Influence of rimonabant treatment on peripheral blood mononuclear cells; flow cytometry analysis and gene expression profiling

The cannabinoid receptor type 1 (CB1) antagonist rimonabant has been used as treatment for obesity. In addition, anti-proliferative effects on mitogen-activated leukocytes have been demonstrated in vitro. We have previously shown that rimonabant (SR141716A) induces cell death in ex vivo isolated malignant lymphomas with high expression of CB1 receptors. Since CB1 targeting may be part of a future lymphoma therapy, it was of interest to investigate possible effects on peripheral blood mononuclear cells (PBMC) in patients treated with rimonabant. We therefore evaluated leukocyte subsets by 6 color flow cytometry in eight patients before and at treatment with rimonabant for 4 weeks. Whole-transcript gene expression profiling in PBMC before and at 4 weeks of rimonabant treatment was done using Affymetrix Human Gene 1.0 ST Arrays. Our data show no significant changes of monocytes, B cells, total T cells or T cell subsets in PBMC during treatment with rimonabant. There was a small but significant increase in CD3-, CD16+ and/or CD56+ cells after rimonabant therapy. Gene expression analysis detected significant changes in expression of genes associated with innate immunity, cell death and metabolism. The present study shows that normal monocytes and leukocyte subsets in blood remain rather constant during rimonabant treatment. This is in contrast to the induction of cell death previously observed in CB1 expressing lymphoma cells in response to treatment with rimonabant in vitro. These differential effects observed on normal and malignant lymphoid cells warrant investigation of CB1 targeting as a potential lymphoma treatment.

Flow cytometric analysis of SOX11: a new diagnostic method for distinguishing B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma from mantle cell lymphoma

The differential diagnosis between mantle cell lymphoma (MCL) and B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma (B-CLL/SLL) is essential, since MCL usually has a more aggressive clinical course. By flow cytometry both MCL and B-CLL are CD19, CD20 and usually CD5 positive. However, ambiguities in other immune phenotypic markers of these lymphoma entities sometimes complicate the flow cytometric differential diagnosis. We here demonstrate that the transcription factor SOX11, which is highly up-regulated in most MCL, can be analyzed by flow cytometry. SOX11 protein could be consistently detected in ex vivo isolated MCL but not in B-CLL/SLL. Flow cytometry also enabled protein quantification, and SOX11 protein levels correlated with mRNA expression. We suggest that implementing detection of SOX11 in diagnostic flow cytometry would be beneficial for accurate and reliable diagnosis of MCL, especially for distinguishing cases of MCL and B-CLL/SLL with aberrant immune phenotypes, and for cases of rare cyclin D1 negative MCL.

Higher World Health Organization grades of follicular lymphoma correlate with better outcome in two Nordic Lymphoma Group trials of rituximab without chemotherapy

Abstract A common treatment for follicular lymphoma is rituximab monotherapy. To identify patients for whom this regimen is adequate as first-line therapy, we applied the World Health Organization (WHO) classification for grading follicular lymphoma in a prospective central pathology review of the biopsies of previously untreated patients in two randomized trials of rituximab without chemotherapy. In the first trial (n₁ = 53), higher WHO grades correlated with longer time to next treatment, independently of clinical prognostic factors (p = 0.030); the finding was replicated in the second trial (n₂ = 221; p = 0.019). Higher grades were associated with better treatment responses (p = 0.018). Furthermore, also grades externally confirmed by independent local pathologists correlated with time to next treatment (p = 0.048). Flow cytometry in a separate patient series showed that the intensity of CD20 increased with the malignant cell size (p < 0.00005). In conclusion, WHO grade 1 follicular lymphoma correlates with inferior outcome after rituximab monotherapy. WHO grading might provide a clinically useful tool for personalized therapy.