Remission maintenance treatment options in chronic lymphocytic leukemia

Development of Stable CHO-K1 Cell Lines Overexpressing Full-Length Human CD20 Antigen

Background

CD20 is a differentiation-related antigen exclusively expressed on the membrane of B lymphocytes. CD20 amplification is observed in numerous immune-related disorders, making it an ideal target for immunotherapy of hematological malignancies and autoimmune diseases. MAb-based therapies targeting CD20 have a principal role in the treatment of several immune-related disordes and cancers, including CLL. Fc gamma receptors mediate CD20 internalization in hematopoietic cells; therefore, this study aimed to establish non-hematopoietic stable cell lines overexpressing full-length human CD20 antigen as an in vitro model for CD20-related studies.

Methods

CD20 gene was cloned into the transfer vector. The lentivirus system was transfected to packaging HEK 293T cells, and the supernatants were harvested. CHO-K1 cells were transduced using recombinant viruses, and a stable cell pool was developed by the antibiotic selection. CD20 expression was confirmed at the mRNA and protein levels.

Results

Simultaneous expression of GFP protein facilitated the detection of CD20-expressing cells. Immunophenotyping analysis of stable clones demonstrated expression of CD20 antigen. In addition, the mean fluorescence intensity was significantly higher in the CD20-CHO-K1 clones than the wild-type CHO-K1 cells.

Conclusion

This study is the first report on using second-generation lentiviral vectors for the establishment of a non-hematopoietic cell-based system, which stably expresses full-length human CD20 antigen. Results of stable CHO cell lines with different levels of CD20 antigen are well suited to be used for CD20-based investigations, including binding and functional assays.

Randomized controlled trial of individualized, low dose, fixed duration lenalidomide maintenance versus observation after frontline chemo-immunotherapy in CLL

Lenalidomide maintenance after frontline chemo-immunotherapy (CIT) in chronic lymphocytic leukemia (CLL) has not been standard due to the availability of novel therapies, though these remain out of reach for most in low-middle income countries. This single-center, open-label study randomized CLL patients (non-deletion 17p) after frontline therapy to lenalidomide maintenance (dose-escalated 2.5-10mg, 20/28 days per cycle for six months) or observation (2:1 allocation). Forty patients were included over 2018-2020. At a median follow-up of 22 months, median progression-free survival (PFS) with lenalidomide was not significantly different than observation (26 vs. 18 months, p = 0.4). Patients with minimal residual disease >10^-2 had a trend toward better PFS with lenalidomide (19 vs. 7 months, p = 0.07). Grade 3 neutropenia was seen in 16.7% of patients on lenalidomide. Quality of life was comparable between the two arms. Low dose, fixed duration lenalidomide maintenance is not an effective strategy after frontline CIT in CLL.