XMRV induces cell migration, cytokine expression and tumor angiogenesis: are 22Rv1 cells a suitable prostate cancer model?

Stimulation of Angiotensin II Type 2 Receptor Modulates Pro-Inflammatory Response in Microglia and Macrophages: Therapeutic Implications for the Treatment of Stroke

BACKGROUND

Sustained microglial activation contributes to the development of post-stroke cognitive impairment (PSCI). Compound 21 (C21), an angiotensin II type 2 receptor agonist, has shown some neurovascular protection after stroke. This study aimed to investigate the direct anti-inflammatory effects of C21 on macrophages, as well as brain innate immune cells.

METHODS

Murine microglial cell line (C8-B4) and RAW 264.7 macrophages were exposed to lipopolysaccharide (LPS) and co-treated with C21. Pro-inflammatory mediators were assessed via RT-qPCR and ELISA. Cellular reactive oxygen species (ROS) were evaluated via CellROXGreen staining, and nitrate production was assessed using Griess assay.

RESULTS

C21 suppressed LPS-induced inflammation and ROS generation in both cells. In microglia, C21 blunted LPS-induced mRNA expression of IL-1β, IL-12b, COX-1, iNOS, and IL-6. A similar pattern was observed in macrophages, where C21 suppressed LPS-induced IL-1β, TNF-α, and CXCL1 expression. These anti-inflammatory effects in microglia and macrophages were associated with increased neuroprotective gene expression, including GDNF and BDNF, in a dose-dependent manner.

CONCLUSIONS

Our findings suggest a protective effect of C21 against the inflammatory response, in both macrophages and microglia, via suppression of the release of pro-inflammatory cytokines/chemokines and the generation of ROS while stimulating the production of neurotrophic factors.

Epigallocatechin 3-gallate: From green tea to cancer therapeutics

Epigallocatechin 3-gallate (EGCG) possesses various biological functions, including anti-cancer and anti-inflammatory properties. EGCG is an abundant polyphenolic component originating from green tea extract that has exhibited versatile bioactivities in combating several cancers. This review highlights the pharmacological features of EGCG and its therapeutic implications in cancer and other metabolic diseases. It modulates numerous signaling pathways, regulating cells' undesired survival and proliferation, thus imparting strong tumor chemopreventive and therapeutic effects. EGCG initiates cell death through the intrinsic pathway and causes inhibition of EGFR, STAT3, and ERK pathways in several cancers. EGCG alters and inhibits ERK1/2, NF-κB, and Akt-mediated signaling, altering the Bcl-2 family proteins ratio and activating caspases in tumor cells. This review focuses on anti-cancer, anti-oxidant, anti-inflammatory, anti-angiogenesis, and apoptotic effects of EGCG. We further highlighted the potential of EGCG in different types of cancer, emphasizing clinical trials formulations that further improve our understanding of the therapeutic management of cancer and inflammatory diseases.

Stem cells and the role of ETS transcription factors in the differentiation hierarchy of normal and malignant prostate epithelium

Prostate cancer is the most common cancer of men in the UK and accounts for a quarter of all new cases. Although treatment of localised cancer can be successful, there is no cure for patients presenting with invasive prostate cancer and there are less treatment options. They are generally treated with androgen-ablation therapies but eventually the tumours become hormone resistant and patients develop castration-resistant prostate cancer (CRPC) for which there are no further successful or curative treatments. This highlights the need for new treatment strategies. In order to prevent prostate cancer recurrence and treatment resistance, all the cell populations in a heterogeneous prostate tumour must be targeted, including the rare cancer stem cell (CSC) population. The ETS transcription factor family members are now recognised as a common feature in multiple cancers including prostate cancer; with aberrant expression, loss of tumour suppressor function, inactivating mutations and the formation of fusion genes observed. Most notably, the TMPRSS2-ERG gene fusion is present in approximately 50% of prostate cancers and in prostate CSCs. However, the role of other ETS transcription factors in prostate cancer is less well understood. This review will describe the prostate epithelial cell hierarchy and discuss the evidence behind prostate CSCs and their inherent resistance to conventional cancer therapies. The known and proposed roles of the ETS family of transcription factors in prostate epithelial cell differentiation and regulation of the CSC phenotype will be discussed, as well as how they might be targeted for therapy.

Frequent infection of human cancer xenografts with murine endogenous retroviruses in vivo

Infection of human cancer xenografts in mice with murine leukemia viruses (MLVs) is a long-standing observation, but the likelihood of infection in vivo and its biological consequences are poorly understood. We therefore conducted a prospective study in commonly used xenograft recipient strains. From BALB/c nude mice engrafted with MCF7 human mammary carcinoma cells, we isolated a virus that was virtually identical to Bxv1, a locus encoding replication-competent xenotropic MLV (XMLV). XMLV was detected in 9/17 (53%) independently isolated explants. XMLV was not found in primary leukemias or in THP1 leukemia cells grown in Bxv1-negative NSG (NOD/SCID/γCnull) mice, although MCF7 explants harbored replication-defective MLV proviruses. To assess the significance of infection for xenograft behavior in vivo, we examined changes in growth and global transcription in MCF7 and the highly susceptible Raji Burkitt lymphoma cell line chronically infected with XMLV. Raji cells showed a stronger transcriptional response that included up-regulation of chemokines and effectors of innate antiviral immunity. In conclusion, the risk of de novo XMLV infection of xenografts is high in Bxv1 positive mice, while infection can have positive or negative effects on xenograft growth potential with significant consequences for interpretation of many xenograft studies.

