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Increased sensitivity to cytosine arabinoside in human leukemia by c-raf-1 antisense oligonucleotides
T Funato1, K Kozawa, S Fujimaki
1Division of Molecular Diagnostics, Department of Clinical Medicine, Tohoku University, School of Medicine, Seiryoumachi 1-1, Aoba-ku, Sendai 980-8574, Japan. tfunato@mail.cc.tohoku.ac.jp
Abstract:
c-raf-1, a cytoplasmic serine/threonine protein kinase, plays an important role in mitogen- and damage-responsive cellular signal transduction pathways. Expression of c-raf-1 modifies cell growth, proliferation and survival. Although expression of c-raf-1 has been studied in several tumors, the role of c-raf-1 in leukemia is so far unclear. We examined the expression of c-raf-1 in the human leukemia cell lines U937 and K562, and in a cytosine arabinoside (Ara-C)-resistant cell line (K562AC) derived from K562. Expression of c-raf-1 was increased in U937 and in Ara-C-resistant K562AC cells compared with the parental cells. We then investigated whether inhibition of c-raf-1 expression by antisense oligonucleotides increases the sensitivity to Ara-C in U937 and K562AC cells. Antisense oligonucleotides for c-raf-1 inhibited expression of c-raf-1 mRNA, but did not affect cell growth and increased sensitivity to Ara-C but not to other drugs such as adriamycin, VP-16 or vincristine. These results suggest that c-raf-1 is one of the factors involved in Ara-C resistance in leukemia and lend weight to the case for development of anti-cancer therapeutics involving oncogene-targeted antisense oligonucleotides.
Insights
Increased c-raf-1 expression contributes to leukemia drug resistance. Inhibiting c-raf-1 with antisense oligonucleotides enhanced sensitivity to cytosine arabinoside (Ara-C) in leukemia cells.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Signaling
Background:
- c-raf-1 is a serine/threonine protein kinase involved in cellular signal transduction, growth, proliferation, and survival.
- The role of c-raf-1 in leukemia remains unclear, despite its study in other tumors.
Purpose of the Study:
- To investigate the expression of c-raf-1 in human leukemia cell lines.
- To determine if inhibiting c-raf-1 enhances sensitivity to cytosine arabinoside (Ara-C) in leukemia cells.
Main Methods:
- Examined c-raf-1 expression in U937 and K562 leukemia cell lines, including an Ara-C-resistant K562AC derivative.
- Utilized antisense oligonucleotides to inhibit c-raf-1 expression.
- Assessed sensitivity to Ara-C and other chemotherapeutic agents (adriamycin, VP-16, vincristine).
Main Results:
- c-raf-1 expression was elevated in U937 and K562AC cells compared to parental cells.
- Antisense inhibition of c-raf-1 reduced c-raf-1 mRNA levels without impacting cell growth.
- Inhibition of c-raf-1 increased sensitivity to Ara-C but not to adriamycin, VP-16, or vincristine.
Conclusions:
- c-raf-1 is implicated as a factor contributing to Ara-C resistance in leukemia.
- Targeting c-raf-1 with oncogene-targeted antisense oligonucleotides shows potential for novel anti-cancer therapeutics.