulin-like growth factor-1 and -2 (IGF1, -2) and IGF-binding protein-2, -3 and -4 (IGFBP2, -3, -4) were measured. The mRNA expressions of growth hormone receptor 1A, IGF1, IGF2, IGFBP2, IGFBP3 and IGFBP4 were detected using RT-qPCR in liver biopsy specimens (day 18). In all groups, total serum IGF1 decreased from day 0 to 16. Notably, IGFBP4 maternal blood concentrations were lower during pregnancy than during non-pregnant cycles and synchronized control cycles. It can be speculated that the lower IGFBP4 in maternal blood may result in an increase of free IGF1 for local action. Further studies regarding IGFBP4 concentration and healthy early pregnancy are warranted.

Insulin-Like Growth Factor-2 Is Induced Following 5-Aminolevulinic Acid-Mediated Photodynamic Therapy in SW620 Human Colon Cancer Cell Line

The IGF system is a family of polypeptide growth factors, which plays a significant role in the development and growth of many cells. Dysregulation of insulin-like growth factors and their pathway components has been connected with essential tumor properties, such as tumor cell proliferation, antiapoptotic properties, invasive behavior and chemotherapy resistance. However, the effects of photodynamic therapy (PDT), one of the cancer treatment methods for the regulation of the IGF signaling pathway, are still unclear. The aim of this study was to investigate the expression of IGF-2 after 5-aminolevulinic acid (5-ALA)-mediated-PDT in SW620 human colorectal cancer cells with evaluation of cell proliferation and apoptosis and to determine the effects of PDT on the IGF-2 receptor (IGF-2R), IGF-2 binding protein-1 (IGF-2BP-1) and the proapoptotic protein, BAX. Cells were treated with 5-aminolevulinic acid and its methyl ester. Changes of the expression and concentration of IGF-2 before and after treatment were assayed by immunocytochemistry, Western blot and ELISA. We found that IGF-2 was significantly overexpressed in the SW620 cell line, while its receptor and binding protein-1 were not significantly changed. Within this study, we would like to suggest that IGF-2 contributes to the effects of PDT and that its expression will influence post-PDT efficacy.

A mRNA and cognate microRNAs localize in the nucleolus

We previously discovered that a set of 5 microRNAs are concentrated in the nucleolus of rat myoblasts. We now report that several mRNAs are also localized in the nucleoli of these cells as determined by microarray analysis of RNA from purified nucleoli. Among the most abundant of these nucleolus-localized mRNAs is that encoding insulin-like growth factor 2 (IGF2), a regulator of myoblast proliferation and differentiation. The presence of IGF2 mRNA in nucleoli was confirmed by fluorescence in situ hybridization, and RT-PCR experiments demonstrated that these nucleolar transcripts are spliced, thus arriving from the nucleoplasm. Bioinformatics analysis predicted canonically structured, highly thermodynamically stable interactions between IGF2 mRNA and all 5 of the nucleolus-localized microRNAs. These results raise the possibility that the nucleolus is a staging site for setting up particular mRNA-microRNA interactions prior to export to the cytoplasm.

Effects of insulin-like growth factor 2 and its receptor expressions on corneal repair

Limbal stem cell (LSC) on the basal layer of cornea plays an important role in the epithelial repair after corneal injury as it can proliferate, differentiate and migrate into injury sites under the direction of cytokines. This study explored the signaling pathway and cellular mechanism between corneal epithelial cells LSC, on a mouse model with mechanic corneal injury. Ipsilateral corneal mechanic injury model was prepared on mice using the contralateral eye as the control. Tissues from both central and peripheral regions of cornea were collected, cultured and quantified for expression of various cytokines including epidermal growth factor (EGF), fibroblast growth factor-β (FGF-β), heparin-like growth factor (HGF), keratinocyte growth factor (KGF), transforming growth factor-β1 (TGF-β1), IGF-1 and IGF-2. The effects of these factors on the differentiation of LSC and fibroblasts were also studied. Most of those cytokines had elevated gene expressions after the corneal injury. Among those IGF-2 had significantly increased expression, along with the high expression of IGF-2 receptor in corneal peripheral cells. IGF-2 also induced the differentiation of LSC into keratin-12-positive cells. Further studies showed the prominent expression of α-actin in injured tissues, suggesting the potential transformation of fibroblasts into myofibroblasts. Both IGF-2 and its receptor had elevated expressions after corneal injury. They may facilitate the transformation of LSC into epithelial cells, in addition to the role in transformation from fibroblasts to myofibroblasts.

IGF-2 is necessary for retinoblastoma-mediated enhanced adaptation after small-bowel resection

Previously, we have demonstrated that genetically disrupting retinoblastoma protein (Rb) expression in enterocytes results in taller villi, mimicking resection-induced adaption responses. Rb deficiency also results in elevated insulin-like growth factor-2 (IGF-2) expression in villus enterocytes. We propose that postoperative disruption of Rb results in enhanced adaptation which is driven by IGF-2. Inducible, intestine-specific Rb-null mice (iRbIKO) and wild-type (WT) littermates underwent a 50% proximal small-bowel resection (SBR) at 7-9 weeks of age. They were then given tamoxifen on postoperative days (PODs) 4-6 and harvested on POD 28. The experiment was then repeated on double knockouts of both IGF-2 and Rb (IGF-2 null/iRbIKO). iRbIKO mice demonstrated enhanced resection-induced adaptive villus growth after SBR and increased IGF-2 messenger RNA (mRNA) in ileal villus enterocytes compared to their WT littermates. In the IGF-2 null/iRbIKO double-knockout mice, there was no additional villus growth beyond what was expected of normal resection-induced adaptation. Adult mice in which Rb is inducibly deleted from the intestinal epithelium following SBR have augmented adaptive growth. IGF-2 expression is necessary for enhanced adaptation associated with acute intestinal Rb deficiency.

Focal overexpression of insulin-like growth factor 2 by hepatocytes and cholangiocytes in viral liver cirrhosis

Insulin-like growth factor (IGF)-2 is overexpressed in hepatocellular carcinoma and accompanying dysplastic lesions. IGF-2 signalling is mediated through IGF-1 receptor (IGF-1R), while mannose 6-phosphate/insulin-like growth factor-2 receptor (M6P/IGF-2R) controls pericellular levels of free IGF-2. We studied, by in situ hybridisation and immunohistology, 18 liver specimens with cirrhosis of different aetiology without neoplastic or dysplastic lesions. Immunohistology was also performed for insulin receptor IGF-1R and IGF-binding proteins 3 and 4. High focal levels of IGF-2 RNA were found in some hepatocytes of all livers with HBV- or HCV-induced cirrhosis (n=10), but in only one of the cirrhoses with nonviral aetiology (n=8). IGF-2 was overexpressed in biliary duct epithelial cells in one case. Compared with noncirrhotic liver, all cirrhotic specimens showed reduced hepatocellular expression of M6P/IGF-2R protein, which contrasted with enhanced expression in perisinusoidal cells. Immunostaining for the other antigens did not reveal significant differences. Upregulation of IGF-2 in some hepatocytes may lead to high focal IGF-2 levels sufficient to saturate local IGF-2 binding capacities, and may result in an increased susceptibility to cellular dedifferentiation and, ultimately, liver cancer. Downregulation of hepatocellular M6P/IGF-2R and upregulation of IGF-2 seem to be early events in hepatocarcinogenesis prior to the appearance of morphologically distinct dysplastic lesions. Elevated focal IGF-2 transcript levels may therefore indicate an increased risk for hepatocellular and cholangiocellular carcinomas.