Checkpoint inhibitor-expressing lentiviral vaccine suppresses tumor growth in preclinical cancer models

BACKGROUND

While immunotherapy has been highly successful for the treatment of some cancers, for others, the immune response to tumor antigens is weak leading to treatment failure. The resistance of tumors to checkpoint inhibitor therapy may be caused by T cell exhaustion resulting from checkpoint activation.

METHODS

In this study, lentiviral vectors that expressed T cell epitopes of an experimentally introduced tumor antigen, ovalbumin, or the endogenous tumor antigen, Trp1 were developed. The vectors coexpressed CD40 ligand (CD40L), which served to mature the dendritic cells (DCs), and a soluble programmed cell death protein 1 (PD-1) microbody to prevent checkpoint activation. Vaccination of mice bearing B16.OVA melanomas with vector-transduced DCs induced the proliferation and activation of functional, antigen-specific, cytolytic CD8 T cells.

RESULTS

Vaccination induced the expansion of CD8 T cells that infiltrated the tumors to suppress tumor growth. Vector-encoded CD40L and PD-1 microbody increased the extent of tumor growth suppression. Adoptive transfer demonstrated that the effect was mediated by CD8 T cells. Direct injection of the vector, without the need for ex vivo transduction of DCs, was also effective.

CONCLUSIONS

This study suggests that therapeutic vaccination that induces tumor antigen-specific CD8 T cells coupled with a vector-expressed checkpoint inhibitor can be an effective means to suppress the growth of tumors that are resistant to conventional immunotherapy.

Poor clinical outcomes and immunoevasive contexture in CD161+CD8+ T cells barren human pancreatic cancer

BACKGROUND

The role of CD161 expression on CD8+ T cells in tumor immunology has been explored in a few studies, and the clinical significance of CD161+CD8+ T cells in pancreatic ductal adenocarcinoma (PDAC) remains unclear. This study seeks to clarify the prognostic value and molecular characteristics linked to CD161+CD8+ T cell infiltration in PDAC.

METHODS

This study included 186 patients with confirmed PDAC histology after radical resection. CD161+CD8+ T cell infiltration was assessed using immunofluorescence staining on tumor microarrays. Flow cytometry and single-cell RNA sequencing were used to evaluate their functional status.

RESULTS

We observed significant associations between tumor-infiltrating CD161+CD8+ T cells and clinicopathological factors, such as tumor differentiation, perineural invasion, and serum CA19-9 levels. Patients with higher tumor-infiltrating CD161+CD8+ T cell levels had longer overall survival (OS) and recurrence-free survival (RFS) than those with lower levels. Multivariable analysis confirmed tumor-infiltrating CD161+CD8+ T cell as an independent prognostic indicator for both OS and RFS. Notably, a combination of tumor-infiltrating CD161+CD8+ T cell and CA19-9 levels showed a superior power for survival prediction, and patients with low tumor-infiltrating CD161+CD8+ T cell and high CA19-9 levels had the worst survival. Furthermore, lower tumor-infiltrating CD161+CD8+ T cells were associated with a better response to adjuvant chemotherapy. Finally, we identified tumor-infiltrating CD161+CD8+ T cells as a unique subtype of responsive CD8+ T cells characterized by increased levels of cytotoxic cytokines and immune checkpoint molecules.

CONCLUSION

CD161+CD8+ T cells exhibit elevated levels of both cytotoxic and immune-checkpoint molecules, indicating as a potential and attractive target for immunotherapy. The tumor-infiltrating CD161+CD8+ T cell is a valuable and promising predictor for survival and therapeutic response to adjuvant chemotherapy in PDAC. Further research is warranted to validate its role in the risk stratification and optimization of therapeutic strategies.

