Targeting the lymphotoxin-beta receptor with agonist antibodies as a potential cancer therapy

Clinical targeting of the TNF and TNFR superfamilies

Inhibitors of tumour necrosis factor (TNF) are among the most successful protein-based drugs (biologics) and have proven to be clinically efficacious at reducing inflammation associated with several autoimmune diseases. As a result, attention is focusing on the therapeutic potential of additional members of the TNF superfamily of structurally related cytokines. Many of these TNF-related cytokines or their cognate receptors are now in preclinical or clinical development as possible targets for modulating inflammatory diseases and cancer as well as other indications. This Review focuses on the biologics that are currently in clinical trials for immune-related diseases and other syndromes, discusses the successes and failures to date as well as the expanding therapeutic potential of modulating the activity of this superfamily of molecules.

Orthotopic mouse models expressing fluorescent proteins for cancer drug discovery

IMPORTANCE OF THE FIELD

Currently used rodent tumor models, including transgenic tumor models, or subcutaneously growing human tumors in immunodeficient mice, do not sufficiently represent clinical cancer, especially with regard to metastasis and drug sensitivity.

AREAS COVERED IN THIS REVIEW

To obtain clinically accurate models, we have developed the technique of surgical orthotopic implantation (SOI) to transplant histologically intact fragments of human cancer, including tumors taken directly from the patient, to the corresponding organ of immunodeficient rodents. SOI allows the growth and metastatic potential of the transplanted tumors to be expressed and reflects clinical cancer of all types. Effective drugs can be discovered and evaluated in the SOI models utilizing human tumor cell lines and patient tumors. Visualization of many aspects of cancer initiation and progression in vivo has been achieved with fluorescent proteins. Tumors and metastases in the SOI models that express fluorescent proteins can be visualized noninvasively in intact animals, greatly facilitating drug discovery.

WHAT THE READER WILL GAIN

This review will provide information on the imageable mouse models of cancer that are clinically relevant, especially regarding metastasis and their use for drug discovery and evaluation.

TAKE HOME MESSAGE

SOI mouse models of cancer reproduce the features of clinical cancer.

The anti-Fn14 antibody BIIB036 inhibits tumor growth in xenografts and patient derived primary tumor models and enhances efficacy of chemotherapeutic agents in multiple xenograft models

Agonistic antibodies targeting Fn14, the receptor for TWEAK, have demonstrated anti-tumor activity in xenograft models. Herein, we further explore the therapeutic potential of the humanized anti-Fn14 agonistic antibody, BIIB036, as a single agent and in combination with standard of care cancer therapeutics. Pharmacokinetic studies of BIIB036 in tumor-bearing mice revealed a half-life of approximately three days suggesting twice a week dosing would be necessary to maintain efficacy. However, in multiple xenograft models, BIIB036 treatment resulted in extended tumor growth inhibition up to 40-50 d following cessation of dosing, suggesting that frequent administration of BIIB036 may not be necessary to maintain prolonged anti-tumor activity. Subsequent xenograft studies revealed that maximal efficacy was achieved with BIIB036 dosing once every two weeks, by either intraperitoneal or subcutaneous administration. Xenograft tumors that were initially treated with BIBI036 and then re-grew up to 1000 mm³ following cessation of the first cycle of treatment remained sensitive to a second cycle of treatment. BIIB036 was also evaluated in patient derived primary colon tumor models, where efficacy compared favorably with a standard of care agent. Lastly, BIIB036 enhanced the efficacy of several standard of care chemotherapeutics, including paclitaxel in MDA-MBA-231 breast tumor xenografts, paclitaxel or carboplatin in HOP62 non-small cell lung xenografts, and 5-FU in NCI-N87 gastric xenografts, with no overlapping toxicities. These studies thus establish BIIB036 as a promising therapeutic agent with durable anti-tumor activity in human xenografts as well as patient derived primary tumor models, and enhanced activity and tolerability in combination with standard of care chemotherapeutics. Taken together, the data presented herein suggest that BIIB036 warrants evaluation in the clinic.

