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Cancer remains one of the most significant and challenging medical issues of our time, characterized by high mortality rates, short survival periods, and low cure rates. The underlying mechanisms of cancer involve complex genetic mutations that lead to uncontrolled cell proliferation. These mutations can be driven by various factors, including genetic predisposition, environmental exposures to carcinogens (such as tobacco smoke and radiation), lifestyle factors (such as diet and physical inactivity), and chronic inflammation.
One of the critical challenges in cancer treatment is its high mortality rate. According to the World Health Organization (WHO), cancer was responsible for approximately 10 million deaths in 2020, making it one of the leading causes of death globally. The five-year survival rate for many cancers remains low, particularly for those diagnosed at advanced stages.
In summary, cancer's complex pathogenesis, coupled with its high mortality and morbidity, underscores its status as a major unsolved medical challenge. Ongoing research and innovative treatment approaches are essential to address this critical global health issue.
PD-1 therapy is an immunotherapy that activates the immune system to attack tumor cells by blocking the binding between the PD-1 receptor and its ligand, PD-L1, using PD-1 inhibitors. Problems with this therapy include issues of therapeutic resistance, as mutations in targets such as TIM-3 and JAK-2 may cause patients to become resistant to PD-1 therapy. In addition, individual patient differences can affect efficacy, as the expression of PD-1 and PD-L1 varies in tumor tissue. Immune-related toxicity is also a common problem and may affect the function of multiple organs, especially the heart, lungs, skin, thyroid, and digestive system. Additionally, insufficient number and function of T cells may lead to reduced therapeutic efficacy, which may be related to the depletion of T cells.
CAR-T therapy works by modifying T cells in the patient's body so that they carry tumor chimeric antigen receptors (CARs), which in turn kill tumor cells. However, there are some problems with CAR-T therapy. First, T cells have a limited ability to infiltrate tumor tissue, which is especially challenging when dealing with solid tumors. Second, CAR-T cells may become exhausted, leading to poor therapeutic outcomes. In addition, tumor cells may develop drug resistance, i.e., the antigen escape phenomenon may allow tumors to evade CAR-T cell attacks. Furthermore, CAR-T therapies may experience toxic reactions during application, such as cytokine release syndrome and neurotoxicity. The existence of these problems makes CAR-T therapy still face challenges in clinical application.
The immune system is a powerful tool for killing tumor cells, and immunotherapy has also been a landmark in the history of the human fight against cancer. Although existing immunotherapies have achieved great success, they still face difficulties in finding various tumor cell targets and low efficiency of T cell recruitment and activation. To ameliorate this problem we designed a tumor-specific gene nanomedicine that can target a wide range of tumor cells, which is expressed only in tumor cells and enhances T-cells immune responses.
In vitro stimulation of T cells with antibodies against CD3 and CD86 to mimic the dual signaling effect of T cell activation has become the most widely used method for T cell activation and expansion. Interleukin 2 (IL-2) is the most important regulatory immune factor in the body's immune network, which induces and activates a wide range of immune cells in the body to exert their effects. Based on this we associate the possibility of developing a tumor-specific genetic nanodrug using a specific promoter. This drug could specifically drive tumor cells to express anti-CD3 scFv (αCD3, CD3 activator) and anti-CD86 scFv (αCD86, CD86 activator), while mobilizing tumor cells to secrete IL-2 (a cytokine for T-cell proliferation and survival), in order to activate T-cells and enhance immunotherapy.
Two signals are required to induce T cell activation and proliferation: binding of CD3 to the TCR to form the TCR-CD3 complex to deliver the first activation signal and the second signal generated by synergistic co-stimulatory molecules, mainly CD86. We designed a tumor-specific gene nanomedicine such that it expresses only anti-CD3 scFv (αCD3, CD3 activator) and anti-CD86 scFv (αCD86, CD86 activator) on the surface of tumor cells while mobilizing the tumor cells to secrete IL-2, a cytokine for T-cell proliferation and survival, in order to activate the T-cells and to enhance the immunotherapy effect. This study provides a strategy to maximize immunotherapy efficacy independent of tumor heterogeneity.
We first chose the tyrosinase promoter (Tyr), whose specificity is reflected in the fact that it is abundantly expressed only in melanoma cells. After verifying the therapeutic effect of nanomedicines constructed with this promoter on melanoma, we replaced Tyr with the survivin promoter (Sur). Survivin is expressed in almost all human tumor cell lines, as a way to achieve specific expression within various tumor cells. We designed four plasmids, IL-2, CD3-CD86, CD3-CD86-IL-2, CD3-CD86-IL-2-GFP in this study, and conducted controlled trials to select and identify the plasmid design with the best efficacy.
· Synthesis of nanoparticles -- Cationic Lipid-Assisted Polymeric NanoparticlesNanoparticles have proved to be a very promising nucleic acid drug delivery system, through the passive, active and endogenous targeted mechanisms to adjust the properties of nanoparticles, drug delivery can be improved selectivity of human organs. The nanoparticles prepared in our study were made of PEG-PLGA and DOTAP, which are FDA approved drug auxiliary agents with certain safety profiles. PEG is not easily degraded, but it has low toxicity and good biocompatibility, and can be excreted through the kidney. DOTAP is a cationic lipid that can be hydrolyzed by lipases and phosphatases to produce fatty acids and glycerol. The resulting fatty acids can be further metabolized into the β-oxidation pathway and eventually converted to acetyl coenzyme A, which enters the citric acid cycle to generate energy. Glycerol can enter the glucose metabolism pathway. The nanoparticles have a PEG shell that protects the nucleic acid from degradation and enhances the retention at the tumor site while prolonging the blood circulation. The cationic lipid DOTAP is positively charged and capable of efficiently encapsulating negatively charged nucleic acids.
Qinqin Cheng, Zhefu Dai, Goar Smbatyan, Alan L. Epstein, Heinz-Josef Lenz, Yong Zhang, Eliciting anti-cancer immunity by genetically engineered multifunctional exosomes, Molecular Therapy, Volume 30, Issue 9, 2022, Pages 3066-3077, ISSN 1525-0016, https://doi.org/10.1016/j.ymthe.2022.06.013.
Wang, Y., Zhou, SK., Wang, Y. et al. Engineering tumor-specific gene nanomedicine to recruit and activate T cells for enhanced immunotherapy. Nat Commun 14, 1993 (2023). https://doi.org/10.1038/s41467-023-37656-w