Bacteria as Nanoparticle Carriers for Immunotherapy in Oncology

The potential use of bacteria and their derivatives as delivery systems for nanoparticles in the treatment of cancer

Cancer is a leading cause of mortality and morbidity worldwide. Nanomaterials, unique optical, magnetic, and electrical properties at the nanoscale (1-100 nm), have been engineered to improve drug capacity, bioavailability, and specificity in cancer treatment. These advancements address toxicity and lack of selectivity in conventional therapies, enabling precise targeting of cancer cells, the tumour microenvironment, and the immune system. Among emerging approaches, bacterial treatment shows promise due to its natural ability to target cancer and its diverse therapeutic mechanisms, which nanotechnology can further enhance. Bacteria-based drug delivery systems leverage bacteria's adaptability and survival strategies within the human body. Bacterial derivatives, such as bacterial ghosts (BGs), bacterial extracellular vesicles (BEVs), and dietary toxins, are recognised as effective biological nanomaterials capable of carrying nanoparticles (NPs). These systems have attracted increasing attention for their potential in targeted NP delivery for cancer treatment. This study explores the use of various bacteria and their byproducts as NP delivery vehicles, highlighting their potential in treating different types of cancer. By combining the strengths of nanotechnology and bacterial therapy, these innovative approaches aim to revolutionise cancer treatment with improved precision and efficacy.

Converging frontiers in cancer treatment: the role of nanomaterials, mesenchymal stem cells, and microbial agents-challenges and limitations

Globally, people widely recognize cancer as one of the most lethal diseases due to its high mortality rates and lack of effective treatment options. Ongoing research into cancer therapies remains a critical area of inquiry, holding significant social relevance. Currently used treatment, such as chemotherapy, radiation, or surgery, often suffers from other problems like damaging side effects, inaccuracy, and the lack of ability to clear tumors. Conventional cancer therapies are usually imprecise and ineffective and usually develop resistance to treatments and cancer recurs. Cancer patients need fresh and innovative treatment that can reduce side effects while maximizing effectiveness. In recent decades several breakthroughs in these, and other areas of medical research, have paved the way for new avenues of fighting cancer including more focused and more effective alternatives. This study reviews exciting possibilities for mesenchymal stem cells (MSCs), nanomaterials, and microbial agents in the modern realm of cancer treatment. Nanoparticles (NPs) have demonstrated surprisingly high potential. They improve drug delivery systems (DDS) significantly, enhance imaging techniques remarkably, and target cancer cells selectively while protecting healthy tissues. MSCs play a double role in tissue repair and are a vehicle for novel cancer treatments such as gene treatments or NPs loaded with therapeutic agents. Additionally, therapies utilizing microbial agents, particularly those involving bacteria, offer an inventive approach to cancer treatment. This review investigates the potential of nanomaterials, MSCs, and microbial agents in addressing the shortcomings of conventional cancer therapies. We will also discuss the challenges and limitations of using these therapeutic approaches.

Approved natural products-derived nanomedicines for disease treatment

In recent years, there has been an increasing emphasis on exploring innovative drug delivery approaches due to the limitations of conventional therapeutic strategies, such as inadequate drug targeting, insufficient therapeutic efficacy, and significant adverse effects. Nanomedicines have emerged as a promising solution with notable advantages, including extended drug circulation, targeted delivery, and improved bioavailability, potentially enhancing the clinical treatment of various diseases. Natural products/materials-derived nanomedicines, characterized by their natural therapeutic efficacy, superior biocompatibility, and safety profile, play a crucial role in nanomedicine-based treatments. This review provides a comprehensive overview of currently approved natural products-derived nanomedicines, emphasizing the essential properties of natural products-derived drug carriers, their applications in clinical diagnosis and treatment, and the current therapeutic potential and challenges. The aim is to offer guidance for the application and further development of these innovative therapeutic approaches.

Harnessing Bacterial Agents to Modulate the Tumor Microenvironment and Enhance Cancer Immunotherapy

Cancer immunotherapy has revolutionized cancer treatment by leveraging the immune system to attack tumors. However, its effectiveness is often hindered by the immunosuppressive tumor microenvironment (TME), where a complex interplay of tumor, stromal, and immune cells undermines antitumor responses and allows tumors to evade immune detection. This review explores innovative strategies to modify the TME and enhance immunotherapy outcomes, focusing on the therapeutic potential of engineered bacteria. These bacteria exploit the unique characteristics of the TME, such as abnormal vasculature and immune suppression, to selectively accumulate in tumors. Genetically modified bacteria can deliver therapeutic agents, including immune checkpoint inhibitors and cytokines, directly to tumor sites. This review highlights how bacterial therapeutics can target critical immune cells within the TME, such as myeloid-derived suppressor cells and tumor-associated macrophages, thereby promoting antitumor immunity. The combination of bacterial therapies with immune checkpoint inhibitors or adoptive cell transfer presents a promising strategy to counteract immune suppression. Continued research in this area could position bacterial agents as a powerful new modality to reshape the TME and enhance the efficacy of cancer immunotherapy, particularly for tumors resistant to conventional treatments.

