Immortalization of neuro-endocrine cells from adrenal tumors arising in SV40 T-transgenic mice

Useful cell lines derived from the adrenal medulla

Five approaches for the preparation of adrenal chromaffin cell lines have been developed. Initially, continuous chromaffin lines were derived from spontaneous pheochromocytoma tumors of the medulla, either from murine or human sources, such as the rat PC12 cell line and the human KNA and KAT45 cell lines. Over the last few decades, more sophisticated molecular methods have allowed for induced tumorigenesis and targeted oncogenesis in vivo, where isolation of specific populations of mouse cell lines of endocrine origin have resulted in model cells to examine a variety of regulatory pathways in the chromaffin phenotype. As well, conditional immortalization with retroviral infection of chromaffin precursors has provided homogeneous and expandable chromaffin cells for transplant studies in animal models of pain. This same strategy of immortalization with conditionally expressed oncogenes has been expanded recently to create the first disimmortalizable chromaffin cells, with an excisable oncogenic cassette, as might be envisioned for the creation of human chromaffin cell lines. Eventually, as we increase our understanding of regulating the phenotypic fate of chromaffin cells in vitro, stem or progenitor adrenal medullary cell lines will be derived as an alternative source for expansion and clinical use.

Spontaneously immortalized epithelial cells from mouse caput epididymidis

We report here on the characterization of tissue-culture cell lines derived from primary cultures of the mouse caput epididymidis epithelium. The cell lines were spontaneously immortalized without the use of transforming oncogenes. In defined conditions, our epididymal cells adopted various morphological features that resembles that of the in vivo epididymis epithelium such as a polarized organization and the presence of junctional structures at their apical/lateral membranes as revealed by electron microscopy analyses. Flow cytometry analysis revealed that we were dealing with homogenous cell populations that had reached a near-tetraploid state. RT-PCR assays were used in order to show that several genes that can be considered as markers of in vivo caput epididymidis epithelium activity were expressed in our cell lines confirming that these cells were indeed in a differentiated state close to their endogenous state.

Immortalization by large T-antigen of the adult epididymal duct epithelium

The SV40 large T-antigen has been widely used to convert various cell types to a transformed phenotype, and also to induce progressive tumours in transgenic animals. The objectives of this review are to compare and discuss three different approaches to generate epididymal epithelial cell lines using the large T-antigen. In the first approach, retroviral transfection of primary cultures was used to immortalize canine epididymal cells in vitro; the other two approaches used transgenic mice expressing the large T-antigen. In one of these in vivo approaches, a construct consisting of the coding sequence of a temperature sensitive (ts) SV40 large T-antigen was inserted in a mouse genome. When the cells are exposed to the permissive temperature of 33 degrees C, functional expression of the large T-antigen occurs and cells start to proliferate. In the second in vivo approach a tissue-specific promoter, the 5kb GPX5 promoter, was used to direct expression of the large T-antigen to the epididymal duct epithelium.

Immortalization of epididymal epithelium in transgenic mice expressing simian virus 40 T antigen: characterization of cell lines and regulation of the polyoma enhancer activator 3

In the present study epididymal epithelium was immortalized in transgenic mice by expressing simian virus 40 T antigen under a 5.0-kb mouse glutathione peroxidase 5 promoter (GPX5-Tag1). Epididymal tumorigenesis was associated with an increase in c-Myc expression, and a marked decrease in B-Myc expression, with a 500-fold lower level in the GPX5-Tag1 caput epididymis compared with wild-type caput. Furthermore, B-Myc was undetectable in the immortalized corpus and cauda epididymis. Hence, it is possible that the normally high B-Myc expression in the epididymis is one of the factors contributing to the highly resistant nature of epididymis toward immortalization. Morphologically different epithelial cell lines were generated from the immortalized epididymides, and the cells expressed several genes typical for epididymal epithelium, such as mouse epididymal 1, mouse epididymal protein 9, androgen and estrogen receptors, anion exchangers 2 and 4, retinoic acid receptor alpha, and polyoma enhancer activator 3 (PEA3). This indicated the differentiated status of the cells and their usefulness for analyzing epididymal gene expression in vitro. As PEA3 is considered to be one of the transcription factors responsible for epididymal gene expression, we further studied its regulation in epididymal cells in vitro. The data showed that PEA3 mRNA expression is regulated in the epididymis via protein kinase A and ERK signaling cascades. Inhibiting protein kinase A resulted in up-regulation and inhibiting ERK resulted in down-regulation of PEA3 mRNA, whereas no significant effect on PEA3 expression was found by modulating the protein kinase C, stress-activated p38, phosphoinositol 3-kinase and p70 S6 kinase cascades.

