The roles of mast cells in anticancer immunity

The tumor microenvironment (TME), which is composed of stromal cells such as endothelial cells, fibroblasts, and immune cells, provides a supportive niche promoting the growth and invasion of tumors. The TME also raises an immunosuppressive barrier to effective antitumor immune responses and is therefore emerging as a target for cancer immunotherapies. Mast cells (MCs) accumulate in the TME at early stages, and their presence in the TME is associated with poor prognosis in many aggressive human cancers. Some well-established roles of MCs in cancer are promoting angiogenesis and tumor invasion into surrounding tissues. Several mouse models of inducible and spontaneous cancer show that MCs are among the first immune cells to accumulate within and shape the TME. Although MCs and other suppressive myeloid cells are associated with poor prognosis in human cancers, high densities of intratumoral T effector (T(eff)) cells are associated with a favorable prognosis. The latter finding has stimulated interest in developing therapies to increase intratumoral T cell density. However, cellular and molecular mechanisms promoting high densities of intratumoral T(eff) cells within the TME are poorly understood. New evidence suggests that MCs are essential for shaping the immune-suppressive TME and impairing both antitumor T(eff) cell responses and intratumoral T cell accumulation. These roles for MCs warrant further elucidation in order to improve antitumor immunity. Here, we will summarize clinical studies of the prognostic significance of MCs within the TME in human cancers, as well as studies in mouse models of cancer that reveal how MCs are recruited to the TME and how MCs facilitate tumor growth. Also, we will summarize our recent studies indicating that MCs impair generation of protective antitumor T cell responses and accumulation of intratumoral T(eff) cells. We will also highlight some approaches to target MCs in the TME in order to unleash antitumor cytotoxicity.     

Successful colon cancer eradication after chemoimmunotherapy is associated with profound phenotypic change of intratumoral myeloid cells

IL-12 is a potent immunostimulatory cytokine, but its impact as an antitumor drug in clinical practice is limited. Upsurge of regulatory T cells (Treg) in the tumor milieu has been proposed to limit the efficacy of the treatment. In this paper, two drugs (cyclophosphamide [CPA] and anti-CD25 mAb) widely used to eliminate Treg were used in an attempt to enhance the antitumor effect of IL-12 gene therapy. Both anti-CD25 and CPA combined with IL-12 were able to deplete intratumoral Treg and myeloid-derived suppressor cells (MDSC), but only IL-12 plus CPA achieved significant antitumor activity in mice with large established s.c. colon carcinoma. This therapeutic effect was associated with the emergence of a heterogeneous population of myeloid cells within the tumor, termed inflammatory myeloid cells (IMC), composed of Ly6C(high)Ly6G(low) inflammatory monocytes and Ly6G(high)Ly6C(+) neutrophils. IMC showed a distinctive pattern of cytokine/chemokine production, and in contrast to MDSC, they did not induce conversion of naive CD4(+) T cells into Treg. The appearance of IMC coincided with intense tumor infiltration by effector T cells, which was abrogated by elimination of IMC by anti-Gr1 mAb, a maneuver that abolished the antitumor effect of the therapy. Therefore, the combination of IL-12 and CPA eliminates intratumoral Treg and MDSC, while it induces the appearance of IMC within the tumor microenvironment. The latter effect is essential to facilitate effector T cell infiltration and subsequent tumor elimination.     

Locoregional therapy with polyethylene-glycol-modified interleukin-2 of an intradermally growing hepatocellular carcinoma in the guinea pig induces T-cell-mediated antitumor activity

