Autocrine regulation of human tumor cell proliferation by insulin-like growth factor II: an in-vitro model.

We have shown that a pleomorphic cell line of abnormal human karyotype derived from a stomach carcinoma (LIM-1839) proliferates in serum-free medium, expresses insulin-like growth factor II (IGF-II) mRNA, and secretes IGF-II (up to 56 ng/ml in serum-free conditioned medium, as measured in a rat liver RRA. No detectable levels of IGF-I can be measured in serum-free conditioned medium by RIA. These cells also secrete IGF-binding proteins, detected by a charcoal adsorption assay. The release of IGF-II and IGF binding proteins into serum-free conditioned medium (1.7 pmol/10(6) cells.24 h and 0.8 pmol binding sites/10(6) cells.24 h for 3 days, respectively) is inhibited 80% by cycloheximide (10 micrograms/ml). The LIM-1839 cells have type I and type II IGF receptors, determined by affinity cross-linking and competition binding studies. These cells proliferated 1.6-fold over 4 days in serum-free medium, with fresh medium changes on days 0 and 2: their growth was inhibited 56% by 40 micrograms/ml Sm 1.2, a monoclonal antibody which recognizes IGF-I and IGF-II. The addition of 20 and 50 ng/ml multiplication stimulating activity (rat IGF-II) caused 1.8- and 1.7-fold increases in cell growth between days 0 and 4 compared to controls, while [Thr59]IGF-I, at 20 and 50 ng/ml, caused 1.6- and 2.0-fold increases. Insulin, at 2 and 10 micrograms/ml, had no significant effect. The stimulatory effects of endogenous and exogenous IGFs on LIM-1839 cell proliferation were inhibited by a monoclonal antibody to the type I IGF receptor, alpha IR-3. These results suggest that the LIM-1839 cells are biologically responsive to endogenously produced IGF-II, and may thereby provide an in vitro model for autocrine regulation of human tumor growth by IGF-II.     

Clinical features of insulin-like growth factor-II producing non-islet-cell tumor hypoglycemia.

In some patients with non-islet-cell tumor hypoglycemia (NICTH), a high molecular weight form of IGF-II (big IGF-II) derived from tumors is present in the circulation and might be associated with recurrent hypoglycemia. In this study, in order to survey the clinical characteristics of patients with IGF-II producing NICTH, we analyzed the medical records of 78 patients with NICTH (M/F 44/34, age 62+/-1.8, range; 9-86 years.) whose serum contained a large amount of big IGF-II. Hepatocellular carcinoma and gastric carcinoma were the most common causes of NICTH. The diameters of the tumors were more than 10 cm in 70% of the patients. Basal immunoreactive insulin (IRI) levels were less than 3 microU/dl in 79% of the patients. Hypoglycemic attack was the onset of disease in 31 of 65 cases (48%), but the tumor was revealed prior to the occurrence of hypoglycemia in 34 cases (52%). Twenty-five of 47 (53%) patients had decreased serum potassium levels. These data suggested that hypoinsulinemic hypoglycemia associated with the presence of a large tumor supports the diagnosis of IGF-II producing NICTH. Hypokalemia was associated with hypoglycemia in some patients. The BMI (21.4+/-0.6 kg/m2) and serum total protein levels (6.6+/-0.1g/dl) were preserved at the occurrence of first hypoglycemic attack suggesting that malnutrition might not be the main cause of hypoglycemia in most patients.     

Overexpression of insulin-like growth factor-II in transgenic mice is associated with pancreatic islet cell hyperplasia

