title: Controlled-release particulate cytokine adjuvants for cancer therapy.
abstract: Cytokine therapy can induce tumor regression in cancer patients but systemic administration of cytokines is accompanied with severe toxicity. Loco-regional delivery represents an effective and less toxic alternative to systemic injection. However; the requirement for frequent repeated injections of recombinant cytokine or the logistical difficulties associated with gene-modification have limited wide-spread use of loco-regional therapy. A simpler alternative local delivery strategy involves the use of controlled-release cytokine depot formulations. These formulations provide the advantage that physiological doses of cytokines are directly released to the tumor microenvironment in a sustained manner. Anti-tumor efficacy of IL-2; IL-12; GM-CSF or TNFalpha-encapsulated polymer microspheres has been evaluated in syngeneic murine and human tumor /SCID mouse xenograft models. A single intra-tumoral injection of these formulations; particularly that of IL-12 in combination with GM-CSF or TNFalpha; promoted the regression of established primary tumors; induced systemic anti-tumor T- and NK-cell responses and achieved complete eradication of disseminated disease. Cellular and molecular analysis of post-therapy tumor microenvironment demonstrated that treatment promoted the activation of tumor-associated T-effector/memory cells; the elimination of CD4+ CD25+ Foxp3+ T-suppressors and the de novo priming of tumor-specific CD8+ T-effector cells. Long-term monitoring of post-therapy tumors revealed that reversal of intra-tumoral immune suppression was transient and that T-suppressor cells rapidly re-infiltrated tumors. Repeated treatment resurrected anti-tumor activity; however, therapeutic efficacy declined with each treatment cycle. The observed loss of therapeutic efficacy was associated with a progressive intensification of the post-treatment T-suppressor cell rebound. In contrast; depletion of T-suppressor cells with low dose chemotherapy prior to each cycle of treatment resulted in a dramatic enhancement of long-term therapeutic efficacy leading to complete remissions. Clinical implications of these findings are discussed herein.
authors.affiliation: Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, Buffalo, NY 14214, USA. negilmez@buffalo.edu
authors.forename: Nejat K
authors.initials: NK
authors.lastname: Egilmez
authors.forename: Mehmet O
authors.initials: MO
authors.lastname: Kilinc
authors.forename: Tao
authors.initials: T
authors.lastname: Gu
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Conway
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D000818:Animals; D002986:Clinical Trials as Topic; D016207:Cytokines / Q000008:administration & dosage* / Q000276:immunology; D003692:Delayed-Action Preparations; D006801:Humans; D009369:Neoplasms / Q000276:immunology / Q000628:therapy*
chemical_list: D000276:Adjuvants, Immunologic; D016207:Cytokines; D003692:Delayed-Action Preparations