Galectin-1 Serum Levels Reflect Tumor Burden and Adverse Clinical Features in Hodgkin Lymphoma

Abstract 51

Galectin-1 (Gal1) is a member of a highly conserved family of carbohydrate-binding proteins that modulate innate and adaptive immune responses and foster tumor immune escape. Through the selective recognition of specific cell-surface glycans (Gal-beta1-4-NAcGlc [N-acetyllactosamine] units on the branches of N- or O-linked glycans), Gal1 induces the apoptosis of Th1 and cytotoxic T cells. Th2 cells have different patterns of sialylation of cell-surface glycoproteins, lack Gal1 ligands, and resist Gal1-induced cell death. Regulatory T (Treg) cells are also resistant to Gal1-mediated apoptosis. In addition, Gal1 promotes hypoxia-driven tumor angiogenesis.

Primary Hodgkin lymphomas (HLs) include small numbers of malignant Reed-Sternberg cells within a Th2/Treg-skewed inflammatory infiltrate. In previous studies, we found that Reed-Sternberg cells overexpress Gal1, which selectively kills Th1 and cytotoxic T cells and promotes the immunosuppressive Th2/Treg-predominant HL microenvironment. In HLs, which exhibit constitutive AP-1 activation, Gal1 overexpression is driven in large part by an AP-1-dependent enhancer.

Given the immunosuppressive function of Gal1, we reasoned that the secreted protein might be a potent marker of disease activity and a novel therapeutic target. We previously developed a panel of Gal1 monoclonal antibodies and demonstrated the utility of Gal1 as a diagnostic marker of AP-1-dependent lymphoid malignancies. A potent neutralizing Gal1 antibody also protected Th1 and cytotoxic T cells from Gal1-induced apoptosis, abrogated Gal1-associated tumor angiogenesis and limited the growth of Gal1+ tumors in vivo.

We have now developed a sandwich ELISA to assess the utility of Gal1 as a serum marker of disease burden in HL. After establishing the sandwich ELISA with purified recombinant Gal1 and the newly developed Gal1 antibodies, we assessed the levels of serum Gal1 in 15 healthy normal donors and 315 newly diagnosed, previously untreated HL patients from the German Hodgkin Study Group. The HL patients were enrolled on 3 tailored, risk-adapted clinical trials: HD13 for early-stage disease (clinical stage [CS] IA-IIB) with no risk factors, 94 pts); HD 14 for early stage disease with risk factors (CS I-IIA with large mediastinal mass, extranodal disease, elevated ESR or > 3 nodal areas and CS IIB with elevated ESR or > 3 nodal areas, 90 pts); and HD18 for bulky localized or advanced stage disease (CS IIB with bulky mediastinal involvement and/or extranodal involvement and CS III or IV, 131 pts).

Serum Gal1 levels were significantly elevated in HL patients in comparison to normal controls (median value 2.3 X higher, p <.0001; 100% specificity and 78% sensitivity with a cut-off value of ∼ 50 ng/ml). HL patients on the clinical trial for early-stage low-risk patients (HD13) had significantly lower Gal1 levels than patients on either HD14 or HD18 (p =.0006).

We next evaluated the potential association of Gal1 serum levels with Ann Arbor stage and B-symptoms, two major determinants for assigning HL pts to risk-adapted therapy. Gal1 levels were significantly higher in HL pts with advanced-stage disease (stage I/II vs. III/IV, p <.001) and B symptoms (absence vs. presence, p =.03).

We also assessed the potential association of Gal1 levels with individual clinical prognostic factors in the Hodgkin Lymphoma International Prognostic Score (IPS). In univariate analyses, Gal1 levels were highly correlated with the following clinical risk factors: extranodal involvement (p =.01); > 3 lymph node areas (p =.0001); elevated erythrocyte sedimentation rate (ESR) (p =.0015); albumin < 4 g/dl (p =.035); hemoglobin < 10.5 g/dl (p =.035); lymphoma count < 600 per mm or < 8% of white cell count (p =.015). Consistent with these observations, HL patients with an IPS score of >= 2 had significantly higher Gal1 levels than patients with an IPS of 0 or 1 (p =.007). Direct analyses of the association between Gal1 levels and outcome await completion of the ongoing HD18 clinical trial.

In conclusion, Gal1 serum levels are significantly associated with tumor burden and additional adverse clinical characteristics in newly diagnosed HL patients. Given the demonstrated role of Gal1 in tumor immune evasion and angiogenesis, analyses of circulating Gal1 levels may inform risk-adapted and targeted treatment strategies for HL patients.