Biomedical subjects

Kay A O Ellem

Publications and source records attributed to Kay A O Ellem.

6 recordsLinked to original sources

PubMed2006

Facultative or obligate anaerobic bacteria have the potential for multimodality therapy of solid tumours.

Recent understanding of the unique pathology of solid tumours has shed light on the difficult and disappointing nature of their clinical treatment. All solid tumours undergo angiogenesis that results in biological changes and adaptive metabolisms, i.e. formation of defective vessels, appearance of hypoxic areas, and emergence of an heterogeneous tumour cell population. This micro-milieu provides a haven for anaerobic bacteria. The strictly anaerobic clostridia have several advantages over other facultative anaerobes such as salmonella or lactic acid-producing, Gram-positive, obligate, anaerobic bifidobacteria. Both pathogenic and non-pathogenic clostridia have been demonstrated to specifically colonise and destroy solid tumours. Early trials of non-pathogenic strains in humans had shown plausible safety. Genetic modifications and adaptation of pathogenic and non-pathogenic strains have further created improved features. However, these manipulations rarely generate strains that resulted in complete tumour control alone. Combined modalities of therapies with chemo and radiation therapies, on the other hand, often perform better, including 'cure' of solid tumours in a high percentage of animals. Considering that clostridia have unlimited capacities for genetic improvement, we predict that designer clostridia forecast a promising future for the development of potent strains for tumour destruction, incorporating mechanisms such as immunotherapy to overcome immune suppression and to elicit strong anti-tumour responses.

Angiogenesis Inhibitors↗

PubMed2006

Immunological characteristics correlating with clinical response to immunotherapy in patients with advanced metastatic melanoma.

Current treatment options for advanced metastatic melanoma are limited to experimental regimen that provide poor survival outcomes. Immunotherapy is a promising alternative and we recently reported a clinical trial in which 6 out of 19 patients enrolled had objective clinical responses to a fully autologous melanoma/dendritic cell vaccine. The mechanism of the vaccine is not well understood, but we hypothesized that general immunocompetence may be a determinant of clinical response. We therefore examined the immune status of an expanded series of 21 patients who displayed varying clinical responses to the melanoma/dendritic cell vaccine. Immunocompetence was assessed using in vitro assays of lymphocyte function: survival, proliferation and cytokine responses to mitogen stimulation as well as T-cell receptor zeta expression and lymphocyte subset analysis. Although lymphocytes from patients mostly performed comparably to age-matched and sex-matched controls, in some assays we identified significant differences between complete clinical responders and other patients, both before and following vaccination. Surprisingly, before vaccination, only lymphocytes from clinical responder patients showed impaired in vitro survival. Following vaccination, T lymphocyte survival improved and cells recovered their ability to produce the Th1-associated cytokines TNF and IFN-gamma in response to anti-CD3 stimulation in vitro. No increase in Th1 cytokine production was observed in lymphocytes from patients who experienced partial clinical responses or progressive disease. We conclude that, before vaccination, patients who go on to have complete responses have immune characteristics suggestive of high cell turnover and low Th1-associated cytokine production, and that these can be reversed with vaccination. These results have potential implications for future immunotherapeutic strategies.

Adult↗

PubMed2005

Gene transfer to dendritic cells induced a protective immunity against melanoma.

Lentiviral vectors have shown promises for efficient gene transfer to dividing as well as nondividing cells. In this study, we explored lentiviral vector-mediated, the entire mTRP-2 gene transfer and expression in dendritic cells (DCs). Adoptive transfer of DCs-expressing mTRP-2 (DC-HR'CmT2) into C57BL/6 mouse was also assessed. Dendritic cells were harvested from bone marrow and functional DCs were proved by allogeneic mixed lymphocyte reaction. Lentiviral vectors were produced by transient transfection of 293T cells. Transduction of DCs was proved by marker gene expression and PCR and RT-PCR amplification. Implantation of the transduced DCs, depletion of immune cells as well as the survival of the mice after tumour challenge were investigated. High efficiency of gene transfer into mature DCs was achieved. The high level expression of the functional antigen (TRP-2) and induction of protective immunity by adoptive transfer of TRP-2 gene modified DCs were demonstrated. In vivo study showed a complete protection of mice from further melanoma cell challenge. In comparison, only 83% of mice survived when mTRP-2 peptide-pulsed DCs were administered, suggesting the generation of specific protection. Together, these results demonstrated the usefulness of this gene transfer to DC approach for immunotherapy of cancer and indicated that using tumour associated antigens (TAAs) for gene transfer may be potentially beneficial for the therapy of melanoma.

