ZAP-70 is Strongest Independent Prognositc Indicator in CLL

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[1197] Spontaneous Apoptosis and Proliferation Predict Disease

Progression within ZAP-70 Negative B-Cell Chronic Lymphocytic

Leukemia (B-CLL). Session Type: Poster Session 355-I

Giovanni Del Poeta, Ilaria Del Principe, Pasquale Niscola, Luca

Maurillo, o Venditti, Francesco Buccisano, Irno Consalvo,

Carla Mazzone, Paola Panetta, Massimo Degan, Irene Pasqua,

Bruno, Valter Gattei, Francesco Lo Coco, Amadori Hematology,

University Tor Vergata, Roma, Italy; Clinical and Experimental

Hematology, CRO, IRCCS, Aviano (PN), Italy

Inhibition of spontaneous apoptosis and upregulation of the anti-

apoptotic protein bcl-2 define clinical prognosis in B-CLL. However,

increasing evidence exists that disease progression (DP) relies upon

a proliferating pool of cells in lymph nodes and bone marrow which

might feed the accumulating pool in the blood. Moreover, unmutated

immunoglobulin VH genes predict for a rapid DP and an inferior

overall survival.

Unmutated B-CLL cells express ZAP-70 protein kinase associated with

an early DP risk. The availability both of rapamycin or proteasome

inhibitors effective against proliferating cells and bcl-2 targeting

drugs incited us to evaluate the impact of proliferation and

apoptosis pathways on B-CLL prognosis.

The primary aims of our study were: 1) to determine progression-free

survival (PFS) upon apoptosis/proliferation and ZAP-70 expression; 2)

whether apoptosis/proliferation could predict varied outcome within

ZAP-70 subgroups; and finally 3) whether ZAP-70 and

apoptosis/proliferation were independent prognostic factors.

Therefore, we investigated 249 pts, median age 64 years, almost all

belonging to the intermediate Rai stage. ZAP-70 was quantified by a

multicolor flow cytometric method. Bcl-2 (Bcl-2B/T) was determined

dividing mean fluorescence intensity (MFI) of CD19+B-CLL cells by MFI

of T-cells. CD71 was used as a measure of proliferation in

percentage. Combining Bcl-2B/T with CD71 (Bcl2CD71) we enucleated

three subgroups: 1) Bcl2CD71- [low proliferation (CD71<8%) and high

apoptosis (Bcl-2B/T<1.6)]; 2) Bcl2CD71+ [high proliferation (CD71>8%)

and low apoptosis (Bcl-2B/T>1.6)]; and 3) Bcl2CD71+/- [low

proliferation/low apoptosis or high proliferation/high apoptosis].

ZAP-70+ B-CLL pts were 87/249 (35%).

We found significant associations either between lower ZAP-70 and

lower Bcl-2B/T (p=0.0008) or lower ZAP-70 and Bcl2CD71- (p=0.0007),

showing that low ZAP-70 levels were characterized by high apoptosis

and low proliferation.

With regard to clinical outcome, a significant shorter PFS was

observed in ZAP-70+ pts (6% vs 58% at 12 years; p<0.00001) and in

Bcl2CD71+ pts (10% vs 56% at 12 years; p<0.00001). The Bcl2CD71+/-

subgroup showed an intermediate outcome (30% at 12 years).

To further explore the prognostic impact of Bcl2CD71 index, we

investigated its expression within ZAP-70+ (87) and ZAP-70 negative

(162) pts. As a matter of fact, Bcl2CD71 index was not able to

identify different prognosic subsets within ZAP-70+ pts, because all

these cases presented a similar short PFS. On the contrary, Bcl2CD71

clearly identified two subsets at different PFS within the ZAP-70

negative subgroup (73% for Bcl2CD71- pts vs 29% for Bcl2CD71+ pts at

12 years, p=0.00007).

In multivariate analysis of PFS, ZAP-70 resulted to be the strongest

independent prognostic factor (p=0.00002). However, the

apoptotic/proliferative index Bcl2CD71 was very useful to identify

our pts at different PFS within the ZAP-70 negative subgroup. In

conclusion, ZAP-70 negative B-CLL represents a large and clinically

heterogeneous population with a variable DP and the determination of

the amount of apoptosis combined with the proliferation, could allow

us both to distinguish early progressive pts and to take timely

therapeutic decisions.