We have used an insulin-like growth factor (IGF)-II transgenic mouse model in which mouse IGF-II is widely overexpressed, resulting in increased fetal size and selective organ overgrowth, to investigate the effects on the development of the endocrine pancreas. Fetuses examined on day 19.5-20 of gestation had significantly elevated circulating levels of IGF-II, compared with control mice. The pancreatic islets in transgenic animals were of irregular shape and had a mean area five times greater than in controls, whereas the mean number of islets per tissue section was not altered. The size of individual endocrine cells was not altered. Although the islets in animals expressing the IGF-II transgene were considerably larger, immunohistochemistry for insulin and glucagon showed that the relative proportion of beta-cells was significantly less, and that of alpha-cells was higher. Normal islet morphology was disrupted, with alpha-cells appearing in small groups within the islets, as well as on the periphery, whereas beta-cells were often seen at the edge of the islets. Twice as many islet cells (21.9% vs. 11.4%) were involved in cell replication, detected by the presence of immunoreactive proliferating cell nuclear antigen, in pancreata from transgenic mice vs. controls, whereas the number of cells undergoing apoptosis was significantly reduced. Abundant IGF-II messenger RNAwas found within the islets of transgenic animals by in situ hybridization, and the relative area of islets demonstrating immunoreactive IGF-II was significantly greater. Immunoreactive IGF-I was much less abundant and was further reduced in islets of transgenic animals. The area of islets immunopositive for IGF binding protein-2 was unaltered. Despite the presence of islet hyperplasia, circulating insulin levels and serum glucose levels were not significantly different between transgenic and control mice. These results show that an overexpression of IGF-II in fetal life has a profound effect on islet morphology and causes islet hyperplasia while reducing the attrition of islet cells by apoptosis.     

Autocrine stimulation by insulin-like growth factor 1 and insulin-like growth factor 2 mediates chondrocyte survival in vitro

OBJECTIVE: To determine the role of autocrine stimulation by insulin-like growth factor 1 (IGF-1) and IGF-2 in mediating chondrocyte survival and to determine whether chondrocytes from older individuals are more susceptible to cell death when IGF action is blocked. METHODS: Survival was assessed in human and monkey chondrocytes cultured in suspension in alginate under serum-free conditions. The role of IGFs in mediating survival was determined by treating cultures with neutralizing antibodies to IGF-1 and IGF-2, an antibody that blocks the type 1 IGF receptor, and antisense oligonucleotides to inhibit IGF-1 production. Survival was measured in chondrocyte cultures from young and old adult monkeys in the presence and absence of the IGF receptor blocking antibody and ceramide to induce cell death. RESULTS: Cell survival of >90% was noted when chondrocytes were cultured for as long as 107 days in alginate in a supplemented serum-free medium. Compared with controls, survival was significantly reduced by treatment with neutralizing antibodies to IGF-1 (25% cell death), neutralizing antibodies to IGF-2 (18% cell death), antibody to the IGF receptor (45% cell death), and IGF-1 antisense oligonucleotides (28% cell death). Cell death from inhibition of the type 1 IGF receptor was associated with an increase in caspase 3 activity and with positive DNA fragmentation, consistent with apoptotic cell death. Chondrocytes from old adult monkeys were more susceptible to cell death than were those from young adult monkeys when the IGF receptor was blocked and cell death was further stimulated by ceramide. CONCLUSION: Autocrine production of IGFs helps to maintain chondrocyte survival in vitro and could play a similar role in vivo. With aging, chondrocytes may become more susceptible to factors that induce cell death.     

Effects of alpha-interferon on insulin-like growth factor-I, insulin-like growth factor-II and insulin-like growth factor binding protein-3 secretion by a human lung cancer cell line in vitro

The aim of our study was to evaluate the effect of alpha-interferon (alpha-IFN) on cell growth and on the different IGF system components in a human non-small cell lung cancer line (Calu-6) in vitro. Our results confirm the release of IGF-I and IGF-II by these cells. The amount of IGF-II in conditioned media (10.25 +/- 3.95 nM/10(6) cells, mean +/- SE) was more than 10-fold higher than that of IGF-I. alpha-IFN treatment reduced IGF-II levels in the media, with a maximal effect between 1 and 10 U/ml (delta% of control: -31 and -55%, respectively, p < 0.05). IGF-I was significantly reduced at 0.5 U/ml (p < 0.01). No difference, however, was observed in IGF mRNA expression between untreated and alpha-IFN treated cells. An increase in IGF-I and IGF-II intracellular levels in alpha-IFN treated cultures was observed, suggesting that alpha-IFN can regulate the transfer of these peptides into the cells. Furthermore, IGF type-I and particularly type-lI receptor expression was increased after alpha-IFN treatment. IGFBP-3 was detected only in trace amounts in the conditioned media; however, it showed an increase after alpha-IFN treatment (+110% at 1 U/ml). IGFBP-3 mRNA expression showed a slight increase after treatment with 1 and 10 U/ml. alpha-IFN (1-10 U/ml) reduced the stimulatory effect of IGF-I on cell replication (p < 0.01), inhibited (p < 0.01) cell replication in untreated and in fetal calf serum (FCS)-stimulated cells, and increased apoptosis in Calu-6 cells. Our data suggest that alpha-IFN may exert its effects at the cellular level in part through modification of the local IGF system.     

