The determination of individual sensitivity to 5-fluorouracil in patients with malignant tumors in different locations]

Possible determination of individual chemosensitivity of tumors to 5-fluorouracil was investigated using new original data and suggestions that lymphocytes of the tumor carrier have an ability to assimilate chemical drugs. Such an ability is likely due to the fact that 5-fluorouracil as an antimetabolite converted its action by inclusion of lymphocytes to the nucleic acid metabolism. The relation between the phenomenon and the chemotherapy efficacy is possibly realized through two mechanisms. One of them is the direct cytotoxic action of chemical drugs on lymphocyte tumor-associated clones resulting in impairment of the tumor growth control. The other is possible participation of lymphocytes in transport of chemical drugs to the tumor tissue. The in vitro model for estimation of tumor carrier chemosensitivity by the level of the nucleic acid metabolism reflects the impact of the immune system on realization of the antitumor effect of chemical drugs.     

TGF-β1 and hypoxia-dependent expression of MKP-1 leads tumor resistance to death receptor-mediated cell death

Sporadic occurrence of transformed tumor cells is under the surveillance of the host immune system and such cells are effectively eliminated by immune-mediated cell death. During tumor progression, the antitumor effects of the tumor microenvironment are suppressed by diverse immunosuppressive mechanisms. In this research, we suggest novel immune evasion strategy of tumor cells through a transforming growth factor (TGF)-β1- and hypoxia-dependent mechanism. Experimental results showed that TGF-β1 and hypoxia induced mitogen-activated protein kinase phosphatase (MKP)-1 expression within 1 h, resulting in attenuation of c-Jun N-terminal kinase (JNK) phosphorylation and subsequent death receptor-mediated cell death. In addition, analysis of microarray data and immunostaining of MKP-1 in hepatocellular carcinoma (HCC) patient samples revealed that expression of MKP-1 is notably higher in tumors than in normal tissues, implying that MKP-1-dependent suppression of immune-mediated cell death takes place only in the tumor. To prove that MKP-1 can act as a mediator of immune escape by tumors, we determined whether chemo-resistance against several anticancer drugs could be overcome by knockdown of MKP-1. Cytotoxic assays showed that chemotherapy with siRNA targeting MKP-1 was significantly more effective than chemotherapy in the presence of MKP-1. Thus, we conclude that TGF-β1 and hypoxia ensure tumor cell survival and growth through expression of MKP-1.     

Antitumor mechanisms of oligodeoxynucleotides with CpG and polyG motifs in murine prostate cancer cells: decrease of NF-kappaB and AP-1 binding activities and induction of apoptosis

Previous studies have shown that CpG oligodeoxynucleotides (ODNs) have substantial immunostimulatory effects with anticancer applications. The antitumor applications that have been described previously are mediated through the CpG-induced activation of the host immune system, not through direct antitumor effects. Using cytostasis and cell proliferation assays, we demonstrated that specific ODNs inhibit the proliferation of RM-1 cells, a murine prostate cancer cell line. Flow cytometry analysis using propidium iodide (PI) nuclear staining confirmed the direct proapoptotic effect of ODNs on prostate cancer cells. This effect was dose dependent. Further studies using Western blot analysis and electrophoresis mobility shift assay (EMSA) revealed that the treatment of prostate cancer cells with specific ODNs activated the caspase pathway(s) and decreased the binding activities of AP-1 and NF-kappaB in a time-dependent manner. Evaluation of a panel of ODNs containing different DNA motifs demonstrated that the optimal proapoptotic sequences required polyG sequences but that CpG motifs were not essential. Finally, in vivo antitumor studies showed that the proapoptotic polyG motifs significantly inhibited prostate tumor growth. PolyG motifs inhibited tumor growth, and the effects were enhanced by CpG immune activating sequences. ODN containing both polyG and CpG motifs may have enhanced efficacy in tumor therapy through multiple mechanisms of action, including direct antitumor activities and immune activation.     

