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In the present study we demonstrated that TLQP-21, a biologically active peptide derived from the processing of the larger pro-VGF granin, plays a role in mammotrophic cell differentiation. We used an established in vitro model, the GH3 cell line, which upon treatment with epidermal growth factor develops a mammotrophic phenotype consisting of induction of prolactin expression and secretion, and inhibition of growth hormone. Here we determined for the first time that during mammotrophic differentiation, epidermal growth factor also induces Vgf gene expression and increases VGF protein precursor processing and peptide secretion. After this initial observation we set out to determine the specific role of the VGF encoded TLQP-21 peptide on this model. TLQP-21 induced a trophic effect on GH3 cells and increased prolactin expression and its own gene transcription without affecting growth hormone expression. TLQP-21 was also able to induce a significant rise of cytoplasmic calcium, as measured by Fura2AM, due to the release from a thapsigargin-sensitive store. TLQP-21-dependent rise in cytoplasmic calcium was, at least in part, dependent on the activation of phospholipase followed by phosphorylation of PKC and ERK. Taken together, the present results demonstrate that TLQP-21 contributes to differentiation of the GH3 cell line toward a mammotrophic phenotype and suggest that it may exert a neuroendocrine role in vivo on lactotroph cells in the pituitary gland. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Telomerase is a specialized DNA polymerase that is required to replicate the ends of linear chromosomes, the telomeres. The majority of human cancers express high levels of telomerase activity that is permissive for tumor growth because it provides cells with an extended proliferative potential. Additionally, telomerase exerts cell growth promoting functions and favors cell survival. Human glioblastoma multiforme (GBM) cells express high level of telomerase activity owing to the overexpression of human telomerase reverse transcriptase (hTERT), the limiting subunit of the enzyme. Here we used retroviral mediated RNA interference to dampen down telomerase activity in two distinct human GBM cell lines, U87MG and TB10. Substantial decrease of hTERT mRNA and telomerase activity had only minimal effects on telomere length maintenance, cell growth and survival in vitro. On the contrary, development of tumors upon subcutaneously grafting of U87MG and TB10 cells and intracranial implantation of U87MG cells in nude athymic mice was strongly reduced by telomerase inhibition. [ABSTRACT FROM AUTHOR]

Many studies have elucidated the important role played by the tumor microenvironment in cancer evolution. In particular the formation of hypoxic areas within the expanding mass of a solid tumor and the consequent induction of an angiogenic switch are crucial steps that shape tumor progression. Focusing on glioblastoma multiforme (GBM), the most common and lethal brain cancer in the adult, I will review recent data that show how the microenvironment regulates crucial functions of glioblastoma stem cells (GSCs) which in turn affect the angiogenic process.

Glioblastoma multiforme (GBM) is characterized by extensive angiogenesis that is mostly orchestrated by the hypoxia inducible factor HIF-1. Deregulation of HIF-1 is believed to contribute to cancer initiation and progression. However, instances have been described in which loss of HIF-1 leads to more aggressive tumors. Here we investigated the consequences of downregulating HIF-1 function in the human GBM cell line TB10, both on cell proliferation in vitro and on tumor growth in vivo. RNA interference targeting the O2-regulated HIF-1alpha subunit efficiently reduced HIF-1alpha expression and transcriptional induction of HIF-1-responsive genes without affecting cell growth. Thus, singularly grown wild-type and HIF-1alpha-inhibited GBM cell populations did not significantly differ in proliferation rate. However, when the two populations were co-cultured, wild-type cells overgrew the HIF-1alpha-inhibited cells. Subcutaneous grafting in nude mice of wild-type and HIF-1alpha-inhibited GBM cells lead to comparable tumor formation and growth. Interestingly, cografting of wt and HIF-1alpha- inhibited GBM cells in nude mice resulted in more aggressive tumors, both in terms of tumor appearance and tumor growth. This suggests that cellular populations that differ in their ability to mount a response to hypoxia may compete in vitro but cooperate in vivo resulting in increased tumor aggressiveness.

Most cells activate intracellular signalling to recover from heat damage. An increase of temperature, known as HS (heat shock), induces two major signalling events: the transcriptional induction of HSPs (heat-shock proteins) and the activation of the MAPK (mitogen-activated protein kinase) cascade. We performed the present study to examine the effects of HS, induced by different experimental conditions, on various kinases [ERK (extracellular-signal-regulated kinase), JNK (c-Jun N-terminal kinase), p38, Akt, AMPK (AMP-activated protein kinase) and PKC (protein kinase C)]. We investigated by Western blot analysis the phosphorylation of MAPK as a measure of cellular responsiveness to heat shift (37°C) and mild HS (40°C) in different cell lines. The results of the study indicate that every cell line responded to heat shift, and to a greater extent to HS, increasing ERK and JNK phosphorylation, whereas variable effects on activation or inhibition of PKC, AMPK, Akt and p38 were observed. Besides the implications of intracellular signalling activated by heat variations, these data may be of technical relevance, indicating possible sources of error due to different experimental temperature conditions.