Targeting Melanoma Hypoxia with the Food-Grade Lactic Acid Bacterium Lactococcus Lactis

An Immunomodulator-Boosted Lactococcus Lactis Platform For Enhanced In Situ Tumor Vaccine

In situ vaccination is an attractive type of cancer immunotherapy, and methods of persistently dispersing immune agonists throughout the entire tumor are crucial for maximizing their therapeutic efficacy. Based on the probiotics usually used for dietary supplements, an immunomodulator-boosted Lactococcus lactis (IBL) strategy is developed to enhance the effectiveness of in situ vaccination with the immunomodulators. The intratumoral delivery of OX40 agonist and resiquimod-modified Lactococcus lactis (OR@Lac) facilitates local retention and persistent dispersion of immunomodulators, and dramatically modulates the key components of anti-tumor immune response. This novel vaccine activated dendritic cells and cytotoxic T lymphocytes in the tumor and tumor-draining lymph nodes, and ultimately significantly inhibited tumor growth and prolonged the survival rate of tumor-bearing mice. The combination of OR@Lac and ibrutinib, a myeloid-derived suppressor cell inhibitor, significantly alleviated or even completely inhibited tumor growth in tumor-bearing mice. In conclusion, IBL is a promising in situ tumor vaccine approach for clinical application and provides an inspiration for the delivery of other drugs.

Engineered live bacteria as disease detection and diagnosis tools

Sensitive and minimally invasive medical diagnostics are essential to the early detection of diseases, monitoring their progression and response to treatment. Engineered bacteria as live sensors are being developed as a new class of biosensors for sensitive, robust, noninvasive, and in situ detection of disease onset at low cost. Akin to microrobotic systems, a combination of simple genetic rules, basic logic gates, and complex synthetic bioengineering principles are used to program bacterial vectors as living machines for detecting biomarkers of diseases, some of which cannot be detected with other sensing technologies. Bacterial whole-cell biosensors (BWCBs) can have wide-ranging functions from detection only, to detection and recording, to closed-loop detection-regulated treatment. In this review article, we first summarize the unique benefits of bacteria as living sensors. We then describe the different bacteria-based diagnosis approaches and provide examples of diagnosing various diseases and disorders. We also discuss the use of bacteria as imaging vectors for disease detection and image-guided surgery. We conclude by highlighting current challenges and opportunities for further exploration toward clinical translation of these bacteria-based systems.

Niche preclinical and clinical applications of photoacoustic imaging with endogenous contrast

In the past decade, photoacoustic (PA) imaging has attracted a great deal of popularity as an emergent diagnostic technology owing to its successful demonstration in both preclinical and clinical arenas by various academic and industrial research groups. Such steady growth of PA imaging can mainly be attributed to its salient features, including being non-ionizing, cost-effective, easily deployable, and having sufficient axial, lateral, and temporal resolutions for resolving various tissue characteristics and assessing the therapeutic efficacy. In addition, PA imaging can easily be integrated with the ultrasound imaging systems, the combination of which confers the ability to co-register and cross-reference various features in the structural, functional, and molecular imaging regimes. PA imaging relies on either an endogenous source of contrast (e.g., hemoglobin) or those of an exogenous nature such as nano-sized tunable optical absorbers or dyes that may boost imaging contrast beyond that provided by the endogenous sources. In this review, we discuss the applications of PA imaging with endogenous contrast as they pertain to clinically relevant niches, including tissue characterization, cancer diagnostics/therapies (termed as theranostics), cardiovascular applications, and surgical applications. We believe that PA imaging's role as a facile indicator of several disease-relevant states will continue to expand and evolve as it is adopted by an increasing number of research laboratories and clinics worldwide.

Engineered Lactococcus lactis secreting Flt3L and OX40 ligand for in situ vaccination-based cancer immunotherapy

In situ vaccination is a promising strategy to convert the immunosuppressive tumor microenvironment into an immunostimulatory one with limited systemic exposure and side effect. However, sustained clinical benefits require long-term and multidimensional immune activation including innate and adaptive immunity. Here, we develop a probiotic food-grade Lactococcus lactis-based in situ vaccination (FOLactis) expressing a fusion protein of Fms-like tyrosine kinase 3 ligand and co-stimulator OX40 ligand. Intratumoural delivery of FOLactis contributes to local retention and sustained release of therapeutics to thoroughly modulate key components of the antitumour immune response, such as activation of natural killer cells, cytotoxic T lymphocytes, and conventional-type-1-dendritic cells in the tumors and tumor-draining lymph nodes. In addition, intratumoural administration of FOLactis induces a more robust tumor antigen-specific immune response and superior systemic antitumour efficacy in multiple poorly immune cell-infiltrated and anti-PD1-resistant tumors. Specific depletion of different immune cells reveals that CD8⁺ T and natural killer cells are crucial to the in situ vaccine-elicited tumor regression. Our results confirm that FOLactis displays an enhanced antitumour immunity and successfully converts the 'cold' tumors to 'hot' tumors.

