Expression of the human germinal center-associated lymphoma (HGAL) protein identifies a subset of classic Hodgkin lymphoma of germinal center derivation and improved survival

Abstract

The human germinal-center-associated lymphoma (HGAL) gene and its cognate protein are expressed in a germinal center (GC)-specific manner. Its expression in classic Hodgkin lymphoma (cHL) prompted us to address whether HGAL expression could distinguish biologically distinct subgroups of cHL. Tissue microarrays from 145 patients treated with curative intent showed HGAL staining in 75% and was closely correlated with MUM1/IRF4 (92%) expression. BCL6 (26%), CD10 (0%), BCL2 (31%), Blimp1 (0.02%), and Epstein-Barr virus (EBV) (20%) showed no specific correlation; neither did phospho-STAT6, a key mediator of IL-4 and IL-13 signaling that induces HGAL and is implicated in cHL pathogenesis. In our study cohort, the 5-year overall survival (OS) correlated with young age (less than 45 years, P < .001), low stage (stage I and II, P = .04), and low International Prognostic Score (P = .002). In univariate analysis, HGAL expression was associated with improved OS (P = .01) and failure-free survival (FFS) (P = .05) but was not independent of other factors in multivariate analysis of OS or FFS. The expression of the GC-specific marker HGAL in a subset of cHL suggests that these cHLs retain characteristics of GC-derived lymphomas. The association with improved OS in univariate but not multivariate analysis suggests that HGAL expression is related to known clinical parameters of improved survival.

Figure 1

HGAL protein expression in classic Hodgkin lymphoma. The spectrum of HGAL staining in cHL cases is shown. Staining is localized to the cytoplasm of large atypical cells. Staining in more than 5% but less than 30% of Hodgkin cells was defined as weak, whereas staining in 30% or more Hodgkin cells was defined as strong.

Figure 2

Representative immunostains and EBV expression in classic Hodgkin lymphoma. (A) Typical examples of TMA cores of cHL stained for BCL6, CD10, BCL2, MUM1/IRF4, and Blimp1 and in situ hybridization for EBV EBER RNA are shown. (B) Hierarchic cluster analysis of immunohistologic and in situ hybridization data shows that HGAL clusters with MUM1/IRF4 on 1 branch of the dendrogram (orange) but not with BCL2, CD10, and BCL6 (blue) or with the 2 EBV-specific markers, LMP2A and EBER (purple), which cocluster with each other.

Figure 3

Cytokine signaling and pSTAT6 in classic Hodgkin lymphoma. (A) Enriched peripheral-blood lymphocytes stimulated with 100 U/mL IL-4, 50 ng/mL IL-10, 100 U/mL IL-2, 10 ng/mL IL-13, or a combination of IL-4 and IL-13 for 6 hours are shown. Only IL-4 and IL-13 induced HGAL mRNA expression, and the combination of IL-4 and IL-13 resulted in a slightly additive induction of HGAL mRNA expression. Error bars indicate SD among 3 experiments. (B) Hierarchic cluster analysis shows that pSTAT6 expression coclusters with HGAL and MUM1/IRF4 on the same branch of the dendrogram (orange), indicating a similar pattern of staining for these 3 proteins across the 145 cHL cases.

Figure 4

HGAL protein expression correlates with overall survival. (A) HGAL protein expression correlates with overall survival (P = .01). (B) HGAL protein expression correlates with improved failure-free survival (P = .05).