Alteration of ribosome function upon 5-fluorouracil treatment favors cancer cell drug-tolerance.

Mechanisms of drug-tolerance remain poorly understood and have been linked to genomic but also to non-genomic processes. 5-fluorouracil (5-FU), the most widely used chemotherapy in oncology is associated with resistance. While prescribed as an inhibitor of DNA replication, 5-FU alters all RNA pathways. Here, we show that 5-FU treatment leads to the production of fluorinated ribosomes exhibiting altered translational activities. 5-FU is incorporated into ribosomal RNAs of mature ribosomes in cancer cell lines, colorectal xenografts, and human tumors. Fluorinated ribosomes appear to be functional, yet, they display a selective translational activity towards mRNAs depending on the nature of their 5'-untranslated region. As a result, we find that sustained translation of IGF-1R mRNA, which encodes one of the most potent cell survival effectors, promotes the survival of 5-FU-treated colorectal cancer cells. Altogether, our results demonstrate that "man-made" fluorinated ribosomes favor the drug-tolerant cellular phenotype by promoting translation of survival genes

Prolactin receptor is a negative prognostic factor in patients with squamous cell carcinoma of the head and neck

Background: The influence of human prolactin (hPRL) on the development of breast and other types of cancer is well established. Little information, however, exists on the effects of hPRL on squamous cell carcinomas of the head and neck (SCCHNs). Methods: In this study, we evaluated prolactin receptor (PRLR) expression in SCCHN cell lines and assessed by immunohistochemistry the expression in 89 patients with SCCHNs. The PRLR expression was correlated with clinicopathological characteristics as well as clinical outcome. The effect of hPRL treatment on tumour cell growth was evaluated in vitro. Results: Immunoreactivity for PRLR was observed in 85 out of 89 (95%) tumours. Multivariate COX regression analysis confirmed high levels of PRLR expression (>25% of tumour cells) to be an independent prognostic factor with respect to overall survival (HR=3.70, 95% CI: 1.14–12.01; P=0.029) and disease-free survival (P=0.017). Growth of PRLR-positive cancer cells increased in response to hPRL treatment. Conclusion: Our data indicate that hPRL is an important growth factor for SCCHN. Because of PRLR expression in a vast majority of tumour specimens and its negative impact on overall survival, the receptor represents a novel prognosticator and a promising drug target for patients with SCCHNs

Growth-Hormone Receptor-Binding Protein in Rat Anterior-Pituitary

GH is synthesized by the somatotrophs in the pituitary, where it may have paracrine actions. In order to identify the GH target cells in rat pituitary, the cellular distributions of rat GH receptor binding protein messenger ribonucleic acid (rGH-RBP mRNA) and protein were investigated at the electronmicroscopic level, using in situ hybridization and immunocytology, respectively, on ultrathin frozen sections of rat pituitary. Ultrastructural distribution of(125)I-bGH, 30 min after intracardiac administration was also performed in order to determine the pituitary cell types that bind the labeled hormone. In situ hybridization was performed using digoxigenin-labeled oligonucleotide probe revealed by indirect immunogold reaction. rGH-RBP mRNA was readily identified in the cytoplasmic matrix, associated with the endoplasmic reticulum and the nucleus of the somatotrophs, the lactotrophs and the gonadotrophs. No significant signal was detected in the corticotrophs or thyrotrophs. The number of gold particles in each pituitary cell type was estimated by direct counting, and was compared to the results of hybridization performed on rat liver sections as a control. The results showed that the level of rGH-RBP mRNA was higher in hepatocytes than in the pituitary cells, and was higher in the somatotrophs and lactotrophs than in the gonadotrophs. Immunocytological dectection of rGH-RBP was performed using two monoclonal antibodies (mAbs 43 and 263) directed against independent epitopes of the extracellular domain of the rGH-R. Indirect immunocytological detection showed regionalization of rGH-RBP; it was present in the cytoplasmic matrix and the nucleus of the hepatocytes and in discrete pituitary cells: somatotrophs, lactotrophs and gonadotrophs, but not in thyrotrophs or corticotrophs. Gold particle number was also higher in somatotrophs and lactotrophs than in gonadotrophs and higher in the nucleus compared to the cytoplasmic matrix. Radioiodinated GH was uptaken 30 min after injection by the same three pituitary cell types, showing evidence for the functional role of the GH receptor. In conclusion, we find that the cellular localization of rGH-RBP mRNA and protein is similar in discrete cell subpopulations of the pituitary, suggesting a direct effect of GH on somatotrophs, lactotrophs and gonadotrophs, through paracrine, autocrine or intracrine mechanisms

Cellular-Localization of the Growth-Hormone Receptor/binding Protein in the Human Anterior-Pituitary Gland

The increasing use of GH therapy has led to the description of its target cells in human tissues, but no data are yet available on the localization of the GH receptor in the human pituitary. In the present study, we used immunocytochemistry to detect the presence of GH receptor/binding protein (GHR/BP), and we examined its distribution among the different types of human anterior pituitary cells. Human pituitaries were taken from autopsies and were processed for embedding in parafin wax. Immunocytochemistry was performed by using monoclonal antibody 263 raised against purified rat and rabbit GHR/BP, which cross-reacts with the human GH receptor. In order to determine the types of cells that display immunoreactivity for GHR/BP, adjacent pituitary sections were used to detect immunoreactivity for GH, PRL, ACTH, TSH, LH, and FSH. Several controls were carried out to verify the specificity of the immunostaining. Receptor immunoreactivity was found in the cytoplasm and nuclei of the somatotrophs, lactotrophs, and gonadotrophs but not in the thyrotrophs or corticotrophs. In order to demonstrate that the detected GHR/BP immunoreactivity was not caused solely by a cellular capture, we also investigated the cellular distribution of GHR gene expression. This was performed by in situ hybridization with use of complementary oligonucleotidic radioactive probes encoding distinct domains of the GHR. Several tests were carried out to validate the detection of gene expression. In situ hybridization demonstrated the presence of GHR messenger RNAs in the anterior lobe of human pituitary, and examination of the signal strengthened the cell-specifity of GHR gene expression. These results demonstrate the presence of GHR/BP in discrete human pituitary cells and indicate a paracrine, autocrine, or intracrine role for GH in the pituitary