Claudia Palena

Sublethal Irradiation of Human Tumor Cells Modulates Phenotype Resulting in Enhanced Killing by Cytotoxic T Lymphocytes

Local radiation of tumor masses is an established modality for the therapy of a range of human tumors. It has recently been recognized that doses of radiation, lower than or equal to those that cause direct cytolysis, may alter the phenotype of target tissue by up-regulating gene products that may make tumor cells more susceptible to T-cell–mediated immune attack. Previously, we demonstrated that radiation increased Fas (CD95) gene expression in carcinoembryonic antigen (CEA)-expressing murine tumor cells, which consequently enhanced their susceptibility to CEA-specific CTL-mediated killing. The present study was designed to determine whether these phenomena also occur with human tumor cells. Here, 23 human carcinoma cell lines (12 colon, 7 lung, and 4 prostate) were examined for their response to nonlytic doses of radiation (10 or 20 Gy). Seventy-two hours postirradiation, changes in surface expression of Fas (CD95), as well as expression of other surface molecules involved in T-cell–mediated immune attack such as intercellular adhesion molecule 1, mucin-1, CEA, and MHC class I, were examined. Twenty-one of the 23 (91%) cell lines up-regulated one or more of these surface molecules postirradiation. Furthermore, five of five irradiated CEA+/A2+ colon tumor cells lines demonstrated significantly enhanced killing by CEA-specific HLA-A2–restricted CD8+ CTLs compared with nonirradiated counterparts. We then used microarray analysis to broaden the scope of observed changes in gene expression after radiation and found that many additional genes had been modulated. These up-regulated gene products may additionally enhance the tumor cells’ susceptibility to T-cell–mediated immune attack or serve as additional targets for immunotherapy. Overall, the results of this study suggest that nonlethal doses of radiation can be used to make human tumors more amenable to immune system recognition and attack and form the rational basis for the combinatorial use of cancer vaccines and local tumor irradiation.

IL-8 Signaling Plays a Critical Role in the Epithelial–Mesenchymal Transition of Human Carcinoma Cells

The switch of tumor cells from an epithelial to a mesenchymal-like phenotype [designated as epithelial-to-mesenchymal transition (EMT)] is known to induce tumor cell motility and invasiveness, therefore promoting metastasis of solid carcinomas. Although multiple studies have focused on elucidating the signaling events that initiate this phenotypic switch, there has been so far no characterization of the pattern of soluble mediators released by tumor cells undergoing EMT, and the potential impact that this phenotypic switch could have on the remodeling of the tumor microenvironment. Here we show that induction of EMT in human carcinoma cells via overexpression of the transcription factor Brachyury is associated with enhanced secretion of multiple cytokines, chemokines, and angiogenic factors and, in particular, with the induction of the IL-8/IL-8R axis. Our results also indicate the essential role of interleukin 8 (IL-8) signaling for the acquisition and/or maintenance of the mesenchymal and invasive features of Brachyury-overexpressing tumor cells and show that IL-8 secreted by tumor cells undergoing EMT could potentiate tumor progression by inducing adjacent epithelial tumor cells into EMT. Altogether, our results emphasize the potential role of EMT in the modulation of the tumor microenvironment via secretion of multiple soluble mediators and suggest that IL-8 signaling blockade may provide a means of targeting mesenchymal-like, invasive tumor cells.

Pilot Study of Vaccination with Recombinant CEA-MUC-1-TRICOM Poxviral-Based Vaccines in Patients with Metastatic Carcinoma

Purpose: Poxviral vectors have a proven safety record and can be used to incorporate multiple transgenes. Prior clinical trials with poxviral vaccines have shown that immunologic tolerance to self-antigens can be broken. Carcinoembryonic antigen (CEA) and MUC-1 are overexpressed in a substantial proportion of common solid carcinomas. The primary end point of this study was vaccine safety, with immunologic and clinical responses as secondary end points. Experimental Design: We report here a pilot study of 25 patients treated with a poxviral vaccine regimen consisting of the genes for CEA and MUC-1, along with a triad of costimulatory molecules (TRICOM; composed of B7.1, intercellular adhesion molecule 1, and lymphocyte function–associated antigen 3) engineered into vaccinia (PANVAC-V) as a prime vaccination and into fowlpox (PANVAC-F) as a booster vaccination. Results: The vaccine was well tolerated. Apart from injection-site reaction, no grade ≥2 toxicity was seen in more than 2% of the cycles. Immune responses to MUC-1 and/or CEA were seen following vaccination in 9 of 16 patients tested. A patient with clear cell ovarian cancer and symptomatic ascites had a durable (18-month) clinical response radiographically and biochemically, and one breast cancer patient had a confirmed decrease of >20% in the size of large liver metastasis. Conclusions: This vaccine strategy seems to be safe, is associated with both CD8 and CD4 immune responses, and has shown evidence of clinical activity. Further trials with this agent, either alone or in combination with immunopotentiating and other therapeutic agents, are warranted.