Recent advances in bacteria-mediated cancer therapy

Cancer is among the leading cause of deaths worldwide. Although conventional therapies have been applied in the fight against the cancer, the poor oxygen, low extracellular pH, and high interstitial fluid pressure of the tumor microenvironment mean that these treatments fail to completely eradicate cancer cells. Recently, bacteria have increasingly been considered to be a promising platform for cancer therapy thanks to their many unique properties, such as specific tumor-targeting ability, high motility, immunogenicity, and their use as gene or drug carriers. Several types of bacteria have already been used for solid and metastatic tumor therapies, with promising results. With the development of synthetic biology, engineered bacteria have been endowed with the controllable expression of therapeutic proteins. Meanwhile, nanomaterials have been widely used to modify bacteria for targeted drug delivery, photothermal therapy, magnetothermal therapy, and photodynamic therapy, while promoting the antitumor efficiency of synergistic cancer therapies. This review will provide a brief introduction to the foundation of bacterial biotherapy. We begin by summarizing the recent advances in the use of many different types of bacteria in multiple targeted tumor therapies. We will then discuss the future prospects of bacteria-mediated cancer therapies.

Advances of bacteria-based delivery systems for modulating tumor microenvironment

The components and hospitable properties of tumor microenvironment (TME) are associated with tumor progression. Recently, TME modulating vectors and strategies have garnished significant attention in cancer therapy. Although a pilot work has reviewed TME regulation via nanoparticle-based delivery systems, there is no systematical review that summarizes the natural bacteria-based anti-tumor system to modulate TME. In this review, we conclude the strategies of bacterial carriers (including whole bacteria, bacterial skeleton and bacterial components) to regulate TME from the perspective of TME components and hospitable properties, and the clinical trials of bacteria-mediated cancer therapy. Current challenges and future prospects for the design of bacteria-based carriers are also proposed that provide critical insights into this natural delivery system and related translation from the bench to the clinic.

Hypoxia boosts aerobic glycolysis of carcinoma：a complex process for tumor development

Hypoxia, a common feature in malignant tumors, is mainly caused by insufficient oxygen supply. Hypoxia is closely related to cancer development, affecting cancer invasion and metastasis, energy metabolism and other pathological processes, and is not conducive to cancer treatment and prognosis. Tumor cells exacerbate metabolic abnormalities to adapt to the hypoxic microenvironment, especially to enhance aerobic glycolysis. Glycolysis leads to an acidic microenvironment in cancer tissues, enhancing cancer metastasis, deterioration and drug resistance. Therefore, hypoxia is a therapeutic target that cannot be ignored in cancer treatment. The adaptation of tumor cells to hypoxia is mainly regulated by hypoxia inducible factors (HIFs), and the stability of HIFs is improved under hypoxic conditions. HIFs can promote the glycolysis of tumors by regulating glycolytic enzymes, transporters, and participates in regulating the TCA (tricarboxylic acid) cycle. In addition, HIFs indirectly affect glycolysis through its interaction with non-coding RNAs. Therefore, targeting hypoxia and HIFs are important tumor therapies.

Emerging contrast agents for multispectral optoacoustic imaging and their biomedical applications

Optoacoustic imaging is a hybrid biomedical imaging modality which collects ultrasound waves generated via photoexciting contrast agents in tissues and produces images of high resolution and penetration depth. As a functional optoacoustic imaging technique, multispectral optoacoustic imaging, which can discriminate optoacoustic signals from different contrast agents by illuminating samples with multi-wavelength lasers and then processing the collected data with specific algorithms, assists in the identification of a specific contrast agent in target tissues and enables simultaneous molecular and physiological imaging. Moreover, multispectral optoacoustic imaging can also generate three-dimensional images for biological tissues/samples with high resolution and thus holds great potential in biomedical applications. Contrast agents play essential roles in optoacoustic imaging, and they have been widely explored and applied as probes and sensors in recent years, leading to the emergence of a variety of new contrast agents. In this review, we aim to summarize the latest advances in emerging contrast agents, especially the activatable ones which can respond to specific biological stimuli, as well as their preclinical and clinical applications. We highlight their design strategies, discuss the challenges and prospects in multispectral optoacoustic imaging, and outline the possibility of applying it in clinical translation and public health services using synthetic contrast agents.

