Antitumor effect of paclitaxel is mediated by inhibition of myeloid-derived suppressor cells and chronic inflammation in the spontaneous melanoma model

A review of the ligands and related targeting strategies for active targeting of paclitaxel to tumours

It has been 30 years since the discovery of the anti-tumour property of paclitaxel (PTX), which has been successfully applied in clinic for the treatment of carcinomas of the lungs, breast and ovarian. However, PTX is poorly soluble in water and has no targeting and selectivity to tumour tissue. Recent advances in active tumour targeting of PTX delivery vehicles have addressed some of the issues related to lack of solubility in water and non-specific toxicities associated with PTX. These PTX delivery vehicles are designed for active targeting to specific cancer cells by the addition of ligands for recognition by specific receptors/antigens on cancer cells. This article will focus on various ligands and related targeting strategies serving as potential tools for active targeting of PTX to tumour tissues, illustrating their use in different tumour models. This review also highlights the need of further studies on the discovery of receptors in different cells of specific organ and ligands with binding efficiency to these specific receptors.

Chemokine receptor patterns in lymphocytes mirror metastatic spreading in melanoma

Melanoma prognosis is dictated by tumor-infiltrating lymphocytes, the migratory and functional behavior of which is guided by chemokine or cytokine gradients. Here, we retrospectively analyzed the expression patterns of 9 homing receptors (CCR/CXCR) in naive and memory CD4+ and CD8+ T lymphocytes in 57 patients with metastatic melanoma (MMel) with various sites of metastases to evaluate whether T cell CCR/CXCR expression correlates with intratumoral accumulation, metastatic progression, and/or overall survival (OS). Homing receptor expression on lymphocytes strongly correlated with MMel dissemination. Loss of CCR6 or CXCR3, but not cutaneous lymphocyte antigen (CLA), on circulating T cell subsets was associated with skin or lymph node metastases, loss of CXCR4, CXCR5, and CCR9 corresponded with lung involvement, and a rise in CCR10 or CD103 was associated with widespread dissemination. High frequencies of CD8+CCR9+ naive T cells correlated with prolonged OS, while neutralizing the CCR9/CCL25 axis in mice stimulated tumor progression. The expansion of CLA-expressing effector memory CD8+ T cells in response to a single administration of CTLA4 blockade predicted disease control at 3 months in 47 patients with MMel. Thus, specific CCR/CXCR expression patterns on circulating T lymphocytes may guide potential diagnostic and therapeutic approaches.

Combinatorial immunotherapy strategies for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common liver malignancy. The prognosis for HCC patients greatly varies according to the stage at diagnosis. Overall it is poor, with a 5-year survival rate of approximately 5-6%. Immunotherapeutic interventions represent a novel and effective therapeutic tool. However, only few immunotherapy trials for HCC have been conducted so far with contrasting results, suggesting that significant improvements are needed. Indeed, the liver is characterized by a strong intrinsic immune suppressive microenvironment which needs to be counterbalanced with immune stimulatory approaches. Therefore, the implementation of combinatorial protocols combining immune stimulatory strategies with specific immunotherapy approaches could result in a dramatic improvement of efficacy and clinical outcome in HCC patients. The present review aims at describing the state of the art in immunotherapy strategies for HCC and future perspectives.

Sulindac, a non-steroidal anti-inflammatory drug, mediates breast cancer inhibition as an immune modulator

The cooperation of adaptive immunity with pharmacologic therapy influences cancer progression. Though non-steroidal anti-inflammatory drugs (NSAIDs) have a long history of cancer prevention, it is unclear whether adaptive immune system affects the action of those drugs. In present study, we revealed a novel immunological mechanism of sulindac. Our data showed that sulindac had substantial efficacy as a single agent against 4T1 murine breast cancer and prolonged the survival of tumor-bearing mice. However, in the athymic nude mice, sulindac treatment was ineffective. Further in vivo T cell subsets depletion experiments showed that CD8+ T lymphocytes deficiency reversed the anti-tumor effect of sulindac. In addition, sulindac significantly reduced M2 macrophages recruitment, cancer-related inflammation and tumor angiogenesis. Our results advance our understanding of the mechanisms of NSAIDs, and more importantly, this will provide insight into rational drug design or antitumor immunotherapy.

