Differential impairment of regulatory T cells rather than effector T cells by paclitaxel-based chemotherapy

Immune-mediated processes implicated in chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) and associated neuropathic pain are challenging complications of cancer treatment. Many of the major classes of chemotherapeutics can cause neurotoxicity and significantly modulate the immune system. There is ongoing investigation regarding whether reciprocal crosstalk between the nervous and immune systems occurs and, indeed, contributes to neuropathic pain during treatment with chemotherapeutics. An emerging concept is that neuroinflammation is one of the major mechanisms underlying CIPN. Here, we discuss recent findings, which provide insight into this complex process of neuroimmune interactions. Findings show limited infiltration of leukocytes into the nervous system of CIPN animals and varying degrees of peripheral and central glial activation depending on the chemotherapeutic drug, dose, schedule, and timing. Most evidence suggests an increase in pro-inflammatory cytokine expression and changes in immune signalling pathways. There is, however, limited evidence available from human studies and it remains unclear whether neuroinflammatory responses are the cause of neuropathy or a bystander effect of the chemotherapy treatment.

An immunostimulatory dual-functional nanocarrier that improves cancer immunochemotherapy

Immunochemotherapy combines a chemotherapeutic agent with an immune-modulating agent and represents an attractive approach to improve cancer therapy. However, the success of immunochemotherapy is hampered by the lack of a strategy to effectively co-deliver the two therapeutics to the tumours. Here we report the development of a dual-functional, immunostimulatory nanomicellar carrier that is based on a prodrug conjugate of PEG with NLG919, an indoleamine 2,3-dioxygenase (IDO) inhibitor currently used for reversing tumour immune suppression. An Fmoc group, an effective drug-interactive motif, is also introduced into the carrier to improve the drug loading capacity and formulation stability. We show that PEG_2k-Fmoc-NLG alone is effective in enhancing T-cell immune responses and exhibits significant antitumour activity in vivo. More importantly, systemic delivery of paclitaxel (PTX) using the PEG_2k-Fmoc-NLG nanocarrier leads to a significantly improved antitumour response in both breast cancer and melanoma mouse models.

The use of immunostimulatory agents to enhance the efficacy of chemotherapy is a promising strategy in cancer therapy. Here, the authors report on a micellar nanoparticle that can effectively co-deliver chemo- and immunotherapeutics, resulting in an improved in vivo antitumour response.

Immunotherapy for neuro-oncology: the critical rationale for combinatorial therapy

A successful therapeutic paradigm established historically in oncology involves combining agents with potentially complementary mechanisms of antitumor activity into rationally designed regimens. For example, cocktails of cytotoxic agents, which were carefully designed based on mechanisms of action, dose, and scheduling considerations, have led to dramatic improvements in survival including cures for childhood leukemia, Hodgkin's lymphoma, and several other complex cancers. Outcome for glioblastoma, the most common primary malignant CNS cancer, has been more modest, but nonetheless our current standard of care derives from confirmation that combination therapy surpasses single modality therapy. Immunotherapy has recently come of age for medical oncology with exciting therapeutic benefits achieved by several types of agents including vaccines, adoptive T cells, and immune checkpoint inhibitors against several types of cancers. Nonetheless, most benefits are relatively short, while others are durable but are limited to a minority of treated patients. Critical factors limiting efficacy of immunotherapeutics include insufficient immunogenicity and/or inadequate ability to overcome immunosuppressive factors exploited by tumors. The paradigm of rationally designed combinatorial regimens, originally established by cytotoxic therapy for oncology, may also prove relevant for immunotherapy. Realization of the true therapeutic potential of immunotherapy for medical oncology and neuro-oncology patients may require development of combinatorial regimens that optimize immunogenicity and target tumor adaptive immunosuppressive factors.

Strategies to modulate the immune system in breast cancer: checkpoint inhibitors and beyond

Is breast cancer (BC) immunogenic? Many data suggest that it is. Many observations demonstrated the prognostic role of tumor-infiltrating lymphocytes (TILs) in triple negative (TN) and human epidermal growth factor receptor 2 (HER-2)-positive BC. TNBCs are poorly differentiated tumors with high genetic instability and very high heterogeneity. This heterogeneity enhances the 'danger signals' and select clone variants that could be more antigenic or, in other words, that could more strongly stimulate a host immune antitumor response. The response to chemotherapy is at least partly dependent on an immunological reaction against those tumor cells that are dying during the chemotherapy. One of the mechanisms whereby chemotherapy can stimulate the immune system to recognize and destroy malignant cells is commonly known as immunogenic cell death (ICD). ICD elicits an adaptive immune response. Which are the clinical implications of all 'immunome' data produced in the last years? First, validate prognostic or predictive role of TILs. Second, validate immune genomic signatures that may be predictive and prognostic in patients with TN disease. Third, incorporate an 'immunoscore' into traditional classification of BC, thus providing an essential prognostic and potentially predictive tool in the pathology report. Fourth, implement clinical trials for BC in the metastatic setting with drugs that target immune-cell-intrinsic checkpoints. Blockade of one of these checkpoints, cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) or the programmed cell death 1 (PD-1) receptor may provide proof of concepts for the activity of an immune-modulation approach in the treatment of a BC.

INFα-2b inhibitory effects on CD4(+)CD25(+)FOXP3(+) regulatory T cells in the tumor microenvironment of C57BL/6 J mice with melanoma xenografts

Background

Regulatory T cells (Treg_s), particularly the CD4⁺CD25⁺Foxp3⁺ Treg_s, down regulate immunity and promote tumor cell growth by directly suppressing CD8⁺ and CD4⁺ T cells. Alternatively they can promote tumor growth by generating interleukin-10 (IL-10) and transforming growth factor β (TGFβ) in situ, which help tumor cells to evade the immune system.