NSCLC and the alternative pathway of NF-κB: uncovering an unknown relation

Lung cancer is the leading cause of cancer-related deaths worldwide. Although our knowledge on the pathobiology of the disease has increased in the last decades, the prognosis of lung cancer patients has hardly changed. Many signaling pathways are implicated in lung carcinogenesis, but the role of the alternative pathway of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in lung cancer pathogenesis and progression has not been investigated. The aim of our study was to investigate the role of this pathway in non-small cell lung cancer (NSCLC) patients. NF-κB2 and RelB protein expression was retrospectively assessed by immunohistochemistry in tissue samples from 109 NSCLC patients. RelB and NF-κB2 protein levels differed between tumors and adjacent nonneoplastic lung parenchyma. Cytoplasmic immunoreactivity of NF-κB2 and RelB was correlated with tumor stage (p = 0.03 and p = 0.016, respectively). In addition, cytoplasmic NF-κB2 levels were related to tumor grade (p = 0.046). Expression of RelB in the cytoplasm was tumor histologic type-specific, with squamous cell carcinomas having the highest protein levels. Nuclear expression of RelB and NF-κB2 differed between tumor and nonneoplastic tissues, possibly indicating activation of the alternative pathway of NF-κB in cancer cells. Moreover, lymph node metastasis was related to nuclear NF-κB2 expression in tumor cells. The deregulation of the alternative NF-κB pathway in NSCLC could play a role in the development and progression of the disease.

Lymphotoxin and the amazing technicolor circus of intestinal homeostasis

Recently a new lymphocyte subset called innate lymphoid cells has emerged and it includes key producers of interleukin (IL)-17 and IL-22 in the mucosal environment. Using Citrobacter rodentium infection to deliver a pathogenic insult to the colon, two studies have revealed an underlying role for lymphotoxin-β receptor signaling in the generation of IL-22 by these cells. This observation links a system well known for its ability to organize lymphoid microenvironments into a basic mucosal response.

Sub-lethal irradiation of human colorectal tumor cells imparts enhanced and sustained susceptibility to multiple death receptor signaling pathways

Background

Death receptors (DR) of the TNF family function as anti-tumor immune effector molecules. Tumor cells, however, often exhibit DR-signaling resistance. Previous studies indicate that radiation can modify gene expression within tumor cells and increase tumor cell sensitivity to immune attack. The aim of this study is to investigate the synergistic effect of sub-lethal doses of ionizing radiation in sensitizing colorectal carcinoma cells to death receptor-mediated apoptosis.

Methodology/Principal Findings

The ability of radiation to modulate the expression of multiple death receptors (Fas/CD95, TRAILR1/DR4, TRAILR2/DR5, TNF-R1 and LTβR) was examined in colorectal tumor cells. The functional significance of sub-lethal doses of radiation in enhancing tumor cell susceptibility to DR-induced apoptosis was determined by in vitro functional sensitivity assays. The longevity of these changes and the underlying molecular mechanism of irradiation in sensitizing diverse colorectal carcinoma cells to death receptor-mediated apoptosis were also examined. We found that radiation increased surface expression of Fas, DR4 and DR5 but not LTβR or TNF-R1 in these cells. Increased expression of DRs was observed 2 days post-irradiation and remained elevated 7-days post irradiation. Sub-lethal tumor cell irradiation alone exhibited minimal cell death, but effectively sensitized three of three colorectal carcinoma cells to both TRAIL and Fas-induced apoptosis, but not LTβR-induced death. Furthermore, radiation-enhanced Fas and TRAIL-induced cell death lasted as long as 5-days post-irradiation. Specific analysis of intracellular sensitizers to apoptosis indicated that while radiation did reduce Bcl-X_L and c-FLIP protein expression, this reduction did not correlate with the radiation-enhanced sensitivity to Fas and/or TRAIL mediated apoptosis among the three cell types.

Conclusions/Significance

Irradiation of tumor cells can overcome Fas and TRAIL resistance that is long lasting. Overall, results of these investigations suggest that non-lethal doses of radiation can be used to make human tumors more amenable to attack by anti-tumor effector molecules and cells.

Lymphatics: at the interface of immunity, tolerance, and tumor metastasis

The lymphatic system has long been accepted as a passive escape route for metastasizing tumor cells. The classic view that lymphatics solely regulate fluid balance, lipid metabolism, and immune cell trafficking to the LN is now being challenged. Research in the field is entering a new phase with increasing evidence suggesting that lymphatics play an active role modulating inflammation, autoimmune disease, and the anti-tumor immune response. Evidence exists to suggest that the lymphatics and chemokines guide LN bi-functionally, driving immunity vs. tolerance according to demand. At sites of chronic inflammation, autoimmunity, and tumors, however, the same chemokines and aberrant lymphangiogenesis foster disease progression. These caveats point to the existence of a complex, finely balanced relationship between lymphatics and the immune system in health and disease. This review discusses emerging concepts in the fields of immunology, tumor biology, and lymphatic physiology, identifying critical, overlapping functions of lymphatics, the LN and lymphoid factors in tipping the balance of immunity vs. tolerance in favor of a growing tumor.

