Imaging aspects of the tumor stroma with therapeutic implications

Cancer cells rely on extensive support from the stroma in order to survive, proliferate and invade. The tumor stroma is thus an important potential target for anti-cancer therapy. Typical changes in the stroma include a shift from the quiescence promoting-antiangiogenic extracellular matrix to a provisional matrix that promotes invasion and angiogenesis. These changes in the extracellular matrix are induced by changes in the secretion of extracellular matrix proteins and glucose amino glycans, extravasation of plasma proteins from hyperpermeable vessels and release of matrix modifying enzymes resulting in cleavage and cross-linking of matrix macromolecules. These in turn alter the rigidity of the matrix and the exposure and release of cytokines. Changes in matrix rigidity and vessel permeability affect drug delivery and mediate resistance to cytotoxic therapy. These stroma changes are brought about not only by the cancer cells, but also through the action of many cell types that are recruited by tumors including immune cells, fibroblasts and endothelial cells. Within the tumor, these normal host cells are activated resulting in loss of inhibitory and induction of cancer promoting activities. Key to the development of stroma-targeted therapies, selective biomarkers were developed for specific imaging of key aspects of the tumor stroma.     

The multifaceted role of autophagy in cancer and the microenvironment

Autophagy is a crucial recycling process that is increasingly being recognized as an important factor in cancer initiation, cancer (stem) cell maintenance as well as the development of resistance to cancer therapy in both solid and hematological malignancies. Furthermore, it is being recognized that autophagy also plays a crucial and sometimes opposing role in the complex cancer microenvironment. For instance, autophagy in stromal cells such as fibroblasts contributes to tumorigenesis by generating and supplying nutrients to cancerous cells. Reversely, autophagy in immune cells appears to contribute to tumor-localized immune responses and among others regulates antigen presentation to and by immune cells. Autophagy also directly regulates T and natural killer cell activity and is required for mounting T-cell memory responses. Thus, within the tumor microenvironment autophagy has a multifaceted role that, depending on the context, may help drive tumorigenesis or may help to support anticancer immune responses. This multifaceted role should be taken into account when designing autophagy-based cancer therapeutics. In this review, we provide an overview of the diverse facets of autophagy in cancer cells and nonmalignant cells in the cancer microenvironment. Second, we will attempt to integrate and provide a unified view of how these various aspects can be therapeutically exploited for cancer therapy.     

卵巢癌腹水非细胞成分对肿瘤的影响

卵巢癌病死率居妇科肿瘤最高,早期诊断率低,多数初次诊断时即为晚期。超过1/3的卵巢癌以及几乎全部的复发患者伴有腹水的产生。卵巢癌腹水中非细胞成分丰富复杂,包括细胞因子、蛋白质、代谢物和外泌体,形成复杂的腹水肿瘤微环境,影响肿瘤细胞的生物学行为及疾病进展。现就卵巢癌腹水非产细胞成分的种类、对肿瘤细胞及疾病的影响作一概述。     

Therapeutic strategies for targeting the ovarian tumor stroma

Epithelial ovarian cancer is the most lethal type of gynecologic malignancy. Sixty percent of women who are diagnosed with ovarian cancer present with advanced-stage disease that involves the peritoneal cavity and these patients have a 5-year survival rate of less than 30%. For more than two decades, tumor-debulking surgery followed by platinum-taxane combination chemotherapy has remained the conventional first-line treatment of ovarian cancer. Although the initial response rate is 70%-80%, most patients with advanced-stage ovarian cancer eventually relapse and succumb to recurrent chemoresistant disease. A number of molecular aberrations that drive tumor progression have been identified in ovarian cancer cells and intensive efforts have focused on developing therapeutic agents that target these aberrations. However, increasing evidence indicates that reciprocal interactions between tumor cells and various types of stromal cells also play important roles in driving ovarian tumor progression and that these stromal cells represent attractive therapeutic targets. Unlike tumor cells, stromal cells within the tumor microenvironment are in general genetically stable and are therefore less likely to become resistant to therapy. This concise review discusses the biological significance of the cross-talk between ovarian cancer cells and three major types of stromal cells (endothelial cells, fibroblasts, macrophages) and the development of new-generation therapies that target the ovarian tumor microenvironment.     

