STAT1 modulates tissue wasting or overgrowth downstream from PDGFRß.

Platelet-derived growth factor (PDGF) acts through two conserved receptor tyrosine kinases: PDGFRα and PDGFRß. Gain-of-function mutations in human PDGFRB have been linked recently to genetic diseases characterized by connective tissue wasting (Penttinen syndrome) or overgrowth (Kosaki overgrowth syndrome), but it is unclear whether PDGFRB mutations alone are responsible. Mice with constitutive PDGFRß signaling caused by a kinase domain mutation (D849V) develop lethal autoinflammation. Here we used a genetic approach to investigate the mechanism of autoinflammation in Pdgfrb+/D849V mice and test the hypothesis that signal transducer and activator of transcription 1 (STAT1) mediates this phenotype. We show that Pdgfrb+/D849V mice with Stat1 knockout (Stat1-/-Pdgfrb+/D849V ) are rescued from autoinflammation and have improved life span compared with Stat1+/-Pdgfrb+/D849V mice. Furthermore, PDGFRß-STAT1 signaling suppresses PDGFRß itself. Thus, Stat1-/-Pdgfrb+/D849V fibroblasts exhibit increased PDGFRß signaling, and mice develop progressive overgrowth, a distinct phenotype from the wasting seen in Stat1+/-Pdgfrb+/D849V mice. Deletion of interferon receptors (Ifnar1 or Ifngr1) does not rescue wasting in Pdgfrb+/D849V mice, indicating that interferons are not required for autoinflammation. These results provide functional evidence that elevated PDGFRß signaling causes tissue wasting or overgrowth reminiscent of human genetic syndromes and that the STAT1 pathway is a crucial modulator of this phenotypic spectrum.

PKC inhibition of sotrastaurin has antitumor activity in diffuse large B-cell lymphoma via regulating the expression of MCT-1.

MCT-1 (multiple copies in T-cell lymphoma-1), a novel oncogene, was originally identified in T-cell lymphoma. A recent study has demonstrated that MCT-1 is highly expressed in 85% of diffuse large B-cell lymphomas (DLBCL). PKC (protein kinase C) plays an essential role in signal transduction for multiple biologically active substances for activating cellular functions and proliferation. In this study, we found that the mRNA and protein expression levels of MCT-1 were visibly decreased after knocking down PKC by siRNA in SUDHL-4 and OCI-LY8 DLBCL cell lines. A selective PKC inhibitor, sotrastaurin, effectively inhibited cell proliferation and induced cell apoptosis in a dose- and time-dependent manner. Meanwhile, we also observed that the cell cycle was arrested in the G1 phase in sotrastaurin-treated cells. In addition, MCT-1 was down-regulated in the sotrastaurin treatment group in vivo. Furthermore, we demonstrated that the PKC inhibitor sotrastaurin induced cell apoptosis and cell cycle arrest in DLBCL cells potentially through regulating the expression of MCT-1. Our data suggest that targeting PKC may be a potential therapeutic approach for lymphomas and related malignancies that exhibit high levels of MCT-1 protein.

Dihydrocelastrol inhibits multiple myeloma cell proliferation and promotes apoptosis through ERK1/2 and IL-6/STAT3 pathways in vitro and in vivo.

Multiple myeloma (MM) is the second most frequent malignant hematological disease. Dihydrocelastrol (DHCE) is synthesized by hydrogenated celastrol, a treterpene isolated from Chinese medicinal plant Tripterygium regelii. In this study, we first reported the anti-tumor activity of DHCE on MM cells. We found that DHCE could inhibit cell proliferation and promote apoptosis through caspase-dependent way in vitro. In addition, DHCE could inactivate the expression of interleukin (IL)-6 and downregulate the phosphorylation of extracellular regulated protein kinases (ERK1/2) and the signal transducer and activator of transcription 3 (STAT3) in MM. It also retained its activity against MM cell lines in the presence of IL-6. Furthermore, treatment of MM cells with DHCE resulted in an accumulation of cells in G0/G1 phase of the cell cycle. Notably, DHCE reduced the expression of cyclin D1 and cyclin-dependent kinases 4 and 6 in MM cell lines. Additionally, its efficacy toward the MM cell lines could be enhanced in combination with the histone deacetylase inhibitor panobinostat (LBH589), which implied the possibility of the combination treatment of DHCE and LBH589 as a potential therapeutic strategy in MM. In addition, treatment of NCI-H929 tumor-bearing nude mice with DHCE (10 mg/kg/d, i.p., 1-14 days) resulted in 73% inhibition of the tumor growth in vivo. Taken together, the results of our present study indicated that DHCE could inhibit cellular proliferation and induce cell apoptosis in myeloma cells mediated through different mechanisms, possibly through inhibiting the IL-6/STAT3 and ERK1/2 pathways. And it may provide a new therapeutic option for MM patients.

