Original

A Synergistic Increase of Apoptosis
Utilizing Fas Antigen Expression
Induced by Low Doses of Anticancer Drug

Hidehiko AKIYAMA, PhD*1, Teruo INO, MD*2, Etsuko TOKUNAGA*3,
Itsurou KATSUDA, PhD*4 and Kohji EZAKI, MD*5

Anticancer drugs have been known to enhance both Fas receptor and Fas ligand expression on tumor cells. Recently, low doses of cytosine arabinoside(ara-C) were reported to enhance Fas antigen expression in the human myeloid leukemia cell line HL60. Here, we showed that low doses of ara-C(LD-ara-C) and etoposide(LD-VP-16) but not vincristine(LD-VCR) induce Fas expression in the human monocytic leukemia cell line U937. We determined the concentrations of ara-C, VP-16 and VCR as 10, 100 and 1 ng/ml, respectively. The ratios for Fas antigen expression induced in non-treated U937 by 24h incubations with ara-C, VP-16 or VCR were 1.90, 1.36 and 1.00, respectively. Utilizing the Fas antigen expression induced by low doses of anticancer drugs, we examined whether anti-Fas IgM monoclonal antibody(CH-11) combined with LD-ara-C, LD-VP-16 or LD-VCR enhances apoptosis. When CH-11 and LD-anticancer drug were added simultaneously, the ratios of annexin V positive cells were 67.8±2.4% with ara-C, 70.0±1.6% with VP-16 and 54.2±1.3% with VCR. Thus, the ratios of annexin V positive cells significantly increased when CH-11 was simultaneously added to the cells with ara-C(p＜0.0001) and VP-16(p＜0.0001), but not with VCR(p＝0.5559), compared with the sums of annexin V positive ratios of CH-11 and LD-anticancer drug added separately. We examined whether a broad-range caspase inhibitor(C.I.) can inhibit the Fas expression enhanced by LD-anticancer drugs. However, the Fas expression enhanced by LD-ara-C or LD-VP-16 was not inhibited by a broad-range caspase inhibitor. We demonstrated that apoptosis induced by LD-ara-C or LD-VP-16 is synergistically increased by the addition of CH-11 in U937.
[Rinsho Byori 51 : 733〜739, 2003]

【Key Words】Fas ligand(CD95/CD95L) system，apoptosis，cytosine arabinoside：ara-C，etoposide：VP-16，vincristine：VCR

Received March 3, 2003; accepted May 14, 2003
*1School of Hygiene, *2,3,5Department of Medicine,
*4College of Medical Technology, Fujita Health University School of Medicine, Toyoake 470-1192

E-mail :hakiyama@fujita-hu.ac.jp