Serum Insulin-like Growth Factor II Research Articles

Low Serum Insulinlike Growth FactorII Levels Correlate with High BMI in American Indian Adults.

Insulinlike growth factorII (IGF-II) regulates metabolism and growth. In humans, both positive and negative relationships have been reported between serum IGF-II levels and obesity. This study assessed the relationship between serum IGF-II levels and BMI and determined whether IGF-II levels predict weight gain. Serum samples were available from 911 American Indians with a recorded BMI. IGF-II was measured using enzyme-linked immunosorbent assay. Serum IGF-II levels were negatively correlated with BMI (r = -0.17, P = 4.4 × 10-7 , adjusted for age, sex, and storage time). The strongest correlation was in participantsaged≥ 30 years (r = -0.28, P = 3.4 × 10-8 , N = 349), a modest correlation was in participants aged20 to 29 years (r = -0.15, P = 7.6 × 10-3 , N = 322), and participants aged15 to 19 years had no correlation (r = 0.05, P = 0.48, N = 240). IGF-II levels did not predict weight gain. However, among individuals who had genotypes for 64 established obesity variants (age ≥ 20 years, N = 671), a genetic risk score for high BMI was associated with lower IGF-II (β = -0.08 SDof IGF-II per SDof the genetic risk score, P = 0.025). There is a negative relationship between IGF-II levels and BMI, in which the correlation is stronger at older ages. The association between genetic risk for BMI and IGF-II levels suggests that this correlation may be due to an effect of obesity on IGF-II.

Characteristics of Hepatic IGF-II Expression and Monitored Levels of Circulating IGF-II mRNA in Metastasis of Hepatocellular Carcinoma

The prognosis of hepatocellular carcinoma (HCC) remains dismal. Insulin-like growth factor II (IGF-II), a fetal growth factor, is highly expressed during HCC development. We examined serum IGF-II levels and circulating IGF-II messenger RNA (mRNA) expression and analyzed the clinicopathologic characteristics in patients with liver diseases. The higher IGF-II level in the serum of patients with HCC could be correlated with hepatitis B virus infection but not with patient sex, age, tumor size, or α-fetoprotein (AFP) level. Total RNAs were extracted from liver tissues or peripheral blood mononuclear cells, and IGF-II complementary DNA (cDNA) and AFP cDNA were synthesized through random primers and reverse transcriptase; gene fragments were amplified by nested polymerase chain reaction and confirmed by sequencing. The incidence of the hepatic IGF-II gene was 100% in HCC, 54.3% in paracancerous tissues, and none in noncancerous tissues. The incidence rates for circulating IGF-II and AFP genes were 34.3% and 52.7%, respectively, and for both, 61.6% in patients with HCC. They were 100% in cases with extrahepatic metastasis. The IGF-II abnormality associates with HCC, and circulating IGF-II and IGF-II mRNA are useful molecular markers for HCC differential diagnosis and hematogenous metastasis.

Solitary fibrous tumor of the pleura with hypoglycemia associated with serum insulin-like growth factor II

Although more than half of patients with SFTP are free of symptoms, large tumors cause respiratory symptoms such as dyspnea, cough, hemoptysis, and chest pain as a result of bronchial compression, atelectasis, and obstructive pneumonia. Furthermore, systemic symptoms, such as hypoglycemia and hypertrophic osteoarthropathy, and nonspecific symptoms, such as fever and fatigue, are occasionally found in patients with SFTP. The incidence of hypoglycemia has been reported to be approximately 4%. Although insulin-like growth factor II (IGF-II) is considered to be related to the hypoglycemia, there are few reports manifesting this relationship on the basis of specific data. 1 We herein describe a rare case of malignant SFTP with hypoglycemia closely associated with serum IGF-II.

