The IGF system in thyroid cancer: new concepts

In recent years, the activation of the insulin-like growth factor (IGF) system in cancer has emerged as a key factor for tumour progression and resistance to apoptosis. Therefore, a variety of strategies have been developed to block the type I IGF receptor (IGF-I-R), which is thought to mediate the biological effects of both IGF-I and IGF-II. However, recent data suggest that the IGF signalling system is complex and that other receptors are involved. To unravel the complexity of the IGF system in thyroid cancer, IGF-I and IGF-II production, and the expression and function of their cognate receptors were studied. Both IGFs were found to be locally produced in thyroid cancer: IGF-I by stromal cells and IGF-II by malignant thyrocytes. Values were significantly higher in malignant tissue than in normal tissue. IGF-I-Rs were overexpressed in differentiated papillary carcinomas but not in poorly differentiated or undifferentiated tumours, whereas insulin receptors (IRs) were greatly overexpressed in all tumour hystotypes, with a trend for higher values in dedifferentiated tumours. As a consequence of IR overexpression, high amounts of IR/IGF-I-R hybrids (which bind IGF-I with high affinity) were present in all thyroid cancer histotypes. Because of recent evidence that isoform A of IR (IR-A) is a physiological receptor for IGF-II in fetal life, the relative abundance of IR-A in thyroid cancer was measured. Preliminary data indicate that overexpressed IRs mainly occur as IR-A in thyroid cancer. These data indicate that both IR/IGF-I-R hybrids and IR-A play an important role in the overactivation of the IGF system in thyroid cancer and in IGF-I mitogenic signalling in these tumours. J Clin PATHOL: Mol Pathol

Low expression of Met-hepatocytic growth factor receptor as an indicator of poor prognosis in thyroid tumors

Clinical implication of Met-hepatocytic growth factor receptor (Met/HGF-R) in thyroid adenocarcinoma tissue was studied on 163 operative thyroid samples (129papillary cancers, 21 follicular cancers, and 13 anaplastic cancers). 49 adenomas, 50 nodular goiters and 50 normal thyroids were compared. Expression of Met/HGF-R was estimated using semiquantitative immunohistochemical method including proportion (limits 0-5) and intensity (limits 0-5) of cell staining and calculation of Met/HGF-R total expression (limit 0-10). Met/HGF-R was not found in normal thyroid tissue, was absent or focally expressed in follicular and aplastic tumors, and was present in different amounts in papillary adenocarcinomas. It is suggested that low expression of Met/HGF-R is an indicator of unfavorable prognosis in papillary thyroid cancer.

Fine-needle aspiration biopsy of the thyroid

The routine use of thyroid FNAB caused profound changes in the management of thyroid nodules. FNAB allows a prompt identification and treatment of thyroid malignancies and avoids unnecessary surgery in patients with benign lesions, improving quality of life in patients with thyroid nodules. Furthermore, FNAB provides guidance for the type of surgery and reduces costs of care. On average, standard FNAB is nondiagnostic in 25% to 40% of cases, which include inadequate specimens and indeterminate (suspicious) diagnoses. In addition, a small percentage of false-negative diagnoses occur, which are unavoidable and raise concern of a late diagnosis of cancer. To minimize the limitations of FNAB, every center should reach and maintain a high standard of expertise in all of the steps of smear preparation and interpretation. Alternative modes of sampling or sample preparation may result in a reduction of nondiagnostic samples and better accuracy. Every center should set up clinical guidelines tailored to their own FNAB results and including the evaluation of clinical data. More work is needed to increase the accuracy of FNAB in suspicious cases. Toward this goal a variety of molecular markers have been evaluated; although none of them are ideal, some are promising. More studies need to be carried out in larger series to further evaluate the accuracy of these markers in identifying specific cancer histotypes within the group of suspicious lesions. It is hoped that, in the near future, the routine use of a combination of these markers will cost-effectively improve the diagnosis of malignant nodules classified as suspicious on traditional cytology. Statistical methods such as bayesian analysis or neural networks can be advantageously used to integrate different relevant information derived from family and personal history, clinical data, cytologic results, and evaluation of molecular markers.

