Therapy of non-Hodgkin's lymphoma

Nomograms for predicting overall survival and cancer-specific survival in patients with head and neck non-Hodgkin lymphoma: A population-based study

This study aimed to develop comprehensive nomograms for patients with head and neck non-Hodgkin lymphoma (H&NNHL) to determine their overall survival (OS) and cancer-specific survival (CSS). In this study, 602 H&NNHL patients were analyzed from the Surveillance, Epidemiology, and End Results database. The R software was used to randomly divide the patients into the training cohort (n = 421) and the validation cohort (n = 181) in a 7-to-3 ratio. To develop nomograms for projecting OS and CSS, multivariable Cox regression was used to acquire independent predictive factors. We have constructed nomograms to predict the 3-, 5-, and 8-year OS and CSS probabilities of H&NNHL patients. The consistency index of the nomograms for OS (CSS) was 0.74 (0.778) and 0.734 (0.775), in the training and validation cohort respectively, and was higher than that of the Ann Arbor staging system. Calibration plotting showed that our models have good calibration ability. Moreover, assessments of the area under the time-dependent receiver operating characteristics curve, net reclassification improvement, integrated discrimination improvement and decision curve analysis demonstrated that our nomograms performed better and were more clinically useful than the Ann Arbor staging system. This is the first research to establish comprehensive nomograms for predicting OS and CSS in patients with H&NNHL at 3-, 5-, and 8-year. The validation of the models demonstrated good performance. It can provide clinicians with reference information for determining customized clinical treatment options and providing personalized prognoses. Indexes such as the concordance index, the area under the time-dependent receiver operating characteristics curve, calibration curves, the net reclassification improvement, the integrated discrimination improvement, and decision-curve analysis were used to compare new survival models to the classical Ann Arbor staging system.

Development and External Validation of a Nomogram to Predict Cancer-Specific Survival in Patients with Primary Intestinal Non-Hodgkin Lymphomas

Purpose

Primary intestinal non-Hodgkin lymphoma (PINHL) is a biologically and clinically heterogeneous disease. Few individual prediction models are available to establish prognoses for PINHL patients. Herein, a novel nomogram was developed and verified to predict long-term cancer-specific survival (CSS) rates in PINHL patients, and a convenient online risk calculator was created using the nomogram.

Materials and Methods

Data on PINHL patients from January 1, 2004, to December 31, 2015, obtained from the Surveillance, Epidemiology, and End Results (SEER) database (n = 2372; training cohort), were analyzed by Cox regression to identify independent prognostic parameters for CSS. The nomogram was internally and externally validated in a SEER cohort (n = 1014) and a First Affiliated Hospital of Guangzhou University of Chinese Medicine (FAHGUCM) cohort (n = 37), respectively. Area under the receiver operating characteristic curve (AUC), calibration curves, and decision curve analysis (DCA) were used to evaluate nomogram performance.

Results

Five independent predictors were identified, namely, age, marital status, Ann Arbor Stage, B symptoms, and histologic type. The nomogram showed good performance in discrimination and calibration, with C-indices of 0.772 (95% CI: 0.754–0.790), 0.763 (95% CI: 0.734–0.792), and 0.851 (95% CI: 0.755–0.947) in the training, internal validation, and external validation cohorts, respectively. The calibration curve indicated that the nomogram was accurate, and DCA showed that the nomogram had a high clinical application value. AUC values indicated that the prediction accuracy of the nomogram was higher than that of Ann Arbor Stage (training cohort: 0.804 vs 0.630; internal validation cohort: 0.800 vs 0.637; external validation cohort: 0.811 vs 0.598), and Kaplan–Meier curves indicated the same.

Conclusion

A nomogram was developed to assist clinicians in predicting the survival of PINHL patients and in making optimal treatment decisions. An online calculator based on the nomogram was made available at https://cuifenzhang.shinyapps.io/DynNomapp/.

CUDC-101 enhances the chemosensitivity of gemcitabine-treated lymphoma cells

BACKGROUND

The metastasis and recurrence of Non-Hodgkin's lymphoma (NHL) is a major cause of morbidity and mortality. Recent work suggests that drugs capable of targeting epigenetic regulatory mechanisms may be well suited to the treatment of such disease progression.

