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CAR T Therapy of Solid Cancers: Problems and Progress

A special issue of Cancers (ISSN 2072-6694). This special issue belongs to the section "Cancer Immunology and Immunotherapy".

Deadline for manuscript submissions: 30 October 2024 | Viewed by 1970

Special Issue Editors


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Guest Editor
Centre for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, London EC1M 6BQ, UK
Interests: integrins; cancer microenvironment; tumour invasion; tumour biology; protein structure; biomarker; therapeutic targeting

E-Mail Website
Guest Editor
Centre for Tumour Biology, Barts Cancer Institute, Queen Mary University of London, London EC1M 6BQ, UK
Interests: CAR T therapy; integrins

Special Issue Information

Dear Colleagues,

CAR T cell therapy has revolutionized the treatment of hematological malignancies; however, this clinical success has yet to be seen in the treatment of solid cancers. The major issues presented by solid tumors include trafficking to and penetration into the tumor, and CAR T cell cytotoxic function within the tumor microenvironment.  

The reasons for this lack of efficacy appear to be a combination of a powerful immunosuppressive environment driven my multiple elements of the innate and adaptive immune system, in addition to the physical characteristics of the tumor microenvironment, such as desmoplasia and the net positive pressure.

To overcome these challenges, we must investigate the biology of CAR T-cells within immuno-competent models. In this Special Issue of Cancers, entitled “CAR T therapy of solid cancers: Problems and Progress”, we invite experts in the field, many of whom employ syngeneic solid tumor models in mice, to submit articles in the hope that together we can begin to resolve the current lack of clinical success regarding the application of CAR T -cell therapy in solid cancers.

Prof. Dr. John F. Marshall
Dr. Lauren Cutmore
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Cancers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • CAR T therapy
  • tumor microenvironment
  • solid tumor
  • treatment
  • immuno-competent models

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Published Papers (2 papers)

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Research

Jump to: Review

11 pages, 1435 KiB  
Article
Ectopic PU.1 Expression Provides Chimeric Antigen Receptor (CAR) T Cells with Innate Cell Capacities Including IFN-β Release
by Dennis Christoph Harrer, Matthias Eder, Markus Barden, Hong Pan, Wolfgang Herr and Hinrich Abken
Cancers 2024, 16(15), 2737; https://doi.org/10.3390/cancers16152737 - 1 Aug 2024
Viewed by 688
Abstract
Chimeric antigen receptor (CAR) T cell therapy has achieved extraordinary success in eliminating B cell malignancies; however, so far, it has shown limited efficacy in the treatment of solid tumors, which is thought to be due to insufficient CAR T cell activation. We [...] Read more.
Chimeric antigen receptor (CAR) T cell therapy has achieved extraordinary success in eliminating B cell malignancies; however, so far, it has shown limited efficacy in the treatment of solid tumors, which is thought to be due to insufficient CAR T cell activation. We hypothesized that the transcription factor PU.1, a master regulator of innate cell functionality, may augment pro-inflammatory CAR T cell activation. T cells were engineered with a CEA-specific CAR together with the constitutive expression of PU.1. CAR-redirected T cell activation was recorded for canonical functionality in vitro under conditions of prolonged repetitive antigen exposure. Ectopic PU.1 expression in CAR T cells upregulated the costimulatory receptors CD40, CD80, CD86, and CD70, which, unexpectedly, did not augment effector functions but hampered the upregulation of 4-1BB, decreased IL-2 production, reduced CAR T cell proliferation, and impaired their cytotoxic capacities. Under “stress” conditions of repetitive engagement of cognate tumor cells, CAR T cells with ectopic PU.1 showed reduced persistence, and finally failed to control the growth of cancer cells. Mechanistically, PU.1 caused CAR T cells to secrete IFN-β, a cytokine known to promote CAR T cell attrition and apoptosis. Collectively, PU.1 can polarize the functional capacities of CAR T cells towards innate cells. Full article
(This article belongs to the Special Issue CAR T Therapy of Solid Cancers: Problems and Progress)
Show Figures

