Prostate stem cell antigen is overexpressed in prostate cancer metastases

An affinity matured minibody for PET imaging of prostate stem cell antigen (PSCA)-expressing tumors

Purpose

Prostate stem cell antigen (PSCA), a cell surface glycoprotein expressed in normal human prostate and bladder, is over-expressed in the majority of localized prostate cancer and most bone metastases. We have previously shown that the hu1G8 minibody, a humanized anti-PSCA antibody fragment (single-chain Fv-C_H3 dimer, 80 kDa), can localize specifically and image PSCA-expressing xenografts at 21 h post-injection. However, the humanization and antibody fragment reformatting decreased its apparent affinity. Here, we sought to evaluate PET imaging contrast with affinity matured minibodies.

Methods

Yeast scFv display, involving four rounds of selection, was used to generate the three affinity matured antibody fragments (A2, A11, and C5) that were reformatted into minibodies. These three affinity matured anti-PSCA minibodies were characterized in vitro, and following radiolabeling with ¹²⁴I were evaluated in vivo for microPET imaging of PSCA-expressing tumors.

Results

The A2, A11, and C5 minibody variants all demonstrated improved affinity compared to the parental (P) minibody and were ranked as follows: A2 > A11 > C5 > P. The ¹²⁴I-labeled A11 minibody demonstrated higher immunoreactivity than the parental minibody and also achieved the best microPET imaging contrast in two xenograft models, LAPC-9 (prostate cancer) and Capan-1 (pancreatic cancer), when evaluated in vivo.

Conclusion

Of the affinity variant minibodies tested, the A11 minibody that ranked second in affinity was selected as the best immunoPET tracer to image PSCA-expressing xenografts. This candidate is currently under development for evaluation in a pilot clinical imaging study.

Chronic active B-cell-receptor signalling in diffuse large B-cell lymphoma

A role for B-cell-receptor (BCR) signalling in lymphomagenesis has been inferred by studying immunoglobulin genes in human lymphomas and by engineering mouse models, but genetic and functional evidence for its oncogenic role in human lymphomas is needed. Here we describe a form of 'chronic active' BCR signalling that is required for cell survival in the activated B-cell-like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL). The signalling adaptor CARD11 is required for constitutive NF-kappaB pathway activity and survival in ABC DLBCL. Roughly 10% of ABC DLBCLs have mutant CARD11 isoforms that activate NF-kappaB, but the mechanism that engages wild-type CARD11 in other ABC DLBCLs was unknown. An RNA interference genetic screen revealed that a BCR signalling component, Bruton's tyrosine kinase, is essential for the survival of ABC DLBCLs with wild-type CARD11. In addition, knockdown of proximal BCR subunits (IgM, Ig-kappa, CD79A and CD79B) killed ABC DLBCLs with wild-type CARD11 but not other lymphomas. The BCRs in these ABC DLBCLs formed prominent clusters in the plasma membrane with low diffusion, similarly to BCRs in antigen-stimulated normal B cells. Somatic mutations affecting the immunoreceptor tyrosine-based activation motif (ITAM) signalling modules of CD79B and CD79A were detected frequently in ABC DLBCL biopsy samples but rarely in other DLBCLs and never in Burkitt's lymphoma or mucosa-associated lymphoid tissue lymphoma. In 18% of ABC DLBCLs, one functionally critical residue of CD79B, the first ITAM tyrosine, was mutated. These mutations increased surface BCR expression and attenuated Lyn kinase, a feedback inhibitor of BCR signalling. These findings establish chronic active BCR signalling as a new pathogenetic mechanism in ABC DLBCL, suggesting several therapeutic strategies.

Targeting prostate cancer cells in vivo using a rapidly internalizing novel human single-chain antibody fragment

Human antibodies targeting prostate cancer cell surface epitopes may be useful for imaging and therapy. The objective of this study was to evaluate the tumor targeting of an internalizing human antibody fragment, a small-size platform, to provide high contrast in a mouse model of human prostate carcinoma.

METHODS

A prostate tumor-targeting single-chain antibody fragment (scFv), UA20, along with a nonbinding control scFv, N3M2, were labeled with (99m)Tc and evaluated for binding and rapid internalization into human prostate tumor cells in vitro and tumor homing in vivo using xenograft models. For the in vitro studies, the labeled UA20 scFv was incubated at 37 degrees C for 1 h with metastatic prostate cancer cells (DU145) to assess the total cellular uptake versus intracellular uptake. For the animal studies, labeled UA20 and N3M2 scFvs were administered to athymic mice implanted subcutaneously with DU145 cells. Mice were imaged with small-animal SPECT/CT with concomitant biodistribution at 1 and 3 h after injection.

RESULTS

The UA20 scFv was labeled in 55%-65% yield and remained stable in phosphate buffer within 24 h. The labeled UA20 scFv was taken up specifically by prostate tumor cells. Internalization was rapid, because incubation at 37 degrees C for less than 1 h resulted in 93% internalization of total cell-associated scFvs. In animal studies, SPECT/CT showed significant tumor uptake as early as 1 h after injection. At 3 h after injection, tumor uptake was 4.4 percentage injected dose per gram (%ID/g), significantly greater than all organs or tissues studied (liver, 2.7 %ID/g; other organs or tissues, <1 %ID/g), except the kidneys (81.4 %ID/g), giving tumor-to-blood and tumor-to-muscle ratios of 12:1 and 70:1, respectively. In contrast, the control antibody exhibited a tumor uptake of only 0.26 %ID/g, similar to that of muscle and fat. Tumor-specific targeting was evidenced by reduced tumor uptake of nearly 70% on administration of a 10-fold excess of unlabeled UA20 scFv. Kidney uptake was nonspecific, consistent with the route of excretion by scFvs.

CONCLUSION

The UA20 scFv showed rapid and specific internalization in prostate tumor cells in vitro and accumulation in prostate tumor xenografts in vivo, demonstrating the potential for future development for prostate cancer imaging and targeted therapy.

Integrative oncogenomic analysis of microarray data in hematologic malignancies

During the last decade, gene expression microarrays and array-based comparative genomic hybridization (array-CGH) have unraveled the complexity of human tumor genomes more precisely and comprehensively than ever before. More recently, the simultaneous assessment of global changes in messenger RNA (mRNA) expression and in DNA copy number through "integrative oncogenomic" analyses has allowed researchers the access to results uncovered through the analysis of one-dimensional data sets, thus accelerating cancer gene discovery. In this chapter, we discuss the major contributions of DNA microarrays to the study of hematological malignancies, focusing on the integrative oncogenomic approaches that correlate genomic and transcriptomic data. We also present the basic aspects of these methodologies and their present and future application in clinical oncology.