METHODS

This study was thus designed to evaluate the ability of the novel histone deacetylase (HDAC) inhibitor CUDC-101 to synergize with gemcitabine in order to kill human HUT78 and Pfeiffer NHL cells. To that end, we analyzed the viability of these NHL cells via CCK-8 assay, while the incidence of apoptosis among treated cells was evaluated via Annexin V-FITC/PI staining and by the Western blotting-mediated evaluation of proteins associate with apoptosis and related signaling pathways.

RESULTS

We found that CUDC-101 and gemcitabine interacted synergistically to reduce NHL cell viability and to induce the apoptotic death of these cells via the EGFR/ PI3K/Akt and Erk pathways, which were regulated by HDAC signaling pathways.

CONCLUSION

Together, our results highlight the anti-cancer properties of CUDC-101 alone or in combination with gemcitabine as an approach to inducing the apoptotic death of lymphoma cells in vitro, while also offering insight into the underlying molecular mechanisms governing this activity.

Large B cell lymphoma presenting as an adnexal mass in an HIV positive patient: a case report

We present a 34-year-old HIV positive woman who presented with a 2-month history of abdominal pain, abdominal distension, night sweats and fever. She had a firm, immobile and irregular abdominopelvic mass of about 30 weeks uterine size. Investigations showed a haemoglobin of 6.5g/dl, (NR 12-14) cancer antigen 125 of 44U/ml (NR 0-35), serum beta human chorionic gonadotropin (HCG) of 0.258mIU/ml (NR 0-5) and alpha fetoprotein of 7ng/ml (NR <10). Her CD4 count was 63cells/mm³. At laparotomy there was a left ovarian mass and the rest of the abdomen and omentum looked grossly normal, leading to the conclusion that the primary was in the ovaries. A total abdominal hysterectomy, bilateral adnexectomy and infracolic omentectomy were done. Sigmoidectomy and Hartmann's procedure were also performed. Histology of the specimens showed a large B cell lymphoma. She has since been commenced on chemotherapy and antiretroviral therapy and has been doing well.

Primary breast diffuse large B-cell lymphoma: a population-based study from 1975 to 2014

Primary breast diffuse large B-cell lymphoma (DLBCL) is a rare non-Hodgkin's lymphoma with limited data. In this study, a population-based study of primary breast DLBCL in the United States was performed to determine its incidence trends, prognostic factors, survival, the role of surgery as well as the comparison with nodal DLBCL. 1021 patients diagnosed with breast DLBCL were identified in the Surveillance, Epidemiology, and End Results (SEER) cancer registries from 1973-2014. The incidence of both breast and nodal DLBCL increased over time. Patients with breast DLBCL were older, mainly women, diagnosed at earlier stages and had lower prevalence in white and black races compared with nodal DLBCL. Multivariate analysis revealed older age (≥ 70 years old) and advanced stage as independent predictors of worse OS. Independent predictor of better DSS were younger age (< 70 years old), early stage and diagnosis after 2000. When analyzed according to age, stage, race, tumor laterality and year of diagnosis, the overall survival did not benefit from surgery except in patients diagnosed between 2001-2010 and the surgery rate decreased overtime. Compared with nodal DLBCL, breast DLBCL patients exhibited a better outcome. In conclusion, breast DLBCL is a rare tumor with increasing incidence and improved survival over the last four decades. The introduction of rituximab seems to improve the outcome of breast DLBCL. Further studies are needed to advance our understanding of breast DLBCL and optimize the treatment strategy.

Non-Hodgkin's B-cell lymphoma: advances in molecular strategies targeting drug resistance