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.     

Taxol-mediated changes in fibrosarcoma-induced immune cell function: Modulation of antitumor activities

 The anticancer drug taxol (paclitaxel) inhibits tumors through multiple cytotoxic and cytostatic mechanisms. Independently of these mechanisms, taxol induces distinct immunological efficacy when it acts as a second signal for activation of tumoricidal activity by interferon-γ(IFNγ)-primed murine normal host macrophages. We reported that tumor-distal macrophages, which mediate immunosuppression through dysregulated nitric oxide (NO) and tumor necrosis factor α (TNFα) production, are differentially regulated by taxol. Because taxol influences tumor cell growth dynamics and activates immune cell populations, we assessed the ex vivo immunosuppressive and antitumor activities of taxol-treated normal host and tumor-bearing host (TBH) macrophages. Pretreatment of such cells with taxol partly reconstituted T cell alloantigen reactivity, suggesting that taxol mediates a limited reversal of TBH macrophage immunosuppressive activity. Taxol-treated TBH macrophages significantly suppressed the growth of fibrosarcoma cells (Meth-KDE) through soluble effector molecules and promoted direct cell-mediated cytotoxicity, indicating that taxol enhanced tumor-induced macrophage antitumor activities. Tumor-induced helper T cells, however, showed a higher sensitivity to direct taxol-induced suppression. These data demonstrate that taxol exerts pleiotropic effects on antitumor immune responses with the capacity to abate the immunosuppressive activities of macrophages and promote macrophage-mediated antitumor activities simultaneously, but also directly modulating T cell reactivity. Collectively, these studies suggest that the antineoplastic drug taxol may impart antitumor activity through an immunotherapeutic capacity. Received: 31 December 1996 / Accepted: 1 July 1997     

The 'kiss of death' by dendritic cells to cancer cells

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) specialized in the stimulation of na?ve T lymphocytes, which are key components of antiviral and antitumor immunity. DCs are 'sentinels' of the immune system endowed with the mission to (1) sense invading pathogens as well as any form of tissue distress and (2) alert the effectors of the immune response. They represent a very heterogeneous population including subsets characterized by their anatomical locations and specific missions. Beyond their unique APC features, DCs exhibit a large array of effector functions that play critical roles in the induction and regulation of the cell-mediated as well as humoral immune responses. In the course of the antitumor immune response, DCs are unique in engulfing tumor cells killed by natural killer (NK) cells and cross-presenting tumor-associated antigens to cytotoxic T lymphocytes (CTLs). However, while DCs mediate antitumor immune responses by stimulating tumor-specific CTLs and NK cells, direct tumoricidal mechanisms have been recently evoked. This review addresses the other face of DCs to directly deliver apoptotic signals to stressed cells, their role in tumor cell death, and its implication in the design of DC-based cancer immunotherapies.     

Cancer chemotherapy: not only a direct cytotoxic effect, but also an adjuvant for antitumor immunity

Treatment of metastatic cancer mainly relies on chemotherapy. Chemotherapeutic agents kill tumor cells by direct cytotoxicity, thus leading to tumor regression. However, emerging data focus on another side of cancer chemotherapy: its antitumor immunity effect. Although cancer chemotherapy was usually considered as immunosuppressive, some chemotherapeutic agents have recently been shown to activate an anticancer immune response, which is involved in the curative effect of these treatments. Cancer development often leads to the occurrence of an immune tolerance that prevents cancer rejection by the immune system and hinders efficacy of immunotherapy. Cancer cells induce proliferation and local accumulation of immunosuppressive cells such as regulatory T cells and immature myeloid cells, and prevent the maturation of dendritic cells and their capacity to present tumor antigens to T lymphocytes. Many anticancer cytotoxic agents interfere with the molecular and cellular mechanisms leading to tumor-induced tolerance. They can restore an efficient immune response that contributes to the therapeutic effects of chemotherapy. These findings open a novel field of investigations for future clinical trial design, taking into account the immunostimulatory capacity of chemotherapeutic agents, and using them in combined chemo-immunotherapy strategies when tumor-induced tolerance is overcome.     