IGF-II transgenic mice display increased aberrant colon crypt multiplicity and tumor volume after 1,2-dimethylhydrazine treatment

In colorectal cancer insulin-like growth factor II (IGF-II) is frequently overexpressed. To evaluate, whether IGF-II affects different stages of tumorigenesis, we induced neoplastic alterations in the colon of wild-type and IGF-II transgenic mice using 1,2-dimethylhydrazine (DMH). Aberrant crypt foci (ACF) served as markers of early lesions in the colonic mucosa, whereas adenomas and carcinomas characterized the endpoints of tumor development. DMH-treatment led initially to significantly more ACF in IGF-II transgenic than in wild-type mice. This increase in ACF was especially prominent for those consisting of ≥three aberrant crypts (AC). Nevertheless, adenomas and adenocarcinomas of the colon, present after 34 weeks in both genetic groups, were not found at different frequency. Tumor volumes, however, were significantly higher in IGF-II transgenic mice and correlated with serum IGF-II levels. Immunohistochemical staining for markers of proliferation and apoptosis revealed increased cell proliferation rates in tumors of IGF-II transgenic mice without significant affection of apoptosis. Increased proliferation was accompanied by elevated localization of β-catenin in the cytosol and cell nuclei and reduced appearance at the inner plasma membrane. In conclusion, we provide evidence that IGF-II, via activation of the β-catenin signaling cascade, promotes growth of ACF and tumors without affecting tumor numbers.

Serum vascular endothelial growth factor C (VEGF-C) as a specific biomarker for advanced cervical cancer: Relationship to insulin-like growth factor II (IGF-II), IGF binding protein 3 (IGF-BP3) and VEGF-B

An early non-invasive diagnosis of cervical cancer and its metastasis can save lives. We have shown that serum IGF-II levels can be effectively used for a specific early diagnosis of cervical cancer. Here, we shall determine if serum levels of vascular endothelial growth factors B and C (VEGF-A [corrected] VEGF-C) associated with vasculogenic and lymphogenic metastasis may be used for an early diagnosis of advanced metastatic cervical cancer and compare these levels with those of the serum IGF-II and IGF-binding protein 3 (IGF-BP3). (a) Serum levels of IGF-II, IGF-BP3, VEGF-A [corrected] (VEGF(165)) and VEGF-C (ELISA kits) were determined in: 82 controls with normal Pap smears; 29 women with atypical squamous cells of undetermined significance (ASCUS) and normal cervical biopsy; 46 ASCUS and cervical intraepithelial neoplasia (CIN) on biopsy; 8 pre-therapy CIN-I; 23 successfully treated CIN-I; 75 persistent CIN-I; 14 CIN-II/III pre-therapy; 14 successfully treated CIN-II/III; 70 persistent CIN-II/III; 86 pre-therapy cervical cancer; 26 in early grades of cervical cancer; 21 in late grades of cervical cancer; 22 cervical cancer patients in remission; 50 persistent cervical cancer; 18 with ovarian cancer; and 57 with endometrial cancer. (b) Serial serum samples collected over 5 years in 5 women with progressing cervical cancer were also tested. (c) Serum and tissue VEGF-C were enumerated in 20 matched serum (ELISA) and tissue (semi-quantitative immunofluorescent antibody assay) samples from controls, early cervical cancer, late cervical cancer, ovarian cancer and endometrial cancer patients. Student's t test, chi-square analysis and linear regression analysis were used. (a) As anticipated, serum IGF-II levels were elevated as early as ASCUS with CIN on biopsy and continued to be elevated in CIN (all grades; pre-therapy and persistent) and cervical cancer (pre-therapy, early, late and persistent). Serum IGF-II levels were normal in ASCUS with normal biopsy, successfully treated CIN-I, II/III, cervical cancer as well as pre-therapy ovarian and endometrial cancers (therapy efficacy: P < 0.0001 by chi-square analysis). Serum IGF-BP3 showed a significant decrease with advancing disease. Serum VEGF-A [corrected] levels were the highest in pre-therapy, early, advanced and persistent cervical cancer, as well as in ovarian and endometrial cancers. Serum VEGF-C levels, on the other hand, were the highest in late and persistent cervical cancers, but not in ovarian or endometrial cancers. (b) In the 5 women with serial samples, the serum levels of the growth factors showed similar trends. (c) VEGF-C levels in serum and tissue were elevated in cervical cancers especially in advanced grades, while they were normal in serum and tissue from the controls and women with ovarian and endometrial cancers. There was a highly significant positive correlation between VEGF-C and IGF-II and a negative correlation between IGF-BP3 and VEGF-C (P < 0.0001). Serum IGF-II up-regulation is specific to cervical cancer and helps in the early diagnosis of malignant proliferation, while serum VEGF-C up-regulation appears to be a unique marker for an early diagnosis of cervical cancer metastasis. VEGF-C and IGF-II systems appear to be interrelated in cervical cancer, contributing to the early malignant cell proliferation and lympho-vascular metastasis. Serum IGF-BP3 and VEGF-A [corrected] appear to be common markers for all gynecological cancers.