Stromal oncostatin M cytokine promotes breast cancer progression by reprogramming the tumor microenvironment

The tumor microenvironment (TME) is reprogrammed by cancer cells and participates in all stages of tumor progression. The contribution of stromal cells to the reprogramming of the TME is not well understood. Here, we provide evidence of the role of the cytokine oncostatin M (OSM) as central node for multicellular interactions between immune and nonimmune stromal cells and the epithelial cancer cell compartment. OSM receptor (OSMR) deletion in a multistage breast cancer model halted tumor progression. We ascribed causality to the stromal function of the OSM axis by demonstrating reduced tumor burden of syngeneic tumors implanted in mice lacking OSMR. Single-cell and bioinformatic analysis of murine and human breast tumors revealed that OSM expression was restricted to myeloid cells, whereas OSMR was detected predominantly in fibroblasts and, to a lower extent, cancer cells. Myeloid-derived OSM reprogrammed fibroblasts to a more contractile and tumorigenic phenotype and elicited the secretion of VEGF and proinflammatory chemokines CXCL1 and CXCL16, leading to increased myeloid cell recruitment. Collectively, our data support the notion that the stromal OSM/OSMR axis reprograms the immune and nonimmune microenvironment and plays a key role in breast cancer progression.     

The tumor suppressor gene ARHI regulates autophagy and tumor dormancy in human ovarian cancer cells

The role of autophagy in oncogenesis remains ambiguous, and mechanisms that induce autophagy and regulate its outcome in human cancers are poorly understood. The maternally imprinted Ras-related tumor suppressor gene aplasia Ras homolog member I (ARHI; also known as DIRAS3) is downregulated in more than 60% of ovarian cancers, and here we show that re-expression of ARHI in multiple human ovarian cancer cell lines induces autophagy by blocking PI3K signaling and inhibiting mammalian target of rapamycin (mTOR), upregulating ATG4, and colocalizing with cleaved microtubule-associated protein light chain 3 (LC3) in autophagosomes. Furthermore, ARHI is required for spontaneous and rapamycin-induced autophagy in normal and malignant cells. Although ARHI re-expression led to autophagic cell death when SKOv3 ovarian cancer cells were grown in culture, it enabled the cells to remain dormant when they were grown in mice as xenografts. When ARHI levels were reduced in dormant cells, xenografts grew rapidly. However, inhibition of ARHI-induced autophagy with chloroquine dramatically reduced regrowth of xenografted tumors upon reduction of ARHI levels, suggesting that autophagy contributed to the survival of dormant cells. Further analysis revealed that autophagic cell death was reduced when cultured human ovarian cancer cells in which ARHI had been re-expressed were treated with growth factors (IGF-1, M-CSF), angiogenic factors (VEGF, IL-8), and matrix proteins found in xenografts. Thus, ARHI can induce autophagic cell death, but can also promote tumor dormancy in the presence of factors that promote survival in the cancer microenvironment.     

Inhibition of autophagy sensitizes MDR-phenotype ovarian cancer SKVCR cells to chemotherapy

Autophagyis an intracellular lysosomal degradation pathway where its primary function is to allow cells to survive under stressful conditions. Autophagy is, however, a double-edge sword that can either promote cell survival or cell death.Chemoresistanceis a major challenge in the clinical treatment of ovarian cancer, of which the underlying mechanisms remain unknown.ObjectiveThe aim of the present study was to explore the role of autophagy in vincristine (VCR) resistant ovarian cancer cells.MethodsThe SKOV3 parental cell line and SKVCR, the VCR-resistant ovarian carcinoma cells were used. 3-MA (3-Methyladenine) and CQ (Chloroquine) were also used as autophagy inhibitors. CCK8 (Cell Counting Kit-8) was used to detect cell viability, quantitative real-time PCR and Western blot were used to detect the expressions of mRNA and protein, MDC staining and flow cytometry were used to detect autophagy and apoptosis, respectively.ResultsCompared with parental SKOV3 cells, SKVCR cells showed Multidrug Resistance (MDR). SKVCR cells demonstrated higher autophagy levels than SKOV3 cells, which could be inhibited by 3-MA and CQ. In SKVCR cells, VCR increased apoptosis levels further, 3-MA and CQ inhibited autophagy and potentiated the cytotoxicity by VCR. Moreover, 3-MA and CQ overcame the acquired VCR resistance in SKVCR cells by enhancing VCR-induced cytotoxicity, and promote apoptosis.ConclusionsOur data indicate that autophagy has a protective role in the multi-drug resistant SKVCR cells. The inhibition of autophagy increases the killing effects of VCR by increasing apoptosis and inhibiting autophagy, suggesting a better strategy for the treatment of drug-resistant SKVCR cells.     