The T-box transcription factor Brachyury promotes epithelial-mesenchymal transition in human tumor cells

Metastatic disease is responsible for the majority of human cancer deaths. Understanding the molecular mechanisms of metastasis is a major step in designing effective cancer therapeutics. Here we show that the T-box transcription factor Brachyury induces in tumor cells epithelial-mesenchymal transition (EMT), an important step in the progression of primary tumors toward metastasis. Overexpression of Brachyury in human carcinoma cells induced changes characteristic of EMT, including upregulation of mesenchymal markers, downregulation of epithelial markers, and an increase in cell migration and invasion. Brachyury overexpression also repressed E-cadherin transcription, an effect partially mediated by Slug. Conversely, inhibition of Brachyury resulted in downregulation of mesenchymal markers and loss of cell migration and invasion and diminished the ability of human tumor cells to form lung metastases in a xenograft model. Furthermore, we found Brachyury to be overexpressed in various human tumor tissues and tumor cell lines compared with normal tissues. We also determined that the percentage of human lung tumor tissues positive for Brachyury expression increased with the stage of the tumor, indicating a potential association between Brachyury and tumor progression. The selective expression of Brachyury in tumor cells and its role in EMT and cancer progression suggest that Brachyury may be an attractive target for antitumor therapies.

The Human T-Box Mesodermal Transcription Factor Brachyury Is a Candidate Target for T-Cell–Mediated Cancer Immunotherapy

Purpose: Identification of tumor antigens is essential in advancing immune-based therapeutic interventions in cancer. Particularly attractive targets are those molecules that are selectively expressed by malignant cells and that are also essential for tumor progression. Experimental Design and Results: We have used a computer-based differential display analysis tool for mining of expressed sequence tag clusters in the human Unigene database and identified Brachyury as a novel tumor antigen. Brachyury, a member of the T-box transcription factor family, is a key player in mesoderm specification during embryonic development. Moreover, transcription factors that control mesoderm have been implicated in the epithelial-mesenchymal transition (EMT), which has been postulated to be a key step during tumor progression to metastasis. Reverse transcription-PCR analysis validated the in silico predictions and showed Brachyury expression in tumors of the small intestine, stomach, kidney, bladder, uterus, ovary, and testis, as well as in cell lines derived from lung, colon, and prostate carcinomas, but not in the vast majority of the normal tissues tested. An HLA-A0201 epitope of human Brachyury was identified that was able to expand T lymphocytes from blood of cancer patients and normal donors with the ability to lyse Brachyury-expressing tumor cells. Conclusions: To our knowledge, this is the first demonstration that (a) a T-box transcription factor and (b) a molecule implicated in mesodermal development, i.e., EMT, can be a potential target for human T-cell–mediated cancer immunotherapy.

Combination Chemotherapy and Radiation of Human Squamous Cell Carcinoma of the Head and Neck Augments CTL-Mediated Lysis

Purpose: The combination of systemic multiagent chemotherapy (5-fluorouracil + cisplatin) and tumor irradiation is standard of care for head and neck squamous cell carcinoma (HNSCC). Furthermore, it has been shown that sublethal doses of radiation or chemotherapeutic drugs in diverse cancer types may alter the phenotype or biology of neoplastic cells, making them more susceptible to CTL-mediated cytotoxicity. However, little is known about the potential synergistic effect of drug plus radiation on CTL killing. Here, we examined whether the combination of two chemotherapeutics and ionizing radiation enhanced CTL-mediated destruction of HNSCC more so than either modality separately, as well as the basis for the enhanced tumor cell lysis. Experimental Design: Several HNSCC cell lines with distinct biological features were treated with sublethal doses of cisplatin and 5-fluorouracil for 24 hours and with 10-Gy irradiation. Seventy-two hours postirradiation, tumor cells were exposed to an antigen-specific CD8+ CTL directed against carcinoembryonic antigen or MUC-1. Results: In three of three tumor cell lines tested, enhanced CTL activity was observed when the two modalities (chemotherapy and radiation) were combined as compared with target cells exposed to either modality separately. CTL-mediated lysis was MHC restricted and antigen specific and occurred almost entirely via the perforin pathway. Moreover, the combination treatment regimen led to a 50% reduction in Bcl-2 expression whereas single modality treatment had little bearing on the expression of this antiapoptotic gene. Conclusions: Overall, these results reveal that (a) CTL killing can be enhanced by combining multiagent chemotherapy and radiation and (b) combination treatment enhanced or sensitized HNSCC to the perforin pathway, perhaps by down-regulating Bcl-2 expression. These studies thus form the rational basis for clinical trials of immunotherapy concomitant with the current standard of care of HNSCC.

