Tumor Burden Influences Cytotoxic T Cell Development in Metastatic Breast Cancer Patients—A Phase I/II Study

MUC1 in Cancer Immunotherapy - New Hope or Phantom Menace?

Understanding of the functioning of MUC1 (human mucin) has advanced significantly over 40 years of its investigation. The anti-adhesive properties of the extracellular domain, which were the main focus of early studies initially explaining overexpression of MUC1 in progressing oncological diseases, were gradually put on the back burner. Researchers became more interested in its regulatory and signaling functions in cells rather in its anti-adhesive properties. The found the ability of MUC1 for signal transduction, and its ability to participate in cell metabolism opened new possibilities for improved control over cancer cells in addition to just attracting antigens of the immune system to a target. Nevertheless, there are issues in the functioning of MUC1 that raise doubts about its effectiveness in cancer immunotherapy.

Genetically Engineered T-Cells for Malignant Glioma: Overcoming the Barriers to Effective Immunotherapy

Malignant gliomas carry a dismal prognosis. Conventional treatment using chemo- and radiotherapy has limited efficacy with adverse events. Therapy with genetically engineered T-cells, such as chimeric antigen receptor (CAR) T-cells, may represent a promising approach to improve patient outcomes owing to their potential ability to attack highly infiltrative tumors in a tumor-specific manner and possible persistence of the adaptive immune response. However, the unique anatomical features of the brain and susceptibility of this organ to irreversible tissue damage have made immunotherapy especially challenging in the setting of glioma. With safety concerns in mind, multiple teams have initiated clinical trials using CAR T-cells in glioma patients. The valuable lessons learnt from those trials highlight critical areas for further improvement: tackling the issues of the antigen presentation and T-cell homing in the brain, immunosuppression in the glioma microenvironment, antigen heterogeneity and off-tumor toxicity, and the adaptation of existing clinical therapies to reflect the intricacies of immune response in the brain. This review summarizes the up-to-date clinical outcomes of CAR T-cell clinical trials in glioma patients and examines the most pressing hurdles limiting the efficacy of these therapies. Furthermore, this review uses these hurdles as a framework upon which to evaluate cutting-edge pre-clinical strategies aiming to overcome those barriers.

Targeted Immunotherapy Designed to Treat MUC1-Expressing Solid Tumour

Several approaches to antigen-specific immunotherapy of cancer antigen-specific immunotherapy of cancer have been tested clinically. In this chapter, we will describe studies done with the antigen MUC1. Tested MUC1 therapeutic vaccines include the following: monoclonal antibodies (MAbs) specific for MUC1; synthetic and recombinant polypeptides from the protein sequence of MUC1; dendritic cells carrying MUC1; RNA and DNA vaccinations; and recombinant viruses carrying the MUC1 DNA sequence. Chemotherapy of cancer aims to be toxic to the cancer cells with manageable side effects to the patient. In contrast, antigen-specific immunotherapy of cancer aims to treat the patient, such that the patient is then able to control and eventually eliminate their cancer cells. It is therefore important to know the immune status of each cancer patient prior to therapy.

Therapeutic vaccines for cancer: an overview of clinical trials

The therapeutic potential of host-specific and tumour-specific immune responses is well recognized and, after many years, active immunotherapies directed at inducing or augmenting these responses are entering clinical practice. Antitumour immunization is a complex, multi-component task, and the optimal combinations of antigens, adjuvants, delivery vehicles and routes of administration are not yet identified. Active immunotherapy must also address the immunosuppressive and tolerogenic mechanisms deployed by tumours. This Review provides an overview of new results from clinical studies of therapeutic cancer vaccines directed against tumour-associated antigens and discusses their implications for the use of active immunotherapy.

Phenotypic plasticity of MDSC in cancers

Myeloid-derived suppressor cells (MDSCs) were initially reported as suppressor of the adaptive immune responses against cancer and other diseases. However, emerging evidence suggest that MDSCs may also support anti-tumor immune responses under certain conditions or may inhibit tumor growth. In the present mini-review, we suggest that such opposing functions of MDSCs are due to phenotypic plasticity of the myeloid cells, allowing them to produce a diverse form of morphology, physiological state, and function in response to environmental conditions. Therefore, they can be manipulated by means of immune modulators to overcome their immune suppressive function.

MUC1-specific cytotoxic T lymphocytes in cancer therapy: induction and challenge

MUC1 glycoprotein is often found overexpressed and hypoglycosylated in tumor cells from numerous cancer types. Since its discovery MUC1 has been an attractive target for antitumor immunotherapy. Indeed, in vitro and in vivo experiments have shown T-cell-specific responses against MUC1 in an HLA-restricted and HLA-unrestricted manner, although some animal models have highlighted the possible development of tolerogenic responses against this antigen. These observations permit the development of new T-cell vaccine strategies capable of inducing an MUC1-specific cytotoxic T cell response in cancer patients. Some of these strategies are now being tested in clinical trials against different types of cancer. To date, encouraging clinical responses have been observed with some MUC1 vaccines in phase II/III clinical trials. This paper compiles knowledge regarding MUC1 as a promising tumor antigen for antitumor therapeutic vaccines applicable to numerous cancers. We also summarize the results of MUC1-vaccine-based clinical trials.

MUC1 immunotherapy is here to stay

INTRODUCTION

Success of HBV vaccines in reducing the incidence of liver cancer, and HPV vaccines in reducing preneoplastic cervical lesions, demonstrate the potential of cancer reduction by harnessing the immune system. For most human cancers, infectious etiology is not known but other tumor antigens, candidates for vaccines, have been identified.