Inhibition of NF-κB signaling as a strategy in disease therapy

As described extensively in this issue, NF-κB transcription factors regulate a number of important physiological processes, including inflammation and immune responses, cell growth and survival, and the expression of certain viral genes. Moreover, NF-κB activity is elevated in and contributes to the pathology of several human diseases, including many cancers and chronic inflammatory diseases. Therefore, there has been great interest in the characterization and development of methods to limit NF-κB signaling for pharmacological intervention. This article describes some of the approaches that have been employed to inhibit NF-κB using in vitro and in vivo experimental models. Moreover, some examples of the clinical use of NF-κB inhibitors are discussed, primarily for the treatment of two B-cell malignancies, multiple myeloma and diffuse large B-cell lymphoma. Finally, the rationale and strategies for inhibiting specific NF-κB subunit activity for disease therapy are discussed.

The choice of the antigen in the dendritic cell-based vaccine therapy for prostate cancer

Tumor antigens (TA) are promising candidates for targeted treatment of prostate cancer (PCa). Critical issues in the preparation of dendritic cell (DC)-based TA vaccines are the DC maturation state and the appropriateness of the TA. Prostate-specific antigen (PSA) and prostate acide pshosphatase (PAP) presented by DC have produced encouraging results and PAP-loaded DCs are at late-stage development for PCa patients. TAs indispensable for tumor survival and propagation are now emerging as first choice TAs for future vaccines. The increased expression and enzymatic activity of prostate specific membrane antigen (PSMA) and prostate stem cell antigen (PSCA) by aggressive prostate tumors is indicative of a unique, selective advantage on the part of cells expressing them. Human telomerase reverse transcriptase (hTERT) and survivin are both involved in tumor cell survival and considered universal TAs. The T cell epitope potential of peptides derived from these TAs has been defined by computer-assisted prediction programs and has been tested in vitro and in vivo in terms of their ability to recruit cytotoxic T lymphocytes (CTL) and to be recognised as CTL targets. Results, reviewed here, show that anti-tumor immunity can be induced in vivo by DC loaded with both whole TAs and TA peptides. The promising, but still limited clinical success suggests further exploration of this immune therapy in the more appropriate setting of minimal disease. In advanced stages, vaccine can still be effective when combined with systemic or local cytoreductive therapies, which may overcome antigen specific tolerance and subvert the tumor immunosuppressive environment.

Emerging therapies for B-cell non-Hodgkin lymphoma

In recent years considerable progress has been made in the treatment of patients with B-cell non-Hodgkin lymphoma (NHL). Although responses can be achieved with combination chemotherapy regimens, a substantial proportion of patients are still not cured. In recent years, the knowledge of the cellular and molecular biology of distinct types of B-cell NHL have led to the development of a new class of drugs that specifically targets unique disease-specific pathways. This review will focus on novel therapies that are being developed for the treatment of B-cell NHL including those targeting the B-cell receptor signaling pathway, the proteasome, epigenetic lesions, novel anti-apoptotic drugs, new monoclonal antibodies and immunomodulatory drugs.

Essential role of MALT1 protease activity in activated B cell-like diffuse large B-cell lymphoma

A key element for the development of suitable anti-cancer drugs is the identification of cancer-specific enzymatic activities that can be therapeutically targeted. Mucosa-associated lymphoid tissue transformation protein 1 (MALT1) is a proto-oncogene that contributes to tumorigenesis in diffuse large B-cell lymphoma (DLBCL) of the activated B-cell (ABC) subtype, the least curable subtype of DLBCL. Recent data suggest that MALT1 has proteolytic activity, but it is unknown whether this activity is relevant for tumor growth. Here we report that MALT1 is constitutively active in DLBCL lines of the ABC but not the GCB subtype. Inhibition of the MALT1 proteolytic activity led to reduced expression of growth factors and apoptosis inhibitors, and specifically affected the growth and survival of ABC DLBCL lines. These results demonstrate a key role for the proteolytic activity of MALT1 in DLBCL of the ABC subtype, and provide a rationale for the development of pharmacological inhibitors of MALT1 in DLBCL therapy.

Anti-metastatic effects of liposomal gemcitabine in a human orthotopic LNCaP prostate cancer xenograft model

Fatal outcomes of prostate carcinoma (PCa) mostly result from metastatic spread rather than from primary tumor burden. Here, we monitored growth and metastatic spread of an orthotopic luciferase/GFP-expressing LNCaP PCa xenograft model in SCID mice by in vivo imaging and in vitro luciferase assay of tissues homogenates. Although the metastatic spread generally shows a significant correlation to primary tumor volumes, the susceptibility of various tissues to metastatic invasion was different in the number of affected animals as well as in absolute metastatic burden in the individual tissues. Using this xenograft model we showed that treatment with liposomal gemcitabine (GemLip) inhibited growth of the primary tumors (83.9 +/- 6.4%; P = 0.009) as well as metastatic burden in lymph nodes (95.6 +/- 24.0%; P = 0.047), lung (86.5 +/- 10.5%; P = 0.015), kidney (88.4 +/- 9.2%; P = 0.045) and stomach (79.5 +/- 6.6%; P = 0.036) already at very low efficient concentrations (8 mg/kg) as compared to conventional gemcitabine (360 mg/kg). Our data show that this orthotopic LNCaP xenograft PCa model seems to reflect the clinical situation characterized by the fact that at time of diagnosis, prostate neoplasms are biologically heterogeneous and thus, it is a useful model to investigate new anti-metastatic therapies.

Prostate stem cell antigen mRNA expression in preoperatively negative biopsy specimens predicts subsequent cancer after transurethral resection of the prostate for benign prostatic hyperplasia

BACKGROUND

Recent data showed that prostate stem cell antigen (PSCA) mRNA expression in transurethral resection of the prostate (TURP)-resected tissues predicted the subsequent prostate cancer after TURP in benign prostatic hyperplasia (BPH) patients with both PSA < 4.0 ng/ml and normal DRE findings. This study was to determine whether PSCA mRNA positivity in preoperatively negative prostatic biopsy samples from BPH men with PSA > 4.0 ng/ml and/or suspicious DRE findings had predictive performance following TURP.

MATERIALS AND METHODS

PSCA in situ hybridization was performed on negative prostatic biopsies taken before TURP from 166 enrolled symptomatic BPH patients, who were continuously followed for 5 years postoperatively. Predictive performance of PSCA mRNA for subsequent cancer onset was evaluated by univariate and multivariate Cox proportional hazards models with bootstrapping and concordance indices.

