Remodeling the Tumor Microenvironment with Emerging Nanotherapeutics

Mannan-binding lectin suppresses growth of hepatocellular carcinoma by regulating hepatic stellate cell activation via the ERK/COX-2/PGE2 pathway

Mannan binding lectin (MBL), initially known to activate the complement lectin pathway and defend against infection, was recently shown to be potentially involved in the development of several types of cancer; however, its exact role in cancers, especially its effect on tumor microenvironment remain largely unknown. Here, using a murine hepatocellular carcinoma (HCC) model, we showed that MBL was a component of liver microenvironment and MBL-deficient (MBL^-/-) mice exhibited an enhanced tumor growth compared with wild-type (WT) mice. This phenomenon was associated with elevation of myeloid derived suppressed cells (MDSCs) in tumor tissue of MBL^-/- mice. MBL deficiency also resulted in an increase of activated hepatic stellate cells (HSCs), which showed enhanced cyclooxygenase-2 (COX-2) expression and prostaglandin E2 (PGE₂) production. Pharmacological inhibition of COX-2 in vivo partially abrogated the MBL deficiency-promoted tumor growth and MDSC accumulation. Mechanistic studies revealed that MBL could interact directly with HSCs and inhibit HCC-induced HSCs activation via downregulating the extracellular signal-regulated kinase (ERK)/COX-2/PGE₂ signaling pathway. Furthermore, MBL-mediated suppression of HCC is validated by administration of MBL-expressing, liver-specific adeno-associated virus (AAV), which significantly inhibited HCC progression in MBL^-/- mice. Taken together, these data reveal that MBL may impact on tumor development by shaping the tumor microenvironment via its interaction with the local stromal cells, and also suggests its potential therapeutic use for the treatment of HCC.

Self-Assembly of a Pure Photosensitizer as a Versatile Theragnostic Nanoplatform for Imaging-Guided Antitumor Photothermal Therapy

Imaging-guided diagnosis and phototherapy has been emerging as promising theragnostic strategies for detection and treatment of cancer. 1,1'-Dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine iodide (DiR) has been widely investigated for in vivo imaging and photothermal therapy (PTT). However, the tumor-homing ability and PTT efficiency of DiR is greatly limited by its extremely low water solubility and nonspecific distribution in off-target tissues. Herein, a facile nanoassembly of pure DiR is reported as a theragnostic nanocarrier platform for imaging-guided antitumor phototherapy. Self-assembly of DiR has almost no effect on its in vitro photothermal efficacy when compared with DiR solution. Interestingly, the PEGylated nanoassemblies of DiR showed distinct advantages over DiR solution and non-PEGylated nanoassemblies in terms of systemic circulation and tumor-homing capability in vivo. As a result, PEGylated DiR nanoassemblies demonstrate potent photothermal tumor therapy in BALB/c mice bearing 4T1 xenograft tumors. Such a pure photosensitizer-based nanoassembly holds great potential as a versatile platform for efficient imaging-guided cancer therapy.

Complex interplay between tumor microenvironment and cancer therapy

Tumor microenvironment (TME) is comprised of cellular and non-cellular components that exist within and around the tumor mass. The TME is highly dynamic and its importance in different stages of cancer progression has been well recognized. A growing body of evidence suggests that TME also plays pivotal roles in cancer treatment responses. TME is significantly remodeled upon cancer therapies, and such change either enhances the responses or induces drug resistance. Given the importance of TME in tumor progression and therapy resistance, strategies that remodel TME to improve therapeutic responses are under developing. In this review, we provide an overview of the essential components in TME and the remodeling of TME in response to anti-cancer treatments. We also summarize the strategies that aim to enhance therapeutic efficacy by modulating TME.

Disulfide Bond-Driven Oxidation- and Reduction-Responsive Prodrug Nanoassemblies for Cancer Therapy

Disulfide bonds have been widely used to develop reduction-responsive drug-delivery systems (DDS) for cancer therapy. We propose that disulfide bonds might be also used as an oxidation-responsive linkage just like thioether bonds, which can be oxidized to hydrophilic sulfoxide or sulphone in the presence of oxidation stimuli. To test our hypothesis, we design three novel paclitaxel-citronellol conjugates linked via different lengths of disulfide-bond-containing carbon chain. The prodrugs can self-assemble into uniform-size nanoparticles with impressively high drug loading (>55%). As expected, the disulfide-bond-bridged prodrug nanoparticles show redox dual-responsive drug release. More interestingly, the position of disulfide bonds in the carbon chain linkage has profound impacts on the redox dual responsiveness, thereby affecting the drug release, cytotoxicity, pharmacokinetics, biodistribution, and in vivo antitumor efficacy of prodrug nanoassemblies. The redox dual-responsive mechanism is elucidated, and how the position of disulfide bonds in the carbon chain affects the redox dual responsiveness and antitumor efficiency of prodrug nanoassemblies is also clarified. Our findings give new insight into the stimuli responsiveness of disulfide bonds and provide a good foundation for the development of novel redox dual-responsive DDS for cancer therapy.

Metastasis in context: modeling the tumor microenvironment with cancer-on-a-chip approaches

Most cancer deaths are not caused by the primary tumor, but by secondary tumors formed through metastasis, a complex and poorly understood process. Cues from the tumor microenvironment, such as the biochemical composition, cellular population, extracellular matrix, and tissue (fluid) mechanics, have been indicated to play a pivotal role in the onset of metastasis. Dissecting the role of these cues from the tumor microenvironment in a controlled manner is challenging, but essential to understanding metastasis. Recently, cancer-on-a-chip models have emerged as a tool to study the tumor microenvironment and its role in metastasis. These models are based on microfluidic chips and contain small chambers for cell culture, enabling control over local gradients, fluid flow, tissue mechanics, and composition of the local environment. Here, we review the recent contributions of cancer-on-a-chip models to our understanding of the role of the tumor microenvironment in the onset of metastasis, and provide an outlook for future applications of this emerging technology.

Summary: This Review evaluates the recent contributions of cancer-on-a-chip models to our understanding of the tumor microenvironment and its role in the onset of metastasis. The authors also provide an outlook for future applications of this emerging technology.

Factors Affecting the Pharmacology of Antibody-Drug Conjugates

Major advances in therapeutic proteins, including antibody–drug conjugates (ADCs), have created revolutionary drug delivery systems in cancer over the past decade. While these immunoconjugate agents provide several advantages compared to their small-molecule counterparts, their clinical use is still in its infancy. The considerations in their development and clinical use are complex, and consist of multiple components and variables that can affect the pharmacologic characteristics. It is critical to understand the mechanisms employed by ADCs in navigating biological barriers and how these factors affect their biodistribution, delivery to tumors, efficacy, and toxicity. Thus, future studies are warranted to better understand the complex pharmacology and interaction between ADC carriers and biological systems, such as the mononuclear phagocyte system (MPS) and tumor microenvironment. This review provides an overview of factors that affect the pharmacologic profiles of ADC therapies that are currently in clinical use and development.

Light-activatable dual-source ROS-responsive prodrug nanoplatform for synergistic chemo-photodynamic therapy

In the context of prodrug nanomedicines for cancer therapy, one of the great challenges is the slow and variable release of the parent drug in tumors.