Lymphotoxin-β receptor activation by lymphotoxin-α(1)β(2) and LIGHT promotes tumor growth in an NFκB-dependent manner

Lymphotoxin beta receptor (LTβR) activation on mouse fibrosarcoma cells (BFS-1) results in enhanced solid tumor growth paralleled by increased angiogenesis induced by the expression of pro-angiogenic CXCL2. In our study, we demonstrate that both functional ligands of the LTβR, namely LTα(1) β(2) and LIGHT, are involved in the activation of LTβR in solid fibrosarcomas. To identify whether the lymphocyte population is involved in the activation of LTβR in these fibrosarcoma tumors, we used conditional LTβ-deficient mice that specifically lack LTβ expression either on T cells (T-LTβ(-/-)) or on B cells (B-LTβ(-/-)). Solid tumor growth was reduced in both mouse strains when compared to tumor growth in wild-type mice, indicating the participation of both T and B host lymphocytes in the activation of LTβR in these tumors. Tumor growth was also reduced in LIGHT-deficient mice, suggesting a contribution of this ligand to the activation of LTβR in BFS-1 fibrosarcomas. LTβR signaling can involve IκBα and/or NFκB-inducing kinase (NIK) for subsequent NFκB activation in different types of cells. Expression of a dominant negative form of IκBα or of a dominant negative mutant of NIK resulted in decreased activation of NFκB signaling and reduced expression of pro-angiogenic CXCL2 in vitro. Moreover, expression of dominant negative form of NIK or an IκBα repressor in these fibrosarcoma cells resulted in reduced solid tumor growth in vivo, suggesting that both IκBα and NIK are involved in pro-angiogenic signaling after LTβR activation. Our data support the idea that the ablation of LTβR signaling should be considered for cancer treatment.

LTβR signaling in dendritic cells induces a type I IFN response that is required for optimal clonal expansion of CD8+ T cells

During an immune response, antigen-bearing dendritic cells (DCs) migrate to the local draining lymph node and present antigen to CD4(+) helper T cells. Antigen-activated CD4(+) T cells then up-regulate TNF superfamily members including CD40 ligand and lymphotoxin (LT)αβ. Although it is well-accepted that CD40 stimulation on DCs is required for DC licensing and cross-priming of CD8(+) T-cell responses, it is likely that other signals are integrated into a comprehensive DC activation program. Here we show that a cognate interaction between LTαβ on CD4(+) helper T cells and LTβ receptor on DCs results in unique signals that are necessary for optimal CD8(+) T-cell expansion via a type I IFN-dependent mechanism. In contrast, CD40 signaling appears to be more critical for CD8(+) T-cell IFNγ production. Therefore, different TNF family members provide integrative signals that shape the licensing potential of antigen-presenting DCs.

Enhancing cytotoxic and apoptotic effect in OVCAR-3 and MDAH-2774 cells with all-trans retinoic acid and zoledronic acid: a paradigm of synergistic molecular targeting treatment for ovarian cancer

Background

Ovarian cancer is the most fatal gynecologic malignancies in the world. Although, platinum based treatments are widely used, the disease becomes treatment refractory within two years, and novel treatment options should be searched. All- trans retinoic acid (ATRA) induces growth arrest, differentiation and cell death in some types of cancer cells and its combination with various anticancer agents results in enhanced cytotoxicity. Zoledronic acid is a common bisphosphonate known for its anticancer effects beyond its current use in the treatment of cancer-induced bone disease. We aimed to investigate the possible additive/synergistic effect of both agents in OVCAR-3 and MDAH-2774 ovarian cancer cell lines, since both agents show superiority to conventional cytotoxics in terms of adverse events.

Methods

XTT cell proliferation assay was used for showing cytotoxicity. For verifying apoptosis, both DNA Fragmentation by ELISA assay and caspase 3/7 activity measurement were used. OligoGeArray^® which consists of 112 apoptosis related genes was used to elucidate the genetic changes within cancer cells. To validate our oligoarray results, quantitative real-time PCR was performed on four selected genes that were maximally effected by the combination treatment: lymphotoxin beta receptor (LTBR), myeloid cell leukemia-1 (MCL-1), tumor necrosis factor receptor superfamily, member 1A (TNFRSF1A), TNFRSF1A-associated death domain protein (TRADD).