Non-Hodgkin's lymphoma (NHL) is a heterogeneous class of cancers displaying a diverse range of biological phenotypes, clinical behaviours and prognoses. Standard treatments for B-cell NHL are anthracycline-based combinatorial chemotherapy regimens composed of cyclophosphamide, doxorubicin, vincristine and prednisolone. Even though complete response rates of 40-50% with chemotherapy can be attained, a substantial proportion of patients relapse, resulting in 3-year overall survival rates of about 30%. Relapsed lymphomas are refractory to subsequent treatments with the initial chemotherapy regimen and can exhibit cross-resistance to a wide variety of anticancer drugs. The emergence of acquired chemoresistance thus poses a challenge in the clinic preventing the successful treatment and cure of disseminated B-cell lymphomas. Gene-expression analyses have increased our understanding of the molecular basis of chemotherapy resistance and identified rational targets for drug interventions to prevent and treat relapsed/refractory diffuse large B-cell lymphoma. Acquisition of drug resistance in lymphoma is in part driven by the inherent genetic heterogeneity and instability of the tumour cells. Due to the genetic heterogeneity of B-cell NHL, many different pathways leading to drug resistance have been identified. Successful treatment of chemoresistant NHL will thus require the rational design of combinatorial drugs targeting multiple pathways specific to different subtypes of B-cell NHL as well as the development of personalized approaches to address patient-to-patient genetic heterogeneity. This review highlights the new insights into the molecular basis of chemorefractory B-cell NHL that are facilitating the rational design of novel strategies to overcome drug resistance.

Developing curcumin into a viable therapeutic for lymphoma

BACKGROUND

Emerging evidence suggests that natural plant ingredients have played an important role in the healthcare of many countries. Several of these natural plant products possess therapeutic potential for various diseases including cancer. Curcumin is the pigment of turmeric, a well-known chemopreventive agent that has been shown to suppress the proliferation of a wide variety of tumor cells, including lymphoma. Curcumin has been shown to have cancer chemopreventive potential against a variety of tumors via targeting key survival pathways that are aberrantly activated in cancer cells.

METHODS

This review discusses therapeutic potential of curcumin in malignancies of lymphoma as well as therapeutic implications of the recent advances in the field.

RESULTS/CONCLUSION

Dietary-compound curcumin hardwires to multiple cellular processes. Suppression of cell proliferation, induction of apoptosis, and inhibition of metastasis are considered to be the major mechanisms underlying its anticancer properties.

An unusual cause of postmenopausal bleeding

BACKGROUND

Non-Hodgkin lymphoma usually presents with lymphadenopathy, fever, night sweats, and weight loss. Postmenopausal vaginal bleeding is a cardinal symptom of carcinoma of the endometrium or cervix but not one of non-Hodgkin lymphoma. Clinical awareness of this unusual mode of presentation is important.

CASE

We report a case of non-Hodgkin lymphoma in a 60-year-old woman, who presented primarily with postmenopausal bleeding. Clinical examination revealed a "thickened" area on the posterior vaginal wall. Repeated vaginal biopsies showed fibrosis and inflammatory tissue only. Immunohistochemistry revealed non-Hodgkin lymphoma. This case highlights the diagnostic challenges such a complex case presents.

CONCLUSION

This case not only represents a case of non-Hodgkin lymphoma with genital involvement but also highlights the importance of diagnosis and management of such complex cases.

Two-stage tracheal reconstruction of primary tracheal non-Hodgkin lymphoma with nitinol mesh stent and cervical myocutaneous flap

Primary tracheal non-Hodgkin lymphoma is an extremely rare entity without consensus management strategy. We present a case of primary tracheal lymphoplasmacytoid lymphoma masquerading as asthma with wheezing and progressive dyspnea. A patented nitinol mesh stent was implanted in the right lateral cervical region 3 weeks before tumor resection. After 5.5-cm-long segmental tracheal resection, a neotracheal tube was constructed with cervical myocutaneous flap sandwiched around the implanted mesh stent, which was then anastomosed with the residual of the patient's trachea. The patient has been well for 30 months.

Primary breast lymphoma in the right breast during treatment for left breast cancer

Background

Primary breast lymphoma is a rare condition, and distinguishing it from breast cancer is important because their treatments differ radically. Moreover, a recent report showed that mastectomy offered no benefit in the treatment of primary breast lymphoma.

Case presentation

A 59-year-old woman was treated with adjuvant chemotherapy and local radiation after surgery for left breast cancer. She presented with a rapidly growing mass in the right breast at 20 months after surgery. Mammography and computed tomography revealed a massive tumour. She was diagnosed with primary breast lymphoma by aspiration cytology, and surgery was performed. Histopathological and immunohistochemical findings confirmed a diffuse large B-cell type primary breast lymphoma.

