Alja J. Stel

Fas receptor clustering and involvement of the death receptor pathway in rituximab-mediated apoptosis with concomitant sensitization of lymphoma B cells to Fas-induced apoptosis

Ab binding to CD20 has been shown to induce apoptosis in B cells. In this study, we demonstrate that rituximab sensitizes lymphoma B cells to Fas-induced apoptosis in a caspase-8-dependent manner. To elucidate the mechanism by which Rituximab affects Fas-mediated cell death, we investigated rituximab-induced signaling and apoptosis pathways. Rituximab-induced apoptosis involved the death receptor pathway and proceeded in a caspase-8-dependent manner. Ectopic overexpression of FLIP (the physiological inhibitor of the death receptor pathway) or application of zIETD-fmk (specific inhibitor of caspase-8, the initiator-caspase of the death receptor pathway) both specifically reduced rituximab-induced apoptosis in Ramos B cells. Blocking the death receptor ligands Fas ligand or TRAIL, using neutralizing Abs, did not inhibit apoptosis, implying that a direct death receptor/ligand interaction is not involved in CD20-mediated cell death. Instead, we hypothesized that rituximab-induced apoptosis involves membrane clustering of Fas molecules that leads to formation of the death-inducing signaling complex (DISC) and downstream activation of the death receptor pathway. Indeed, Fas coimmune precipitation experiments showed that, upon CD20-cross-linking, Fas-associated death domain protein (FADD) and caspase-8 were recruited into the DISC. Additionally, rituximab induced CD20 and Fas translocation to raft-like domains on the cell surface. Further analysis revealed that, upon stimulation with rituximab, Fas, caspase-8, and FADD were found in sucrose-gradient raft fractions together with CD20. In conclusion, in this study, we present evidence for the involvement of the death receptor pathway in rituximab-induced apoptosis of Ramos B cells with concomitant sensitization of these cells to Fas-mediated apoptosis via Fas multimerization and recruitment of caspase-8 and FADD to the DISC.

Superior Activity of Fusion Protein scFvRit:sFasL over Cotreatment with Rituximab and Fas Agonists

The clinical efficacy of the CD20-specific chimeric monoclonal antibody rituximab is significantly hampered by intrinsic or acquired resistance to therapy. Rituximab activates antibody-dependent cellular cytotoxicity/complement-dependent cytotoxicity-dependent lysis but also induces apoptosis by cross-linking of its target antigen CD20. Recent reports indicate that this apoptotic activity of rituximab can be synergized by cotreatment with Fas agonists. Here, we report on a strategy designed to exploit and optimize the synergy between rituximab and Fas signaling by genetically fusing a rituximab-derived antibody fragment to soluble Fas ligand (sFasL). The resultant fusion protein, designated scFvRit:sFasL, potently induced CD20-restricted apoptosis in a panel of malignant B-cell lines (10 of 11) and primary patient-derived malignant B cells (two of two non-Hodgkin lymphoma and five of six B cell chronic lymphocytic leukemia). ScFvRit:sFasL efficiently activated CD20 and Fas apoptotic signaling, resulting in a far superior proapoptotic activity compared with cotreatment with rituximab and Fas agonists. ScFvRit:sFasL lacked activity toward normal human B cells and also lacked systemic toxicity in nude mice with no elevation of aspartate aminotransferase and alanine aminotransferase levels or liver caspase-3 activity. In conclusion, scFvRit:sFasL efficiently activates CD20 and Fas-apoptotic signaling and may be useful for the elimination of malignant B cells.

Low p21(Waf1/Cip1) protein level sensitizes testicular germ cell tumor cells to Fas-mediated apoptosis

In the present study, we investigated the relation between p21 expression and the sensitivity of testicular germ cell tumor (TGCT) cells to apoptotic stimuli. Despite similar cisplatin-induced wild-type p53 accumulation, the TGCT cell lines Tera and Scha expressed low p21 protein and mRNA levels in comparison to A2780 ovarian cancer cells. Inhibition of the proteasome complex with MG-132 increased p21 protein levels in TGCT cells but much more in A2780 cells, whereas cisplatin had no additional effect on p21 protein levels. Inhibition of caspase-3 activity in TGCT cells with the broad-spectrum caspase inhibitor zVAD-fmk had no effect on p21 levels and also not upon cisplatin treatment. A similar induction of p53 irradiation, in contrast to cisplatin, substantially increased both p21 mRNA and protein expression in Tera cells. Cisplatin-treated Tera cells expressing low p21 protein levels were Fas-sensitive, while irradiation-induced p21, which was mainly localized in the cytosol, rendered irradiated Tera cells resistant to Fas-induced apoptosis. Sensitivity of irradiated Tera cells to Fas-induced apoptosis was restored by short interfering RNA-specific suppression of p21 expression. These results strongly indicate that the low p21 protein levels are caused by reduced p21 gene transcription and sensitize cisplatin-treated TGCT cells to the Fas death pathway.

