Acadesine-Induced Apoptosis in CLL

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[4822] Mechanism of Acadesine-Induced Apoptosis in B-Cell Neoplasms.

Session Type: Publication Only

F. Santidrián, Clara Campàs, Llorenç Coll-Mulet,

Iglesias-Serret, Ana M. Cosialls, Mercé Defrias, Domindo,

Alberto Fernandez de Sevilla, Pons, Joan Gil Dept. Ciències

Fisiològiques II, IDIBELL-Universitat de Barcelona, L'Hospitalet de

Llobregat, Barcelona, Spain; Servei d'Hematologia, IDIBELL-Hospital

Universitari de Bellvitge, L'Hospitalet de Llobregat, Barcelona,

Spain; Dept. Hematologia Clínica, IDIBELL-Institut Catala

d'Oncologia, L'Hospitalet de Llobregat, Barcelona, Spain

Mature B-cell neoplasms include B-cell chronic lymphocytic leukemia

(B-CLL), follicular lymphoma (FL), mantle cell lymphoma (MCL) and

splenic marginal zone B-cell lymphoma (SMZL), among others.

We found that acadesine, 5-aminoimidazole-4-carboxamide (AICA)

riboside, induced apoptosis in B-cell neoplasms and in normal B

lymphocytes, but FL samples were resistant. T cells from these

patients or from healthy donors were not affected (Campas et al.

Blood 101: 3674, 2003; Campas et al. Leukemia 19: 292, 2005).

We have studied the mechanism of acadesine-induced apoptosis.

Acadesine uptake and phosphorylation to ZMP are necessary to induce

apoptosis. The best known molecular target of ZMP described to date

is adenosine monophosphate-activated protein kinase (AMPK).

We have analyzed the expression of LKB1, an AMPKK, AMPK isoforms and

related proteins in B-CLL cells. B-CLL cells express LKB1, the & #945;1

catalytic isoform of AMPK and both the & #946;1 and & #946;2 isoforms of the

& #946;

regulatory subunit, but do not express the & #945;2 isoform.

Moreover, the AMPK related protein Snark is expressed in B-CLL

cells, while Melk and Ark5 are not. Incubation of B-CLL, MCL, SMZL

cells with acadesine induces phosphorylation in Thr172 and

activation of AMPK, which correlates with induction of apoptosis.

Acadesine enters FL cells as it induces phosphorylation of AMPK,

however FL cells are resistant to acadesine-induced apoptosis.

Moreover, phenformin and metformin induce AMPK phosphorylation but

not induce apoptosis in B-CLL cells. The phosphorylation of AMPK is

not sufficient for induction of apoptosis by acadesine in B-cell

neoplasms.

In B-CLL cells, CD40L or TPA, but not IL-4 or SDF1 inhibit acadesine-

induced apoptosis. Acadesine inhibit neither AKT phosphorylation

induced by TPA, IL-4, SDF1 or CD40L nor basal AKT phosphorylation.

Finally, acadesine induces a conformational change in Bax protein,

and citochrome c release to cytosol which is not block by ZVAD.fmk.

In conclusion, although further studies are necessary to elucidate

the mechanism of acadesine-induced apoptosis, we propose that

acadesine may provide an effective treatment for mature B-cell

neoplasms such as B-CLL, MCL and SMZL.