The IGF-I receptor in cell growth, transformation and apoptosis.
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Animals↗
Biomedical subjects
B Valentinis
Publications and source records attributed to B Valentinis.
Insulin-like growth factor (IGF)-binding protein-3 induces apoptosis and mediates the effects of transforming growth factor-beta1 on programmed cell death through a p53- and IGF-independent mechanism.
Insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) is known to block IGF action and inhibit cell growth. IGFBP-3 is thought to act by sequestering free IGFs or, possibly, act via a novel IGF-independent mechanism. Supporting its role as a primary growth inhibitor, IGFBP-3 production has been shown to be increased by cell growth-inhibitory agents, such as transforming growth factor-beta (TGF-beta), and the tumor suppressor gene p53. In this paper, we demonstrate, for the first time, a novel function of IGFBP-3 as an apoptosis-inducing agent and show that this action is mediated through an IGF.IGF receptor-independent pathway. In the p53 negative prostate cancer cell line, PC-3, the addition of recombinant IGFBP-3 resulted in a dose-dependent induction of apoptosis. 125I-IGFBP-3 bound with high affinity to specific proteins in PC-3 cell lysates and plasma membrane preparations. These membrane-associated molecules may serve as receptors that mediate the direct effect of IGFBP-3 on apoptosis. In addition, in an IGF receptor-negative mouse fibroblast cell line, treatment with recombinant IGFBP-3 as well as transfection of the IGFBP-3 gene induced apoptosis, suggesting that neither IGFs nor IGF receptors are required for this action. Furthermore, treatment with TGF-beta1, a known apoptosis-inducing agent, resulted in the induction of IGFBP-3 expression 6-12 h before the onset of apoptosis. This effect of TGF-beta1 was prevented by co-treatment with IGFBP-3-neutralizing antibodies or IGFBP-3-specific antisense thiolated oligonucleotides. These findings suggest that IGFBP-3 induces apoptosis through a novel pathway independent of either p53 or the IGF.IGF receptor-mediated cell survival pathway and that IGFBP-3 mediates TGF-beta1 induced apoptosis in PC-3 cells.
Animals↗
Insulin-like growth factor II stimulates cell proliferation through the insulin receptor.
R- cells are 3T3-like fibroblasts generated from mouse embryos nullizygous for a targeted disruption of the genes encoding the type 1 insulin-like growth factor (IGF) receptor (IGF1R). These cells fail to proliferate in serum-free medium supplemented with purified growth factors, in contrast to their wild-type counterparts. However, when R- cells overexpress the insulin receptor from a stably integrated plasmid, R-/IR cells, they become capable of growing in serum-free medium supplemented solely with insulin or IGF-II, but not with IGF-I. Moreover, the introduction into R-/IR cells of an additional plasmid expressing IGF-II causes these cells to proliferate in serum-free medium without growth factor supplementation. From these results, we conclude that IGF-II can stimulate cell proliferation not only through its cognate IGF1R but also through the insulin receptor.
3T3 Cells↗
The role of the IGF-I receptor in apoptosis.
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Animals↗
Insulin-like growth factor I receptor signaling in transformation by src oncogenes.
R- cells, a line of mouse embryo fibroblasts with a targeted disruption of the insulin-like growth factor I (IGF-I) receptor genes, are refractory to transformation by several viral and cellular oncogenes. Using colony formation in soft agar as a measure of full transformation, we report here that R- cells can be transformed by v-src, although they still cannot be transformed by the activated c-src527 (mutation at tyrosine 527 to phenylalanine), which readily transforms mouse embryo cells with a wild-type number of IGF-I receptors (W cells). Although v-src is a more potent inducer of tyrosine phosphorylation than c-src527, the extent of phosphorylation of either insulin receptor substrate 1 or Shc, two of the major substrates of the IGF-I receptor, does not seem sufficiently different to explain the qualitative difference in soft agar growth. v-src, however, is considerably more efficient than c-src527 in its ability to tyrosyl phosphorylate, in R- cells, the focal adhesion kinase, Stat1, and p130cas. These results indicate that v-src, but not c-src527, can bypass the requirement for a functional IGF-I receptor in the full transformation of mouse embryo fibroblasts and suggest that qualitative and quantitative differences between the two oncogenes can be used to identify some of the signals relevant to the mechanism(s) of transformation.
3T3 Cells↗
The IGF-I receptor protects tumor cells from apoptosis induced by high concentrations of serum.