Figure 1

Figure 1
<p>Ectopic expression of PU.1 upregulates costimulatory receptors on CAR T cells. (<b>A</b>) Schematic depiction of CAR and PU.1 expression constructs. (<b>B</b>) CAR expression by aCEA-28ζ-GFP CAR T cells (Ctrl) and aCEA-28ζ-PU.1 CAR T cells (PU.1) was detected by staining with a phycoerythrin (PE)-labeled goat anti-IgG antibody before (upper panels) and after (lower panels) magnetic cell separation (MACS). The anti-IgG antibody detects the common IgG1 CH2-CH3 spacer domain of the CAR. One representative donor out of six is shown. Data represent means ± SEM of six donors; <span class="html-italic">p</span> values were calculated by Student’s <span class="html-italic">t</span> test, ns: not significant. (<b>C</b>) Western blot showing PU.1 protein expression in aCEA-28ζ-GFP CAR T cells (Ctrl) and aCEA-28ζ-PU.1 CAR T cells (PU.1) five days after retroviral transduction. One representative donor out of six donors is shown. (<b>D</b>) Flow cytometric analysis of PU.1 target genes MHC-I and MHC-II, costimulatory receptors, adhesion molecules, and the myeloid marker CD33 in CD8<sup>+</sup> (upper panels) and CD4<sup>+</sup> (lower panels) CAR T cells at baseline (d0) and 48 h after stimulation with CEA+ BxPC-3 pancreatic carcinoma cells (d2). Data represent geometric means ± SEM of four donors; <span class="html-italic">p</span> values were calculated by paired <span class="html-italic">t</span> test. * indicates <span class="html-italic">p</span> ≤ 0.05, ** indicates <span class="html-italic">p</span> ≤ 0.01, *** indicates <span class="html-italic">p</span> ≤ 0.001 and ns indicates not significant.</p>
Full article ">Figure 2
<p>Ectopic expression of PU.1 impairs IL-2 secretion and proliferation of CAR T cells. (<b>A</b>) CAR-triggered CD25 upregulation in CD8<sup>+</sup> and CD4<sup>+</sup> T cells 48 h after co-incubation with CEA<sup>+</sup> BxPC-3 cells compared with CEA<sup>−</sup> 293 T cells. (<b>B</b>) CAR-triggered secretion of IFN-γ and IL-2 by CAR T cells incubated with BxPC-3 cells and 293T cells, respectively, after 48 h as determined by ELISA. (<b>C</b>) Expansion index of CD8<sup>+</sup> and CD4<sup>+</sup> CAR T cells was determined by staining with the “Cell Proliferation Dye eFluor<sup>®</sup> 450” and co-incubation with BxPC-3 cells for five days. (<b>A</b>–<b>C</b>) Data represent means ± SEM of four donors; <span class="html-italic">p</span> values were calculated by Student’s <span class="html-italic">t</span> test; * <span class="html-italic">p</span> ≤ 0.05; *** <span class="html-italic">p</span> ≤ 0.001; ns, not significant.</p>
Full article ">Figure 3
<p>Ectopic PU.1 expression diminishes cytotoxicity of CAR T cells. (<b>A</b>) CAR-triggered CD137 upregulation in CD8<sup>+</sup> and CD4<sup>+</sup> T cells 48 h after co-incubation with BxPC-3 cells and 293 T cells. (<b>B</b>) Cytotoxicity of CAR T cells after a 24-h co-culture with CEA<sup>+</sup> BxPC-3 cells (left panel) and CEA- 293T cells (right panel) was determined by co-incubation at the indicated effector to target ratios and cytotoxicity recorded by an XTT-based colorimetric assay. (<b>C</b>) Flow cytometric analysis of granzyme B and perforin levels in CD8<sup>+</sup> CAR T cells at baseline after retroviral transduction. (<b>A</b>–<b>C</b>) Data represent means ± SEM of four donors; <span class="html-italic">p</span> values were calculated by Student’s <span class="html-italic">t</span> test; * <span class="html-italic">p</span> ≤ 0.05; ** <span class="html-italic">p</span> ≤ 0.01; **** <span class="html-italic">p</span> ≤ 0.0001; ns, not significant.</p>
Full article ">Figure 4
<p>Ectopic expression of PU.1 reduces functional persistence of CAR T cells. (<b>A</b>) CAR T cells (1 × 10<sup>5</sup> CAR T cells) were stimulated twice (R1 and R2) with GFP-labeled CEA<sup>+</sup> BxPC-3 cells (1 × 10<sup>5</sup> tumor cells). At the end of each round, live CD3<sup>+</sup> CAR<sup>+</sup> T cells (left panel) and BxPC-3 cells (right panel) were counted by flow cytometry. Data represent means ± SEM of five donors; <span class="html-italic">p</span> values were calculated by Student’s <span class="html-italic">t</span> test; * <span class="html-italic">p</span> ≤ 0.05, ** <span class="html-italic">p</span> ≤ 0.01; **** <span class="html-italic">p</span> ≤ 0.0001; ns, not significant. (<b>B</b>) CD8<sup>+</sup> and CD4<sup>+</sup> CAR T cells with PU.1 expression were co-incubated with BxPC-3 cells (0.5 × 10<sup>5</sup> tumor cells) for 72 h and Annexin V staining recorded by flow cytometry. Data represent means ± SEM of four donors; <span class="html-italic">p</span> values were calculated by Student’s <span class="html-italic">t</span> test; * <span class="html-italic">p</span> ≤ 0.05. (<b>C</b>) CD8<sup>+</sup> and CD4<sup>+</sup> CAR T cells with and without PU.1 were co-incubated with BxPC-3 cells for 72 h and Ki-67 expression determined by flow cytometry. Data represent means ± SEM of three donors; <span class="html-italic">p</span> values were calculated by Student’s <span class="html-italic">t</span> test; * <span class="html-italic">p</span> ≤ 0.05; ** <span class="html-italic">p</span> ≤ 0.01. (<b>D</b>) IFNβ released into the supernatant by CAR T cells incubated with BxPC-3 cells after 48 h as determined by ELISA. Data represent means ± SEM of three donors; <span class="html-italic">p</span> values were calculated by Student’s <span class="html-italic">t</span> test; * <span class="html-italic">p</span> ≤ 0.05.</p>
Full article ">

