DNA vaccination with all-trans retinoic acid treatment induces long-term survival and elicits specific immune responses requiring CD4+ and CD8+ T-cell activation in an acute promyelocytic leukemia mouse model

Abstract

IntroductionDespite improved molecular characterization of malignancies and development of targeted therapies, 1 acute leukemia is not curable and few patients survive more than 10 years after diagnosis. 2,3 To further improve outcome, we studied the potential efficacy of boosting the patient's immune response. Therapeutic vaccination aimed at promoting T-cell immunity requires: activation of the innate system, optimal presentation of major histocompatibility complex (MHC) class I-binding peptides, and provision of CD4 ϩ T-cell help. DNA vaccines have the potential to supply all of these. In an animal model of acute promyelocytic leukemia (APL), 4 we developed a promyelocytic leukemia-RAR␣ (PML/RAR␣)-targeted DNA-based vaccine 5 and show that DNA combined with all-trans retinoic acid (ATRA) has a pronounced survival advantage, concomitant with time-dependent antibody production, 5,6 and an increase in interferon-␥ (IFN-␥). 5 A similar approach confirmed these findings. 7 The role of ATRA as an immunomodulator is well documented. [8][9][10][11] Westervelt et al 12 show that ATRA responses are influenced by the presence of an intact adaptive immune response.The present study is aimed at investigating the immune responses involved in the antileukemic effect of the combined ATRA ϩ DNA therapy, particularly those mediated by CD4 ϩ and CD8 ϩ T cells. MethodsWe extended our previous study using the same protocol illustrated in supplemental Figure 1A (available on the Blood website; see the Supplemental Materials link at the top of the online article) where we combined ATRA (5 mg) and a PML-RAR␣FrC DNA construct in an APL mouse model. 5 Peripheral blood (PB) was collected approximately every 20 days from day 19 after APL engraftment to follow the mice clinically. At specific days, mice were killed to evaluate responses. Methods are detailed in the figure legends. Animal studies were undertaken according to the guidelines of the institutional animal care committee of Hôpital Saint-Louis. Results and discussion DNA vaccination combined with ATRA induces long-term survivalOur finding of ATRA ϩ DNA treatment significantly extending survival compared with ATRA alone was confirmed in additional protocols (Figure 1A-B; supplemental Figure 1B-C). We have previously reported that DNA alone elicited a modest survival advantage 5 and that FrC alone failed to give long-term survival 13 (supplemental Figure 1D).ATRA ϩ DNA-treated mice had increased white blood cell counts on day 21 after leukemia engraftment, possibly resulting from the For personal use only. on May 11, 2018. by guest www.bloodjournal.org From increases in CD4 ϩ and CD8 ϩ cells (supplemental Figure 2A). ATRAand nearly half of the ATRA ϩ DNA-treated mice had reduced platelets by day 60 (supplemental Figure 2A). Long-term survivors (LTSs) from the ATRA ϩ DNA-treated group (Ͼ 120 days) had significantly reduced bone marrow blast counts (2%-12%; supplemental Figure 2B). ATRA-alone-treated mice died by day 90.PB absolute counts of CD3 ϩ CD4 ϩ and CD3 ϩ CD8 ϩ subsets, as...

Leukocyte Homing, Fate, and Function Are Controlled by Retinoic Acid

“…An earlier study showed that liposomal RA treatment induced regression of murine acute promyelocytic leukemia in cooperation with adaptive immunity (210). In line with these findings, combination of a DNA vaccine and RA administration induced robust CD4 ϩ and CD8 ϩ T-cell immunity and enabled long-term survival in an acute promyelocytic leukemia mouse model, although ATRA alone failed to elicit pronounced T-cell immunity (56). While the studies above were not specifically designed to understand the role of RA in mediating enhanced anti-tumor T-cell immunity, they support the notion that ATRA may be important for the development of anti-tumor T cell response, thus contributing to the observed efficacy in tumor control.…”

Tracking the extramedullary PML-RARα-positive cell reservoirs in a preclinical model: Biomarker of long-term drug efficacy

“…2B). Survival of APL mice treated by the combination ATRA þ DNA is significantly (p ¼ 0.0002) superior to that of mice treated by ATRA alone [4,6] (Fig. 2D).…”

“…Therefore, monitoring PB cells by RT-qPCR analysis of PML-RARa offers a measurable evaluation of disease control during treatment pointing up the power of minimal disease quantitative assessment to differentiate therapeutic strategies in preclinical mouse models as well as in patients [7,10]. Furthermore, it is well known that in this preclinical model, suboptimal ATRA treatment leads to differentiation of APL cells and complete remission but relapses always occur and no cure is achieved with any mice alive after 120 days [3,4,6]. On the contrary in the ATRA þ DNA-treated groups, 30% of the mice are still alive with blood cell counts and spleen sizes within the normal range (data not shown) and referred to as long-term survivors (LTS) [4,6] (Fig.…”

Mutated regions of nucleophosmin 1 elicit both CD4+ and CD8+ T-cell responses in patients with acute myeloid leukemia

“…The combination of ATRA and vaccination in AML/acute promyelocytic leukemia showed an increase of specific T-cell responses in vitro. 31,32 The addition of ATRA to initial chemotherapy might contribute to the eradication of leukemic cells through down-regulation of NPM1, thus inducing apoptosis. 25 Moreover, chemotherapy followed by a combination of immunotherapy and ATRA as maintenance therapy might facilitate the elimination of minimal residual disease in AML patients.…”

“…The combination of ATRA and vaccination in AML/acute promyelocytic leukemia showed an increase of specific T-cell responses in vitro. 31,32 The addition of …”