低血糖を併発した perivesical solitary fibrous tumor の1例

Some non-islet tumors can induce hypoglycemia. We report a case of a solitary fibrous tumor (SFT) as perivesical mass associated with hypoglycemia. A 61-year-old man was admitted to our department with recurrent hypoglycemic attack and lower abdominal discomfort, but no symptom of urination. Ultrasonography and magnetic resonance imaging demonstrated a giant heterogeneous mass in the pelvic and rightward shift of bladder, but the tumor's border was clear. Endocrinological analyses showed high serum levels of insulin-like growth factor II (IGF-II) and suppressed secretion of insulin. We removed perivesical tumor that weighed 720 g on 30th January in 2003. After the removal, serum IGF-II levels returned to normal and hypoglycemic attacks ceased. Pathological examination revealed well-circumscribed nodular mass composed of uniform spindle cells arranged in bundles and fascicles with varying amounts of collagen and reticulin fibers. Almost all of the tumor cells were immunohystochemically positive for vimentin and CD34, negative for cytokeratin.

Circulating levels of insulin-like growth factor-II and IGF-binding protein 3 in cervical cancer

Objective We aimed to further document that elevated levels of circulating insulin-like growth factor II (IGF-II) are associated with cervical cancer and to test the hypothesis that there may be an inverse association between IGF-II and IGF-binding protein 3 (IGF-BP3). Method Serum IGF-II and IGF-BP3 levels were measured, using ELISA kits (Diagnostic Systems Laboratories), in 23 controls; 16 ASC-US with normal biopsies; 14 ASC-US with advanced CIN; 2 pretherapy CIN-I; 8 successfully treated CIN-I; 24 persistent CIN I; 14 pretherapy CIN II/III; 10 posttherapy CIN II/III with normal biopsies; 18 persistent CIN-II/III; 7 with pretherapy cervical cancer; 19 with posttherapy cervical cancer under remission; 15 with posttherapy persistent/recurrent cervical cancer; 10 with persistent ovarian or endometrial cancer; and 3 with endometrial or vulvar with cervical cancer. Student's t test and linear regression analysis were used. Results Compared to controls (493 ± 90 ng/ml) and women with other gynecological cancers, serum IGF-II levels were significantly increased in women with ASC-US, with advanced CIN on biopsy ( P < 0.0001), persistent CIN-I (993 ± 262 ng/ml; P < 0.0001), pretherapy advanced CIN (1086 ± 240; P < 0.0001), pretherapy cervical cancer patients (1746 ± 318 ng/ml; P < 0.0001) and posttherapy persistent/recurrent CIN (1094 ± 300; P < 0.0001); and cervical cancer (1395 ± 189; P < 0.0001). After therapy, the IGF-II levels returned to normal in both CIN and cervical cancer patients under remission. Elevated serum IGF-II levels had 100% sensitivity and 87% specificity for cervical cancer and 81% sensitivity and 82% specificity for CIN. The levels of IGF-BP3 were significantly reduced in women with CIN before and after therapy ( P < 0.0001) and in cervical cancer patients before and after therapy ( P < 0.001). There was an inverse relationship between serum IGF-II and BP-3 levels ( P < 0.01). Decreased serum IGF-BP3 levels had a sensitivity of 72% and specificity of 75% for cervical cancer and 81% sensitivity and 83% specificity for CIN. When both markers were considered together the sensitivity was 72% and specificity 84% for cervical cancer, while for CIN, the sensitivity was 57% and specificity 81%. Conclusion Serum IGF-II may be a reliable marker for early diagnosis and monitoring therapy efficacy (sensitivity and specificity of 100% versus normal controls), while IGF-BP3 levels can be reliably used to predict prognosis.

