Contributions
Abstract: EP608
Type: E-Poster Presentation
Session title: Chronic lymphocytic leukemia and related disorders - Biology & Translational Research
Background
B-cell maturation antigen (BCMA) is highly expressed on normal and malignant cells and is a feasible target for multiple myeloma (MM) immunotherapy, which is currently clinically exploited with Teclistamab (Tec, BCMAxCD3 DuoBody®, JNJ-64007957; NCT03145181). BCMA is expressed on late stage B-cells, and whether BCMA can serve as immunotherapeutic target for earlier stage B-cell malignancies is currently unknown. Data regarding BCMA expression on B-cell malignancies are limited. Increased serum levels of soluble BCMA in chronic lymphocytic leukemia (CLL) and Waldenström macroglobulinemia (WM) have been observed, indicating that these B-cell malignancies do express BCMA which is subsequently cleaved off the membrane by γ-secretase (γ-sec).
Aims
We assessed BCMA expression on B-cell lymphoma cell lines and primary malignant cells and explored effects of T-cell activation and killing of B-NHL mediated by Tec in vitro.
Methods
B-NHL cell lines or CLL cells were cultured in presence or absence of γ-sec inhibitor. BCMA expression was assessed by flow cytometry or immunohistochemistry (IHC). To assess Tec function, cell lines or primary CLL were co-cultured with healthy donor (HD) T-cells in presence of Tec. Cytotoxicity, T-cell activation and cytokine production were assessed by flow cytometry.
Results
BCMA expression varied among different B-NHL cell lines while Jurkat (T-cell line) did not express BCMA. Highest BCMA expression was observed in MM cell lines (RPMI-8226 and U266), followed by WM (MWCL1 and BWCM.1), Burkitt lymphoma (BL, Daudi and Ramos), CLL (CII, PGA and Mec-1), diffuse large B-cell lymphoma (DLBCL, OCI-Ly3 and OCI-Ly7) and mantle cell lymphoma (MCL, JeKo-1) (Fig 1A). γ-sec inhibition increased BCMA expression, even when basal levels of BCMA were low, indicating active BCMA shedding. These data were corroborated in primary B-cell lymphoma by IHC and showed moderate levels in WM, and weak or undetectable expression in MCL, DLBCL and CLL (Fig 1B). BCMA membrane expression could be detected at low levels on primary CLL cells by flow cytometry and could be marginally increased by γ-sec treatment.
Next, potency of Tec against lymphoma cell lines was studied. Co-culture of HD T-cells with RPMI-8226, CII, BWCM.1 or JeKo-1 in the presence of Tec resulted in T-cell activation, proliferation and cytotoxicity (Fig 1C-D), independent of the level of BCMA expression. Response to Tec therefore seems to be dependent on a threshold BCMA expression level, but is likely also influenced by tumor intrinsic factors, since WM cell lines with high expression are not efficiently killed.
Efficacy of Tec on primary tumor cells was studied using CLL cells. Despite low BCMA levels, HD T-cells lysed CLL cells up to 40% in presence of Tec. Furthermore, Tec induced activation, degranulation and efficient cytotoxicity by CLL-derived T-cells upon coculture with autologous CLL cells (Fig 1E).
Conclusion
In conclusion, BCMA expression is variable on B-cell lines, which can be enhanced by γ-sec inhibition, and Tec induces cytotoxicity independent of BCMA expression levels. Despite low BCMA expression in primary CLL, Tec induced cytotoxicity and autologous T-cell activation. Further studies to understand the determinants of response to Tec will be required to identify which other diseases might be suitable targets for Tec treatment.
Keyword(s): B-cell maturation antigen, Bispecific, Immunotherapy
Abstract: EP608
Type: E-Poster Presentation
Session title: Chronic lymphocytic leukemia and related disorders - Biology & Translational Research
Background
B-cell maturation antigen (BCMA) is highly expressed on normal and malignant cells and is a feasible target for multiple myeloma (MM) immunotherapy, which is currently clinically exploited with Teclistamab (Tec, BCMAxCD3 DuoBody®, JNJ-64007957; NCT03145181). BCMA is expressed on late stage B-cells, and whether BCMA can serve as immunotherapeutic target for earlier stage B-cell malignancies is currently unknown. Data regarding BCMA expression on B-cell malignancies are limited. Increased serum levels of soluble BCMA in chronic lymphocytic leukemia (CLL) and Waldenström macroglobulinemia (WM) have been observed, indicating that these B-cell malignancies do express BCMA which is subsequently cleaved off the membrane by γ-secretase (γ-sec).
Aims
We assessed BCMA expression on B-cell lymphoma cell lines and primary malignant cells and explored effects of T-cell activation and killing of B-NHL mediated by Tec in vitro.
Methods
B-NHL cell lines or CLL cells were cultured in presence or absence of γ-sec inhibitor. BCMA expression was assessed by flow cytometry or immunohistochemistry (IHC). To assess Tec function, cell lines or primary CLL were co-cultured with healthy donor (HD) T-cells in presence of Tec. Cytotoxicity, T-cell activation and cytokine production were assessed by flow cytometry.
Results
BCMA expression varied among different B-NHL cell lines while Jurkat (T-cell line) did not express BCMA. Highest BCMA expression was observed in MM cell lines (RPMI-8226 and U266), followed by WM (MWCL1 and BWCM.1), Burkitt lymphoma (BL, Daudi and Ramos), CLL (CII, PGA and Mec-1), diffuse large B-cell lymphoma (DLBCL, OCI-Ly3 and OCI-Ly7) and mantle cell lymphoma (MCL, JeKo-1) (Fig 1A). γ-sec inhibition increased BCMA expression, even when basal levels of BCMA were low, indicating active BCMA shedding. These data were corroborated in primary B-cell lymphoma by IHC and showed moderate levels in WM, and weak or undetectable expression in MCL, DLBCL and CLL (Fig 1B). BCMA membrane expression could be detected at low levels on primary CLL cells by flow cytometry and could be marginally increased by γ-sec treatment.
Next, potency of Tec against lymphoma cell lines was studied. Co-culture of HD T-cells with RPMI-8226, CII, BWCM.1 or JeKo-1 in the presence of Tec resulted in T-cell activation, proliferation and cytotoxicity (Fig 1C-D), independent of the level of BCMA expression. Response to Tec therefore seems to be dependent on a threshold BCMA expression level, but is likely also influenced by tumor intrinsic factors, since WM cell lines with high expression are not efficiently killed.
Efficacy of Tec on primary tumor cells was studied using CLL cells. Despite low BCMA levels, HD T-cells lysed CLL cells up to 40% in presence of Tec. Furthermore, Tec induced activation, degranulation and efficient cytotoxicity by CLL-derived T-cells upon coculture with autologous CLL cells (Fig 1E).
Conclusion
In conclusion, BCMA expression is variable on B-cell lines, which can be enhanced by γ-sec inhibition, and Tec induces cytotoxicity independent of BCMA expression levels. Despite low BCMA expression in primary CLL, Tec induced cytotoxicity and autologous T-cell activation. Further studies to understand the determinants of response to Tec will be required to identify which other diseases might be suitable targets for Tec treatment.
Keyword(s): B-cell maturation antigen, Bispecific, Immunotherapy