Temperature-dependent, neurotrophic factor-elicited, neuronal differentiation in adrenal chromaffin cell line immortalized with temperature-sensitive SV40 T-antigen

We established adrenal medullary cell lines from transgenic mice expressing an oncogene, the temperature-sensitive simian virus 40 large T-antigen, under the control of the tyrosine hydroxylase promoter. A clonal cell line, named tsAM5D, conditionally grew at a permissive temperature of 33 degrees C and exhibited the dopaminergic chromaffin cell phenotype as exemplified by the expression pattern of mRNA for catecholamine-synthesizing enzymes and secretory vesicle-associated proteins. tsAM5D cells proliferated at the permissive temperature in response to basic fibroblast growth factor (bFGF) and ciliary neurotrophic factor (CNTF). At a non-permissive temperature of 39 degrees C, bFGF and CNTF acted synergistically to differentiate tsAM5D cells into neuron-like cells. In addition, tsAM5D cells caused to differentiate by bFGF plus CNTF at 39 degrees C became dependent solely on nerve growth factor for their survival and showed markedly enhanced neurite outgrowth. In the presence of bFGF and CNTF, the morphological change induced by the temperature shift was associated with up-regulated expression of neuronal marker genes including neuron-specific enolase, growth-associated protein-43, microtubule-associated protein 2, neurofilament, and p75 neurotrophin receptor, indicating that the cells underwent neuronal differentiation. Thus, we demonstrated that tsAM5D cells could proliferate at permissive 33 degrees C, and also had the capacity to terminally differentiate into neuron-like cells in response to bFGF and CNTF when the oncogene was inactivated by shifting the temperature to non-permissive 39 degrees C. These results suggest that tsAM5D cells should be a good tool to allow a detailed study of mechanisms regulating neuronal differentiation.

TSPY-LTA transgenic mice develop endocrine tumors of the pituitary and adrenal gland

In an attempt to determine the susceptibility of spermatogonia to malignant transformation transgenic mice were generated harboring a 1.3 kb 5'-flanking region of the germ cell specific expressed human testis specific protein, Y-encoded gene fused with the simian virus 40 large T antigen (TAg). Unexpectedly, TAg expression in transgenic mice was also detected in somatic tissues. Between days 65 and 85 after birth most of the transgenic mice developed anterior lobe tumors of the pituitary gland and to a less extent medulla type tumors of the adrenal gland. In addition, a few older transgenic mice developed tumors of the seminal vesicle, but no testicular tumors were observed in transgenic mice up to an age of 5 months. The pituitary tumors were immunoreactive for anti-prolactin (PRL) and anti-adrenocorticotropic hormone (ACTH). PRL and corticosterone concentrations in serum of transgenic mice were significantly increased. Taken together, our studies provide a novel mouse model for pituitary adenomas displaying a unique combination of hormone expression by tumor cells secreting PRL and ACTH.

Immortalized chromaffin cells disimmortalized with Cre/lox site-directed recombination for use in cell therapy for pain after partial nerve injury