Down-regulation of eIF4GII by miR-520c-3p represses diffuse large B cell lymphoma development.

Deregulation of the translational machinery is emerging as a critical contributor to cancer development. The contribution of microRNAs in translational gene control has been established however; the role of microRNAs in disrupting the cap-dependent translation regulation complex has not been previously described. Here, we established that elevated miR-520c-3p represses global translation, cell proliferation and initiates premature senescence in HeLa and DLBCL cells. Moreover, we demonstrate that miR-520c-3p directly targets translation initiation factor, eIF4GII mRNA and negatively regulates eIF4GII protein synthesis. miR-520c-3p overexpression diminishes cells colony formation and reduces tumor growth in a human xenograft mouse model. Consequently, downregulation of eIF4GII by siRNA decreases translation, cell proliferation and ability to form colonies, as well as induces cellular senescence. In vitro and in vivo findings were further validated in patient samples; DLBCL primary cells demonstrated low miR-520c-3p levels with reciprocally up-regulated eIF4GII protein expression. Our results provide evidence that the tumor suppressor effect of miR-520c-3p is mediated through repression of translation while inducing senescence and that eIF4GII is a key effector of this anti-tumor activity.

Inhibiting CARD11 translation during BCR activation by targeting the eIF4A RNA helicase.

Human diffuse large B-cell lymphomas (DLBCLs) often aberrantly express oncogenes that generally contain complex secondary structures in their 5' untranslated region (UTR). Oncogenes with complex 5'UTRs require enhanced eIF4A RNA helicase activity for translation. PDCD4 inhibits eIF4A, and PDCD4 knockout mice have a high penetrance for B-cell lymphomas. Here, we show that on B-cell receptor (BCR)-mediated p70s6K activation, PDCD4 is degraded, and eIF4A activity is greatly enhanced. We identified a subset of genes involved in BCR signaling, including CARD11, BCL10, and MALT1, that have complex 5'UTRs and encode proteins with short half-lives. Expression of these known oncogenic proteins is enhanced on BCR activation and is attenuated by the eIF4A inhibitor Silvestrol. Antigen-experienced immunoglobulin (Ig)G(+) splenic B cells, from which most DLBCLs are derived, have higher levels of eIF4A cap-binding activity and protein translation than IgM(+) B cells. Our results suggest that eIF4A-mediated enhancement of oncogene translation may be a critical component for lymphoma progression, and specific targeting of eIF4A may be an attractive therapeutic approach in the management of human B-cell lymphomas.

Thalidomide treatment for patients with previously untreated multiple myeloma: a meta-analysis of randomized controlled trials.