Results

We demonstrated that a novel combination of ATRA and zoledronic acid is a strong inducer of apoptotic related cell death in both ovarian cancer cells. While the combination therapy significantly induced proapoptotic genes such as tumor necrosis factor receptor superfamily (TNFRSF), TRADD and caspase 4, some of the antiapoptotic genes such as members of MCL-1, LTBR, BAG3 and Bcl-2 family members were inhibited.

Conclusions

These are the preliminary molecular results of a novel combination treatment of ATRA and zoledronic acid, with fewer side effects as compared to conventional cytotoxic agents. With additional experimental analysis, it may serve as a good option for the treatment of refractory and elderly ovarian cancer patients, for whom there exists very limited choice of treatment.

The unexpected role of lymphotoxin beta receptor signaling in carcinogenesis: from lymphoid tissue formation to liver and prostate cancer development

The cytokines lymphotoxin (LT) alpha, beta and their receptor (LTbetaR) belong to the tumor necrosis factor (TNF) superfamily, whose founder-TNFalpha-was initially discovered due to its tumor necrotizing activity. LTbetaR signaling serves pleiotropic functions including the control of lymphoid organ development, support of efficient immune responses against pathogens due to maintenance of intact lymphoid structures, induction of tertiary lymphoid organs, liver regeneration or control of lipid homeostasis. Signaling through LTbetaR comprises the noncanonical/canonical nuclear factor-kappaB (NF-kappaB) pathways thus inducing chemokine, cytokine or adhesion molecule expression, cell proliferation and cell survival. Blocking LTbetaR signaling or Fcgamma-receptor mediated immunoablation of LT-expressing cells was demonstrated to be beneficial in various infectious or noninfectious inflammatory or autoimmune disorders. Only recently, LTbetaR signaling was shown to initiate inflammation-induced carcinogenesis, to influence primary tumorigenesis and to control reemergence of carcinoma in various cancer models through distinct mechanisms. Indeed, LTbetaR signaling inhibition has already been used as efficient anti-inflammatory, anti-cancer therapy in some experimental models. Here, we review the pleiotropic functions attributed to LT, the effects of its deregulation and extensively discuss the recent literature on LT's link to carcinogenesis.

Tumor necrosis factor, lymphotoxin and cancer

Initially TNF has been discovered as an anti-tumor factor, but it is now considered as one of the universal effectors of innate signaling implicating its key role in host defense and inflammation. Other physiological functions of TNF are primarily linked to organization of lymphoid tissues. TNF can exert deleterious effects on the organism when its local or systemic concentrations exceed certain levels. This is the main reason for the failure of TNF therapy in oncology. Moreover, in certain experimental models TNF to TNFRp55 signaling axis was found to play a pro-tumorigenic role. On the other hand, anti-TNF therapy proved to be beneficial in rheumatic and other autoimmune diseases. Taking into consideration the pivotal function of TNF in the immune system, it is obvious that such therapy cannot be entirely free of adverse effects including suppression of host defense and, possibly, predisposition to lymphomas. Lymphotoxins alpha and beta are the two related cytokines that exist in distinct trimeric forms which can signal through TNFR I and TNFR II, as well LTbetaR receptors, depending on the composition of the trimer. These signals have important functions in the development and homeostasis of the immune system. Importantly, there is a recently uncovered link between the LTalpha/LTbeta to LTbetaR signaling axis and cancer. Here we review the current status of the field with the focus on one particular issue: are TNF and lymphotoxins intrinsically anti-cancer or pro-tumorigenic.

Creation of a LIGHT mutant with the capacity to evade the decoy receptor for cancer therapy

The cytokine LIGHT activates various anti-tumor functions through its two receptors, lymphotoxin beta receptor (LTbetaR) and herpes virus entry mediator (HVEM), and is expected to be a promising candidate for cancer therapy. However, LIGHT is also trapped by decoy receptor 3 (DcR3), which is highly expressed in various tumors. Here, we used phage display technique to create LIGHT mutants that specifically bind LTbetaR and HVEM, and is not trapped by DcR3 for optimized cancer therapy. We constructed phage library displaying structural variants of LIGHT with randomized amino acid residues. After the affinity panning, we created 6 clones of LIGHT mutants as candidates for DcR3-evading LIGHT. Analysis of binding affinities showed that all candidates had 10-fold lower affinities for DcR3 than wild-type LIGHT, while 5 of the 6 clones had almost the same affinity for LTbetaR and HVEM. Furthermore, analysis of detailed binding kinetics showed that lower affinity for DcR3 is dependent on their faster off-rate. Further, we showed that the LIGHT mutant had almost the same cytotoxicity via LTbetaR, and had 62-fold higher DcR3-evading capacity compared to the wild type. Our data provide valuable information for construction of more functional LIGHT mutants that might be powerful tools for cancer therapy.