RESULTS

PSCA mRNA was detected in 42/166 (25.3%) of the preoperatively negative biopsy specimens, with a mean positive-labeling cells of 31.6%, in which 31 patients were identified as having subsequent PCa on follow-up. Of 124 patients with negative expression for PSCA mRNA none were subsequently diagnosed with PCa. The examination of Spearman's rank correlation coefficient showed that PSCA mRNA expression levels were positively and statistically correlated with higher Gleason score (r = 0.88, P < 0.001) and clinical T stage (r = 0.84, P < 0.001). A final multivariate Cox proportional hazards model demonstrated that only PSCA mRNA expression in negative prostatic biopsies was predictive of the subsequent cancer development after TURP (hazard ratio = 3.49; 95% CI: 2.02-4.75; P < 0.001), with the concordance index of 0.893.

CONCLUSIONS

This prospective study identifies PSCA mRNA in preoperatively negative prostatic biopsies as a significant predictor of subsequent cancer after TURP.

Expression of the gastrin-releasing peptide receptor, the prostate stem cell antigen and the prostate-specific membrane antigen in lymph node and bone metastases of prostate cancer

OBJECTIVE

Cell membrane antigens like the gastrin-releasing peptide receptor (GRPR), the prostate stem cell antigen (PSCA), and the prostate-specific membrane antigen (PSMA), expressed in prostate cancer, are attractive targets for new therapeutic and diagnostic applications. Therefore, we investigated in this study whether these antigens are expressed in metastasized prostate cancer.

METHODS

Formalin-fixed, paraffin-embedded specimens of 15 patients with uni- or bilateral lymph node metastases of prostate cancer (totaling 21 cases) and 17 patient-cases of bone metastases were processed for immunohistochemistry with anti-GRPR, anti-PSCA, and anti-PSMA antibodies. A pathologist blinded to clinical and pathological data scored the immunoreactivity for these antibodies on a four-point scale (0 = no staining; 1+ = weak staining; 2+ = moderate staining; 3+ = strong staining) and documented the distribution pattern.

RESULTS

GRPR staining in lymph node metastases was seen in 85.7% of cases (18 of 21 cases), PSCA in 95.2% (20/21), and PSMA in 100% (21/21). GRPR in bone metastases was seen in 52.9% of cases (9/17), PSCA in 94.1% (16/17), and PSMA in 100% (17/17).

CONCLUSION

We have shown for the first time that GRPR is expressed in the vast majority of lymph node metastases and in 52.9% of bone metastases of prostate cancer. PSCA and PSMA are both highly expressed in lymph node and bone metastases. Although PSCA and PSMA are mostly expressed in prostate cancer metastases, GRPR offers an interesting alternative target as it can be targeted relatively easy with peptide-based (radio)pharmaceuticals.

Immunohistochemical Expression of Prostate Stem Cell Antigen in Cystoprostatectomies with Incidental Prostate Cancer

High expression of Prostate Stem Cell Antigen (PSCA) has been shown to be associated with adverse prognostic features in clinically-diagnosed prostate cancer. The aim of this study is to analyze PSCA expression in cystoprostatectomies with incidental prostate carcinoma (PCa). PSCA expression was evaluated immunohistochemically in normal-looking epithelium (NEp), high-grade prostatic intraepithelial neoplasia (HGPIN) and pT2a Gleason score 6 acinar adenocarcinoma. The evaluation was carried out on 20 cystoprostatectomies (CyPs) with incidental PCa from men with bladder urothelial carcinoma (UC), and 20 radical prostatectomies (RPs) with hormonally untreated PCa from men with clinically detected PCa. Ki-67 was also investigated. The percentages of PSCA positive cells in HGPIN were significantly higher than in NEp (NEp: CyP, mean 2.92% ± standard deviation 6.26%; RP, 3.5% ± 6.46%. HGPIN: CyP, 13.67% ± 12.78%; RP, 14.67% ± 11.34%) (p<0.001). The proportions of positive cells in PCa were greater than in HGPIN (CyP, 20.25% ± 15.96%; RP, 22.58% ± 13.67%) (p0.001). For Ki-67 labeling, the proportions of positive nuclei in the CyPs significantly increased from NEp through HGPIN to PCa. A similar trend was seen in the RPs. In the CyPs the percentages of PSCA and Ki67 positive cells were lower than in the RPs, the differences between the CyP and RP compartments being not statistically significant. Our findings suggest that PSCA is a marker associated with neoplastic transformation of prostate cells, both in CyPs and RPs. However, there are no significant differences between CyPs with incidental prostate carcinoma and RPs with clinically diagnosed cancer.

IRF4: Immunity. Malignancy! Therapy?

IRF4, a member of the Interferon Regulatory Factor (IRF) family of transcription factors, is expressed in cells of the immune system, where it transduces signals from various receptors to activate or repress gene expression. IRF4 expression is a key regulator of several steps in lymphoid-, myeloid-, and dendritic-cell differentiation, including the differentiation of mature B cells into antibody-secreting plasma cells. IRF4 expression is also associated with many lymphoid malignancies, with recent evidence pointing to an essential role in multiple myeloma, a malignancy of plasma cells. Interference with IRF4 expression is lethal to multiple myeloma cells, irrespective of their genetic etiology, making IRF4 an "Achilles' heel" that may be exploited therapeutically.

Molecular imaging of prostate cancer

Prostate carcinoma is the most common non-cutaneous malignancy in males. Imaging of prostatic lesions is of great importance and aids in oncologic management and monitoring of therapy response. Particularly molecular imaging based on positron emission tomography (PET) and single photon emission computerized tomography (SPECT) has great potential. Using radio-labelled molecular probes, these approaches are highly sensitive and can provide key molecular and functional information on tumours. The identification of suitable targets based on unique genetic and biochemical features of cancer lesions is one of the core activities driving progress in molecular imaging of pathological processes. Nowadays, mainly metabolic probes are being used routinely for detection and staging of prostate cancer. The development of new specific receptor ligands and targeted probes and antibodies holds great promise to further enhance the performance of molecular imaging and to further improve the diagnosis and monitoring of prostate cancer.

Parallel multi-time point cell stimulation and lysis on-chip for studying early signaling events in T cell activation

Dynamics of complex signaling networks are important to many biological problems. Quantitative data at early time points after cellular stimulation are necessary for accurate model generation. However, the large amount of data needed is often extremely time-consuming and expensive to acquire with conventional methods. We present a two-module microfluidic platform for simultaneous multi-time point stimulation and lysis of T cells for early time point signaling activation with a resolution down to 20 s using only small amounts of cells and reagents. The key design features are rapid mixing of reagents and uniform splitting into eight channels for simultaneous collection of multi-time point data. Chaotic mixing was investigated via computational fluid dynamic modeling, and was used to achieve rapid and complete mixing. This modular device is flexible-with easy adjustment of the setup, a wide range of time points can be achieved. We show that treatment in the device does not elicit adverse cellular stress in Jurkat cells. The activation of six important proteins in the signaling cascade was quantified upon stimulation with a soluble form of alpha-CD3. The dynamics from device and conventional methods are similar, but the microdevice exhibits significantly less error between experiments. We envision this high-throughput format to enable simple and fast generation of large sets of quantitative data, with consistent sample handling, for many complex biological systems.

