A selective nonpeptide somatostatin receptor 5 agonist effectively decreases insulin secretion in hyperinsulinism.

Congenital hyperinsulinism (HI), a beta cell disorder most commonly caused by inactivating mutations of beta cell KATP channels, results in dysregulated insulin secretion and persistent hypoglycemia. Children with KATP-HI are unresponsive to diazoxide, the only FDA-approved drug for HI, and utility of octreotide, the second-line therapy, is limited because of poor efficacy, desensitization, and somatostatin receptor type 2 (SST2)-mediated side effects. Selective targeting of SST5, an SST receptor associated with potent insulin secretion suppression, presents a new avenue for HI therapy. Here, we determined that CRN02481, a highly selective nonpeptide SST5 agonist, significantly decreased basal and amino acid-stimulated insulin secretion in both Sur1-/- (a model for KATP-HI) and wild-type mouse islets. Oral administration of CRN02481 significantly increased fasting glucose and prevented fasting hypoglycemia compared to vehicle in Sur1-/- mice. During a glucose tolerance test, CRN02481 significantly increased glucose excursion in both WT and Sur1-/- mice compared to the control. CRN02481 also reduced glucose- and tolbutamide-stimulated insulin secretion from healthy, control human islets similar to the effects observed with SS14 and peptide somatostatin analogs. Moreover, CRN02481 significantly decreased glucose- and amino acid-stimulated insulin secretion in islets from two infants with KATP-HI and one with Beckwith-Weideman Syndrome-HI. Taken together, these data demonstrate that a potent and selective SST5 agonist effectively prevents fasting hypoglycemia and suppresses insulin secretion not only in a KATP-HI mouse model but also in healthy human islets and islets from HI patients.

Controlled dimerization of insulin-like growth factor-1 and insulin receptors reveals shared and distinct activities of holo and hybrid receptors.

Breast cancer development and progression are influenced by insulin-like growth factor receptor 1 (IGF1R) and insulin receptor (InsR) signaling, which drive cancer phenotypes such as cell growth, proliferation, and migration. IGF1R and InsR form IGF1R/InsR hybrid receptors (HybRs) consisting of one molecule of IGF1R and one molecule of InsR. The specific signaling and functions of HybR are largely unknown, as HybR is activated by both IGF1 and insulin, and no cellular system expresses HybR in the absence of holo-IGF1R or holo-InsR. Here we studied the role of HybR by constructing inducible chimeric receptors and compared HybR signaling with that of holo-IGF1R and holo-InsR. We cloned chemically inducible chimeric IGF1R and InsR constructs consisting of the extracellular domains of the p75 nerve growth factor receptor fused to the intracellular ß subunit of IGF1R or InsR and a dimerization domain. Dimerization with the drugs AP20187 or AP21967 allowed specific and independent activation of holo-IGF1R, holo-InsR, or HybR, resulting in activation of the PI3K pathway. Holo-IGF1R and HybR both promoted cell proliferation and glucose uptake, whereas holo-InsR only promoted glucose uptake, and only holo-IGF1R showed anti-apoptotic effects. We also found that the three receptors differentially regulated gene expression: holo-IGF1R and HybR up-regulated EGR3; holo-InsR specifically down-regulated JUN and BCL2L1; holo-InsR down-regulated but HybR up-regulated HK2; and HybR specifically up-regulated FHL2, ITGA6, and PCK2. Our findings suggest that, when expressed and activated in mammary epithelial cells, HybR acts in a manner similar to IGF1R and support further investigation of the role of HybR in breast cancer.

Oncogenic non-coding RNA NEAT1 promotes the prostate cancer cell growth through the SRC3/IGF1R/AKT pathway.

Steroid receptor co-activator3 (SRC3) has been known to severe as an androgen receptor (AR) coactivator and is involved in the prostate cancer progression. Non-coding RNA (ncRNA) plays an important role in the cancer progression. However, the mechanism underlying the relationship between ncRNA and AR coactivators is still unclear. Here, we found a ncRNA, Nuclear Enriched Abundant Transcript 1 (NEAT1), was able to interact with SRC3 in the prostate cancer cell lines. NEAT1 can upregulate the AKT phosphorylation via a SRC3/IGF1R pathway. In function, NEAT1 promoted the prostate cancer cell growth through IGF1R/AKT signaling pathway. The NEAT1, SRC3, and IGF1R were highly expressed in the patients' samples of prostate cancer. Therefore, we found a novel SRC3 binding ncRNA that can promote the prostate cancer cell growth through SRC3/IGF1R/AKT pathway.

MicroRNA-381 inhibits cell proliferation and invasion in endometrial carcinoma by targeting the IGF-1R.