To prepare immortalized adrenal chromaffin cells for eventual clinical use, the immortalizing oncogene must be removed. We have utilized a Cre-mediated excision of a loxP-flanked Tag sequence to test whether immortalized chromaffin cells could be disimmortalized by this method. Cultures of embryonic rat adrenal cells were immortalized with the tsA-TN retroviral vector encoding the loxP-flanked temperature-sensitive allele of SV40 large T antigen (tsA-TN) and a positive/negative neo/HSV-TK sequence for selection with either G418 or gancyclovir, respectively. These cells were then infected with the 1710-CrePR1 bicistronic retroviral vector coding for a form of Cre modulatable by the synthetic steroid RU486. These immortalized loxTsTag/CrePR1/RAD cells expressed immunoreactivities (ir) for all the catecholamine enzymes: tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DbetaH), and phenylethanolamine-N-methyltransferase (PNMT). After initial incubation at 37 degrees C with RU486 for 3 days, followed by the addition of gancyclovir for 7 days, Tag-ir was not detectable in most of the surviving chromaffin cells, compared to 100% expression in immortalized loxTsTag/CreR1/RAD cells not treated with RU486 and gancyclovir. The expression of TH, DbetaH, and PNMT was increased after disimmortalization and the ability of disimmortalized cells to synthesize norepinephrine was also significantly increased compared to immortalized cells. When both types of chromaffin cells were transplanted in a model of neuropathic pain and partial nerve injury, both cell grafts were equally able to reverse the behavioral hypersensitivity induced by the injury. The use of Cre/lox site-directed disimmortalization of chromaffin cells that are able to deliver neuroactive molecules offers a novel approach to cell therapy.

Emerging cell and molecular strategies for the study and treatment of painful peripheral neuropathies

Pharmacologic treatment for the symptoms of painful neuropathy has been problematic, because there has been limited understanding of the underlying etiologies and systemic levels that an effective dose can have on multiple side effects. The use of molecular methods, such as gene deletion from knockout mice and cellular minipumps for delivery of biologic antinociceptive molecules, has led to a better understanding of the underlying mechanisms of the induction of intractable neuropathic pain. The initiation of an excitatory cascade after injury or disease leads to the induction of various second messenger systems, loss or down-regulation of the endogenous inhibitory spinal GABA system and central sensitization, causing such pain. The development and use of cellular minipumps, immortalized cell lines bioengineered to secrete various antinociceptive molecules for the reversal of neuropathic pain, makes cellular therapy a strategy for clinical use in the next few years. The development of molecular "disimmortalization" technologies will make the use of such engineered cell lines safe for human use. Direct somatic gene transfer for neuropathic pain will eventually overcome the problems associated with transplantation of non-autologous and xenogenic cells. These virus-mediated methods, although at the early stages of evolution and use, offer large-scale production of biologic agents that can be conveniently and confidently used for the long-term relief of chronic neuropathic pain in a clinical setting, without systemic effects or surgical interventions.

A novel stromal cell-dependent hematopoietic cell line established from temperature-sensitive SV40 T-antigen transgenic mice

A novel primitive hematopoietic cell line, THS119, was established from lineage marker negative (Lin-)/Sca-1+ cells from bone marrow of temperature-sensitive (ts) SV40 T-antigen transgenic mice after lengthy passaging by coculture with TBR59 bone marrow stromal cells. THS119 cells exhibited immature primitive hematopoietic cells such as forming cobblestones underneath the stromal cell layers. They retained properties of hematopoietic stem cells as shown by expression of c-Kit, Sca-1 and CD34low, but lacked hematopoietic lineage surface markers of differentiated hematopoietic cells (Gr-1, TER119, Mac-1, CD3, B220). RT-PCR analysis showed that THS119 cells exhibited multiple expression of both earlier developmental markers of myeloid, lymphoid and the hematopoietic cell specific transcription factors. THS119 cells showed temperature-dependent growth reflecting ts T-antigen, and their maintenance was TBR59 stromal cell-dependent. The requirement of stromal cells could not be replaced by cytokines, however, an IL-3 or IL-7 dependent cell line was generated after prolonged culture of THS119 cells on the stromal cells in the presence of these cytokines, and these cytokine-dependent cell lines exhibited phenotypes similar to the parental cells in their gene expression. SCF/c-Kit interaction is one factor required for their maintenance, but involvement of other factor(s) in the conditioned medium of TBR59 stromal cells was suggested. A novel immature hematopoietic cell line, THS119, may provide an appropriate experimental system to resolve how hematopoietic cells are kept in a primitive phase within a hematopoietic microenvironment.