Recent prognostic factors in diffuse large B-cell lymphoma indicate NF-kappaB pathway as a target for new therapeutic strategies

The diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphoid cancer. The classical chemotherapy regimen given to these patients was the CHOP (Cyclophosphamide, Hydroxydaunorubicin or Adriamycin, Oncovin or Vincristine, Prednisone or Prednisolone), but recently rituximab with CHOP (R-CHOP) increased the number of cases responding to first line therapy. DLBCL classification identified three principle subgroups. The first one, named germinal centre B cell-like (GCB), responds to both CHOP and R-CHOP treatment and it is mainly characterised by the expression of markers like Bcl-6 and CD10. The second, the activated B-cell like (ABC), has a worse prognosis in comparison with GCB, and is mainly characterised by the expression of IRF-4, PRDM1 and NF-kappaB. It is interesting to notice that IRF-4 and PRDM1 are under the transcriptional control of NF-kappaB, whose high activation level is associated with a worse prognosis. The third one, mediastinal large B-cell lymphoma (PMBCL) is an uncommon subtype characteristically found in young females. Gene expression profiling suggests that this disease resembles Hodgkin lymphoma more than other types of DLBCL. The impact of rituximab on the outcome of patients with PMBCL has still not been fully assessed. It was seen that rituximab inhibits NF-kappaB pathway in vitro. However, the clinical significance of this finding is still unknown, because both ABC and GCB DLBCL show a significant improvement of overall survival after R-CHOP treatment. In this review, the NF-kappaB pathway is suggested as a target for new chemotherapy strategies based on the association of CHOP with molecules more effective than rituximab in this pathway inhibition.

Pathway activation in large B-cell non-Hodgkin lymphoma cell lines by doxorubicin reveals prognostic markers of in vivo response

The principal curative agent in the front-line treatment of patients with diffuse large B-cell lymphoma (DLBCL) is the anthracycline, doxorubicin. To define pathways that may have a functional role in the response of DLBCL in vivo to doxorubicin-based therapies, seven DLBCL cell lines were treated with doxorubicin and the cellular response evaluated. Expression profiling of responses revealed changes in levels of genes consistent with discrete pathway activation that were confirmed functionally. The two most sensitive cell lines (Ly3 and Ly10) displayed activation of the TP53 pathway but not in the remaining five (Ly1, Ly2, Ly4, Ly7 and Ly8), where TP53 mutations were identified. In this latter group, a G2/M delay was invoked. NF-kappaB pathway activation was evident in Ly1 which with Ly4 displayed the most chemoresistant response. Treatment of Ly1 after doxorubicin with the proteasomic inhibitor, bortezomib, additively increased the cytotoxic effect of doxorubicin. Chemoresistance of Ly4 was associated with loss of chromosome 2 (0-9 Mbp) that in vivo was highly correlated with adverse outcome. Thus, the response of DLBCL in vivo and in vitro is defined by several distinct molecular and genetic pathways which is, perhaps, not surprising given the heterogeneous clinical, morphologic and genetic nature of DLBCL.

Humanized radioiodinated minibody for imaging of prostate stem cell antigen-expressing tumors

PURPOSE

Prostate stem cell antigen (PSCA) is a cell surface glycoprotein that is overexpressed in prostate cancer, including hormone refractory disease. Previous preclinical studies showed the intact anti-PSCA antibodies, 1G8 and hu1G8, localized specifically to PSCA-expressing xenografts. Optimal micro positron emission tomography (microPET) imaging using hu1G8, however, required a delay of 168 hours postinjection. In this study, the 2B3 minibody (an 80-kDa engineered antibody fragment) has been produced for rapid targeting and imaging.

EXPERIMENTAL DESIGN

A gene encoding a PSCA-specific minibody, V(L)-linker-V(H)-hinge-huIgG1 C(H)3, was assembled. The minibody was expressed by secretion from mammalian cells and purified by cation exchange chromatography. Relative affinity and specificity were determined by competition ELISA and flow cytometry. Serial microPET imaging using a 124I-labeled minibody was conducted at 4 and 21 hours in mice bearing LAPC-9 AD, LAPC-9 AI, PC-3, and LNCaP-PSCA human prostate cancer xenografts. Tumor and tissue biodistribution was determined, and region of interest analysis of the images was conducted.

RESULTS

Yields of 20 mg/L purified 2B3 minibody were obtained that showed specific binding to LNCaP-PSCA cells. Purified 2B3 minibody showed specific binding to LNCaP-PSCA cells with an apparent affinity of 46 nmol/L. Radioiodinated 2B3 minibody showed rapid nontarget tissue and blood clearance kinetics (t1/2beta = 11.2 hours). MicroPET scanning using the 124I-2B3 minibody showed both androgen-dependent and -independent tumors as early as 4 hours and excellent high contrast images at 21 hours postinjection.

CONCLUSIONS

Imaging PSCA-positive prostate cancer is feasible using an intermediate size antibody fragment at 21 hours.

Compensatory IKKalpha activation of classical NF-kappaB signaling during IKKbeta inhibition identified by an RNA interference sensitization screen

A subtype of diffuse large B-cell lymphoma (DLBCL), termed activated B-cell-like (ABC) DLBCL, depends on constitutive nuclear factor-kappaB (NF-kappaB) signaling for survival. Small molecule inhibitors of IkappaB kinase beta (IKKbeta), a key regulator of the NF-kappaB pathway, kill ABC DLBCL cells and hold promise for the treatment of this lymphoma type. We conducted an RNA interference genetic screen to investigate potential mechanisms of resistance of ABC DLBCL cells to IKKbeta inhibitors. We screened a library of small hairpin RNAs (shRNAs) targeting 500 protein kinases for shRNAs that would increase the killing of an ABC DLBCL cell line in the presence of a small molecule IKKbeta inhibitor. Two independent shRNAs targeting IKKalpha synergized with the IKKbeta inhibitor to kill three different ABC DLBCL cell lines but were not toxic by themselves. Surprisingly, IKKalpha shRNAs blocked the classical rather than the alternative NF-kappaB pathway in ABC DLBCL cells, as judged by inhibition of IkappaBalpha phosphorylation. IKKalpha shRNA toxicity was reversed by coexpression of wild-type but not kinase inactive forms of IKKalpha, suggesting that IKKalpha may directly phosphorylate IkappaBalpha under conditions of IKKbeta inhibition. In models of physiologic NF-kappaB pathway activation by CARD11 or tumor necrosis factor-alpha, compensatory IKKalpha activity was also observed with IKKbeta inhibition. These results suggest that therapy for ABC DLBCL may be improved by targeting both IKKalpha and IKKbeta, possibly through CARD11 inhibition.

