Molecular and functional profiling identifies therapeutically targetable vulnerabilities in plasmablastic lymphoma.

Plasmablastic lymphoma (PBL) represents a rare and aggressive lymphoma subtype frequently associated with immunosuppression. Clinically, patients with PBL are characterized by poor outcome. The current understanding of the molecular pathogenesis is limited. A hallmark of PBL represents its plasmacytic differentiation with loss of B-cell markers and, in 60% of cases, its association with Epstein-Barr virus (EBV). Roughly 50% of PBLs harbor a MYC translocation. Here, we provide a comprehensive integrated genomic analysis using whole exome sequencing (WES) and genome-wide copy number determination in a large cohort of 96 primary PBL samples. We identify alterations activating the RAS-RAF, JAK-STAT, and NOTCH pathways as well as frequent high-level amplifications in MCL1 and IRF4. The functional impact of these alterations is assessed using an unbiased shRNA screen in a PBL model. These analyses identify the IRF4 and JAK-STAT pathways as promising molecular targets to improve outcome of PBL patients.

PD1/PD-L1 Expressions in Plasmablastic Lymphoma with Clinicopathological Correlation.

The activation of the programmed cell death one (PD1)/PD1 ligand (PD-L1) immune checkpoint pathway is a mechanism of immune evasion characterized by the upregulation of PD-L1 expression by tumor cells and by the tumor microenvironment. This activation leads to the inhibition of PD1-positive T cells and to a decrease in the anti-tumor immune response. Plasmablastic lymphoma (PBL) is an aggressive type of large B-cell lymphoma with limited studies on the frequency of PD1 and PD-L1 expressions and their clinical impact. As PBL is associated with immune suppression in immunocompromised individuals, we hypothesize that the PD1/PD-L1 axis may be relevant in this type of lymphoma. Our study demonstrates a subset of PBL cases with a higher PD-L1 expression by tumor cells [nPD-L1high, in 4 of 21 (19%) cases] and by tumor microenvironment [macrophages/stromal cells, sPD-L1high, in 9 of 21 (43%) cases]. While nPD-L1 expression showed no significant correlation with PD1 expression on tumor-infiltrating lymphocytes, or other clinicopathological parameters, it positively correlated with sPD-L1 expression. Moreover, patients with nPD-L1high had a tendency towards a shorter overall survival (median 9.3 vs. 25.5 months in nPD-L1low patients). In conclusion, our study provides a rationale to identify, by immunohistochemistry, a subset of nPD-L1high patients who may benefit from clinical trials of PD1/PD-L1 checkpoint blockade. Further studies on large cohorts are needed to investigate prognostic and predictive biomarkers for the PD1/PD-L1 pathway in PBL patients.

Cytokeratin expression in plasmablastic lymphoma - a possible diagnostic pitfall in the routine work-up of tumours.

AIMS: Plasmablastic lymphoma (PBL) is a rare aggressive B-cell lymphoma that frequently arises at extranodal sites in the setting of immunosuppression. The diagnosis of PBL is complex, owing to a frequent solid or cohesive growth pattern, and an often unusual immunophenotype. Several case reports have described cytokeratin (CK) expression in PBL, introducing a diagnostic pitfall. The aim of this study was to determine the frequency of CK expression in PBL in the largest series available to date. METHODS AND RESULTS: By using immunohistochemistry in a cohort of 72 PBLs, we identified CK8/18 positivity in 11 of 72 cases (15%) and AE1/3 positivity in six of 65 cases (9%), clearly contrasting with a control series of non-PBL aggressive B-cell lymphomas (one of 96 diffuse large B-cell lymphomas), as well as with data in the literature describing only occasional CK expression in haematological neoplasms. CONCLUSIONS: Our data indicate CK expression in a substantial number (15%) of PBLs. In view of the particular morphological features of PBL and its frequent negativity for the common leukocyte antigen and B-cell markers, this feature represents a pitfall in the routine diagnostic work-up of PBL, and requires more extensive immunohistochemical and molecular characterisation of cases entering the differential diagnosis.

Plasmablastic Lymphomas: Characterization of Tumor Microenvironment Using CD163 and PD-1 Immunohistochemistry.

This study aims to characterize the tumor microenvironment of plasmablastic lymphoma (PBL) in regard to the quantities of CD163(+) tumor associated macrophages (TAM) and PD1(+) tumor infiltrating lymphocytes (TIL). This article also reviews the existing knowledge of the role of PD-1/PD-L1 pathway in the tumor microenvironment of hematopoietic neoplasms, discusses potential mechanisms to explain our findings, and outlines areas for future studies. We performed CD163 and PD1 immunohistochemical studies in 11 cases classified as plasmablastic lymphoma, and recorded the percentages of positive TAMs and TILs. Based on previous studies, cut off values of ≥30% and >5% were used to classify the cases into high TAMs and TILs, respectively. We determined that the majority of cases (8 of 11, or 73%) had high percentage of TAMs, while only a minority had high percentage of TILs (3 of 11, or 27%). Our data shows a trend towards a negative correlation between TAMs and TILs (p=0.08), and a predominance of the pattern TAMhigh/TILlow (7 of 11, or 63%) compared to other patterns. The microenvironment of plasma-blastic lymphoma tends to show high percentage of TAMs (≥30%) combined with low percentage of TILs (≤5%). Additional studies are needed to determine the clinical significance of TILs and the influence of EBV and HIV infections on numbers of TILs in PBL. As high microenvironment TAMs have been associated with high microenvironment PD-L1 in other hematopoietic malignancies, our data supports the need for future studies on the expression of PD-L1 in PBL.