Immunotherapy for pancreatic cancer

Pancreatic cancer, a highly lethal cancer, has the lowest 5-year survival rate for several reasons, including its tendency for the late diagnosis, a lack of serologic markers for screening, aggressive local invasion, its early metastatic dissemination, and its resistance to chemotherapy/radiotherapy. Pancreatic cancer evades immunologic elimination by a variety of mechanisms, including induction of an immunosuppressive microenvironment. Cancer-associated fibroblasts interact with inhibitory immune cells, such as tumor-associated macrophages and regulatory T cells, to form an inflammatory shell-like desmoplastic stroma around tumor cells. Immunotherapy has the potential to mobilize the immune system to eliminate cancer cells. Nevertheless, although immunotherapy has shown brilliant results across a wide range of malignancies, only anti-programmed cell death 1 antibodies have been approved for use in patients with pancreatic cancer who test positive for microsatellite instability or mismatch repair deficiency. Some patients treated with immunotherapy who show progression based on conventional response criteria may prove to have a durable response later. Continuation of immune-based treatment beyond disease progression can be chosen if the patient is clinically stable. Immunotherapeutic approaches for pancreatic cancer treatment deserve further exploration, given the plethora of combination trials with other immunotherapeutic agents, targeted therapy, stroma-modulating agents, chemotherapy, and multi-way combination therapies.     

肿瘤微环境促进子宫内膜癌细胞分泌雌激素

目的:筛选子宫内膜癌微环境中促进子宫内膜癌细胞雌激素分泌的细胞因子,并探讨相关机制。方法:提取子宫内膜癌间质细胞,用双重免疫荧光法进行鉴定。检测子宫内膜癌细胞(RL95-2、HEC-1A和HEC-1B)与间质细胞共培养和单独培养模式下,培养液上清雌激素浓度和肿瘤细胞芳香化酶的表达情况。用细胞因子芯片筛选2种模式下差异性表达的细胞因子,并用real-time PCR进行验证。结果:成功提取肿瘤间质细胞(波形蛋白为阳性)。共培养组上清雌激素浓度和肿瘤细胞中芳香化酶mRNA表达量均高于单独培养组(P<0.01)。共培养组上清中生长分化因子-15(GDF-15)的表达高于单独培养组,10 ng/mL的GDF-15可显著上调子宫内膜癌细胞中芳香化酶的表达(P<0.01)。结论:子宫内膜癌细胞与间质细胞共培养情况下,子宫内膜癌细胞中芳香化酶的表达,进而促进间质细胞雌激素浓度的合成,其中子宫内膜癌细胞中GDF-15可能发挥重要作用。     

Immunotherapy of ovarian cancer

Epithelial ovarian cancer remains the leading cause of death due to gynaecological malignancy. Although patients with advanced ovarian cancer have a good response to surgery and platinum-based chemotherapy, long-term survival remains poor. Immunotherapy techniques currently under investigation for treatment of recurrence include antitumour monoclonal and bispecific antibodies. Antibodies to ovarian cancer antigens have also been combined with radioisotopes, immunotoxins and chemotherapeutic drug conjugates to provide improved targeting of these agents. Anti-idiotypic antibodies and vaccines have also been developed to initiate humoral and cellular immune responses against ovarian cancer. Cytokines have been administered alone as well as in combination with other immunotherapy agents in patients with ovarian cancer. Finally, antigen-presenting cells are being modified by a variety of methods to stimulate an antitumour immune response. This review summarises the latest published clinical data and highlights promising areas of research in this exciting field.     

Role of the equilibrium between colon cancer and mononuclear cells in cytokine production

Patients with ulcerative colitis and Crohn's disease are at increased risk for colorectal cancer, a phenomenon assumed to be at least in part consequence of chronic inflammation. The purpose of this study was to examine whether human colon cancer cells may promote immune cells to produce cytokines, particularly those involved in inflammatory reaction. HT-29 and RKO human colon cancer cell lines were used. Human peripheral blood mononuclear cells (PBMC) were incubated for 24 h without or with cancer cells, or with supernatants derived from these cells cultured at the same conditions. TNFα, IL-1β, IL-6, IFNγ, IL-1ra and IL-10 secreted by PBMC were detected using specific ELISA kits. Interaction between colon cancer cells and PBMC induced secretion of pro- and anti-inflammatory cytokines in a dose-dependent manner. Furthermore, supernatants from increasing number of colon cancer cells caused a dose-dependent cytokine secretion. However, the production of cytokines was more pronounced when PBMC were directly exposed to tumor cells as compared to their supernatants. The results of our experimental model demonstrating an altered balance between pro- and anti-inflammatory cytokines generated by interaction between colon cancer and immune cells support the role of the malignant cells in promoting inflammation as one of the mechanisms for progression of colon cancer.     