Detection of circulating tumor cells in prostate cancer patients: methodological pitfalls and clinical relevance

Disseminated malignancy is the major cause of prostate cancer-related mortality. Circulating tumor cells (CTCs) are essential for the establishment of metastasis. Various contemporary and molecular methods using prostate-specific biomarkers have been applied to detect extraprostatic disease that is undetectable by conventional imaging techniques, assessing the risk for disease recurrence after therapy of curative intent. However, the clinical relevance of CTC detection is still controversial. We review current literature regarding molecular methods used for the detection of CTCs in the peripheral blood and bone marrow biopsies of patients with prostate cancer, and we discuss the methodological pitfalls that influence the clinical significance of molecular staging.

Salvage chemotherapy and autologous stem cell transplantation are inferior for relapsed or refractory primary mediastinal large B-cell lymphoma compared with diffuse large B-cell lymphoma

Primary mediastinal large B-cell lymphoma (PMLCL) is an aggressive non-Hodgkin lymphoma with distinct clinical and gene expression profiles. Outcomes of salvage chemotherapy and autologous stem cell transplantation (ASCT) for relapsed or refractory disease (RR) have not been well characterised. We retrospectively identified 180 consecutive RR patients (37 PMLCL and a control group of 143 DLBCL) that underwent salvage chemotherapy. The overall response rate (ORR) to salvage chemotherapy (25% vs. 48%, p = 0.01) and 2-year OS after diagnosis of RR disease (15% vs. 34%, p = 0.018) was inferior in PMLCL patients. The 2-year post-ASCT OS (67% PMLCL vs. 53%, p = 0.78) and PFS (57% PMLCL vs. 36%, p = 0.64) were similar. RR PMLCL had an inferior ORR and survival compared with DLBCL but chemosensitive PMLCL and DLBCL patients have similar outcomes post-ASCT. Strategies for PMLCL should focus on identifying poor risk patients to test novel induction and salvage strategies.

Engineered humanized diabodies for microPET imaging of prostate stem cell antigen-expressing tumors

We have previously demonstrated preclinical in vivo targeting of prostate stem cell antigen (PSCA) using a humanized anti-PSCA 2B3 monoclonal antibody (mAb). However, humanization resulted in 5-fold loss of apparent affinity relative to the parental mAb (1 nM). In this study, diabodies (scFv dimers of 55 kDa) were generated from 2B3 including variants with different linker lengths as well as back-mutations to original murine residues to improve affinity. Parental 2B3 (p2B3) and back-mutated 2B3 (bm2B3) diabodies (Dbs) with five- or eight-amino acid linkers (p2B3-Db5, p2B3-Db8, bm2B3-Db5 and bm2B3-Db8) were evaluated for binding to PSCA by flow cytometry and affinities were determined by surface plasmon resonance. Back-mutation restored the affinity from 5.4 to 1.9 nM. Stability, evaluated by size exclusion, revealed that diabodies with eight-residue linkers existed as a mixture of dimeric and monomeric species at low concentrations (<or =1 mg/ml). Shortening the linker from eight to five residues improved dimer stability, notably in the bm2B3-Db8 compared with bm2B3-Db5. Both p2B3-Db8 and bm2B3-Db8 were radioiodinated with (124)I and evaluated by serial micro-positron emission tomography imaging in mice bearing LAPC-9 human prostate cancer xenografts. Localization in LAPC-9 xenografts was seen at 4 h, whereas at 20 h most of the activity had cleared from the tumor. Highest tumor-to-background contrast ratios and best images were obtained at 12 h. Although the higher affinity bm2B3-Db8 demonstrated improved tumor retention at later time points (20 h), it did not improve tumor targeting or imaging compared with p2B3-Db8 at 12 h.

Prostate stem cell antigen: a prospective therapeutic and diagnostic target

The development of novel clinical tools to combat cancer is an intense field of research and recent efforts have been directed at the identification of proteins that may provide diagnostic, prognostic and/or therapeutic applications due to their restricted expression. To date, a number of protein candidates have emerged as potential clinical tools in the treatment of prostate cancer. Discovered over ten year ago, prostate stem cell antigen (PSCA) is a cell surface antigen that belongs to the Ly-6/Thy-1 family of glycosylphosphatidylinositol-anchored proteins. PSCA is highly overexpressed in human prostate cancer, with limited expression in normal tissues, making it an ideal target for both diagnosis and therapy. Several studies have now clearly correlated the expression of PSCA with relevant clinical benchmarks, such as Gleason score and metastasis, while others have demonstrated the efficacy of PSCA targeting in treatment through various modalities. The purpose of this review is to present the current body of knowledge about PSCA and its potential role in the treatment of human prostate cancer.

Molecular subtypes of diffuse large B-cell lymphoma arise by distinct genetic pathways

Gene-expression profiling has been used to define 3 molecular subtypes of diffuse large B-cell lymphoma (DLBCL), termed germinal center B-cell-like (GCB) DLBCL, activated B-cell-like (ABC) DLBCL, and primary mediastinal B-cell lymphoma (PMBL). To investigate whether these DLBCL subtypes arise by distinct pathogenetic mechanisms, we analyzed 203 DLBCL biopsy samples by high-resolution, genome-wide copy number analysis coupled with gene-expression profiling. Of 272 recurrent chromosomal aberrations that were associated with gene-expression alterations, 30 were used differentially by the DLBCL subtypes (P < 0.006). An amplicon on chromosome 19 was detected in 26% of ABC DLBCLs but in only 3% of GCB DLBCLs and PMBLs. A highly up-regulated gene in this amplicon was SPIB, which encodes an ETS family transcription factor. Knockdown of SPIB by RNA interference was toxic to ABC DLBCL cell lines but not to GCB DLBCL, PMBL, or myeloma cell lines, strongly implicating SPIB as an oncogene involved in the pathogenesis of ABC DLBCL. Deletion of the INK4a/ARF tumor suppressor locus and trisomy 3 also occurred almost exclusively in ABC DLBCLs and was associated with inferior outcome within this subtype. FOXP1 emerged as a potential oncogene in ABC DLBCL that was up-regulated by trisomy 3 and by more focal high-level amplifications. In GCB DLBCL, amplification of the oncogenic mir-17-92 microRNA cluster and deletion of the tumor suppressor PTEN were recurrent, but these events did not occur in ABC DLBCL. Together, these data provide genetic evidence that the DLBCL subtypes are distinct diseases that use different oncogenic pathways.