High concentrations of fetal bovine serum (FBS) induce apoptosis of cells in culture. A decrease in the number of insulin-like growth factor I receptors (IGF-IR) sensitizes the cells to serum-induced apoptosis. Autophosphorylation of the IGR-IR is not affected by high serum. These results may explain why the targeting of the IGF-IR renders tumor cells much more sensitive to apoptosis in vivo than in vitro.
Animals↗
Grb10: A new substrate of the insulin-like growth factor I receptor.
Using the yeast two-hybrid system, we have isolated a new substrate of the insulin-like growth factor I receptor (IGF-IR), identified as Grb10, a member of the family of SH2 domain proteins. With the help of several mutants of the IGF-IR, we have mapped the binding site of Grb10 between amino acids 1229 and 1245 of the receptor, a sequence that is dispensable for the mitogenic activity of the IGF-IR. Grb10 coprecipitates with the IGF-IR in cell lysates and is probably involved in the regulation of its activity.
Binding Sites↗
p53 expression, DNA content and cell proliferation in primary and synchronous metastatic lesions from ovarian surface epithelial-stromal tumours.
The aim of this study was to investigate biological heterogeneity between primary and metastatic ovarian cancer lesions from individual patients as a means of elucidating steps in clinical progression. Cancer tissue from 61 untreated patients with ovarian surface epithelial-stromal tumours was examined. p53 expression detected immunocytochemically by the PAb1801 antibody, DNA content evaluated by flow cytometry, and cell proliferation evaluated as the [3H]thymidine labelling index were investigated in primary tumours and corresponding synchronous metastases. The frequency of p53 positivity was similar in primary (62%) and metastatic (66%) sites, with an agreement between the two lesions from the same patient in 97% of the cases. Similarly, aneuploidy frequency (80%) and DNA indices were superimposable in primary and metastatic lesions from the same patient, with a 94% agreement. The frequency of aneuploidy was higher in p53-positive than in p53-negative lesions. An overall poor agreement (rs = 0.44) was observed for proliferative activity of primary and metastatic lesions, due to a heterogeneous profile in omental with respect to primary tumours, which was mainly evident in p53-positive cancers. Conversely, cell proliferation of peritoneal, abdominal and pelvic lesions was qualitatively similar to that of the primary tumour in 88% of patients.
Cell Division↗
p53 gene point mutations in relation to p53 nuclear protein accumulation in colorectal cancers.
It is known that structural alterations of the p53 tumour suppressor gene cause malignant transformation and tumour progression in colorectal mucosa. In this study, 38 colorectal cancers were analysed for mutations detected in the p53 gene by single-strand conformational polymorphism and DNA sequence analysis, and the results were compared with p53 protein expression detected by immunohistochemistry. A very strict association (P < 0.0001) was found between genetic alterations and protein accumulation, as detected by the PAb 1801 monoclonal antibody. p53 expression and gene mutations were more frequent in rectal than in colonic cancers. No relation was observed with Dukes' stage, even though most of the mutations were at exon 7 in Dukes' A-B cancers and almost all mutations at exon 8 were observed in Dukes' C-D cancers. DNA ploidy was not generally associated with p53 protein expression or gene mutations. However, 83 per cent of cases with exon 5 and 6 mutations were diploid or near-diploid and 71 per cent of cases with mutations at exons 7 and 8 were aneuploid. Tumours with p53 gene mutations at exon 5 had a higher median [3H]thymidine labelling index (17 per cent) than those with mutations at exons 6, 7, and 8 (11.8 per cent).
Base Sequence↗
The human insulin-like growth factor (IGF) binding protein-3 inhibits the growth of fibroblasts with a targeted disruption of the IGF-I receptor gene.
The insulin-like growth factors (IGFs) are important mitogens that exert their proliferative effects on cells via the type I IGF receptors (IGF-R). The IGFs also associate with IGF binding proteins (IGFBPs). IGF-inhibitory, IGF-stimulatory, and IGF-independent effects of IGFBPs on cell growth have been reported. We have asked whether the IGFBP-3 has an effect on cell growth, which is independent of its ability to bind IGF-I and thus inhibit the activation of the IGF-I receptor. For this purpose, we have used a fibroblast cell line (R- cells) derived from mouse embryos homozygous for a targeted disruption of the IGF-R gene. When compared with wild type cells (W), which bind IGF-I with high affinity and specificity, R- cells transfected with a mammalian expression vector containing the human (h) IG-FBP-3 cDNA were selected (R-/BP3) and found to express hIGFBP-3 mRNA (detected by Northern blots) and to secrete hIGFBP-3 protein [detected by Western ligand blotting (WLB), immunoblotting, and immunoprecipitation as well as immunofluorescence confocal microscopy]. Growth of five different R- cells, and 10-fold slower compared with W cells, grown under identical conditions. Confluent R- cells. These experiments show that the overexpression of IGFBP-3 has an inhibitory effect on cell growth which does not involve IGF binding to, or signal transduction via, the type I IGF-R. We conclude that the cellular production of IGFBPs serves as a negative regulator of cell proliferation which involves a cellular signaling pathway separate from the IGF-IGF-R system.
