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Alzheimer’s disease (AD) is the leading cause of dementia among the elderly population, posing a significant public health challenge due to limited therapeutic options that merely delay cognitive decline. AD is associated with impaired energy metabolism and reduced neurotrophic signaling. The insulin-like growth factor (IGF) signaling pathway, crucial for central nervous system (CNS) development, metabolism, repair, cognition, and emotion regulation, includes IGF-1, IGF-2, IGF-1R, IGF-2R, insulin receptor (IR), and six insulin-like growth factor binding proteins (IGFBPs). Research has identified abnormalities in IGF signaling in individuals with AD and AD models. Dysregulated expression of IGFs, receptors, IGFBPs, and disruptions in downstream phosphoinositide 3-kinase-protein kinase B (PI3K/AKT) and mitogen-activated protein kinase (MAPK) pathways collectively increase AD susceptibility. Studies suggest modulating the IGF pathway may ameliorate AD pathology and cognitive decline. This review explores the CNS pathophysiology of IGF signaling in AD progression and assesses the potential of targeting the IGF system as a novel therapeutic strategy. Further research is essential to elucidate how aberrant IGF signaling contributes to AD development, understand underlying molecular mechanisms, and evaluate the safety and efficacy of IGF-based treatments.

Drug resistance often critically limits the efficacy of molecular targeted drugs. Although pharmacological inhibition of phosphatidylinositol 3‐kinase (PI3K) is an attractive therapeutic strategy for cancer therapy, molecular determinants for efficacy of PI3K inhibitors (PI3Kis) remain unclear. We previously identified that overexpression of insulin‐like growth factor 1 receptor (IGF1R) contributed to the development of drug resistance after long‐term exposure to PI3Kis. In this study, we examined the involvement of basal IGF1R expression in intrinsic resistance of drug‐naïve cancer cells to PI3Kis and whether inhibition of IGF1R overcomes the resistance. We found that cancer cells highly expressing IGF1R showed resistance to dephosphorylation of Akt and subsequent antitumor effect by ZSTK474 treatment. Knockdown of IGF1R by siRNAs facilitated the dephosphorylation and enhanced the drug efficacy. These cells expressed tyrosine‐phosphorylated insulin receptor substrate 1 at high levels, which was dependent on basal IGF1R expression. In these cells, the efficacy of ZSTK474 in vitro and in vivo was improved by its combination with the IGF1R inhibitor OSI‐906. Finally, we found a significant correlation between the basal expression level of IGF1R and the inefficacy of ZSTK474 in an in vivo human cancer panel, as well as in vitro. These results suggest that basal IGF1R expression affects intrinsic resistance of cancer cells to ZSTK474, and IGF1R is a promising target to improve the therapeutic efficacy. The current results provide evidence of combination therapy of PI3Kis with IGF1R inhibitors for treating IGF1R‐positive human cancers. Cancer cells highly expressing insulin‐like growth factor 1 receptor (IGF1R) exhibited resistance to a PI3K inhibitor ZSTK474, and the resistance was diminished after expression knockdown of the IGF1R gene. Moreover, the combination therapy of ZSTK474 with an IGF1R inhibitor exerted a synergistic effect on cancer cells highly expressing IGF1R both in vitro and in vivo. These observations indicated that basal expression of IGF1R in cancer cells confers intrinsic resistance to ZSTK474, and a combination therapy of ZSTK474 with an IGF1R inhibitor would be a promising therapeutic strategy for treating IGF1R‐positive human tumors.

Enhancement of insulin-like growth factor 1 receptor (IGF-IR) degradation by heat shock protein 90 (HSP90) inhibitor is a potential antitumor therapeutic strategy. However, very little is known about how IGF-IR protein levels are degraded by HSP90 inhibitors in pancreatic cancer (PC). We found that the HSP90α inhibitor NVP-AUY922 (922) effectively downregulated and destabilized the IGF-1Rβ protein, substantially reduced the levels of downstream signaling molecules (p-AKT, AKT and p-ERK1/2), and resulted in growth inhibition and apoptosis in IGF-1Rβ-overexpressing PC cells. Preincubation with a proteasome or lysosome inhibitor (MG132, 3 MA or CQ) mainly led to IGF-1Rβ degradation via the lysosome degradation pathway, rather than the proteasome-dependent pathway, after PC cells were treated with 922 for 24 h. These results might be associated with the inhibition of pancreatic cellular chymotrypsin–peptidase activity by 922 for 24 h. Interestingly, 922 induced autophagic flux by increasing LC3II expression and puncta formation. However, knockdown of the crucial autophagy component AGT5 and the chemical inhibitor 3 MA-blocked 922-induced autophagy did not abrogate 922-triggered IGF-1Rβ degradation. Furthermore, 922 could enhance chaperone-mediated autophagy (CMA) activity and promote the association between HSP/HSC70 and IGF-1Rβ or LAMP2A in coimmunoprecipitation and immunofluorescence analyses. Silencing of LAMP2A to inhibit CMA activity reversed 922-induced IGF-1Rβ degradation, suggesting that IGF-1Rβ degradation by 922 was partially dependent on the CMA pathway rather than macroautophagy. This finding is mirrored by the identification of the KFERQ-like motif in IGF-1Rβ. These observations support the potential application of 922 for IGF-1Rβ-overexpressing PC therapy and first identify the role of the CMA pathway in IGF-1Rβ degradation by an HSP90 inhibitor.