Comparison of the anti-tumor activity of native, secreted, and membrane-bound LIGHT in mouse tumor models

The TNF superfamily member LIGHT has potent anti-tumor activity through direct cytotoxicity and activation of the immune response, and is a promising candidate for cancer therapy. Natively, LIGHT exists as both a membrane-anchored form and a proteolytically processed, secreted form. However, the strength of the anti-tumor activity of each form of LIGHT has not been well defined. Here, to identify the optimal form of LIGHT for cancer gene therapy, we constructed fiber-mutant adenovirus vectors (AdRGD) encoding native full-length LIGHT (LIGHT/FL), stably membrane-anchored LIGHT (LIGHT/mem), and fully secreted LIGHT (LIGHT/sec). We then compared the anti-tumor effects of the different forms of LIGHT in mice by intratumoral injection of each AdRGD. We demonstrated that intratumoral injection of AdRGD-LIGHT/sec provided greater tumor suppression than AdRGD-LIGHT/FL, although this effect did not reach statistical significance. By comparison, AdRGD-LIGHT/mem had negligible anti-tumor activity. We also demonstrated that more CD4+ and CD8+ T cells accumulated inside tumors treated in vivo with AdRGD-LIGHT/sec than in tumors treated with AdRGD-LIGHT/FL or AdRGD-LIGHT/mem. These results suggest that the secreted form of LIGHT might be the optimal form for cancer gene therapy.

LIGHT protein suppresses tumor growth by augmentation of immune response

The tumor necrosis factor (TNF) superfamily member LIGHT has potent anti-tumor activities through activation of the immune response, and it is a promising candidate for use in cancer immunotherapy. However, there are no reports of the anti-tumor effects of LIGHT protein in vivo because of the lack of easy, efficient methods of manufacturing this protein. Here, we developed a method of manufacturing recombinant LIGHT protein using Escherichia coli through refolding of inclusion bodies; we then evaluated the anti-tumor activity of the protein. LIGHT protein expressed in E. coli showed the same biological activities and binding affinities to its receptors as did LIGHT expressed in mammalian cells. In addition, intratumoral injection of LIGHT significantly suppressed tumor growth, with augmentation of antigen-specific IFN-gamma-producing cells in the regional lymph nodes and spleen. These results indicate that LIGHT protein efficiently evokes the systemic tumor-specific immune response, and thus induces tumor suppression.

Anti-tumor activity of stability-engineered IgG-like bispecific antibodies targeting TRAIL-R2 and LTbetaR

Bispecific antibodies (BsAbs) represent an emerging class of biologics that achieve dual targeting with a single agent. Recombinant DNA technologies have facilitated a variety of creative bispecific designs with many promising therapeutic applications; however, practical methods for producing high quality BsAbs that have good product stability, long serum half-life, straightforward purification, and scalable production have largely been limiting. Here we describe a protein-engineering approach for producing stable, scalable tetravalent IgG-like BsAbs. The stability-engineered IgG-like BsAb was envisioned to target and crosslink two TNF family member receptors, TRAIL-R2 (TNF-Related Apoptosis Inducing Ligand Receptor-2) and LTbetaR (Lymphotoxin-beta Receptor), expressed on the surface of epithelial tumor cells with the goal of triggering an enhanced anti-tumor effect. Our IgG-like BsAbs consists of a stability-engineered anti-LTbetaR single chain Fv (scFv) genetically fused to either the N- or C-terminus of the heavy chain of a fulllength anti-TRAIL-R2 IgG1 monoclonal antibody. Both N- or C-terminal BsAbs were active in inhibiting tumor cell growth in vitro, and with some cell lines demonstrated enhanced activity relative to the combination of parental Abs. Pharmacokinetic studies in mice revealed long serum half-lives for the BsAbs. In murine tumor xenograft models, therapeutic treatment with the BsAbs resulted in reduction in tumor volume either comparable to or greater than the combination of parental antibodies, indicating that simultaneously targeting and cross-linking receptor pairs is an effective strategy for treating tumor cells. These studies support that stability-engineering is an enabling step for producing scalable IgG-like BsAbs with properties desirable for biopharmaceutical development.