Endometrial carcinoma (EC) is the sixth most common type of malignant tumor occurring in females. MicroRNAs (miRNAs) serve as oncogenes or tumor suppressors in human cancer and play important roles in tumorigenesis, and tumor development by regulating various processes. Thus, further investigation into miRNAs involved in EC formation and progression may aid in developing effective therapeutic strategies for patients with this disease. miRNA­381 (miR­381) is aberrantly expressed in multiple types of human cancer. However, the expression pattern, biological roles and underlying mechanisms of miR­381 in EC are poorly understood. In the present study, the results showed that miR­381 was downregulated in EC tissues and cell lines. Decreased miR­381 expression correlated with the International Federation of Gynecology and Obstetrics stage, lymph nodes metastasis and myometrial invasion of EC. The ectopic expression of miR­381 significantly inhibited the proliferation and invasion of EC cells. Through a series of experiments, the insulin­like growth factor receptor 1 (IGF­1R) was identified as a novel direct target of miR­381 in EC. Furthermore, IGF­1R was highly expressed in EC tissues and inversely correlated with miR­381 levels. IGF­1R overexpression partially abrogated the tumor­suppressive effects of miR­381 on the proliferation and invasion of EC cells. miR­381 targeted IGF­1R to inactivate the protein kinase B (AKT) and extracellular signal­regulated kinase (ERK) signaling pathways in EC. These results suggest that miR­381 acts as a tumor suppressor in EC by directly targeting IGF­1R, and indirectly regulating the AKT and ERK signaling pathways. Thus, miR­381 should be investigated as a prognostic biomarker and novel therapeutic target for the treatment of patients with EC.

Upregulation of IRS1 Enhances IGF1 Response in Y537S and D538G ESR1 Mutant Breast Cancer Cells.

Increased evidence suggests that somatic mutations in the ligand-binding domain of estrogen receptor [ER (ERα/ESR1)] are critical mediators of endocrine-resistant breast cancer progression. Insulinlike growth factor-1 (IGF1) is an essential regulator of breast development and tumorigenesis and also has a role in endocrine resistance. A recent study showed enhanced crosstalk between IGF1 and ERα in ESR1 mutant cells, but detailed mechanisms are incompletely understood. Using genome-edited MCF-7 and T47D cell lines harboring Y537S and D538G ESR1 mutations, we characterized altered IGF1 signaling. RNA sequencing revealed upregulation of multiple genes in the IGF1 pathway, including insulin receptor substrate-1 (IRS1), consistent in both Y537S and D538G ESR1 mutant cell line models. Higher IRS1 expression was confirmed by quantitative reverse transcription polymerase chain reaction and immunoblotting. ESR1 mutant cells also showed increased levels of IGF-regulated genes, reflected by activation of an IGF signature. IGF1 showed increased sensitivity and potency in growth stimulation of ESR1 mutant cells. Analysis of downstream signaling revealed the phosphoinositide 3-kinase (PI3K)-Akt axis as a major pathway mediating the enhanced IGF1 response in ESR1 mutant cells. Decreasing IRS1 expression by small interfering RNA diminished the increased sensitivity to IGF1. Combination treatment with inhibitors against IGF1 receptor (IGF1R; OSI-906) and ER (fulvestrant) showed synergistic growth inhibition in ESR1 mutant cells, particularly at lower effective concentrations. Our study supports a critical role of enhanced IGF1 signaling in ESR1 mutant cell lines, pointing toward a potential for cotargeting IGF1R and ERα in endocrine-resistant breast tumors with mutant ESR1.

Implication of epithelial-mesenchymal transition in IGF1R-induced resistance to EGFR-TKIs in advanced non-small cell lung cancer.

The underlying mechanisms for acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) in about 30%-40% of non-small cell lung cancer (NSCLC) patients remain elusive. Recent studies have suggested that activation of epithelial-mesenchymal transition (EMT) and type 1 insulin-like growth factor receptor (IGF1R) is associated with acquired EGFR-TKIs resistance in NSCLC. Our study aims to further explore the mechanism of EMT and IGF1R in acquired EGFR-TKIs resistance in NSCLC cell lines with mutant (PC-9) or wild-type EGFR (H460). Compared to parental cells, EGFR-TKIs-resistant PC-9/GR and H460/ER cells displayed an EMT phenotype and showed overexpression of IGF1R. SiIGF1R in PC-9/GR and H460/ER cells reversed EMT-related morphologies and reversed their resistance to EGFR-TKIs. Exogenous IGF-1 alone induced EMT in EGFR-TKIs-naïve PC-9 and H460 cells and increased their resistance against EGFR-TKIs. Inducing EMT by TGF-ß1 in PC-9 and H460 cells decreased their sensitivity to EGFR-TKIs, whereas reversing EMT by E-cadherin overexpression in PC-9/GR and H460/ER cells restored their sensitivity to EGFR-TKIs. These data suggest that IGF1R plays an important role in acquired drug resistance against EGFR-TKIs by inducing EMT. Targeting IGF1R and EMT may be a potential therapeutic strategy for advanced NSCLC with acquired EGFR-TKIs resistance.

The role of EphB4 and IGF-IR expression in breast cancer cells.