Methods

In vivo tumor models were prepared via subcutaneous injection with a suspension of B16 melanoma cells into the left upper flank of C57BL/6 J mice. The mice were randomized into five groups: radiotherapy (RT), chemotherapy (CT), radiochemotherapy (RCT), Inteferon α (INFα) groups, and a control group. Flow cytometry was used to determine the Treg_s levels in the spleen and peripheral blood, and immunohistochemistry was performed to determine the expression levels of TGFβ and IL-10 in the tumor microenvironment.

Results

Tumor weight was significantly reduced in the CT or RCT groups (40.91 % and 41.83 %, respectively), while the reduction in tumor weight was relatively lower for the RT and IFNα groups (15.10 % and 13.15 %, respectively). The flow cytometry results showed that the ratios of CD4⁺CD25⁺Foxp3⁺ Treg_s to lymphocytes and CD4⁺ cells in the spleen and in peripheral blood were significantly decreased after treatment with IFNα (P < 0.05). Expression of TGFβ and IL-10 in the tumor microenvironment in the CT and RT groups was higher compared with the control group (P < 0.01), while the expression of TGFβ and IL-10 in the INFα group was not significantly different (P > 0.05).

Conclusions

The results show that INFα-2b inhibits cancer cell immune evasion by decreasing the levels of CD4⁺CD25⁺Foxp3⁺ Treg_s and suppressing the expression of TGFβ and IL-10 in the tumor microenvironment.

Immunotherapy for Advanced Lung Cancer

Lung cancers are immunogenic tumors that manage to evade the immune system by exploiting checkpoint pathways that render effector T cells anergic. Inhibition of these checkpoints can restore and invigorate endogenous antitumor T-cell responses. The immunotherapeutic approach of checkpoint inhibition has become an important treatment option for patients with advanced non-small cell lung cancer, playing a role that will continue to evolve over the coming years. The programmed death 1 inhibitors nivolumab and pembrolizumab have both been shown to induce durable responses and improve survival in a subset of patients with platinum-refractory metastatic non-small cell lung cancer. Nivolumab has recently earned Food and Drug Administration approval for progressive squamous cell lung cancer. Optimization and validation of a pretreatment biomarker to predict response is a key area of ongoing research. Combination therapy is now being investigated in an effort to improve response rates.

Myeloid-derived suppressor cells correlate with patient outcomes in hepatic arterial infusion chemotherapy for hepatocellular carcinoma

Hepatic arterial infusion chemotherapy (HAIC) has been employed as an alternative therapy to sorafenib for the patients with advanced hepatocellular carcinoma (HCC). In this study, we performed a comparative analysis of various immune cell responses including tumor-associated antigen (TAA)-specific T cells, regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) in advanced HCC patients treated with HAIC. Thirty-six HCC patients were examined in the study. Interferon gamma enzyme-linked immunospot assays were performed to examine the frequency of TAA-specific T cells. The frequencies of Tregs and MDSCs were examined by multicolor fluorescence-activated cell sorting analysis. The treatment with HAIC using interferon (IFN)/5-fluorouracil (FU) or IFN/FU + cisplatin modulated the frequencies of various immune cells. In 22.2 % of patients, the frequency of TAA-specific T cells increased after HAIC. Although the frequency of Tregs decreased after HAIC, it was not associated with the prognosis of patients. An analysis of prognostic factors for overall survival identified diameter of the tumor (<3.0 cm), absence of major portal vein invasion, absence of distant metastasis, Union Internationale Contre Le Cancer tumor lymph node metastasis stage (I or II), neutrophil lymphocytic ratio (<2.1) and the frequency of MDSCs (<30.5 %) as factors that prolonged overall survival time after HAIC. Even in the group adjusted with progressive levels of tumors, patients with a low frequency of MDSCs had a significantly longer overall survival time. In conclusion, the frequency of MDSCs before the treatment is a prognostic factor in HAIC against HCC.

Current status of immunotherapy

The successful use of immune checkpoint inhibitors has been big breakthrough in the development of cancer immunotherapy. Anti-CTLA-4 monoclonal antibody, ipilimumab, is the first-approved immune checkpoint inhibitor and has shown durable objective responses for advanced melanoma beyond the effect of dacarbazine. Anti-PD-1 monoclonal antibodies, nivolumab and pembrolizumab, are other immune checkpoint inhibitors that have demonstrated more effective results than conventional drugs in clinical trials for a variety of advanced solid tumors including melanoma, non-small cell lung carcinoma and renal carcinoma. These studies have indicated that the enhancement of anti-cancer immunity by controlling the immune suppressive environment in cancer tissues is an important issue for the development of cancer immune-therapy. Accordingly, in recent years, the enthusiasm for research of cancer immunology has shifted to studies regarding the formation of the immune suppressive environment, immune suppression mechanisms in cancer tissues and the molecules and cells involved in these pathways. Novel findings from these studies might lead to the development of cancer immunotherapy based on control of the immune suppressive environment.

Cancer immunotherapy via combining oncolytic virotherapy with chemotherapy: recent advances

Oncolytic viruses are multifunctional anticancer agents with huge clinical potential, and have recently passed the randomized Phase III clinical trial hurdle. Both wild-type and engineered viruses have been selected for targeting of specific cancers, to elicit cytotoxicity, and also to generate antitumor immunity. Single-agent oncolytic virotherapy treatments have resulted in modest effects in the clinic. There is increasing interest in their combination with cytotoxic agents, radiotherapy and immune-checkpoint inhibitors. Similarly to oncolytic viruses, the benefits of chemotherapeutic agents may be that they induce systemic antitumor immunity through the induction of immunogenic cell death of cancer cells. Combining these two treatment modalities has to date resulted in significant potential in vitro and in vivo synergies through various mechanisms without any apparent additional toxicities. Chemotherapy has been and will continue to be integral to the management of advanced cancers. This review therefore focuses on the potential for a number of common cytotoxic agents to be combined with clinically relevant oncolytic viruses. In many cases, this combined approach has already advanced to the clinical trial arena.