Key Points Preclinical evidence for a role of insulin and insulin-like growth factor (IGF) signalling in promoting neoplastic growth is impressive. Several different targeting strategies for the insulin and IGFI receptor family exist, and dozens of drug candidates have shown activity in model systems. Phase III clinical trials have so far been undertaken only with IGFI receptor-specific antibodies. Although the final results have not yet been published, disappointing reports have been presented for some of these trials. Future trials may differ by incorporating predictive biomarkers, by using rational combination therapy approaches and by using other pharmacological approaches to targeting, such as anti-ligand antibodies or tyrosine kinase inhibitors. The insulin and IGFI receptor family may be involved in resistance mechanisms to therapies that target other signalling nodes in cancer cells, suggesting that there may be situations in which co-targeting will confer benefit. The insulin and IGFI receptor family is now known to have a role in the important relationships between macronutrient intake and cancer, diabetes and cancer, and obesity and cancer. Biguanides, such as metformin, which is widely used in diabetes treatment, have been reported in hypothesis-generating retrospective population studies of subjects with diabetes to be associated with reduced cancer burden. These agents lower insulin levels if they are increased, and have a variety of effects on cellular signalling and cellular metabolism. However, there are gaps in knowledge related to their pharmacokinetics and mechanisms of action that require elucidation. This Review reflects on the recent disappointing initial results from Phase III trials of insulin-like growth factor I receptor (IGF1R)-specific antibodies for cancer treatment, and discusses the next steps in targeting insulin and IGFI signalling in cancer therapy. Although several early phase clinical trials raised enthusiasm for the use of insulin-like growth factor I receptor (IGF1R)-specific antibodies for cancer treatment, initial Phase III results in unselected patients have been disappointing. Further clinical studies may benefit from the use of predictive biomarkers to identify probable responders, the use of rational combination therapies and the consideration of alternative targeting strategies, such as ligand-specific antibodies and receptor-specific tyrosine kinase inhibitors. Targeting insulin and IGF signalling also needs to be considered in the broader context of the pathophysiology that relates obesity and diabetes to neoplasia, and the effects of anti-diabetic drugs, including metformin, on cancer risk and prognosis. The insulin and IGFI receptor family is also relevant to the development of PI3K–AKT pathway inhibitors.

Insulin-like growth factor I (IGF-I) plays a critical role in regulating proliferation, differentiation, growth, and survival in fish as well as in humans. Few studies have investigated the involvement of IGFs in bivalves. In Korea, the Pacific oyster Crassostrea gigas is an important aquaculture species, and its growth is dependent on environmental conditions. Intrinsic factors that can be used as indicators to assess oyster growth based on individual size are limited. This study analyzed IGF-I, IGF-I receptor (IGF-IR), and IGF binding protein (IGFBP) in adductor muscle of C. gigas in winter using immunoblotting and reverse transcriptase-polymerase chain reaction. Levels of IGF-I and the IGF-IR β subunit, and expression of C. gigas insulin receptor-related receptor and IGFBP messenger RNA were significantly higher in large individuals (LI) than small individuals (SI). The IGF-IR β subunit was detected in the adductor muscle of both groups; however, phosphorylation of the IGF-IR β subunit and extracellular signal-regulated kinase was greater in LI than SI. The condition index of C. gigas showed a similar pattern. The results of this study suggest that the IGF system is associated with growth rate differences in C. gigas during winter in Korea.

Insulin-like growth factor 1 receptor (IGF1R) is a cell surface receptor, belonging to the tyrosine kinase receptor superfamily. IGF1R plays a role not only in normal cell development but also in malignant transformation, which has become a candidate therapeutic target for the treatment of human cancer. This study aimed to explore insertions and deletions (indels) in IGF1R gene and investigate their association with growth traits in four Chinese cattle breeds (Xianan cattle, Jinnan cattle, Qinchuan cattle and Nanyang cattle). The current paper identified a 28-bp indel by polymerase chain reaction within IGF1R gene. The analysis showed that there was a significant correlation between the locus and the hucklebone width of Nanyang cattle in four periods, in which it was highly correlated at 6, 12 and 18 months. At the age of 6 months, it was also significantly correlated with body height, body weight and body length. Association analysis showed that the locus in Jinnan cattle was extremely significantly correlated with body slanting length and body weight, and significantly correlated with chest circumference. There was no significant correlation between this locus and growth traits of Xianan cattle and Qinchuan cattle. The detected indel in the IGF1R gene was significantly associated with growth traits in Jinnan and Nanyang cattle, and could be used as a molecular marker for growth trait selection.

