Inhibition of glutaminase-1 in DLBCL potentiates venetoclax-induced antitumor activity by promoting oxidative stress.

Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma in adults, but first-line immunochemotherapy fails to produce a durable response in about one-third of the patients. Because tumor cells often reprogram their metabolism, we investigated the importance of glutaminolysis, a pathway converting glutamine to generate energy and various metabolites, for the growth of DLBCL cells. Glutaminase-1 (GLS1) expression was robustly detected in DLBCL biopsy samples and cell lines. Both pharmacological inhibition and genetic knockdown of GLS1 induced cell death in DLBCL cells regardless of their subtype classification, whereas primary B cells remained unaffected. Interestingly, GLS1 inhibition resulted not only in reduced levels of intermediates of the tricarboxylic acid cycle but also in a strong mitochondrial accumulation of reactive oxygen species. Supplementation of DLBCL cells with α-ketoglutarate or with the antioxidant α-tocopherol mitigated oxidative stress and abrogated cell death upon GLS1 inhibition, indicating an essential role of glutaminolysis in the protection from oxidative stress. Furthermore, the combination of the GLS1 inhibitor CB-839 with the therapeutic BCL2 inhibitor ABT-199 not only induced massive reactive oxygen species (ROS) production but also exhibited highly synergistic cytotoxicity, suggesting that simultaneous targeting of GLS1 and BCL2 could represent a novel therapeutic strategy for patients with DLBCL.

Complete Remission and Long-term Survival of a Patient with a Diffuse Large B-cell Lymphoma Under Viscum album Extracts After Resistance to R-CHOP: A Case Report.

BACKGROUND: A nodular lymphocyte predominant Hodgkin's lymphoma (NLPHL) is a lymphoproliferative neoplasm with a fair prognosis, but the possibility of a malignant transformation into a diffuse large B-cell lymphoma (DLBCL) is high. DLBCL progresses aggressively. Introduction of rituximab into therapy had led to improved outcomes. The use of Viscum album extracts (VAE) in cancer is established, but their application in lymphoma are rare. CASE PRESENTATION: A 65-year-old patient was diagnosed with DLBCL stage IIa with splenomegaly, transformed from a NLPHL, after a 30-year history of repeatedly enlarged inguinal lymph nodes. The patient initially rejected chemotherapy. After his tumor pain increased, he accepted the consecutive therapies bendamustine plus vincristine plus prednisolone, trofosfamide, and rituximab plus cyclophosphamide plus hydroxydaunorubicin plus vincristine plus prednisone (R-CHOP), inducing only a slight regression of the splenic lesions. VAE was additionally applied to R-CHOP. Five months after termination of chemotherapy - under continued VAE therapy in increasing dosage- regression of paraaortal lesions was found. The patient fully recovered under continuous VAE application and is in ongoing complete remission and in a good state of health 17 years after the initial diagnosis. CONCLUSION: As complete remission of lymphoproliferative disorders after VAE treatment has been previously reported, further investigations of VAE in lymphoma seem highly worthwhile.

Primary cutaneous follicular helper T-cell lymphoma: diagnostic pitfalls of this new lymphoma subtype.

The recently proposed entity of cutaneous follicular helper T (T(FH)) cell lymphoma (CT(FH)CL) harbors distinct clinical and histopathologic features. Here, diagnostic pitfalls are exemplified in a case report and by review of the literature. A 45-year-old patient developed rapidly growing nodules and plaques on upper arms and buttocks, which were initially misdiagnosed as primary cutaneous follicle center B-cell lymphoma (CFCL). Consequently, systemic therapy with rituximab failed and consecutive skin biopsies revealed CT(FH)CL (CD3+CD4+CD10+PD-1+bcl6+ICOS+CXCL13+). Interestingly, the prima vista PD-1-positive and CD10-positive tumor cells lost PD-1 expression in follow-up biopsies while retaining CD10, ICOS and CXCL13 expression. All biopsy specimens displayed an identical clonal T-cell population. Initially, nodules were controlled by local radiotherapy and oral psoralen combined with ultraviolet A (PUVA) therapy. However, disease recurred and progressed rapidly with disseminated nodules. Treatment with bexarotene, methotrexate and polychemotherapy failed to stop disease progression. Finally, modified total skin electron beam radiation resulted in complete remission. Disease stabilized on maintenance therapy with bexarotene in combination with ultraviolet A (UVA) therapy. The case highlights that because of concomitant B-cell stimulation, CT(FH)CL clinicopathologically is prone to be mistaken for CFCL. Importantly, CT(FH)CL might lose PD-1 while retaining CD10 expression in later stages, which may lead to confusion in distinguishing CT(FH)CL from CFCL.