AREAS COVERED

The authors discuss knowledge accumulated the last two decades on the tumor antigen MUC1 that has put it at the top of the list as an immunotherapy reagent. They examine evidence that anti-MUC1 immunity affects tumor development and prognosis. Finally, they review two decades of immunotherapy trials targeting MUC1, focusing primarily on vaccines but also adoptive antibody and T-cell therapies.

EXPERT OPINION

Most approaches targeting MUC1 have been immunotherapies administered to date to more than 1200 patients in clinical trials. Even though these trials focused on advanced cancer, encouraging results were reported particularly for less immunosuppressed patients. Furthermore, spontaneous anti-MUC1 immune responses are associated with better prognosis or with a reduced lifetime risk of developing MUC1+ cancers. MUC1 is abnormally expressed in over 80% of all cancers. Successfully targeting this molecule could benefit over a million patients diagnosed yearly with MUC1+ tumors just in the USA.

Immunotherapy of breast cancer

INTRODUCTION

Immunotherapy of breast cancer has been shown to prevent recurrence, improve survival and eliminate breast cancer in humans.

AREAS COVERED

The reason for this review is to present the current information and the prospects for the future of immunotherapy of breast cancer in humans to include tumor antigens for vaccines and targets for monoclonal antibodies and adoptive T-cell therapy, and immune modulatory agents, such as adjuvants to stimulate the immune response and inhibitors of checkpoint blockade to prevent downmodulation of activated lymphocytes, to enhance these modalities. The research discussed and the literature search undertaken is of the clinical immunotherapy of breast cancer in humans, from 2000 to September, 2011.

EXPERT OPINION

The key message of the paper is that one reason for the failure of the immune system to control macroscopic disease is that the immune escape mechanisms involving both tumor and the tumor stroma prevent the immune system from destroying the tumor. Changing the tumor microenvironment is necessary to eliminate macroscopic tumors. Prospects for improvement are proposals for combining current modalities of therapy with type 1 cellular immunity-inducing agents, all targeting multiple tumor antigens and in the context of minimal disease.

Cytotoxic T-lymphocyte immunotherapy for ovarian cancer: a pilot study

The objective was to evaluate the toxicity and feasibility of intraperitoneal infusion of tumor-specific cytotoxic T lymphocytes (CTL) as therapy for recurrent ovarian cancer, and to determine if repetitive cycles of CTL generation and infusion measurably increases the host's ovarian cancer immune response. In this study, 7 subjects with recurrent ovarian cancer confined to the peritoneal cavity underwent up to 4 cycles, each cycle beginning with a leukapheresis for collection of precursor lymphocytes, which were stimulated in vitro with mucin 1, a tumor-specific antigen found commonly in ovarian cancer cells. The resulting new CTL for each cycle were reintroduced into the host by intraperitoneal infusion. Immunologic parameters (killer cells, cytokine production, memory T lymphocytes, and natural killer cells) were studied. Toxicity, CA-125, and survival data were also evaluated. The tumor marker CA-125 was nonstatistically significantly reduced after the first month of immunotherapy. However, after that it rose. Killer cells, cytokine production, and memory T lymphocytes increased after the first cycle of stimulation, but plateaued or reduced thereafter. The percent of natural killer cells inversely correlated with other immune parameters. Median survival was 11.5 months. One subject is free of disease since December, 2000. Multiple cycles, beyond 1 cycle, of T-cell stimulation followed by adoptive T-cell infusion, may not enhance the in vivo immune response.

Developing an effective breast cancer vaccine

BACKGROUND

Harnessing the immune response in treating breast cancer would potentially offer a less toxic, more targeted approach to eradicating residual disease. Breast cancer vaccines are being developed to effectively train cytotoxic T cells to recognize and kill transformed cells while sparing normal ones. However, achieving this goal has been problematic due to the ability of established cancers to suppress and evade the immune response.

METHODS

A review of the literature on vaccines and breast cancer treatment was conducted, specifically addressing strategies currently available, as well as appropriate settings, paradigms for vaccine development and response monitoring, and challenges with immunosuppression.

RESULTS

Multiple issues need to be addressed in order to optimize the benefits offered by breast cancer vaccines. Primary issues include the following: (1) cancer vaccines will likely work better in a minimal residual disease state, (2) clinical trial design for immunotherapy should incorporate recommendations from expert groups such as the Cancer Vaccine Working Group and use standardized immune response measurements, (3) the presently available cancer vaccine approaches, including dendritic cell-based, tumor-associated antigen peptide-based, and whole cell-based, have various pros and cons, (4) to date, no one approach has been shown to be superior to another, and (5) vaccines will need to be combined with immunoregulatory agents to overcome tumor-related immunosuppression.

CONCLUSIONS

Combining a properly optimized cancer vaccine with novel immunomodulating agents that overcome tumor-related immunosuppression in a well-designed clinical trial offers the best hope for developing an effective breast cancer vaccine strategy.

MUC1 immunotherapy

The overexpression and aberrant glycosylation of MUC1 is associated with a wide variety of cancers, making it an ideal target for immunotherapeutic strategies. This review highlights the main avenues of research in this field, focusing on adenocarcinomas, from the preclinical to clinical; the problems and possible solutions associated with each approach; and speculates on the direction of MUC1 immunotherapeutic research over the next 5-10 years.