[Differentiated carcinoma of the thyroid in the young. Clinical and histopathologic aspects]

BACKGROUND

The surgical approach to Differentiated Thyroid Carcinoma (DTC) is controversial. Aim of this study is to evaluate the opportunity of total thyroidectomy as treatment of choice for DTC in children.

METHODS

We examined the tumor features at diagnosis, the complications of surgery and the clinical outcome in a consecutive series of 33 young patients, (age range 7-19 yrs), who underwent total thyroidectomy for DTC as compared to a consecutive series of 181 adult patients operated for DTC (age range 20-64 yrs).

RESULTS

Histopathological examination has shown that bilateral foci of the tumor and extrathyroidal extension, were present with similar frequency in both groups of patients (15 vs 18% and 39 vs 48% respectively); node metastases and distant metastases were more frequent in young patients than in adult patients. Complications of total thyroidectomy were not frequent with 6% of permanent hypoparathyroidism. No case of laryngeal nerve damage was observed. In 7/8 patients with lung metastases the radioiodine treatment was effective: in four patients we observed a complete remission of disease, and in three patients a partial response with a decrease of Tg levels and a reduction of the radioiodine uptake areas.

CONCLUSIONS

Thyroid carcinoma is not less aggressive in children than in adults. Total thyroidectomy plus lymph node dissections appears to be the treatment of choice as routine surgical treatment of DTC in children. Radioiodine therapy gives good results for the treatment of lung metastases.

Appearance of antithyroglobulin antibodies as the sole sign of metastatic lymph nodes in a patient operated on for papillary thyroid cancer: a case report

We report a case in which the appearance of a progressively rising titer of thyroglobulin (Tg) antibodies was the most sensitive marker of papillary thyroid cancer relapse at loco-regional lymph nodes. The patient, a 60-year-old man, had been treated with total thyroidectomy plus lymphadenectomy and radioiodine ablation for a 1-cm papillary thyroid cancer. Twelve years after surgery, while undergoing levothyroxine (LT4) therapy, Tg antibodies were first detected and progressively rose from 99 to 1,697 U/mL in 18 months, while serum Tg remained undetectable. Both neck ultrasonography and 131I whole-body scan (WBS) were unremarkable. Enlarged lymph nodes became palpable at the left laterocervical region only 2 years after the first appearance of Tg antibodies and were surgically removed after cancer relapse was confirmed by fine-needle aspiration cytology. This case emphasizes the possibility that in thyroid cancer patients who have undergone total thyroidectomy, the appearance of Tg antibodies may indicate metastatic lymph nodes even when serum Tg is undetectable and WBS negative.

Insulin and insulin-like growth factor-I (IGF-I) receptor overexpression in breast cancers leads to insulin/IGF-I hybrid receptor overexpression: evidence for a second mechanism of IGF-I signaling

The insulin receptor (IR) form hybrids with the closely related insulin-like growth factor-I (IGF-I) receptor (IGF-I-R). Because most human breast carcinomas overexpress both the IR and the IGF-I-R, we evaluated whether the insulin/IGF-I hybrid receptor (Hybrid-R) is also overexpressed in these tumors and what role it plays in breast cancer biology. Using specific ELISAs and Western blots, we measured Hybrid-R content and function in 8 human cultured breast cancer cell lines and 39 human breast cancer specimens. Hybrid-R content and function were also compared to the content and function of the IR and the IGF-I-R. Hybrid-R content exceeded the IGF-I-R content in >75% of breast cancer specimens and was directly related to the molar ratio of both the IR and IGF-I-R content, suggesting that Hybrid-R formation occurred by random assembly of IR and IGF-I-R half-receptors. Hybrid-Rs became tyrosine autophosphorylated when breast cancer cells were exposed to IGF-I but not when they were exposed to insulin. In cells with an elevated Hybrid-R content, Hybrid-R autophosphorylation in response to IGF-I exceeded IGF-I-R autophosphorylation, suggesting that most of the IGF-I effect occurred via the Hybrid-R. Furthermore, Hybrid-Rs mediated growth in response to IGF-I, as indicated by experiments with blocking antibodies to the IGF-I-R. These data indicated therefore that: (a) Hybrid-Rs are present and play a major role in mediating the IGF-I signal in breast cancer; (b) their expression is directly related to IR overexpression; and (c) potential therapies designed to block IGF-I actions in breast cancer must take into account the role of these Hybrid-Rs.

