Genetic Variations in Heparanase Gene (HPSE) Are Associated with Increased Risk of Graft Vs. Host Disease Following Allogeneic Hematopoietic Stem Cell Transplantation: Effect of Discrepancy Between Recipient and Donor.

Graft-versus-host disease (GVHD) is the most common cause of overall mortality and morbidity after HSCT. Heparanase, endo-â-glucuronidase that specifically cleaves the saccharide chains of heparan sulfate proteoglycans, is involved in the process of inflammation and release of heparan sulfate-bound chemokines, cytokines and bioactive angiogenic factors that are main players in the development of GVHD. Therefore, we investigated the possible association of HPSE gene SNPs with the risk of post HSCT GVHD and transplantation outcome.

Four hundred and fourteen patients with hematological malignancies and their HLA matched donors were included in the study. Genotyping of two HPSE gene SNPs rs4693608 and rs4364254 was carried out using PCR-RFLP-based analysis and allele-specific amplification.

Assessment of heparanase gene SNPs among healthy individuals demonstrated a significant correlation between HPSE gene SNPs and the expression level of heparanase, SNP rs4693608 being the most prominent (p=0.00043). This approach allowed distribution of all possible HPSE genotype combinations into three groups (LR, MR and HR) correlating with low, intermediate and high heparanase mRNA and protein expression levels. In the group of HSCT patients we found a highly significant correlation between HPSE gene SNPs rs4693608 and rs4364254, their combinations and risk of acute GVHD. The cumulative incidence of acute GVHD, grade II-IV, was 54.4% (95% CI 44.7-66.2) in the recipient group HR, while in recipient groups MR and LR, the cumulative incidences were 40.5% (95% CI 33.2-49.4) and 24.9% (95%CI 17.7-34.9), respectively (P=0.0001). Moreover, discrepancy between recipient and donor in these SNPs combinations significantly affected the risk of acute GVHD. Genotype combination LR in patients exerted a protective effect against GVHD regardless of the donor genotype combinations. Acute GVHD rates were highest when recipients possessed genotype combinations HR. correlating with high heparanase mRNA levels, while their donors possessed the MR or LR genotype combinations correlating with a lower heparanase mRNA level, (HR-MR and HR-LR pairs). The other combinations were associated with an intermediate risk. Therefore, we divided all recipient-donor pairs to three groups according to potential risk for acute GVHD development. The first group, LAGR, included three pairs with low risk of acute GVHD development (LR-LR, LR-MR, and LR-HR pairs). The second cohort, HAGR, contained pairs with high risk of acute GVHD development (HR-MR and HR-LR pairs). The third group, MAGR, consisted of pairs with moderate risk of acute GVHD development (MR-MR, MR-HR, MR-LR and HR-HR pairs). Cumulative rate of acute GVHD incidence was 71.2% (95% CI 58.2-87.0) in the HAGR group, 41.5% (95% CI 34.4-50.1) in the MAGR group, and 24.9% (CI 95% 17.7-34.9) in the LAGR group (÷2=29.3, P< 0.00001 for grade II-IV and ÷2=34.1, P< 0.00001 for grade III-IV). In addition, HPSE gene SNPs disclosed a correlation with extensive chronic GVHD, non-relapse mortality and overall survival. Multivariate analysis confirmed the independent effect of both host genotype and host-donor genotype risk groups.

The study demonstrated significant correlation between HPSE gene SNPs and heparanase expression levels and the risk of acute and extensive chronic GVHD. Our findings may imply the involvement of heparanase in the pathogenesis of GVHD. We speculate that secreted levels of cytokines and chemokines affected by heparanase are higher in patients possessing HR genotype in comparison to possessors of the MR and LR genotypes. Higher cytokine and chemokine signals originating from the patient activate donor T-cells and increase the risk of GVHD. When donor T-cells originated from a donor environment with lower heparanase levels as dictated by donor genotype LR/MR, the infusion into a high heparanase level environment may cause hyperactivation and an even higher risk of GVHD. This aggressive phenotype of donor T lymphocytes results in infiltration and destruction of patient tissues and GVHD development.

No relevant conflicts of interest to declare.