Preexisting antitumor immunity augments the antitumor effects of chemotherapy

Efficacy of cancer chemotherapy is generally believed to be the result of direct drug killing of tumor cells. However, increased tumor cell killing does not always lead to improved efficacy. Herein, we demonstrate that the status of antitumor immunity at the time of chemotherapy treatment is a critical factor affecting the therapeutic outcome in that tumor-bearing mice that possess preexisting antitumor immunity respond to chemotherapy much better than those that do not. Enhancing antitumor immunity before or at the time of chemotherapy-induced antigen release increases subsequent response to chemotherapy significantly. By in vitro and in vivo measurements of antitumor immunity, we found a close correlation between the intensity of antitumor immunity activated by chemotherapy and the efficacy of treatment. Immune intervention with interleukin-12 during the early phase of chemotherapy-induced immune activation greatly amplifies the antitumor response, often resulting in complete tumor eradication not only at the chemo-treated local site, but also systemically. These findings provide additional evidence for an immune-mediated antitumor response to chemotherapy. Further, our results show that timely immune modification of chemotherapy-activated antitumor immunity can result in enhanced antitumor-immune response and complete tumor eradication.     

Direct tumor damage mechanisms of photodynamic therapy

Photodynamic therapy (PDT) is a clinically approved and rapidly developing cancer treatment regimen. It is a minimally invasive two-stage procedure that requires administration of a photosensitizing agent followed by illumination of the tumor with visible light usually generated by laser sources. A third component of PDT is molecular oxygen which is required for the most effective antitumor effects. In the presence of the latter, light of an appropriate wavelength excites the photosensitizer thereby producing cytotoxic intermediates that damage cellular structures. PDT has been approved in many countries for the treatment of lung, esophageal, bladder, skin and head and neck cancers. The antitumor effects of this treatment result from the combination of direct tumor cell photodamage, destruction of tumor vasculature and activation of an immune response. The mechanisms of the direct photodamage of tumor cells, the signaling pathways that lead to apoptosis or survival of sublethaly damaged cells, and potential novel strategies of improving the antitumor efficacy of PDT are discussed.     

Interferon-alpha and cancer: mechanisms of action and new perspectives of clinical use

Interferons-alpha (IFN-alpha) are pleiotropic cytokines belonging to type I IFNs, extensively used in the treatment of patients with some types of cancer and viral disease. IFN-alpha can affect tumor cell functions by multiple mechanisms. In addition, these cytokines can promote the differentiation and activity of host immune cells. Early studies in mouse tumor models showed the importance of host immune mechanisms in the generation of a long-lasting antitumor response after treatment of the animals with IFN-alpha/beta. Subsequently, an ensemble of studies based on the use of genetically modified tumor cells expressing specific IFN molecules provided important information on the host-mediated antitumor mechanisms induced by the local production of IFN-alpha. Of note, several studies have then underscored new immunomodulatory effects of IFN-alpha, including activities on T cells and dendritic cells, which may lead to IFN-induced antitumor immunity. In addition, recent reports on new immune correlates in cancer patients responding to IFN-alpha represent additional evidence on the importance of the interactions of IFN-alpha with the immune system for the generation of a durable antitumor response. On the whole, this knowledge suggests the advantage of using these cytokines as adjuvants of cancer vaccines and for the in vitro generation of highly active dendritic cells to be utilized for therapeutic vaccination of cancer patients.     