Venous thrombosis and cancer: from mouse models to clinical trials

Cancer patients have a ~4 fold increased risk of venous thromboembolism (VTE) compared with the general population and this is associated with significant morbidity and mortality. This review summarizes our current knowledge of VTE and cancer, from mouse models to clinical studies. Notably, the risk of VTE varies depending on the type and stage of cancer. For instance, pancreatic and brain cancer patients have a higher risk of VTE than breast and prostate cancer patients. Moreover, patients with metastatic disease have a higher risk than those with localized tumors. Tumor‐derived procoagulant factors and growth factors may directly and indirectly enhance VTE. For example, increased levels of circulating tumor‐derived, tissue factor‐positive microvesicles may trigger VTE. In a mouse model of ovarian cancer, tumor‐derived IL‐6 and hepatic thrombopoietin have been linked to increased platelet production and thrombosis. In addition, mouse models of mammary and lung cancer showed that tumor‐derived granulocyte colony‐stimulating factor causes neutrophilia and activation of neutrophils. Activated neutrophils can release neutrophil extracellular traps (NETs) that enhance thrombosis. Cell‐free DNA in the blood derived from cancer cells, NETs and treatment with cytotoxic drugs can activate the clotting cascade. These studies suggest that there are multiple mechanisms for VTE in patients with different types of cancer. Preventing and treating VTE in cancer patients is challenging; the current recommendations are to use low‐molecular‐weight heparin. Understanding the underlying mechanisms may allow the development of new therapies to safely prevent VTE in cancer patients.     

Antitumor Effects of Chimeric Receptor Engineered Human T Cells Directed to Tumor Stroma

Cancer-associated fibroblasts (CAFs), the principle component of the tumor-associated stroma, form a highly protumorigenic and immunosuppressive microenvironment that mediates therapeutic resistance. Co-targeting CAFs in addition to cancer cells may therefore augment the antitumor response. Fibroblast activation protein-α (FAP), a type 2 dipeptidyl peptidase, is expressed on CAFs in a majority of solid tumors making it an attractive immunotherapeutic target. To target FAP-positive CAFs in the tumor-associated stroma, we genetically modified T cells to express a FAP-specific chimeric antigen receptor (CAR). The resulting FAP-specific T cells recognized and killed FAP-positive target cells as determined by proinflammatory cytokine release and target cell lysis. In an established A549 lung cancer model, adoptive transfer of FAP-specific T cells significantly reduced FAP-positive stromal cells, with a concomitant decrease in tumor growth. Combining these FAP-specific T cells with T cells that targeted the EphA2 antigen on the A549 cancer cells themselves significantly enhanced overall antitumor activity and conferred a survival advantage compared to either alone. Our study underscores the value of co-targeting both CAFs and cancer cells to increase the benefits of T-cell immunotherapy for solid tumors.     

Development of cancer vaccines to activate cytotoxic T lymphocytes

Cancer vaccines have been shown to stimulate cytotoxic T lymphocyte (CTL) responses in a variety of cancer patients. However, the response is often of low frequency and moderate avidity, and does not result in objective clinical responses. This is related to the target antigens, which are usually over-expressed self-antigens that elicit tolerogenic and regulatory immune responses, resulting in deletion or inactivation of high-avidity T cells. Although moderate-avidity T cells can be efficient killers, tumours are often poor targets as they express a variety of molecules to protect them from cell-mediated immunity. Adoptive transfer of large numbers of high-avidity Tcells has been shown to induce regression of bulky disease, proving that immune responses can effectively eradicate tumours. New approaches that target activated de-ndritic cells invivo, resulting in cross-presentation of CTL epitopes and release of cytokines that suppress regulatory T cells, have resulted in the pr-oduction of T cells with sufficient avidity to kill tumour target cells. These approaches in combination with regimes, such as cytokine therapy, chemotherapy or radiotherapy, that modulate effector costimulatory expression on tumour targets may result in more effective second-generation cancer vaccines.     