Conclusion

In this case, the lymphoma exhibited rapid growth despite chemotherapy for a malignancy in the contralateral breast. The patient had developed bronchiolitis obliterans organizing pneumonia due to radiation. Therefore, surgical treatment of the lymphoma was selected.

Preclinical and clinical evaluation of epratuzumab (anti-CD22 IgG) in B-cell malignancies

The vast majority of non-Hodgkin's lymphomas are of B-cell phenotype. Development of unlabeled or radiolabeled therapeutic monoclonal antibodies against the cell surface antigen, CD20, has revolutionized the treatment of these malignancies. It is clear that antibodies targeting other B-cell-specific molecules, such as CD22, also offer potential therapeutic benefit. Epratuzumab is a humanized anti-CD22 monoclonal, which has undergone preclinical and phase I/II clinical evaluation in patients with indolent or aggressive lymphoma. Data suggest that this agent is well tolerated, and can induce tumor regressions. Trials are currently evaluating its safety and activity in combination with rituximab (chimeric anti-CD20) and standard chemotherapy are ongoing. Initial results suggest that these regimens have acceptable toxicity, and that epratuzumab warrants further evaluation as an adjunct to standard lymphoma treatment regimens.

Primary breast lymphoma: the role of mastectomy and the importance of lymph node status

OBJECTIVE

To construct and analyze a database comprised of all reported cases of primary breast lymphoma (PBL) that include treatment and follow-up information published during the last 3 decades.

SUMMARY BACKGROUND DATA

PBL accounts for 0.4% of breast malignancies and 2% of extranodal lymphomas. Surgical therapy has varied from biopsy to radical mastectomy. Chemotherapy and radiation therapy have been used as adjuvant or primary therapy. A standard consensus treatment of PBL is not available.

METHODS

We reviewed all published PBL reports from June 1972 to March 2005. A database was compiled by abstracting individual patient information, limiting our study to those reports that contained specific treatment and outcome data. Patient demographics such as survival, recurrence, and time to follow-up were recorded, in addition to surgical, radiation, and/or chemotherapy treatment(s).

RESULTS

We found 465 acceptable patients reported in 92 publications. Age range was 17 to 95 years (mean, 54 years). Mean tumor size was 3.5 cm. Diffuse large cell (B) lymphoma was the most common histologic diagnosis (53%). Disease-free survival was 44.5% overall. Follow-up ranged from one to 288 months (mean, 48 months). Treatment by mastectomy offered no survival benefit or protection from recurrence. Treatment that included radiation therapy in stage I patients (node negative) showed benefit in both survival and recurrence rates. Treatment that included chemotherapy in stage II patients (node positive) showed benefit in both survival and recurrence rates. Histologic tumor grade predicted survival.

CONCLUSIONS

Mastectomy offers no benefit in the treatment of PBL. Nodal status predicts outcome and guides optimal use of radiation and chemotherapy.

Epratuzumab in the therapy of oncological and immunological diseases

B cells play an important role in the pathogenesis of certain lymphomas and leukemias, as well as many autoimmune diseases. Antagonistic B-cell antibodies are thus gaining an increasing role in the management of these diseases. The first antibody target in this regard was CD20, with the development and introduction of rituximab in the management of B-cell malignancies, as well as rheumatoid arthritis. A second candidate target is CD22. The first antagonistic antibody to this B-cell marker, epratuzumab, appears to function, in contrast to CD20 antibodies, more by modulation of B cells rather than by their high depletion in circulation. Originally developed for the treatment of non-Hodgkin's lymphoma, epratuzumab has now been found to be effective, with a very good safety profile, in two prototype autoimmune diseases: systemic lupus erythematosus and primary Sjögren's syndrome. Recent studies have demonstrated the activity and safety of epratuzumab in non-Hodgkin's lymphoma patients who have relapsed or are refractive to conventional therapy, including rituximab, and has also shown good activity in follicular and diffuse large B-cell lymphoma in combination with rituximab. As such, this new investigative antibody may have a significant market potential owing to the multitude of diseases and patients who may benefit from a CD22, B-cell antibody immunotherapy that is complementary to the known effects and role of CD20 antibodies, but can usually be administered within 1 h and depletes approximately 50% of circulating B cells.

