Microtubule-Targeting Combined with HDAC Inhibition Is a Novel Therapeutic Strategy for Diffuse Intrinsic Pontine Gliomas

Diffuse intrinsic pontine gliomas (DIPG) are an incurable childhood brain cancer for which novel treatments are needed. DIPGs are characterized by a mutation in the H3 histone (H3K27M), resulting in loss of H3K27 methylation and global gene dysregulation. TRX-E-009-1 is a novel anticancer agent with preclinical activity demonstrated against a range of cancers. We examined the antitumor activity of TRX-E-009-1 against DIPG neurosphere cultures and observed tumor-specific activity with IC50s ranging from 20 to 100 nmol/L, whereas no activity was observed against normal human astrocyte cells. TRX-E-009-1 exerted its anti-proliferative effect through the induction of apoptotic pathways, with marked increases in cleaved caspase 3 and cleaved PARP levels, while also restoring histone H3K27me3 methylation. Co-administration of TRX-E-009-1 and the histone deacetylase (HDAC) inhibitor SAHA extended survival in DIPG orthotopic animal models. This antitumor effect was further enhanced with irradiation. Our findings indicate that TRX-E-009-1, combined with HDAC inhibition, represents a novel, potent therapy for children with DIPG.

Depletion of white adipose tissue in cancer cachexia syndrome is associated with inflammatory signaling and disrupted circadian regulation

Involuntary weight loss in patients with cancer is the hallmark of cancer cachexia. The etiology of cachexia is multifactorial involving loss of skeletal muscle and adipose tissue associated with high systemic levels of acute phase proteins and inflammatory cytokines. While muscle wasting overtly impacts on cancer patient quality of life, loss of lipid depots represents a sustained energy imbalance. In this study fat depletion was examined in Colon-26 model of cancer cachexia, which is a widely used rodent model of this syndrome. We investigated diurnal expression of circadian rhythm regulators as well as key mediators of energy metabolism and cytokine signaling. Mice bearing the C26 tumour exhibited reduced adipose mass, elevated adipose tissue lipolysis and a 5-fold increase in plasma levels of free fatty acids. These changes were associated with activated IL-6 signaling in WAT through a 3-fold increase in phosphorylated STAT3 and high SOCS3 gene expression levels. In addition perturbations in circadian regulation of lipid metabolism were also observed. Lipid catabolism did not appear to be influenced by the classical PKA pathway activating the lipase HSL. ATGL protein levels were elevated 2-fold in cachectic mice while 4-fold increase phosphorylated ACC and a 2-fold decrease in phosphorylated 4EBP1 was observed indicating that lipid metabolism is modulated by the ATGL & AMPK/mTOR pathways. This study provides evidence for activation of cytokine signaling and concomitant alterations in circadian rhythm and regulators of lipid metabolism in WAT of cachectic animals.

Targeting fibroblast-like synovial cells at sites of inflammation with peptide targeted liposomes results in inhibition of experimental arthritis

In this study we examined a synovium-specific targeted liposomal drug delivery system for its ability to localize and release its drug cargo to inflamed joints. Targeted liposomes were tested in vitro for binding to synovial fibroblast like (FLS) and endothelial cells using flow cytometry and in vivo for localization to joints using a rat model of adjuvant induced arthritis (AIA). Targeted liposomes were then loaded with anti-arthritic medications and examined for clinical efficacy in AIA. Targeted liposomes specifically bound to rabbit FLS and human FLS and showed a 7-10 fold increase in vivo localization in affected joints compared to unaffected joints. Histological sections from rats treated with prednisone and a new immunosuppressive peptide CP showed minimal inflammation. This report substantiates the ability of the novel FLS sequence to target liposomal drug delivery and offers an alternative therapeutic approach for the treatment of arthritis.

Toward understanding the role of leptin and leptin receptor antagonism in preclinical models of rheumatoid arthritis

A potential link between obesity, circulating leptin levels and autoimmune disease symptoms suggests that targeting the leptin receptor (ObR) might be a viable novel strategy to combat rheumatoid arthritis (RA). However, studies in animal models and evaluation of clinical cases did not provide clear view on leptin's involvement in RA. To validate ObR as RA target, we used our peptide-based ObR agonists and antagonist in different in vitro and in vivo models of the disease. In human peripheral blood mononuclear cells, leptin and its agonist fragment, desI(2)-E1/Aca, moderately induced constitutive activation of a major proinflammatory transcription factor, NF-κB, while the ObR antagonist peptide Allo-aca inhibited the process. Leptin administration itself did not induce arthritis in rats, but worsened the clinical condition of mice given K/BxN serum transfer arthritis. Simultaneous administration of Allo-aca reduced leptin-dependent increase in disease severity by more than 50%, but the antagonist was ineffective when injected with a 3-day delay. In rats inflicted with mild adjuvant-induced arthritis, both leptin and Allo-aca reduced the extent of joint swelling and the number of arthritic joints. In a more aggressive disease stage, Allo-aca decreased the number of arthritic joints in a dose-dependent manner but did not affect other arthritis markers. In summary, leptin exerts diverse effects on RA depending on the experimental model. This might reflect the heterogeneous character of RA, which is differently impacted by leptin and is unmasked by ObR antagonism. Nevertheless, the results suggest that ObR antagonists might become useful therapeutics in leptin-sensitive early stages of RA.

The potential of liposomal drug delivery for the treatment of inflammatory arthritis

OBJECTIVE

To review the use of liposomes as a delivery agent in inflammatory arthritis.

METHODS

The literature on liposomes and liposomal drug delivery for the treatment of inflammatory arthritis was reviewed. A PubMed search of articles in the English-language journals from 1965 to 2007 was performed. The index words used were as follows: "rheumatoid arthritis," "liposomes," and "targeted delivery." Papers identified were reviewed, abstracted, and summarized.

RESULTS

Liposomes have the capacity to be used as delivery and targeting agents for the administration of antirheumatic drugs at lower doses with reduced toxicity. In other areas of medicine, the pace of progress has been rapid. In the case of infectious diseases and cancer, liposomal drug delivery has progressed and developed into commercially viable therapeutic options for the treatment of fungal infections (amphotericin B), or metastatic breast cancer and Kaposi sarcoma (doxorubicin, daunorubicin), respectively. In arthritis, the efficacy of prednisolone-loaded long-circulating liposomes is currently being evaluated in a phase II clinical trial. Liposome's application to arthritis is still in its infancy but appears promising as new patents are filed. With improvements in liposomal formulation and targeted synovial delivery, liposomes offer increased therapeutic activity and improvement in the risk-benefit ratio.

CONCLUSION

Recent research into synovial targets and improved liposomal formulations continues to improve our capacity to use liposomes for targeted delivery. With time, this approach has the potential to improve drug delivery and reduce systemic complications.