Targeting damage-associated molecular pattern molecules (DAMPs) and DAMP receptors in melanoma

Potential of damage associated molecular patterns in synergising radiation and the immune response in oesophageal cancer

BACKGROUND

There is an intimate crosstalk between cancer formation, dissemination, treatment response and the host immune system, with inducing tumour cell death the ultimate therapeutic goal for most anti-cancer treatments. However, inducing a purposeful synergistic response between conventional therapies and the immune system remains evasive. The release of damage associated molecular patterns (DAMPs) is indicative of immunogenic cell death and propagation of established immune responses. However, there is a gap in the literature regarding the importance of DAMP expression in oesophageal adenocarcinoma (OAC) or by immune cells themselves.

AIM

To investigate the effects of conventional therapies on DAMP expression and to determine whether OAC is an immunogenic cancer.

METHODS

We investigated the levels of immunogenic cell death-associated DAMPs, calreticulin (CRT) and HMGB1 using an OAC isogenic model of radioresistance. DAMP expression was also assessed directly using ex vivo cancer patient T cells (n = 10) and within tumour biopsies (n = 9) both pre and post-treatment with clinically relevant chemo(radio)therapeutics.

RESULTS

Hypoxia in combination with nutrient deprivation significantly reduces DAMP expression by OAC cells in vitro. Significantly increased frequencies of T cell DAMP expression in OAC patients were observed following chemo(radio)therapy, which was significantly higher in tumour tissue compared with peripheral blood. Patients with high expression of HMGB1 had a significantly better tumour regression grade (TRG 1-2) compared to low expressors.

CONCLUSION

In conclusion, OAC expresses an immunogenic phenotype with two distinct subgroups of high and low DAMP expressors, which correlated with tumour regression grade and lymphatic invasion. It also identifies DAMPs namely CRT and HMGB1 as potential promising biomarkers in predicting good pathological responses to conventional chemo(radio)therapies currently used in the multimodal management of locally advanced disease.

Receptors of immune cells mediates recognition for tumors

Over the last few decades, the immune system has been steered toward eradication of cancer cells with the help of cancer immunotherapy. T cells, B cells, monocytes/macrophages, dendritic cells, T-reg cells, and natural killer (NK) cells are some of the numerous immune cell types that play a significant part in cancer cell detection and reduction of inflammation, and the antitumor response. Briefly stated, chimeric antigen receptors, adoptive transfer and immune checkpoint modulators are currently the subjects of research focus for successful immunotherapy-based treatments for a variety of cancers. This chapter discusses ongoing investigations on the mechanisms and recent developments by which receptors of immune cells especially that of lymphocytes and monocytes/macrophages regulate the detection of immune system leading to malignancies. We will also be looking into the treatment strategies based on these mechanisms.

Hypoxia-Regulated Tumor-Derived Exosomes and Tumor Progression: A Focus on Immune Evasion

Tumor cells express a high quantity of exosomes packaged with unique cargos under hypoxia, an important characteristic feature in solid tumors. These hypoxic tumor-derived exosomes are, crucially, involved in the interaction of cancer cells with their microenvironment, facilitating not only immune evasion, but increased cell growth and survival, enhanced angiogenesis, epithelial–mesenchymal transition (EMT), therapeutic resistance, autophagy, pre-metastasis, and metastasis. This paper explores the tumor microenvironment (TME) remodeling effects of hypoxic tumor-derived exosome towards facilitating the tumor progression process, particularly, the modulatory role of these factors on tumor cell immune evasion through suppression of immune cells, expression of surface recognition molecules, and secretion of antitumor soluble factor. Tumor-expressed exosomes educate immune effector cells, including macrophages, monocytes, T cells, natural killer (NK) cells, dendritic cells (DCs), γδ T lymphocytes, regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), mast cells, and B cells, within the hypoxic TME through the release of factors that regulate their recruitment, phenotype, and function. Thus, both hypoxia and tumor-derived exosomes modulate immune cells, growth factors, cytokines, receptor molecules, and other soluble factors, which, together, collaborate to form the immune-suppressive milieu of the tumor environment. Exploring the contribution of exosomal cargos, such as RNAs and proteins, as indispensable players in the cross-talk within the hypoxic tumor microenvironmental provides a potential target for antitumor immunity or subverting immune evasion and enhancing tumor therapies.

