Rozemarijn S. van Rijn

Complement-induced cell death by rituximab depends on CD20 expression level and acts complementary to antibody-dependent cellular cytotoxicity

Purpose: The use of the CD20-specific antibody rituximab has greatly improved the response to treatment of CD20+ follicular lymphoma. Despite the success of rituximab, resistance has been reported and prognostic markers to predict individual response are lacking. The level of CD20 expression on tumors has been related to response, but results of several studies are contradictory and no clear relationship could be established. Complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) are thought to be important effector mechanisms, but the exact mechanism of rituximab-mediated cell kill is still unknown. Importantly, no data have been reported on the combined contribution of CDC and ADCC. Experimental Design: We have developed a system of clonally related CEM-CD20 cells by retroviral transfer of the human CD20 cDNA (n = 90). This set of cells, with the CD20 molecule as the only variable, was used to study the importance of CD20 expression level on rituximab-mediated CDC, ADCC, and the combination. Results: We show a sigmoidal correlation of CD20 expression level and rituximab-mediated killing via CDC but not ADCC. On both high and low CD20-expressing cells, all CD20 molecules were translocated into lipid rafts after rituximab binding. Furthermore, CDC and ADCC act simultaneously and CDC-resistant cells are sensitive to ADCC and vice versa. Conclusions: These findings suggest that CDC depends on CD20 expression level and that both CDC and ADCC act complementary. These data give new insights into novel strategies to improve the efficacy of CD20-specific antibodies for the treatment of CD20+ tumors.

Early amygdala damage in the rat as a model for neurodevelopmental psychopathological disorders.

Neurodevelopmental disorders in medial temporal lobe structures may underlie psychopathological diseases such as schizophrenia and autism. To construct an animal model for these developmental disorders, social and non-social behavioural responses were assessed in rats with ibotenic acid lesions of the (baso-)lateral and central amygdala or ventral hippocampus, induced early in life. Lesioning the amygdala on day 7 after birth resulted in a variety of behavioural disturbances later in life, whereas after similar lesions on day 21 after birth no disturbances developed, except for deficits in social behaviours. Lesioning the hippocampus led to much less disturbances. The results show that amygdala and hippocampus damage at a specific point early in life results in enduring behavioural disturbances that become more manifest after puberty. In particular, lesions of the amygdala on day 7 of life may serve as a rat model with face and construct validity for neurodevelopmental disorders in studying psychopathology.

Identification of relevant drugable targets in diffuse large B-cell lymphoma using a genome-wide unbiased CD20 guilt-by association approach

Forty percent of patients with diffuse large B-cell lymphoma (DLBCL) show resistant disease to standard chemotherapy (CHOP) in combination with the anti-CD20 monoclonal antibody rituximab (R). Although many new anti-cancer drugs were developed in the last years, it is unclear which of these drugs can be safely combined to improve standard therapy without antagonizing anti-CD20 efficacy. In this study, we aimed to identify rituximab compatible drug-target combinations for DLBCL. For this, we collected gene expression profiles of 1,804 DLBCL patient samples. Subsequently, we performed a guilt-by-association analysis with MS4A1 (CD20) and prioritized the 500 top-ranked CD20-associated gene probes for drug-target interactions. This analysis showed the well-known genes involved in DLBCL pathobiology, but also revealed several genes that are relatively unknown in DLBCL, such as WEE1 and PARP1. To demonstrate potential clinical relevance of these targets, we confirmed high protein expression of WEE1 and PARP1 in patient samples. Using clinically approved WEE1 and PARP1 inhibiting drugs in combination with rituximab, we demonstrated significantly improved DLBCL cell killing, also in rituximab-insensitive cell lines. In conclusion, as exemplified by WEE1 and PARP1, our CD20-based genome-wide analysis can be used as an approach to identify biological relevant drug-targets that are rituximab compatible and may be implemented in phase 1/2 clinical trials to improve DLBCL treatment.

Lactate dehydrogenase levels and F-18-FDG PET/CT metrics differentiate between mediastinal Hodgkin's lymphoma and primary mediastinal B-cell lymphoma

Purpose This study aims to investigate whether clinical, laboratory, and fluorine-18-fluorodeoxyglucose (18F-FDG) PET/CT findings can discriminate between mediastinal Hodgkin’s lymphoma and primary mediastinal B-cell lymphoma (PMBCL). Patients and methods This retrospective study included 56 patients (42 with mediastinal Hodgkin’s lymphoma and 14 with PBMCL). Differences in clinical, laboratory, and 18F-FDG PET/CT metrics were assessed between Hodgkin’s lymphoma and PMBCL. Results Lactate dehydrogenase (LDH) and 18F-FDG PET/CT-based maximum tumor diameter, lesion-to-liver ratio maximum standardized uptake value (SUVmax), and lesion-to-liver ratio peak standardized uptake value (SUVpeak) were all significantly higher (P<0.001) in PMBCL than in Hodgkin’s lymphoma, and PMBCL also significantly more frequently (P=0.001) exhibited necrosis on 18F-FDG PET/CT than Hodgkin’s lymphoma. LDH, maximum tumor diameter, lesion-to-liver ratio SUVmax, and lesion-to-liver ratio SUVpeak yielded areas under the receiver operating characteristic curve of 0.968 [95% confidence interval (CI): 0.923–1.000], 0.866 (95% CI: 0.765–0.968), 0.875 (95% CI: 0.776–0.975), and 0.874 (95% CI: 0.771–0.976), respectively. LDH (with cutoff of 236 U/l) achieved sensitivity and specificity of 81.6 and 100%, respectively; maximum tumor diameter (with cutoff of 9.98 cm) achieved sensitivity and specificity of 87.2 and 78.3%, respectively; lesion-to-liver ratio SUVmax (with cutoff of 7.12) achieved sensitivity and specificity of 94.9 and 64.3%, respectively; lesion-to-liver ratio SUVpeak (with cutoff of 11.45) achieved sensitivity and specificity of 97.4 and 64.3%, respectively; and the presence of necrosis achieved sensitivity and specificity of 78.6 and 74.4%, respectively, in discriminating PMBCL from Hodgkin’s lymphoma. Conclusion LDH levels and several 18F-FDG PET/CT findings (tumor size, presence of necrosis, and degree of 18F-FDG uptake) are helpful in discriminating mediastinal Hodgkin’s lymphoma from PMBCL.