Therapy with repeated intratumoral and perilymphatic administration of relatively low doses of polyethylene-glycol(PEG)-modified interleukin-2 (IL-2) in the syngeneic guinea pig line 10 (L10) hepatocarcinoma results in significant local tumor growth inhibition and a delay in development of regional lymph node metastases of more than 3 weeks when compared to controls. Occasionally animals are cured of tumor. The mechanism of this antitumor activity was studied. The antitumor activity of locoregionally administered PEG-IL-2 was abrogated by pretreatment with polyclonal anti-thymocyte serum, indicating that the observed tumor growth inhibition was a T-cell-mediated phenomenon. Besides the locoregional tumor growth inhibition, a systemic effect was recorded as the growth of a second tumor cell inoculum at the contralateral side was inhibited as well. Furthermore, those animals cured after PEG-IL-2 therapy developed specific immunity against the L10 tumor and this immunity could be transferred to naive animals by spleen cells. Immunohistological observations of the tumor site revealed a slight increase of helper and cytotoxic T cell subpopulations after PEG-IL-2 therapy. More pronounced, however, was the rise in number of eosinophilic granulocytes present in the stroma surrounding the tumor cells. Involvement of cytotoxic cells in the antitumor effects of PEG-IL-2 could not be demonstrated: regional lymph node cells and spleen cells obtained immediately after therapy (day 15) or on day 21 showed no cytotoxic activity in vitro against L10, K562, Daudi and line 1 (L1) target cells.In conclusion, locoregional therapy with PEG-IL-2 induced a systemic T-cell-mediated antitumor response. As no cytotoxic T cell activity was measured, however, the underlying mechanism is most likely a T-helper response. Eosinophils at the tumor site may be tumoricidal but further experiments must reveal the role of these cells in the PEG-IL-2-induced tumor regression.     

The role of dendritic cells in tumor microenvironments and their uses as therapeutic targets

Dendritic cells (DC), which consist of several different subsets, specialize in antigen presentation and are critical for mediating the innate and adaptive immune responses. DC subsets can be classified into conventional, plasmacytoid, and monocyte-derived DC in the tumor microenvironment, and each subset plays a different role. Because of the role of intratumoral DCs in initiating antitumor immune responses with tumor-derived antigen presentation to T cells, DCs have been targeted in the treatment of cancer. By regulating the functionality of DCs, several DC-based immunotherapies have been developed, including administration of tumor-derived antigens and DC vaccines. In addition, DCs participate in the mechanisms of classical cancer therapies, such as radiation therapy and chemotherapy. Thus, regulating DCs is also important in improving current cancer therapies. Here, we will discuss the role of each DC subset in antitumor immune responses, and the current status of DC-related cancer therapies.     

A Multifunctional Drug Combination Shows Highly Potent Therapeutic Efficacy against Human Cancer Xenografts in Athymic Mice

The tumor microenvironment plays a crucial role during tumor development. Integrated combination of drugs that target tumor microenvironment is a promising approach to anticancer therapy. Here, we report a multifunctional combination of low-cytotoxic drugs composed of dipyridamole, bestatin and dexamethasone (DBDx) which mainly acts on the tumor microenvironment shows highly potent antitumor efficacy in vivo. In mouse hepatoma H22 model, the triple drug combination showed synergistic and highly potent antitumor efficacy. The combination indices of various combinations of the triple drugs were between 0.2 and 0.5. DBDx inhibited the growth of a panel of human tumor xenografts and showed no obvious systemic toxicity. At tolerated doses, DBDx suppressed the growth of human hepatocellular carcinoma BEL-7402, HepG2, and lung adenocarcinoma A549 xenografts by 94.5%, 93.7% and 96.9%, respectively. Clonogenic assay demonstrated that DBDx showed weak cytotoxicity. Western blot showed that Flk1 and Nos3 were down-regulated in the DBDx-treated group. Proteomic analysis showed that DBDx mainly affected the metabolic process and immune system process; in addition, the angiogenesis and VEGF signaling pathway were also affected. Conclusively, DBDx, a multifunctional drug combination of three low-cytotoxic drugs, shows synergistic and highly potent antitumor efficacy evidently mediated by the modulation of tumor microenvironment. Based on its low-cytotoxic attributes and its broad-spectrum antitumor therapeutic efficacy, this multifunctional combination might be useful in the treatment of cancers, especially those refractory to conventional chemotherapeutics.     

Chemoimmunotherapy with doxorubicin and caffeine combination enhanced ICD induction and T-cell infiltration in B16F10 melanoma tumors