Primary central nervous system plasmablastic lymphoma in an HIV-positive patient.

Plasmablastic lymphoma (PBL) is a rare subtype of diffuse large B-cell lymphoma, highly associated with HIV and Epstein-Barr virus (EBV) infections. It commonly presents in extranodal sites, often an oral mass, but reports of primary central nervous system PBL (PCNSPBL) are exceedingly rare. Here, we report on a 33-year-old man with newly diagnosed HIV infection who presented with acute-onset unilateral visual disturbance and was found to have biopsy-proven PCNSPBL. The neoplastic cells displayed a plasmacytoid appearance, with the expression of CD38 and CD138, and were positive for EBV by in situ hybridisation for EBV-encoded RNA. Systemic workup revealed the presence of Kaposi sarcoma, but no evidence of lymphoma. He is currently being treated with high-dose methotrexate, as well as antiretroviral therapy for his HIV infection, and has achieved a complete response.

Transformation of double-hit follicular lymphoma to plasmablastic lymphoma: a partial role of MYC gene rearrangement.

Follicular lymphoma (FL) is genetically characterized by BCL2/IGH translocation. Some FL cases histologically transform to high-grade lymphoma, and the majority of cases transform to diffuse large B-cell lymphoma. We report herein an unusual FL case that transformed to plasmablastic lymphoma (PBL) with MYC gene rearrangement as early as 12 months after FL diagnosis. IGH/MYC translocation, the most common cytogenetic abnormality seen in de novo PBL, was also detected in the transformed tumor (double-hit lymphoma). The patient became resistant to chemotherapy and died 4 months after transformation. We speculate that the "second hit" of MYC rearrangement played a crucial role in PBL transformation (PBL-T) in this case. Highly specific three-color FISH analysis demonstrated the presence of BCL2/IGH/MYC triple fusion signals on a single chromosome as we expected, but BCL2/IGH and IGH/MYC fusion signals also coexisted in a single nucleus. The PBL-T tumor was genetically heterogeneous, despite being histologically quite homogeneous PBL. Surprisingly, three-color FISH analysis revealed that the preceding FL tumor was also genetically heterogeneous, simultaneously harboring BCL2/IGH, IGH/MYC and BCL2/IGH/MYC fusion signals (i.e. double-hit lymphoma), despite being histologically quite homogeneous FL. This suggests that MYC rearrangement played a partial role in PBL-T. Genetic instability including MYC rearrangement in the preceding FL tumor would contribute to PBL-T and poor outcome in this case. This study will broaden our understanding of the pathogenesis of high-grade transformation of FL and help improve patient outcome.

Vitamin D Receptor Expression in Plasmablastic Lymphoma and Myeloma Cells Confers Susceptibility to Vitamin D.

Plasmablastic B-cell malignancies include plasmablastic lymphoma and subsets of multiple myeloma and diffuse large B-cell lymphomaDLBCL. These diseases can be difficult to diagnose and treat, and they lack well-characterized cell line models. Here, immunophenotyping and FOXP1 expression profiling identified plasmablastic characteristics in DLBCL cell lines HLY-1 and SU-DHL-9, associated with CTNNAL1, HPGD, RORA, IGF1, and/or vitamin D receptor (VDR) transcription. We demonstrated VDR protein expression in primary plasmablastic tumor cells and confirmed in cell lines expression of both VDR and the metabolic enzyme CYP27B1, which catalyzes active vitamin D3 production. Although Vdr and Cyp27b1 transcription in normal B cells were activated by interleukin 4 (IL-4) and CD40 signaling, respectively, unstimulated malignant plasmablastic cells lacking IL-4 expressed both VDR and CYP27B1. Positive autoregulation evidenced intact VDR function in all plasmablastic lines, and inhibition of growth by active vitamin D3 was both dependent on MYC protein inhibition and could be enhanced by cotreatment with a synthetic ROR ligand SR-1078. Furthermore, a VDR polymorphism, FOK1, was associated with greater vitamin D3-dependent growth inhibition. In summary, HLY-1 provides an important model of strongly plasmablastic lymphoma, and disruption of VDR pathway activity may be of therapeutic benefit in both plasmablastic lymphoma and myeloma.

Plasmablastic Lymphoma: A Review of Clinicopathologic Features and Differential Diagnosis.

Plasmablastic lymphoma (PBL) is a challenging diagnosis given its rarity and lack of expression of markers that are usually used by pathologists in establishing hematopoietic lineage. However, knowledge of the characteristic clinical setting, sites of involvement, and morphologic features of plasmablastic lymphoma can aid in the correct diagnosis of a suspected large cell lymphoma that is negative for B-cell- and T-cell-specific antigens. Herein, we review the clinical and pathologic features of plasmablastic lymphoma with an emphasis on the differential diagnosis of hematolymphoid neoplasms with immunoblastic morphology and/or evidence of plasmacytic differentiation by immunophenotype.