The efficacy and safety of thalidomide as an initial treatment in myeloma patients who were unsuitable for autologous stem cell transplantation (ASCT), as induction treatment prior to ASCT, or as a maintenance treatment was unclear. The purpose of this study was to assess the benefits and risks of thalidomide for previously untreated myeloma patients. MEDLINE, EMBASE, and Cochrane Library were searched for randomized controlled trials (RCTs) of thalidomide used in either induction or maintenance therapy for previously untreated myeloma patients. Twenty-two RCTs enrolling 9098 patients were identified, including 15 RCTs of induction thalidomide, 6 RCTs of maintenance thalidomide, and 1 RCT of induction and maintenance thalidomide. Induction thalidomide improved overall response rate (ORR) (risk ratio (RR) 1.54, 95 % confidence interval (CI) 1.30-1.83), complete response rate (CRR) (RR 3.03, 95 % CI 1.91-4.80), progression-free survival (PFS) (hazard ratio (HR) 0.65, 95 % CI 0.56-0.76), and overall survival (OS) (HR 0.78, 95 % CI 0.67-0.91) in patients who were not allowed to receive ASCT. Induction thalidomide improved pre-ASCT ORR (RR 1.20, 95 % CI 1.11-1.30), pre-ASCT and post-ASCT CRR (RR 1.47, 95 % CI 1.12-1.93 and RR 1.23, 95 % CI 1.00-1.50, respectively), and PFS (HR 0.73, 95 % CI 0.59-0.91) in patients who were allowed to receive ASCT, but it did not improve post-ASCT ORR (RR 1.04, 95 % CI 0.99-1.09) and OS (HR 0.91, 95 % CI 0.79-1.05). Improved PFS and prolonged OS were observed (HR 0.61, 95 % CI 0.53-0.70 and HR 0.77, 95 % CI 0.62-0.95, respectively) when thalidomide was added to maintenance therapy. More patients experienced venous thromboembolism (VTE) of grade 3/4 when thalidomide was added to induction or maintenance therapy (HR 2.15, 95 % CI 1.58-2.92 and RR 1.96, 95 % CI 1.13-3.40, respectively). Induction thalidomide still increased the risk of VTE (RR 1.53, 95 % CI 1.12-2.08) after VTE prophylaxis was used. Induction thalidomide effectively improved CRR, ORR, and PFS (except post-ASCT ORR). Notably, induction thalidomide improved OS in patients who were not allowed to receive ASCT but not in patients who were allowed to receive ASCT. The addition of thalidomide to maintenance therapy improved both PFS and OS. However, thalidomide led to a greater risk of VTE with grade 3/4. This risk did not disappear after VTE prophylaxis was used in induction therapy with thalidomide.

Pterostilbene Inhibits Human Multiple Myeloma Cells via ERK1/2 and JNK Pathway In Vitro and In Vivo.

Multiple myeloma (MM) is the second most common malignancy in the hematologic system, which is characterized by accumulation of plasma cells in bone marrow. Pterostilbene (PTE) is a natural dimethylated analog of resveratrol, which has anti-oxidant, anti-inflammatory and anti-tumor properties. In the present study, we examined the anti-tumor effect of PTE on MM cell lines both in vitro and in vivo using the cell counting kit (CCK)-8, apoptosis assays, cell cycle analysis, reactive oxygen species (ROS) generation, JC-1 mitochondrial membrane potential assay, Western blotting and tumor xenograft models. The results demonstrated that PTE induces apoptosis in the H929 cell line and causes cell cycle arrest at G0/G1 phase by enhancing ROS generation and reducing mitochondrial membrane potential. The anti-tumor effect of PTE may be caused by the activation of the extracellular regulated protein kinases (ERK) 1/2 and c-Jun N-terminal kinase (JNK) signaling pathways. Additionally, mice treated with PTE by intraperitoneal injection demonstrated reduced tumor volume. Taken together, the results of this study indicate that the anti-tumor effect of PTE on MM cells may provide a new therapeutic option for MM patients.

Distinct inhibitory effects on mTOR signaling by ethanol and INK128 in diffuse large B-cell lymphoma.

BACKGROUND: The mechanistic target of rapamycin, (mTOR) kinase plays a pivotal role in controlling critical cellular growth and survival pathways, and its aberrant induction is implicated in cancer pathogenesis. Therefore, suppression of active mTOR signaling has been of great interest to researchers; several mTOR inhibitors have been discovered to date. Ethanol (EtOH), similar to pharmacologic mTOR inhibitors, has been shown to suppress the mTOR signaling pathway, though in a non-catalytic manner. Despite population studies showing that the consumption of EtOH has a protective effect against hematological malignancies, the mechanisms behind EtOH's modulation of mTOR activity in cells and its downstream consequences are largely unknown. Here we evaluated the effects of EtOH on the mTOR pathway, in comparison to the active-site mTOR inhibitor INK128, and compared translatome analysis of their downstream effects in diffuse large B-cell lymphoma (DLBCL). RESULTS: Treatment of DLBCL cells with EtOH suppressed mTORC1 complex formation while increasing AKT phosphorylation and mTORC2 complex assembly. INK128 completely abrogated AKT phosphorylation without affecting the structure of mTORC1/2 complexes. Accordingly, EtOH less profoundly suppressed cap-dependent translation and global protein synthesis, compared to a remarkable inhibitory effect of INK128 treatment. Importantly, EtOH treatment induced the formation of stress granules, while INK128 suppressed their formation. Microarray analysis of polysomal RNA revealed that although both agents primarily affected cell growth and survival, EtOH and INK128 regulated the synthesis of mostly distinct genes involved in these processes. Though both EtOH and INK128 inhibited cell cycle, proliferation and autophagy, EtOH, in contrast to INK128, did not induce cell apoptosis. CONCLUSION: Given that EtOH, similar to pharmacologic mTOR inhibitors, inhibits mTOR signaling, we systematically explored the effect of EtOH and INK128 on mTOR signal transduction, components of the mTORC1/2 interaction and their downstream effectors in DLBCL malignancy. We found that EtOH partially inhibits mTOR signaling and protein translation, compared to INK128's complete mTOR inhibition. Translatome analysis of mTOR downstream target genes established that differential inhibition of mTOR by EtOH and INK128 distinctly modulates translation of specific subsets of mRNAs involved in cell growth and survival, leading to differential cellular response and survival.

