Roberto Raúl SG, Damaris IA, Ángel de Jesús JC, Leticia MF. Cry1Ac Protoxin Confers Antitumor Adjuvant Effect in a Triple-Negative Breast Cancer Mouse Model by Improving Tumor Immunity.
BREAST CANCER: BASIC AND CLINICAL RESEARCH 2022;
16:11782234211065154. [PMID:
35002244 PMCID:
PMC8738886 DOI:
10.1177/11782234211065154]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 11/17/2021] [Indexed: 12/07/2022] Open
Abstract
The Cry1Ac protoxin from Bacillus thuringiensis is a systemic
and mucosal adjuvant, able to confer protective immunity in different infection
murine models and induce both Th1 and TCD8+ cytotoxic lymphocyte responses,
which are required to induce antitumor immunity. The Cry1Ac toxin, despite
having not being characterized as an adjuvant, has also proved to be immunogenic
and able to activate macrophages. Here, we investigated the potential antitumor
adjuvant effect conferred by the Cry1Ac protoxin and Cry1Ac toxin in a triple
negative breast cancer (TNBC) murine model. First, we evaluated the ability of
Cry1Ac proteins to improve dendritic cell (DC) activation and cellular response
through intraperitoneal (i.p.) coadministration with the 4T1 cellular lysate.
Mice coadministered with the Cry1Ac protoxin showed an increase in the number
and activation of CD11c+MHCII- and CD11c+MHCII+low in the peritoneal
cavity and an increase in DC activation (CD11c+MHCII+) in the spleen. Cry1Ac
protoxin increased the proliferation of TCD4+ and TCD8+ lymphocytes in the
spleen and mesenteric lymph nodes (MLN), while the Cry1Ac toxin only increased
the proliferation of TCD4+ and TCD8+ in the MLN. Remarkably, when tested in the
in vivo TNBC mouse model, prophylactic immunizations with 4T1 lysates plus the
Cry1Ac protoxin protected mice from developing tumors. The antitumor effect
conferred by the Cry1Ac protoxin also increased specific cytotoxic T cell
responses, and prevented the typical tumor-related decrease of T cells
(TCD3+ and TCD4+) as well the increase of myeloid-derived suppressor cells
(MDSC) in spleen. Also in the tumor microenvironment of mice coadministered
twice with Cry1Ac protoxin immunological improvements were found such as
reductions in immunosupressive populations (T regulatory lymphocytes and MDSC)
along with increases in macrophages upregulating CD86. These results show a
differential antitumor adjuvant capability of Cry1Ac proteins, highlighting the
ability of Cry1Ac protoxin to enhance local and systemic tumor immunity in TNBC.
Finally, using a therapeutic approach, we evaluated the coadministration of
Cry1Ac protoxin with doxorubicin. A significant reduction in tumor volume and
lung metastasis was found, with increased intratumoral levels of tumor necrosis
factor-α and IL-6 with respect to the vehicle group, further supporting its
antitumor applicability.
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