Nanoscale, antigen encounter-dependent, IL-12 delivery by CAR T cells plus PD-L1 blockade for cancer treatment.

BACKGROUND: Chimeric antigen receptor (CAR)-T cell therapies for the treatment of hematological malignancies experienced tremendous progress in the last decade. However, essential limitations need to be addressed to further improve efficacy and reduce toxicity to assure CAR-T cell persistence, trafficking to the tumor site, resistance to an hostile tumor microenvironment (TME), and containment of toxicity restricting production of powerful but potentially toxic bioproducts to the TME; the last could be achieved through contextual release upon tumor antigen encounter of factors capable of converting an immune suppressive TME into one conducive to immune rejection. METHODS: We created an HER2-targeting CAR-T (RB-312) using a clustered regularly interspaced short palindromic repeats (CRISPR) activation (CRISPRa) system, which induces the expression of the IL-12 heterodimer via conditional transcription of its two endogenous subunits p35 and p40. This circuit includes two lentiviral constructs. The first one (HER2-TEV) expresses an anti-human epidermal growth factor receptor 2 (HER2) CAR single chain variable fragment (scFv), with CD28 and CD3z co-stimulatory domains linked to the tobacco etch virus (TEV) protease and two single guide RNAs (sgRNA) targeting the interleukin (IL)-12A and IL12B transcription start site (TSS), respectively. The second construct (LdCV) encodes linker for activation of T cells (LAT) fused to nuclease-deactivated Streptococcus Pyogenes Cas9 (dCas9)-VP64-p65-Rta (VPR) via a TEV-cleavable sequence (TCS). Activation of the CAR brings HER2-TEV in close proximity to LdCV releasing dCas9 for nuclear localization. This conditional circuit leads to conditional and reversible induction of the IL-12/p70 heterodimer. RB-312 was compared in vitro to controls (cRB-312), lacking the IL-12 sgRNAs and conventional HER2 CAR (convCAR). RESULTS: The inducible CRISPRa system activated endogenous IL-12 expression resulting in enhanced secondary interferon (FN)-γ production, cytotoxicity, and CAR-T proliferation in vitro, prolonged in vivo persistence and greater suppression of HER2+ FaDu oropharyngeal cancer cell growth compared to the conventional CAR-T cell product. No systemic IL-12 was detected in the peripheral circulation. Moreover, the combination with programmed death ligand (PD-L1) blockade demonstrated robust synergistic effects. CONCLUSIONS: RB-312, the first clinically relevant product incorporating a CRISPRa system with non-gene editing and reversible upregulation of endogenous gene expression that promotes CAR-T cells persistence and effectiveness against HER2-expressing tumors. The autocrine effects of reversible, nanoscale IL-12 production limits the risk of off-tumor leakage and systemic toxicity.

Stromal AR inhibits prostate tumor progression by restraining secretory luminal epithelial cells.

Androgen receptor (AR) is expressed in both the prostate epithelium and the prostate stroma and plays diverse roles in prostate physiology. Although low expression of stromal AR is clinically associated with advanced cancer stage and worse outcome, whether stromal AR inhibits or promotes prostate cancer progression remains controversial. Here, we specifically delete AR in smooth muscle cells of the adult mouse prostate under two tumorigenic conditions, namely, the Hi-Myc genetic model and the T + E2 hormonal carcinogenesis model. Histology analyses show that stromal AR deletion exacerbates tumor progression phenotypes in both models. Furthermore, single-cell analyses of the tumor samples reveal that secretory luminal cells are the cell population particularly affected by stromal AR deletion, as they transition to a cellular state of potentiated PI3K-mTORC1 activities. Our results suggest that stromal AR normally inhibits prostate cancer progression by restraining secretory luminal cells and imply possible unintended negative effects of androgen deprivation therapy.

Contextual reprogramming of CAR-T cells for treatment of HER2+ cancers.