Kunitz type protease inhibitor from the canine tapeworm as a potential therapeutic for melanoma

Modulating the tumor microenvironment to promote an effective immune response is critical in managing any type of tumor. Melanoma is an aggressive skin cancer and the incidence rate is increasing worldwide. Potent protease inhibitors have recently been extensively researched as potential therapeutic agents against various cancers. EgKI-1 is a potent Kunitz type protease inhibitor identified from the canine tapeworm Echinococcus granulosus that has shown anti-cancer activities in vivo. In this study we show that EgKI-1 significantly reduced the growth of melanoma in the B16-F0 mouse model and was not toxic to normal surrounding tissue. Moreover, EgKI-1 treatment significantly reduced survivin expression levels and increased the CD8+ T cell population in draining axillary lymph nodes. Therefore, EgKI-1 potentially reduces tumor growth by inducing apoptosis and modulating the tumor microenvironment, and has potential for development as an intra-lesional treatment for melanoma.

Intracellularly Generated Immunological Gold Nanoparticles for Combinatorial Photothermal Therapy and Immunotherapy against Tumor

Gold nanoparticle (AuNP) has been widely used in cancer photothermal therapy (PTT) for ablating accessible tumor, while it is insufficient for inhibiting tumor metastasis and relapse in current stage. Here, we first developed a novel immunological AuNP through intracellular generation and exocytosis for combinatorial PTT and immunotherapy. Melanoma B16F10 cells were employed to generate AuNPs first and then shed nanoparticle trapped vesicles to extracellular environment with retained tumor antigens (AuNP@B16F10). By further introducing the nanoparticles into dendritic cells (DCs), DC-derived AuNPs (AuNP@DC_B16F10) were generated with enhanced biosafety, which can induce hyperthermia and provoke antitumor immune responses. This immunological nanoplatform demonstrated efficient inhibition or even eradication of primary tumor, tumor metastasis, as well as tumor relapse, with significantly improved overall survival of mice. With our design, the intracellularly generated AuNPs with immunological property could act as an effective treatment modality for cancer.

Radiation as an In Situ Auto-Vaccination: Current Perspectives and Challenges

Radiotherapy is generally considered to be a local treatment, but there have been reports of rare cases demonstrating abscopal effects in which antitumor effects have been observed in cancer lesions other than the irradiated site. This result is more likely to occur when immune checkpoint inhibitors are used in addition to radiotherapy. Certain radiation-induced chemokines and cytokines have immune-enhancing effects. Immune checkpoint inhibitors may strengthen these effects by stimulating antigen-presenting cells and effector cytotoxic T cells. To date, there is no consensus regarding the applicability of the abscopal effect in the clinical setting, including optimal methods for combining immune checkpoint inhibitors and irradiation. In this review, we highlight the evidence for interactions between cancer immunotherapy and radiotherapy and discuss the potential of such interactions for use in designing novel combination therapies.

Abscopal effect of radiotherapy combined with immune checkpoint inhibitors

Radiotherapy (RT) is used routinely as a standard treatment for more than 50% of patients with malignant tumors. The abscopal effect induced by local RT, which is considered as a systemic anti-tumor immune response, reflects the regression of non-irradiated metastatic lesions at a distance from the primary site of irradiation. Since the application of immunotherapy, especially with immune checkpoint inhibitors, can enhance the systemic anti-tumor response of RT, the combination of RT and immunotherapy has drawn extensive attention by oncologists and cancer researchers. Nevertheless, the exact underlying mechanism of the abscopal effect remains unclear. In general, we speculate that the immune mechanism of RT is responsible for, or at least associated with, this effect. In this review, we discuss the anti-tumor effect of RT and immune checkpoint blockade and discuss some published studies on the abscopal effect for this type of combination therapy. In addition, we also evaluate the most appropriate time window for the combination of RT and immune checkpoint blockade, as well as the optimal dose and fractionation of RT in the context of the combined treatment. Finally, the most significant purpose of this review is to identify the potential predictors of the abscopal effect to help identify the most appropriate patients who would most likely benefit from the combination treatment modality.