Ultrasonography of major salivary glands compared with parotid and labial gland biopsy and classification criteria in patients with clinically suspected primary Sjögren’s syndrome

Objective To assess the validity of ultrasound of major salivary glands (sUS) compared with parotid and labial gland biopsies, sialometry, anti-SSA/Ro antibody status and classification criteria in patients clinically suspected with primary Sjögren’s syndrome (pSS). Methods 103 consecutive outpatients with clinically suspected pSS underwent sUS. Parenchymal echogenicity, homogeneity, hypoechogenic areas, hyperechogenic reflections and clearness of salivary gland border were scored according to the Hocevar scoring system. Total ultrasound score was calculated as the sum of these domains (range 0–48). Results Absolute agreement between sUS and parotid (83%) and labial (79%) gland biopsy outcome was good. Negative sUS predicts negative parotid gland biopsy, and positive sUS predicts positive labial gland biopsy. Compared with the American European Consensus Group (AECG) classification, sUS showed an absolute agreement of 82%, sensitivity of 71% and specificity of 92%. Compared with the American College of Rheumatology (ACR) classification, absolute agreement was 86%, sensitivity was 77% and specificity was 92%. Compared with the ACR-European League Against Rheumatism (EULAR) classification, absolute agreement was 80%, sensitivity was 67% and specificity was 94%. Positive sUS predicts classification, but negative sUS does not exclude classification. The combination of positive sUS with presence of anti-SSA/Ro antibodies or negative sUS with absence of anti-SSA/Ro antibodies showed a high predictive value for classification as pSS or non-pSS. Conclusion In our prospective inception cohort study derived from daily clinical practice, absolute agreement between sUS and salivary gland biopsies was slightly higher for parotid compared with labial gland biopsies. The combination of positive sUS and presence of anti-SSA/Ro antibodies highly predicts classification according to the AECG, ACR and ACR-EULAR classification criteria.

Characterization of BIS20x3, a bi-specific antibody activating and retargeting T-cells to CD20-positive B-cells

This paper describes a bi-specific antibody, which was called BIS20x3. It retargets CD3ɛ-positive cells (T-cells) to CD20-positive cells and was obtained by hybrid–hybridoma fusion. BIS20x3 could be isolated readily from quadroma culture supernatant and retained all the signalling characteristics associated with both of its chains. Cross-linking of BIS20x3 on Ramos cells leads to DNA fragmentation percentages similar to those obtained after Rituximab-cross-linking. Cross-linking of BIS20x3 on T-cells using cross-linking F(ab′)2-fragments induced T-cell activation. Indirect cross-linking of T-cell-bound BIS20x3 via Ramos cells hyper-activated the T-cells. Furthermore, it was demonstrated that BIS20x3 effectively re-targets T-cells to B-cells, leading to high B-cell cytotoxicity. The results presented in this paper show that BIS20x3 is fully functional in retargeting T-cells to B-cells and suggest that B-cell lymphomas may represent ideal targets for T-cell retargeting bi-specific antibodies, because the retargeted T-cell is maximally stimulated in the presence of B-cells. Additionally, since B-cells may up-regulate CD95/ Fas expression upon binding of CD20-directed antibodies, B-cells will become even more sensitive for T-cell mediated killing via CD95L/ Fas L, and therefore supports the intention to use T-cell retargeting bi-specific antibodies recognizing CD20 on B-cell malignancies as a treatment modality for these diseases.

The Role of B Cell-Mediated T Cell Costimulation in the Efficacy of the T Cell Retargeting Bispecific Antibody BIS20x3

