From the Guest Editors: Role of Tumor Microenvironment in Tumor Progression and Treatment Response: A 30 Years' Journey

The effects of tumor-derived supernatants (TDS) on cancer cell progression: A review and update on carcinogenesis and immunotherapy

Tumors can produce bioactive substances called tumor-derived supernatants (TDS) that modify the immune response in the host body. This can result in immunosuppressive effects that promote the growth and spread of cancer. During tumorigenesis, the exudation of these substances can disrupt the function of immune sentinels in the host and reinforce the support for cancer cell growth. Tumor cells produce cytokines, growth factors, and proteins, which contribute to the progression of the tumor and the formation of premetastatic niches. By understanding how cancer cells influence the host immune system through the secretion of these factors, we can gain new insights into cancer diagnosis and therapy.

Engineering the Tumor Immune Microenvironment through Minimally Invasive Interventions

The tumor microenvironment (TME) is a unique landscape that poses several physical, biochemical, and immune barriers to anti-cancer therapies. The rapidly evolving field of immuno-engineering provides new opportunities to dismantle the tumor immune microenvironment by efficient tumor destruction. Systemic delivery of such treatments can often have limited local effects, leading to unwanted offsite effects such as systemic toxicity and tumor resistance. Interventional radiologists use contemporary image-guided techniques to locally deliver these therapies to modulate the immunosuppressive TME, further accelerating tumor death and invoking a better anti-tumor response. These involve local therapies such as intratumoral drug delivery, nanorobots, nanoparticles, and implantable microdevices. Physical therapies such as photodynamic therapy, electroporation, hyperthermia, hypothermia, ultrasound therapy, histotripsy, and radiotherapy are also available for local tumor destruction. While the interventional radiologist can only locally manipulate the TME, there are systemic offsite recruitments of the immune response. This is known as the abscopal effect, which leads to more significant anti-tumoral downstream effects. Local delivery of modern immunoengineering methods such as locoregional CAR-T therapy combined with immune checkpoint inhibitors efficaciously modulates the immunosuppressive TME. This review highlights the various advances and technologies available now to change the TME and revolutionize oncology from a minimally invasive viewpoint.

Stimuli-Responsive Nano-Architecture Drug-Delivery Systems to Solid Tumor Micromilieu: Past, Present, and Future Perspectives

The microenvironment characteristics of solid tumors, renowned as barriers that harshly impeded many drug-delivery approaches, were precisely studied, investigated, categorized, divided, and subdivided into a complex diverse of barriers. These categories were further studied with a particular perspective, which makes all barriers found in solid-tumor micromilieu turn into different types of stimuli, and were considered triggers that can increase and hasten drug-release targeting efficacy. This review gathers data concerning the nature of solid-tumor micromilieu. Past research focused on the treatment of such tumors, the recent efforts employed for engineering smart nanoarchitectures with the utilization of the specified stimuli categories, the possibility of combining more than one stimuli for much-greater targeting enhancement, examples of the approved nanoarchitectures that already translated clinically as well as the obstacles faced by the use of these nanostructures, and, finally, an overview of the possible future implementations of smart-chemical engineering for the design of more-efficient drug delivery and theranostic systems and for making nanosystems with a much-higher level of specificity and penetrability features.

Cytokine profiles of tumor supernatants in invasive ductal cancer and fibroadenoma of the breast and its relationship with VEGF-A expression in the tumors

Interrelations between cytokines, produced by invasive ductal carcinoma (IDC) and fibroadenoma (FA) of the breast, and angiogenic growth factor VEGF-A, expressed in IDC and FA, were investigated. The analysis of the cytokine profiles of IDC and FA was performed by cultivation of tumor biopsy specimens in vitro. Testing of the cytokine-producing reserve of the tumors for production of VEGF-A was conducted by culturing samples of IDC and FA in a medium containing polyclonal activator (a complex of phytohemagglutinin, concanavalin A, and lipopolysaccharide). Levels of cytokines and growth factors (IL-2, IL-6, IL-8, IL-10, IL-17, IL-18, IL-1β, IL-1Ra, TNF-α, IFN-γ, G-CSF, GM-CSF, VEGF-A) and MCP-1 (monocyte chemoattractant protein-1) in tumor supernatants were determined by an ELISA. Expression of VEGF-A was analyzed in tumor biopsy specimens by immunohistochemical analysis. In the IDC supernatants, the concentrations of IL-17, IL-18, and IFN-γ were higher and the concentrations of IL-10 and MCP-1 were lower in comparison with the FA supernatants. We observed negative correlations between the macrophage infiltration and VEGF-A concentration in the IDC supernatants (r = −0.508; P = 0.011) and between VEGF-A expression and the IDC vascularization degree (r = −0.423, P = 0.039). Spontaneous expression of VEGF-A in samples of IDC significantly exceeded the VEGF-A expression in FA. There was no difference between IDC and FA in VEGF-A expression after treatment with the polyclonal activators. Our results indicate that greater malignancy may have a paradoxical effect that is controlled by cytokines and characterized by weakening of tumor angiogenesis during overproduction of VEGF-A. These findings point to complex mechanisms of positive and negative regulation of tumor angiogenesis by cytokines that are produced by the tumor and by cells in its microenvironment, whose cytokine profiles may change at different stages of tumor progression.

Cytokine pattern of the breast tumor supernatant

Cytokine production was evaluated in supernatants of cultured tumor cells that were obtained by biopsy of the breast invasive ductal carcinoma (IDC) and breast fibroadenoma (FA) and grown in vitro. In the IDC supernatants, the concentrations of pro-inflammatory (pro-oncogenic) cytokines IL-17, IL-18, and IFNγ and of IL-1 receptor antagonist were significantly higher than in the FA cell supernatants. The concentrations of anti-inflammatory cytokine IL-10 and MCP-1 protein in supernatants of IDC cells were significantly lower than those determined in FA supernatants.

Pharmacokinetic strategies to improve drug penetration and entrapment within solid tumors

Despite the discovery of a large number of anticancer agents, cancer still remains among the leading causes of death since the middle of the twentieth century. Solid tumors possess a high degree of genetic instability and emergence of treatment resistance. Tumor resistance has emerged for almost all approved anticancer drugs and will most probably emerge for newly discovered anticancer agents as well. The use of pharmacokinetic approaches to increase anticancer drug concentrations within the solid tumor compartment and prolong its entrapment might diminish the possibility of resistance emergence at the molecular pharmacodynamic level and might even reverse tumor resistance. Several novel treatment modalities such as metronomic therapy, angiogenesis inhibitors, vascular disrupting agents and tumor priming have been introduced to improve solid tumor treatment outcomes. In the current review we will discuss the pharmacokinetic aspect of these treatment modalities in addition to other older treatment modalities, such as extracellular matrix dissolving agents, extracellular matrix synthesis inhibitors, chemoembolization and cellular efflux pump inhibition. Many of these strategies showed variable degrees of success/failure; however, reallocating these modalities based on their influence on the intratumoral pharmacokinetics might improve their understanding and treatment outcomes.