Antitumor activity of fucoidan against diffuse large B cell lymphoma in vitro and in vivo.

Fucoidan is one of the major sulfated polysaccharides isolated from brown seaweeds. In this study, we determined the anti-cancer activity of fucoidan on diffuse large B cell lymphoma (DLBCL) cells both in vitro and in vivo. Fucoidan inhibited the growth of DLBCL cells in a dose- and time-dependent manner, and fucoidan treatment provoked G0/G1 cell cycle arrest, which was accompanied by p21 up-regulation and cyclin D1, Cdk4, and Cdk6 down-regulation. Fucoidan also induced caspase-dependent cell apoptosis in DLBCL cell lines and primary DLBCL cell. In addition, fucoidan treatment caused the loss of mitochondrial membrane potential and the release of cytochrome c and apoptosis-inducing factor from the mitochondria into the cytosol. Fucoidan also potentiated the activities of carfilzomib in killing DLBCL cells. Oral administration of fucoidan effectively inhibited tumor growth in xenograft mouse models. Our findings reveal the novel function of fucoidan as an anti-DLBCL agent, which can be used in the clinical treatment of DLBCL.

Regulation of androgen receptor activity by tyrosine phosphorylation.

The androgen receptor (AR) is essential for the growth of prostate cancer cells. Here, we report that tyrosine phosphorylation of AR is induced by growth factors and elevated in hormone-refractory prostate tumors. Mutation of the major tyrosine phosphorylation site in AR significantly inhibits the growth of prostate cancer cells under androgen-depleted conditions. The Src tyrosine kinase appears to be responsible for phosphorylating AR, and there is a positive correlation of AR tyrosine phosphorylation with Src tyrosine kinase activity in human prostate tumors. Our data collectively suggest that growth factors and their downstream tyrosine kinases, which are elevated during hormone-ablation therapy, can induce tyrosine phosphorylation of AR and such modification may be important for prostate tumor growth under androgen-depleted conditions.

The novel anti-MEK small molecule AZD6244 induces BIM-dependent and AKT-independent apoptosis in diffuse large B-cell lymphoma.

The RAS/RAF/MEK/ERK signaling pathway has been largely unexplored as a potential therapeutic target in lymphoma. The novel 2nd generation anti-MEK small molecule, AZD6244, down-regulated its direct downstream target, phospho-ERK (pERK) in germinal center and nongerminal center diffuse large B-cell lymphoma (DLBCL) cell lines and primary cells. Similar decreased pERK levels were noted despite constitutive activation (CA) of MEK. Consequently, several lymphoma-related ERK substrates were down-regulated by AZD6244 including MCT-1, c-Myc, Bcl-2, Mcl-1, and CDK1/2. AZD6244 induced time- and dose-dependent antiproliferation and apoptosis in all DLBCL cell lines and fresh/primary cells (IC(50) 100nM-300nM). Furthermore, AZD6244 resulted in significantly less tumor compared with control in an in vivo DLBCL SCID xenograft model. Cell death was associated with cleaved PARP, caspases-8, -9, and -3, and apoptosis was caspase-dependent. In addition, there was stabilization of FoxO3a, activation of BIM and PUMA, and a significant decrease in c-Myc transcripts. Moreover, siRNA knockdown of BIM abrogated AZD6244-related apoptosis, while shRNA knockdown of ERK minimally sensitized cells. Finally, manipulation of AKT with transfection of OCI-LY3 cells with CA-AKT or through chemical inhibition (LY294002) had minimal effect on AZD6244-induced cell death. Altogether, these findings show that the novel anti-MEK agent, AZD6244, induced apoptosis in DLBCL and that cell death was BIM-dependent.