Majority of chemotherapeutic agents can elicit antitumor immunity and modulate the composition, density, function, and distribution of tumor infiltrating lymphocytes (TILs), to influence differential therapeutic responses and prognosis in cancer patients. The clinical success of these agents, particularly anthracyclines like doxorubicin, not only depends on their cytotoxic activity but also by the enhancement of pre-existing immunity primarily through induction of immunogenic cell death (ICD). However, resistance for the induction of ICD either intrinsic or acquired is a major hurdle for most of these drugs. To enhance ICD by these agents, it has become clear that blockade of adenosine production or its signaling need to be specifically targeted as they represent highly resistant mechanisms. Given the prominent role of adenosine mediated immunosuppression and resistance to ICD induction in tumor microenvironment, combination strategies that involve ICD induction and adenosine signaling blockade are further warranted. In the present study, we investigated the antitumor effect of caffeine and doxorubicin combination therapy against 3-MCA-induced and cell-line induced tumors in mice. Our results demonstrated significant tumor growth inhibition by the combination therapy of doxorubicin and caffeine against both carcinogen-induced and cell-line induced tumor models. In addition, significant T-cell infiltration and enhanced ICD induction evidenced by increased intratumoral calreticulin and HMGB1 levels, was observed in B16F10 melanoma mice. The possible mechanism behind the observed antitumor activity might be due to the enhanced ICD induction and subsequent T-cell infiltration by the combination therapy. To prevent the development of resistance and to enhance the antitumor activity of ICD inducing drugs like doxorubicin, combination with adenosine-A2A receptor pathway inhibitors like caffeine might be a potential strategy.     

Oncolytic Adenovirus Expressing IL-23 and p35 Elicits IFN-γ- and TNF-α-Co-Producing T Cell-Mediated Antitumor Immunity

Cytokine immunogene therapy is a promising strategy for cancer treatment. Interleukin (IL)-12 boosts potent antitumor immunity by inducing T helper 1 cell differentiation and stimulating cytotoxic T lymphocyte and natural killer cell cytotoxicity. IL-23 has been proposed to have similar but not overlapping functions with IL-12 in inducing Th1 cell differentiation and antitumor immunity. However, the therapeutic effects of intratumoral co-expression of IL-12 and IL-23 in a cancer model have yet to be investigated. Therefore, we investigated for the first time an effective cancer immunogene therapy of syngeneic tumors via intratumoral inoculation of oncolytic adenovirus co-expressing IL-23 and p35, RdB/IL23/p35. Intratumoral administration of RdB/IL23/p35 elicited strong antitumor effects and increased survival in a murine B16-F10 syngeneic tumor model. The levels of IL-12, IL-23, interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α) were elevated in RdB/IL23/p35-treated tumors. Moreover, the proportion of regulatory T cells was markedly decreased in mice treated with RdB/IL23/p35. Consistent with these data, mice injected with RdB/IL23/p35 showed massive infiltration of CD4⁺ and CD8⁺ T cells into the tumor as well as enhanced induction of tumor-specific immunity. Importantly, therapeutic mechanism of antitumor immunity mediated by RdB/IL23/p35 is associated with the generation and recruitment of IFN-γ- and TNF-α-co-producing T cells in tumor microenvironment. These results provide a new insight into therapeutic mechanisms of IL-12 plus IL-23 and provide a potential clinical cancer immunotherapeutic agent for improved antitumor immunity.     

Delivery of dendritic cells engineered to secrete IFN-alpha into central nervous system tumors enhances the efficacy of peripheral tumor cell vaccines: dependence on apoptotic pathways

We tested whether modulation of the CNS-tumor microenvironment by delivery of IFN-alpha-transduced dendritic cells (DCs: DC-IFN-alpha) would enhance the therapeutic efficacy of peripheral vaccinations with cytokine-gene transduced tumor cells. Mice bearing intracranial GL261 glioma or MCA205 sarcoma received peripheral immunizations with corresponding irradiated tumor cells engineered to express IL-4 or GM-CSFs, respectively, as well as intratumoral delivery of DC-IFN-alpha. This regimen prolonged survival of the animals and induced tumor-specific CTLs that expressed TRAIL, which in concert with perforin and Fas ligand (FasL) was involved in the tumor-specific CTL activity of these cells. The in vivo antitumor activity associated with this approach was abrogated by administration of neutralizing mAbs against TRAIL or FasL and was not observed in perforin-/-, IFN-gamma-/-, or FasL-/- mice. Transduction of the tumor cells with antiapoptotic protein cellular FLIP rendered the gene-modified cells resistant to TRAIL- or FasL-mediated apoptosis and to CTL killing activity in vitro. Furthermore, the combination therapeutic regimen was ineffective in an intracranial cellular FLIP-transduced MCA205 brain tumor model. These results suggest that the combination of intratumoral delivery of DC-IFN-alpha and peripheral immunization with cytokine-gene transduced tumor cells may be an effective therapy for brain tumors that are sensitive to apoptotic signaling pathways.     