Oncolytic Immunotherapy for Treatment of Cancer

Immunotherapy entails the treatment of disease by modulation of the immune system. As detailed in the previous chapters, the different modes of achieving immune modulation are many, including the use of small/large molecules, cellular therapy, and radiation. Oncolytic viruses that can specifically attack, replicate within, and destroy tumors represent one of the most promising classes of agents for cancer immunotherapy (recently termed as oncolytic immunotherapy). The notion of oncolytic immunotherapy is considered as the way in which virus-induced tumor cell death (known as immunogenic cancer cell death (ICD)) allows the immune system to recognize tumor cells and provide long-lasting antitumor immunity. Both immune responses toward the virus and ICD together contribute toward successful antitumor efficacy. What is now becoming increasingly clear is that monotherapies, through any of the modalities detailed in this book, are neither sufficient in eradicating tumors nor in providing long-lasting antitumor immune responses and that combination therapies may deliver enhanced efficacy. After the rise of the genetic engineering era, it has been possible to engineer viruses to harbor combination-like characteristics to enhance their potency in cancer immunotherapy. This chapter provides a historical background on oncolytic virotherapy and its future application in cancer immunotherapy, especially as a combination therapy with other treatment modalities.

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.

Cytotoxic effects of chemotherapy on cancer and immune cells: how can it be modulated to generate novel therapeutic strategies?

The first objective to use chemotherapy is to kill cancer cells. However, it is common knowledge that these drugs can also damage healthy host cells, especially immune cells, and thus impair the endogenous antitumor response. Here, we focus on the cytotoxic effects of chemotherapy on tumor cells and immune cells. It is not enough to simply kill cancer cells, and causing immunogenic cell death will impair the adaptive immune system's ability to fight the remaining cancer cells. On the other hand, the killing of immune cells can also enhance tumor growth. A study of the repercussions of the cytotoxic effects of chemotherapy is of great importance to evaluate the antitumor response. Strategies can be proposed to promote the 'good way' for cancer cells to die and to avoid the adverse side effects of chemotherapy on immune cells in order to strengthen the role of the immune system in the antitumor response.

Phase I trial of multidrug resistance-associated protein 3-derived peptide in patients with hepatocellular carcinoma

Multidrug resistance-associated protein 3 (MRP3) is a carrier-type transport protein belonging to the ABC transporters. In this study, we investigated the safety and immunogenicity of a MRP3-derived peptide (MRP3765) as a vaccine and characterized the MRP3-specific T cell responses induced. Twelve hepatocellular carcinoma (HCC) patients treated with hepatic arterial infusion chemotherapy (HAIC) were enrolled. The MRP3-derived peptide was emulsified in incomplete Freund's adjuvant and administered via subcutaneous immunization three times weekly. No serious adverse drug reactions to the peptide vaccine were observed, and the vaccination was well tolerated. The vaccination induced MRP3-specific immunity in 72.7% of the patients. In a phenotypic analysis, the largest post-vaccinated increase in MRP3-specific T cells was due to an increase in cells with the effector memory phenotype. Among the 12 patients, one patient showed a partial response, nine showed a stable disease, and two showed a progressive disease. The median overall survival time was 14.0 months. In conclusion, the safety, effects of immune boosting, and possible prolongation of overall survival by the MRP3-derived peptide demonstrate the potential of the peptide to provide clinical benefit in HCC patients.

Relevance of tumor-infiltrating lymphocytes in breast cancer

While breast cancer has not been considered a cancer amenable to immunotherapeutic approaches, recent studies have demonstrated evidence of significant immune cell infiltration via tumor-infiltrating lymphocytes in a subset of patient tumors. In this review we present the current evidence highlighting the clinical relevance and utility of tumor-infiltrating lymphocytes in breast cancer. Retrospective and prospective studies have shown that the presence of tumor-infiltrating lymphocytes is a prognostic marker for higher responses to neoadjuvant chemotherapy and better survival, particularly in triple negative and HER2-positive early breast cancer. Further work is required to determine the immune subsets important in this response and to discover ways of encouraging immune infiltrate in tumor-infiltrating lymphocytes-negative patients.

Paclitaxel and Its Evolving Role in the Management of Ovarian Cancer

Paclitaxel, a class of taxane with microtubule stabilising ability, has remained with platinum based therapy, the standard care for primary ovarian cancer management. A deeper understanding of the immunological basis and other potential mechanisms of action together with new dosing schedules and/or routes of administration may potentiate its clinical benefit. Newer forms of taxanes, with better safety profiles and higher intratumoural cytotoxicity, have yet to demonstrate clinical superiority over the parent compound.

Paclitaxel and Its Evolving Role in the Management of Ovarian Cancer

Paclitaxel, a class of taxane with microtubule stabilising ability, has remained with platinum based therapy, the standard care for primary ovarian cancer management. A deeper understanding of the immunological basis and other potential mechanisms of action together with new dosing schedules and/or routes of administration may potentiate its clinical benefit. Newer forms of taxanes, with better safety profiles and higher intratumoural cytotoxicity, have yet to demonstrate clinical superiority over the parent compound.

Paclitaxel and Its Evolving Role in the Management of Ovarian Cancer

Paclitaxel, a class of taxane with microtubule stabilising ability, has remained with platinum based therapy, the standard care for primary ovarian cancer management. A deeper understanding of the immunological basis and other potential mechanisms of action together with new dosing schedules and/or routes of administration may potentiate its clinical benefit. Newer forms of taxanes, with better safety profiles and higher intratumoural cytotoxicity, have yet to demonstrate clinical superiority over the parent compound.

Enhancing the efficacy of adoptive cellular therapy by targeting tumor-induced immunosuppression

Strategies aimed at stimulating the immune system against cancer have signaled a new era for designing new effective therapies for patients. Recent breakthroughs in adoptive cellular therapy and in using checkpoint inhibitors for some patients have renewed much enthusiasm in this field. However, it has become apparent that tumors can use a multitude of inhibitory networks to effectively reduce antitumor immunity. This review discusses our current knowledge of these immune suppressive mechanisms used by tumors and describes potential new strategies that may counteract this problem resulting in significantly increasing therapeutic outcomes of adoptive immunotherapy in a higher proportion of patients.

