Low Expression of T/NK-Cell Signature Predicts Poor Survival in Patients with Primary Testicular and Diffuse Large B-Cell Lymphoma

Primary testicular lymphoma (PTL) is a rare and aggressive disease accounting for 1% of malignant lymphomas. Majority of the PTLs are diffuse large B-cell lymphomas (DLBCL). Recently, the impact of tumor microenvironment (TME) and limited immune surveillance on the lymphoma pathogenesis and survival has been recognized. Here, we aimed to characterize cellular and molecular immunological profiles in PTL, and associate the findings with outcome.

We used NanoString digital gene expression profiling with the PanCancer Immune panel to assess the expression of 770 immune response genes in tumor tissue of 60 patients with PTL. RNA-sequencing data from a cohort of 96 patients with primary DLBCL was used to validate the findings.

Unsupervised hierarchical clustering revealed clusters of genes with differential expression between the PTL patients. The clusters were enriched for genes related to T-cell and natural killer (NK) cell markers and signaling (e.g. CD3, CD4, CD8, ITGB2, PRF1, GZMA/B/H/M/K), as well as cytokine signaling (e.g. IL4, IL9, IL17A/B, TNFSF11, CXCR1, CCL28). Interestingly, the group of patients with low expression of T/NK-cell signature genes had a significantly worse progression-free survival (5-year PFS 33% vs. 65%, p=0.012) and overall survival (5-year OS 33% vs. 67%, p=0.004), as compared to the other patients. In Cox multivariate analysis with international prognostic index (IPI), T/NK-cell signature retained independence for prediction of better PFS and OS (RR=0.356, p=0.014 and RR=0.306, p=0.006, respectively). The signature was identified also in a cohort of 96 patients with primary DLBCL, but not in Hodgkin lymphoma. Multiplex immunohistochemistry confirmed lower percentage of CD3+, CD3+CD4+, and CD3+CD8+ lymphocytes in the tumor tissue of the group of PTL patients with poor prognosis (11.8% vs. 24.1%, 5.0% vs. 15.6%, and 4.6% vs. 12.3%, respectively), and association of their higher amount with favorable PFS and OS. Moreover, the RNA level expression of MHC class I and II genes was significantly lower in the poor prognosis group.

In conclusion, our results demonstrate that loss of T/NK cell signature and MHC class I and II gene expression are associated with high risk of recurrence and death in patients with PTL and DLBCL. They further highlight the importance of the immune escape as a mechanism of treatment resistance.