Continuous delivery of IFN-beta promotes sustained maturation of intratumoral vasculature

IFNs have pleiotropic antitumor mechanisms of action. The purpose of this study was to further investigate the effects of IFN-beta on the vasculature of human xenografts in immunodeficient mice. We found that continuous, systemic IFN-beta delivery, established with liver-targeted adeno-associated virus vectors, led to sustained morphologic and functional changes of the tumor vasculature that were consistent with vessel maturation. These changes included increased smooth muscle cell coverage of tumor vessels, improved intratumoral blood flow, and decreased vessel permeability, tumor interstitial pressure, and intratumoral hypoxia. Although these changes in the tumor vasculature resulted in more efficient tumor perfusion, further tumor growth was restricted, as the mature vasculature seemed to be unable to expand to support further tumor growth. In addition, maturation of the intratumoral vasculature resulted in increased intratumoral penetration of systemically administered chemotherapy. Finally, molecular analysis revealed increased expression by treated tumors of angiopoietin-1, a cytokine known to promote vessel stabilization. Induction of angiopoietin-1 expression in response to IFN-beta was broadly observed in different tumor lines but not in those with defects in IFN signaling. In addition, IFN-beta-mediated vascular changes were prevented when angiopoietin signaling was blocked with a decoy receptor. Thus, we have identified an alternative approach for achieving sustained vascular remodeling-continuous delivery of IFN-beta. In addition to restricting tumor growth by inhibiting further angiogenesis, maturation of the tumor vasculature also improved the efficiency of delivery of adjuvant therapy. These results have significant implications for the planning of combination anticancer therapy.     

Intratumoral bacteria are an important “accomplice” in tumor development and metastasis

As emerging tumor components, intratumoral bacteria have been found in many solid tumors. Several studies have demonstrated that different cancer subtypes have distinct microbial compositions, and mechanistic studies have shown that intratumoral bacteria may promote cancer initiation and progression through DNA damage, epigenetic modification, inflammatory responses, modulation of host immunity and activation of oncogenes or oncogenic pathways. Moreover, intratumoral bacteria have been shown to modulate tumor metastasis and chemotherapy response. A better understanding of the tumor microenvironment and its associated microbiota will facilitate the design of new metabolically engineered species, opening up a new era of intratumoral bacteria-based cancer therapy. However, many questions remain to be resolved, such as where intratumoral bacteria originate and whether there is a direct causal relationship between intratumoral bacteria and tumor susceptibility. In addition, suitable preclinical models and more advanced detection techniques are crucial for studying the biological functions of intratumoral bacteria. In this review, we summarize the complicated role of intratumoral bacteria in the regulation of cancer development and metastasis and discuss their carcinogenic mechanisms and potential therapeutic aspects.     

The next‐generation BET inhibitor,PLX51107, delays melanoma growth in a CD8‐mediated manner

Epigenetic agents such as bromodomain and extra‐terminal region inhibitors (BETi) slow tumor growth via tumor intrinsic alterations; however, their effects on antitumor immunity remain unclear. A recent advance is the development of next‐generation BETi that are potent and display a favorable half‐life. Here, we tested the BETi, PLX51107, for immune‐based effects on tumor growth in BRAF V600E melanoma syngeneic models. PLX51107 delayed melanoma tumor growth and increased activated, proliferating, and functional CD8+ T cells in tumors leading to CD8+ T‐cell‐mediated tumor growth delay. PLX51107 decreased Cox2 expression, increased dendritic cells, and lowered PD‐L1, FasL, and IDO‐1 expression in the tumor microenvironment. Importantly, PLX51107 delayed the growth of tumors that progressed on anti‐PD‐1 therapy; a response associated with decreased Cox2 levels, decreased PD‐L1 expression on non‐immune cells, and increased intratumoral CD8+ T cells. Thus, next‐generation BETi represent a potential first‐line and secondary treatment strategy for metastatic melanoma by eliciting effects, at least in part, on antitumor CD8+ T cells.     

