Regulation of dendritic cell expansion in aged athymic nude mice by FLT3 ligand

Signaling pathway activation drift during aging: Hutchinson-Gilford Progeria Syndrome fibroblasts are comparable to normal middle-age and old-age cells

For the past several decades, research in understanding the molecular basis of human aging has progressed significantly with the analysis of premature aging syndromes. Progerin, an altered form of lamin A, has been identified as the cause of premature aging in Hutchinson-Gilford Progeria Syndrome (HGPS), and may be a contributing causative factor in normal aging. However, the question of whether HGPS actually recapitulates the normal aging process at the cellular and organismal level, or simply mimics the aging phenotype is widely debated. In the present study we analyzed publicly available microarray datasets for fibroblasts undergoing cellular aging in culture, as well as fibroblasts derived from young, middle-age, and old-age individuals, and patients with HGPS. Using GeroScope pathway analysis and drug discovery platform we analyzed the activation states of 65 major cellular signaling pathways. Our analysis reveals that signaling pathway activation states in cells derived from chronologically young patients with HGPS strongly resemble cells taken from normal middle-aged and old individuals. This clearly indicates that HGPS may truly represent accelerated aging, rather than being just a simulacrum. Our data also points to potential pathways that could be targeted to develop drugs and drug combinations for both HGPS and normal aging.

Development of an immunotherapeutic adenovirus targeting hormone-independent prostate cancer

Background

To develop a targeting therapy for hormone-independent prostate cancer, we constructed and characterized conditionally replicating oncolytic adenovirus (Ad) equipped with mRFP (monomeric red fluorescence protein)/ttk (modified herpes simplex virus thymidine kinase). This construct was then further modified to express both mRFP/ttk and a soluble form of cytokine FLT3L (fms-related tyrosine kinase 3 ligand) simultaneously.

Methods

To construct the recombinant oncolytic adenovirus, E1a and E4 genes, which are necessary for adenovirus replication, were controlled by the prostate-specific enhancer sequence (PSES) targeting prostate cancer cells expressing prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA). Simultaneously, it expressed the mRFP/ttk fusion protein in order to be able to elicit the cytotoxic effect.

Results

The Ad5/35PSES.mRFP/ttk chimeric recombinant adenovirus was generated successfully. When replication of Ad5/35PSES.mRFP/ttk was evaluated in prostate cancer cell lines under fluorescence microscopy, red fluorescence intensity increased more in LNCaP cells, suggesting that the mRFP/ttk fusion protein was folded functionally. In addition, the replication assay including wild-type adenovirus as a positive control showed that PSES-positive cells (LNCaP and CWR22rv) permitted virus replication but not PSES-negative cells (DU145 and PC3). Next, we evaluated the killing activity of this recombinant adenovirus. The Ad5/35PSES. mRFP/ttk killed LNCaP and CWR22rv more effectively. Unlike PSES-positive cells, DU145 and PC3 were resistant to killing by this recombinant adenovirus. Finally, in order to potentiate therapeutic efficacy, we developed a recombinant adenovirus expressing multiexogenous genes, mRFP/ttk and sFLT3L.

Conclusion

In the present study, a replication-competent adenovirus was successfully designed to replicate conditionally in PSA-positive and PSMA-positive prostate cancer cells. This recombinant adenovirus is equipped with the fusion protein of suicidal and red-fluorescence fusion protein together with sFLT3L. This construct would be expected to have potent antitumor effects and deserves more extensive investigation.

Effect of aging and oral tolerance on dendritic cell function

Oral tolerance can be induced in some mouse strains by gavage or spontaneous ingestion of dietary antigens. In the present study, we determined the influence of aging and oral tolerance on the secretion of co-stimulatory molecules by dendritic cells (DC), and on the ability of DC to induce proliferation and cytokine secretion by naive T cells from BALB/c and OVA transgenic (DO11.10) mice. We observed that oral tolerance could be induced in BALB/c mice (N = 5 in each group) of all ages (8, 20, 40, 60, and 80 weeks old), although a decline in specific antibody levels was observed in the sera of both tolerized and immunized mice with advancing age (40 to 80 weeks old). DC obtained from young, adult and middle-aged (8, 20, and 40 weeks old) tolerized mice were less efficient (65, 17 and 20%, respectively) than DC from immunized mice (P < 0.05) in inducing antigen-specific proliferation of naive T cells from both BALB/c and DO11.10 young mice, or in stimulating IFN-g, IL-4 and IL-10 production. However, TGF-beta levels were significantly elevated in co-cultures carried out with DC from tolerant mice (P < 0.05). DC from both immunized and tolerized old and very old (60 and 80 weeks old) mice were equally ineffective in inducing T cell proliferation and cytokine production (P < 0.05). A marked reduction in CD86+ marker expression was observed in DC isolated from both old and tolerized mice (75 and 50%, respectively). The results indicate that the aging process does not interfere with the establishment of oral tolerance in BALB/c mice, but reduces DC functions, probably due to the decline of the expression of the CD86 surface marker.

