Search

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.

Childhood diarrhea is one of the leading causes of morbidity and mortality in children under five in low and middle-income countries, second only to respiratory illness. The mouthing behavior that is common in children exposes them to fecal-orally transmitted pathogens that can result in diarrhea; however, there is a need for further evidence on specific exposure routes. This study describes the frequency and diversity of two important routes of enteric pathogen exposure among infants 3-9 months of age: infant oral contact behavior and caregiver handwashing behavior. Data were collected through structured observations of 25 index infants for the oral contact data and 25 households for the caregiver handwashing data in a peri-urban setting in Kisumu (Obunga), Kenya. Breast was the most common type of oral contact event with an average of 3.00 per observation period and 0.5 events per hour. This was followed by a range of physical objects with an average of 2.49 per observation and 0.4 events per hour. The "infant's own hands" was the third most common oral contact, with an average of 2.16 events per hour, and 0.4 oral contact events per hour. Food and liquids were the 4th and 5th most common oral contact events with an average of 1.64 food contacts and 0.52 liquid oral contact events per observation period. Feeding events, including breastfeeding, were the most commonly observed key juncture-71% of total junctures observed were caregivers feeding children. This was followed by child cleaning (23%), caregiver toilet uses at (4%), and lastly food preparation at 2%. HWWS was observed only once before a feeding event (1%), twice after cleaning a child (9%), and twice after caregiver toilet use (40%). The combined implication of data from observing oral contact behavior in children and hand hygiene of caregivers suggests that caregiver hand hygiene prior to feeding events and after cleaning a child are priority interventions.

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&ndash, GHR axis in inducing chemoresistance in human melanoma by driving MITF-regulated and ABC-transporter-mediated drug clearance pathways.