Production of insulin-like growth factor-II by human fetal pancreas in culture

Insulin-like growth factor-II (IGF-II) is a polypeptide hormone thought to be involved in fetal development because of its wide distribution in fetal tissues and its presence in the fetal circulation. We have developed a highly sensitive radioreceptor assay for IGF-II using rat liver microsomal membranes and have used this assay to test for the presence of IGF-II in the human fetal pancreas and the release of IGF-II by the human fetal pancreas in organ culture. IGF-II was present in extracts of pancreatic tissue (0.056 +/- 0.012 pmol/mg tissue, n = 5) and was released in culture at the rate of 0.027-0.134 pmol/mg tissue per day with release being maintained for at least 3 weeks in culture. The rate of release was not affected by the gestational age of the fetus over 14 to 20 weeks but was significantly related to the rate of insulin release (r = 0.712, P less than 0.001, n = 34). Chronic exposure to 12-0-tetradecanoylphorbol-13-acetate (TPA), which inhibits insulin release in the human fetal pancreas, caused an 85% drop in IGF-II production, which was reversed when TPA was removed. These studies demonstrate that IGF-II is produced by the human fetal pancreas in a pattern similar to that of insulin. We suggest that control of IGF-II release, like that of insulin, may involve protein-kinase C and that IGF-II may have a paracrine or autocrine role in the development of fetal pancreatic function.     

Metabolic clearance of insulin-like growth factor-II in sheep

The metabolic clearance of ovine insulin-like growth factor-II (IGF-II) was examined in sheep using 131I-labelled IGF-II. Following i.v. administration the tracer was distributed in a volume similar to that of the vascular space (58.5 +/- 3.3 ml/kg; mean +/- S.E.M., n = 5) and demonstrated a triphasic pattern of clearance. Size-exclusion chromatography of a plasma sample collected 1 min after injection revealed peaks of radioactivity corresponding to hormone complexed to binding proteins of 150 and 40-50 kDa (relative abundance 21 and 65% respectively), a high molecular weight binding protein (greater than 200 kDa; 5%) and 'free' tracer (9%). Chromatography of sequential plasma samples revealed different patterns of clearance for these constituents. Half-lives of 131I-labelled IGF-II complexed to the 150 and 40-50 kDa binding proteins, as calculated from rate constants for their decay, were 351 +/- 30 and 9.6 +/- 1.8 min respectively (n = 5). These differ markedly from estimates for the clearance of IGF-I (545 +/- 25 min, n = 8, and 34 +/- 2.3 min, n = 6) associated with carrier proteins of the same apparent molecular weights. This was reflected in calculated metabolic clearance rates for IGF-I (3.9 +/- 0.5 ml/min) and IGF-II (7.8 +/- 1.0 ml/min). Chromatography also revealed that free IGF-II was reduced to negligible levels by 12 min. In contrast, radioactivity eluting in the position expected for the greater than 200 kDa binding protein was cleared from the circulation very slowly.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reactivation of the insulin-like growth factor-Ⅱ signaling pathway in human hepatocellular carcinoma

Constitutive activation of the insulin-like growth factor （IGF）-signaling axis is frequently observed in human hepatocellular carcinoma （HCC）. Especially the overexpression of the fetal growth factor IGF-Ⅱ, IGF-Ⅰ receptor （IGF-IR）, and cytoplasmic downstream effectors such as insulin-receptor substrates （IRS） contribute to proliferation, anti-apoptosis, and invasive behavior. This review focuses on the relevant alterations in this signaling pathway and independent in vivo models that support the central role IGF-Ⅱ signaling during HCC development and progression. Since this pathway has become the center of interest as a target for potential anti-cancer therapy in many types of malignancies, various experimental strategies have been developed, including neutralizing antibodies and selective receptor kinase inhibitors, with respect to the specific and efficient reduction of oncogenic IGF- Ⅱ/IGF-IR-signaling.     