Insulin receptor isoform A, a newly recognized, high-affinity insulin-like growth factor II receptor in fetal and cancer cells

Insulin-like growth factor II (IGF-II) is a peptide growth factor that is homologous to both insulin-like growth factor I (IGF-I) and insulin and plays an important role in embryonic development and carcinogenesis. IGF-II is believed to mediate its cellular signaling via the transmembrane tyrosine kinase type 1 insulin-like growth factor receptor (IGF-I-R), which is also the receptor for IGF-I. Earlier studies with both cultured cells and transgenic mice, however, have suggested that in the embryo the insulin receptor (IR) may also be a receptor for IGF-II. In most cells and tissues, IR binds IGF-II with relatively low affinity. The IR is expressed in two isoforms (IR-A and IR-B) differing by 12 amino acids due to the alternative splicing of exon 11. In the present study we found that IR-A but not IR-B bound IGF-II with an affinity close to that of insulin. Moreover, IGF-II bound to IR-A with an affinity equal to that of IGF-II binding to the IGF-I-R. Activation of IR-A by insulin led primarily to metabolic effects, whereas activation of IR-A by IGF-II led primarily to mitogenic effects. These differences in the biological effects of IR-A when activated by either IGF-II or insulin were associated with differential recruitment and activation of intracellular substrates. IR-A was preferentially expressed in fetal cells such as fetal fibroblasts, muscle, liver and kidney and had a relatively increased proportion of isoform A. IR-A expression was also increased in several tumors including those of the breast and colon. These data indicate, therefore, that there are two receptors for IGF-II, both IGF-I-R and IR-A. Further, they suggest that interaction of IGF-II with IR-A may play a role both in fetal growth and cancer biology.

Insulin receptor activation by IGF-II in breast cancers: evidence for a new autocrine/paracrine mechanism

IGF-II, produced by breast cancer epithelial and stromal cells, enhances tumor growth by activating the IGF-I receptor (IGF-I-R) via autocrine and paracrine mechanisms. Previously we found that the insulin receptor (IR), which is related to the IGF-I-R, is overexpressed in breast cancer cells. Herein, we find that, in breast cancer the IR is activated by IGF-II. In eight human breast cancer cell lines studied there was high affinity IGF-II binding to the IR, with subsequent IR activation. In these lines, IGF-II had a potency up to 63% that of insulin. In contrast, in non malignant human breast cells, IGF-II was less than 1% potent as insulin. Via activation of the IR tyrosine kinase IGF-II stimulated breast cancer cell growth. Moreover, IGF-II also activated the IR in breast cancer tissue specimens; IGF-II was 10-100% as potent as insulin. The IR occurs in two isoforms generated by alternative splicing of exon 11; these isoforms are IR-A (Ex11-) and IR-B (Ex11+). IR-A was predominantly expressed in breast cancer cells and specimens and the potency of IGF-II was correlated to the expression of this isoform (P<0.0001). These data indicate, therefore, that the IR-A, which binds IGF-II with high affinity, is predominantly expressed in breast cancer cells and represents a new autocrine/paracrine loop involved in tumor biology.