Multidimensional role of bacteria in cancer: Mechanisms insight, diagnostic, preventive and therapeutic potential

The active role of bacteria in oncogenesis has long been a topic of debate. Although, it was speculated to be a transmissible cause of cancer as early as the 16th-century, yet the idea about the direct involvement of bacteria in cancer development has only been explored in recent decades. More recently, several studies have uncovered the mechanisms behind the carcinogenic potential of bacteria which are inflammation, immune evasion, pro-carcinogenic metabolite production, DNA damage and genomic instability. On the other side, the recent development on the understanding of tumor microenvironment and technological advancements has turned this enemy into an ally. Studies using bacteria for cancer treatment and detection have shown noticeable effects. Therapeutic abilities of bioengineered live bacteria such as high specificity, selective cytotoxicity to cancer cells, responsiveness to external signals and control after ingestion have helped to overcome the challenges faced by conventional cancer therapies and highlighted the bacterial based therapy as an ideal approach for cancer treatment. In this review, we have made an effort to compile substantial evidence to support the multidimensional role of bacteria in cancer. We have discussed the multifaceted role of bacteria in cancer by highlighting the wide impact of bacteria on different cancer types, their mechanisms of actions in inducing carcinogenicity, followed by the diagnostic and therapeutic potential of bacteria in cancers. Moreover, we have also highlighted the existing gaps in the knowledge of the association between bacteria and cancer as well as the limitation and advantage of bacteria-based therapies in cancer. A better understanding of these multidimensional roles of bacteria in cancer can open up the new doorways to develop early detection strategies, prevent cancer, and develop therapeutic tactics to cure this devastating disease.

Bacteria-Mediated Synergistic Cancer Therapy: Small Microbiome Has a Big Hope

The use of bacteria to specifically migrate to cancerous tissue and elicit an antitumor immune response provides a promising platform against cancer with significantly high potency. With dozens of clinical trials underway, some researchers hold the following views: "humans are nearing the first commercial live bacteria therapeutic." However, the facultative anaerobe Salmonella typhimurium VNP20009, which is particularly safe and shows anticancer effects in preclinical studies, had failed in a phase I clinical trial due to low tumor regression and undesired dose-dependent side effects. This is almost certain to disappoint people's inflated expectations, but it is noted that recent state-of-the-art research has turned attention to bacteria-mediated synergistic cancer therapy (BMSCT). In this review, the foundation of bacteria-mediated bio-therapy is outlined. Then, we summarize the potential benefits and challenges of bacterial bio-therapy in combination with different traditional anticancer therapeutic modalities (chemotherapy, photothermal therapy, reactive oxygen and nitrogen species therapy, immunotherapy, or prodrug-activating therapy) in the past 5 years. Next, we discuss multiple administration routes of BMSCT, highlighting potentiated antitumor responses and avoidance of potential side effects. Finally, we envision the opportunities and challenges for BMSCT development, with the purpose of inspiring medicinal scientists to widely utilize the microbiome approach in patient populations.

Skin Barriers in Dermal Drug Delivery: Which Barriers Have to Be Overcome and How Can We Measure Them?

Although, drugs are required in the various skin compartments such as viable epidermis, dermis, or hair follicles, to efficiently treat skin diseases, drug delivery into and across the skin is still challenging. An improved understanding of skin barrier physiology is mandatory to optimize drug penetration and permeation. The various barriers of the skin have to be known in detail, which means methods are needed to measure their functionality and outside-in or inside-out passage of molecules through the various barriers. In this review, we summarize our current knowledge about mechanical barriers, i.e., stratum corneum and tight junctions, in interfollicular epidermis, hair follicles and glands. Furthermore, we discuss the barrier properties of the basement membrane and dermal blood vessels. Barrier alterations found in skin of patients with atopic dermatitis are described. Finally, we critically compare the up-to-date applicability of several physical, biochemical and microscopic methods such as transepidermal water loss, impedance spectroscopy, Raman spectroscopy, immunohistochemical stainings, optical coherence microscopy and multiphoton microscopy to distinctly address the different barriers and to measure permeation through these barriers in vitro and in vivo.