Tracing and targeting cancer stem cells: New venture for personalized molecular cancer therapy

Tumors consist of a mixture of heterogeneous cell types. Cancer stem cells(CSCs) are a minor sub-population within the bulk cancer fraction which has been foundto reconstitute and propagate the disease and to be frequently resistant to chemotherapy, irradiation, cytotoxic drugs and probably also against immune attack. CSCs are considered as the seeds of tumor recurrence, driving force of tumorigenesis and metastases. This underlines the urgent need for innovative methods to identify and target CSCs. However, the role and existence of CSCs in therapy resistance and cancer recurrence remains a topic of intense debate. The underlying biological properties of the tumor stem cells are extremely dependent on numerous signals, and the targeted inhibition of these stem cell signaling pathways is one of the promising approaches of the new antitumor therapy approaches. This perspective review article summarizes the novel methods of tracing CSCs and discusses the hallmarks of CSC identification influenced by the microenvironment or by having imperfect detection markers. In addition, explains the known molecular mechanisms of therapy resistance in CSCs as reliable and clinically predictive markers that could enable the use of new targeted antitumor therapy in the sense of personalized medicine.     

The intrinsic immunogenic properties of cancer cell lines,immunogenic cell death,and how these influence host antitumor immune responses

Modern cancer therapies often involve the combination of tumor-directed cytotoxic strategies and generation of a host antitumor immune response. The latter is unleashed by immunotherapies that activate the immune system generating a more immunostimulatory tumor microenvironment and a stronger tumor antigen-specific immune response. Studying the interaction between antitumor cytotoxic therapies, dying cancer cells, and the innate and adaptive immune system requires appropriate experimental tumor models in mice. In this review, we discuss the immunostimulatory and immunosuppressive properties of cancer cell lines commonly used in immunogenic cell death (ICD) studies being apoptosis or necroptosis. We will especially focus on the antigenic component of immunogenicity. While in several cancer cell lines the epitopes of endogenously expressed tumor antigens are known, these intrinsic epitopes are rarely determined in experimental apoptotic or necroptotic ICD settings. Instead by far the most ICD research studies investigate the antigenic response against exogenously expressed model antigens such as ovalbumin or retroviral epitopes (e.g., AH1). In this review, we will argue that the immune response against endogenous tumor antigens and the immunopeptidome profile of cancer cell lines affect the eventual biological readouts in the typical prophylactic tumor vaccination type of experiments used in ICD research, and we will propose additional methods involving immunopeptidome profiling, major histocompatibility complex molecule expression, and identification of tumor-infiltrating immune cells to document intrinsic immunogenicity following different cell death modalities.Subject terms: Cancer models, Antigen-presenting cells, Immune cell death     

Tumor vaccine: current trends in antigen specific immunotherapy

Effective cancer treatment to prevent the tumor growth as well as to stop its recurrence is the dream of oncologists. Currently available therapeutic measures like, radiotherapy and chemotherapy, often suffer from severe toxicity and lack of specificity of the drug towards tumor cells. Another promising approach is the 'immunotherapy', in which either the immune system is activated by tumor vaccine to combat the tumor growth or antitumor antibodies can be used. Vaccination can stimulate humoral, cellular and innate immune systems to generate various effector molecules, like antibody, cytotoxic T cells, cytokines etc. In antigen specific immunotherapy, the immune system can be stimulated actively by antigen based tumor vaccine to kill only those tumor cells, having expression of the particular tumor associated antigen. Different experimental, preclinical and clinical studies have proved that generated immune responses are effective to restrict the tumor growth. Useful strategies of antigen specific immunotherapy and outcome of various laboratory and clinic based studies are discussed.     

自然杀伤细胞参与肝脏恶性肿瘤免疫逃逸研究进展

自然杀伤细胞是机体固有免疫系统重要组成部分,在肝脏等免疫器官中含量丰富,而且免疫表型、功能等表现出器官特异性。在正常情况下,靶细胞表面的配体与自然杀伤细胞表面的活化性受体直接结合并释放细胞毒性物质,诱导活化靶细胞凋亡程序,从而发挥抗感染、抗肿瘤作用。然而肿瘤细胞仍能够通过多种途径逃逸机体的免疫监视功能,研究认为肿瘤细胞抗原异常表达、肿瘤微环境中细胞因子及其他免疫细胞相互作用等因素所引起的自然杀伤细胞活性降低对于诱导肿瘤免疫逃逸起重要作用。本文综述了自然杀伤细胞在肝脏恶性肿瘤发生过程中参与免疫逃逸的机制及研究进展,以期为临床抗肿瘤免疫治疗的研究提供参考。     