Therapeutic targeting of TWEAK/Fnl4 in cancer: exploiting the intrinsic tumor cell killing capacity of the pathway

TNF-like weak inducer of apoptosis (TWEAK) and FGF-inducible molecule 14 (Fn14) are a TNF superfamily ligand-receptor pair. Initially identified as an inducer of tumor cell killing, TWEAK has pleiotropic effects, mediating proinflammatory and pro-angiogenic activity as well as stimulation of invasion, migration, and survival through its widely recognized receptor, Fn14. Fn14 is expressed at relatively low levels in normal tissues, but is dramatically elevated locally in injured and diseased tissues, where it plays a role in tissue remodeling. Herein we review the link between the TWEAK/Fn14 pathway and cancer as well as discuss potential therapeutic strategies targeting this pathway for cancer treatment. Many of the activities associated with the TWEAK/Fn14 pathway are linked with tumorigenesis and could thereby provide a growth advantage to tumors, suggesting that inhibition of the pathway may be beneficial in the treatment of cancer. At the same time, the elevated expression of Fn14 by tumor cells as well as the intrinsic tumor cell killing capacity of this receptor represents a promising alternative of harnessing the intrinsic tumor cell killing capacity of Fn14 to treat cancer.

Differential RelA- and RelB-dependent gene transcription in LTbetaR-stimulated mouse embryonic fibroblasts

BACKGROUND

Lymphotoxin signaling via the lymphotoxin-beta receptor (LTbetaR) has been implicated in biological processes ranging from development of secondary lymphoid organs, maintenance of spleen architecture, host defense against pathogens, autoimmunity, and lipid homeostasis. The major transcription factor that is activated by LTbetaR crosslinking is NF-kappaB. Two signaling pathways have been described, the classical inhibitor of NF-kappaB alpha (IkappaBalpha)-regulated and the alternative p100-regulated pathway that result in the activation of p50-RelA and p52-RelB NF-kappaB heterodimers, respectively.

RESULTS

Using microarray analysis, we investigated the transcriptional response downstream of the LTbetaR in mouse embryonic fibroblasts (MEFs) and its regulation by the RelA and RelB subunits of NF-kappaB. We describe novel LTbetaR-responsive genes that were regulated by RelA and/or RelB. The majority of LTbetaR-regulated genes required the presence of both RelA and RelB, revealing significant crosstalk between the two NF-kappaB activation pathways. Gene Ontology (GO) analysis confirmed that LTbetaR-NF-kappaB target genes are predominantly involved in the regulation of immune responses. However, other biological processes, such as apoptosis/cell death, cell cycle, angiogenesis, and taxis were also regulated by LTbetaR signaling. Moreover, LTbetaR activation inhibited expression of a key adipogenic transcription factor, peroxisome proliferator activated receptor-gamma (pparg), suggesting that LTbetaR signaling may interfere with adipogenic differentiation.

CONCLUSION

Microarray analysis of LTbetaR-stimulated fibroblasts provided comprehensive insight into the transcriptional response of LTbetaR signaling and its regulation by the NF-kappaB family members RelA and RelB.

Stroma-dependent apoptosis in clonal hematopoietic precursors correlates with expression of PYCARD

The role of the marrow microenvironment in the pathophysiology of myelodysplastic syndromes (MDSs) remains controversial. Using stromal/hematopoietic cell cocultures, we investigated the effects of stroma-derived signals on apoptosis sensitivity in hematopoietic precursors. The leukemia-derived cell line KG1a is resistant to proapoptotic ligands. However, when cocultured with the human stromal cell line HS5 (derived from normal marrow) and exposed to tumor necrosis factor-alpha (TNF-alpha), KG1a cells showed caspase-3 activation and induction of apoptosis. Apoptosis was contact dependent. Identical results were obtained in coculture with primary stroma. Gene-expression profiling of KG1a cells identified coculture-induced up-regulation of various genes involved in apoptosis, including PYCARD. Suppression of PYCARD expression in KG1a by miRNA interfered with apoptosis. Knockdown of the TNF receptor 1 (TNFR1) or TNFR2 in HS5 cells had no effect. However, knockdown of R1 in KG1a cells prevented TNF-alpha-induced apoptosis, while apoptosis was still induced by TNF-alpha-related apoptosis-inducing ligand. Primary CD34(+) cells from MDS marrow, when cocultured with HS5 and TNF-alpha, also underwent apoptosis. In contrast, no apoptosis was observed in CD34(+) cells from the marrow of healthy donors. These data indicate that stroma may convey not only protective effects on hematopoietic cells, but, dependent upon the milieu, may also facilitate apoptosis.