Alphavbeta3 integrin signaling pathway is involved in insulin-like growth factor I-stimulated human extravillous trophoblast cell migration

IGF-I and -II provide paracrine and autocrine stimuli, respectively, for extravillous trophoblast (EVT) cell migration. This study examined the role of alpha(v)beta(3) integrin and its signaling pathway in IGF-I-stimulated migration. Migration assays were conducted using cultured EVT cells treated with or without IGF-I in the presence or absence of alphaIR3, Arg-Gly-Asp (RGD) hexapeptide, and antibody against alpha(v)beta(3) integrin. Morphological changes were studied using scanning electron microscopy. Colocalization of alpha(5)beta(1) alpha(v)beta(3) integrins, vinculin, focal adhesion kinase, and paxillin were determined by immuno-cytochemistry and immunoblotting. The results showed that IGF-I could stimulate EVT cell migration in a time- and dose-dependent manner and addition of alphaIR3, Arg-Gly-Asp hexapeptide, and antibody against alpha(v)beta(3) integrin attenuated the IGF-I migratory effect. Scanning electron microscopy images revealed that IGF-I promoted lamellipodia formation. Immunostaining and immunoblotting exhibited the colocalization of alpha(v)beta(3) integrin with phosphorylated focal adhesion kinase, paxillin, and vinculin at focal adhesions after IGF-I treatment. Immunoblotting demonstrated an increase in focal adhesion kinase and paxillin tyrosine phosphorylation followed by tyrosine phosphorylation of IGF-I receptor in a time- and dose-dependent manner. These findings indicated alpha(v)beta(3) integrin localization in the core of focal adhesions of EVT cells and that alpha(v)beta(3) integrin signaling pathways are activated in IGF-I-mediated migration of these cells.     

Regulation of insulin-like growth factor-II production in bone cultures

Although bone matrix is a rich source of insulin-like growth factor-II (IGF-II), little is known about the regulation of its synthesis by bone cells. This is due in part to the lack of simple and reliable assays to measure IGF-II. We have developed a method to dissociate IGF-II from its binding proteins by acidification and ultrafiltration, and quantitated IGF-II by RIA in 24- to 72-h cultures of 21-day-old fetal rat calvariae. The coefficient of variation of the assay was 13.8% or less; the recovery of IGF-II was 30-50%, and IGF-I cross-reacted 1% or less in the assay compared to IGF-II standards. The IGF-II concentrations in calvarial culture medium were in the 1- to 3-nM range, and these levels were suppressed by cycloheximide (3.6 microM) by almost 80%. Continuous treatment with placental lactogen, PTH, GH, insulin, or T3 did not modify IGF-II concentrations in 24- to 72-h cultures. Treatment with 17 beta-estradiol, testosterone, and 1,25-dihydroxyvitamin D3 also had no effect on IGF-II levels, whereas cortisol (10-100 nM) decreased IGF-II concentrations by 20-50%. Transforming growth factor-beta, prostaglandin E2, and platelet-derived growth factor BB did not alter IGF-II levels, and basic fibroblast growth factor (0.06-6 nM) for 72 h decreased calvarial IGF-II by 30-50%. In conclusion, 21-day-old fetal rat calvariae secrete IGF-II, and its concentration in culture medium is decreased by cortisol and basic fibroblast growth factor.     

Effects of insulin-like growth factor-II on growth hormone release from human somatotrophinoma cells in vitro