T cell-mediated help against tumors

Adoptive transfer of tumor antigen-specific T helper (Th) cells is a surprisingly potent anti-tumor therapy. Even in RIP1-Tag2 mice with a rapidly growing, aggressive endogenous beta cell tumor Th can significantly extend life time and are more efficient than any other therapy studied. The therapeutic effect of Th cells seems to be independent of tumor cell destruction. It critically relies on three principles: (i) inhibition of tumor angiogenesis, (ii) inhibition of beta cell proliferation, and (iii) induction of tumor dormancy. As tumor cell destruction by cytotoxic CD8+ T cells (CTL) largely failed in tumor therapy, induction of tumor dormancy by Th cell-mediated immune responses represents a novel therapeutic option that may be combined with other cytotoxic regimens, e. g. radio- and/or chemotherapy, as it is established for bone marrow transplantation. Importantly, Th cell efficacy strictly requires interferon-gamma (IFN-gamma) signaling, and, in the absence of IFN-gamma, Th cells may even worsen tumor diseases. Therefore, using the immune system to control tumor dormancy represents a novel approach, especially as therapy of tumors resistant to conventional therapies. Yet, it is important to underline that Th cell-based antitumor effects critically depend on a functional cytokine network, especially appropriate IFN-gamma signaling.     

Type I interferon-mediated pathway interacts with peroxisome proliferator activated receptor-γ (PPAR-γ): At the cross-road of pancreatic cancer cell proliferation

Pancreatic adenocarcinoma remains an unresolved therapeutic challenge because of its intrinsically refractoriness to both chemo- and radiotherapy due to the complexity of signaling and the activation of survival pathways in cancer cells. Recent studies have demonstrated that the combination of some drugs, targeting most of aberrant pathways crucial for the survival of pancreatic cancer cells may be a valid antitumor strategy for this cancer. Type I interferons (IFNs) may have a role in the pathogenesis and progression of pancreatic adenocarcinoma, but the limit of their clinical use is due to the activation of tumor resistance mechanisms, including JAK-2/STAT-3 pathway. Moreover, aberrant constitutive activation of STAT-3 proteins has been frequently detected in pancreatic adenocarcinoma. The selective targeting of these cell survival cascades could be a promising strategy in order to enhance the antitumor effects of type I IFNs. The activation of peroxisome proliferator-activated receptor γ (PPAR-γ), on the other hand, has a suppressive activity on STAT-3. In fact, PPAR-γ agonists negatively modulate STAT-3 through direct and/or indirect mechanisms in several normal and cancer models. This review provides an overview on the current knowledge about the molecular mechanisms and antitumor activity of these two promising classes of drugs for pancreatic cancer therapy. Finally, the synergistic antiproliferative activity of combined IFN-β and troglitazone treatment on pancreatic cancer cell lines, evaluated in vitro, and the consequent potential clinical applications will be discussed.     

Antitumor immunity and cellular cancer therapies

The identification of tumor specific antigens has provided important advance in tumor immunology. It is now established that specific cytotoxic T lymphocytes (CTL) and natural killer cells infiltrate tumor tissues and are effector cells able to control tumor growth. However, such a natural antitumor immunity has limited effects in cancer patients. Failure of host defenses against tumor is consecutive to several mechanisms which are becoming targets to design new immunotherapeutic approaches. CTL are critical components of the immune response to human tumors and induction of strong CTL responses is the goal of most current vaccine strategies. Effectiveness of cytokine therapy, cancer vaccines and injection of cells improving cellular immunity have been established in tumor grafted murine models. Clinical trials are underway. To day, interest is particularly focused on cell therapy: injected cells are either "ready to use" effector cells (lymphocytes) or antigen presenting cells able to induce a protective immune reaction in vivo (dendritic cells). The challenge ahead lie in the careful optimization of the most promising strategies in clinical situation.     