In this study, we investigated the role of the naturally occurring B cell-mediated T cell costimulation in the antitumor efficacy of the bispecific Ab BIS20x3. BIS20x3 has a dual specificity for both CD20 and CD3 and has previously been shown to effectively direct the lytic potential of cytolytic T cells toward malignant, CD20+ B cells. BIS20x3 instigated T cell-B cell interaction caused a dose-dependent activation of T cells that was 30 times stronger when compared with T cell activation induced by monovalent anti-CD3 Abs. The activation of T cells by BIS20x3 and B cells appeared functional and resulted in the rapid induction of high lytic potential in freshly isolated peripheral T cells. BIS20x3-mediated T cell-B cell interaction resulted in a significant up-regulation of ICAM-1 on B cells and the activation of T cells was found to be dependent on the interaction of ICAM-1 with LFA-1 and trans-activation by the NF-κB pathway. Also, the lytic potential of freshly isolated T cells activated via BIS20x3 appeared to be dependent on NF-κB signaling in the target B cells. Interestingly, the costimulatory signaling effects described in this study appeared specifically related to the targeting against CD20 because targeting against CD19, by a CD3xCD19-directed bispecific Ab, was significantly less effective in inducing T cell activation and T cell-mediated B cell lysis. Together these results demonstrate that the malignant B cells actively contribute to their own demise upon CD20-directed bispecific Ab-mediated T cell targeting.

Scoring hypoechogenic areas in one parotid and one submandibular gland increases feasibility of ultrasound in primary Sjögren’s syndrome

Objective To assess whether ultrasonographic scoring of (i) both parotid and submandibular salivary glands and (ii) all individual components of the Hocevar scoring system, is needed for classifying patients as primary Sjögren’s syndrome (pSS). Methods Ultrasound examination of the major salivary glands (sUS) was performed in 204 consecutive patients clinically suspected (n=171) or diagnosed (n=33) with pSS. Parenchymal echogenicity, homogeneity, hypoechogenic areas, hyperechogenic reflections and salivary gland posterior border were scored in left and right parotid and submandibular glands. Logistic regression analyses were performed to assess which glands and sUS components contributed significantly to classification as pSS or non-pSS according to the 2016 American College of Rheumatology-European League Against Rheumatism (ACR-EULAR) criteria. Results 116 (57%) patients were classified as pSS, the remaining as non-pSS. Instead of scoring both sides (area under the curve; AUC=0.856, Nagelkerke R2=0.526), multivariate analysis showed that sUS scoring of only right (AUC=0.850; R2=0.518) or left (AUC=0.852; R2=0.511) parotid and submandibular glands is sufficient to predict ACR-EULAR classification. Moreover, all individual components of the Hocevar scoring system significantly predicted classification. Multivariate analysis showed that parenchymal echogenicity and hypoechogenic areas contributed independently to ACR-EULAR classification (AUC=0.857; R2=0.539). Scoring these components in one parotid and one submandibular gland highly predicted ACR-EULAR classification (AUC=0.855; R2=0.539). Scoring only hypoechogenic areas on one side showed almost similar results (AUC=0.846; R2=0.498). Conclusion sUS examination of parotid and submandibular glands on one side is sufficient to predict classification of patients according to the ACR-EULAR criteria. To further increase feasibility of sUS in outpatient clinics worldwide, only hypoechogenic areas can be scored.

Validation of the ACR-EULAR criteria for primary Sjogren's syndrome in a Dutch prospective diagnostic cohort

Objectives To validate the ACR-EULAR classification criteria for primary SS (pSS), and compare them to the American-European Consensus Group (AECG) and ACR criteria in a Dutch prospective diagnostic cohort. Methods Consecutive patients (n = 129) referred for suspicion of pSS underwent a multidisciplinary evaluation, including a labial and/or parotid gland biopsy. Patients with an incomplete work-up (n = 8) or associated systemic auto-immune disease (n = 7) were excluded. The ACR-EULAR classification was compared with expert classification, AECG and ACR classification. Additionally, the accuracy of individual ACR-EULAR items in discriminating pSS from non-pSS was evaluated. The validity of criteria sets was described separately using parotid or labial gland biopsy results for classification. Results Of the 114 evaluated patients, the expert panel classified 34 (30%) as pSS and 80 (70%) as non-pSS. Using labial gland biopsy results, ACR-EULAR classification showed 87% absolute agreement (κ = 0.73) with expert classification, with a sensitivity of 97% and specificity of 83%. Using the parotid gland biopsy results, the ACR-EULAR criteria performed excellently as well. Focus score, anti-SSA titre and ocular staining score showed good to excellent accuracy, whereas unstimulated whole saliva and Schirmers test had poor accuracy. The ACR-EULAR and AECG criteria had equal validity. Compared with ACR classification, ACR-EULAR classification showed higher sensitivity but lower specificity. Conclusion The ACR-EULAR criteria showed good agreement with expert classification, but some patients may be misclassified as pSS. Unstimulated whole saliva and Schirmers test showed poor discriminative value. The ACR-EULAR criteria performed equally to the AECG criteria, and had higher sensitivity but lower specificity than the ACR criteria.