Serum levels of sCD137 (4-1BB) ligand are prognostic factors for progression in acute myeloid leukemia but not in non-Hodgkin's lymphoma

CD178 (Fas/APO-1 ligand) and CD137 ligand (CD137L) have previously been described in sera of patients with various malignancies and play an important role in the pathogenesis of various diseases. Recently, we demonstrated that low levels of soluble (s) CD137L and high levels of sCD178 correlate significantly with a long progression free survival in patients with myelodysplastic syndrome (MDS). In this study, we correlated sCD137L and sCD178 levels in sera of 42 samples of patients with acute myeloid leukemia (AML) and 46 samples of patients with non-Hodgkin's lymphoma (NHL) with stages, subtypes, and the clinical course of the diseases and determined cut-off values with maximum probability for significant differentiation between cases with higher/lower probability for progress free survival. In contrast to patients with MDS, surprisingly no correlation between sCD178 levels and different subtypes and stages or with prognosis in AML or NHL were observed. Regarding sCD137L, NHL-patients displayed lower levels compared with AML. Statistically significant higher median levels of sCD137L are present in patients with undifferentiated AML (M1/M2, 1,470 pg/mL), poor cytogenetic risk (288 pg/mL) and higher levels of BM-blasts (186 pg/mL) compared with patients with monocytoid AML (M4/M5, 89 pg/mL), intermediate cytogenetic risk (59 pg/mL) and lower levels of BM-blasts (14 pg/mL) respectively. Furthermore, in AML patients sCD137L levels correlate significantly with the probabilities to achieve complete remission (CR), stay in CR or with progress of the disease. Taken together, our data demonstrate that sCD137L can be used as a prognostic factor not only in MDS but also in AML.

Patterns of care in a population-based random sample of patients diagnosed with non-Hodgkin's lymphoma

New therapies have enhanced treatment of non-Hodgkin's lymphoma (NHL), but extent of treatment use in community practice is unknown. We conducted a population-based study of NHL patients diagnosed in 1999 with histologically confirmed NHL (n = 947) residing in areas covered by the Surveillance, Epidemiology, and End Results program. We performed analyses to study factors associated with receipt of chemotherapy, radiation, and rituximab, and examine factors associated with mortality. Most patients presented with B-cell lymphoma (n = 828). Approximately 20% of patients received no therapy, over 60% received chemotherapy, and 12% received rituximab, alone or in combination. Patients aged 75 +, and males were less likely to have received chemotherapy (p = 0.01). There were no significant associations between receipt of rituximab and the factors analyzed. Patients who presented with B-symptoms or unknown B-symptom status were less likely to receive radiation (OR = 0.32 and 0.47, respectively, p = 0.0002) than asymptomatic patients. Cause-specific and all-cause mortality were significantly associated with patient age, race/ethnicity, gender, marital status, co-morbid conditions, and histological subgroup. Hispanic and African-Americans, patients age 75 +, males, unmarried patients, or patients with B-symptoms had higher risk of death from NHL and all-cause (p < 0.01). This is the first population-based study examining therapy received for many histological subtypes of NHL.

Multifocal Primary Breast Lymphoma

Primary breast lymphoma (PBL) is a rare condition, accounting for only 0.04 to 0.5% of breast malignancies and less than 2% of extranodal lymphomas. Clinical presentation and imaging may suggest a benign condition. Reports of treatment vary widely. Surgical therapy has been reported to include only biopsy or extend to partial mastectomy, total mastectomy, or even radical mastectomy. Chemotherapy with various agents is often used. Radiotherapy has been used in the adjuvant setting or as primary local therapy. Immunotherapy and radioimmunotherapy have shown some promise in other lymphomas and may be useful here as well. There is no standard or consensus of treatment for PBL. This report describes a case of multifocal PBL in a 45-year-old female and discusses the physical findings, diagnosis, and treatment options for this condition.

99mTc-rituximab radiolabelled by photo-activation: a new non-Hodgkin’s lymphoma imaging agent

PURPOSE

Rituximab was the first chimeric monoclonal antibody to be approved for treatment of indolent B-cell non-Hodgkin's lymphoma (NHL). It is directed against the CD20 antigen, which is expressed by 95% of B-cell NHLs. The aim of this study was to explore the possibility of radiolabelling rituximab with (99m)Tc for use as an imaging agent in NHL for early detection, staging, remission assessment, monitoring for metastatic spread and tumour recurrence, and assessment of CD20 expression prior to (radio)immunotherapy.