Adoptive Transfer↗

PubMed2005

Search for "weapons of mass destruction" for cancer -- immuno/ gene therapy comes of age.

The complexity of a cancer, such as cell heterogeneity, and the existence of hypoxia, stromal cells and stem cells has so far prevented successful development and treatment of patients suffering from the later stages of cancers. At present, the use of conventional therapies, such as chemo/radio therapy is limited, and only therapies that are focused on utilizing the patient's immune response to combat against the disease appear to be the most reliable and promising. Two decades ago, cytokines were discovered to be able to activate the immune systems and mount an anti-tumour response. Then, dendritic cells were hailed as the most significant regulators of immunity and are employed in a variety of cancer management schemes. This review introduces current development in the field, focusing on combination of the components of the rapidly growing fields of immunotherapy and gene transfer/therapy, providing useful and significant detailed information for readers of cellular and molecular immunology.

Animals↗

PubMed2004

Microarray expression profiling in melanoma reveals a BRAF mutation signature.

We have used microarray gene expression profiling and machine learning to predict the presence of BRAF mutations in a panel of 61 melanoma cell lines. The BRAF gene was found to be mutated in 42 samples (69%) and intragenic mutations of the NRAS gene were detected in seven samples (11%). No cell line carried mutations of both genes. Using support vector machines, we have built a classifier that differentiates between melanoma cell lines based on BRAF mutation status. As few as 83 genes are able to discriminate between BRAF mutant and BRAF wild-type samples with clear separation observed using hierarchical clustering. Multidimensional scaling was used to visualize the relationship between a BRAF mutation signature and that of a generalized mitogen-activated protein kinase (MAPK) activation (either BRAF or NRAS mutation) in the context of the discriminating gene list. We observed that samples carrying NRAS mutations lie somewhere between those with or without BRAF mutations. These observations suggest that there are gene-specific mutation signals in addition to a common MAPK activation that result from the pleiotropic effects of either BRAF or NRAS on other signaling pathways, leading to measurably different transcriptional changes.

Amino Acid Substitution↗

PubMed2003

Durable complete clinical responses in a phase I/II trial using an autologous melanoma cell/dendritic cell vaccine.

Advanced metastatic melanoma is incurable by standard treatments, but occasionally responds to immunotherapy. Recent trials using dendritic cells (DC) as a cellular adjuvant have concentrated on defined peptides as the source of antigens, and rely on foreign proteins as a source of help to generate a cell-mediated immune response. This approach limits patient accrual, because currently defined, non-mutated epitopes are restricted by a small number of human leucocyte antigens. It also fails to take advantage of mutated epitopes peculiar to the patient's own tumour, and of CD4+ T lymphocytes as potential effectors of anti-tumour immunity. We therefore sought to determine whether a fully autologous DC vaccine is feasible, and of therapeutic benefit. Patients with American Joint Cancer Committee stage IV melanoma were treated with a fully autologous immunotherapy consisting of monocyte-derived DC, matured after culture with irradiated tumour cells. Of 19 patients enrolled into the trial, sufficient tumour was available to make treatments for 17. Of these, 12 received a complete priming phase of six cycles of either 0.9x10(6) or 5x10(6) DC/intradermal injection, at 2-weekly intervals. Where possible, treatment continued with the lower dose at 6-weekly intervals. The remaining five patients could not complete priming, due to progressive disease. Three of the 12 patients who completed priming have durable complete responses (average duration 35 months+), three had partial responses, and the remaining six had progressive disease (WHO criteria). Disease regression was not correlated with dose or with the development of delayed type hypersensitivity responses to intradermal challenge with irradiated, autologous tumour. However, plasma S-100B levels prior to the commencement of treatment correlated with objective clinical response ( P=0.05) and survival (log rank P<0.001). The treatment had minimal side-effects and was well tolerated by all patients. Mature, monocyte-derived DC preparations exposed to appropriate tumour antigen sources can be reliably produced for patients with advanced metastatic melanoma, and in a subset of those patients with lower volume disease their repeated administration results in durable complete responses.

Adult↗