Combinatorial Cancer Immunotherapies

T cell checkpoint blockade therapies are revolutionizing the treatment of patients with cancer. Highlighted by the recent success of PD-1 plus CTLA-4 blockade in patients with melanomas, synergistic immunotherapy combinations of modalities represent an important opportunity to improve responses and outcomes for patients. We review the rationale and experience with T cell checkpoint blockade in combination with targeting of other coinhibitory or costimulatory checkpoints, immunomodulatory molecules in the tumor microenvironment, and other anticancer modalities such as vaccines, chemotherapy, and radiation.

Combinatorial prospects of nano-targeted chemoimmunotherapy

Despite the significant increase in our knowledge on cancer initiation and progression, and the development of novel cancer treatments, overall patient survival rates have thus far only marginally improved. However, it can be expected that lasting tumor control will be attainable for an increasing number of cancer patients in the foreseeable future, which is likely to be achieved by combining cancer chemotherapy with anticancer immunotherapy. A plethora of new cancer chemotherapy reagents are expected to become accessible to the clinic in the coming years which can then be used for efficient tumor debulking and aid in antigen exposure to the immune system. Durable remission and the eradication of micrometastases are likely to be achieved with specialized monoclonal antibodies and therapeutic cancer vaccines that modulate the immune system to overcome immunosuppression and kill distant cancer cells. Moreover, the method of drug delivery to tumors, stromal and immune cells is expected to shift largely from conventional 'free' drug molecules to encapsulated in targeted nano-vehicles, therapeutics often referred to or considered part of "nanomedicine". Several biocompatible nano-vehicles, such as metal-nanoparticles, biodegradable-nanoparticles, liposomes or dendrimers are potential candidates for targeted drug delivery but may also serve additional purposes. A dexterous combination of nanomedicine, cancer immunotherapy and chemotherapeutic engineering are likely to become the basis for new hope in the form of targeted cancer therapies that could attack tumors early in their development. One can envision nano-vehicles that would selectively deliver effective doses of chemotherapeutic agents to cancer cells while leaving healthy cells untouched. Furthermore, given that after chemotherapeutic treatment there often remains a limited number of chemo-resistant tumor cells, which go on to drive tumor progression, nano-vehicles could also be engineered to provoke an appropriate immune response to destroy these cells. Here, we discuss the potential of the combinatorial role of cancer chemotherapy, cancer immunotherapy and the prospective of nanotechnology for the targeted delivery of chemoimmunotherapeutic agents.

Chemotherapy and immunotherapy: mapping the road ahead

Cancer immunotherapy, and in particular checkpoint blockade, is now standard clinical care for a growing number of cancers. Cytotoxic drugs have been the primary weapon against cancer for a long time and have typically been understood because of their capacity to directly kill tumour cells. It is now clear that these drugs are potential partners for checkpoint blockade and different drugs can influence the immune response to cancer through a wide variety of mechanisms. Some of these relate to immunogenic cell death, whilst others relate to changes in antigen-presentation, tumour cell targeting, or depletion of immunosuppressive cells. Here, we review some recent advances in our understanding of the immunological changes associated with chemotherapy, discuss progress in combining chemotherapy with checkpoint blockade, and comment on the difficulties encountered in translating promising preclinical data into successful treatments for cancer patients.

Immunological Effects of Conventional Chemotherapy and Targeted Anticancer Agents

The tremendous clinical success of checkpoint blockers illustrates the potential of reestablishing latent immunosurveillance for cancer therapy. Although largely neglected in the clinical practice, accumulating evidence indicates that the efficacy of conventional and targeted anticancer agents does not only involve direct cytostatic/cytotoxic effects, but also relies on the (re)activation of tumor-targeting immune responses. Chemotherapy can promote such responses by increasing the immunogenicity of malignant cells, or by inhibiting immunosuppressive circuitries that are established by developing neoplasms. These immunological "side" effects of chemotherapy are desirable, and their in-depth comprehension will facilitate the design of novel combinatorial regimens with improved clinical efficacy.

Correlation between myeloid-derived suppressor cells and S100A8/A9 in tumor and autoimmune diseases

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that constitute an important component of immune regulatory system. Two calcium-binding proteins S100A8 and S100A9 act as important mediators in acute and chronic inflammation. In recent years, many researchers have found that MDSCs and S100A8/A9 operated with one another through a positive feedback loop to promote tumor development and metastasis. However, the correlation between MDSCs and S100A8/A9 in autoimmune diseases (AIDs) remains unknown. In this review, we discussed the co-operation of MDSCs and S100A8/A9 in tumor environment, and also, the role of these two components in AIDs.