ATM regulates a DNA damage response posttranscriptional RNA operon in lymphocytes.

Maintenance of genomic stability depends on the DNA damage response, a biologic barrier in early stages of cancer development. Failure of this response results in genomic instability and high predisposition toward lymphoma, as seen in patients with ataxia-telangiectasia mutated (ATM) dysfunction. ATM activates multiple cell-cycle checkpoints and DNA repair after DNA damage, but its influence on posttranscriptional gene expression has not been examined on a global level. We show that ionizing radiation modulates the dynamic association of the RNA-binding protein HuR with target mRNAs in an ATM-dependent manner, potentially coordinating the genotoxic response as an RNA operon. Pharmacologic ATM inhibition and use of ATM-null cells revealed a critical role for ATM in this process. Numerous mRNAs encoding cancer-related proteins were differentially associated with HuR depending on the functional state of ATM, in turn affecting expression of encoded proteins. The findings presented here reveal a previously unidentified role of ATM in controlling gene expression posttranscriptionally. Dysregulation of this DNA damage response RNA operon is probably relevant to lymphoma development in ataxia-telangiectasia persons. These novel RNA regulatory modules and genetic networks provide critical insight into the function of ATM in oncogenesis.

Alcohol consumption and decreased risk of non-Hodgkin lymphoma: role of mTOR dysfunction.

Several epidemiologic studies support the emerging paradigm that current alcohol consumers have decreased risk of most types of non-Hodgkin lymphoma. The observed lower risk among people who drank alcohol does not seem to vary with beverage type. The mechanisms accounting for alcohol-induced decrease in the incidence of lymphomas remain largely unknown. We demonstrate that low-dose chronic exposure to ethanol inhibits mammalian target of rapamycin (mTOR) C1 complex formation, resulting in decreased phosphorylation events involved in mTOR pathway signaling in a lymphoid-tissue specific manner. These changes in mTOR signaling lead to a decrease in eIF4E associated with the translation initiation complex and a repression of global cap-dependent synthesis in both lymphoma cell lines and normal donor lymphocytes. We show that chronic exposure of ethanol at physiologically relevant concentrations in a xenograft model results in a striking inhibition of lymphoma growth. Our data support a paradigm in which chronic ethanol exposure inhibits mTOR signaling in lymphocytes with a significant repression of cap-dependent translation, reducing the tumorigenic capacity of non-Hodgkin lymphoma in a human xenograft model. The ethanol-mediated repression of mTOR signaling coupled with decreased in vivo lymphoma growth underscore the critical role of mTOR signaling and translation in lymphoma.

Pterostilbene Induces Cell Apoptosis and Cell Cycle Arrest in T-Cell Leukemia/Lymphoma by Suppressing the ERK1/2 Pathway.

Pterostilbene is a natural 3,5-dimethoxy analog of trans-resveratrol that has been reported to have antitumor, antioxidant, and anti-inflammatory effects. T-cell leukemia/lymphoma is one of the more aggressive yet uncommon non-Hodgkin lymphomas. Although there has been increasing research into T-cell leukemia/lymphoma, the molecular mechanisms of the antitumor effects of pterostilbene against this malignancy are still largely unknown. The aim of this study is to confirm the effects of pterostilbene in T-cell leukemia/lymphoma. Jurkat and Hut-78 cells treated with pterostilbene were evaluated for cell proliferation using Cell Counting Kit-8, and apoptosis, cell cycle progression, reactive oxygen species generation, and mitochondrial membrane potential were analyzed using flow cytometry. The level of protein expression was detected by western blot. The results demonstrated that pterostilbene significantly inhibited the growth of T-cell leukemia/lymphoma cell lines in vitro and induced apoptosis in a dose- and time-dependent manner. Moreover, pterostilbene treatment markedly induced S-phase cell cycle arrest, which was accompanied by downregulation of cdc25A, cyclin A2, and CDK2. Pterostilbene also induced the generation of reactive oxygen species and the loss of mitochondrial membrane potential and inhibited ERK1/2 phosphorylation. Taken together, our study demonstrated the potential of pterostilbene to be an effective treatment for T-cell leukemia/lymphoma.

Preclinical activity of DCZ3301, a novel aryl-guanidino compound in the therapy of multiple myeloma.