The effect of aging on OX40 agonist-mediated cancer immunotherapy

Agents that enhance T cell co-stimulatory signaling have emerged as promising cancer immunotherapies. Our laboratory has been evaluating the TNF receptor co-stimulatory molecule, OX40, which has the capacity to augment critical aspects of T cell function and induce tumor regression in animal models. Effective stimulation of OX40 expressing T cells was accomplished with agonist antibodies to OX40 that were eventually translated into a clinical trial for cancer patients. A recent attempt to assess the affect of immune senescence on OX40 therapy, revealed a dramatic loss of efficacy of the agonist therapy in older tumor-bearing mice. The deficiency in OX40-enhanced anti-tumor responses in older mice correlated with a decrease in the number of differentiated effector T cells. Further investigation suggests that the underlying age-related decline in the agonist OX40-mediated T cell responses was not inherent to the T cells themselves, but related to the host environment. Thus, effective use of immunotherapies based on T cell co-stimulatory molecules may require additional modifications, such as immune stimulants to increase innate immunity, to address age-related defects that reside outside of the T cell and within the host environment.

Aging and the dendritic cell system: implications for cancer

The immune system shows a decline in responsiveness to antigens both with aging, as well as in the presence of tumors. The malfunction of the immune system with age can be attributed to developmental and functional alterations in several cell populations. Previous studies have shown defects in humoral responses and abnormalities in T cell function in aged individuals, but have not distinguished between abnormalities in antigen presentation and intrinsic T cell or B cell defects in aged individuals. Dendritic cells (DC) play a pivotal role in regulating immune responses by presenting antigens to naïve T lymphocytes, modulating Th1/Th2/Th3/Treg balance, producing numerous regulatory cytokines and chemokines, and modifying survival of immune effectors. DC are receiving increased attention due to their involvement in the immunobiology of tolerance and autoimmunity, as well as their potential role as biological adjuvants in tumor vaccines. Recent advances in the molecular and cell biology of different DC populations allow for addressing the issue of DC and aging both in rodents and humans. Since DC play a crucial role in initiating and regulating immune responses, it is reasonable to hypothesize that they are directly involved in altered antitumor immunity in aging. However, the results of studies focusing on DC in the elderly are conflicting. The present review summarizes the available human and experimental animal data on quantitative and qualitative alterations of DC in aging and discusses the potential role of the DC system in the increased incidence of cancer in the elderly.

Effect of aging on bone marrow-derived murine CD11c+CD4-CD8alpha- dendritic cell function

Dendritic cells (DCs) are actively used as cellular adjuvant in cancer immunotherapy. However, although DC immunotherapies primarily target the elderly population, little is known about the effect of aging on DC functions. Here, we compared the T-cell stimulation, cytokine production, and tumor surveillance functions of bone marrow-derived CD11c(+)CD4(-)CD8alpha(-) DCs of old and young C57BL/6 mice. Old immature bone marrow-derived CD4(-)CD8alpha(-) DCs (imDCs) were 4 times less effective than were young DCs in stimulating syngeneic CD4(+) T-cell proliferation. Old imDCs also have decreased DC-specific/intracellular adhesion molecule type 3-grabbing, nonintegrin (DC-SIGN) expression compared to young DCs. Interestingly, mice treated with the ovalbumin peptide-pulsed young DCs exhibited significantly greater tumor regression than with ovalbumin peptide-pulsed old DCs. Old terminally differentiated bone marrow-derived DCs (tDC) also have increased interleukin-10, but decreased interleukin-6 and tumor necrosis factor-alpha production. Taken together, these results have important implications in the clinical application of DC-based tumor immunotherapy in elderly persons.

Combined immunostimulation and conditional cytotoxic gene therapy provide long-term survival in a large glioma model

In spite of preclinical efficacy and recent randomized, controlled studies with adenoviral vectors expressing herpes simplex virus-1 thymidine kinase (HSV1-TK) showing statistically significant increases in survival, most clinical trials using single therapies have failed to provide major therapeutic breakthroughs. Because glioma is a disease with dismal prognosis and rapid progression, it is an attractive target for gene therapy. Preclinical models using microscopic brain tumor models (e.g., < or =0.3 mm3) may not reflect the pathophysiology and progression of large human tumors. To overcome some of these limitations, we developed a syngeneic large brain tumor model. In this model, administration of single therapeutic modalities, either conditional cytotoxicity or immunostimulation, fail. However, when various immunostimulatory therapies were delivered in combination with conditional cytotoxicity (HSV1-TK), only the combined delivery of fms-like tyrosine kinase ligand (Flt3L) and HSV1-TK significantly prolonged the survival of large tumor-bearing animals (> or =80%; P < or = 0.005). When either macrophages or CD4+ cells were depleted before administration of viral therapy, TK + Flt3L therapy failed to prolong survival. Meanwhile, depletion of CD8+ cells or natural killer cells did not affect TK + Flt3L efficacy. Spinal cord of animals surviving 6 months after TK + Flt3L were evaluated for the presence of autoimmune lesions. Whereas macrophages were present within the corticospinal tract and low levels of T-cell infiltration were detected, these effects are not indicative of an overt autoimmune disorder. We propose that combined Flt3L and HSV1-TK adenoviral-mediated gene therapy may provide an effective antiglioma treatment with increased efficacy in clinical trials of glioma.