Insulin/IGF-I hybrid receptors play a major role in IGF-I signaling in thyroid cancer

The insulin-like growth factor-I (IGF-I) plays an important role in determining the biological behavior of a variety of malignancies. We measured IGF-I, its receptor and related receptors in thyroid cancer. IGF-I was present both in normal thyroid tissue and in thyroid cancer tissue and it was produced by stromal cells but not by thyrocytes. Values were significantly higher in malignant than in normal tissue. IGF-I receptors (IGF-I-Rs) and the homologous insulin receptors (IRs) were found overexpressed in both thyroid cancer cell lines (n = 4) and specimens (n = 17) as compared to normal values. In addition, high levels of hybrid IGF-I/insulin receptors (IR/IGF-I-Rs) were present in both thyroid cancer specimens and cell lines. IR/IGF-I-R hybrids were the most represented type of receptor in 14/17 specimens and exceeded the IGF-I-R content in all cases. Hybrid content correlated with the IR and IGF-I-R content, suggesting that in thyroid tissue hybrid formation occurs by random assembly of IR and IGF-I-R half receptors. Hybrid receptor autophosphorylation was stimulated by IGF-I with high affinity. In cells with a high IR/IGF-I-Rs content, blocking antibodies specific to these receptors substantially inhibited IGF-I induced cell growth. These data indicate that the IGF-I system is overactivated in thyroid cancer and that IR/IGF-I-R hybrid receptors play an important role in IGF-I mitogenic signaling in these tumors.

Expression of neurotrophins, GDNF, and their receptors in rat thyroid tissue

Levels of mRNA for neurotrophins (brain-derived neurotrophic factor, BDNF; neurotrophin 3, NT-3; neurotrophin 4, NT-4) and their receptors (trkA, trkB, trkC) and for glial cell line-derived neurotrophic factor (GDNF) and its receptors (ret, GDNFR-alpha) were measured in rat thyroid tissue by ribonuclease protection assays. In thyroid tissue the NT-3 mRNA level was threefold lower and the NT-4 mRNA level sixfold higher than those detected in adult rat hippocampus, while BDNF mRNA was undetectable. Very low levels of mRNA for truncated trkB and trkC receptors and no catalytic trkA, trkB or trkC were found. In conclusion NT-3 and NT-4, but not the corresponding functional receptors, are expressed in the thyroid tissue. Therefore, it is unlikely that these factors serve a direct local autocrine or paracrine function in thyroid cell types, and a target-derived mode of action on neurons innervating the thyroid tissue is suggested. An opposite result has been found for the neurotrophic factor GDNF: thyroid tissue showed a high level of transcripts for the GDNF receptor subunits (GDNFR-alpha and Ret), while GDNF mRNA was undetectable. The in situ hybridization analysis of GDNFR-alpha and ret mRNA revealed an interesting difference in the cell distribution of these transcripts: ret mRNA is selectively expressed in a subpopulation of cells scattered in the follicular epithelium and in the interfollicular spaces, while GDNFR-alpha expression is more homogeneous and widespread, including the more abundant cell type of the thyroid gland: the follicular cell. Double-labeling in situ hybridization/immunocytochemistry experiments, with a specific marker (calcitonin), showed that parafollicular cells express ret but not GDNFR-alpha. This differential distribution of the GDNF receptor components (GDNFR-alpha and ret) may reflect a peculiar biological role in intercellular communication in the thyroid gland.

Outcome of differentiated thyroid cancer in Graves' patients

The clinical behavior and outcome was evaluated in 21 nonoccult differentiated thyroid carcinomas occurring in Graves' patients during the period 1982-94 and compared with that of matched tumors occurring in euthyroid controls (n = 70). At surgery, patients with Graves' disease showed distant metastases more frequently than euthyroid patients (3/21 = 14.3% vs. 1/70 = 1.4%, P = 0.0556). Graves' patients also showed a significantly higher cumulative risk of recurrent/progressive distant metastases or total adverse events (odd ratios = 3.14 and 2.07, respectively) as compared with euthyroid patients. At the last follow-up visit, persistence of distant metastases was also more frequent in the Graves' group (P = 0.007), although the cumulative individual dose of radioiodine administered was higher than in the control group (median dose = 805 mCi vs. 350 mCi). Two patients died in the Graves' group vs. none in the control group. Circulating thyroid stimulating antibodies were present in all patients but one and persisted as long as signs of disease were evident. These findings indicate that differentiated thyroid carcinomas in patients with Graves' disease are more aggressive than those occurring in matched euthyroid controls and should, therefore, be managed accordingly.