Animals↗
The role of the insulin-like growth factor I receptor in the transformation by simian virus 40 T antigen.
Balb/c 3T3 cells transformed by the tsA58 temperature-sensitive (ts) mutant of SV40 large T antigen, BalbA58 cells, grow in 1% serum at the permissive temperature of 34 degrees C but fail to grow at the restrictive temperature of 39.6 degrees C. Although incapable of growing, BalbA58 cells, in low serum at 39.6 degrees C, still synthesize DNA and tend to accumulate in the G2 phase of the cell cycle. Growth in 1% serum at 39.6 degrees C resumes if BalbA58 cells are treated with insulin-like growth factor I (IGF-I). By using cells overexpressing the IGF-I receptor, and cells with a targeted disruption of the IGF-I receptor genes, we show that: 1) the activation of the IGP-I receptor by its ligand(s) plays a major role in the ability of the SV40 large T antigen to promote growth in low serum; and 2) the IGF-I receptor plays a role in the progression of cells not only through G1, but also through the S and G2 phases of the cell cycle. These findings, together with other recent findings from the literature, suggest that one of the mechanisms by which oncogenes and tumor suppressor genes regulate cell growth is through the modulation of growth factors and their receptors.
3T3 Cells↗
Biological characterisation of primary and metachronous lesions in breast cancer patients.
Proliferative activity, evaluated as [3H]thymidine labelling index ([3H]dT LI), and hormone receptors were determined on 97 primary breast cancers and on metachronous lesions from the same patient. Overall, the [3H]dT LI of metachronous lesions was significantly higher than that of the primary tumour (P = 0.003). Hormone receptor profiles of the two lesions were similar in about 75% of the cases; disagreements were mainly due to a disappearance of hormone receptors in metachronous lesions. In contralateral tumours, [3H]dT LI and hormone receptors were unrelated to those of the relative primary lesion. In this series of relapsing patients, [3H]dT LI was unrelated to hormone receptor status in the primary tumour, but it was higher in the metachronous lesions from patients with hormone receptor-negative primary tumours. For patients given no systemic therapy between surgery and relapse, the time to develop local-regional recurrences or contralateral tumours was inversely related to the [3H]dT LI of the metachronous lesions.
Breast Neoplasms↗
Potentials of cell kinetics in the management of patients with ovarian cancers.
The relevance of 3H-thymidine labeling index (3H-dt LI) on clinical outcome was evaluated on 85 patients with advanced ovarian cancers treated with carboplatin or cisplatin alone (39 cases) or cisplatin in association with doxorubicin and/or cyclophosphamide (46 cases). 3H-dT LI of the primary tumour was significantly related to the 3-year probability of survival in patients treated by monochemotherapy (low LI, 63%; high LI, 21%; P = 0.013) but not in those treated with polychemotherapy. Analysis of the relation between cell kinetics and clinical outcome as a function of treatment showed that in patients with rapidly proliferating tumours the 3-year survival was significantly higher following polychemotherapy than monochemotherapy (51 vs. 21%; P = 0.04). In patients with slowly proliferating tumours no significant difference in survival was observed following the two types of treatment for the overall series, whereas in patients not achieving a complete response survival was significantly higher following monochemotherapy than polychemotherapy (61 vs. 9%; P = 0.008).
Antineoplastic Combined Chemotherapy Protocols↗
Changes in cell kinetics induced by primary chemotherapy in breast cancer.
Changes in the 3H-thymidine labelling index (3H-TdR LI) of primary tumor induced by cytoreductive chemotherapy were evaluated in 26 patients with locally advanced breast cancer subjected to mastectomy after different systemic therapies. A significant reduction of 3H-TdR LI by primary chemotherapy was observed in 11 cases. Changes in cell kinetics were related to the pretreatment proliferative activity: significant increases were observed in 70% of tumors with a very low 3H-TdR LI (less than 25%) and significant decreases in 100% of tumors with a very high 3H-TdR LI (greater than 7.0%). There was no correlation between pretreatment 3H-TdR LI and the objective clinical response, which was conversely related to posttreatment cell kinetics. The 2-year progression rate was lower for patients whose residual tumors after treatment had remained (2/7) or become (1/8) slowly proliferating than for patients whose tumors had remained (5/7) or become (4/4) rapidly proliferating.