Insulin-like growth factor-I (IGF-I) and IGF-II receptors have previously been demonstrated on membranes prepared from human somatotrophinomas. IGF-I has been shown to have a variable effect on GH secretion by these tumours in vitro. The effects of purified IGF-II on GH secretion have not been described. We have studied the direct actions of human recombinant IGF-II on GH release from eight somatotrophinomas cultured in vitro. Somatotrophinoma cells were cultured as monolayers at a density of 10(5) cells/0.5 ml. Treatment with IGF-II for 4 and 24 h resulted in discrete inhibitory effects on GH release from two tumours (tumour 5: 4 h, IGF-II 0.5 nmol/l; tumour 2; 24 h, IGF-II 1 nmol/l). Treatment with IGF-II for 24 h resulted in significant inhibitory effects on GH release from one tumour over a range of concentrations tested (IGF-II 0.5-10 nmol/l). Addition of human GH-releasing factor (hGRF) (1-44) (20 nmol/l) for 4 and 24 h resulted in stimulation of GH release by five tumours. Two tumours demonstrated significant inhibitory effects of IGF-II on GRF-stimulated GH release (tumour 2: 24 h, IGF-II 1-5 nmol/l; tumour 3; 4 h, IGF-II 5 nmol/l; 24 h, IGF-II 0.5-50 nmol/l). These data emphasize the heterogeneity of somatotrophinomas in terms of their response to modulators of GH secretion. IGF-II does not appear to have a modulatory role on GH release by most somatotrophinomas.     

The role of insulin-like growth factor-II in cancer growth and progression evidenced by the use of ribozymes and prostate cancer progression models.

Towards understanding the IGF system during cancer growth and progression, progressive prostate cancer models, such as SV40 large T antigen immortalized human prostate epithelial cells (P69, M2182, M2205, and M12) and LNCaP sublines (C4, C4-2, and C4-2B4), were used. IGF-II mRNA levels progressively increase as prostate cancer cells become more tumorigenic and metastatic, suggesting that IGF-II contributes in part to prostate cancer progression. The role of IGF-II in cancer cell growth was evaluated in LNCaP, PC3, and M12 prostate cancer cell lines and MCF-7 breast cancer cell line by ribozyme/antisense strategies which were previously shown to suppress endogenous IGF-II expression and cell growth in PC-3 cells [Xu et al., Endocrinol 140 (1999) 2134]. Retroviral mediated transient expression of IGF-II-specific ribozyme (RZ) caused extensive cell death. In stably cloned cell lines, both RZ and mutant ribozyme (MRZ) inhibited cancer cell growth, suggesting that antisense effects of MRZ may be sufficient for cell growth inhibition. These results confirm an important role of IGF-II in cancer cell growth and progression, and support further development of gene therapy targeting IGF-II.     

Resveratrol regulates insulin-like growth factor-II in breast cancer cells

IGF-II is a potent mitogen and inhibitor of apoptosis in breast cancer. Regulation of IGF-II is complex and includes inhibition by tumor suppressors, stimulation by oncogenes, and imprinting and hormonal regulation by estrogens. Resveratrol (RSV) is a phytoestrogen that displays estrogen-like agonistic and antagonistic activity. Recent studies have shown that RSV inhibits the growth of breast cancer cells and may represent a potent agent in chemopreventive therapy. Because 17beta-estradiol regulates IGF-II, we hypothesized that RSV may have a similar effect on IGF-II. The present study was designed to examine whether: 1) RSV modulates IGF-II in breast cancer cells; 2) regulation of IGF-II by RSV is dependent on the ER status; and 3) IGF-II (not IGF-I) mediates RSV effects on breast cancer cells. Treatment of MCF-7 and T47D cells with RSV (10(-6) M) caused stimulation of precursor IGF-II mRNA and protein; this effect was blocked by coincubation with 17beta-estradiol (10(-9) M). Cell growth stimulated by RSV (10(-6) M) was blocked by addition of a blocking IGF-I receptor antibody, or the antiestrogen tamoxifen (10(-7) M). In contrast, RSV treatment (10(-4) M) inhibited IGF-II secretion and cell growth in MCF-7 and T47D cells. No increase in IGF-II levels is seen in estrogen receptor (-) MCF-10 cells, even though cell growth was inhibited by RSV 10(-4) M and precursor IGF-II blocked the inhibitory effect of resveratrol. No change in IGF-I was observed with RSV treatment (10(-6) to 10(-4) M). Our study demonstrates that RSV regulates IGF-II and that IGF-II mediates RSV effect on cell survival and growth in breast cancer cells.     