Intratumoral interleukin-2 immunotherapy: Activation of tumor-infiltrating and splenic lymphocytes in vivo

Direct intratumoral injection of interleukin-2 (IL-2) was evaluated in a murine model. Balb/c mice received 5 × 10⁴ Line 1 alveolar carcinoma cells (L1C2) by subcutaneous injection. On the third day following tumor implantation, mice received injections of IL-2 (5 × 10³–5 × 10⁴ units) or diluent twice daily, either by i. p. or intratumoral injection, 5 days/week for 3 weeks. Intratumoral injection of 5 × 10⁴ units IL-2 significantly reduced tumor volume (P <0.05 versus control), increased median survival time (P = 0.0001), and resulted in a 23.5% cure rate (P = 0.008). There were no long-term survivors in the other treatment groups. Both tumor-infiltrating lymphocytes (TIL) and splenic lymphocytes isolated directly from IL-2-treated mice demonstrated enhanced cytolytic activity compared to diluent-treated controls. To determine whether non-T-cell-mediated antitumor responses were active in our model, intratumoral immunotherapy was evaluated in athymic Balb/cnu/nu mice. In order to decrease the recruitment of lymphocyte precursors, nude mice were splenectomized and received cyclophosphamide prior to tumor injection and IL-2 therapy. Intratumoral IL-2 immunotherapy also significantly decreased tumor volume in these immunodeficient mice (P <0.02), but did not lead to long-term survival. We conclude that both TIL and splenic lymphocytes are activated in vivo in response to intratumoral IL-2 immunotherapy, suggesting that intratumoral therapy with IL-2 activates both local and systemic antitumor responses.Supported by the Tobacco-Related Disease Research Program of the University of California, the Cancer Research Coordinating Committee, the Jonsson Cancer Center Foundation, and Veterans Administration Medical Research Funds     

Intratumoral CC chemokine ligand 5 overexpression delays tumor growth and increases tumor cell infiltration

Chemokines participate in the antitumor immune response by regulating the movement and positioning of lymphocytes as well as effector functions and may thus be candidates for use in antitumor therapy. To test whether CCL5, a chemokine involved in the recruitment of a wide spectrum of immunocompetent cells, can control tumor growth, we forced its expression at mouse tumor sites. Tumor growth was reduced in mice with s.c. syngeneic CCL5-EL-4 compared with EL-4-injected mice, whereas both reduced tumor growth and incidence were observed in mice with OVA-expressing EG-7 transfected with CCL5 compared with EG-7-injected mice. Significant antitumor effects were observed soon after intratumoral injection of DNA plasmid coding for chimeric CCL5-Ig. Importantly, quantitative RT-PCR assays showed that the amount of CCL5 expression at the tumor site determined the effectiveness of the antitumor response, which was associated with infiltration of increased numbers of NK, CD4, and CD8 cells at the tumor site. This effect was lost in mice deficient for T/B lymphocytes (RAG-2 knockout) or for CCR5 (CCR5 knockout). Together, these data demonstrate the antitumor activity of intratumoral CCL5 overexpression, due to its recruitment of immunocompetent cells, and the potential usefulness of chimeric CCL5-Ig DNA as an agent in cancer therapy.     

Immune Adjuvant Activity of Pre-Resectional Radiofrequency Ablation Protects against Local and Systemic Recurrence in Aggressive Murine Colorectal Cancer

Purpose

While surgical resection is a cornerstone of cancer treatment, local and distant recurrences continue to adversely affect outcome in a significant proportion of patients. Evidence that an alternative debulking strategy involving radiofrequency ablation (RFA) induces antitumor immunity prompted the current investigation of the efficacy of performing RFA prior to surgical resection (pre-resectional RFA) in a preclinical mouse model.

Experimental Design

Therapeutic efficacy and systemic immune responses were assessed following pre-resectional RFA treatment of murine CT26 colon adenocarcinoma.