Review

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22 pages, 1700 KiB  
Review
Strategies for Improving CAR T Cell Persistence in Solid Tumors
by Megen C. Wittling, Anna C. Cole, Brianna Brammer, Kailey G. Diatikar, Nicole C. Schmitt and Chrystal M. Paulos
Cancers 2024, 16(16), 2858; https://doi.org/10.3390/cancers16162858 - 16 Aug 2024
Viewed by 839
Abstract
CAR T cells require optimization to be effective in patients with solid tumors. There are many barriers affecting their ability to succeed. One barrier is persistence, as to achieve an optimal antitumor response, infused CAR T cells must engraft and persist. This singular [...] Read more.
CAR T cells require optimization to be effective in patients with solid tumors. There are many barriers affecting their ability to succeed. One barrier is persistence, as to achieve an optimal antitumor response, infused CAR T cells must engraft and persist. This singular variable is impacted by a multitude of factors—the CAR T cell design, lymphodepletion regimen used, expansion method to generate the T cell product, and more. Additionally, external agents can be utilized to augment CAR T cells, such as the addition of novel cytokines, pharmaceutical drugs that bolster memory formation, or other agents during either the ex vivo expansion process or after CAR T cell infusion to support them in the oppressive tumor microenvironment. This review highlights many strategies being used to optimize T cell persistence as well as future directions for improving the persistence of infused cells. Full article
(This article belongs to the Special Issue CAR T Therapy of Solid Cancers: Problems and Progress)
Show Figures

Figure 1

Figure 1
<p>Intervention strategies to enhance CAR T cell persistence. Depicted is the general timeline for CAR T cell treatment as well as points indicated at which the persistence of CAR T cells can be impacted. Made using BioRender.</p>
Full article ">Figure 2
<p>Costimulatory domain possibilities in CAR constructs. Depicted is a first-generation CAR T cell with a zoomed-in region on the costimulatory domain. Different costimulatory domains being tested in CAR T cell design are listed. Domains in bold are used in current FDA-approved CAR T cell products. Note that these domains can also be combined in tandem with another domain in a third-generation CAR T cell (not depicted). Made using BioRender.</p>
Full article ">Figure 3
<p>Effects of lymphodepletion. Depicted are several effects of lymphodepletion on adoptive cellular therapy. Made using BioRender.</p>
Full article ">Figure 4
<p>Depicted are the main strategies discussed throughout the review to improve CAR T cell persistence. Made using BioRender. TBI = total body irradiation.</p>
Full article ">
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