The application of bacteria-nanomaterial hybrids in antitumor therapy

Adverse effects and multidrug resistance remain significant obstacles in conventional cancer therapy. Nanomedicines, with their intrinsic properties such as nano-sized dimensions and tunable surface characteristics, have the potential to mitigate the side effects of traditional cancer treatments. While nanomaterials have been widely applied in cancer treatment, challenges such as low targeting efficiency and poor tumor penetration persist. Recent research has shown that anaerobic bacteria exhibit high selectivity for primary tumors and metastatic cancers, offering good safety and superior tumor penetration capabilities. This suggests that combining nanomaterials with bacteria could complement their respective limitations, opening vast potential applications in cancer therapy. The use of bacteria in combination with nanomaterials for anticancer treatments, including chemotherapy, radiotherapy, and photothermal/photodynamic therapy, has contributed to the rapid development of the field of bacterial oncology treatments. This review explores the mechanisms of bacterial tumor targeting and summarizes strategies for synthesizing bacterial-nanomaterial and their application in cancer therapy. The combination of bacterial-nanomaterial hybrids with modern therapeutic approaches represents a promising avenue for future cancer treatment research, with the potential to improve treatment outcomes for cancer patients.

Unveiling the Role of HGF/c-Met Signaling in Non-Small Cell Lung Cancer Tumor Microenvironment

Non-small cell lung cancer (NSCLC) is characterized by several molecular alterations that contribute to its development and progression. These alterations include the epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), human epidermal growth factor receptor 2 (HER2), and mesenchymal-epithelial transition factor (c-MET). Among these, the hepatocyte growth factor (HGF)/c-MET signaling pathway plays a crucial role in NSCLC. In spite of this, the involvement of the HGF/c-MET signaling axis in remodeling the tumor microenvironment (TME) remains relatively unexplored. This review explores the biological functions of the HGF/c-MET signaling pathway in both normal and cancerous cells, examining its multifaceted roles in the NSCLC tumor microenvironment, including tumor cell proliferation, migration and invasion, angiogenesis, and immune evasion. Furthermore, we summarize the current progress and clinical applications of MET-targeted therapies in NSCLC and discuss future research directions, such as the development of novel MET inhibitors and the potential of combination immunotherapy.

Surface-modified bacteria: synthesis, functionalization and biomedical applications

The past decade has witnessed a great leap forward in bacteria-based living agents, including imageable probes, diagnostic reagents, and therapeutics, by virtue of their unique characteristics, such as genetic manipulation, rapid proliferation, colonization capability, and disease site targeting specificity. However, successful translation of bacterial bioagents to clinical applications remains challenging, due largely to their inherent susceptibility to environmental insults, unavoidable toxic side effects, and limited accumulation at the sites of interest. Cell surface components, which play critical roles in shaping bacterial behaviors, provide an opportunity to chemically modify bacteria and introduce different exogenous functions that are naturally unachievable. With the help of surface modification, a wide range of functionalized bacteria have been prepared over the past years and exhibit great potential in various biomedical applications. In this article, we mainly review the synthesis, functionalization, and biomedical applications of surface-modified bacteria. We first introduce the approaches of chemical modification based on the bacterial surface structure and then highlight several advanced functions achieved by modifying specific components on the surface. We also summarize the advantages as well as limitations of surface chemically modified bacteria in the applications of bioimaging, diagnosis, and therapy and further discuss the current challenges and possible solutions in the future. This work will inspire innovative design thinking for the development of chemical strategies for preparing next-generation biomedical bacterial agents.

Bacteria-based immunotherapy for cancer: a systematic review of preclinical studies

Immunotherapy has been emerging as a powerful strategy for cancer management. Recently, accumulating evidence has demonstrated that bacteria-based immunotherapy including naive bacteria, bacterial components, and bacterial derivatives, can modulate immune response via various cellular and molecular pathways. The key mechanisms of bacterial antitumor immunity include inducing immune cells to kill tumor cells directly or reverse the immunosuppressive microenvironment. Currently, bacterial antigens synthesized as vaccine candidates by bioengineering technology are novel antitumor immunotherapy. Especially the combination therapy of bacterial vaccine with conventional therapies may further achieve enhanced therapeutic benefits against cancers. However, the clinical translation of bacteria-based immunotherapy is limited for biosafety concerns and non-uniform production standards. In this review, we aim to summarize immunotherapy strategies based on advanced bacterial therapeutics and discuss their potential for cancer management, we will also propose approaches for optimizing bacteria-based immunotherapy for facilitating clinical translation.

Establishment of ultrasound-responsive SonoBacteriaBot for targeted drug delivery and controlled release

Bacteria-driven biohybrid microbots have shown great potential in caⁿcer treatment. However, how precisely controlling drug release at the tumor site is still an issue. To overcome the limitation of this system, we proposed the ultrasound-responsive SonoBacteriaBot (DOX-PFP-PLGA@EcM). Doxorubicin (DOX) and perfluoro-n-pentane (PFP) were encapsulated in polylactic acid-glycolic acid (PLGA) to form ultrasound-responsive DOX-PFP-PLGA nanodroplets. Then, DOX-PFP-PLGA@EcM is created by DOX-PFP-PLGA amide-bonded to the surface of E. coli MG1655 (EcM). The DOX-PFP-PLGA@EcM was proved to have the characteristics of high tumor-targeting efficiency, controlled drug release capability, and ultrasound imaging. Based on the acoustic phase change function of nanodroplets, DOX-PFP-PLGA@EcM enhance the signal of US imaging after ultrasound irradiation. Meanwhile, the DOX loaded into DOX-PFP-PLGA@EcM can be released. After being intravenously injected, DOX-PFP-PLGA@EcM can efficiently accumulate in tumors without causing harm to critical organs. In conclusion, the SonoBacteriaBot has significant benefits in real-time monitoring and controlled drug release, which has significant potential applications for therapeutic drug delivery in clinical settings.