Combining immunotherapy and anticancer agents: the right path to achieve cancer cure?

Recent clinical trials revealed the impressive efficacy of immunological checkpoint blockade in different types of metastatic cancers. Such data underscore that immunotherapy is one of the most promising strategies for cancer treatment. In addition, preclinical studies provide evidence that some cytotoxic drugs have the ability to stimulate the immune system, resulting in anti-tumor immune responses that contribute to clinical efficacy of these agents. These observations raise the hypothesis that the next step for cancer treatment is the combination of cytotoxic agents and immunotherapies. The present review aims to summarize the immune-mediated effects of chemotherapeutic agents and their clinical relevance, the biological and clinical features of immune checkpoint blockers and finally, the preclinical and clinical rationale for novel therapeutic strategies combining anticancer agents and immune checkpoint blockers.

Nivolumab in NSCLC: latest evidence and clinical potential

New insight on the interaction between the immune system and tumor has identified the programmed death-1/programmed death-1 ligand pathway to be a key player in evading host immune response. The immune checkpoint modulator, nivolumab (BMS-936558/ONO-4538), is the first PD-1 inhibitor to gain regulatory approval, for the treatment of patients with unresectable melanoma. This review will discuss results from early phase studies of nivolumab in solid tumors including non-small cell lung cancer (NSCLC) as well as studies of nivolumab in combination with chemotherapy, other immune modulators and molecular targeted therapy in patients with NSCLC.

Suppressive effects of gemcitabine plus cisplatin chemotherapy on regulatory T cells in nonsmall-cell lung cancer

OBJECTIVE

To investigate the effect of gemcitabine plus cisplatin chemotherapy on the percentage of CD4(+)CD25(+)FOXP3(+) and CD8(+)CD28(-) regulatory T cells (Tregs) in the peripheral blood of patients with nonsmall-cell lung cancer (NSCLC).

METHODS

Peripheral blood was taken from patients with NCSLC (before and after chemotherapy) and control subjects with nonmalignant disease. The percentages of CD4(+)CD25(+)FOXP3(+) and CD8(+)CD28(-) Tregs were analysed using flow cytometry.

RESULTS

Patients (n = 40) had significantly higher CD4(+)CD25(+)FOXP3(+) and CD8(+)CD28(-) percentages than control subjects (n = 24). CD4(+)CD25(+)FOXP3(+) and CD8(+)CD28(-) percentages increased with tumour progression, fell significantly after chemotherapy, but remained significantly higher than control values.

CONCLUSIONS

CD4(+)CD25(+)FOXP3(+) and CD8(+)CD28(-) Treg percentages were higher in patients with NSCLC than control subjects, and increased in line with tumour progression. Percentages of CD4(+)CD25(+)FOXP3(+) and CD8(+)CD28(-) Tregs were significantly reduced following gemcitabine plus cisplatin chemotherapy.

Chemotherapy and Oncolytic Virotherapy: Advanced Tactics in the War against Cancer

Cancer is a traitorous archenemy that threatens our survival. Its ability to evade detection and adapt to various cancer therapies means that it is a moving target that becomes increasingly difficult to attack. Through technological advancements, we have developed sophisticated weapons to fight off tumor growth and invasion. However, if we are to stand a chance in this war against cancer, advanced tactics will be required to maximize the use of our available resources. Oncolytic viruses (OVs) are multi-functional cancer-fighters that can be engineered to suit many different strategies; in particular, their retooling can facilitate increased capacity for direct tumor killing (oncolytic virotherapy) and elicit adaptive antitumor immune responses (oncolytic immunotherapy). However, administration of these modified OVs alone, rarely induces successful regression of established tumors. This may be attributed to host antiviral immunity that acts to eliminate viral particles, as well as the capacity for tumors to adapt to therapeutic selective pressure. It has been shown that various chemotherapeutic drugs with distinct functional properties can potentiate the antitumor efficacy of OVs. In this review, we summarize the chemotherapeutic combinatorial strategies used to optimize virally induced destruction of tumors. With a particular focus on pharmaceutical immunomodulators, we discuss how specific therapeutic contexts may alter the effects of these synergistic combinations and their implications for future clinical use.

Antitumor activity of total flavonoids from Tetrastigma hemsleyanum Diels et Gilg is associated with the inhibition of regulatory T cells in mice

Objective

To determine the antitumor activity of Radix tetrastigmae flavonoids and their inhibitory effect on regulatory T cells (Tregs) in mice.

Materials and methods

Total flavonoids were isolated from Radix tetrastigmae, the root of Tetrastigma hemsleyanum Diels et Gilg, and administered to C57BL/6 mice by oral gavage after inoculation with Lewis lung carcinoma (LLC) cells. The effects of total flavonoids on tumor growth in vivo were examined. Flow cytometry was used to study the effects on Tregs, and enzyme-linked immunosorbent assay was used to analyze the changes in the serum levels of transforming growth factor β, prostaglandin E2, and cyclooxygenase 2 after tumor inoculation and flavonoid administration.

Results

Total flavonoids from T. hemsleyanum Diels et Gilg significantly inhibited tumor growth in C57BL/6 mice inoculated with LLCs. These flavonoids dramatically suppressed regulatory T-cell development in tumor-bearing mice. Further studies revealed that total flavonoids significantly decreased the serum levels of transforming growth factor β, prostaglandin E2, and cyclooxygenase 2 in tumor-bearing mice, which may be responsible for the inhibition of Tregs.

Conclusion

The antitumor activity of total flavonoids from T. hemsleyanum Diels et Gilg is associated with the inhibition of Tregs in a mouse tumor model. Total flavonoids from T. hemsleyanum Diels et Gilg may be used as antitumor agents in cancer prevention and treatment.