The saga of XMRV: a virus that infects human cells but is not a human virus

Xenotropic murine leukemia virus-related virus (XMRV) was discovered in 2006 in a search for a viral etiology of human prostate cancer (PC). Substantial interest in XMRV as a potentially new pathogenic human retrovirus was driven by reports that XMRV could be detected in a significant percentage of PC samples, and also in tissues from patients with chronic fatigue syndrome (CFS). After considerable controversy, etiologic links between XMRV and these two diseases were disproven. XMRV was determined to have arisen during passage of a human PC tumor in immunocompromised nude mice, by activation and recombination between two endogenous murine leukemia viruses from cells of the mouse. The resulting XMRV had a xentropic host range, which allowed it replicate in the human tumor cells in the xenograft. This review describes the discovery of XMRV, and the molecular and virological events leading to its formation, XMRV infection in animal models and biological effects on infected cells. Lessons from XMRV for other searches of viral etiologies of cancer are discussed, as well as cautions for researchers working on human tumors or cell lines that have been passed through nude mice, includingpotential biohazards associated with XMRV or other similar xenotropic murine leukemia viruses (MLVs).

Infection of Xenotransplanted Human Cell Lines by Murine Retroviruses: A Lesson Brought Back to Light by XMRV

Infection of xenotransplanted human cells by xenotropic retroviruses is a known phenomenon in the scientific literature, with examples cited since the early 1970s. However, arguably, until recently, the importance of this phenomenon had not been largely recognized. The emergence and subsequent debunking of Xenotropic Murine leukemia virus-Related Virus (XMRV) as a cell culture contaminant as opposed to a potential pathogen in several human diseases, notably prostate cancer and Chronic Fatigue Syndrome, highlighted a potential problem of murine endogenous gammaretroviruses infecting commonly used human cell lines. Subsequent to the discovery of XMRV, many additional cell lines that underwent xenotransplantation in mice have been shown to harbor murine gammaretroviruses. Such retroviral infection poses the threat of not only confounding experiments performed in these cell lines via virus-induced changes in cellular behavior but also the potential infection of other cell lines cultured in the same laboratory. Thus, the possibility of xenotropic retroviral infection of cell lines may warrant additional precautions, such as periodic testing for retroviral sequences in cell lines cultured in the laboratory.

Xenotropic MLV envelope proteins induce tumor cells to secrete factors that promote the formation of immature blood vessels

Background

Xenotropic Murine leukemia virus-Related Virus (XMRV) is a γ-retrovirus initially reported to be present within familial human prostate tumors and the blood of patients with chronic fatigue syndrome. Subsequent studies however were unable to replicate these findings, and there is now compelling evidence that the virus evolved through rare retroviral recombination events in human tumor cell lines established through murine xenograft experiments. There is also no direct evidence that XMRV infection has any functional effects that contribute to tumor pathogenesis.

Results

Herein we describe an additional xenotropic MLV, “B4rv”, found in a cell line derived from xenograft experiments with the human prostate cancer LNCaP cell line. When injected subcutaneously in nude mice, LNCaP cells infected with XMRV or B4rv formed larger tumors that were highly hemorrhagic and displayed poor pericyte/smooth muscle cell (SMC) investment, markers of increased metastatic potential. Conditioned media derived from XMRV- or B4rv-infected LNCaPs, but not an amphotropic MLV control virus infected LNCaPs, profoundly decreased expression of marker genes in cultured SMC, consistent with inhibition of SMC differentiation/maturation. Similar effects were seen with a chimeric virus of the amphotropic MLV control virus containing the XMRV env gene, but not with an XMRV chimeric virus containing the amphotropic MLV env gene. UV-inactivated XMRV and pseudovirions that were pseudotyped with XMRV envelope protein also produce conditioned media that down-regulated SMC marker gene expression in vitro.

Conclusions

Together these results indicate that xenotropic MLV envelope proteins are sufficient to induce the production of factors by tumor cells that suppress vascular SMC differentiation, providing evidence for a novel mechanism by which xenotropic MLVs might alter tumor pathogenesis by disrupting tumor vascular maturation. Although it is highly unlikely that either XMRV or B4Rv themselves infect humans and are pathogenic, the results suggest that xenograft approaches commonly used in the study of human cancer promote the evolution of novel retroviruses with pathogenic properties.