Enhancement of docetaxel-induced cytotoxicity and apoptosis by all-trans retinoic acid (ATRA) through downregulation of survivin (BIRC5), MCL-1 and LTbeta-R in hormone- and drug resistant prostate cancer cell line, DU-145

Background

The management of hormone-refractory prostate cancer (HRPC) still remains as an important challenge of daily oncology practice. Docetaxel has proved to be a first line treatment choice. All-trans retinoic acid (ATRA) could potently inhibit the growth of prostate cancer cells in vitro and its combination with various anticancer agents results in increased cytotoxicity. Based on these data, our aim was to examine the synergistic/additive cytotoxic and apoptotic effects of combination of docetaxel and ATRA, in hormone- and drug refractory human DU-145 prostate cancer cells. Furthermore, we have searched for the underlying mechanisms of apoptosis by demonstrating apoptosis-related genes.

Methods

XTT cell proliferation assay was used for showing cytotoxicity. For verifying apoptosis, both DNA Fragmentation by ELISA assay and caspase 3/7 activity measurement were used. For detecting the mechanism of apoptosis induced by docetaxel-ATRA combination, OligoGeArray^® which consists of 112 apoptosis related genes was used.

Results

Our results revealed that docetaxel and ATRA were synergistically cytotoxic and apoptotic in DU-145 cells, in a dose- and time dependent manner. It was also shown by our studies that apoptosis was induced in DU-145 prostate carcinoma cells with significant cytotoxicity, no matter which agent applied first. We have found out that docetaxel-ATRA combination significantly downregulates survivin (BIRC5), myeloid cell leukemia-1 (MCL-1) and lymphotoxin β-receptor (LTβR) genes, which all three have pivotal roles in regulation of apoptosis and cell cycle progression.

Conclusion

In conclusion, we strongly suggest that docetaxel and ATRA combination is a good candidate for this challenging era of daily oncologic practice. Also, the combination of docetaxel and ATRA might allow a reduction in docetaxel doses and by this way may diminish docetaxel adverse effects while maintaining the therapeutic effect in patients with HRPC.

The lymphotoxin-beta receptor is an upstream activator of NF-kappaB-mediated transcription in melanoma cells

The pleiotropic transcription factor nuclear factor-kappaB (NF-kappaB (p50/p65)) regulates the transcription of genes involved in the modulation of cell proliferation, apoptosis, and oncogenesis. Furthermore, a host of solid and hematopoietic tumor types exhibit constitutive activation of NF-kappaB (Basseres, D. S., and Baldwin, A. S. (2006) 25, 6817-6830). However, the mechanism for this constitutive activation of NF-kappaB has not been elucidated in the tumors. We have previously shown that NF-kappaB-inducing kinase (NIK) protein and its association with Inhibitor of kappaB kinase alphabeta are elevated in melanoma cells compared with their normal counterpart, leading to constitutive activation of NF-kappaB. Moreover, expression of dominant negative NIK blocked this base-line NF-kappaB activity in melanoma cells. Of the three receptors that require NIK for activation of NF-kappaB, only the lymphotoxin-beta receptor (LTbeta-R) is expressed in melanoma. We show in this manuscript that for melanoma there is a strong relationship between expression of the LTbeta-R and constitutive NF-kappaB transcriptional activity. Moreover, we show that activation of the LTbeta-R can drive NF-kappaB activity to regulate gene expression that leads to enhanced cell growth. The inhibition by LTbeta-R shRNA resulted in decreased NF-kappaB promoter activity, decreased growth, and decreased invasiveness as compared with control. These results indicate that the LTbeta-R constitutively induces NF-kappaB activation, and this event may be associated with autonomous growth of melanoma cells.

Ectopic lymphoid tissues and local immunity

Ectopic or tertiary lymphoid tissues develop at sites of inflammation or infection in peripheral, non-lymphoid organs. These tissues are architecturally similar to conventional secondary lymphoid organs, with separated B and T cell areas, specialized populations of dendritic cells, well-differentiated stromal cells and high endothelial venules. Ectopic lymphoid tissues are often associated with the local pathology that results from chronic infection or chronic inflammation. However, there are also examples in which ectopic lymphoid tissues appear to contribute to local protective immune responses. Here we review how ectopic lymphoid structures develop and function in the context of local immunity and pathology.