Cancer stem cells in prostate adenocarcinoma: a target for new anticancer strategies

Prostate cancer (PC) is major common malignancy in males in most industrialized Western countries, where it is the most commonly diagnosed cancer affecting men after middle age (>50 years). Over 90% of PC patients with incurable disease respond to primary treatment, which consists of intervention to lower serum testosterone. However, the duration of response is short (12-33 months) and in almost all patients, is followed by the emergence of a phenotype resistant to androgen deprivation in therapy (known as hormone or androgen-resistant PC). Considerable research efforts have been directed towards the identification of markers associated with the initiation and progression of PC, yet there is little consensus about the target cell within prostate epithelium that is susceptible to malignant transformation. Stem cells may represent a major target for mutations leading to cancer as their longevity assures continued presence during the long latency between carcinogenic agents exposure and cancer development. Therefore in order to allow the development of more effective treatment strategies for PC, a better understanding of the molecular changes that underlie cancer stem cells is required.

Targeting transcription factors for therapeutic benefit

Transcription factors are a large class of biological molecules that are important for health and disease. Despite that there are challenges to targeting them therapeutically and most approaches alter their activity indirectly. Research at the chemical biology interface has led to the development of new ways of targeting transcription factors including blocking transcription factor dimerisation, targeting specific DNA sequences and DNA decoys. This review discusses these issues with a view to inspiring the development of new agents that could be useful for the treatment of cancer.

B-cell lymphoma 6 and the molecular pathogenesis of diffuse large B-cell lymphoma

PURPOSE OF REVIEW

The B-cell lymphoma 6 transcriptional repressor is the most commonly involved oncogene in B-cell lymphomas. Sustained expression of B-cell lymphoma 6 causes malignant transformation of germinal center B cells. Understanding the mechanism of action of B-cell lymphoma 6 is crucial for the study of how aberrant transcriptional programming leads to lymphomagenesis and development of targeted antilymphoma therapy.

RECENT FINDINGS

Identification of B-cell lymphoma 6 target genes indicates a critical role for B-cell lymphoma 6 in facilitating a state of physiological genomic instability required for germinal center B cells to undergo affinity maturation, and suggests its contribution to several additional cellular functions. The discovery of several layers of counterregulatory mechanisms reveals how B cells can control and fine-tune the potentially lymphomagenic actions of B-cell lymphoma 6. From the biochemical standpoint, B-cell lymphoma 6 can regulate distinct biological pathways through different cofactors. This observation explains how the biological actions of B-cell lymphoma 6 can be physiologically controlled through separate mechanisms and affords the means for improved therapeutic targeting. The fact that patients with B-cell lymphoma 6-dependent lymphoma can be identified on the basis of gene signatures suggests that therapeutic trials of B-cell lymphoma 6 inhibitors could be personalized to these individuals.

SUMMARY

B-cell lymphoma 6 plays a fundamental role in lymphomagenesis and is an excellent therapeutic target for development of improved antilymphoma therapeutic regimens.

Bortezomib in mantle cell lymphoma

Mantle cell lymphoma (MCL) represents 6% of non-Hodgkin lymphomas, but is one of the most active fields of clinical investigation. Unfortunately, there is still no standard or curative therapy in MCL. Front-line therapy appears to benefit from intensification either through high-dose therapy with stem cell transplant consolidation or dose-intense chemotherapy with hyperfractionated cyclophosphamide, vincristine, adriamycin/doxorubicin and dexamethasone/rituximab. Most patients still relapse and a multitude of novel agents are currently being tested in this setting, including proteasome inhibitors with bortezomib (the first of its class and the first US FDA-approved drug for MCL), mTOR inhibitors, Bcl-2 inhibitors, antiangiogenesis agents and histone deacetylase inhibitors among others. An obvious effort is needed to enroll patients on clinical trials, the design of which might benefit from pharmacogenomics and a better understanding of MCL biology and its diversity.

Deletion of PSCA increases metastasis of TRAMP-induced prostate tumors without altering primary tumor formation

BACKGROUND

Prostate stem cell antigen (PSCA) is expressed in normal epithelium of various tissues, in embryos and adult animals. PSCA expression is upregulated in up to 70% of prostate tumors and metastases, and a subset of bladder and pancreatic cancers. However, its function is unknown. We studied the effect of targeted gene deletion of PSCA on normal organ development and prostate carcinogenesis.

METHODS

PSCA +/+, PSCA +/-, and PSCA -/- mice were bred and aged to 22 months. A cohort of animals was treated with gamma-irradiation at 2 and 6 months of age. PSCA knockout mice were crossed to TRAMP mice and TRAMP+ PSCA +/+, TRAMP+ PSCA +/-, and TRAMP+ PSCA -/- mice and offspring aged to 10 months of age. Tissues were analyzed by RT-PCR, histology, and immunohistochemistry for markers of proliferation, apoptosis, angiogenesis, and tumor progression.

RESULTS

PSCA knockout animals were viable, fertile and indistinguishable from wild-type littermates. Spontaneous or radiation-induced primary epithelial tumor formation was also similar in wild-type and PSCA knockout mice. We observed an increased frequency of metastasis in TRAMP+ PSCA heterozygous and knockout mice, compared to TRAMP+ wild-type mice. Metastases were largely negative for PSCA and androgen receptor. Cleaved-caspase 3 and CD31 staining was similar in all genotypes. Aurora-A and Aurora-B kinases were detected in the cytoplasm of PSCA heterozygous and knockout tumors, suggesting aberrant kinase function.

CONCLUSION

These data suggest that PSCA may play a role in limiting tumor progression in certain contexts, and deletion of PSCA may promote tumor migration and metastasis.

The association of prostate stem cell antigen (PSCA) mRNA expression and subsequent prostate cancer risk in men with benign prostatic hyperplasia following transurethral resection of the prostate

BACKGROUND

Prior data showed prostate stem cell antigen (PSCA) mRNA expression in benign prostatic hyperplasia (BPH) tissues. The purpose of the present investigation was to determine whether PSCA mRNA expression in resected BPH samples was associated with the subsequent presence of cancer following transurethral resection of the prostate (TURP).

METHODS

PSCA in situ hybridization was performed on the TURP-resected tissues from 288 patients, who were histopathologically confirmed BPH without cancer. All these patients were continuously followed for 9-70 months postoperatively. Univariate and multivariate cox regression analyses were used to evaluate the predictive performance of PSCA mRNA for subsequent cancer onset following TURP.

RESULTS

PSCA mRNA was detected in 93/288 (32.3%) of the resected BPH specimens, with a mean positive-labeling cells of 23.8%, in which 22 patients (23.7%) were identified as having PCa on follow-up. Of 195 patients with negative expression for PSCA mRNA 2 (1.0%) were subsequently found with PCa. PSCA mRNA expression levels were directly proportional to higher Gleason score and clinical T stage. Univariate and multivariate cox regression analyses demonstrated that only PSCA mRNA expression was predictive of the subsequent cancer development after TURP, however, PSA velocity was an univariately significant but not multivariately significant predictor.