BACKGROUND: Adoptive transfer of chimeric antigen receptor (CAR)-engineered T cells combined with checkpoint inhibition may prevent T cell exhaustion and improve clinical outcomes. However, the approach is limited by cumulative costs and toxicities. METHODS: To overcome this drawback, we created a CAR-T (RB-340-1) that unites in one product the two modalities: a CRISPR interference-(CRISPRi) circuit prevents programmed cell death protein 1 (PD-1) expression upon antigen-encounter. RB-340-1 is engineered to express an anti-human epidermal growth factor receptor 2 (HER2) CAR single chain variable fragment (scFv), with CD28 and CD3ζ co-stimulatory domains linked to the tobacco etch virus (TEV) protease and a single guide RNA (sgRNA) targeting the PD-1 transcription start site (TSS). A second constructs includes linker for activation of T cells (LAT) fused to nuclease-deactivated spCas9 (dCas9)-Kruppel-associated box (KRAB) via a TEV-cleavable sequence (TCS). Upon antigen encounter, the LAT-dCas9-KRAB (LdCK) complex is cleaved by TEV allowing targeting of dCas9-KRAB to the PD-1 gene TSS. RESULTS: Here, we show that RB-340-1 consistently demonstrated higher production of homeostatic cytokines, enhanced expansion of CAR-T cells in vitro, prolonged in vivo persistence and more efficient suppression of HER2+ FaDu oropharyngeal cancer growth compared to the respective conventional CAR-T cell product. CONCLUSIONS: As the first application of CRISPRi toward a clinically relevant product, RB-340-1 with the conditional, non-gene editing and reversible suppression promotes CAR-T cells resilience to checkpoint inhibition, and their persistence and effectiveness against HER2-expressing cancer xenografts.

Improving CAR T-Cell Persistence.

Over the last decade remarkable progress has been made in enhancing the efficacy of CAR T therapies. However, the clinical benefits are still limited, especially in solid tumors. Even in hematological settings, patients that respond to CAR T therapies remain at risk of relapsing due to several factors including poor T-cell expansion and lack of long-term persistence after adoptive transfer. This issue is even more evident in solid tumors, as the tumor microenvironment negatively influences the survival, infiltration, and activity of T-cells. Limited persistence remains a significant hindrance to the development of effective CAR T therapies due to several determinants, which are encountered from the cell manufacturing step and onwards. CAR design and ex vivo manipulation, including culture conditions, may play a pivotal role. Moreover, previous chemotherapy and lymphodepleting treatments may play a relevant role. In this review, the main causes for decreased persistence of CAR T-cells in patients will be discussed, focusing on the molecular mechanisms underlying T-cell exhaustion. The approaches taken so far to overcome these limitations and to create exhaustion-resistant T-cells will be described. We will also examine the knowledge gained from several key clinical trials and highlight the molecular mechanisms determining T-cell stemness, as promoting stemness may represent an attractive approach to improve T-cell therapies.

Novel Method of Plasmid DNA Delivery to Mouse Bladder Urothelium by Electroporation.

Genetically engineered mouse models (GEMMs) are extremely valuable in revealing novel biological insights into the initiation and progression mechanisms of human diseases such as cancer. Transgenic and conditional knockout mice have been frequently used for gene overexpression or ablation in specific tissues or cell types in vivo. However, generating germline mouse models can be time-consuming and costly. Recent advancements in gene editing technologies and the feasibility of delivering DNA plasmids by viral infection have enabled rapid generation of non-germline autochthonous mouse cancer models for several organs. The bladder is an organ that has been difficult for viral vectors to access, due to the presence of a glycosaminoglycan layer covering the urothelium. Here, we describe a novel method developed in lab for efficient delivery of DNA plasmids into the mouse bladder urothelium in vivo. Through intravesical instillation of pCAG-GFP DNA plasmid and electroporation of surgically exposed bladder, we show that the DNA plasmid can be delivered specifically into the bladder urothelial cells for transient expression. Our method provides a fast and convenient way for overexpression and knockdown of genes in the mouse bladder, and can be applied to building GEMMs of bladder cancer and other urological diseases.