Insulin-like growth factor II in gynecological cancers: a preliminary study.

We have previously reported elevated serum levels of cervical human papilloma viral proteins E6 and E7 and serum insulin-like growth factor II (IGF-II) in women with cervical cancer and advanced cervical intraepithelial neoplasia. As most women with cervical cancer have elevated levels of serum IGF-II, we sought to determine whether the cervical cancer and lymph node biopsies from these women demonstrated increased production of IGF-II and whether this elevation was also present in ovarian and endometrial cancers. We used the semi-quantitative immunofluorescent antibody assay established in our laboratory to identify the levels of IGF-II in 21 cervical cancers (seven with matching lymph nodes), 18 benign cervical biopsies, 13 endometrial cancers, 15 benign endometrial biopsies, 5 ovarian cancers, and 15 benign ovarian biopsies. The immunofluorescent IGF-II levels (relative intensity per pixel) were the highest in cervical cancers; they were significantly higher than in matched controls. IGF-II levels were not higher in ovarian cancers and only slightly elevated in endometrial cancers. The presence of IGF-II in pelvic lymph nodes of women with cervical cancer paralleled with those in the cervical cancers. Interestingly, we could identify small nests of metastases of malignant cells in the nodes (pauci-cellular metastasis) by using IGF-II as the marker. We propose that measurement and identification of IGF-II in the cervical biopsy may be a sensitive method of detecting cervical cancer and metastatic spread in the lymph nodes.

Cervical epidermal growth factor-receptor (EGF-R) and serum insulin-like growth factor II (IGF-II) levels are potential markers for cervical cancer.

To ascertain if cervical epithelial epidermal growth factor receptor (EGF-R) and serum insulin-like growth factor II (IGF-II) levels are potential markers for cervical cancer. We tested cervical biopsies obtained from 18 controls, 3 women with cervical intraepithelial neoplasia (CIN) I, 17 women with CIN II and III, and 12 women with cervical cancer for EGF-R using a quantitative immunofluorescent antibody assay. We measured serum IGF-II levels using an enzyme-linked immunosorbent assay in 20 controls, 26 CIN patients, 12 with cervical cancer before therapy, 5 with cervical cancer for < 1 year, and 9 others > 1 year after therapy. The levels of cervical EGF-R in women with CIN and cervical cancer were significantly higher (P<0.05 for CIN I; P<0.001 for patients with CIN II and III or cervical cancer) than in controls. Women with cervical cancer (P<0.001 vs. controls) or advanced CIN (P = 0.03) had elevated levels of serum IGF-II, while the women with CIN I had levels similar to controls. Women with cervical cancer in the post-therapy period had significantly lower serum IGF-II levels than the women with cervical cancer before therapy (P<0.001). Cervical epithelial EGF-R and serum IGF-II levels may be used for the diagnosis and prognosis of cervical cancer.

Increased and persistent circulating insulin-like growth factor II in neonatal transgenic mice suppresses developmental apoptosis in the pancreatic islets.