The tumour microenvironment and implications for cancer immunotherapy

Tumour cells exist in a complex milieu of cellular and non-cellular components comprising fibroblasts, endothelial cells, immune cells and metabolites of cellular respiration. An elaborate interplay between these components and tumour cells exists with implications for immunological recognition of tumour cells. Tumours have been shown to alter their antigen and cytokine profiles, desensitise and impair immune defences, signal fibroblasts to facilitate metastasis, and take advantage of acidic and hypoxic conditions that impede normal cells. This paper aims to review the roles of the stroma, extracellular matrix and chemistry of the microenvironment on tumour growth, with particular emphasis on interactions with the immune system, and to highlight some of the novel therapeutic strategies that target the tumour microenvironment.     

Pathophysiologic significance of host reactions in human cancer tissue: desmoplasia and tumor immunity.

Invasive growth of malignant cells, particularly carcinoma cells, induces host reaction within and around tumor tissue. Representatives of them are desmoplasia, angiogenesis and immune reactions. Desmoplasia, a process of fibrosis, is induced by activation of fibroblasts with increased production of matrix proteins and matrix degrading enzymes. Angiogenesis is prerequisite for the growth of solid tumor. Inhibition of this is now a target of cancer therapy. The present author has proposed a concept that tumor vessels are composed of nutrient vessels and immune/inflammatory vessels. The latter is similar to venules in inflammatory lesions expressing the cell adhesion molecules to facilitate the transmigration of inflammatory cells to the tissue. In colon cancer, venules distributed along the invasive margin correspond to these vessels, which express E-, and P-selectins, and ICAM-1. These venules are considered to be an entry site of immune/inflammatory cells to cancer tissue. To further analyze immune mechanism, the present authors have confirmed that macrophages distributed along the invasive margin of colon cancer express costimulatory molecules B7.1/B7.2, which are required for the proliferation of T-cells. T-cells were co-localized with these cells. Clinicopathologic analysis confirmed that CD8+ T-cells distributed within cancer cell nest (intraepithelial) have the most significant impact on the patients' survival in colorectal cancer. These data suggest that various host reactions take place in the stroma of cancer tissue, which modulate the biologic behavior of cancer.     

The role of cytokines in cancer cachexia

A large number of observations point towards cytokines, polypeptides released mainly by immune cells, as the molecules responsible for the metabolic derangements associated with cancer-bearing states. Indeed, these alterations lead to a pathological state known as cancer cachexia which is, unfortunately, one of the worst effects of malignancy, accounting for nearly a third of cancer deaths. It is characterized by weight loss together with anorexia, weakness, anemia, and asthenia. The complications associated with the appearance of the cachectic syndrome affect both the physiological and biochemical balance of the patient and have effects on the efficiency of the anticancer treatment, resulting in a considerably decreased survival time. At the metabolic level, cachexia is associated with loss of skeletal muscle protein together with a depletion of body lipid stores. The cachectic patient, in addition to having practically no adipose tissue, is basically subject to an important muscle wastage manifested as an excessive nitrogen loss. The metabolic changes are partially mediated by alterations in circulating hormone concentrations (insulin, glucagon, and glucocorticoids in particular) or in their effectiveness. The present study reviews the involvement of different cytokines in the metabolic and physiological alterations associated with tumor burden and cachexia. Among these cytokines, some can be considered as procachectic (such as tumor necrosis factor-alpha), while others having opposite effects can be named as anticachectic cytokines. It is the balance between these two cytokine types that finally seems to have a key role in cancer cachexia.     

Bystander killing of cancer requires the cooperation of CD4(+) and CD8(+) T cells during the effector phase

Cancers frequently evade cytotoxic T lymphocyte-mediated destruction through loss or down-regulation of tumor antigens and antigen-presenting major histocompatibility complex molecules. Therefore, we have concentrated our efforts on immunological strategies that destroy nonmalignant stromal cells essential for the survival and growth of cancer cells. In this study, we developed a non-T cell receptor transgenic, immunocompetent tumor model to determine whether tumor-bearing hosts' own immune systems could eliminate cancer cells through stromal targeting and what role CD4(+) T cells play alongside CD8(+) T cells in this process. We found that aggressive cancers could be eradicated by T cell targeting of tumor stroma. However, successful elimination required the cooperation of CD4(+) and CD8(+) T cells not only during the induction phase but also during the effector phase in the tumor microenvironment, implying a new role for CD4(+) T cells that has not been previously described. Our study demonstrates the potential of stromal targeting as a cancer immunotherapy and suggests that successful anticancer strategies must facilitate cooperation between CD4(+) and CD8(+) T cells at the right times and the right places.