We synthesized a novel aryl-guanidino compound, DCZ3301, and found that it has potent cytotoxicity against multiple human cancer cell lines. The anticancer activity was most potent against multiple myeloma (MM). DCZ3301 induced cytotoxicity in MM cell lines, as well as patient myeloma cells, in part by decreasing mitochondrial membrane potential to induce apoptosis. In contrast, DCZ3301 had no cytotoxic effect on normal cells. DCZ3301 also inhibited cell cycling and caused a G2/M accumulation that corresponded with downregulation of Cdc25C, CDK1, and Cyclin B1. DCZ3301 retained its activity against MM cells in the presence of exogenous cytokines (IL-6 or VEGF) or bone marrow stromal cells (BMSCs) and reduced activity of multiple signaling pathways (STAT3, NFκB, AKT, ERK1/2) in MM but not normal cells. The STAT3 pathway played an important role in modulating DCZ3301-mediated cytotoxicity. Knockdown of STAT3 using siRNA in MM cells enhanced DCZ3301-induced cytotoxicity, whereas overexpression of STAT3 in MM cells partially protected them from apoptosis. In addition, DCZ3301 inhibited VEGF and IL-6 secretion in a dose-dependent fashion in a co-culture of MM cells and BMSCs. Combining DCZ3301 with bortezomib induced synergistic cytotoxicity in MM cell lines and primary MM cells. Finally, in vivo efficacy of DCZ3301 was confirmed in an MM xenograft mouse model. Together, these results provide a rationale for translation of this small-molecule inhibitor, either alone or in combination, to the clinic against MM.

The blueberry component pterostilbene has potent anti-myeloma activity in bortezomib-resistant cells.

Multiple myeloma (MM) is an incurable hematologic malignancy because of its drug resistance. Pterostilbene (Pter) is found mainly in blueberries and grapes. The effects of Pter and its exact pharmacologic mechanisms on chemoresistant myeloma are not known. Herein, we investigated the anti-myeloma activity of Pter in bortezomib-resistant cell line H929R and explored the related mechanism of action for the first time. We found that Pter inhibited proliferation of H929R cells and promoted apoptosis of the cells through a caspase-dependent pathway, loss of mitochondrial membrane potential, and activation of Akt and p38 mitogen-activated protein kinase (MAPK) signaling pathways. DNA damage and S-phase arrest might be involved in Pter-related toxicity in H929R cells. Pter and the histone deacetylase inhibitors panobinostat or vorinostat inhibited proliferation of H929R cells in a synergistic manner. These data supported that Pter might be a promising natural compound for relapsed/refractory myeloma therapy, especially against myeloma resistant to bortezomib chemotherapy.

Therapeutic potential and functional interaction of carfilzomib and vorinostat in T-cell leukemia/lymphoma.

We previously showed that the proteasome inhibitor carfilzomib and the histone deacetylase inhibitor (HDACI) vorinostat cooperated to induce cell apoptosis in one T-cell leukemia cell line in vitro, implying the possibility of the combination treatment of carfilzomib and vorinostat as a potential therapeutic strategy in human T-cell leukemia/lymphoma. Here we report that combination treatment of carfilzomib and vorinostat enhanced cell apoptosis and induced a marked increase in G2-M arrest, reactive oxygen species (ROS) generation, and activated the members of mitogen-activated protein kinases (MAPK) family, including the stress-activated kinases JNK, p38MAPK, and ERK1/2. Carfilzomib/vorinostat-mediated apoptosis was blocked by the ROS scavenger N-acetylcysteine (NAC). The JNK inhibitor SP600125 and the p38MAPK inhibitor SB203580 but not the MEK1/2 inhibitor U0126 significantly attenuated carfilzomib/vorinostat-induced apoptosis, suggesting that p38MAPK and JNK activation contribute to carfilzomib and vorinostat-induced apoptosis. This was further confirmed via short hairpin (shRNA) RNA knockdown of p38MAPK and JNK. Interestingly, the ROS scavenger NAC attenuated carfilzomib/vorinostat-mediated activation of p38MAPK and JNK. However, p38MAPK shRNA but not JNK shRNA diminished carfilzomib/vorinostat-mediated ROS generation. In contrast, overexpression of p38MAPK significantly increased carfilzomib/vorinostat-mediated ROS generation, suggesting that an amplification loop exists between ROS and p38MAPK pathway. Combination treatment of carfilzomib and vorinostat enhanced their individual antitumor activity in both a human xenograft model as well as human primary T-cell leukemia/lymphoma cells. These data suggest the potential clinical benefit and underlying molecular mechanism of combining carfilzomib with vorinostat in the treatment of human T-cell leukemia/lymphoma.

