Our findings suggest that a myriad of molecular mechanisms are induced by GH that cause EMT and may point to potential therapeutic use of GH antagonists or any downregulator of GH action in EMT-related disease.

The reorganization of cranial cartilages during tadpole metamorphosis is a set of complex processes. The fates of larval cartilage-forming cells (chondrocytes) and sources of adult chondrocytes are largely unknown. Individual larval cranial cartilages may either degenerate or remodel, while many adult cartilages appear to form de novo during metamorphosis. Determining the extent to which adult chondrocytes/cartilages are derived from larval chondrocytes during metamorphosis requires new techniques in chondrocyte lineage tracing. We have developed two transgenic systems to label cartilage cells throughout the body with fluorescent proteins. One system strongly labels early tadpole cartilages only. The other system inducibly labels forming cartilages at any developmental stage. We examined cartilages of the skull (viscero- and neurocranium), and identified larval cartilages that either resorb or remodel into adult cartilages. Our data show that the adult otic capsules, tecti anterius and posterius, hyale, and portions of Meckel’s cartilage are derived from larval chondrocytes. Our data also suggest that most adult cartilages form de novo, though we cannot rule out the potential for extreme larval chondrocyte proliferation or de- and re-differentiation, which could dilute our fluorescent protein signal. The transgenic lineage tracing strategies developed here are the first examples of inducible, skeleton-specific, lineage tracing in Xenopus.

Growth hormone (GH) facilitates therapy resistance in the cancers of breast, colon, endometrium, and melanoma. The GH-stimulated pathways responsible for this resistance were identified as suppression of apoptosis, induction of epithelial-to-mesenchymal transition (EMT), and upregulated drug efflux by increased expression of ATP-binding cassette containing multidrug efflux pumps (ABC-transporters). In extremely drug-resistant melanoma, ABC-transporters have also been reported to mediate drug sequestration in intracellular melanosomes, thereby reducing drug efficacy. Melanocyte-inducing transcription factor (MITF) is the master regulator of melanocyte and melanoma cell fate as well as the melanosomal machinery. MITF targets such as the oncogene MET, as well as MITF-mediated processes such as resistance to radiation therapy, are both known to be upregulated by GH. Therefore, we chose to query the direct effects of GH on MITF expression and activity towards conferring chemoresistance in melanoma. Here, we demonstrate that GH significantly upregulates MITF as well as the MITF target genes following treatment with multiple anticancer drug treatments such as chemotherapy, BRAF-inhibitors, as well as tyrosine-kinase inhibitors. GH action also upregulated MITF-regulated processes such as melanogenesis and tyrosinase activity. Significant elevation in MITF and MITF target gene expression was also observed in mouse B16F10 melanoma cells and xenografts in bovine GH transgenic (bGH) mice compared to wild-type littermates. Through pathway inhibitor analysis we identified that both the JAK2-STAT5 and SRC activities were critical for the observed effects. Additionally, a retrospective analysis of gene expression data from GTEx, NCI60, CCLE, and TCGA databases corroborated our observed correlation of MITF function and GH action. Therefore, we present in vitro, in vivo, and in silico evidence which strongly implicates the GH–GHR axis in inducing chemoresistance in human melanoma by driving MITF-regulated and ABC-transporter-mediated drug clearance pathways.

Growth hormone (GH) and the GH receptor (GHR) are expressed in a wide range of malignant tumors including melanoma. However, the effect of GH/insulin-like growth factor (IGF) on melanoma in vivo has not yet been elucidated. Here we assessed the physical and molecular effects of GH on mouse melanoma B16-F10 and human melanoma SK-MEL-30 cells in vitro. We then corroborated these observations with syngeneic B16-F10 tumors in two mouse lines with different levels of GH/IGF: bovine GH transgenic mice (bGH; high GH, high IGF-1) and GHR gene-disrupted or knockout mice (GHRKO; high GH, low IGF-1). In vitro, GH treatment enhanced mouse and human melanoma cell growth, drug retention and cell invasion. While the in vivo tumor size was unaffected in both bGH and GHRKO mouse lines, multiple drug-efflux pumps were up regulated. This intrinsic capacity of therapy resistance appears to be GH dependent. Additionally, epithelial-to-mesenchymal transition (EMT) gene transcription markers were significantly upregulated in vivo supporting our current and recent in vitro observations. These syngeneic mouse melanoma models of differential GH/IGF action can be valuable tools in screening for therapeutic options where lowering GH/IGF-1 action is important.