Combination cancer immunotherapy and new immunomodulatory targets

Targeting immune checkpoints such as programmed cell death protein 1 (PD1), programmed cell death 1 ligand 1 (PDL1) and cytotoxic T lymphocyte antigen 4 (CTLA4) has achieved noteworthy benefit in multiple cancers by blocking immunoinhibitory signals and enabling patients to produce an effective antitumour response. Inhibitors of CTLA4, PD1 or PDL1 administered as single agents have resulted in durable tumour regression in some patients, and combinations of PD1 and CTLA4 inhibitors may enhance antitumour benefit. Numerous additional immunomodulatory pathways as well as inhibitory factors expressed or secreted by myeloid and stromal cells in the tumour microenvironment are potential targets for synergizing with immune checkpoint blockade. Given the breadth of potential targets in the immune system, critical questions to address include which combinations should move forward in development and which patients will benefit from these treatments. This Review discusses the leading drug targets that are expressed on tumour cells and in the tumour microenvironment that allow enhancement of the antitumour immune response.

Modulation of APC Function and Anti-Tumor Immunity by Anti-Cancer Drugs

Professional antigen-presenting cells (APCs), such as dendritic cells (DCs), are central to the initiation and regulation of anti-cancer immunity. However, in the immunosuppressive environment within a tumor APCs may antagonize anti-tumor immunity by inducing regulatory T cells (Tregs) or anergy of effector T cells due to lack of efficient costimulation. Hence, in an optimal setting, anti-cancer drugs have the power to reduce tumor size and thereby may induce the release of tumor antigens and, at the same time, modulate APC function toward efficient priming of antigen-specific effector T cells. Selected cytotoxic agents may revert APC dysfunction either by directly maturing DCs or through induction of immunogenic tumor cell death. Furthermore, specific cytotoxic agents may support adaptive immunity by selectively depleting regulatory subsets, such as Tregs or myeloid-derived suppressor cells. Perspectively, this will allow developing effective combination strategies with novel immunotherapies to exert complementary pressure on tumors via direct toxicity as well as immune activation. We, here, review our current knowledge on the capacity of anti-cancer drugs to modulate APC functions to promote durable anti-cancer immune responses.

[Development of Preventive Therapy by Clarification of Mechanisms of Environmental-Factor-Mediated Diseases]

Environmental factors affecting human health are generally classified into physical, chemical and biological factors. In this review article, we focus on ultraviolet (UV) as a physical factor, heavy metals as a chemical factor and Japanese cedar pollens as a biological factor. Since we believe that progress based on both fieldwork research and experimental research is essential in hygiene study, we included the results of both the research approached. We first introduced the mechanism of development of and prevention of UV-mediated skin melanoma in our experimental research after showing our epidemiological research on UV-mediated DNA damage in humans. We then introduced our evaluation of toxicity and development of a remediation system in our experimental research on heavy metals after showing our fieldwork research for the monitoring of drinking water from wells in Asian countries. We finally introduced the results of pathogenic analysis of pollinosis in our clinical study. We would be very happy if young researchers would re-realize the importance of experimental research as well as epidemiological research in hygiene study.

Immune-mediated mechanisms influencing the efficacy of anticancer therapies

Conventional anticancer therapies, such as chemotherapy, radiotherapy, and targeted therapy, are designed to kill cancer cells. However, the efficacy of anticancer therapies is not only determined by their direct effects on cancer cells but also by off-target effects within the host immune system. Cytotoxic treatment regimens elicit several changes in immune-related parameters including the composition, phenotype, and function of immune cells. Here we discuss the impact of innate and adaptive immune cells on the success of anticancer therapy. In this context we examine the opportunities to exploit host immune responses to boost tumor clearing, and highlight the challenges facing the treatment of advanced metastatic disease.

