Preclinical evaluation of antisense bcl-2 as a chemosensitizer for patients with gastric carcinoma.
BACKGROUND
Because bcl-2 is a critical factor for anticancer drug-induced apoptosis, the authors conducted a preclinical evaluation of antisense (AS) bcl-2 as an enhancer of the chemotherapeutic effect in the treatment of patietns with gastric carcinoma.


METHODS
AS bcl-2 was used with 18-mer phosphorothiated oligonucleotides in the MKN-45 gastric carcinoma cell line. Drug sensitivity in vitro was evaluated using the methyl-thiazoldiphenyl tetrazolium assay, and antitumor effects in vivo were evaluated using the nude mouse xenograft. Apoptosis was determined with the terminal deoxyuridine triphosphate nick-end labeling assay. AS bcl-2 in vitro was treated with lipofectin, whereas it was administered intraperitoneally for 6 consecutive days twice every 2 weeks in vivo. Anticancer drugs were administered intraperitoneally four times per week.


RESULTS
bcl-2 was down-regulated to 60% of its initial value after treatment with 1.0 muM AS bcl-2 compared with the controls of random and mismatched oligonucleotides. Drug sensitivity to doxorubicin, cisplatin, and paclitaxel (TXL) was increased 3-4-fold when used in combination with AS bcl-2, which was determined with 50% inhibitory concentration values, compared with the control group. Increased drug sensitivity was associated with apoptosis, which increased in Bax and poly-adenosine diphosphate (ADP-ribose) polymerase and decreased in phosphorylated Akt (pAkt). The antitumor effect of cisplatin and TXL in vivo was enhanced significantly in combination with AS bcl-2. Down-regulation of bcl-2 was observed on Day 4 after the treatment with AS bcl-2.


CONCLUSIONS
Combination treatment with AS bcl-2 and anticancer drugs, including cisplatin and TXL, may be a new strategy for enhancing chemotherapeutic effects in the treatment of gastric carcinoma.
Department of Surgical Oncology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima, Japan. rkim@hiroshima-u.ac.jp
Ryungsa
R
Kim
Manabu
M
Emi
Kazuaki
K
Tanabe
Tetsuya
T
Toge
D000818:Animals; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D015153:Blotting, Western; D045744:Cell Line, Tumor; D016373:DNA, Antisense / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm; D006801:Humans; D020287:In Situ Nick-End Labeling; D051379:Mice; D008819:Mice, Nude; D011065:Poly(ADP-ribose) Polymerases / Q000187:drug effects / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000187:drug effects / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D013274:Stomach Neoplasms / Q000188:drug therapy*; D051028:bcl-2-Associated X Protein
D000970:Antineoplastic Agents; C494826:BAX protein, human; C494827:Bax protein, mouse; D016373:DNA, Antisense; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D011065:Poly(ADP-ribose) Polymerases; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt