Pitfalls - immunotherapy

Human autologous in vitro models of glioma immunogene therapy using B7-2,
GM-CSF, and IL12.

* Parney IF, * Farr-Jones MA, * Kane K, * Chang LJ, *
Petruk KC.

Division of Neurosurgery, Department of Surgery, 2D1.02 W.C. Mackenzie
Health Sciences Center, University of Alberta, Edmonton, Alberta, Canada
T6G 2R7.

BACKGROUND: Cancer immunogene therapy is based on vaccination with
radiated, autologous tumor cells transduced with immunostimulatory genes.
To help determine an optimal glioma immunogene therapy strategy, we
stimulated lymphocytes with autologous human glioma cells transduced with
B7-2 (CD86), granulocyte-macrophage colony-stimulating factor (GM-CSF),
and/or interleukin-12 (IL12).

METHODS: A human glioma-derived cell culture (Ed147.BT) was transduced
with B7-2, GM-CSF, and/or IL12 using retroviral vectors. Autologous
peripheral blood mononuclear cells (PBMC) were co-cultured with irradiated
gene-transduced tumor alone or a combination of radiated wild type and
gene-transduced cells. Peripheral blood mononuclear cells proliferation
was determined by serial cell counts. Peripheral blood mononuclear cells
phenotype was assessed by flow cytometry for CD4, CD8, and CD16.
Anti-tumor cytotoxicity was determined by chromium-51 (51Cr) release
assay.

RESULTS: Peripheral blood mononuclear cells cell numbers all decreased
during primary stimulation but tumor cells expressing B7-2 or GM-CSF
consistently caused secondary proliferation. Tumors expressing B7-2 and
GM-CSF or B7-2, GM-CSF, and IL12 consistently increased PBMC CD8+
(cytotoxic T) and CD16+ (natural killer) percentages. Interestingly,
anti-tumor cytotoxicity only exceeded that of PBMC stimulated with wild
type tumor alone when peripheral blood mononuclear cells were stimulated
with both wild type tumor and B7-2/GM-CSF- (but not IL12) transduced
cells.

CONCLUSIONS: PBMC proliferation and phenotype is altered as expected by
exposure to immunostimulatory gene-transduced tumor. However, transduced
tumor cells alone do not stimulate greater anti-tumor cytotoxicity than
wild type tumor. Only B7-2/GM-CSF-transduced cells combined with wild type
produced increased cytotoxicity. This may reflect selection of tumor
subclones with limited antigenic spectra during retrovirus-mediated gene
transfer.

PMID: 12195617 [PubMed - indexed for MEDLINE]

<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16628480&query_hl=6&itool=pubmed_docsum>

1: J Neurooncol. 2006 Apr 21; [Epub ahead of print] Related Articles,
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Technical hurdles in a pilot clinical trial of combined B7-2 and
GM-CSF immunogene therapy for glioblastomas and melanomas.

Parney IF, Chang LJ, Farr-Jones MA, Hao C, Smylie M, Petruk KC.

Department of Clinical Neurosciences, Southern Alberta Cancer Research
Institute, and Hotchkiss Brain Institute, University of Calgary, Calgary,
Alberta, Canada.

OBJECTIVE: Malignant glioblastomas and melanomas continue to have a
dismal prognosis despite advances in conventional therapy. This has led to
investigations of novel treatment strategies including immunogene therapy.
We report a pilot clinical trial of combined B7-2 and GM-CSF immunogene
therapy for gliomas and melanomas and discuss technical hurdles
encountered.

METHODS: Patients with recurrent malignant gliomas or medically refractory
melanomas were vaccinated with irradiated autologous tumor cells
transduced with B7-2 and GM-CSF genes using a retroviral vector. Patients
were monitored for toxicity, inflammatory/immune reactions, and clinical
status.

RESULTS: Vaccine preparation was attempted from 116 malignant glioma and
32 melanoma specimens. Adequate vaccines could only be prepared for five
glioblastoma and three melanoma patients. Six patients (three recurrent
glioblastomas and three melanomas) were actually vaccinated. Minor
toxicities included flu-like symptoms (3/6), injection site erythema
(4/6), and asymptomatic elevations in liver enzymes (3/6). Most patients
showed evidence of an inflammatory response but specific anti-tumor
immunity was not demonstrated. All six patients have died, although three
patients with minimal residual disease at treatment had prolonged
recurrence-free intervals after vaccination.

CONCLUSIONS: Combined B7-2 and GM-CSF immunogene therapy for glioblastomas
and melanomas using autologous tumor cells has many technical pitfalls
hindering large scale application and evaluation. As a result, this pilot
study was too limited to draw meaningful conclusions regarding safety or
anti-tumor immunity.

While immunotherapy has been promising in pre-clinical studies, alternate
strategies will be required to bring these benefits to patients.

PMID: 16628480 [PubMed - as supplied by publisher]

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