A highly efficient tumor-infiltrating MDSC differentiation system for discovery of anti-neoplastic targets, which circumvents the need for tumor establishment in mice

Myeloid-derived suppressor cells (MDSCs) exhibit potent immunosuppressive activities in cancer. MDSCs infiltrate tumors and strongly inhibit cancer-specific cytotoxic T cells. Their mechanism of differentiation and identification of MDSC-specific therapeutic targets are major areas of interest. We have devised a highly efficient and rapid method to produce very large numbers of melanoma-infiltrating MDSCs ex vivo without inducing tumors in mice. These MDSCs were used to study their differentiation, immunosuppressive activities and were compared to non-neoplastic counterparts and conventional dendritic cells using unbiased systems biology approaches. Differentially activated/deactivated pathways caused by cell type differences and by the melanoma tumor environment were identified. MDSCs increased the expression of trafficking receptors to sites of inflammation, endocytosis, changed lipid metabolism, and up-regulated detoxification pathways such as the expression of P450 reductase. These studies uncovered more than 60 potential novel therapeutic targets. As a proof of principle, we demonstrate that P450 reductase is the target of pro-drugs such as Paclitaxel, which depletes MDSCs following chemotherapy in animal models of melanoma and in human patients. Conversely, P450 reductase protects MDSCs against the cytotoxic actions of other chemotherapy drugs such as Irinotecan, which is ineffective for the treatment of melanoma.

The importance of the tumor microenvironment in the therapeutic management of cancer

Tumor prognosis is generally defined by various tumor parameters. However, it is well known that paracrine, endocrine and cell-cell interactions between the tumor and its microenvironment contribute to its growth. The tumor microenvironment (TME) can also influence disease prognosis and is likely to be considered as an important prognostic factor. In addition, conventional therapies can influence the microenvironment and antitumor immunity. Similarly, the TME will influence the effectiveness of therapy. The purpose of this review is to demonstrate how TME is important in therapeutic management. Key interactions between TME and different cancer therapies as well as their current clinical consequences have been described. More research is needed to establish the important network between tumor cells and their environment to highlight their relationships with conventional therapies and develop global therapeutic strategies.

[Metronomic Chemotherapy--A New Path to Treat Advanced Non-small Cell Lung Cancer]

节拍化疗是近年来兴起的一种新的化疗策略。与传统化疗不同，节拍化疗通过相对低剂量的、频繁的应用细胞毒性药物，没有较长的治疗间歇，发挥抗肿瘤作用。最初认为节拍化疗直接作用于肿瘤血管内皮细胞，发挥抗血管生成作用。近年来发现节拍化疗还有调节机体免疫功能，影响肿瘤干细胞，诱导细胞休眠的作用。晚期非小细胞肺癌（non-small cell lung cancer, NSCLC）的治疗已经从彻底的清除肿瘤细胞转向改善疗效、降低毒性和提高生活质量。节拍化疗可以避免传统化疗毒性大，作用不持久的缺点，目前一些临床研究正在探索节拍化疗对晚期NSCLC的作用，并且初见疗效，有望成为晚期NSCLC一种新的治疗模式。

Histone deacetylase inhibitor-temozolomide co-treatment inhibits melanoma growth through suppression of Chemokine (C-C motif) ligand 2-driven signals

Target-specific agents used in melanoma are not curative, and chemokines are being implicated in drug-resistance to target-specific agents. Thus, the use of conventional agents in rationale combinations may result in optimization of therapy. Because histone deacetylases participate in tumor development and progression, the combination of the pan-inhibitor SAHA and temozolomide might provide a therapeutic advantage. Here, we show synergism between the two drugs in mutant BRAF cell lines, in association with decreased phosphorylation of cell survival proteins (e.g., C-Jun-N-terminal-kinase, JNK). In the spontaneous ret transgenic mouse melanoma model, combination therapy produced a significant disease onset delay and down-regulation of Chemokine (C-C motif) ligand 2 (CCL2), JNK, and of Myeloid-derived suppressor cell recruitment. Co-incubation with a CCL2-blocking-antibody enhanced in vitro cell sensitivity to temozolomide. Conversely, recombinant CCL2 activated JNK in human tumor melanoma cells. In keeping with these results, the combination of a JNK-inhibitor with temozolomide was synergistic. By showing that down-regulation of CCL2-driven signals by SAHA and temozolomide via JNK contributes to reduce melanoma growth, we provide a rationale for the therapeutic advantage of the drug combination. This combination strategy may be effective because of interference both with tumor cell and tumor microenvironment.