Results

Treatment with pre-resectional RFA significantly delayed tumor growth and improved overall survival compared to sham surgery, RFA, or resection alone. Mice in the pre-resectional RFA group that achieved a complete response demonstrated durable antitumor immunity upon tumor re-challenge. Failure to achieve a therapeutic benefit in immunodeficient mice confirmed that tumor control by pre-resectional RFA depends on an intact adaptive immune response rather than changes in physical parameters that make ablated tumors more amenable to a complete surgical excision. RFA causes a marked increase in intratumoral CD8⁺ T lymphocyte infiltration, thus substantially enhancing the ratio of CD8⁺ effector T cells: FoxP3⁺ regulatory T cells. Importantly, pre-resectional RFA significantly increases the number of antigen-specific CD8⁺ T cells within the tumor microenvironment and tumor-draining lymph node but had no impact on infiltration by myeloid-derived suppressor cells, M1 macrophages or M2 macrophages at tumor sites or in peripheral lymphoid organs (i.e., spleen). Finally, pre-resectional RFA of primary tumors delayed growth of distant tumors through a mechanism that depends on systemic CD8⁺ T cell-mediated antitumor immunity.

Conclusion

Improved survival and antitumor systemic immunity elicited by pre-resectional RFA support the translational potential of this neoadjuvant treatment for cancer patients with high-risk of local and systemic recurrence.     

Intratumoral immunocytokine treatment results in enhanced antitumor effects

Immunocytokines (IC), consisting of tumor-specific monoclonal antibodies fused to the immunostimulatory cytokine interleukin 2 (IL2), exert significant antitumor effects in several murine tumor models. We investigated whether intratumoral (IT) administration of IC provided enhanced antitumor effects against subcutaneous tumors. Three unique ICs (huKS-IL2, hu14.18-IL2, and GcT84.66-IL2) were administered systemically or IT to evaluate their antitumor effects against tumors expressing the appropriate IC-targeted tumor antigens. The effect of IT injection of the primary tumor on a distant tumor was also evaluated. Here, we show that IT injection of IC resulted in enhanced antitumor effects against B16-KSA melanoma, NXS2 neuroblastoma, and human M21 melanoma xenografts when compared to intravenous (IV) IC injection. Resolution of both primary and distant subcutaneous tumors and a tumor-specific memory response were demonstrated following IT treatment in immunocompetent mice bearing NXS2 tumors. The IT effect of huKS-IL2 IC was antigen-specific, enhanced compared to IL2 alone, and dose-dependent. Hu14.18-IL2 also showed greater IT effects than IL2 alone. The antitumor effect of IT IC did not always require T cells since IT IC induced antitumor effects against tumors in both SCID and nude mice. Localization studies using radiolabeled ¹¹¹In-GcT84.66-IL2 IC confirmed that IT injection resulted in a higher concentration of IC at the tumor site than IV administration. In conclusion, we suggest that IT IC is more effective than IV administration against palpable tumors. Further testing is required to determine how to potentially incorporate IT administration of IC into an antitumor regimen that optimizes local and systemic anticancer therapy.     

Gene-based delivery of immune-activating cytokines for cancer treatment

Tumors evolve together with the tumor microenvironment (TME) and reshape it towards immunosuppression. Immunostimulating cytokines can be used to revert this state leading to effective antitumor immune responses, but their exploitation as anticancer drugs has been hampered by severe toxicity associated with systemic administration. Local, TME-targeted delivery of immune activating cytokines can deploy their antitumoral function more effectively than systemic administration while, at the same time, avoiding exposure of healthy organs and limiting toxicity. Here, we review different gene and cell therapy platforms developed for tumor-directed cytokine delivery highlighting their potential for clinical translation.     

Intratumoral injection of therapeutic HPV vaccinia vaccine following cisplatin enhances HPV-specific antitumor effects

Despite the conventional treatments of radiation therapy and chemotherapy, the 5-year survival rates for patients with advanced-stage cervical cancers remain low. Cancer immunotherapy has emerged as an alternative, innovative therapy that may improve survival. Here, we utilize a preclinical HPV-16 E6/E7-expressing tumor model, TC-1, and employ the chemotherapeutic agent cisplatin to generate an accumulation of CD11c+ dendritic cells in tumor loci making it an ideal location for the administration of therapeutic vaccines. Following cisplatin treatment, we tested different routes of administration of a therapeutic HPV vaccinia vaccine encoding HPV-16 E7 antigen (CRT/E7-VV). We found that TC-1 tumor-bearing C57BL/6 mice treated with cisplatin and intratumoral injection of CRT/E7-VV significantly increased E7-specific CD8+ T cells in the blood and generated potent local and systemic antitumor immune responses compared to mice receiving cisplatin and CRT/E7-VV intraperitoneally or mice treated with cisplatin alone. We further extended our study using a clinical grade recombinant vaccinia vaccine encoding HPV-16/18 E6/E7 antigens (TA-HPV). We found that intratumoral injection with TA-HPV following cisplatin treatment also led to increased E7-specific CD8+ T cells in the blood as well as significantly decreased tumor size compared to intratumoral injection with wild type vaccinia virus. Our study has strong implications for future clinical translation using intratumoral injection of TA-HPV in conjunction with the current treatment strategies for patients with advanced cervical cancer.     

