Regulation of cell apoptosis by insulin-like growth factor I.
TL;DR: Results support the conclusion that inhibition of apoptosis within the mammary gland by IGF-I involves decreased activity of AP-1 and predisposes the tissue to tumors.
Abstract: Correct temporal and spatial regulation of apoptosis is critical for normal mammary gland development and lactation. Previous work with a strain of trans-genic mice that overexpress des(1-3)hIGF-I during pregnancy and lactation suggested that this growth factor inhibits apoptosis. The hypothesis tested within these studies is that overexpression of des(1-3)hIGF-I within the mammary gland inhibits apoptosis and the expression of apoptosis-associated genes that are known to be activated by the transcription factor AP-1. This inhibition of apoptosis was further posited to predispose the tissue to carcinogenesis. TUNEL analysis of mammary tissue from transgenic mice that overexpress des(1-3)hIGF-I under control of the rat whey acidic protein promoter showed only 25% (P < 0.05) of the number of apoptotic cells found in nontransgenic mice at the same stage of lactation. Northern analysis of RNA from these animals showed a 75% (P = 0.08) reduction in c-Jun mRNA abundance. Histological analysis of mammary tissue from nonlactating multiparous WAP-DES mice ranging in age from 13 to 25 months showed a variety of hyper-plastic lesions. These lesions aberrantly expressed the transgene. At 23 months of age 50% of the transgenic mice within this study developed adenocarcinomas. These results support the conclusion that inhibition of apoptosis within the mammary gland by IGF-I involves decreased activity of AP-1 and predisposes the tissue to tumors.
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TL;DR: It is shown that overexpression ofAIB1 in transgenic mice (AIB1-tg) leads to mammary hypertrophy, hyperplasia, abnormal postweaning involution, and the development of malignant mammary tumors, suggesting that an autocrine IGF-I loop underlies the mechanism of AIB1-induced oncogenesis.
368 citations
Cites result from "Regulation of cell apoptosis by ins..."
...%) counterstained with hematoxylin.of mammary tumors, albeit at a later onset (24 month) than in our study (Hadsell and Abdel-Fattah, 2001)....
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TL;DR: In some mammals, including humans, proliferative exhaustion is followed by epiphyseal fusion, an abrupt event in which the growth plate cartilage is replaced completely by bone.
Abstract: Longitudinal bone growth occurs rapidly in early life but then slows and, eventually, ceases. The decline in growth rate is caused primarily by a decrease in the rate of chondrocyte proliferation and is accompanied by structural changes in growth plate cartilage. This programmed senescence does not appear to be caused by hormonal or other systemic mechanisms but is intrinsic to the growth plate itself. In particular, recent evidence indicates that senescence might occur because stem-like cells in the resting zone have a finite proliferative capacity, which is exhausted gradually. In some mammals, including humans, proliferative exhaustion is followed by epiphyseal fusion, an abrupt event in which the growth plate cartilage is replaced completely by bone.
121 citations
TL;DR: Results clearly show that SRC-3 and AP-1 can coordinately regulate the transcription of multiple components in the IGF/AKT pathway to ensure ligand-independent cell proliferation and survival of cancer cells.
Abstract: Steroid receptor coactivator (SRC)-3, also called amplified in breast cancer 1, is a member of the p160 nuclear receptor coactivator family involved in transcriptional regulation of target genes. SRC-3 is frequently amplified and/or overexpressed in hormone-sensitive and hormone-insensitive tumors. We reported previously that SRC-3 stimulated prostate cell growth in a hormone-independent manner through activation of AKT signaling pathway. However, the underlying mechanism remains undefined. Here, we exploited the mifepristone-induced SRC-3 LNCaP prostate cancer cell line generated in our laboratory to identify SRC-3-regulated genes by oligonucleotide microarray analysis. We found that SRC-3 up-regulates the expression of multiple genes in the insulin-like growth factor (IGF)/AKT signaling pathway that are involved in cell proliferation and survival. In contrast, knockdown of SRC-3 in PC3 (androgen receptor negative) prostate cancer cells and MCF-7 breast cancer cells reduces their expression. Similarly, in prostate glands of SRC-3 null mice, expressions of these components in the IGF/AKT signal pathway are also reduced. Chromatin immunoprecipitation assay revealed that SRC-3 was directly recruited to the promoters of these genes, indicating that they are direct targets of SRC-3. Interestingly, we showed that recruitment of SRC-3 to two target promoters, IRS-2 and IGF-I, requires transcription factor activator protein-1 (AP-1). Taken together, our results clearly show that SRC-3 and AP-1 can coordinately regulate the transcription of multiple components in the IGF/AKT pathway to ensure ligand-independent cell proliferation and survival of cancer cells.
113 citations
TL;DR: This is the first study demonstrating that higher IGF-I levels, and lower and higher IGFBP-3 levels are risk factors for SPT development.