von Willebrand factor fibers promote cancer-associated platelet aggregation in malignant melanoma of mice and humans

Tumor-mediated procoagulatory activity leads to venous thromboembolism and supports metastasis in cancer patients. A prerequisite for metastasis formation is the interaction of cancer cells with endothelial cells (ECs) followed by their extravasation. Although it is known that activation of ECs and the release of the procoagulatory protein von Willebrand factor (VWF) is essential for malignancy, the underlying mechanisms remain poorly understood. We hypothesized that VWF fibers in tumor vessels promote tumor-associated thromboembolism and metastasis. Using in vitro settings, mouse models, and human tumor samples, we showed that melanoma cells activate ECs followed by the luminal release of VWF fibers and platelet aggregation in tumor microvessels. Analysis of human blood samples and tumor tissue revealed that a promoted VWF release combined with a local inhibition of proteolytic activity and protein expression of ADAMTS13 (a disintegrin-like and metalloproteinase with thrombospondin type I repeats 13) accounts for this procoagulatory milieu. Blocking endothelial cell activation by the low-molecular-weight heparin tinzaparin was accompanied by a lack of VWF networks and inhibited tumor progression in a transgenic mouse model. Our findings implicate a mechanism wherein tumor-derived vascular endothelial growth factor-A (VEGF-A) promotes tumor progression and angiogenesis. Thus, targeting EC activation envisions new therapeutic strategies attenuating tumor-related angiogenesis and coagulation.

Using chemo-drugs or irradiation to break immune tolerance and facilitate immunotherapy in solid cancer

The immunity is dual host-protective and tumor-promoting in cancer development and progression. Many immune suppressive cells and cytokines in microenvironment can prevent cytotoxic T lymphocytes (CTL) and natural killer cells (NK) from killing tumor cells. Chemotherapy drugs and irradiation have been reported helpful in breaking immune tolerance and creating microenvironment for adoptive cell therapy. Low-dose cyclophosphamide or gemcitabine therapy can selectively deplete T regulatory cells (Treg). Paclitaxel can alter cytokine network at the tumor site, and 5-fluorouracil shows a pronounced effect on myeloid-derived suppressor cells (MDSC) depletion. Local tumor irradiation and total body irradiation (TBI) can also affect tumor microenvironment and facilitate immunotherapy. In this review, we summarize the particular effects of these agents and methods on immunomodulation, as well as their potential values in immunotherapy. The combination with immunotherapy represents a novel therapeutic strategy.

Nano-gold corking and enzymatic uncorking of carbon nanotube cups

Because of their unique stacked, cup-shaped, hollow compartments, nitrogen-doped carbon nanotube cups (NCNCs) have promising potential as nanoscale containers. Individual NCNCs are isolated from their stacked structure through acid oxidation and subsequent probe-tip sonication. The NCNCs are then effectively corked with gold nanoparticles (GNPs) by sodium citrate reduction with chloroauric acid, forming graphitic nanocapsules with significant surface-enhanced Raman signature. Mechanistically, the growth of the GNP corks starts from the nucleation and welding of gold seeds on the open rims of NCNCs enriched with nitrogen functionalities, as confirmed by density functional theory calculations. A potent oxidizing enzyme of neutrophils, myeloperoxidase (MPO), can effectively open the corked NCNCs through GNP detachment, with subsequent complete enzymatic degradation of the graphitic shells. This controlled opening and degradation was further carried out in vitro with human neutrophils. Furthermore, the GNP-corked NCNCs were demonstrated to function as novel drug delivery carriers, capable of effective (i) delivery of paclitaxel to tumor-associated myeloid-derived suppressor cells (MDSC), (ii) MPO-regulated release, and (iii) blockade of MDSC immunosuppressive potential.

Myeloid-derived suppressor cells in malignant melanoma

Melanoma is known for its rapid progression, metastasis to distant organs and therapeutic resistance. Despite high melanoma immunogenicity, the results of immunotherapeutic clinical studies are mostly unsatisfactory. One explanation is the development of strong immunosuppression mediated by highly immunosuppressive regulatory leukocytes, in particular, myeloid-derived suppressor cells (MDSCs). These cells were found to be enriched and activated in the melanoma microenvironment, inducing a profound impairment of anti-tumor immune responses and leading to the tumor progression. Therefore, understanding the mechanisms of MDSC generation, migration to the tumor site and activation as well as their targeting is important for the development of novel strategies for effective melanoma immunotherapy. We suggest that such therapeutic approaches should involve the inhibition of MDSC-mediated immunosuppressive melanoma microenvironment combined with other immunologic treatments.

