Retinoblastoma (RB) is the most common intraocular cancer in children worldwide. Current treatments mainly involve combinations of chemotherapies, cryotherapies, and laser-based therapies. Severe or late-stage disease may require enucleation or lead to fatality. Recently, RB has been shown to arise from cone precursor cells, which have high MDM2 levels to suppress p53-mediated apoptosis. This finding leads to the hypothesis that restoring apoptosis mechanisms in RBs could specifically kill the cancer cells without affecting other retinal cells. We have previously reported involvement of an extrapituitary signaling pathway of the growth hormone-releasing hormone (GHRH) in the retina. Here we show that the GHRH receptor (GHRH-R) is highly expressed in RB cells but not in other retinal cells. We induced specific apoptosis with two different GHRH-R antagonists, MIA-602 and MIA-690. Importantly, these GHRH-R antagonists do not trigger apoptosis in other retinal cells such as retinal pigmented epithelial cells. We delineated the gene expression profiles regulated by GHRH-R antagonists and found that cell proliferation genes and apoptotic genes are down-and up-regulated, respectively. Our results reveal the involvement of GHRH-R in survival and proliferation of RB and demonstrate that GHRH-R antagonists can specifically kill the RB cells.GHRH pathway | GHRH-R antagonist | retinoblastoma | growth hormonereleasing hormone | apoptosis R etinoblastoma (RB) is the most common childhood intraocular malignancy and accounts for approximately 3% of all childhood cancers (1). It has been reported to arise from the cone precursor cells of the retina that transduce light into electrical signals (2). RB is thought to result largely from the loss of function of both copies of RB1 gene located on human chromosome 13q14 (3, 4). Functional disruption of RB1 can be generated by the somatic inactivation of both RB1 alleles, or with a germline RB1 mutation in one allele and a somatic inactivation of the second RB1 allele (5). The RB1 protein acts as a signal transducer connecting cell cycle progression with the transcription machinery (6). There are four steps in the mitotic cycle of a cell: G1, S, G2, and cell division. In the G1 phase, cyclin D is highly expressed, which leads to activation of cyclin-dependent kinases (CDKs) 4 and 6. CDK4 and CDK6 then phosphorylate RB1, inhibiting RB1 binding to the transcription factor E2F (7, 8). As a result, the RB1-free E2F binds to promotors of several genes and turns on their expressions to induce cell cycle progression into S phase, the DNA synthesis phase. Similarly, cells carrying RB1 mutations would also progress into S phase. Normally, this premature progression into S phase would trigger apoptosis to prevent uncontrolled cell proliferation (9). However, it has been reported that the cone precursor cells express high levels of MDM2, a protein that suppresses apoptosis mediated by p53 (2). Therefore, cone precursor cells in patients carrying RB1 mutations pass through the cell cycle faster an...

SummarySystemic lupus erythematosus (SLE) is an autoimmune disease that is characterized by high morbidity and mortality and its treatment remains challenging. Dendritic cells (DCs) have been shown to participate in the initiation and perpetuation of lupus pathogenesis and the DCs that can induce tolerogenicity appear as potential cell‐based therapy in this condition. In this study, we examined the in vitro tolerogenic properties of bone‐marrow derived DCs (BMDCs) in the murine lupus setting. We used lentiviral transduction of RelB‐silencing short hairpin RNA to modify the expression of RelB, a key transcription factor regulating DC maturation, in BMDCs from MRL/MpJ mice. Tolerogenic properties of RelB‐modified DCs were compared with scrambled control (SC) ‐modified DCs. RelB expression was found to be significantly reduced in RelB‐modified DCs derived from MRL/MpJ mice, wild‐type of the same genetic background as MRL/lpr lupus‐prone mice. These MRL/MpJ RelB‐modified DCs displayed semi‐mature phenotype with expression of lower levels of co‐stimulatory molecules compared with SC‐modified DCs. RelB‐modified DCs were found to be low producers of interleukin‐12p70 (IL‐12p70) and could induce hyporesponsiveness of splenic T cells from MRL/MpJ and MRL/lpr mice. Furthermore, they down‐regulated interferon‐γ expression and induced IL‐10‐producing T cells in MRL/MpJ splenocytes, and attenuated interferon‐γ and IL‐17 expression in MRL/lpr splenic CD4+ lymphocytes. Splenocytes primed by RelB‐modified DCs demonstrated antigen‐specific suppressive effects on allogeneic splenocytes. In conclusion, RelB‐silencing in DCs generates DCs of tolerogenic properties with immunomodulatory function and appears as potential option of cell‐targeted therapy.

The innate cytokine IL-33 is increasingly recognised to possess biological effects on various immune cells. We have previously demonstrated elevated serum level of soluble ST2 in patients with active systemic lupus erythematosus suggesting involvement of IL-33 and its receptor in the lupus pathogenesis. This study sought to examine the effect of exogenous IL-33 on disease activity of pre-disease lupus-prone mice and the underlying cellular mechanisms. Recombinant IL-33 was administered to MRL/lpr mice for 6 weeks whereas control group received phosphate-buffered saline. IL-33-treated mice displayed less proteinuria, renal histological inflammatory changes and had lower serum levels of pro-inflammatory cytokines including IL-6 and TNF-α. Renal tissue and splenic CD11b+ extracts showed features of M2 polarisation with elevated mRNA expression of Arg1, FIZZI and reduced iNOS. These mice also had increased IL-13, ST2, Gata3 and Foxp3 mRNA expression in renal and splenic tissues. Kidneys of these mice displayed less CD11b+ infiltration, had downregulated MCP-1 and increased infiltration of Foxp3 expressing cells. Splenic CD4+ T cells showed increased ST2 expressing CD4+Foxp3+ population and reduced IFN-γ+ population. There were no differences in serum anti-dsDNA antibodies and renal C3 and IgG2a deposit in these mice. Exogenous IL-33 was found to ameliorate disease activity in lupus-prone mice with induction of M2 polarisation, Th2 response and expansion of regulatory T cells. IL-33 likely orchestrated autoregulation of these cells through upregulation of ST2 expression.