Can ultrasound of the major salivary glands assess histopathological changes induced by treatment with rituximab in primary Sjögren’s syndrome?

With great interest we have read the recent publication by Fisher et al ,1 entitled ‘Effect of rituximab on a salivary gland ultrasound score in primary Sjogren’s syndrome: results of the TRACTISS randomised double-blind multicenter substudy’ in which the authors demonstrated a significant improvement in total ultrasound score (TUS) after rituximab treatment compared with placebo at weeks 16 and 48 in 52 patients with primary Sjogren’s syndrome (pSS). We and others have shown that treatment with rituximab, a chimeric anti-CD20 monoclonal antibody, affects the histopathology of the salivary glands and results in a decrease in area of lymphocytic infiltrate in the labial and parotid glands.2–5 This reduction in infiltrated area, that is, up to 50%, is mainly caused by B cell depletion.2 Rituximab treatment also causes a significant loss of germinal centres.2 Interestingly, rituximab treatment also leads to a significant restoration of the ductal epithelium glandular tissue itself. This is illustrated by a significant decrease in number and severity of lymphoepithelial lesions (LELs) in parotid gland tissue 12 weeks after rituximab treatment.2 6 The normalisation of the epithelium appears to be a direct consequence of depletion of intraepithelial B cells.7 Significant improvement of the parotid gland ultrasound score of patients with pSS has been observed before in another randomised controlled trial (RCT) with rituximab, the Tolerance and Efficacy of Rituximab in Primary Sjogren’s Syndrome (TEARS) study.8 This is an RCT with rituximab versus placebo, performed by a French group. Together with the improvement of the histopathology of the gland, it might not be a surprise that Fisher et al 1 also observed a significant improvement in TUS. This newly …

Salivary gland ultrasound can differentiate primary sjÖgren's syndrome from systemic diseases with salivary gland involvement

Background Ultrasound of the major salivary glands (SGUS) has shown high diagnostic accuracy for primary Sjögrens syndrome (pSS) [1,2]. None of the existing studies, however, included a control group of patients with sarcoidosis, amyloidosis, human immunodeficiency virus (HIV) or hepatitis C (HCV) infection [2]. These diseases are known to frequently affect the major salivary glands, cause dry mouth or may have histopathology similar to pSS. Objectives To assess the diagnostic accuracy of SGUS to differentiate pSS from systemic diseases with salivary gland involvement. Methods Twenty consecutive patients fulfilling the AECG criteria for pSS and 20 consecutive patients with well-established systemic diseases, i.e., 5 patients with sarcoidosis, 5 patients with amyloidosis, 5 patients with HIV infection and 5 patients with HCV infection, were included. Echogenicity, parenchymal homogeneity, presence of hypoechogenic areas and clearness of posterior glandular border of both parotid and submandibular salivary glands were scored independently by two blinded observers and rated according to the Hocevar et al scoring system (ultrasound total score (UTS), range: 0–48) [3]. The optimal cut-off point was determined by using ROC curve. The agreement between SGUS positivity and classification as pSS was assessed. Results The median age of patients with pSS and systemic diseases was 50 and 53 years, respectively. Daily complaints of dry mouth longer than 3 months, need of liquid to swallow food and recurrent or persistent swelling of the major salivary glands were reported by 95%, 85% and 70% of patients with pSS compared to 45%, 30% and 20% of patients with systemic diseases. The accuracy of SGUS to discriminate pSS was excellent, with an area under ROC of 0.91 and optimal cut off point of 15. The agreement between SGUS and diagnosis for pSS was good (κ=0.75, percentage of absolute agreement 87.5) with a sensitivity of 90%, specificity of 85%, positive predictive value of 86%, negative predictive value of 89% and diagnostic odds ratio of 51. UTS was positive in 2 patients with HIV infection and one patient with sarcoidosis. Patients with pSS had significantly higher UTS than patients with systemic diseases (median UTS 27 vs. 10, p<0.001) and patients of the various subgroups (p<0.05; Fig). Conclusions This pilot study indicates that SGUS has a high diagnostic accuracy to discriminate pSS from associated systemic diseases with salivary gland involvement. A minority of HIV and sarcoidosis patients, however, may show SGUS findings mimicking pSS. References Jousse-Joulin et al. Rheumatology (Oxford) 2016;55:789–800. Delli et al. Oral Dis 2015;21:792–800. Hocevar et al. Rheumatology (Oxford) 2005;44:768–72. Disclosure of Interest None declared