Repurposing Drugs in Oncology (ReDO)-mebendazole as an anti-cancer agent

Mebendazole, a well-known anti-helminthic drug in wide clinical use, has anti-cancer properties that have been elucidated in a broad range of pre-clinical studies across a number of different cancer types. Significantly, there are also two case reports of anti-cancer activity in humans. The data are summarised and discussed in relation to suggested mechanisms of action. Based on the evidence presented, it is proposed that mebendazole would synergise with a range of other drugs, including existing chemotherapeutics, and that further exploration of the potential of mebendazole as an anti-cancer therapeutic is warranted. A number of possible combinations with other drugs are discussed in the Appendix.

Paclitaxel: new uses for an old drug

Paclitaxel (Taxol), one of the most important anticancer drugs, has been used for therapy of different types of cancers. Mechanistically, paclitaxel arrests cell cycle and induces cell death by stabilizing microtubules and interfering with microtubule disassembly in cell division. Recently, it has been found that low-dose paclitaxel seems promising in treating non-cancer diseases, such as skin disorders, renal and hepatic fibrosis, inflammation, axon regeneration, limb salvage, and coronary artery restenosis. Future studies need to understand the mechanisms underlying these effects in order to design therapies with specificity.

Pathological mobilization and activities of dendritic cells in tumor-bearing hosts: challenges and opportunities for immunotherapy of cancer

A common characteristic of solid tumors is the pathological recruitment of immunosuppressive myeloid cells, which in certain tumors includes dendritic cells (DCs). DCs are of particular interest in the field of cancer immunotherapy because they induce potent and highly specific anti-tumor immune responses, particularly in the early phase of tumorigenesis. However, as tumors progress, these cells can be transformed into regulatory cells that contribute to an immunosuppressive microenvironment favoring tumor growth. Therefore, controlling DC phenotype has the potential to elicit effective anti-tumor responses while simultaneously weakening the tumor’s ability to protect itself from immune attack. This review focuses on the dual nature of DCs in the tumor microenvironment, the regulation of DC phenotype, and the prospect of modifying DCs in situ as a novel immunotherapeutic approach.

Immunological Mechanisms of Low and Ultra-Low Dose Cancer Chemotherapy

Traditionally, anticancer chemotherapy has been generally considered to be strongly immunosuppressive. However, increasing evidence suggests that certain chemotherapeutic agents rely on the induction of antitumor immune responses, in both experimental animal models and patients with cancer. Many of these chemotherapeutic agents exert immunogenic effects via the induction and release of immunostimulatory "danger" signals from dying cancerous cells when used in low doses. New data suggests that several common chemotherapeutic agents may also display direct stimulating effects on immune cells even when applied in ultra-low concentrations (chemoimmunomodulation). Importantly, it is becoming clear that both immune effector cells and immune regulatory cells can be targeted by various chemotherapeutic agents to produce favorable antitumor immune responses. Therefore, utilizing cancer drugs to enhance host antitumor immunity should be considered a feasible therapeutic approach; and recent characterization of the immunomodulatory mechanisms of anticancer chemotherapy using both new and traditional cytotoxic agents suggests that combinations of these approaches with "classical" immunomodulatory agents could lead to a viable new therapeutic paradigm for the treatment of cancer.

Interphase microtubules: chief casualties in the war on cancer?

Microtubule-targeting agents (MTAs) profoundly affect interphase cells, such as by disrupting axonal transport, transcription, translation, mitochondrial permeability, immune cell function, directional migration and centrosome clustering. This finding is antithetical to the conventionally held notion that MTAs act on mitosis to trigger arrest-mediated apoptotic cell death. Furthermore, the paucity of mitotic cells in patient tumors and lack of correlation of MTA efficacy with tumor proliferation rate provide strong impetus to re-examine the mechanistic basis of action of MTAs, with an eye toward interphase activities. Whereas targeted antimitotics have unequivocally failed their promise across clinical studies, MTAs constitute a mainstay of chemotherapy. This paradox necessitates the conclusion that MTAs exert mitosis-independent effects, spurring a dramatic paradigm shift in our understanding of the mode of action of MTAs.