Pterostilbene induces apoptosis and cell cycle arrest in diffuse large B-cell lymphoma cells.

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma (NHL). Pterostilbene, a natural dimethylated analog of resveratrol, has been shown to possess diverse pharmacological activities, including anti-inflammatory, antioxidant and anticancer properties. However, to the best of our knowledge, there has been no study of the effects of pterostilbene upon hematological malignancies. Herein, we report the antitumor activity and mechanism of pterostilbene against DLBCL cells both in vitro and in vivo. We found that pterostilbene treatment resulted in a dose-dependent inhibition of cell viability. In addition, pterostilbene exhibited a strong cytotoxic effect, as evidenced not only by reductions of mitochondrial membrane potential (MMP) but also by increases in cellular apoptotic index and reactive oxygen species (ROS) levels, leading to arrest in the S-phase of the cell cycle. Furthermore, pterostilbene treatment directly up-regulated p-p38MAPK and down-regulated p-ERK1/2. In vivo, intravenous administration of pterostilbene inhibited tumor development in xenograft mouse models. Overall, the results suggested that pterostilbene is a potential anti-cancer pharmaceutical against human DLBCL by a mechanism involving the suppression of ERK1/2 and activation of p38MAPK signaling pathways.

Abnormal expression of matrix metalloproteinase-2 and -9 in interspecific pregnancy of rat embryos in mouse recipients.

The high failure rate of interspecific pregnancy is a major obstacle to the successful interspecific cloning of mammals. Embryo transfer between rats and mice provides a unique model for studying the causes of such failures. Previous research has shown that the upper time limit for the survival of rat embryos in mouse uteri was the seventh day of pregnancy (Day 7). To study the reasons for the failure of interspecific pregnancy between rats and mice, we transferred rat blastocysts into mouse uteri on the third day of pseudopregnancy. Unexpectedly, intact rat embryos could still be observed in mouse uteri on Day 9 and the implantation rate was as high as 30.6%. However, compared with mouse embryos, the further development of transferred rat embryos in mouse uteri was retarded. On Day 10, transferred rat embryos shrank with much blood. From Day 11 on, they lost their intact structure and the recipient uteri developed dropsy. On Day 12, the embryos shrank further and completely separated from the mouse uteri. By Day 13, they had been absorbed without any remains. In an in vitro co-culture (CT) system, the attachment rate of rat embryos on a monolayer of mouse uterine epithelial cells was similar to that of mouse embryos, but the outgrowth rate of rat embryos was significantly lower. Further investigation by gelatin zymography showed that matrix metalloproteinase-2 (MMP-2) and metalloproteinase-9 (MMP-9) activities in transferred rat embryos was significantly less than in mouse embryos. The same result was obtained in the in vitro CT assay. These results suggest that rat embryos can complete adhesion but not the invasion when transferred into mouse uteri. The reduced invasive ability, and especially, the associated reduction of MMP-2 and -9 activity, is one of the reasons for the failure of interspecific pregnancy.

MNKs act as a regulatory switch for eIF4E1 and eIF4E3 driven mRNA translation in DLBCL.

The phosphorylation of eIF4E1 at serine 209 by MNK1 or MNK2 has been shown to initiate oncogenic mRNA translation, a process that favours cancer development and maintenance. Here, we interrogate the MNK-eIF4E axis in diffuse large B-cell lymphoma (DLBCL) and show a distinct distribution of MNK1 and MNK2 in germinal centre B-cell (GCB) and activated B-cell (ABC) DLBCL. Despite displaying a differential distribution in GCB and ABC, both MNKs functionally complement each other to sustain cell survival. MNK inhibition ablates eIF4E1 phosphorylation and concurrently enhances eIF4E3 expression. Loss of MNK protein itself downregulates total eIF4E1 protein level by reducing eIF4E1 mRNA polysomal loading without affecting total mRNA level or stability. Enhanced eIF4E3 expression marginally suppresses eIF4E1-driven translation but exhibits a unique translatome that unveils a novel role for eIF4E3 in translation initiation. We propose that MNKs can modulate oncogenic translation by regulating eIF4E1-eIF4E3 levels and activity in DLBCL.