Combination of Sasa quelpaertensis Nakai Leaf Extract and Cisplatin Suppresses the Cancer Stemness and Invasion of Human Lung Cancer Cells

Lung cancer is the leading cause of cancer death worldwide, and most chemotherapeutic drugs have limited success in treating this disease. Furthermore, some drugs show undesirable side effects due to the enrichment of cancer stem cells (CSCs) that are present, leading to resistance to conventional chemotherapy and tumor relapse. CSCs possess self-renewal characteristics, aggressive tumor initiating activity, and ability to facilitate tumor metastasis. Therefore, development of nontoxic agents that can potentiate chemotherapy and eliminate CSCs would be highly desirable. In the present study, we investigated whether Sasa quelpaertensis leaf extracts (SQE) and cisplatin (CIS), individually or in combination, would exert anti-CSC and antimetastatic effect in H1299 and A549 human lung cancer cells. Following these treatments, cell growth, phosphorylation of phosphoinositide-3 kinase, and activation of the mammalian target of rapamycin were inhibited. Decreased serial sphere formation, clonogenicity, and expression of major stem cell markers, such as CD44 and SOX-2, in CD44+ cancer stem cells were also observed. In addition, inhibition of cell migration and invasion in both cell lines as well as inhibition of matrix metalloproteinase-2 activity and expression were detected. Importantly, the anticancer stemness and antimetastasis effects in each of these assays were greater for the combined treatment with SQE and CIS than with each treatment individually. In conclusion, the data suggest that SQE alone, or in combination with CIS, represents a promising therapeutic strategy for eliminating cancer stemness and cell invasion potential of CSCs, thereby treating and preventing metastatic lung cancer cells.

Chemotherapeutic targeting of cancer-induced immunosuppressive cells

The expansion of immunosuppressive cells represents a cardinal strategy deployed by tumors to escape from detection and elimination by the immune system. Regulatory T lymphocytes (Treg) and myeloid-derived suppressor cells (MDSC), major components of these inhibitory cellular networks, have drawn intense scrutiny in recent years. In patients with cancer and in animal tumor models, these suppressor cells accumulate in the tumor microenvironment, secondary lymphoid tissues, and in the blood. Equipped with the ability to suppress innate and adaptive anticancer immunity, these cells also foster disease development by promoting tumor neoangiogenesis and by enhancing cancer metastasis. They therefore represent major impediments for anticancer therapies, particularly for immune-based interventions. Recent work has provided evidence that beyond their direct cytotoxic or cytostatic effects on cancer cells, several conventional chemotherapeutic drugs and agents used in targeted therapies can promote the elimination or inactivation of suppressive Tregs or MDSCs, resulting in enhanced antitumor immunity. We analyze findings pertinent to this concept, discuss the possible molecular bases underlying the selective targeting of these immunosuppressive cells by antineoplastic agents, and consider current challenges and future prospects related to the integration of these molecules into more efficient anticancer chemoimmunotherapeutic strategies.

Immune-based mechanisms of cytotoxic chemotherapy: implications for the design of novel and rationale-based combined treatments against cancer

Conventional anticancer chemotherapy has been historically thought to act through direct killing of tumor cells. This concept stems from the fact that cytotoxic drugs interfere with DNA synthesis and replication. Accumulating evidence, however, indicates that the antitumor activities of chemotherapy also rely on several off-target effects, especially directed to the host immune system, that cooperate for successful tumor eradication. Chemotherapeutic agents stimulate both the innate and adaptive arms of the immune system through several modalities: (i) by promoting specific rearrangements on dying tumor cells, which render them visible to the immune system; (ii) by influencing the homeostasis of the hematopoietic compartment through transient lymphodepletion followed by rebound replenishment of immune cell pools; (iii) by subverting tumor-induced immunosuppressive mechanisms and (iv) by exerting direct or indirect stimulatory effects on immune effectors. Among the indirect ways of immune cell stimulation, some cytotoxic drugs have been shown to induce an immunogenic type of cell death in tumor cells, resulting in the emission of specific signals that trigger phagocytosis of cell debris and promote the maturation of dendritic cells, ultimately resulting in the induction of potent antitumor responses. Here, we provide an extensive overview of the multiple immune-based mechanisms exploited by the most commonly employed cytotoxic drugs, with the final aim of identifying prerequisites for optimal combination with immunotherapy strategies for the development of more effective treatments against cancer.

Changes in the immune cell population and cell proliferation in peripheral blood after gemcitabine-based chemotherapy for pancreatic cancer

PURPOSE

Regulatory T cells (Tregs) play a role in the immunosuppressive state in pancreatic cancer patients. We aimed to evaluate the changes of immune cells population including Tregs caused by gemcitabine (GEM)-based chemotherapy.

METHODS

Fifty-three patients with pancreatic cancer were enrolled in this study, of which 32 received GEM- based chemotherapy. Blood samples were collected before and at least 2 weeks after the last dose of chemotherapy. The peripheral blood mononuclear cells (PBMCs) were subjected to flow cytometry analysis after labeling with anti-CD4, anti-CD25, and anti-Foxp3 antibodies. Other lymphocytes and NK cell markers were also measured. The proliferative capacity of PBMCs stimulated with anti-CD3 was analyzed using H(3) thymidine.

RESULTS

The percentage and number of Tregs were significantly decreased after chemotherapy (p = 0.032, p = 0.003, respectively). The other immune cells and the proliferative capacity did not change.

CONCLUSION

This study showed that GEM-based chemotherapy produced an immunomodulatory effect via the depletion of Tregs.

Therapeutic vaccines for ovarian cancer

While therapeutic vaccines for ovarian cancer represent only a small fraction of active clinical trials, growing interest in this area and the accumulated data supporting the use of vaccines in cancer treatment portend further expansion of trials incorporating these strategies. This review explores the rationale for the use of vaccines for the treatment of ovarian cancer. It examines vaccine platforms that have been investigated and reviews the data from these studies. We also highlight recently reported phase 2 and 3 clinical trials with clinical outcomes as endpoints. Finally, we consider directions for the next generation of vaccines in light of these findings and our emerging understanding of agents that may augment vaccine responses by targeting the immunosuppressive impact of the tumor microenvironment.