RIG-I inhibits the MAPK-dependent proliferation of BRAF mutant melanoma cells via MKP-1

BACKGROUND

BRAF-mutant melanoma is characterized by aggressive metastatic potential and therapeutic resistance. The innate immune receptor RIG-I has emerged as a potential target in melanoma therapies but the contributing pathways involved in anti-cancer activity are poorly characterized.

METHODS

Baseline and ATRA-induced expression of RIG-I in nine (3 wild type and 6 BRAF-mutant) melanoma cell lines was measured with Q-PCR and Western blot. Ligand-specific stimulation of RIG-I was detected by Q-PCR and ELISA. Activation of the RIG-I-coupled IRF3, NF-κB and MAPK pathways was tested with protein array and Western blot. Cell proliferation and apoptosis was monitored by flow cytometry and cell counting. Down modulation of MKP-1 expression in melanoma cells was performed by specific siRNA.

RESULTS

Short-term ATRA pre-treatment increases the expression of RIG-I in BRAF-mutant melanoma cells. Specific activation of RIG-I by 5'ppp-dsRNA leads to increased activity of the IRF3-IFNβ pathway but does not influence NF-κB signaling. RIG-I mediates the targeted dephosphorylation of several MAPKs (p38, RSK1, GSK-3α/β, HSP27) via the endogenous regulator MKP-1 resulting in decreased melanoma cell proliferation.

CONCLUSION

RIG-I has the potential to exert anticancer activity in BRAF-mutant melanoma via controlling IFNβ production and MAPK signaling. This is the first study showing that RIG-I activation results in MKP-1-mediated inhibition of cell proliferation via controlling the p38-HSP27, c-Jun and rpS6 pathways thus identifying RIG-I and MKP-1 as novel and promising therapeutical targets.

Key Role of DAMP in Inflammation, Cancer, and Tissue Repair

PURPOSE

This review aimed to take stock of the current status of research on damage-associated molecular pattern (DAMP) protein. We discuss the Janus-faced role of DAMP molecules in inflammation, cancer, and tissue repair. The high-mobility group box (HMGB)-1 and adenosine triphosphate proteins are well-known DAMP molecules and have been primarily associated with inflammation. However, as we shall see, recent data have linked these molecules to tissue repair. HMGB1 is associated with cancer-related inflammation. It activates nuclear factor kB, which is involved in cancer regulation via its receptor for advanced glycation end-products (RAGE), Toll-like receptors 2 and 4. Proinflammatory activity and tissue repair may lead to pharmacologic intervention, by blocking DAMP RAGE and Toll like receptor 2 and 4 role in inflammation and by increasing their concentration in tissue repair, respectively.

METHODS

We conducted a MEDLINE search for articles pertaining to the various issues related to DAMP, and we discuss the most relevant articles especially (ie, not only those published in journals with a higher impact factor).

FINDINGS

A cluster of remarkable articles on DAMP have appeared in the literature in recent years. Regarding inflammation, several strategies have been proposed to target HMGB1, from antibodies to recombinant box A, which interacts with RAGE, competing with the full molecule. In tissue repair, it was reported that the overexpression of HMGB1 or the administration of exogenous HMGB1 significantly increased the number of vessels and promoted recovery in skin-wound, ischemic injury.

IMPLICATIONS

Due to the bivalent nature of DAMP, it is often difficult to explain the relative role of DAMP in inflammation versus its role in tissue repair. However, this point is crucial as DAMP-related treatments move into clinical practice.