In rats, a proportion of pancreatic beta-cells are deleted by apoptosis in the second week of postnatal life and replaced by endocrine cell neogenesis from pancreatic ductal epithelium. This coincides with a reduction in pancreatic insulin-like growth factor II (IGF-II) expression, and IGF-II has been shown to act as a beta-cell survival factor in vitro. To examine whether IGF-II regulates beta-cell apoptosis in vivo, an IGF-II transgenic mouse model was used in which mouse IGF-II is overexpressed in skin, gut, and uterus driven by a keratin promoter, so that circulating IGF-II is retained postnatally. Mice were killed between postnatal days 7 and 26, and the pancreas was examined histologically. Apoptotic cells were visualized by the terminal deoxynucleotidyltransferase-mediated deoxy-UTP nick end labeling method, and proliferating cells were examined by immunohistochemistry for proliferating cell nuclear antigen. In nontransgenic mice, serum IGF-II was absent by 26 days, but mean (+/-SEM) values were 45+/-9 ng/ml (n = 5) in transgenic animals. A 2- to 3-fold rise in islet cell apoptosis was seen in normal animals between days 11 and 16, but this was substantially decreased in IGF-II transgenic mice (day 11; control, 12+/-1%; transgenic, 6+/-1%; P < 0.01; n = 5). Consequently, islets from IGF-II transgenic mice had a significantly greater mean area from days 11-16, but the proportions of beta- and alpha-cells and circulating insulin levels were not changed. Islet cell DNA synthesis was increased in transgenic mice on days 13 and 16. The total islet number per section did not alter. The results show that a persistent presence of circulating IGF-II postnatally alters endocrine pancreatic ontogeny in the mouse and largely prevents the wave of developmental apoptosis that precipitates beta-cell turnover in neonatal life.

Serum insulin-like growth factor II in 44 patients with non-islet cell tumor hypoglycemia.

Serum insulin-like growth factor II (IGF-II) was characterized by radioimmunoassay and Western immunoblot in 44 patients with non-islet cell tumor hypoglycemia (NICTH). 31 of 44 patients with NICTH had big IGF-II in sera. When the presence of IGF-II in tumors from 20 patients was investigated, IGF-II in tumors was detected in 18 patients and these patients had big IGF-II in sera. In two patients whose tumors did not contain IGF-II, big IGF-II in sera was not detected. In six patients with IGF-II in tumors, hypoglycemia disappeared and the big IGF-II decreased after successful removal of the tumors. These data indicate that the big IGF-II could be related to hypoglycemia, and that the increased serum big IGF-II suggests IGF-II-producing NICTH. Serum IGF-II levels in 31 patients with big IGF-II were greater than those in 13 patients without it (Mean +/- SEM: 723+/-54 vs. 326+/-31 ng/ml), but the elevated IGF-II levels were found in only 13 patients. Serum IGF-I levels were low in all patients with NICTH. In the 13 patients without big IGF-II, serum IGF-II levels were lower than those in the patients with big IGF-II, and serum IGF-I levels were also low. Serum IGF-II/IGF-I ratios in the patients with big IGF-II were elevated and greater than those in the patients without big IGF-II (35.0+/-2.2 vs. 11.5+/-2.4). The present data indicate that IGF-II-producing tumors are not rare in NICTH, and serum big IGF-II and IGF-II/IGF-I ratio are useful for screening patients with IGF-II-producing NICTH.

Antisense oligodeoxynucleotides of IGF-II selectively inhibit growth of human hepatoma cells overproducing IGF-II.

Insulin-like growth factor II (IGF-II) is expressed in many developing embryonic tissues and is involved in mammalian growth and development. After birth, serum IGF-II is mainly produced by liver cells. Many reports have indicated that IGF-II is overexpressed in some hepatocellular carcinoma (HCC) tissue. These findings imply the possible importance of this growth factor in carcinogenesis. We screened four human HCC cell lines and three rat HCC cell lines and found that HuH-7 and HepG2 cells produced fivefold more intracellular IGF-II than the other cell lines. Experimental data indicate that IGF-II functions through the intracrine mode for HuH-7 cells. To study whether the overexpression of IGF-II is significant for the growth of HCC or only a consequence of HCC development, we used antisense oligodeoxynucleotides (ATON) to arrest the translation of IGF-II mRNA, and then measured the effects on cell growth. We found that the production of IGF-II was suppressed by ATON, and the decrease of IGF-II resulted in growth inhibition of HuH-7 and HepG2. ATON had no effect on the other tested cell lines, which produced lower levels of IGF-II. The growth inhibition was mainly attributed to a decrease of cell proliferative activity. The results indicate that the IGF-II-overproducing cell lines do depend on IGF-II for growth, and ATON of IGF-II can selectively inhibit the growth of these cells. ATON may be a potential therapeutic agent for this type of HCC in vivo.