METHODS

Rituximab was purified from Mabthera solution (Roche), photo-activated at 302 nm by UV irradiation and radiolabelled with (99m)Tc. The effectiveness of the labelling method was evaluated by determination of the number of free thiol groups per photoreduced antibody, radiochemical purity and in vitro stability of (99m)Tc-rituximab.

RESULTS

On average, 4.4 free thiol groups per photoreduced antibody were determined. Radiolabelling yields greater than 95% were routinely observed after storage of the photo-activated antibody at -80 degrees C for 195 days. The direct binding assay showed preserved ability of (99m)Tc-rituximab to bind to CD20, with an average immunoreactive fraction of 93.3%. The internalisation rate was proven to be low, with only 5.3% of bound (99m)Tc-rituximab being internalised over 4 h at 37 degrees C.

CONCLUSION

Our results demonstrate that (99m)Tc-rituximab of high radiochemical purity and with preserved binding affinity for the antigen can be prepared by photoreduction and that the method shows good reproducibility. (99m)Tc-rituximab will be further explored as an imaging agent applicable in NHL for the purposes mentioned above.

Effect of colony-stimulating factor and conventional- or high-dose chemotherapy on FDG uptake in bone marrow

PURPOSE

Granulocyte or granulocyte-macrophage colony stimulating factor (CSF), usually used in conjunction with chemotherapy, may interfere with the( 18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) reading. The purpose of this study is to evaluate the effects of CSF, conventional-or high-dose chemotherapy on bone marrow FDG uptake.

METHODS

Two hundred and forty-one FDG PET scans obtained in 163 patients with lymphoma and no pathologically and radiologically proven bone marrow involvement were analyzed. The standardized uptake value (SUV) of each patient's spine was measured.

RESULTS

Among patients with no recent history of CSF use, the average SUV in 36 patients with no history of chemotherapy was 1.60+/-0.34, that in 49 patients with a history of conventional-dose chemotherapy was 1.37+/-0.32, and that in 12 patients with a history of high-dose chemotherapy was 1.26+/-0.25 (P=0.008 and 0.002, respectively by Mann-Whitney U test). In 80 patients treated with conventional-dose chemotherapy and CSF, the average SUV after discontinuation of CSF was as follows: 0-7 days, 2.37+/-1.19; 8-14 days: 2.04+/-0.67; 15-21 days: 1.87+/-0.52; 22-30 days: 1.59+/-0.18; 31-90 days: 1.54+/-0.36. In 45 patients treated with high-dose chemotherapy and CSF, no significant increase in bone marrow uptake was seen in most of them.

CONCLUSION

Bone marrow FDG uptake may be increased by CSF treatment and may be decreased by chemotherapy. In patients treated with conventional-dose chemotherapy and CSF, increased marrow uptake will return to the pretreatment value approximately 1 month after discontinuation of CSF.

Cellular and molecular signal transduction pathways modulated by rituximab (rituxan, anti-CD20 mAb) in non-Hodgkin's lymphoma: implications in chemosensitization and therapeutic intervention