CONCLUSIONS

This prospective study identifies PSCA mRNA in BPH as a significant predictor of cancer development after TURP, suggesting that PSCA may be used to identify patients who are at high risk for subsequent cancer onset following TURP for BPH and the PSCA test may be useful when applied for repeat biopsies.

Identification of N-(quinolin-8-yl)benzenesulfonamides as agents capable of down-regulating NFkappaB activity within two separate high-throughput screens of NFkappaB activation

We describe here a series of N-(quinolin-8-yl)benzenesulfonamides capable of suppressing the NFkappaB pathway identified from two high-throughput screens run at two centers of the NIH Molecular Libraries Initiative. These small molecules were confirmed in both primary and secondary assays of NFkappaB activation and expanded upon through analogue synthesis. The series exhibited potencies in the cell-based assays at as low as 0.6 microM, and several indications suggest that the targeted activity lies within a common region of the NFkappaB pathway.

Monoclonal antibody therapy for prostate cancer

Early detection of prostate cancer (PCa) and advances in hormonal and chemotherapy treatments have provided great clinical benefits to patients with early stages of the disease. However, a significant proportion of patients still progress to advanced, metastatic disease, for which no effective therapies are available. Therefore, there is a critical need for new treatment modalities, ideally targeted specifically to prostate cancer cells. The recent clinical and commercial successes of monoclonal antibodies (MAbs) have made them the most rapidly expanding class of therapeutics being developed for many disease indications, including cancer. PCa is well suited for antibody-based therapy due to the size and location of recurrent and metastatic tumors, and the lack of necessity to avoid targeting the normal prostate, a nonessential organ. These properties have fostered interest in the development and clinical evaluation of therapeutic MAbs directed to both well established and newly discovered targets in PCa. MAbs directed to established targets include those approved for other solid tumors, including anti-human epidermal growth factor receptor-2 (HER2) MAb trastuzumab, anti-epidermal growth factor receptor (EGFR) MAbs cetuximab and panitumumab, and the antivascular endothelial growth factor (VEGF) MAb bevacizumab. Genomics efforts have yielded a large number of novel, clinically relevant targets in PCa with the desirable expression profiling in tumor and normal tissues, and with an implicated role in tumor growth and spread. Growing efforts are directed to the development of naked or payload-conjugated therapeutic antibodies to these targets, and a variety of MAb products are currently progressing through preclinical and various stages of clinical development. The clinical experience with some of the commercialized MAb products points out specific challenges in conducting clinical trials with targeted therapy in PCa.

Targeting aggressive B-cell lymphomas with cell-penetrating peptides

DLBCL (diffuse large B-cell lymphoma) is the most common subtype of non-Hodgkin's lymphoma. Current therapy for patients includes chemotherapy and monoclonal antibodies. Although oncogene-targeted therapy is dramatically successful for patients with certain kinds of leukaemias, there are no such agents yet for DLBCL. One reason for this is that several key oncogenes involved in DLBCL pathogenesis are transcription factors, which are difficult to therapeutically target with small molecules. Recent advances in the structural and functional characterization of DLBCL oncogenes have facilitated design of CPPs (cellpenetrating peptides) with potent inhibitory effects on DLBCL and other aggressive lymphomas. CPPs targeting the Bcl (B-cell lymphoma)-6, Bcl-2, Myc and NF-κB (nuclear factor κB) oncogenic pathways, among others, could improve efficacy and reduce toxicity of anti-lymphoma therapy. Another barrier towards effective therapy in DLBCL is its profound molecular heterogeneity. Combinatorial administration of oncogene-targeted CPPs based on the molecular profiles of individual patient tumours could allow individualized targeted therapy regimens to be developed.

Targeting of tumor cells expressing the prostate stem cell antigen (PSCA) using genetically engineered T-cells

BACKGROUND

Curative therapeutic options for minimal residual disease or advanced tumor stages in prostate cancer (PCa) are still missing. Adoptive transfer of cytotoxic T-cells that have been polyclonally rendered tumor-specific by genetic engineering appears to be a promising immunotherapeutic strategy. Among the numerous prostate tissue/tumor antigens identified during the last years, the "prostate stem cell antigen" (PSCA) is an attractive immunotherapeutic target. It is broadly expressed on the surface of primary PCa cells as well as on PCa metastases.

METHODS

To generate a chimeric T-cell receptor (TCR) recognizing PSCA, a monoclonal anti-PSCA antibody was raised and a single-chain fragment (scFv) was prepared. The resulting anti-PSCA scFv 7F5 was fused to the beta2 constant region derived from the beta-chain of a TCR and to the CD3zeta-signaling domain.

RESULTS

The chimeric alpha-PSCA-beta2/CD3zeta-TCR, expressed in Jurkat cells, was phosphorylated in the ITAMs of the CD3-zeta chain upon cross-linking by insolublized PSCA. When transduced into a mouse cytotoxic T-cell line, the chimeric receptor specifically activated cytotoxicity against PSCA-positive tumor cells.

CONCLUSIONS

We developed a functional chimeric TCR against PSCA for treatment of PCa. The chimeric alpha-PSCA-beta2/CD3zeta-TCR might now be used for arming human cytotoxic T-cells for further studies towards a clinical treatment of PCa.

A library of gene expression signatures to illuminate normal and pathological lymphoid biology

Genomics has provided a lever to pry open lymphoid cells and examine their regulatory biology. The large body of available gene expression data has also allowed us to define the of coordinately expressed genes, termed gene expression signatures, which characterize the states of cellular physiology that reflect cellular differentiation, activation of signaling pathways, and the action of transcription factors. Gene expression signatures that reflect the action of individual transcription factors can be defined by perturbing transcription factor function using RNA interference (RNAi), small-molecule inhibition, and dominant-negative approaches. We have used this methodology to define gene expression signatures of various transcription factors controlling B-cell differentiation and activation, including BCL-6, B lymphocyte-induced maturation protein-1 (Blimp-1), X-box binding protein-1 (XBP1), nuclear factor-kappaB (NF-kappaB), and c-myc. We have also curated a wide variety of gene expression signatures from the literature and assembled these into a signature database. Statistical methods can define whether any signature in this database is differentially expressed in independent biological samples, an approach we have used to gain mechanistic insights into the origin and clinical behavior of B-cell lymphomas. We also discuss the use of genomic-scale RNAi libraries to identify genes and pathways that may serve as therapeutic targets in B-cell malignancies.

