title: Reversing tumor immune suppression with intratumoral IL-12: activation of tumor-associated T effector/memory cells, induction of T suppressor apoptosis, and infiltration of CD8+ T effectors.
abstract: A single intratumoral injection of IL-12 and GM-CSF-loaded slow-release microspheres induces T cell-dependent eradication of established primary and metastatic tumors in a murine lung tumor model. To determine how the delivery of cytokines directly to the microenvironment of a tumor nodule induces local and systemic antitumor T cell activity, we characterized therapy-induced phenotypic and functional changes in tumor-infiltrating T cell populations. Analysis of pretherapy tumors demonstrated that advanced primary tumors were infiltrated by CD4+ and CD8+ T cells with an effector/memory phenotype and CD4+CD25+Foxp3+ T suppressor cells. Tumor-associated effector memory CD8+ T cells displayed impaired cytotoxic function, whereas CD4+CD25+Foxp3+ cells effectively inhibited T cell proliferation demonstrating functional integrity. IL-12/GM-CSF treatment promoted a rapid up-regulation of CD43 and CD69 on CD8+ effector/memory T cells, augmented their ability to produce IFN-gamma, and restored granzyme B expression. Importantly, treatment also induced a concomitant and progressive loss of T suppressors from the tumor. Further analysis established that activation of pre-existing effector memory T cells was short-lived and that both the effector/memory and the suppressor T cells became apoptotic within 4 days of treatment. Apoptotic death of pre-existing effector/memory and suppressor T cells was followed by infiltration of the tumor with activated, nonapoptotic CD8+ effector T lymphocytes on day 7 posttherapy. Both CD8+ T cell activation and T suppressor cell purge were mediated primarily by IL-12 and required IFN-gamma. This study provides important insight into how local IL-12 therapy alters the immunosuppressive tumor milieu to one that is immunologically active, ultimately resulting in tumor regression.
authors.affiliation: J.G. Brown Cancer Center, School of Medicine, University of Louisville, Louisville, KY 40202, USA.
authors.forename: Mehmet O
authors.initials: MO
authors.lastname: Kilinc
authors.forename: Karanvir S
authors.initials: KS
authors.lastname: Aulakh
authors.forename: Raji E
authors.initials: RE
authors.lastname: Nair
authors.forename: Stacy A
authors.initials: SA
authors.lastname: Jones
authors.forename: Pascale
authors.initials: P
authors.lastname: Alard
authors.forename: Michele M
authors.initials: MM
authors.lastname: Kosiewicz
authors.forename: Nejat K
authors.initials: NK
authors.lastname: Egilmez
mesh_terms: D002282:Adenocarcinoma, Bronchiolo-Alveolar / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D019496:Cancer Vaccines / Q000008:administration & dosage / Q000627:therapeutic use; D016923:Cell Death / Q000276:immunology; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000276:immunology*; D002478:Cells, Cultured; D005260:Female; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000008:administration & dosage / Q000627:therapeutic use; D007156:Immunologic Memory; D015552:Injections, Intralesional; D018664:Interleukin-12 / Q000008:administration & dosage* / Q000627:therapeutic use; D053645:Interleukin-2 Receptor alpha Subunit / Q000096:biosynthesis; D008175:Lung Neoplasms / Q000276:immunology / Q000473:pathology / Q000628:therapy*; D008213:Lymphocyte Activation / Q000276:immunology; D016246:Lymphocytes, Tumor-Infiltrating / Q000276:immunology / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D008863:Microspheres; D050378:T-Lymphocytes, Regulatory / Q000276:immunology* / Q000378:metabolism / Q000473:pathology
chemical_list: D019496:Cancer Vaccines; D053645:Interleukin-2 Receptor alpha Subunit; D018664:Interleukin-12; D016178:Granulocyte-Macrophage Colony-Stimulating Factor