Hill

Jamie L. Harden

Machiels

Mehmet O. Kilinc

Mihich

Motoyoshi

Nejat K. Egilmez

Rachael B. Rowswell-Turner

Raji E. Nair

Reddy

Reilly

Tao Gu

Abstract
               Intratumoral delivery of IL-12 and GM-CSF induces local and systemic antitumor CD8+ T cell activation and tumor kill. However, the effector response is transient and is rapidly countered by CD4+ Foxp3+ T suppressor cell expansion. To determine whether depletion of the pre-existing T suppressor cell pool prior to treatment could diminish posttherapy regulatory cell resurgence, FVBneuN mice bearing advanced spontaneous mammary tumors were treated with cyclophosphamide (CY) 1 d before IL-12/GM-CSF therapy. Administration of CY mediated a significant delay in the post–IL-12/GM-CSF T suppressor cell rebound, resulting in a 7-fold increase in the CD8+ CTL/T suppressor cell ratio, a 3-fold enhancement of CTL cytotoxicity, and an extension of the effector window from 3 to 7 d. In long-term therapy studies, chronic chemoimmunotherapy promoted a dramatic enhancement of tumor regression, resulting in complete cure in 44% of the mice receiving CY plus IL-12/GM-CSF. Tumor eradication in the chronic therapy setting was associated with the ability to repeatedly rescue and maintain cytotoxic CD8+ T cell activity. These findings demonstrated that chronic administration of CY in conjunction with immune therapy enhances the initial induction of antitumor T effector cells and, more importantly, sustains their cytotoxic activity over the long-term via persistent blockade of homeostatic counter-regulation.</jats:p

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The Journal of Immunology

Chronic Chemoimmunotherapy Achieves Cure of Spontaneous Murine Mammary Tumors via Persistent Blockade of Posttherapy Counter-Regulation

Chronic Chemoimmunotherapy Achieves Cure of Spontaneous Murine Mammary Tumors via Persistent Blockade of Posttherapy Counter-Regulation

Abstract

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