Abstract: Purpose: Second primary tumors (SPTs) are a hallmark of head and neck squamous cell carcinomas (HNSCCs). Serum levels of insulin growth factors (IGFs) and their binding proteins (IGFBPs) have been associated with subsequent development of several epithelial cancers in prospective studies. Experimental Design: To examine the role of IGFs in SPT development, we conducted a nested case–control study within a randomized, placebo-controlled chemoprevention trial in patients with early-stage HNSCC. We compared prediagnostic serum IGF-I and IGFBP-3 levels in 80 patients who subsequently developed SPTs and 173 controls (patients without SPTs) matched to the cases on age (±5 years), sex, ethnicity, year of randomization, and length of follow-up. Results: The cases exhibited significantly higher levels of IGF-I and IGFBP-3 than did the controls ( P = 0.001 and 0.019, respectively). Elevated IGF-I levels were associated with a 3.66-fold significantly increased risk of SPT. Lower and higher IGFBP-3 levels were associated with a 2.22- and 7.12-fold significant increased risk, respectively. The median SPT-free time was significantly shorter in patients with higher IGF-I levels than in patients with lower IGF-I levels ( P P = 0.002). Moreover, in the Cox proportional hazards model, higher IGF-I levels were significantly associated with increased risk of SPT with a hazard ratio of 2.78. Patients with the lower and higher IGFBP-3 levels also exhibited significantly increased risks with hazard ratios of 1.65 and 2.17, respectively. Conclusions: This is the first study demonstrating that higher IGF-I levels, and lower and higher IGFBP-3 levels are risk factors for SPT development. Thus, measuring serum IGF-I and IGFBP-3 levels may be useful markers in assessing the risk of second tumors in patients successfully treated for their index cancer.
68 citations
TL;DR: The number of infiltrating adaptive immune system cells with tumour-rejecting capacity, primarily, T lymphocytes, is lower in breast cancer compared with other cancer types, but infiltration occurs in a large proportion of cases.
Abstract: A cancer cell-centric view has long dominated the field of cancer biology. Research efforts have focussed on aberrant cancer cell signalling pathways and on changes to cancer cell DNA. Mounting evidence demonstrates that many cancer-associated cell types within the tumour stroma co-evolve and support tumour growth and development, greatly modifying cancer cell behaviour, facilitating invasion and metastasis and controlling dormancy and sensitivity to drug therapy. Thus, these stromal cells represent potential targets for cancer therapy. Among these cell types, immune cells have emerged as a promising target for therapy. The adaptive and the innate immune system play an important role in normal mammary development and breast cancer. The number of infiltrating adaptive immune system cells with tumour-rejecting capacity, primarily, T lymphocytes, is lower in breast cancer compared with other cancer types, but infiltration occurs in a large proportion of cases. There is strong evidence demonstrating the importance of the immunosuppressive role of the innate immune system during breast cancer progression. A consideration of components of both the innate and the adaptive immune system is essential for the design and development of immunotherapies in breast cancer. In this review, we focus on the importance of immunosuppressive myeloid-derived suppressor cells (MDSCs) as potential targets for breast cancer therapy.
62 citations
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...1995, Hadsell & Abdel-Fattah 2001, Tonner et al....
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References
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TL;DR: The effects of dominant-interfering or constitutively activated forms of various components of the JNK-p38 and ERK signaling pathways demonstrated that activation of JNK and p38 and concurrent inhibition of ERK are critical for induction of apoptosis in these cells.
Abstract: Apoptosis plays an important role during neuronal development, and defects in apoptosis may underlie various neurodegenerative disorders. To characterize molecular mechanisms that regulate neuronal apoptosis, the contributions to cell death of mitogen-activated protein (MAP) kinase family members, including ERK (extracellular signal-regulated kinase), JNK (c-JUN NH2-terminal protein kinase), and p38, were examined after withdrawal of nerve growth factor (NGF) from rat PC-12 pheochromocytoma cells. NGF withdrawal led to sustained activation of the JNK and p38 enzymes and inhibition of ERKs. The effects of dominant-interfering or constitutively activated forms of various components of the JNK-p38 and ERK signaling pathways demonstrated that activation of JNK and p38 and concurrent inhibition of ERK are critical for induction of apoptosis in these cells. Therefore, the dynamic balance between growth factor-activated ERK and stress-activated JNK-p38 pathways may be important in determining whether a cell survives or undergoes apoptosis.
5,398 citations
TL;DR: Postnatal growth curves indicated that surviving Igf-1(-/-) mutants, which are infertile and exhibit delayed bone development, continue to grow with a retarded rate after birth in comparison with wild-type littermates and become 30% of normal weight as adults.
2,411 citations
TL;DR: The proapoptotic function of BAD is regulated by the PI 3-kinase-Akt pathway, and active, but not inactive, forms of Akt were found to phosphorylate BAD in vivo and in vitro at the same residues that are phosphorylated in response to IL-3.
Abstract: BAD is a distant member of the Bcl-2 family that promotes cell death. Phosphorylation of BAD prevents this. BAD phosphorylation induced by interleukin-3 (IL-3) was inhibited by specific inhibitors of phosphoinositide 3-kinase (PI 3-kinase). Akt, a survival-promoting serine-threonine protein kinase, was activated by IL-3 in a PI 3-kinase-dependent manner. Active, but not inactive, forms of Akt were found to phosphorylate BAD in vivo and in vitro at the same residues that are phosphorylated in response to IL-3. Thus, the proapoptotic function of BAD is regulated by the PI 3-kinase-Akt pathway.
2,321 citations
TL;DR: A novel interacting protein, Bad, whose homology to Bcl-2 is limited to the BH1 and BH2 domains is identified, whose role in the mammalian cell death pathway is determined by these competing dimerizations in which levels of Bad influence the effectiveness of BCl-2 versus B cl-xL in repressing death.
2,159 citations
TL;DR: The entire 1,370-amino-acid sequence of the human insulin receptor precursor is deduced from a single complementary DNA clone, finding sequence homologies to human epidermal growth factor receptor and the members of the src family of oncogene products.
Abstract: We have deduced the entire 1,370-amino-acid sequence of the human insulin receptor precursor from a single complementary DNA clone. The precursor starts with a 27-amino-acid signal sequence, followed by the receptor α-subunit, a precursor processing enzyme cleavage site, then the β-subunit containing a single 23-amino-acid transmembrane sequence. There are sequence homologies to human epidermal growth factor receptor and the members of the src family of oncogene products.
2,140 citations