Biomarkers for response to TIL therapy: a comprehensive review

Adoptive cell therapy with tumor-infiltrating lymphocytes (TIL) has demonstrated durable clinical responses in patients with metastatic melanoma, substantiated by recent positive results of the first phase III trial on TIL therapy. Being a demanding and logistically complex treatment, extensive preclinical and clinical effort is required to optimize patient selection by identifying predictive biomarkers of response. This review aims to comprehensively summarize the current evidence regarding the potential impact of tumor-related factors (such as mutational burden, neoantigen load, immune infiltration, status of oncogenic driver genes, and epigenetic modifications), patient characteristics (including disease burden and location, baseline cytokines and lactate dehydrogenase serum levels, human leucocyte antigen haplotype, or prior exposure to immune checkpoint inhibitors and other anticancer therapies), phenotypic features of the transferred T cells (mainly the total cell count, CD8:CD4 ratio, ex vivo culture time, expression of exhaustion markers, costimulatory signals, antitumor reactivity, and scope of target tumor-associated antigens), and other treatment-related factors (such as lymphodepleting chemotherapy and postinfusion administration of interleukin-2).

Expert consensus guidelines on management and best practices for tumor-infiltrating lymphocyte cell therapy

Adoptive cell therapy with autologous, ex vivo-expanded, tumor-infiltrating lymphocytes (TILs) is being investigated for treatment of solid tumors and has shown robust responses in clinical trials. Based on the encouraging efficacy, tolerable safety profile, and advancements in a central manufacturing process, lifileucel is now the first US Food and Drug Administration (FDA)-approved TIL cell therapy product. To this end, treatment management and delivery practice guidance is needed to ensure successful integration of this modality into clinical care. This review includes clinical and toxicity management guidelines pertaining to the TIL cell therapy regimen prepared by the TIL Working Group, composed of internationally recognized hematologists and oncologists with expertize in TIL cell therapy, and relates to patient care and operational aspects. Expert consensus recommendations for patient management, including patient eligibility, screening tests, and clinical and toxicity management with TIL cell therapy, including tumor tissue procurement surgery, non-myeloablative lymphodepletion, TIL infusion, and IL-2 administration, are discussed in the context of potential standard of care TIL use. These recommendations provide practical guidelines for optimal clinical management during administration of the TIL cell therapy regimen, and recognition of subsequent management of toxicities. These guidelines are focused on multidisciplinary teams of physicians, nurses, and stakeholders involved in the care of these patients.

Systemically administered low-affinity HER2 CAR T cells mediate antitumor efficacy without toxicity

BACKGROUND

The paucity of tumor-specific targets for chimeric antigen receptor (CAR) T-cell therapy of solid tumors necessitates careful preclinical evaluation of the therapeutic window for candidate antigens. Human epidermal growth factor receptor 2 (HER2) is an attractive candidate for CAR T-cell therapy in humans but has the potential for eliciting on-target off-tumor toxicity. We developed an immunocompetent tumor model of CAR T-cell therapy targeting murine HER2 (mHER2) and examined the effect of CAR affinity, T-cell dose, and lymphodepletion on safety and efficacy.

METHODS

Antibodies specific for mHER2 were generated, screened for affinity and specificity, tested for immunohistochemical staining of HER2 on normal tissues, and used for HER2-targeted CAR design. CAR candidates were evaluated for T-cell surface expression and the ability to induce T-cell proliferation, cytokine production, and cytotoxicity when transduced T cells were co-cultured with mHER2+ tumor cells in vitro. Safety and efficacy of various HER2 CARs was evaluated in two tumor models and normal non-tumor-bearing mice.

RESULTS

Mice express HER2 in the same epithelial tissues as humans, rendering these tissues vulnerable to recognition by systemically administered HER2 CAR T cells. CAR T cells designed with single-chain variable fragment (scFvs) that have high-affinity for HER2 infiltrated and caused toxicity to normal HER2-positive tissues but exhibited poor infiltration into tumors and antitumor activity. In contrast, CAR T cells designed with an scFv with low-affinity for HER2 infiltrated HER2-positive tumors and controlled tumor growth without toxicity. Toxicity mediated by high-affinity CAR T cells was independent of tumor burden and correlated with proliferation of CAR T cells post infusion.

CONCLUSIONS

Our findings illustrate the disadvantage of high-affinity CARs for targets such as HER2 that are expressed on normal tissues. The use of low-affinity HER2 CARs can safely regress tumors identifying a potential path for therapy of solid tumors that exhibit high levels of HER2.