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Growth hormone (GH) is a protein that is known to stimulate postnatal growth, counter regulate insulin’s action and induce expression of insulin-like growth factor-1. GH exerts anabolic or catabolic effects depending upon on the targeted tissue. For instance, GH increases skeletal muscle and decreases adipose tissue mass. Our laboratory has spent the past two decades studying these effects, including the effects of GH excess and depletion, on the proteome of several mouse and human tissues. This review first discusses proteomic techniques that are commonly used for these types of studies. We then examine the proteomic differences found in mice with excess circulating GH (bGH mice) or mice with disruption of the GH receptor gene (GHR−/−). We also describe the effects of increased and decreased GH action on the proteome of adult patients with either acromegaly, GH deficiency or patients after short-term GH treatment. Finally, we explain how these proteomic studies resulted in the discovery of potential biomarkers for GH action, particularly those related with the effects of GH on aging, glucose metabolism and body composition.Electronic supplementary materialThe online version of this article (doi:10.1186/s12014-017-9160-2) contains supplementary material, which is available to authorized users.

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The impact of growth hormone (GH) on systemic glucose, growth and the myriad of downstream targets indicate the potential to enhance the progression of cancers. There is, however, continued debate as to GH’s impact on cancer with varied effects across subjects and cancer types. To bridge this gap in fundamental understanding, 16 human cancer types were selected and the RNA expression data for all matching samples (primary or metastatic) were queried in The Cancer Genome Atlas (TCGA). Each cancer type was stratified into GH-responsive [GH receptor (R) expression in the top quartile of each cancer type] and baseline (the remaining 75% of samples). Patients with GH-responsive cutaneous melanomas had a significant reduction in post-diagnosis lifespan (log-rank test, P = 0.0073). To explore the deleterious effects of GH in melanoma progression, we developed a novel tool, gdc-file-matcher (https://github.com/pxslip/gdc-file-matcher), to extract dataset metadata. Using the extensive metadata available in TCGA, we identified a significant negative correlation (P r (>|t|) = 0.021) between GHR expression and post-diagnosis lifespan in male melanoma patients who died within 1 year of diagnosis that drove the reduction in lifespan. The same trend, though not significant, was also observed in female melanoma patients. To validate the stratification approach, differential expression profiles were generated using a generalized linear model in EdgeR. The expression profiles were validated against expression levels of adiponectin, multiple ABC transporters, and metastatic markers in implanted B16-F10 melanomas in wild-type C57BL6J mice and transgenic bGH mice. The expression profiles of the implanted in vivo melanoma samples validated the stratification approach as indicative of GH action in human melanomas. To understand the molecular mechanisms resulting in increased mortality rates of GH-responsive tumors, the differentially expressed genes were investigated. The gene expression profiles showed clear evidence for a greater metastatic potential in GH-responsive tumors. In addition, upregulated genes showed an increased potential for angiogenesis and drug resistance along with a downregulation of DNA repair genes, P53 signaling cascades and other protective pathways. Thus, we demonstrate induced melanomas in the C57BL6J background are a reliable mouse model for translational research in GH-related cancer and are likely able to be expanded as a model for additional melanoma therapy research. Most critically, the survival and gene expression data from this in vivo validated informatic analysis demonstrate a clear role for Pegvisomant or alternate forms of GH modulation in the treatment of GH-responsive melanomas.