Measurement of human IGF-II using Sephacryl extraction: a rapid and reliable assay method.

Measurement of insulin-like growth factor II (IGF-II) in human serum is complicated by the presence of IGF binding proteins and usually involves cumbersome extraction procedures followed by radioimmunoassay. We have utilized an extraction process developed for measuring insulin-like growth factor II in ovine serum using Sephacryl HR100, and have applied this to the extraction of human samples followed by radioimmunoassay for human IGF-II. The assay yielded 98% recovery of unlabelled IGF-II, parallelism between dilutions of eluate and the standard curve, complete removal of binding proteins and near-complete removal of IGF-I, and intra- and interassay coefficients of variation of 5% and 9%, respectively. The normal range for serum IGF-II in women was 490-1056 micrograms/L, and IGF-II levels were positively correlated with serum concentrations of insulin-like growth factor binding protein-3 (IGFBP-3) but not with IGF-I levels. Mean serum concentrations of IGF-II were reduced below normal in a number of hypopituitary patients and children with short stature and IGF-II concentrations in these subjects correlated positively with IGF-I and IGFBP-3. In acromegalic patients IGF-II levels were usually normal and were negatively correlated with IGF-I concentrations. From our experience with the above results the present assay appears particularly suitable for clinical measurements and research projects where high sample throughput is required.

Change in serum concentration of insulin-like growth factor II (IGF-II) in patients with thyroid disease.

We investigated the serum concentration of IGF-II in patients with thyroid diseases (25 with untreated Graves' patients, 30 with hypothyroidism, 23 with thyroid adenoma) and in 72 healthy adults as normal controls, by a sensitive radioimmunoassay of serum IGF-II. Thyroid hormones are known to increase IGF-I production in the liver through the enhancement of GH secretion. In case of IGF-II, however, knowledge has been rather limited. The mean +/- SD concentration in healthy subjects was 556 +/- 94 micrograms/L with neither sex nor age dependence. In untreated Graves' patients, serum IGF-II levels (675 +/- 129 micrograms/L) were significantly (P < 0.01) higher than in normal controls, and significantly lower in patients with hypothyroidism (460 +/- 106 micrograms/L; P < 0.01). Thyroid hormones revealed positive correlation with the IGF-II concentration.

Characterization of insulin-like growth factor II (IGF-II) and IGF binding proteins in patients with non-islet-cell tumor hypoglycemia.

Insulin-like growth factor II (IGF-II) in serum and tumor extracts from five patients with non-islet-cell tumor hypoglycemia (NICTH) has been characterized. These tumors contained large quantities of IGF-II (2.4-14.2 micrograms/g tissues). The serum IGF-II levels in four of five patients were a little high and the serum IGF-I levels in five patients were low. The serum IGF-II/IGF-I ratios in these patients ranged from 24.1 to 64.2, and the values were significantly greater than those in normal subjects (1.7-7.1). When the sera were gel-filtered on a Sephacryl S-200 column under neutral conditions, the proportion of the free form of IGF-II was not increased. However, in four of five patients, an abnormal IGF-II-IGF binding protein complex was found. When serum IGF binding proteins (IGFBPs) were analyzed by Western ligand blotting, serum IGFBP-2 increased in these patients. When the tumor extracts and sera were gel-filtered on a Biogel P-60 column under acidic conditions, the majority of IGF-II in these sera was a big form of IGF-II. As compared to authentic IGF-II, insulin receptor reactivities and IGF-II receptor reactivities of tumor extracted IGF-II increased in two of three patients. These data indicate that in patients with NICTH, heterogenous IGF-II is produced in respect of size and bioactivities, and that the characteristics of IGF binding protein are altered. Thus, to find IGF-II producing tumors among extrapancreatic tumors associated with hypoglycemia, the quality of IGF-II as well as the quantity should be studied.

