Absence of XMRV and Closely Related Viruses in Primary Prostate Cancer Tissues Used to Derive the XMRV-Infected Cell Line 22Rv1

The 22Rv1 cell line is widely used for prostate cancer research and other studies throughout the world. These cells were established from a human prostate tumor, CWR22, that was serially passaged in nude mice and selected for androgen independence. The 22Rv1 cells are known to produce high titers of xenotropic murine leukemia virus-related virus (XMRV). Recent studies suggested that XMRV was inadvertently created in the 1990's when two murine leukemia virus (MLV) genomes (pre-XMRV1 and pre-XMRV-2) recombined during passaging of the CWR22 tumor in mice. The conclusion that XMRV originated from mice and not the patient was based partly on the failure to detect XMRV in early CWR22 xenografts. While that deduction is certainly justified, we examined the possibility that a closely related virus could have been present in primary tumor tissue. Here we report that we have located the original prostate tumor tissue excised from patient CWR22 and have assayed the corresponding DNA by PCR and the tissue sections by fluorescence in situ hybridization for the presence of XMRV or a similar virus. The primary tumor tissues lacked mouse DNA as determined by PCR for intracisternal A type particle DNA, thus avoiding one of the limitations of studying xenografts. We show that neither XMRV nor a closely related virus was present in primary prostate tissue of patient CWR22. Our findings confirm and reinforce the conclusion that XMRV is a recombinant laboratory-generated mouse virus that is highly adapted for human prostate cancer cells

Retrotransposons and the evolution of mammalian gene expression

Transposable elements, and retroviral-like elements in particular, are a rich potential source of genetic variation within a host's genome. Many mutations of endogenous genes in phylogenetically diverse organisms are due to insertion of elements that affect gene expression by altering the normal pattern of regulation. While few such associations are known to have been maintained over time, two recently elucidated examples suggest transposable elements may have a significant impact in evolution of gene expression. The first example, concerning the mouse sex-limited protein ( Slp ), clearly establishes that ancient retroviral enhancer sequences now confer hormonal dependence on the adjacent gene. The second example shows that within the human amylase gene family, salivary specific expression has arisen due to inserted sequences, deriving perhaps from a conjunction of two retrotransposable elements.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42800/1/10709_2004_Article_BF00133720.pd

Binding and structural characteristics of a soluble lactogen-binding protein from rabbit mammary-gland cytosol

Specific receptors for prolactin (PRL) are known to be present on plasma membranes and intracellular membranes of mammary gland. We now report, however, the detection and characterization of a soluble lactogen-specific binding protein in high-speed (200,000 g) cytosolic preparations from pregnant- and non-pregnant-rabbit mammary gland. The binding protein was not detectable by poly(ethylene glycol) precipitation; instead, bound and free 125I-labelled human growth hormone (hGH; a potent lactogen) was separated using a mini-gel filtration technique. Specific binding of 125I-hGH reached an apparent equilibrium between 10 and 14 h at 21-23 degrees C. It was dependent on mammary-gland protein concentration and, partially, on Ca2+ or Mg2+ concentrations. Scatchard analysis revealed steep curvilinear plots, the high-affinity component having a KA of approximately 3 × 10(10) M-1. Gel filtration on calibrated Ultrogel AcA34 columns of 125I-hGH-cytosol complexes or of cytosol alone, followed by measurement of 125I-hGH binding in each eluted fraction, indicated that the binding protein had an Mr of 33,000-43,000. A specific binding protein of the same size was observed when 125I-ovine or -human PRL, but not 125I-bovine GH, was used as ligand. The apparent lactogenic specificity was confirmed by a lack of cross-reactivity of the binding protein with an anti-[GH receptor (rabbit liver)] monoclonal antibody. Polyacrylamide-gel electrophoresis of 125I-hGH covalently cross-linked to cytosol with disuccinimidyl suberate revealed binding proteins of Mr 35,000 (non-reduced) and 37,000 (reduced), results comparable with those obtained by gel filtration and indicating an absence of inter-subunit disulphide bonds. These studies have shown the presence of an apparently naturally soluble lactogen-binding protein in the cytosolic fraction of rabbit mammary gland. The relationship between this binding protein and the membrane PRL receptor is not yet known.</jats:p