Interleukin-2 therapy for advanced chronic myeloid leukemia

Targeting the silent minority: emerging immunotherapeutic strategies for eradication of malignant stem cells in chronic myeloid leukaemia

Standard allogeneic stem cell transplantation (alloSCT) has provided a cure for chronic myeloid leukaemia (CML) over the last 25 years, but is only an option for a minority of patients. It was hoped that the introduction of imatinib mesylate (IM), a specific tyrosine kinase inhibitor that targets the Bcr-Abl oncogene product, would provide long-term remission or even cure for those patients without a donor, but studies have shown that IM does not eliminate leukaemic stem cells in CML patients. To overcome this problem of molecular persistence, research is underway to combine reduced intensity stem cell transplant or non-donor-dependent immunotherapies with IM with the aim of increasing cure rate, reducing toxicity and improving quality of life. The alternative approach is to combine IM or second-generation agents with other novel drugs that interrupt key signalling pathways activated by Bcr-Abl. This article will focus on the latest immunotherapy and molecularly targeted therapeutic options in CML and how they may be combined to improve the outcome for CML patients in the future.

Transgenic interleukin 2 secreted by CML dendritic cells stimulates autologous T(H)1 T cells

BACKGROUND

We investigated if dendritic cells (DC), derived from patients suffering from chronic myeloid leukemia (CML) could be modified by recombinant replication-defective adenoviruses to express functional interleukin 2 (IL-2). Such modification might confer onto antigen-presenting cells the ability to stimulate expansion of effector cells.

METHODS

To quantify the infection efficiency of CML dendritic cells (CML-DC) by recombinant adenovirus, we measured the expression of green fluorescent protein (GFP) gene contained in the virus. In CML-DC infected with an adenovirus containing the IL-2 gene, we evaluated their ability to secrete IL-2 and stimulate proliferation of autologous T cells.

RESULTS

Uninfected CML-DC and normal DC secreted similar amounts of IL-12 and stimulated similarly efficient autologous mixed leukocyte reaction. Immature CML-DC infected by an adenovirus containing the gene for IL-2 secreted large amounts of IL-2 and stimulated proliferation of autologous T cells more efficiently than the corresponding CML-DC alone. High levels of interferon eta, but not of IL-4, in cell culture supernates indicated that the proliferating cells were T(H)1. Infected mature CML-DC were more effective than infected immature CML-DC, showing that T cell stimulation by mature DC and by IL-2 was additive.

DISCUSSION

CML-DC can be modified genetically and functionally by recombinant replication-defective adenoviruses, providing new possibilities for clinical trials in dendritic cell-based immunotherapy.

Current Treatment of Chronic Myeloid Leukemia

We are entering an exciting era in the management of chronic myeloid leukemia (CML). This, in part is related to our considerable understanding of the molecular lesion associated with the disease-arguably the best characterized of any malignancy. Although allogeneic hematopoietic cell transplantation remains the sole potentially curative therapy at present, newer agents such as the tyrosine kinase inhibitor STI571 show promise and may eventually replace less specific cytotoxic therapy. This review focuses on the numerous options currently available for treating CML and includes a treatment algorithm.