TWEAKing tissue remodeling by a multifunctional cytokine: role of TWEAK/Fn14 pathway in health and disease

First described as a weak apoptosis inducer, the TNF superfamily ligand TWEAK has since emerged as a cytokine that regulates multiple cellular responses, including proinflammatory activity, angiogenesis and cell proliferation, suggesting roles in inflammation and cancer. More recently TWEAK's ability to regulate progenitor cell fate was elucidated. Experiments using genetic overexpression and pathway inhibition or deficiency in mice indicate that TWEAK coordinates inflammatory and progenitor cell responses in settings of acute injury through its highly inducible receptor, FGF-inducible molecule 14 (Fn14), establishing the pathway's physiological role in facilitating acute tissue repair. In contrast, in chronic inflammatory disease models characterized by persistent TWEAK/Fn14 activation, TWEAK functions as a novel pathogenic mediator by amplifying inflammation, promoting tissue damage and potentially impeding endogenous repair mechanisms. Herein we aim not only to review the multifaceted functions of this emerging pathway, but also propose a conceptual framework for TWEAK/Fn14 pathway function in health and disease, supported by studies employing TWEAK and Fn14 deficient mice and anti-TWEAK blocking mAbs in acute injury and inflammatory disease settings. In addition to a perspective of the biology, we discuss potential therapeutic strategies targeting this pathway for the treatment of tissue injury, chronic inflammatory diseases and cancer.

Targeting lymphotoxin beta receptor with tumor-specific T lymphocytes for tumor regression

PURPOSE

One of the impediments of immunotherapy against cancer is the suppression of tumor-specific CTLs in the tumor microenvironment, partly due to the selective inhibition of the perforin pathway and the emergence of Fas-resistant tumors. Therefore, we sought to identify perforin- and Fas-independent cytotoxic pathways and explored the potential of targeting LTbetaR with tumor-specific CTLs to induce tumor rejection in vivo.

EXPERIMENTAL DESIGN

Fas-resistant tumors were examined for their susceptibility to perforin-deficient (pfp) CTLs via CTL adoptive transfer in mouse models of experimental lung metastasis. The specificity of LTbetaR, a cell surface death receptor, in causing tumor rejection by CTLs was analyzed by LTbetaR-specific neutralizing monoclonal antibody in vitro. The specificity and efficacy of LTbetaR in the suppression of established tumors was further investigated by silencing LTbetaR in tumor cells in vivo.

RESULTS

pfp CTLs exhibited significant cytotoxicity against Fas-resistant tumors in vivo. The perforin- and Fas-independent cytotoxicity was directly mediated, at least in part, by the adoptively transferred CTLs. It was observed that LTbetaR was expressed on the tumor cell surface, and LTalpha, LTbeta, and LIGHT, all of which are ligands for LTbetaR, were either constitutively expressed or activated in the tumor-specific CTLs and primary CD8(+) T cells. Blocking LTbetaR with LTbetaR-specific neutralizing monoclonal antibody decreased CTL cytotoxicity in vitro. Silencing LTbetaR using LTbetaR-specific short hairpin RNA reduced the ability of pfp CTLs to induce tumor rejection in vivo.

CONCLUSION

LTbetaR directly mediates CTL-directed tumor rejection in vivo. Targeting LTbetaR with tumor-specific CTLs is a potential therapeutic approach.

Molecular Profiling of Matched Samples Identifies Biomarkers of Papillary Thyroid Carcinoma Lymph Node Metastasis

Biomarkers of papillary thyroid carcinoma (PTC) metastasis can accurately identify metastatic cells and aggressive tumor behavior. To find new markers, serial analysis of gene expression (SAGE) was done on three samples from the same patient: normal thyroid tissue, primary PTC, and a PTC lymph node metastasis. This genomewide expression analysis identified 31 genes expressed in lymph node metastasis, but not in the primary tumor. Eleven genes were evaluated by quantitative real-time reverse transcription-PCR (qPCR) on independent sets of matched samples to find genes that were consistently different between the tumor and metastatic samples. LIMD2 and PTPRC (CD45) showed a statistically significant difference in expression between tumor and metastatic samples (P < 0.0045), and an additional gene (LTB) had borderline significance. PTPRC and LTB were tested by immunohistochemistry in an independent set of paired samples, with both markers showing a difference in protein expression. All 20 metastases from 6 patients showed expression in both markers, with little or no expression in primary tumor. Some of these markers could provide an improved means to detect metastatic PTC cells during initial staging of a newly diagnosed carcinoma and/or to rule out recurrence. The functional role of these genes may also provide insight into mechanisms of thyroid cancer metastasis.