Combination with an antisense oligonucleotide synergistically improves the antileukemic efficacy of erucylphospho-N,N,N-trimethylpropylammonium in chronic myeloid leukemia cell lines.

The aim of this study was to enhance the antileukemic efficacy of the alkylphosphocholine erucylphospho-N,N,N-trimethylpropylammonium (ErPC3) in chronic myeloid leukemia (CML)-derived cell lines by a bcr-directed antisense oligonucleotide (ASO-bcr). The mechanism was substantiated by Western blotting of the BCR-ABL expression level of CML cells, and the efficacy was substantiated by inhibition of colony formation compared with normal hematopoietic cells. The clonogenicity of K-562 cells expressing high levels of p210(BCR-ABL) was inhibited significantly by the ASO-bcr (T/C%, 30; P < 0.05) but not by ErPC3 (T/C%, 70). Combined sequential exposure to ErPC3 and the ASO-bcr, however, inhibited synergistically colony growth (T/C%, 3; P < 0.01). The colony growth of BV-173 cells expressing lower levels of p210(BCR-ABL) than K562 cells was inhibited to a greater extent by the ASO-bcr (T/C%, 15; P < 0.01). AR-230 cells that express high levels of p230(BCR-ABL) showed an intermediate decrease in colony formation in response to the ASO-bcr (T/C%, 20; P < 0.05). BCR-ABL levels of BV-173, CML-T1, and LAMA-84 cells were reduced in response to the ASO-bcr, as evidenced by Western blot. However, K-562 and AR-230 cells showed reduced BCR-ABL expression only after repeated treatment. ErPC3 and the ASO-bcr did not reduce colony formation (CFU-GM) of normal mouse bone marrow cells from long-term bone marrow cell cultures; instead, ErPC3 stimulated colony formation (P < 0.05) and did not induce chromosomal aberrations in mouse bone marrow. In conclusion, the combination of ErPC3 with a suitable antisense oligonucleotide inhibited synergistically colony formation of CML cell lines without damaging normal cells and thus might have a bearing on the purging of autologous hematopoietic transplants in CML patients.

Combination effects of alkylphosphocholines and gemcitabine in malignant and normal hematopoietic cells.

Cytosine arabinoside (ara-C) and 2',2'-difluorodeoxycytidine (Gem) were compared in leukemia cells, with Gem being more potent than ara-C. Gem was combined with hexadecylphosphocholine (HPC) or erucylphospho-N,N,N-trimethylpropanolamine (ErPC(3)) in resistant CML cells. Supra-additive effects were seen in K-562 cells after concomitant and sequential exposure of Gem followed by HPC. The reverse sequence resulted in antagonism. Both effects were more significant when HPC was exchanged for ErPC(3). Gem or HPC failed to induce DNA laddering in K-562 cells, but apoptotic signals were transferred by the Gem-exposed SKW-3 cytosolic fraction to K-562 nuclei. HPC did not increase the clastogenicity of Gem and counteracted its mitotic inhibition in murine bone marrow. Thus, the combination of Gem and an alkylphosphocholine is advantageous in terms of their complementary mode of action, resulting in increased cytotoxicity and lowered myelotoxicity.