An insulin-like growth factor II-producing histiocytoma associated with hypoglycemia: Analysis of the peptide, its gene expression, and glucose transporter isoforms

An insulin-like growth factor II (IGF-II)-producing histiocytoma was detected in a patient presenting with the classical findings of tumor-related hypoglycemia (low serum insulin and IGF-I concentrations, glucose intolerance, and only modestly increased serum IGF-II levels). Acid-gel filtration of serum extracts showed a single peak of IGF-II immunoreactivity that emerged at the same site as the 125I-labeled human IGF-II standard. High-performance liquid chromatography (HPLC) analysis of the tumor IGF-II demonstrated that it had an identical retention time to that of recombinant human IGF-II. The tumor IGF-II content was extremely high, messenger RNA (mRNA) for IGF-II showed a 100-fold increase in expression compared with normal human liver tissue. Of special interest, a newly identified exon (hE 1) was shown to be predominantly expressed in the tumor by Northern blot analysis using leader exon-specific rat IGF-II complementary DNA (cDNA) probes. Although the significance of this finding remains uncertain, this is the first evidence of a new transcription unit in the human IGF-II gene. In addition, immunoblotting showed that the levels of the glucose transporters, GLUT1 and GLUT4, in the tumor were low and undetectable, respectively. This finding makes it unlikely that increased glucose consumption by the tumor accounted for the hypoglycemia in this patient. This case report provides an interesting insight into the pathophysiology of tumor-induced hypoglycemia and new evidence of the abnormal regulation of IGF-II gene expression in human tumors.

Expression of insulin-like growth factor II (IGF-II) in human primary liver cancer: mRNA and protein analysis

Insulin-like growth factor II (IGF-II) is a polypeptide growth factor thought to be involved in fetal tissue development. We previously showed an increased expression of IGF-II mRNA in human primary liver cancer. The present investigation was undertaken to characterize the overexpressed IGF-II transcripts and to determine whether they are translated into protein. Two cDNAs with distinct 5' untranslated regions, corresponding to IGF-II transcripts expressed in fetal liver, were isolated from a primary liver cancer. Complete nucleotide sequence analysis showed an identical open reading frame of 540 bp, encoding a predicted polypeptide identical to the IGF-II isolated from serum. An increased synthesis of IGF-II protein was demonstrated by a protein-binding assay in tumorous liver samples, the highest levels being found in primary liver cancers with the highest IGF-II steady state level. By contrast, serum IGF-II content was low in most of primary liver cancer cases analyzed. Altogether, the results indicate reexpression of IGF-II both at the mRNA and protein levels in primary liver cancer. This finding is consistent with IGF-II being a marker of liver cell differentiation. In addition, this growth factor might be involved in liver cancer progression by an autocrine and/or paracrine mechanism.

Serum concentrations of insulin-like growth factor II are not changed by short-term fasting and refeeding.

To determine the factors that regulate insulin-like growth factor II (IGF-II), we raised polyclonal antibodies to this peptide and developed a RIA that measures IGF-II in serum or plasma samples after extraction of IGF-binding proteins by C18 cartridge chromatography. The IGF-II antiserum was highly specific, exhibiting no cross-reactivity with IGF-I or insulin at the highest concentrations tested (10(-6) mol/L). As little as 0.43 micrograms/L IGF-II was detectable, and 50% displacement of tracer occurred at 1.7 microgram/L. The serum IGF-II concentrations of normal adults [mean, 634 +/- 170 (+/- SD) micrograms/L], patients with acromegaly (570 +/- 146 micrograms/L), and patients with hypopituitarism (156 +/- 58 micrograms/L) were similar to those reported by others. In eight obese subjects injected with GH (0.1 mg/kg ideal BW, im, every 48 h for 16 days), serum IGF-II concentrations did not rise significantly, whereas IGF-I concentrations increased 67%. Sixteen normal subjects, within 15% of ideal body weight, were fasted for 5 days on two to four occasions and refed diets of differing protein and calorie contents. Their mean serum IGF-II concentration before fasting (691 +/- 26 micrograms/L) was not significantly different from that after fasting (674 +/- 21 micrograms/L) or after refeeding (641 +/- 20 micrograms/L). In contrast, their mean IGF-I concentration decreased 42% with fasting and rose with refeeding. Unlike IGF-I, serum IGF-II concentrations do not appear to be regulated by short term changes in nutritional status. It is clear from this study and others that IGF-II and IGF-I are regulated differently despite their structural homology and the similarity of their actions in vitro.