Pattern Recognition Receptors in Cancer Progression and Metastasis

The innate immune system is an integral component of the inflammatory response to pathophysiological stimuli. Toll-like receptors (TLRs) and inflammasomes are the major sensors and pattern recognition receptors (PRRs) of the innate immune system that activate stimulus (signal)-specific pro-inflammatory responses. Chronic activation of PRRs has been found to be associated with the aggressiveness of various cancers and poor prognosis. Involvement of PRRs was earlier considered to be limited to infection- and injury-driven carcinogenesis, where they are activated by pathogenic ligands. With the recognition of damage-associated molecular patterns (DAMPs) as ligands of PRRs, the role of PRRs in carcinogenesis has also been implicated in other non-pathogen-driven neoplasms. Dying (apoptotic or necrotic) cells shed a plethora of DAMPs causing persistent activation of PRRs, leading to chronic inflammation and carcinogenesis. Such chronic activation of TLRs promotes tumor cell proliferation and enhances tumor cell invasion and metastasis by regulating pro-inflammatory cytokines, metalloproteinases, and integrins. Due to the decisive role of PRRs in carcinogenesis, targeting PRRs appears to be an effective cancer-preventive strategy. This review provides a brief account on the association of PRRs with various cancers and their role in carcinogenesis.

Mechanisms of tumor-induced T cell immune suppression and therapeutics to counter those effects

The theory of tumor immune surveillance states that the host immune system has means to recognize transformed cells and kills them to prevent growth and spreading of those cells. Nevertheless, cancer cells often survive and outgrow to form a tumor mass and metastasize to other tissues or organs. During the stage of immune evasion of tumor, various changes takes place both in the tumor cells and the tumor microenvironment to divert the anti-tumor immune responses by T cells and natural killer cells. Advances in the basic science in tumor immunology have led to development of many creative strategies to overcome the immune suppression imposed during tumor progression, a few of which have been approved for the treatment of cancer patients in the clinic. In the first part of this review, mechanisms of tumor-induced T cell immune suppression resulting in immune evasion of tumors will be discussed. In the second part, emerging methods to harness the immune responses against tumors will be introduced.

Anti-inflammative effect of glycyrrhizin on rat thermal injury via inhibition of high-mobility group box 1 protein

AIM

Glycyrrhizin (Gly) has been reported as an inhibitor of extracellular HMGB1 (high-mobility group box 1 protein) cytokine's activity, and protects spinal cord, liver, heart and brain against ischemia-reperfusion-induced injury in rats. The purpose of this study was to investigate the protective effect of Gly in rat skin thermal injury model and to elucidate the underlying mechanisms.

METHODS

Twenty-four male Sprague-Dawley rats (200-250g) were randomly divided into control group, vehicle-treated and Gly-treated burn groups, each group contained eight animals. In the latter two groups, rats were subjected to 30% TBSA (Total Body Surface Area) full-thickness scald injury. In Gly-treated burn group, glycyrrhizin (60mg/kg) was administered intraperitoneally immediately after and at 24th hour burn; in vehicle-treated burn group, Ringer's solution (4ml/kg, as a vehicle) was administered intraperitoneally immediately after and at 24th hour burn. The animals were sacrificed at 48h after injury. Aortic blood samples were obtained to detect tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) with ELISA (Enzyme-Linked Immuno Sorbent Assay) kits. Lung, liver and kidney tissue samples were collected to determine the expression of HMGB1 mRNA and protein. HMGB1 mRNA level was semiquantitatively measured by Real-Time PCR using β-actin as an internal standard, and protein expression of HMGBI was determined by Western blot.

RESULTS

Severe skin scald injury caused a significant increase in plasma TNF-α and IL-1β versus the control group (P<0.001) in 48h after burns. Intraperitoneal administration of Gly (60mg/kg) significantly reduced the levels of serum TNF-α and IL-1β (P<0.01). Gly treatment reduced these biochemical indices accompanied by lower level of HMGB1 protein (P<0.05) and mRNA expression (P<0.01).

CONCLUSION

These results demonstrate that Gly possesses an anti-inflammation effect to protect the remote organs from burn-induced injury.