A review of PD-1/PD-L1 siRNA delivery systems in immune T cells and cancer cells

Molecular Engineering of Functional SiRNA Agents

Synthetic biology constitutes a scientific domain focused on intentional redesign of organisms to confer novel functionalities or create new products through strategic engineering of their genetic makeup. Leveraging the inherent capabilities of nature, one may address challenges across diverse sectors including medicine. Inspired by this concept, we have developed an innovative bioengineering platform, enabling high-yield and large-scale production of biological small interfering RNA (BioRNA/siRNA) agents via bacterial fermentation. Herein, we show that with the use of a new tRNA fused pre-miRNA carrier, we can produce various forms of BioRNA/siRNA agents within living host cells. We report a high-level overexpression of nine target BioRNA/siRNA molecules at 100% success rate, yielding 3-10 mg of BioRNA/siRNA per 0.25 L of bacterial culture with high purity (>98%) and low endotoxin (<5 EU/μg RNA). Furthermore, we demonstrate that three representative BioRNA/siRNAs against GFP, BCL2, and PD-L1 are biologically active and can specifically and efficiently silence their respective targets with the potential to effectively produce downstream antiproliferation effects by PD-L1-siRNA. With these promising results, we aim to advance the field of synthetic biology by offering a novel platform to bioengineer functional siRNA agents for research and drug development.

Plasmid co-expressing siRNA-PD-1 and Endostatin carried by attenuated Salmonella enhanced the anti-melanoma effect via inhibiting the expression of PD-1 and VEGF on tumor-bearing mice

Melanoma, the most perilous form of skin cancer, is known for its inherent resistance to chemotherapy. Even with advances in tumor immunotherapy, the survival of patients with advanced or recurrent melanomas remains poor. Over time, melanoma tumor cells may produce excessive angiogenic factors, necessitating the use of combinations of angiogenesis inhibitors, including broad-spectrum options, to combat melanoma. Among these inhibitors, Endostatin is one of the most broad-spectrum and least toxic angiogenesis inhibitors. We found Endostatin significantly increased the infiltration of CD8+ T cells and reduced the infiltration of M2 tumor-associated macrophages (TAMs) in the melanoma tumor microenvironment (TME). Interestingly, we also observed high expression levels of programmed death 1 (PD-1), an essential immune checkpoint molecule associated with tumor immune evasion, within the melanoma tumor microenvironment despite the use of Endostatin. To address this issue, we investigated the effects of a plasmid expressing Endostatin and PD-1 siRNA, wherein Endostatin was overexpressed while RNA interference (RNAi) targeted PD-1. These therapeutic agents were delivered using attenuated Salmonella in melanoma-bearing mice. Our results demonstrate that pEndostatin-siRNA-PD-1 therapy exhibits optimal therapeutic efficacy against melanoma. We found that pEndostatin-siRNA-PD-1 therapy promotes the infiltration of CD8+ T cells and the expression of granzyme B in melanoma tumors. Importantly, combined inhibition of angiogenesis and PD-1 significantly suppresses melanoma tumor progression compared with the inhibition of angiogenesis or PD-1 alone. Based on these findings, our study suggests that combining PD-1 inhibition with angiogenesis inhibitors holds promise as a clinical strategy for the treatment of melanoma.

Recent progress, perspectives, and issues of engineered PD-L1 regulation nano-system to better cure tumor: A review

Currently, immune checkpoint blockade (ICB) therapies that target the programmed cell death ligand-1 (PD-L1) have been used as revolutionary cancer treatments in the clinic. Apart from restoring the antitumor response of cytotoxic T cells by blocking the interaction between PD-L1 on tumor cells and programmed cell death-1 (PD-1) on T cells, PD-L1 proteins were also newly revealed to possess the capacity to accelerate DNA damage repair (DDR) and enhance tumor growth through multiple mechanisms, leading to the impaired efficacy of tumor therapies. Nevertheless, current free anti-PD-1/PD-L1 therapy still suffered from poor therapeutic outcomes in most solid tumors due to the non-selective tumor accumulation, ineludible severe cytotoxic effects, as well as the common occurrence of immune resistance. Recently, nanoparticles with efficient tumor-targeting capacity, tumor-responsive prosperity, and versatility for combination therapy were identified as new avenues for PD-L1 targeting cancer immunotherapies. In this review, we first summarized the multiple functions of PD-L1 protein in promoting tumor growth, accelerating DDR, as well as depressing immunotherapy efficacy. Following this, the effects and mechanisms of current clinically widespread tumor therapies on tumor PD-L1 expression were discussed. Then, we reviewed the recent advances in nanoparticles for anti-PD-L1 therapy via using PD-L1 antibodies, small interfering RNA (siRNA), microRNA (miRNA), clustered, regularly interspaced, short palindromic repeats (CRISPR), peptide, and small molecular drugs. At last, we discussed the challenges and perspectives to promote the clinical application of nanoparticles-based PD-L1-targeting therapy.

Remodeling the tumor immune microenvironment via siRNA therapy for precision cancer treatment

How to effectively transform the pro-oncogenic tumor microenvironments (TME) surrounding a tumor into an anti-tumoral never fails to attract people to study. Small interfering RNA (siRNA) is considered one of the most noteworthy research directions that can regulate gene expression following a process known as RNA interference (RNAi). The research about siRNA delivery targeting tumor cells and TME has been on the rise in recent years. Using siRNA drugs to silence critical proteins in TME was one of the most efficient solutions. However, the manufacture of a siRNA delivery system faces three major obstacles, i.e., appropriate cargo protection, accurately targeted delivery, and site-specific cargo release. In the following review, we summarized the pharmacological actions of siRNA drugs in remolding TME. In addition, the delivery strategies of siRNA drugs and combination therapy with siRNA drugs to remodel TME are thoroughly discussed. In the meanwhile, the most recent advancements in the development of all clinically investigated and commercialized siRNA delivery technologies are also presented. Ultimately, we propose that nanoparticle drug delivery siRNA may be the future research focus of oncogene therapy. This summary offers a thorough analysis and roadmap for general readers working in the field.