External beam radiotherapy (EBRT) suppressed prostate stem cell antigen (PSCA) mRNA expression in clinically localized prostate cancer

BACKGROUND

Prostate stem cell antigen (PSCA), a recently identified glycosylphosphatidylinositol (GPI)-anchored cell surface protein belonging to the Thy-1/Ly-6 family of cell surface antigens, is overexpressed in human prostate cancer (PCa). Our recent data indicated that complete androgen ablation could significantly suppress PSCA mRNA expression in primarily organ-confined PCa. The effect of external beam radiotherapy (EBRT), one of the curative treatment options for localized PCa, on tumor PSCA mRNA expression has not been elucidated. The purpose of the present study was to investigate the variations in the expression levels of PSCA mRNA before and after EBRT, and further evaluate the prognostic value of PSCA in this disease.

MATERIALS AND METHODS

Between January 1999 and June 2005, 87 men with clinically localized adenocarcinoma of the prostate received only EBRT with a total dose of 65-70 Gy for 6.5-7 weeks. PSCA in situ hybridization (ISH) was performed on the cancerous pretreatment biopsy or transurethral resection of prostate (TURP) tissue and post-treatment biopsy tissue of all 87 men, respectively. Tumor cytoplasmic staining of PSCA mRNA was evaluated by two independent pathologists and the differences of PSCA mRNA expression levels between the samples before and after EBRT were analyzed using the Student's t-test. Twenty-four to seventy months continuous follow-up studies after treatment were performed and aimed at assessing the correlation of PSCA mRNA expression level with biochemical relapse and/or distant metastases from the cancer.

RESULTS

The percent of cells positive for PSCA mRNA by ISH labeling declined from 71.2% (0-93%) +/- 9.7% before EBRT to 30.7% (0-90%) +/- 5.3% after EBRT (P<0.001). Before EBRT, 81 of 87 cases (93.1%) were positive for PSCA mRNA labeling, however, after EBRT the percentage of positive reactivity of PSCA mRNA was decreased to 62 of 81 cases (76.5%), in which 59 men (95.2%) were found without biochemical relapse or distant metastases on follow-up. This decline in PSCA mRNA labeling was directly proportional to higher pretreatment serum PSA level, higher tumor grade (Gleason score), and higher clinical T stage. The rest 19 cases had the increased percentage of cells positive for PSCA mRNA after EBRT, in which 15 cases developed biochemical relapse and/or distant metastases from tumor on follow-up.

CONCLUSIONS

We found that EBRT for PCa can significantly suppress PSCA mRNA expression and the elevated PSCA mRNA level after EBRT may be a clinically adverse predictor for tumor progression.

A cell-based assay for IkappaBalpha stabilization using a two-color dual luciferase-based sensor

A cell-sensor assay for stabilization of IkappaBalpha was developed in the activated B cell-like diffuse large B-cell lymphoma cell line OCI-Ly3. This cell line expresses known nuclear factor kappaB (NFkappaB) target genes due to high constitutive activity of IkappaB kinase (IKK), which phosphorylates the protein IkappaBalpha leading to proteasomal degradation of IkappaBalpha and activation of NFkappaB. The cell-sensor assay uses green and red light-emitting beetle luciferases, with the green luciferase fused to IkappaBalpha (IkappaBalpha-CBG68) and the red luciferase (CBR) present in its native state. The IkappaBalpha-CBG68 reporter functions as a sensor of IKK and proteasome activity, while CBR serves to normalize for cell number and nonspecific effects. Both reporter constructs were stably integrated and placed under the control of an inducible promoter system, which increased fold responsiveness to inhibitors when assay incubations were performed simultaneous to reporter induction by doxycycline. The assay was miniaturized to a 1,536-well plate format and showed a Z' of 0.6; it was then used to panel 2,677 bioactive compounds by a concentration-response-based screening strategy. The concentration-effect curves for the IkappaBalpha-CBG68 and CBR signals were then used to identify specific stabilizers of IkappaBalpha, such as IKK inhibitors or proteasome inhibitors, which increased the doxycycline-induced rise in IkappaBalpha-CBG68 without affecting the rise in CBR. Known and unexpected inhibitors of NFkappaB signaling were identified from the bioactive collection. We describe here the development and performance of this assay, and discuss the merits of its specific features.

NF-kappa B as a target for cancer therapy

NF-kappaB transcription factors and the signaling pathways that activate them play a critical role in cancer development, progression and therapy, and recently have become a focal point for intense drug discovery and development efforts. This article presents a critical review on the different types of inhibitors targeting the NF-kappaB pathway at several stages.

Downregulation of Bfl-1 protein expression sensitizes malignant B cells to apoptosis

Elevated expression of the antiapoptotic protein Bfl-1 (A1) was previously reported in several cancer cell lines. Recently, molecular profiling of large B-cell lymphoma identified Bfl-1 as a gene signature in 'OxPhos' diffuse large B-cell lymphoma subtype and in primary mediastinal large B-cell lymphoma, suggesting that in addition to Bcl-2, Bcl-xL and Mcl-1, Bfl-1 may be a relevant target in the design of new strategies for cancer therapy. Using short hairpin RNA strategy, we show here that Bfl-1 silencing in one lymphoblastoid B-cell line and in two diffuse large B-cell lymphoma cell lines potently induces their apoptosis and sensitizes those cell lines to anti-CD20 (Rituximab)-mediated cell death as well as to apoptosis induced by chemotherapeutic molecules such as doxorubicin, vincristine, cisplatin and fludarabine. These results demonstrate for the first time that Bfl-1 is an essential protein for survival of malignant B cells and suggest Bfl-1 may represent a potential target for future drug development against B cell lymphoma.

MicroRNA-155 is induced during the macrophage inflammatory response

The mammalian inflammatory response to infection involves the induction of several hundred genes, a process that must be carefully regulated to achieve pathogen clearance and prevent the consequences of unregulated expression, such as cancer. Recently, microRNAs (miRNAs) have emerged as a class of gene expression regulators that has also been linked to cancer. However, the relationship between inflammation, innate immunity, and miRNA expression is just beginning to be explored. In the present study, we use microarray technology to identify miRNAs induced in primary murine macrophages after exposure to polyriboinosinic:polyribocytidylic acid or the cytokine IFN-beta. miR-155 was the only miRNA of those tested that was substantially up-regulated by both stimuli. It also was induced by several Toll-like receptor ligands through myeloid differentiation factor 88- or TRIF-dependent pathways, whereas up-regulation by IFNs was shown to involve TNF-alpha autocrine signaling. Pharmacological inhibition of the kinase JNK blocked induction of miR-155 in response to either polyriboinosinic:polyribocytidylic acid or TNF-alpha, suggesting that miR-155-inducing signals use the JNK pathway. Together, these findings characterize miR-155 as a common target of a broad range of inflammatory mediators. Importantly, because miR-155 is known to function as an oncogene, these observations identify a potential link between inflammation and cancer.