Overexpression of the RON gene in human breast carcinoma

Constitutive activation of the RON gene, known to code for the tyrosine-kinase receptor for Macrophage Stimulating Protein (also known as Scatter Factor 2), has been shown to induce invasive-metastatic phenotype in vitro. As yet, nothing is known about the expression of this novel member of the MET-oncogene family in spontaneously occurring human cancers. Here we report that Ron is expressed at abnormally high levels in about 50% primary breast carcinomas (35/74 patients). Among these, the expression is increased more than 20-fold in 12 cases and the overexpressed protein is constitutively phosphorylated on tyrosine residues. Notably, Ron is only barely detectable in epithelial cells of the mammary gland, and its expression remains unchanged in benign breast lesions (including adenomas and papillomas). Overexpression was observed in different histotypic variants of carcinomas; it is associated with the disease at any stage and correlates with the post-menopausal status. In breast carcinoma cells grown in vitro, activation of the Ron receptor resulted in proliferation, migration and invasion through reconstituted basement membranes. Altogether, these data suggest a role for the RON gene in progression of human breast carcinomas to the invasive-metastatic phenotype.

Transition from cold to hot thyroid nodules

We report three cases of autonomously functioning thyroid nodules (AFTNs) that appeared hypofunctioning at radioactive iodine (131I) thyroid scan carried out at initial observation. Since at that time thyroid hormones and thyrotropin (TSH) were also normal, they were initially classified as "cold" nodules and treated with levothyroxine (LT4). The correct diagnosis of AFTN was made years later when a thyroid scintigraphy was repeated. In two of these patients, re-evaluation of the nodule was done because of the development of LT4 intolerance. A possible explanation is that these AFTNs had undergone hemorrhagic/cystic degeneration when they were first studied, but in subsequent years, proliferation of residual AFTN tissue caused the recurrence of a typical functioning nodule.

Insulin receptor what role in breast cancer?

It is commonly believed that the insulin receptor mainly mediates the metabolic effects of insulin, whereas the closely related IGF-I receptor is considered a major factor for the regulation of cell proliferation. Experimental and epidemiological evidence indicates, however, that insulin and insulin receptors may play an important role in breast cancer. This article reviews evidence indicating that (a) insulin receptors are overexpressed in human breast cancer, (b) insulin stimulates growth in breast cancer cells, (c) cells transfected with human insulin receptor may acquire a ligand-dependent transformed phenotype, and (d) breast cancer is associated with insulin resistance and hyperinsulinemia. These findings may open new possibilities in breast cancer prevention, prognosis assessment, and therapy. (Trends Endocrinol Metab 1997; 8:306-312). (c) 1997, Elsevier Science Inc.

Negative/low expression of the Met/hepatocyte growth factor receptor identifies papillary thyroid carcinomas with high risk of distant metastases