Personalized therapy for metastatic melanoma: could timing be everything?

There is ample evidence that immune-related processes in humans are under temporal regulation. The circadian variation of humoral and cellular immunity is well documented and appears to be hormonally modulated via the hypothalamic-pituitary-adrenal axis. In advanced melanoma, it has recently been demonstrated that systemic immunity is repolarized toward a global state of chronic inflammation (Th2 dominance) and appears to be governed by infradian biorhythms of cytokines and immune cell subsets, which extend beyond the 24-h circadian variability reported in healthy volunteers. It is suggested that synchronizing administration of lymphodepleting chemotherapy (temozolomide) with these endogenous (individualized) immune dynamics (biorhythms) in patients with advanced/metastatic melanoma improves clinical outcomes compared with temozolomide used in a conventional 'random delivery' fashion.

Novel mechanism of synergistic effects of conventional chemotherapy and immune therapy of cancer

There is mounting evidence to support the use of a combination of immunotherapy with chemotherapy in the treatment of various types of cancers. However, the mechanism(s), by which these modalities are synergized, are not fully understood. In this review, we discuss several possible mechanisms of the combined effect of immunotherapy and chemotherapy of cancer. We will examine various aspects of this issue such as the combination of different treatment options, the dosage for each arm of treatment, and, more importantly, the timing and sequence of the administration of these treatments.

Concomitant combination of active immunotherapy and carboplatin- or paclitaxel-based chemotherapy improves anti-tumor response

Recent preclinical evidence substantially supports the successful combination of chemotherapies and active immunotherapy for cancer treatment. These data sustain the effect of sequential combination schemes (vaccine plus chemotherapy or vice versa), which could be difficult to implement in clinical practice. Since chemotherapy is the standard treatment for most cancers, ethical issues forbid its delay and make difficult the evaluation of other treatments such as using an immunotherapeutic agent. Besides, vaccines must be applied as soon as possible to advanced cancer patients, in order to give them time to develop an effective immune response. Thus, a clinically attractive scenario is the concomitant application of treatments. However, little is known about the specific effect of different chemotherapeutic agents when combined with a cancer vaccine in such concomitant treatment. In this work, we analyze the influence of high-dose carboplatin or paclitaxel in the generation of a specific immune response when administered concomitantly with an OVA vaccine. Interestingly, neither carboplatin nor paclitaxel affects the humoral and CTL in vivo response generated by the vaccine. Moreover, an enhancement of the overall anti-tumor effect was observed in animals treated with OVA/CF vaccine combined with cytotoxic drugs. Moreover, the effect of the concomitant treatment was tested using a tumor-related antigen, the epidermal growth factor (EGF). Animals administered with EGF-P64k/Montanide and cytotoxic agents showed an antibody response similar to that from control animals. Therefore, our study suggests that carboplatin and paclitaxel can be concomitantly combined with active immunotherapies in the clinical practice of advanced cancer patients.

Suppression, subversion and escape: the role of regulatory T cells in cancer progression

Regulatory T cells (T(regs) ) are crucial in mediating immune homeostasis and promoting the establishment and maintenance of peripheral tolerance. However, in the context of cancer their role is more complex, and they are thought to contribute to the progress of many tumours. As cancer cells express both self- and tumour-associated antigens, T(regs) are key to dampening effector cell responses, and therefore represent one of the main obstacles to effective anti-tumour responses. Suppression mechanisms employed by T(regs) are thought to contribute significantly to the failure of current therapies that rely on induction or potentiation of anti-tumour responses. This review will focus on the current evidence supporting the central role of T(regs) in establishing tumour-specific tolerance and promoting cancer escape. We outline the mechanisms underlying their suppressive function and discuss the potential routes of T(regs) accumulation within the tumour, including enhanced recruitment, in-situ or local proliferation, and de-novo differentiation. In addition, we review some of the cancer treatment strategies that act, at least in part, to eliminate or interfere with the function of T(regs) . The role of T(regs) is being recognized increasingly in cancer, and controlling the function of these suppressive cells in the tumour microenvironment without compromising peripheral tolerance represents a significant challenge for cancer therapies.

Chemoimmunotherapy: reengineering tumor immunity

Cancer chemotherapy drugs have long been considered immune suppressive. However, more recent data indicate that some cytotoxic drugs effectively treat cancer in part by facilitating an immune response to the tumor when given at the standard dose and schedule. These drugs induce a form of tumor cell death that is immunologically active, thereby inducing an adaptive immune response specific for the tumor. In addition, cancer chemotherapy drugs can promote tumor immunity through ancillary and largely unappreciated immunologic effects on both the malignant and normal host cells present within the tumor microenvironment. These more subtle immunomodulatory effects are dependent on the drug itself, its dose, and its schedule in relation to an immune-based intervention. The recent approvals of two new immune-based therapies for prostate cancer and melanoma herald a new era in cancer treatment and have led to heightened interest in immunotherapy as a valid approach to cancer treatment. A detailed understanding of the cellular and molecular basis of interactions between chemotherapy drugs and the immune system is essential for devising the optimal strategy for integrating new immune-based therapies into the standard of care for various cancers, resulting in the greatest long-term clinical benefit for cancer patients.