Antineoplastic Combined Chemotherapy Protocols↗
3H-thymidine labeling index, hormone receptors, and ploidy in breast cancers from elderly patients.
Breast cancers from 476 elderly patients, 70 years and older, operated on since 1972, were analyzed for proliferative activity, hormone receptors, and DNA content. Tumor proliferative activity, expressed as 3H-thymidine labeling index (3H-TdR LI), had a median value of 3.4%, which progressively increased from 1972 to 1990. Estrogen and progesterone receptors were present respectively in 83% and 61% of the cases; the positivity for estrogen receptors slightly increased with time. Aneuploid clones were detected in 74% of the cases, and this incidence was relatively stable during the time of observation. 3H-TdR LI, hormone receptors, and ploidy were generally unrelated to the local-regional extension of the disease in these elderly patients, in agreement with observations on cancer from younger patients. However, the absence of hormone receptors and the presence of aneuploidy were markedly indicative of fast cell proliferation. As in younger patients, these biologic findings in elderly patients could be considered as a complement to clinico-pathologic features in a 'risk-factor profile system' for treatment planning.
Age Factors↗
Proliferative activity of primary breast cancer and of synchronous lymph node metastases evaluated by [3H]-thymidine labelling index.
The [3H]-thymidine labelling index ([3H]TdR LI) has been used to evaluate and comparatively analyse the proliferative activity of different tumour lesions from the same patient. The analysis was performed on the primary tumour and its synchronous lymph node metastasis from 210 patients operated on for breast cancer. A direct relation was observed between the proliferative activity of the two different lesions (Spearman correlation coefficient = 0.46, P less than 0.0001), but there was considerable scatter amongst the data. The [3H]TdR LI of primary and of metastatic lesions belonged to the same proliferation classes in only 47% of the cases. Higher or lower [3H]TdR LI values, categorized on the basis of the tertiles of the frequency distribution, occurred in the node metastasis than in the primary tumour in an almost similar percentage of the remaining cases. Menopause, receptor status and pathological features did not affect interlesion kinetic patterns. The prognostic role of the proliferative activity of the two different lesions was investigated on 107 patients with stage II tumours homogeneously treated with surgery and systemic adjuvant therapy. Relapse-free survival at 3 years was significantly affected by the proliferative activity of the primary tumour but not by that of the lymph node metastasis.
Breast Neoplasms↗
DNA ploidy of human breast cancer.
Ploidy was determined on 663 resectable primary tumors from untreated patients. Nuclei obtained by mechanical disaggregation of frozen tissue were stained with propidium iodide and analysed in a FACS IV. Aneuploidy was detected in 73% of cases. It was not significantly related to nodal involvement or tumor size, although the highest frequencies were observed in large tumors (88%) or with more than 10 positive nodes (77%). Aneuploidy was more frequently observed in ductal infiltrating (81%) than in lobular histology and in tumors lacking both progesterone and estrogen receptors (85%). Analysis of ploidy in primary and synchronous lymph node metastases from the same patient showed a high agreement rate (90%) of DNA patterns simply defined as diploid or aneuploid. However, differences in DNA stemlines and DNA indices between the two synchronous lesions from the same patient were a rather frequent event.
Adult↗
Insulin and IGF-I receptors signaling in protection from apoptosis.
R-cells are mouse embryo fibroblasts with a targeted disruption of the insulin-like growth factor I receptor (IGF-IR) genes. Because R-cells do not express the IGF-IR, they are ideal for studying the biological effects of the insulin receptor (IR), independently from any contribution by the IGF-IR. By stably transfecting R-cells with constructs expressing the IR, we show here the IR can protect cells from apoptosis induced by anoikis or by okadaic acid. The IR, however, is not as efficient as the IGF-IR in protecting mouse embryo fibroblasts from apoptosis, even when IRS-1, one of its major substrates, is over-expressed. In addition, the protection by the IGF-IR is resistant to inhibitors of phosphatidylinositol 3-kinase (PI 3-ki), while the anti-apoptotic effect of the IR is sensitive. These experiments suggest that the IGF-IR uses an alternative anti-apoptotic pathway, not shared with the IR, which is PI3-ki-independent.
3T3 Cells↗