Lipoplexes prepared from cationic liposomes and mammalian DNA induce CpG-independent, direct cytotoxic effects in cell cultures and in mice

BACKGROUND: Recent studies demonstrated the cytotoxic activity of bacterial DNA (pDNA) complexed with cationic lipids. This cytotoxicity is related to the ability of pDNA to induce potently the immune system, which is associated with release of inflammatory cytokines. Both activities seem to be related to the nonmethylated CpG sequences present in the pDNA. Here we study the cytotoxic activity of nonbacterial DNA complexed with cationic lipids against various tumor cell lines. METHODS: Various nucleic acids complexed with cationic liposomes were prepared and their cytotoxic activity was studied in cell cultures and in tumor-bearing mice. Cell uptake of lipoplexes was evaluated, and mechanism of DNA cytotoxic activity was studied. RESULTS: We found that nonbacterial (vertebrate) genomic DNA when complexed with cationic lipids is highly cytotoxic against C-26 and M-109 tumor cells. Cationic lipids alone were not toxic to these cells. The cytotoxic activity does not result from nonspecific acidification of the intracellular milieu, as substitution of DNA by poly-L-glutamate did not result in cytotoxicity, although the level of uptake of anionic charges per cell was similar to that of the nucleic acids, suggesting that this cytotoxic effect is specific to nucleic acids. By studying the nucleic acid fate using confocal microscopy, we found that cytotoxicity correlated with the release of DNA into the cytoplasm following uptake of lipoplexes. Injection of calf thymus DNA-based lipoplexes to mice with peritoneal C-26 metastases resulted in doubling of median survival time and long-term survival in 20% of the tumor-bearing mice. Judging by low levels of IFN-gamma, TNF-alpha and IL-6 in the treated mice, this effect cannot be ascribed to Th-1 inflammation, but rather to a direct cytotoxic effect on the tumor cells. CONCLUSIONS: The above data provide a new insight into the mechanisms of lipoplex-mediated antitumor effects in vitro and in vivo and new perspectives in cancer therapy.     

Idiotype vaccination against murine B cell lymphoma. Humoral and cellular requirements for the full expression of antitumor immunity

The roles of humoral and cellular antitumor immune responses induced by immunization with tumor-derived idiotypic IgM were studied in a syngeneic, transplantable B cell lymphoma (38C13) of C3H mice. Id vaccination with keyhole limpet hemocyanin-conjugated Id induced protection against a subsequent lethal tumor challenge. Such immunizations elicited anti-idiotypic antibodies that were cytotoxic in in vitro antibody-dependent cellular cytotoxicity assays as well as in vivo passive transfer experiments. L3T4+ T cells, which proliferated in vitro in response to the specific Id protein, were also induced. However, cells mediating direct cytotoxicity, either in vitro or in vivo, were not observed in the lymph nodes, spleens, or peritoneal cavity of immune mice or at the site of tumor regression as demonstrated by using a tumor sponge implantation model. In addition, in vitro sensitization of immune lymphocytes against 38C13 tumor cells failed to induce cytotoxicity. Immunization with lipid conjugated Id also elicited a T cell proliferative response but failed to induce anti-idiotypic antibodies and did not confer resistance to tumor growth. These results suggest that anti-idiotypic antibodies play the major role in the destruction of 38C13 tumor cells. However, in vivo depletion of L3T4+ or Lyt-2+ cells from 38C-Id-keyhole limpet hemocyanin-immunized mice resulted in diminished protection against a tumor challenge. Thus, although humoral responses appear to play the predominant part in tumor destruction, cellular responses are also required for the full expression of antitumor immunity in this system.