To investigate the clinical impact of Met/hepatocyte growth factor receptor (HGF-R) expression in thyroid cancer we studied 163 thyroid carcinomas (129 papillary, 21 follicular, and 13 anaplastic) from patients followed-up for 25-147 months postthyroidectomy. Forty-nine thyroid adenomas were also studied. Met/HGF-R expression was evaluated by semiquantitative immunohistochemistry, measuring both the proportion (scale of 0-5) and the intensity (scale, 0-5) of stained cells and calculating a total score (scale of 0-10). Met/HGF-R was absent in the normal thyroid tissue, absent or focally expressed in follicular and anaplastic tumors, and expressed at various levels in most papillary carcinomas, including microcarcinomas. Papillary carcinomas were thus categorized as having negative/low Met/HGF-R (n = 50; total score, < or = 5) or high Met/HGF-R expression (n = 70; total score, > 5). High Met/HGF-R was inversely associated with vascular invasion (P = 0.0308), but not with other prognostic factors. Negative/low Met/HGF-R expression was the most effective predictor by multivariate Cox analysis of distant metastases (hazard ratio = 9.71; P = 0.0036), higher than extrathyroid invasion (hazard ratio = 4.25; P = 0.0181), age (< or = 45 vs. > 45 yr; hazard ratio = 3.99; P = 0.0099), and vascular invasion (hazard ratio = 3.19; P = 0.0358). These findings suggest a role for Met/HGF-R in papillary thyroid cancer and its clinical use to select patients with a high risk of distant metastases.

In situ evidence of neoplastic cell phagocytosis by macrophages in papillary thyroid cancer

We evaluated the occurrence, tissue distribution, and prognostic value of tumor-associated macrophages in 121 papillary thyroid carcinomas using immunohistochemical staining with anti-CD68 antibody in archival paraffin-embedded sections. Lymphocytic infiltration and dendritic cell presence were also evaluated. Three groups were identified according to the presence and characteristics of macrophages: 1) tumors without evidence of infiltrating macrophages: (n = 35); 2) tumors with infiltrating macrophages but no evidence of neoplastic cells phagocytosis (n = 68); and 3) tumors with infiltrating macrophages and in situ evidence of active neoplastic cell phagocytosis (n = 18). Neoplastic cell phagocytosis by macrophages was positively correlated with both lymphocytic infiltration and dendritic cells (P = 0.0000), whereas it was negatively correlated with vascular invasion (P = 0.0032). Distant metastases developed in none of the 18 tumors with neoplastic cell phagocytosis, but occurred in 15 of 103 of the remaining tumors (P = 0.0647) and were significantly and negatively associated with lymphocytic infiltration or dendritic cells. The present study indicates, therefore, that immune reaction, involving neoplastic cell phagocytosis by macrophages and lymphocytic infiltration, plays a role in the development of distant metastases in patients with papillary thyroid cancer.

Detection of an activating mutation of the thyrotropin receptor in a case of an autonomously hyperfunctioning thyroid insular carcinoma

Thyroid carcinomas, even when well differentiated, usually appear as hypofunctioning at scintigraphy. We report a case of an aggressive insular thyroid carcinoma presenting as an autonomously functioning thyroid nodule and causing severe thyrotoxicosis. The tumor was metastatic to a cervical lymph node and both lungs. An activating mutation of the TSH receptor gene in both the primary tumor and the lymph node metastasis was found, due to a base substitution at codon 633 (normal guanine at position 1896 replaced by cytosine CAC for GAC causing aspartic acid substitution by histidine). Other known oncogenes (gsp, ras, PTC/ret, trk, met, and p53) were not involved. This is the first description of an activating TSH receptor mutation in a thyroid hyperfunctioning carcinoma in which an aggressive malignant phenotype coexisted with activation of the cAMP cascade and differentiated thyroid functions.

Laparoscopic adjustable silicone gastric banding: preliminary results of the University of Naples experience

BACKGROUND

Laparoscopic adjustable silicone gastric banding (LASGB) is a minimally invasive surgical procedure indicated for the treatment of patients with morbid obesity.

METHODS

From January 1996, eight patients successfully underwent the video-laparoscopic procedure.

RESULTS

Preoperative body mass index was 44.4 +/- 4.7 (range 37.9-53.3). Mean operative time was 255 +/- 73 minutes (range 150-360). Mean hospital stay was 3 +/- 1 days. Intraoperative complications were absent.

CONCLUSION

Preliminary results have been satisfactory, and encourage us to continue with LASGB.