Influence of IL-8 on the epithelial–mesenchymal transition and the tumor microenvironment

The phenomenon of epithelial-mesenchymal transition (EMT) has gained attention in the field of cancer biology for its potential contribution to the progression of carcinomas. Tumor EMT is a phenotypic switch that promotes the acquisition of a fibroblastoid-like morphology by epithelial tumor cells, resulting in enhanced tumor cell motility and invasiveness, increased metastatic propensity and resistance to chemotherapy, radiation and certain small-molecule-targeted therapies. Tumor cells undergoing EMT are also known to increase the secretion of specific factors, including cytokines, chemokines and growth factors, which could play an important role in tumor progression. This review summarizes the current knowledge on the secretory properties of epithelial tumor cells that have undergone an EMT, with an emphasis on the potential role of the IL-8-IL-8 receptor axis on the induction and/or maintenance of tumor EMT and its ability to remodel the tumor microenvironment.

Identification of Novel Human CTL Epitopes and Their Agonist Epitopes of Mesothelin

Purpose: Mesothelin is overexpressed in many pancreatic and ovarian cancers, mesotheliomas, and other tumor types. Clinical trials are ongoing using immunotoxins to target mesothelin, and patients immunized with allogeneic pancreatic tumor cell lines have shown immune responses to previously defined mesothelin epitopes. The purpose of this study was to define novel mesothelin CTL epitopes and, more importantly, agonist epitopes that would more efficiently activate human T cells to more efficiently lyse human tumors. Experimental Design and Results: Two novel mesothelin HLA-A2 epitopes were defined. T-cell lines generated from one of these epitopes were shown to lyse pancreatic and ovarian tumor cells. Several agonist epitopes were defined and were shown to (a) have higher affinity and avidity for HLA-A2, (b) activate mesothelin-specific T cells from normal individuals or cancer patients to a greater degree than the native epitope in terms of induction of higher levels of IFN-γ and the chemokine lymphotactin, and (c) lyse several mesothelin-expressing tumor types in a MHC-restricted manner more effectively than T cells generated using the native peptide. External beam radiation of tumor cells at nontoxic levels was shown to enhance the expression of mesothelin and other accessory molecules, resulting in a modest but statistically significant increase in tumor cell lysis by mesothelin-specific T cells. Conclusions: The identification of novel CTL agonist epitopes supports and extends observations that mesothelin is a potential target for immunotherapy of pancreatic and ovarian cancers, as well as mesotheliomas.

Cancer vaccines: preclinical studies and novel strategies.

The development of cancer vaccines, aimed to enhance the immune response against a tumor, is a promising area of research. A better understanding of both the molecular mechanisms that govern the generation of an effective immune response and the biology of a tumor has contributed to substantial progress in the field. Areas of intense investigation in cancer immunotherapy will be discussed here, including: (1) the discovery and characterization of novel tumor antigens to be used as targets for vaccination; (2) the investigation of different vaccine-delivery modalities such as cellular-based vaccines, protein- and peptide-based vaccines, and vector-based vaccines; (3) the characterization of biological adjuvants to further improve the immunogenicity of a vaccine; and (4) the investigation of multimodal therapies where vaccines are being combined with other oncological treatments such as radiation and chemotherapy. A compilation of data from preclinical studies conducted in vitro as well as in animal models is presented here. The results from these studies would certainly support the development of new vaccination strategies toward cancer vaccines with enhanced clinical efficacy.

Vaccines against human carcinomas: strategies to improve antitumor immune responses.

Multiple observations in preclinical and clinical studies support a role for the immune system in controlling tumor growth and progression. Various components of the innate and adaptive immune response are able to mediate tumor cell destruction; however, certain immune cell populations can also induce a protumor environment that favors tumor growth and the development of metastasis. Moreover, tumor cells themselves are equipped with various mechanisms that allow them to evade surveillance by the immune system. The goal of cancer vaccines is to induce a tumor-specific immune response that ultimately will reduce tumor burden by tipping the balance from a protumor to an antitumor immune environment. This review discusses common mechanisms that govern immune cell activation and tumor immune escape, and some of the current strategies employed in the field of cancer vaccines aimed at enhancing activation of tumor-specific T-cells with concurrent reduction of immunosuppression.