Growth factor receptor inhibitor

About: Growth factor receptor inhibitor is a research topic. Over the lifetime, 4730 publications have been published within this topic receiving 297500 citations.

Insulin-like growth factor binding proteins: new proteins, new functions.

Abstract: The insulin-like growth factors (IGFs), IGF binding proteins (IGFBPs), and IGFBP proteases regulate somatic growth and cellular proliferation both in vivo and in vitro. IGFs are potent mitogens whose actions are determined by the availability of free IGFs to interact with IGF receptors. IGFBPs comprise a family of six proteins that bind IGFs with high affinity and specificity and thereby regulate IGF-dependent actions. IGFBPs have recently emerged as IGF-independent regulators of cell growth. Cleavage of IGFBPs by specific proteases modulate levels of free IGFs and IGFBPs and thereby their actions. IGFBP-related proteins (IGFBP-rPs) bind IGFs with low affinity and also play important roles in cell growth and differentiation. The GH-IGF-IGFBP axis is complex and powerful. Future research on its physiology promises exciting insights into cell biology as well as therapies for diseases such as cancer and diabetes mellitus.

Upregulation of vascular endothelial growth factor (VEGF) and downregulation of placenta growth factor (PlGF) associated with malignancy in human thyroid tumors and cell lines.

Abstract: Vascular endothelial growth factor (VEGF) is a potent mitogen for endothelial cells in vitro, promotes neoangiogenesis in vivo and increases the permeability of the vascular endothelium. VEGF overexpression occurs in several cultured tumor cell lines and in certain human malignancies. Placenta growth factor (PlGF) is a recently identified growth factor for endothelial cells (EC); PlGF strongly potentiates both the proliferative and the permeabilization effects exerted by VEGF on the vascular endothelium. To uncover the molecular mechanisms underlying neoangiogenesis in human thyroid tumors, we have analysed VEGF and PlGF expression in a panel of thyroid carcinoma cell lines with different tumorigenic potential as well as in human primary thyroid tumors. We show that a high tumorigenic potential is associated with an elevated VEGF expression in human thyroid tumor cell lines. Furthermore, VEGF overexpression occurs in 5/5 highly malignant anaplastic carcinomas. Papillary and follicular carcinomas express intermediate levels of VEGF mRNA. In contrast, PlGF expression is severely down regulated in the majority of thyroid tumor cell lines and in tumors. Furthermore, we show that both the VEGF receptors, FLT-1 and flk/KDR, are expressed in endothelial cells that line tumor-embedded microvascular vessels, suggesting that VEGF but not PlGF, contributes to thyroid tumor development.

Insulin as a Growth Factor

Abstract: Insulin is a potent mitogen for many cell types in vitro. During tissue culture, supraphysiological concentrations of insulin are necessary to promote cell replication in connective or musculoskeletal tissues. Insulin promotes the growth of these cells by binding, with low affinity, to the type I insulin-like growth factor (IGF) receptor, not through the high affinity insulin receptor. In other cell types, such as hepatocytes, embryonal carcinoma cells, or mammary tumor cells, the type I IGF receptor is virtually absent, and insulin stimulates the growth of these cells at physiological concentrations by binding to the high affinity insulin receptor. Both receptor systems activate phosphorylation reactions within the cell which extend to ribosomal proteins. Insulin acts synergistically with other factors, such as platelet-derived growth factor and epidermal growth factor, to stimulate the progression of cells through the cycle of proliferation. Abnormal insulin secretion or action, before or after birth, often is associated with disordered growth suggesting that insulin may function as a growth factor in vivo. Poor growth follows impaired insulin secretion in diabetes mellitus. This is associated with reduced circulating levels of IGF's which may be partly responsible for the growth failure. Insulin has a direct action on release of IGF's from the liver in vitro, but during experimental diabetes there is a reduced number of hepatic somatotropic receptors which could limit the ability of growth hormone to regulate IGF release. Diabetic children, treated conventionally, have normal circulating IGF levels, but both growth rate and serum IGF concentration may increase dramatically when diabetic control is optimized.(ABSTRACT TRUNCATED AT 250 WORDS)

Activation of growth factor secretion in tumorigenic states of breast cancer induced by 17 beta-estradiol or v-Ha-ras oncogene.

Abstract: The MCF-7 human breast cancer cell line responds to estrogen stimulation in vitro by increased secretion of growth factors and proliferation and in vivo by tumor formation in the nude mouse. To test a possible role of growth factor secretion in expression of the tumorigenic phenotype, we stably transfected MCF-7 cells with the v-Ha-ras oncogene to produce the MCF-7ras cell line. The MCF-7ras cell line was tumorigenic in the absence of estrogens and secreted 3- to 5-fold elevated levels of a high molecular weight form of a type alpha transforming growth factor-like growth factor, type beta transforming growth factor, and insulin-like growth factor I. MCF-7ras cells, in contrast to MCF-7, were less sensitive to further growth stimulation by estrogen, type alpha transforming growth factor, and insulin-like growth factor I and showed little change in receptor levels for these hormones. Conditioned medium from MCF-7ras cells as well as two of its component growth factors (insulin-like growth factor I and type alpha transforming growth factor) replaced estrogen in stimulating MCF-7 colony formation in vitro. A coordinate increase in growth factor secretion by human breast cancer may contribute to its escape from estrogen dependence.