Autocrine human growth hormone promotes tumor angiogenesis in mammary carcinoma

Accumulating literature implicates pathological angiogenesis and lymphangiogenesis as playing key roles in tumor progression. Autocrine human growth hormone (hGH) is a wild-type orthotopically expressed oncogene for the human mammary epithelial cell. Herein we demonstrate that autocrine hGH expression in the human mammary carcinoma cell line MCF-7 stimulated the survival, proliferation, migration, and invasion of a human microvascular endothelial cell line (HMEC-1). Autocrine/paracrine hGH secreted from mammary carcinoma cells also promoted HMEC-1 in vitro tube formation as a consequence of increased vascular endothelial growth factor-A (VEGF-A) expression. Semiquantitative RT-PCR analysis demonstrated that HMEC-1 cells express both hGH and the hGH receptor (hGHR). Functional antagonism of HMEC-1-derived hGH reduced HMEC-1 survival, proliferation, migration/invasion, and tube formation in vitro. Autocrine/paracrine hGH secreted by mammary carcinoma cells increased tumor blood and lymphatic microvessel density in a xenograft model of human mammary carcinoma. Autocrine hGH is therefore a potential master regulator of tumor neovascularization, coordinating two critical processes in mammary neoplastic progression, angiogenesis and lymphangiogenesis. Consideration of hGH antagonism to inhibit angiogenic processes in mammary carcinoma is therefore warranted.     

Autocrine human growth hormone enhancement of human mammary carcinoma cell spreading is Jak2 dependent

We investigated the role of autocrine production of human (h) GH in the attachment and spreading of mammary carcinoma cells in vitro. We used a previously described model system for the study of the autocrine/paracrine role of GH in which the hGH gene (MCF-hGH) or a translation-deficient hGH gene (MCF-MUT) was stably transfected into MCF-7 cells. No differences in attachment to a collagen matrix between MCF-hGH and MCF-MUT cells were observed in either serum-free medium (SFM) or medium containing exogenous hGH, 5% serum, or 10% serum. In contrast, MCF-hGH cells spread more rapidly on a collagen matrix than did MCF-MUT cells. Exogenous hGH and 10% serum interacted with autocrine production of hGH in an additive manner to increase cell spreading. MCF-hGH cells formed filipodia and stress fibers earlier than MCF-MUT cells during the process of cell spreading and possessed marked differences in morphology after spreading. MCF-MUT cells displayed uniform and symmetrical formation of stress fibers, whereas MCF-hGH cells displayed irregular and elongated stress fiber formation. The level of cytoplasmic phosphotyrosine was increased in MCF-hGH compared with MCF-MUT cells during spreading and displayed colocalization with Janus kinase 2 (JAK2). Basal JAK2 tyrosine phosphorylation was increased, and it increased further on spreading in MCF-hGH cells compared with MCF-MUT cells. Transient transfection of JAK2 complementary DNA resulted in interaction with autocrine hGH to increase the rate of cell spreading in MCF-hGH cells compared with MCF-MUT cells. Treatment with a selective JAK2 tyrosine kinase inhibitor (AG 490) reduced the rate of MCF-hGH cell spreading to the rate of MCF-MUT cell spreading. Thus, we conclude that autocrine production of hGH enhances the rate of mammary carcinoma cell spreading in a JAK2-dependent manner.     

Autocrine growth stimulation of a human T-cell lymphoma line by interleukin 2.

The ability of tumor cells to produce and to respond to their own growth factor (autocrine secretion) may be of importance for their growth. We describe a human tumor cell line regulated by an autocrine secretion of the growth factor interleukin 2 (IL-2). This T-lymphocyte cell line, IARC 301, was established from a patient with a T-cell lymphoma in the absence of any added specific growth factor. It constitutively expresses biologically functional high-affinity cell-surface receptors for IL-2 as shown by the binding of both radiolabeled purified IL-2 and monoclonal antibodies to IL-2 receptors. In addition, it synthesizes IL-2, which is bound to cell surface receptors. Monoclonal antibodies directed against either IL-2 or the IL-2 receptor block IARC 301 cell growth. These findings demonstrate that the proliferation of this tumor cell line is mediated by an autocrine pathway involving endogenous IL-2 production and its binding to cell surface receptors.     

Fibroblast cell interactions with human melanoma cells affect tumor cell growth as a function of tumor progression.