In vivo tumor delivery of a recombinant single chain Fv::tumor necrosis factor-alpha fusion [correction of factor: a fusion] protein.

Locoregional and intratumoral administration of tumor necrosis factor alpha (TNF alpha) has been successful in obtaining inhibition or regression of tumor growth in the clinic. This potent antitumor activity of TNF alpha has not yet been exploited as a systemic agent in cancer therapy, mainly due to high levels of toxicity to normal tissues before a therapeutic dose of TNF alpha in the tumor has been achieved. To address this, we have targeted TNF alpha using antitumor antibodies. We have used a genetic fusion of human recombinant TNF alpha with MFE-23, a single-chain Fv antibody fragment directed against carcinoembryonic antigen. MFE-23::TNF alpha fusion protein is isolated in high yields (28 mg/L) from bacterial inclusion bodies and purified to homogeneity by affinity chromatography. It is a 144 kDa trimer in native form and possesses the antigen-binding activity of the sFv and the cytotoxicity to both WEHI 164 and a human adenocarcinoma cell line (LoVo) of rhTNF alpha. Radiolabeled MFE-23::TNF alpha binds both human and mouse TNF receptor 1 in vitro and is able to localize effectively in nude (nu/nu) mice bearing human LS174T xenografts; tumor/tissue ratios of 21:1 and 60:1 are achieved 24 and 48 h after intravenous injection. These studies indicate that MFE-23::TNF alpha will provide an effective means for systemically administered cancer therapy with TNF alpha.     

Blockade of programmed death-1 pathway rescues the effector function of tumor-infiltrating T cells and enhances the antitumor efficacy of lentivector immunization

Despite intensive effort, the antitumor efficacy of tumor vaccines remains limited in treating established tumors regardless of the potent systemic tumor-specific immune response and the increases of tumor infiltration of T effector cells. In the current study, we demonstrated that although lentivector (lv) immunization markedly increased Ag-dependent tumor infiltration of CD8 and CD4 T cells and generated Ag-specific antitumor effect, it simultaneously increased the absolute number of myeloid-derived suppressor cells and regulatory T cells in the tumor lesions. In addition, lv immunization induced expression of programmed death-ligand 1 in the tumor lesions. Furthermore, the tumor-infiltrating CD8 T cells expressed high levels of programmed death-1 and were partially dysfunctional, producing lower amounts of effector cytokines and possessing a reduced cytotoxicity. Together, these immune-suppression mechanisms in the tumor microenvironment pose a major obstacle to effective tumor immunotherapy and may explain the limited antitumor efficacy of lv immunization. The loss of effector function in the tumor microenvironment is reversible, and the effector function of CD8 T cells in the tumor could be partially rescued by blocking programmed death-1 and programmed death-ligand 1 pathway in vitro and in vivo, resulting in enhanced antitumor efficacy of lv immunization. These data suggest that immunization alone may exacerbate immune suppression in the tumor lesions and that methods to improve the tumor microenvironment and to rescue the effector functions of tumor-infiltrating T cells should be incorporated into immunization strategies to achieve enhanced antitumor efficacy.     

肿瘤相关巨噬细胞：在肿瘤演进中的作用及潜在抗肿瘤靶点

炎症是公认的肿瘤十大特征之一,而肿瘤相关巨噬细胞是肿瘤微环境的重要组成部分,它影响肿瘤的生长、血管生成、免疫抑制、 转移和药物抗性。最新研究表明,肿瘤相关巨噬细胞还会影响抗肿瘤治疗的临床疗效。鉴于肿瘤相关巨噬细胞在肿瘤演进中起重要作用, 其作为潜在抗肿瘤靶点备受关注。基于最新的研究,对人类癌症中肿瘤相关巨噬细胞的主要功能、作用和特征以及用作新兴肿瘤治疗干预 靶点作一综述。