T cell-mediated immunotherapy of metastases: state of the art in 2005

Combination of Radiotherapy and Targeted Agents in Brain Metastasis: An Update

OPINION STATEMENT

The combination of radiation therapy and targeted agents (molecular inhibitors or immunotherapy) represents an opportunity to improve the outcomes of patients with brain metastases. The combination of whole-brain radiation therapy (WBRT) with targeted agents takes advantage of radiosensitization, while the combination with stereotactic radiosurgery (SRS) may allow one to substitute an effective systemic agent for adjuvant WBRT, the historical standard of care. This strategy may in turn allow the promotion of secondary prevention paradigms with possibly less cognitive toxicity. At present, the combination of targeted therapy with SRS rather than with WBRT is the more viable option although both avenues will likely have a role in the future management of brain metastases. Patients should be encouraged to enter clinical trials since the off-study use of these combinations will delay the advancement of the field. Caution is advised in the combination of radiation and targeted agents as unexpected toxicities can occur. Clinicians should avail themselves of clinical trials in order to offer patients these promising options and to move the field forward. In the absence of a clinical trial, we recommend the combination of SRS with targeted agents and deferred WBRT. Small, asymptomatic brain metastases may be best managed with single-modality targeted agents with deferred radiation therapy, preferably on a clinical trial. Advances in targeted therapies combined with radiation therapy will most likely improve local control and hopefully the quality of life and survival of patients with brain metastasis.

Newcastle disease virus: a promising vector for viral therapy, immune therapy, and gene therapy of cancer

This review deals with the avian paramyxovirus Newcastle disease virus (NDV) and describes properties that explain its oncolytic activity, its tumor-selective replication behavior, and its immune-stimulatory capacity with human cells. The strong interferon response of normal cells upon contact with NDV appears to be the basis for the good tolerability of the virus in cancer patients and for its immune stimulatory properties, whereas the weak interferon response of tumor cells explains the tumor selectivity of replication and oncolysis. Various concepts for the use of this virus for cancer treatment are pointed out and results from clinical studies are summarized. Reverse genetics technology has made it possible recently to clone the genome and to introduce new foreign genes thus generating new recombinant viruses. These can, in the future, be used to transfer new therapeutic genes into tumors and also to immunize against new emerging pathogens. The modular nature of gene transcription, the undetectable rate of recombination, and the lack of a DNA phase in the replication cycle make NDV a suitable candidate for the rational design of a safe and stable vaccine and gene therapy vector.

Reovirus: viral therapy for cancer 'as nature intended'

Oncolytic viruses are tumour selective and able to lyse cancer cells after infection. Reovirus is an example of a wild-type oncolytic virus and is currently being investigated as a potential novel therapy for cancer. This overview gives a brief description of what is known about reovirus biology and summarises the preclinical data related to its oncolytic ability. The completed and ongoing clinical trials involving reovirus, both as a single agent and in combination with chemotherapy and radiotherapy, will be reviewed and their results discussed. Many of these clinical studies are being conducted by centres in the UK.

Photodynamic therapy plus low-dose cyclophosphamide generates antitumor immunity in a mouse model

Photodynamic therapy (PDT) is a modality for the treatment of cancer involving excitation of nontoxic photosensitizers with harmless visible light-producing cytotoxic reactive oxygen species. PDT causes apoptosis and necrosis of tumor cells, destruction of the tumor blood supply, and activation of the immune system. The objective of this study was to compare in an animal model of metastatic cancer PDT alone and PDT combined with low-dose cyclophosphamide (CY) a treatment that has been proposed to deplete regulatory T cells (T-regs) and increase the immune response to some tumors. We used J774 tumors (a highly metastatic reticulum cell sarcoma line) and PDT with benzoporphyrin derivative monoacid ring A, verteporfin for injection (BPD; 1-mg/kg injected i.v. followed after 15 min by 150 J/cm(2) of 690-nm light). CY (50 or 150 mg/kg i.p.) was injected 48 h before light delivery. PDT alone led to tumor regressions and a survival advantage but no permanent cures were obtained. BPD-PDT in combination with low-dose CY (but not high-dose CY) led to 70% permanent cures. Low-dose CY alone gave no permanent cures but did provide a survival advantage and was shown to reduce CD4+FoxP3+ T-regs in lymph nodes, whereas high-dose CY reduced other lymphocyte classes as well. Cured animals were rechallenged with J774 cells, and the tumors were rejected in 71% of mice. Cured mice had tumor-specific T cells in spleens as determined by a (51)Cr release assay. We conclude that low-dose CY depletes T-regs and potentiates BPD-PDT, leading to tumor cures and memory immunity.

Recent Advances and Current Challenges in Tumor Immunology and Immunotherapy

Despite advances in animal studies, where the cure of the majority of mice with pre-established (albeit early-stage) tumors has become almost standard, human clinical trials have been much less successful. Here we describe some of the most recent advances in the specialist field of tumor immunology and immunotherapy, highlighting salient work to identify key problem areas and potential solutions. We make particular note of recent developments in adoptive therapy; whole-cell, DNA, and peptide vaccines; and antibody therapy. We also describe the revival of interest in regulatory T cells and conclude by detailing the need for clinical trial read-out autonomy and methods to predict which patients will respond to a particular treatment.

Identification and characterization of IS1 transposition in plasmid amplification mutants of E. coli clones producing DNA vaccines

Merck Research Laboratories has developed a highly productive Escherichia coli fermentation process to produce plasmid DNA for use as vaccines. The process consists of a fed-batch fermentation in a chemically defined medium. Initiation of the feed stream precedes a growth-limited phase in which plasmid DNA is amplified. The fermentation is only maximally productive for a small fraction of E. coli transformants designated as high-producers, while the predominant low-producer population does not amplify plasmid DNA. In experiments undertaken to probe this phenomenon, transposition of the 768-bp E. coli insertion sequence IS1 into an HIV DNA vaccine vector was observed in several low-producer clones. IS1 was found to insert in or near the neomycin resistance gene in nearly a dozen unique sites from within a single population of plasmid molecules. The fraction of IS1-containing plasmids within several clones was determined by quantitative polymerase chain reaction and was found to increase with increasing cultivation time in the chemically defined medium. Because transposition into an antibiotic-resistance gene is unlikely to affect plasmid amplification, the genomes of high- and low-producers of three different HIV DNA vaccine vectors were subsequently profiled by restriction fragment length polymorphism analysis. In all three cases, IS1 insertional mutations were found in the genomes of the predominant low-producers, while the genomes of the high-producers were indistinguishable from untransformed cells. The insertions reside on similarly sized fragments for two of the low-producer clones, and the fragment size is smaller for the third clone. The third clone also produces much less plasmid DNA than a typical low-producer. The results suggest the presence of an IS1 insertional mutation that affects plasmid replication and amplification, possibly in a position-dependent manner.