Cold thyroid nodule reduction with L-thyroxine can be predicted by initial nodule volume and cytological characteristics

In a previous study we demonstrated that a 1-yr treatment with L-T4 induces substantial nodule volume reduction (> or = 50%) in approximately 40% of patients with a benign solitary cold thyroid nodule. The present prospective study investigated whether it is possible to identify, before starting L-T4 treatment, nodules with a high probability to shrink in response to L-T4. We recorded several clinical and cytological features in a continuous series of 42 patients with a cold nodule and related them to the nodule volume response to 1-yr treatment with L-T4. Fisher discriminant analysis showed that a combination of some cytological features (colloid, degenerative changes, cellular hyperplasia, and fibrosis) and initial nodule volume can be used for predicting nodule volume reduction. In fact, although only 33% of all nodules shrank, 62% of colloid nodules and 57% of small degenerative nodules shrank. None of the hyperplastic or fibrotic nodules shrank. These results were validated in a different retrospective series of 46 patients and allowed us to predict nodule reduction in over 80% of the cases.

Overexpression of membrane glycoprotein PC-1 in MDA-MB231 breast cancer cells is associated with inhibition of insulin receptor tyrosine kinase activity

MDA-MB231 human breast cancer cells are unresponsive to insulin and contain a glycoprotein inhibitor of insulin-stimulated insulin receptor (IR) tyrosine kinase activity. Prior studies in both fibroblasts from insulin- resistant non-insulin-dependent diabetes mellitus patients and transfected cells indicate that overexpression of membrane glycoprotein PC-1 reduces IR tyrosine kinase activity. In the present study, we measured PC-1 content and activity in MDA-MB231 and four other human breast cancer cell lines. We observed that PC-1 expression was 3- to 30-fold higher in MDA-MB231 cells when compared with the other breast cell lines. Wheat germ agglutinin extracts of MDA-MB231 cells inhibited IR tyrosine kinase activity. Treatment of these extracts with an antibody to PC-1 significantly reduced their ability to inhibit insulin-stimulated IR tyrosine kinase activity. In addition, when cell clones with different PC-1 activity were selected from MDA-MB231 cells, we found an inverse correlation (r = -0.741, P = 0.006) between the PC-1 activity and the insulin-stimulated IR autophosphorylation. A similar inverse correlation was observed in cell clones derived from the insulin-responsive breast cancer cell line MCF-7. By both immunoprecipitation and cross-linking studies we found PC-1 to be associated with IR. These studies indicate, therefore, that overexpression of PC-1 in MDA-MB231 cells may account, at least in part, for the reduced IR tyrosine kinase activity and suggest that PC-1 is a specific modulator of the IR activity in breast cancer cells.

Interleukin-1 blocks insulin and insulin-like growth factor-stimulated growth in MCF-7 human breast cancer cells by inhibiting receptor tyrosine kinase activity

Interleukins-1 (IL-1s) are known to inhibit the growth of cultured breast cancer cells. We examined the effects of IL-1 alpha and IL-1 beta on insulin and insulin-like growth factor I (IGF-I) stimulation of cell growth and found that both IL-1s inhibited anchorage-dependent and independent growth of MCF-7 breast cancer cells. In cells incubated with IL-1 beta (100 U/ml), insulin receptor (IR) protein and messenger RNA were increased by 100%, while IGF-I receptor protein and transcript were not significantly changed. These data were confirmed by binding studies. Incubation of MCF-7 cells with IL-1s led, however, to a significant inhibition of IR and IGF-I receptor autophosphorylation (-55%) and phosphotransferase activity (-65%). Also, in 3T3/ HIR rat fibroblasts, transfected with and overexpressing IR, IL-1s decreased insulin-stimulated cell growth in soft agar and IR tyrosine kinase activity. The present findings suggest that IL-1s antagonize the insulin and IGF-I mitogenic effects in MCF-7 cells by blocking the receptor tyrosine kinase activity that is crucial for the mitogenic effect of these factors.