Substantially modified ratios of effector to regulatory T cells during chemotherapy in ovarian cancer patients return to pre-treatment levels at completion: implications for immunotherapy

Ovarian cancer is the leading cause of death from gynaecological malignancy. Despite improved detection and treatment options, relapse rates remain high. Combining immunotherapy with the current standard treatments may provide an improved prognosis, however, little is known about how standard chemotherapy affects immune potential (particularly T cells) over time, and hence, when to optimally combine it with immunotherapy (e.g., vaccines). Herein, we assess the frequency and ratio of CD8+ central memory and effector T cells as well as CD4+ effector and regulatory T cells (Tregs) during the first 18 weeks of standard chemotherapy for ovarian cancer patients. In this pilot study, we observed increased levels of recently activated Tregs with tumor migrating ability (CD4+CD25^hiFoxp3+CD127−CCR4+CD38+ cells) in patients when compared to controls. Although frequency changes of Tregs as well as the ratio of effector T cells to Tregs were observed during treatment, the Tregs consistently returned to pre-chemotherapy levels at the end of treatment. These results indicate T cell subset distributions associated with recurrence may be largely resistant to being “re-set” to healthy control homeostatic levels following standard treatments. However, it may be possible to enhance T effector to Treg ratios transiently during chemotherapy. These results suggest personalized immune monitoring maybe beneficial when combining novel immuno-therapeutics with standard treatment for ovarian cancer patients.

Targeting regulatory T cells

Cancers express tumor-associated antigens that should elicit immune response to antagonize the tumor growth, but spontaneous immune rejection of established cancer is rare, suggesting an immunosuppressive environment hindering host antitumor immunity. Among the specific and active tumor-mediated mechanisms, CD4(+)CD25(high) T regulatory cells (Treg) are important mediators of active immune evasion in cancer. In this review, we will discuss Treg subpopulations and the mechanisms of their suppressive functions. Treg depletion improves endogenous antitumor immunity and the efficacy of active immunotherapy in animal models for cancer, suggesting that inhibiting Treg function could also improve the limited successes of human cancer immunotherapy. We will also discuss specific strategies for devising effective cancer immunotherapy targeting Treg.

Low-dose paclitaxel enhances the anti-tumor efficacy of GM-CSF surface-modified whole-tumor-cell vaccine in mouse model of prostate cancer

Chemotherapy combined with a tumor vaccine is an attractive approach in cancer therapy. This study was designed to investigate the optimal schedule and mechanisms of action of a novel GM-CSF (granulocyte-macrophage colony-stimulating factor) surface-modified tumor-cell vaccine in combination with paclitaxel in the treatment of mouse RM-1 prostate cancer. First, the anti-tumor efficiencies of various dosage of paclitaxel (4, 20, 40 mg/kg) in combination with the vaccine in different administration sequences were examined in the mouse RM-1 prostate cancer model. Then, the in vivo and in vitro effects of various dosage of paclitaxel on RM-1 cells, T cells, and DCs (dendritic cells) were evaluated. The results showed that: (a) the GM-CSF-surface-modified tumor-cell vaccine was more potent at inducing the uptake of tumor antigens by DCs than irradiated tumor cells plus free GM-CSF; (b) 4 mg/kg paclitaxel combined with the GM-CSF-surface-modified tumor-cell vaccine was the most effective at enhancing tumor regression in RM-1 prostate cancer mice when the vaccine was administrated 2 days after paclitaxel; and (c) administration of 4 mg/kg paclitaxel followed by the vaccine induced the highest degree of CD8(+) T-cell infiltration in tumor tissue, suggesting that the induction of tumor-specific immune response had occurred. These findings suggested that the GM-CSF-surface-modified tumor-cell vaccine may have potential clinical benefit for patients with prostate cancer when it is combined with paclitaxel. Furthermore, the effect of immunochemotherapy depends on careful selection of paclitaxel dosage and the sequence of paclitaxel/vaccine administration.

Immunological and clinical effects of vaccines targeting p53-overexpressing malignancies

Approximately 50% of human malignancies carry p53 mutations, which makes it a potential antigenic target for cancer immunotherapy. Adoptive transfer with p53-specific cytotoxic T-lymphocytes (CTL) and CD4⁺ T-helper cells eradicates p53-overexpressing tumors in mice. Furthermore, p53 antibodies and p53-specific CTLs can be detected in cancer patients, indicating that p53 is immunogenic. Based on these results, clinical trials were initiated. In this paper, we review immunological and clinical responses observed in cancer patients vaccinated with p53 targeting vaccines. In most trials, p53-specific vaccine-induced immunological responses were observed. Unfortunately, no clinical responses with significant reduction of tumor-burden have occurred. We will elaborate on possible explanations for this lack of clinical effectiveness. In the second part of this paper, we summarize several immunopotentiating combination strategies suitable for clinical use. In our opinion, future p53-vaccine studies should focus on addition of these immunopotentiating regimens to achieve clinically effective therapeutic vaccination strategies for cancer patients.

Dendritic cell vaccination against ovarian cancer--tipping the Treg/TH17 balance to therapeutic advantage?

The pathology of ovarian cancer is characterized by profound immunosuppression in the tumor microenvironment. Mechanisms that contribute to the immunosuppressed state include tumor infiltration by regulatory T cells (Treg), expression of B7-H1 (PDL-1), which can promote T cell anergy and apoptosis through engagement of PD-1 expressed by effector T cells, and expression of indoleamine 2,3-dioxygenase (IDO), which can also contribute to effector T cell anergy. Expression of both B7-H1 and IDO has been associated with differentiation and recruitment of Treg, and clinical studies have shown that each of these mechanisms correlates independently with increased morbidity and mortality in patients with ovarian cancer. In a remarkable counterpoint to these observations, ovarian tumor infiltration with T(H)17 cells correlates with markedly improved clinical outcomes. In this Future Perspectives review, we argue that dendritic cell (DC) vaccination designed to drive tumor-antigen-specific T(H)17 T cell responses, combined with adjuvant treatments that abrogate immunosuppressive mechanisms operative in the tumor microenvironment, offers the potential for clinical benefit in the treatment of ovarian cancer. We also discuss pharmacological approaches to modulation of MAP kinase signaling for manipulation of the functional plasticity of DC, such that they may be directed to promote T(H)17 responses following DC vaccination.