The risk of renal cell carcinoma development is correlated with obesity and type II diabetes. Since insulin and insulin-like growth factors play a key role during development of both metabolic diseases, these molecules may be important in RCC pathophysiology We investigated the effect of insulin and IGFs on RCC cells using in vitro model with 786-O, 769-P, Caki-1, Caki-2, ACHN cancer cell lines. Cancer cells were compared with normal kidney cells - PCS-400-010 and HEK293. The growth, viability of cells as well as migration rate were assessed upon hormonal stimulation. The insulin receptor and Insulin-like growth factor 1 receptor presence were evaluated and the expression of 84 genes related to insulin signaling pathway. In all RCC cell lines IGF-1R expression was confirmed in contrast to IR, which was expressed only in control HEK293 cell line. Insulin and IGFs stimulated RCC cells growth and migration rate. Insulin, IGF-1 and IGF-2 triggered both IR and IGF-1R phosphorylation. Analyzed RCC did not secret insulin, IGF-1 or IGF-2 and were not activated in autocrine-paracrine signaling loop. Insulin and IGFs stimulations triggered down-regulation of PI3K-Akt-mTOR and Ras-MAPK pathway gens, as well as DOK2–3, INS, FRS3, IRS1–2, IGF1R – genes encoding insulin receptor-associated proteins. In conclusion, we showed that IGFs and insulin may play a stimulatory role for renal cancer cells, thus they can possibly affect renal cancer tumorigenesis and progression on cellular level.

The insulin-like growth factor type 1 receptor (IGF-1R) plays a key role in the development and progression of cancer; however, therapeutics targeting it have had disappointing results in the clinic. As a receptor tyrosine kinase (RTK), IGF-1R is traditionally described as an ON/OFF system, with ligand stabilizing the ON state and exclusive kinase-dependent signaling activation. Newly added to the traditional model, ubiquitin-mediated receptor downregulation and degradation was originally described as a response to ligand/receptor interaction and thus inseparable from kinase signaling activation. Yet, the classical model has proven over-simplified and insufficient to explain experimental evidence accumulated over the last decade, including kinase-independent signaling, unbalanced signaling, or dissociation between signaling and receptor downregulation. Based on the recent findings that IGF-1R “borrows” components of G-protein coupled receptor (GPCR) signaling, including β-arrestins and G-protein-related kinases, we discuss the emerging paradigm for the IGF-1R as a functional RTK/GPCR hybrid, which integrates the kinase signaling with the IGF-1R canonical GPCR characteristics. The contradictions to the classical IGF-1R signaling concept as well as the design of anti-IGF-1R therapeutics treatment are considered in the light of this paradigm shift and we advocate recognition of IGF-1R as a valid target for cancer treatment.

Triple-negative breast cancer (TNBC) lacks targeted therapies, leaving cytotoxic chemotherapy as the current standard treatment. However, chemotherapy resistance remains a major clinical challenge. Increased insulin-like growth factor 1 signaling can potently blunt chemotherapy response, and lysosomal processes including the nutrient scavenging pathway autophagy can enable cancer cells to evade chemotherapy-mediated cell death. Thus, we tested whether inhibition of insulin receptor/insulin-like growth factor 1 receptor with the drug BMS-754807 and/or lysosomal disruption with hydroxychloroquine (HCQ) could sensitize TNBC cells to the chemotherapy drug carboplatin. Using in vitro studies in multiple TNBC cell lines, in concert with in vivo studies employing a murine syngeneic orthotopic transplant model of TNBC, we show that BMS-754807 and HCQ each sensitized TNBC cells and tumors to carboplatin and reveal that exogenous metabolic modulators may work synergistically with carboplatin as indicated by Bliss analysis. Additionally, we demonstrate the lack of overt in vivo toxicity with our combination regimens and, therefore, propose that metabolic targeting of TNBC may be a safe and effective strategy to increase sensitivity to chemotherapy. Thus, we conclude that the use of exogenous metabolic modulators, such as BMS-754807 or HCQ, in combination with chemotherapy warrants additional study as a strategy to improve therapeutic responses in women with TNBC.

Leydig cell tumours (LCTs) are uncommon stromal neoplasms of the testis, accounting for less than 3% of all gonadal cancers. Most of them are benign, but the malignant ones are very aggressive without specific effective treatment. Several studies reported pharmacologic insight into the use of statins as anti‐tumour agents, but their efficacy on LCTs has not been investigated. Previously, we emphasised the central role of insulin‐like growth factor 1 (IGF1)/insulin‐like growth factor 1 receptor (IGF1R) signalling in Leydig cell tumorigenesis; here, we showed that simvastatin reduces cell proliferation, determines cell cycle arrest at the G1 phase, and induces reactive oxygen species (ROS) accumulation and apoptosis in R2C and LC540 rat Leydig tumour cells. Furthermore, it prevents isoprenoid farnesyl pyrophosphate (FPP) formation and decreases IGF1R expression, leading to the breakdown of the IGF1R signalling pathway. Importantly, we observed that simvastatin synergised with cisplatin in reducing tumour cell proliferation. Collectively, these data suggest that simvastatin is a potential anticancer drug capable of counteracting LCT growth, and it could be proposed as an adjuvant for chemotherapy in LCT treatment.