It is known from a variety of experimental systems that the ability of tumor cells to grow locally and metastasize can be affected by the presence of adjacent normal tissues and cells, particularly mesenchymally derived stromal cells such as fibroblasts. However, the comparative influence of such normal cell-tumor cell interactions on tumor behavior has not been thoroughly investigated from the perspective of different stages of tumor progression. To address this question we assessed the influence of normal dermal fibroblasts on the growth of human melanoma cells obtained from different stages of tumor progression. We found that the in vitro growth of most (4 out of 5) melanoma cell lines derived from early-stage radial growth phase or vertical growth phase metastatically incompetent primary lesions is repressed by coculture with normal dermal fibroblasts, suggesting that negative homeostatic growth controls are still operative on melanoma cells from early stages of disease. On the other hand, 9 out of 11 melanoma cell lines derived from advanced metastatically competent vertical growth phase primary lesions, or from distant metastases, were found to be consistently stimulated to grow in the presence of dermal fibroblasts. Evidence was obtained to show that this discriminatory fibroblastic influence is mediated by soluble inhibitory and stimulatory growth factor(s). Taken together, these results indicate that fibroblast-derived signals can have antithetical growth effects on metastatic versus metastatically incompetent tumor subpopulations. This resultant conversion in responsiveness to host tissue environmental factors may confer upon small numbers of metastatically competent cells a growth advantage, allowing them to escape local growth constraints both in the primary tumor site and at distant ectopic tissue sites.     

Serum insulin-like growth factor-II as a serologic marker of small hepatocellular carcinoma

OBJECTIVE: Alpha-fetoprotein (AFP) is not a useful tumor marker for diagnosis of small hepatocellular carcinoma (HCC). There is over-expression of insulin-like growth factor (IGF)-II in HCC tissue. This study investigates the diagnostic application of IGF-II in small HCC. MATERIAL AND METHODS: Serum levels of IGF-II and AFP were determined in 41 patients with small cirrhotic HCC (< or = 3 cm), 41 sex- and age-matched patients with cirrhosis alone (LC), and 41 healthy adults. The optimal cut-off values for diagnosing HCC were determined with receiver operating characteristics (ROC) curve. RESULTS: Both IGF-II and AFP levels in HCC were higher than those in LC patients or controls (each p = 0.0001). The IGF-II levels in LC patients were lower than those in controls (p = 0.001). In HCC patients, multivariate analysis indicated that that both IGF-II (odds ratio, 4.54; 95% confidence interval, 2.15-9.55; p = 0.0001) and AFP (odds ratio, 1.05; 95% confidence interval, 1.01-1.08; p = 0.003) were found to be associated with an increased risk of presence of HCC. The optimal cut-off values of IGF-II (4.1 mg/g prealbumin) and AFP (50 ng/ml) were determined with ROC curves. The sensitivity, specificity, and diagnostic accuracy values for IGF-II were 63%, 90%, and 70%, respectively. Those for AFP were 44%, 95%, and 70%, respectively. Determination of both markers in parallel significantly increase the diagnostic accuracy (88%) and sensitivity (80%), with a high specificity (90%). CONCLUSIONS: Serum IGF-II level can be used as an independent serologic marker or a complementary tumor marker to AFP for diagnosis of small HCC.     

Differential effect of growth hormone and insulin-like growth factor-I, insulin-like growth factor-II, and insulin on Ig production and growth in human plasma cells

The effect of human growth hormone (GH) and insulin-like growth factor- I (IGF-I), IGF-II, and insulin on human plasma cell responses was studied. GH enhanced Ig production and thymidine uptake in the human plasma cell lines, IM-9 and AF-10. IGF-I, but not IGF-II or insulin, also enhanced Ig production and proliferation in them. However, enhancement by GH was not mediated by IGF-I, because enhancement was blocked by anti-GH antibody (Ab), but not by Ab to IGF-I or IGF-I receptor. Conversely, the enhancement by IGF-I was blocked by either Ab to IGF-I or IGF-I receptor, but not by anti-GH Ab. GH and IGF-I also enhanced production of IgG1, IgG2, IgG3, IgG4, IgA1, IgA2, and IgM and thymidine uptake in PCA-1+ plasma cells generated in vitro. Again, enhancement by GH was specifically blocked by anti-GH Ab, whereas enhancement by IGF-I was specifically blocked by either Ab to IGF-I or IGF-I receptor. These results indicate that GH and IGF-I may play important roles in plasma cell responses.