Contribution of the immune system to the chemotherapeutic response

The immune system plays an important role in the surveillance of neoplastic cells by eliminating them before they manifest as full-blown cancer. Despite this, tumors do develop in the presence of a functioning immune system. Conventional chemotherapy and its ability to directly kill tumor cells is one of the most effective weapons in the fight against cancer, however, increasing evidence suggests that the therapeutic efficacy of some cytotoxic drugs relies on their capacity to interact with the immune system. Killing of tumor cells in a manner that favors their capture by immune cells or selective targeting of immunosuppressive pathways by specific chemotherapies promotes the generation of an effective anti-cancer response; however, this alone is rarely sufficient to cause elimination of advanced disease. An understanding of the immunological events occurring in both animal models and patients undergoing chemotherapy will guide decisions for the development of appropriate combinations and scheduling for the integration of chemotherapy with immunotherapy.

Chemoimmunotherapy

Cancer chemotherapy drugs are historically regarded as detrimental to immunity because of their myelosuppressive effects. However, accumulating data suggest that the antitumor activity of conventional cancer chemotherapy results in part from its ability to harness the innate and adaptive immune systems by inducing immunologically active tumor cell death. Additional data broaden the immunologic effect of cancer chemotherapy drugs, demonstrating that some drugs have the ability to disrupt pathways of immune suppression and immune tolerance in a manner that depends on the drug dose, and the timing of its administration in relation to immunotherapy. Understanding the cellular and molecular basis of the interactions between chemotherapy drugs and the immune system will facilitate the strategic development of chemoimmunotherapy treatment regimens that both maximize tumor regression and the antitumor immune response for the long-term clinical benefit of cancer patients.

Selective impairment of CD4+CD25+Foxp3+ regulatory T cells by paclitaxel is explained by Bcl-2/Bax mediated apoptosis

Paclitaxel has become one of the most effective and widely used chemotherapeutic agents over the past decades. Although it has shown promise to selectively deplete regulatory T (Treg) cells in our previous study, the underlying molecular mechanism remains to be further elucidated. The present study focused on the effect of paclitaxel on Treg cells in 3LL Lewis tumor model and explored the possible molecular pathways involved in this process. We found that paclitaxel significantly decreased the percentage of Treg cells in CD4(+) cells and impaired their suppressive functions, but effector T (Teff) cells remained unaffected. Compared with Teff cells, Treg cells exhibited a high sensitivity to paclitaxel-mediated apoptosis in vitro. Interestingly, though paclitaxel has been characterized as a mitotic inhibitor, tubulin was not involved in the selective function of paclitaxel. Treg cells exposed to paclitaxel displayed downregulation of Bcl-2 and upregulation of Bax. Blocking the Bcl-2 pathway eliminated the difference between Treg and Teff cells responding to paclitaxel. These results suggest that Bcl-2 rather than tubulin contributes to the distinctive effect of paclitaxel on Treg cells. Therefore, we here identify a molecular pathway through which paclitaxel selectively ablates Treg cells.

Therapeutic cancer vaccines in combination with conventional therapy

The clinical efficacy of most therapeutic vaccines against cancer has not yet met its promise. Data are emerging that strongly support the notion that combining immunotherapy with conventional therapies, for example, radiation and chemotherapy may improve efficacy. In particular combination with chemotherapy may lead to improved clinical efficacy by clearing suppressor cells, reboot of the immune system, by rendering tumor cells more susceptible to immune mediated killing, or by activation of cells of the immune system. In addition, a range of tumor antigens have been characterized to allow targeting of proteins coupled to intrinsic properties of cancer cells. For example, proteins associated with drug resistance can be targeted, and form ideal target structures for use in combination with chemotherapy for killing of surviving drug resistant cancer cells. Proteins associated with the malignant phenotype can be targeted to specifically target cancer cells, but proteins targeted by immunotherapy may also simultaneously target cancer cells as well as suppressive cells in the tumor stroma.

Chemotherapy enhances tumor cell susceptibility to CTL-mediated killing during cancer immunotherapy in mice

Cancer immunotherapy faces a serious challenge because of low clinical efficacy. Recently, a number of clinical studies have reported the serendipitous finding of high rates of objective clinical response when cancer vaccines are combined with chemotherapy in patients with different types of cancers. However, the mechanism of this phenomenon remains unclear. Here, we tested in mice several cancer vaccines and an adoptive T cell transfer approach to cancer immunotherapy in combination with several widely used chemotherapeutic drugs. We found that chemotherapy made tumor cells more susceptible to the cytotoxic effect of CTLs through a dramatic perforin-independent increase in permeability to GrzB released by the CTLs. This effect was mediated via upregulation of mannose-6-phosphate receptors on the surface of tumor cells and was observed in mouse and human cells. When combined with chemotherapy, CTLs raised against specific antigens were able to induce apoptosis in neighboring tumor cells that did not express those antigens. These data suggest that small numbers of CTLs could mediate a potent antitumor effect when combined with chemotherapy. In addition, these results provide a strong rationale for combining these modalities for the treatment of patients with advanced cancers.

Enhancement of antitumor immunity by low-dose total body irradiationis associated with selectively decreasing the proportion and number of T regulatory cells

Low-dose total body irradiation (LTBI) is used in the treatment of some cancers mainly for immune enhancement rather than cell killing. However, the mechanism underlying LTBI remains unknown. In this study, by analyzing the immune patterns of lymphocytes, we found that the percentage and absolute number of CD4(+)CD25(+)Foxp3(+) regulatory T cells are markedly decreased in naive mice following treatment with LTBI. On the contrary, the CD4(+)CD44(+)/CD8(+)CD44(+) effect or-memory T cells are greatly increased. Importantly, naive mice treated with dendritic cell-gp 100 tumor vaccines under LTBI induced an enhancement of antigen-specific proliferation and cytotoxicity as well as interferon-gamma (IFN-gamma) secretion against F10 melanoma tumor challenge, compared to treatment with either the tumor vaccine or LTBI alone. Consequently, the treatment resulted in a reduced tumor burden and prolonged mouse survival. Our data demonstrate that LTBI's enhancement of antitumor immunity was mainly associated with selectively decreasing the proportion and number of T regulatory cells,implying the potential application of the combination of LTBI and a tumor vaccine in antitumor therapy.