Mechanism of action of conventional and targeted anticancer therapies: reinstating immunosurveillance

Conventional chemotherapeutics and targeted antineoplastic agents have been developed based on the simplistic notion that cancer constitutes a cell-autonomous genetic or epigenetic disease. However, it is becoming clear that many of the available anticancer drugs that have collectively saved millions of life-years mediate therapeutic effects by eliciting de novo or reactivating pre-existing tumor-specific immune responses. Here, we discuss the capacity of both conventional and targeted anticancer therapies to enhance the immunogenic properties of malignant cells and to stimulate immune effector cells, either directly or by subverting the immunosuppressive circuitries that preclude antitumor immune responses in cancer patients. Accumulating evidence indicates that the therapeutic efficacy of several antineoplastic agents relies on their capacity to influence the tumor-host interaction, tipping the balance toward the activation of an immune response specific for malignant cells. We surmise that the development of successful anticancer therapies will be improved and accelerated by the immunological characterization of candidate agents.

Potentiation of cytotoxicity of paclitaxel in combination with Cl-IB-MECA in human C32 metastatic melanoma cells: A new possible therapeutic strategy for melanoma

Metastatic melanoma monotherapies with drugs such as dacarbazine, cisplatin or paclitaxel (PXT) are associated with significant toxicity and low efficacy rates. These facts reinforce the need for development of novel agents or combinatory strategies. Cl-IB-MECA is a small molecule, orally bioavailable, well tolerated and currently under clinical trials as an anticancer agent. Our aim was to investigate a possible combinatory therapeutic strategy using PXT and Cl-IB-MECA on human C32 melanoma cells and its underlying mechanisms. Cytotoxicity was evaluated using MTT reduction, lactate dehydrogenase leakage and neutral red uptake assays, for different concentrations and combinations of both agents, at 24 and 48 h. Apoptosis was also assessed using fluorescence microscopy and through the evaluation of caspases 8, 9, and 3 activities. We demonstrated, for the first time, that combination of PXT and Cl-IB-MECA significantly increases cytotoxicity for clinically relevant concentrations. This combination seems to act synergistically in disrupting membrane integrity, but also causing lysosomal and mitochondrial dysfunction. When using the lowest PTX concentration (10 ng/mL), co-incubation with CI-IB-MECA (micromolar concentrations) potentiated overall cytotoxic effects and morphological signs of apoptosis. All combinations studied enhanced caspase 8, 9, and 3 activities, suggesting the involvement of both intrinsic and extrinsic apoptotic pathways. The possibility that cytotoxicity elicited by Cl-IB-MECA, alone or in combination with PXT, involves adenosine receptor activation was discarded and results confirmed that oxidative stress is only involved in cytotoxicity after treatment with PXT, alone. Being melanoma a very apoptosis-resistance cancer, this combination seems to hold promise as a new therapeutic strategy for melanoma.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) induces microglial nitric oxide production and subsequent rat primary cortical neuron apoptosis through p38/JNK MAPK pathway

It has been widely accepted that microglia, which are the innate immune cells in the brain, upon activation can cause neuronal damage. In the present study, we investigated the role of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in regulating microglial nitric oxide production and its role in causing neuronal damage. The study revealed that TCDD stimulates the expression of inducible nitric oxide synthase (iNOS) as well as the production of nitric oxide (NO) in a dose- and time-dependent manner. Further, a rapid activation of p38 and JNK MAPKs was found in HAPI microglia following TCDD treatment. Blockage of p38 and JNK kinases with their specific inhibitors, SB202190 and SP600125, significantly reduced TCDD-induced iNOS expression and NO production. In addition, it was demonstrated through treating rat primary cortical neurons with media conditioned with TCDD treated microglia that microglial iNOS activation mediates neuronal apoptosis. Lastly, it was also found that p38 and JNK MAPK inhibitors could attenuate the apoptosis of rat cortical neurons upon exposure to medium conditioned by TCDD-treated HAPI microglial cells. Based on these observations, we highlight that the p38/JNK MAPK pathways play an important role in TCDD-induced iNOS activation in rat HAPI microglia and in the subsequent induction of apoptosis in primary cortical neurons.