The clinical application of rituximab (chimeric mouse anti-human CD20 mAb, Rituxan, IDEC-C2B8), alone and/or combined with chemotherapy, has significantly ameliorated the treatment outcome of patients with relapsed and refractory low-grade or follicular non-Hodgkin's lymphoma (NHL). The exact in vivo mechanisms of action of rituximab are not fully understood, although antibody-dependent cell-mediated cytotoxicity (ADCC), complement-dependent cytotoxicity (CDC), and apoptosis have been suggested. We have proposed that modifications of the cellular signaling pathways by rituximab may be crucial for its clinical response. The B-cell restricted cell surface phosphoprotein CD20 is involved in many cellular signaling events including proliferation, activation, differentiation, and apoptosis upon crosslinking. Monomeric rituximab chemosensitizes drug-resistant NHL cells via selective downregulation of antiapoptotic factors through the type II mitochondrial apoptotic pathway. Several signaling pathways are affected by rituximab which are implicated in the underlying molecular mechanisms of chemosensitization. ARL (acquired immunodeficiency syndrome (AIDS)-related lymphoma) and non-ARL cell lines have been examined as in vitro model systems. In ARL, rituximab diminishes the activity of the p38MAPK signaling pathway resulting in inhibition of the interleukin (IL)-10/IL-10R autocrine/paracrine cytokine autoregulatory loop leading to the inhibition of constitutive STAT-3 activity and subsequent downregulation of Bcl-2 expression leading to chemosensitization. Rituximab upregulates Raf-1 kinase inhibitor protein (RKIP) expression in non-ARL cells. Through physical association with Raf-1 and nuclear factor kappaB (NF-kappa B)-inducing kinase (NIK), RKIP negatively regulates two major survival pathways, namely, the extracellular signal-regulated kinase1/2 (ERK1/2) and the NF-kappa B pathways, respectively. Downmodulation of the ERK1/2 and NF-kappa B pathways inhibits the transcriptional activity of AP-1 and NF-kappa B transcription factors, respectively, both of which lead to the downregulation of Bcl-(xL) (Bcl-2 related gene (long alternatively spliced variant of Bcl-x gene)) transcription and expression and sensitization to drug-induced apoptosis. Bcl-(xL)-overexpressing cells corroborated the pivotal role of Bcl-(xL) in chemosensitization. The specificity of rituximab-mediated signaling and functional effects were corroborated by the use of specific pharmacological inhibitors. Many patients do not respond and/or relapse and the mechanisms of unresponsiveness are unknown. Rituximab-resistant B-NHL clones were generated to investigate the acquired resistance to rituximab-mediated signaling, and chemosensitization. Resistant clones display different phenotypic, genetic and functional properties compared to wild-type cells. This review summarizes the data highlighting a novel role of rituximab as a signal-inducing antibody and as a chemosensitizing agent through negative regulation of major survival pathways. Studies presented herein also reveal several intracellular targets modified by rituximab, which can be exploited for therapeutic and prognostic purposes in the treatment of patients with rituximab- and drug-refractory NHL.

Rituximab (Chimeric Anti-CD20 Monoclonal Antibody) Inhibits the Constitutive Nuclear Factor-κB Signaling Pathway in Non-Hodgkin's Lymphoma B-Cell Lines: Role in Sensitization to Chemotherapeutic Drug-induced Apoptosis

The chimeric anti-CD20 antibody rituximab (Rituxan, IDEC-C2B8) is widely used in the clinical treatment of patients with non-Hodgkin's lymphoma (NHL). Rituximab sensitizes NHL B-cell lines to drug-induced apoptosis via down-regulation of Bcl-xL expression. We hypothesized that the mechanism by which rituximab down-regulates Bcl-xL may be, in part, due to inhibition of constitutive nuclear factor-κB (NF-κB) activity that regulates Bcl-xL expression. This hypothesis was tested in CD20+ drug-resistant Ramos (Bcl-2−/Bcl-xL+) and Daudi (Bcl-2+/Bcl-xL+) cell lines. Rituximab decreased the phosphorylation of NF-κB-inducing kinase, IκB kinase, and IκB-α, diminished IKK kinase activity, and decreased NF-κB DNA binding activity. These events occurred with similar kinetics and were observed 3 to 6 hours post-rituximab treatment. Rituximab significantly up-regulated Raf-1 kinase inhibitor protein expression, thus interrupting the NF-κB signaling pathway concomitant with Bcl-xL and Bfl-1/A1 down-regulation. The role of NF-κB in the regulation of Bcl-xL transcription was shown using promoter reporter assays in which deletion of the two-tandem NF-κB binding sites in the upstream promoter region significantly reduced the luciferase activity. This was further corroborated by using IκB superrepressor cells and by NF-κB–specific inhibitors. The direct role of Bcl-xL in drug resistance was assessed by using Bcl-xL–overexpressing cells, which exhibited higher drug resistance that was partially reversed by rituximab. Rituximab-mediated inhibition of the NF-κB signaling pathway and chemosensitization was corroborated by the use of specific inhibitors. These findings reveal a novel pathway mediated by rituximab through Raf-1 kinase inhibitor protein induction that negatively regulates the constitutive NF-κB pathway and chemosensitization of the NHL B-cells.