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c-raf-1 depletion and tumor responses in patients treated with the c-raf-1 antisense oligodeoxynucleotide ISIS 5132
P J O'Dwyer1, J P Stevenson, M Gallagher
1Thomas Jefferson University, Kimmel Cancer Center, Philadelphia, Pennsylvania 19104, USA.
Abstract:
Abnormally regulated signaling through proliferative signal transduction pathways characterizes many of the common solid tumors. The best described of these involves potentially oncogenic proteins of the Ras family, which activate Raf proteins in the early steps of the mitogen-activated protein kinase cascade. ISIS 5132, a phosphorothioate antisense oligodexoynucleotide directed to the 3' untranslated region of the c-raf-1 mRNA, inhibits the growth of human tumor cell lines in vitro and in vivo in association with specific down-regulation of target message expression. Using a semiquantitative reverse transcription-PCR assay, we analyzed changes in c-raf-1 mRNA expression in peripheral blood mononuclear cells collected from patients with advanced cancers treated with ISIS 5132 as part of a clinical trial. Specimens were collected for analysis pretreatment and on days 3, 5, 8, and 15 of the first cycle and on day 1 of each subsequent cycle. We observed significant reductions of c-raf-1 expression from baseline by day 3 in 13 of 14 patients (P = 0.002). The time course and depletion of c-raf-1 message in peripheral blood mononuclear cells paralleled the clinical benefit in two patients. These findings demonstrate that ISIS 5132 specifically reduces target gene expression in treated patients and that peripheral blood mononuclear cells are suitable tissues for biomarker studies in future trials.
Insights
ISIS 5132, an antisense therapy, effectively reduces c-raf-1 mRNA in advanced cancer patients. This targeted approach shows promise for cancer treatment and biomarker studies.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacogenomics
Background:
- Aberrant signaling pathways, particularly involving Ras and Raf proteins, are hallmarks of common solid tumors.
- The c-raf-1 gene plays a crucial role in the mitogen-activated protein kinase cascade, a key pathway in cell proliferation.
- Targeting oncogenic signaling pathways is a critical strategy in cancer therapy.
Purpose of the Study:
- To evaluate the efficacy of ISIS 5132, an antisense oligonucleotide, in down-regulating c-raf-1 mRNA expression in patients with advanced cancers.
- To assess the changes in c-raf-1 mRNA levels in peripheral blood mononuclear cells (PBMCs) during ISIS 5132 treatment.
- To determine the suitability of PBMCs as a biomarker tissue for assessing drug efficacy in clinical trials.
Main Methods:
- A clinical trial was conducted involving patients with advanced cancers treated with ISIS 5132.
- Peripheral blood mononuclear cells were collected from patients at various time points before and during treatment.
- A semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) assay was used to measure c-raf-1 mRNA expression levels.
Main Results:
- ISIS 5132 treatment led to significant reductions in c-raf-1 mRNA expression from baseline by day 3 in 13 out of 14 patients (P = 0.002).
- The observed down-regulation of c-raf-1 mRNA in PBMCs paralleled the clinical benefit observed in two patients.
- The study demonstrated specific target gene expression reduction in patients receiving ISIS 5132.
Conclusions:
- ISIS 5132 effectively and specifically reduces c-raf-1 mRNA expression in patients with advanced cancers.
- Peripheral blood mononuclear cells are a suitable and accessible tissue for biomarker studies in future clinical trials involving antisense therapies.
- These findings support the potential of ISIS 5132 as a targeted cancer therapeutic and highlight the utility of PBMCs for monitoring drug activity.