STAT3 mediates C6-ceramide-induced cell death in chronic lymphocytic leukemia

The pathogenesis of chronic lymphocytic leukemia(CLL)is poorly understood and it remains incurable with current therapies.We have previously shown that nanoliposomal C6-ceramide(CNL)is an effective therapy in an in vivo murine model of CLL.However,the key signaling pathways mediating CNL-induced cell death in CLL remains unknown.We hypothesized that CNL targets STAT3,a critical regulator of hematopoietic biology.We observed that CNL treatment reduced phosphorylated STAT3 at both Y705 and S727 residues in CLL cell lines and patient cells.This,in turn,reduced STAT3 transcriptional activity and expression of critical STAT3-dependent survival factors like Mcl-1 and survivin.The effect of CNL on STAT3 was further confirmed ex vivo as shown by reduced STAT3 phosphorylation in xenograft tumors obtained from mice treated with CNL.CNL suppressed STAT3 phosphorylation at Y705 and S727 through reduction in BTK activity and MEK1/2 kinase/PKC activities,respectively.Moreover,a synergistic reduction in CLL cell viability was observed on co-treatment with CNL and the BTK inhibitor,ibrutinib.Expression of an oncogenic form of STAT3 conferred partial resistance to CNL,providing confirmation that STAT3 mediates CNL-induced cell death.Taken together,these findings provide the first body of evidence demonstrating ceramide regulation of STAT3 phosphorylation.These results are also the first to demonstrate an effect of ceramide on BTK,a critical kinase mediating the B-cell receptor signaling in CLL cells and suggest a novel and synergistic combination of CNL and BTK inhibitors for CLL treatment.

A nano-enhanced vaccine for metastatic melanoma immunotherapy

Aim:Despite the huge advancements in cancer therapies and treatments over the past decade,most patients with metastasized melanoma still die from the disease.This poor prognosis largely results from resistance to conventional chemotherapies and other cytotoxic drugs.We have previously identified 6 antigenic peptides derived from melanomas that have proven efficacious for activating CD4+T cells in clinical trials for melanoma.Our aim was to improve pharmacodynamics,pharmacokinetic and toxicological parameters by individually encapsulating each of the 6 melanoma helper peptides within their own immunogenic nanoliposomes.Methods:We modified these liposomes as necessary to account for differences in the peptides’chemical properties,resulting in 3 distinct formulations.To further enhance immunogenicity,we also incorporated KDO2,a TLR4 agonist,into the lipid bilayer of all nanoliposome formulations.We then conducted in vivo imaging studies in mice and ex vivo cell studies from 2 patient samples who both strongly expressed one of the identified peptides.Results:We demonstrate that these liposomes,loaded with the different melanoma helper peptides,can be readily mixed together and simultaneously delivered without toxicity in vivo.These liposomes are capable of being diffused to the secondary lymphoid organs very quickly and for at least 6 days.In addition,we show that these immunogenic liposomes enhance immune responses to specific peptides ex vivo.Conclusion:Lipid-based delivery systems,including nanoliposomes and lipid nanoparticles,have now been validated for pharmacological(small molecules,bioactive lipids)and molecular(mRNA,siRNA)therapeutic approaches.However,the utility of these formulations as cancer vaccines,delivering antigenic peptides,has not yet achieved the same degree of commercial success.Here,we describe the novel and successful development of a nanoliposome-based cancer vaccine for melanoma.These vaccines help to circumvent drug resistance by increasing a patient’s T cell response,making them more susceptible to checkpoint blockade therapy.