OBJECTIVE: to investigate the role of EphB4 and IGF-1R in the proliferation and migration of breast cancer. METHODS: The relative mRNA levels of EphB4 were measured by RT-PCR. The proliferation of the cells was determined by MTT assay, and cells migration and invasive ability was analyzed using the scratch migration assay. RESULTS: The expression of EphB4 in control group was significantly decreased when compared with IGF-I group (P<0.001). The expression of EphB4 in IGF-I+LY and LY group were lower than that of the control group (P<0.001).The cell proliferation and migration ability of the cells in IGF-I group increased significantly compared to the cells in the control group (P<0.001), while the cells in IGF-1+LY group and LY group showed a decreased proliferation and migration ability compared to the control group (P<0.001). CONCLUSION: IGF-IR might be a upstream gene of EphB4. Besides, higher expression of EphB4 shows increased tumor proliferation and migration in breast cells. The study of EphB4 upstream gene and signaling pathway can provide more targeted anti-tumor point selection for targeted therapy.

Classifying the adverse mitogenic mode of action of insulin analogues using a novel mechanism-based genetically engineered human breast cancer cell panel.

Insulin analogues are widely used in clinical practice. Modifications on the insulin molecular structure can affect the affinity and activation towards two closely related receptor tyrosine kinases: the insulin receptor (INSR) and the insulin-like growth factor 1 receptor (IGF1R). A switch towards higher IGF1R affinity is likely to emphasize mitogenesis rather than glucose metabolism. Relevant well-validated experimental tools to address the insulin analogue activation of either INSR or IGF1R are missing. We have established a panel of human MCF-7 breast cancer cell lines either ectopically expressing the INSR (A or B isoform) in conjunction with a stable knockdown of the IGF1R or ectopically expressing the IGF1R in conjunction with a stable knockdown of the INSR. In these cell lines, we systematically evaluated the INSR and IGF1R receptor activation and downstream mitogenic signalling of all major clinical relevant insulin analogues in comparison with insulin and IGF1R. While most insulin analogues primarily activated the INSR, the mitogenic activation pattern of glargine was highly similar to IGF1 and insulin AspB10, known to bind IGF1R and induce carcinogenesis. Yet, in a long-term proliferation assay, the proliferative effect of glargine was not much different from regular insulin or other insulin analogues. This was caused by the rapid enzymatic conversion into its two metabolic active metabolites M1 and M2, with reduced mitogenic signalling through the IGF1R. In summary, based on our new cell models, we identified a similar mitogenic potency of insulin glargine and AspB10. However, rapid enzymatic conversion of glargine precludes a sustained activation of the IGF1R signalling pathway.

Influence of estradiol on insulin-like growth factor-1-induced luteinizing hormone secretion.

Several studies suggest an interrelationship between estradiol (E2) and insulin-like growth factor-1 (IGF-1) at the hypothalamic level. The present study was designed to discern if the capability of IGF-1 to release LH and influence the timing of female puberty is influenced by E2. Twenty-eight-day-old female rats were ovariectomized (OVEX), then implanted with a third ventricular (3V) cannula. Two weeks later, these animals received subcutaneous (s.c.) injection of oil, or either one or two injections of E2 in the form of estradiol benzoate (1 microg). Forty-eight hours later, four basal blood samples were drawn then the animals received IGF-1 (200 ng) or saline via the 3V and four more blood samples were taken. Results indicated that E2 replacement lowered basal LH levels and IGF-1 induced a significant LH release in only animals that had E2 levels above 20 pg/ml. These levels of E2 were also associated with increases (p<0.05) in the expression of both IGF-1 receptor (IGF-1R) mRNA and protein. In order to further support the hypothesis that the action of IGF-1 at the time of puberty is influenced by E2, 24-day-old intact female rats received s.c. injection of sesame oil or 0.1 microg of E2. The next day, the E2-treated animals also received twice daily s.c. injections of either IGF-1 (500 ng) or saline until vaginal opening (VO) occurred. The animals that received E2 plus IGF-1 showed VO at 31.1 days, which was 2.5 days earlier (p<0.01) than E2-treated animals and 4 days earlier (p<0.001) than IGF-1-treated and saline control animals. Taken together, these results indicate that the hypothalamic action of IGF-1 to stimulate LH release and advance female pubertal development is dependent upon the influence of E2.

Discovery of a potent, highly selective, and orally efficacious small-molecule activator of the insulin receptor.

A series of 3,6-diaryl-2,5-dihydroxybenzoquinones were synthesized and evaluated for their abilities to selectively activate human insulin receptor tyrosine kinase (IRTK). 2, 5-Dihydroxy-6-(1-methylindol-3-yl)-3-phenyl-1,4-benzoquinone (2h) was identified as a potent, highly selective, and orally active small-molecule insulin receptor activator. It activated IRTK with an EC(50) of 300 nM and did not induce the activation of closely related receptors (IGFIR, EGFR, and PDGFR) at concentrations up to 30 000 nM. Oral administration of the compound to hyperglycemic db/db mice (0.1-10 mg/kg/day) elicited substantial to nearly complete correction of hyperglycemia in a dose-dependent manner. In ob/ob mice, the compound (10 mg/kg) caused significant reduction in hyperinsulinemia. A structurally related compound 2c, inactive in IRTK assay, failed to affect blood glucose level in db/db mice at equivalent exposure levels. Results from additional studies with compound 2h, aimed at evaluating classical quinone-related phenomena, provided sufficient grounds for optimism to allow more extensive toxicologic evaluation.