Determination of circulating levels of insulin-like growth factor II (IGF-II) in swine

A heterologous radioimmunoassay system was developed for the determination of circulating IGF-II concentrations in swine. The assay utilized a monoclonal antibody against human IGF-II (Amano Intl. Ez, VA) and bovine IGF-II (Monsanto Co., MO) as the cold standard and iodinated ligand. Serial dilutions of acid-ethanol extracted normal swine sera resulted in a curve which was parallel to the bovine IGF-II standard curve. Recovery of unlabeled standard added to extracted swine sera was 101%. Neither IGF-I nor insulin were capable of cross-reacting in this assay at levels up to 100-fold excess. Using this assay, serum IGF-II levels were determined to be significantly lower when subnormal growth hormone (GH) levels existed such as in hypophysectomized swine. However, in contrast to serum IGF-I concentrations, supranormal levels of porcine GH (pGH) did not elevate serum IGF-II concentrations after 13 wk of treatment in 25 kg hogs (initial body wt). In addition, serum IGF-II levels were reduced in fasted swine, despite a significant increase in circulating GH concentrations. Thus, although normal concentrations of GH are required for maintenance of physiological levels of IGF-II in swine, the mechanism for stimulation of IGF-II secretion is less GH-dependent than IGF-I.

Somatomedin-C/insulin-like growth factor-I and insulin-like growth factor-II mRNAs in rat fetal and adult tissues.

Somatomedin-C or insulin-like growth factor I (Sm-C/IGF-I) and insulin-like growth factor II (IGF-II) have been implicated in the regulation of fetal growth and development. In the present study 32P-labeled complementary DNA probes encoding human and mouse Sm-C/IGF-I and human IGF-II were used in Northern blot hybridizations to analyse rat Sm-C/IGF-I and IGF-II mRNAs in poly(A+) RNAs from intestine, liver, lung, and brain of adult rats and fetal rats between day 14 and 17 of gestation. In fetal rats, all four tissues contained a major mRNA of 1.7 kilobases (kb) that hybridized with the human Sm-C/IGF-I cDNA and mRNAs of 7.5, 4.7, 1.7, and 1.2 kb that hybridized with the mouse Sm-C/IGF-I cDNA. Adult rat intestine, liver, and lung also contained these mRNAs but Sm-C/IGF-I mRNAs were not detected in adult rat brain. These findings provide direct support for prior observations that multiple tissues in the fetus synthesize immunoreactive Sm-C/IGF-I and imply a role for Sm-C/IGF-I in fetal development as well as postnatally. The abundance of a 7.5-kb Sm-C/IGF-I mRNA in poly(A+) RNAs from adult rat liver was 10-50-fold higher than in other adult rat tissues which provides further evidence that in the adult rat the liver is a major site of Sm-C/IGF-I synthesis and source of circulating Sm-C/IGF-I. Multiple IGF-II mRNAs of estimated sizes 4.7, 3.9, 2.2, 1.75, and 1.2 kb were observed in fetal rat intestine, liver, lung, and brain. The 4.7- and 3.9-kb mRNAs were the major hybridizing IGF-II mRNAs in all fetal tissues. Higher abundance of IGF-II mRNAs in rat fetal tissues compared with adult tissues supports prior hypotheses, based on serum IGF-II concentrations, that IGF-II is predominantly a fetal somatomedin. IGF-II mRNAs are present, however, in some poly(A+) RNAs from adult rat tissues. The brain was the only tissue in the adult rat where the 4.7- and 3.9-kb IGF-II mRNAs were consistently detected. Some samples of adult rat intestine contained the 4.7- and 3.9-kb IGF-II mRNAs and some samples of adult liver and lung contained the 4.7-kb mRNA. These findings suggest that a role for IGF-II in the adult rat, particularly in the central nervous system, cannot be excluded.