The role of proteasome inhibition in nonsmall cell lung cancer

Chemical Proteomics Reveals that the Anticancer Drug Everolimus Affects the Ubiquitin-Proteasome System

Rapamycin is a natural antifungal, immunosuppressive, and antiproliferative compound that allosterically inhibits mTOR complex 1. The ubiquitin-proteasome system (UPS) responsible for protein turnover is usually not listed among the pathways affected by mTOR signaling. However, some previous studies have indicated the interplay between the UPS and mTOR. It has also been reported that rapamycin and its analogs can allosterically inhibit the proteasome itself. In this work, we studied the molecular effect of rapamycin and its analogs (rapalogs), everolimus and temsirolimus, on the A549 cell line by expression proteomics. The analysis of differentially expressed proteins showed that the cellular response to everolimus treatment is strikingly different from that to rapamycin and temsirolimus. In the cluster analysis, the effect of everolimus was similar to that of bortezomib, a well-established proteasome inhibitor. UPS-related pathways were enriched in the cluster of proteins specifically upregulated upon everolimus and bortezomib treatments, suggesting that both compounds have similar proteasome inhibition effects. In particular, the total amount of ubiquitin was significantly elevated in the samples treated with everolimus and bortezomib, and analysis of the polyubiquitination patterns revealed elevated intensities of the ubiquitin peptide with a GG modification at the K48 residue, consistent with a bottleneck in proteasomal protein degradation. Moreover, the everolimus treatment resulted in both ubiquitin phosphorylation and generation of a significant amount of semitryptic peptides, illustrating the increase in the protease activity. These observations suggest that everolimus affects the UPS in a unique way, and its mechanism of action is different from that of its close chemical analogs, rapamycin and temsirolimus.

Small-molecule inhibitors targeting FOXM1: Current challenges and future perspectives in cancer treatments

Forkhead box (FOX) protein M1 (FOXM1) is a critical proliferation-associated transcription factor (TF) that is aberrantly overexpressed in the majority of human cancers and has also been implicated in poor prognosis. A comprehensive understanding of various aspects of this molecule has revealed its role in, cell proliferation, cell migration, invasion, angiogenesis and metastasis. The FOXM1 as a TF directly or indirectly regulates the expression of several target genes whose dysregulation is associated with almost all hallmarks of cancer. Moreover, FOXM1 expression is associated with chemoresistance to different anti-cancer drugs. Several studies have confirmed that suppression of FOXM1 enhanced the drug sensitivity of various types of cancer cells. Current data suggest that small molecule inhibitors targeting FOXM1 in combination with anticancer drugs may represent a novel therapeutic strategy for chemo-resistant cancers. In this review, we discuss the clinical utility of FOXM1, further, we summarize and discuss small-molecule inhibitors targeting FOXM1 and categorize them according to their mechanisms of targeting FOXM1. Despite great progress, small-molecule inhibitors targeting FOXM1 face many challenges, and we present here all small-molecule FOXM1 inhibitors in different stages of development. We discuss the current challenges and provide insights on the future application of FOXM1 inhibition to the clinic.

Molecular analysis of cell survival and death pathways in the proteasome inhibitor bortezomib-resistant PC3 prostate cancer cell line

The ubiquitin-proteasome pathway is an important protein quality control system involved in intracellular homeostasis. To achieve intracellular homeostasis, proteins that are misfolded as a result of translational errors or genetic mutations must be eliminated by the ubiquitin-proteasome pathway. In our previous publications, we determined that 4T1 breast and B16F10 melanoma cancer cells have differential levels of resistance to proteasome inhibitors. Again, in the previous studies, we reported that 4T1 cell cultures, despite being p53-mutant, underwent apoptosis as a result of bortezomib treatment. The first goal of this study was to verify the resistance levels of parental and resistant PC3 prostate cancer cells to bortezomib using WST-1 test. As a result of treatment with different bortezomib concentrations for 48 h, the IC₅₀ value of the parental cells was determined as 32.8 nM and that of the resistant cells was determined as 346 nM. This result showed that the resistant cells were at least 10.5 times more resistant. In addition, to determine whether the resistance gained was reversible or not, the cells were passaged in a medium without bortezomib for one month. The IC₅₀ value determination by WST-1 test showed that the resistant PC3 cells gained an irreversible bortezomib resistance phenotype. The results of the 3D spheroid experiment showed that the 3D spheroid diameter of resistant cells was significantly higher than that of the parental cells. The studies conducted with Western blot showed that ERK1 MAPK T202 phosphorylation and the conversion of autophagy marker LC3-I to LC3-II were significantly increased in parental cells as compared to the resistant cells. Finally, the results showed that while both maternal embryonic leucine zipper kinase (MELK) inhibitor OTSSP167 and Ca²⁺ chelator BAPTA-AM (also an inhibitor of the expression of antiapoptotic protein GRP78) are promising agents for cancer cells resistant to the proteasome inhibitors, CDK2 inhibitor CVT-313 was found ineffective in both parental and the resistant cells.

Explaining the Genetic Causality for Complex Phenotype via Deep Association Kernel Learning

The genetic effect explains the causality from genetic mutations to the development of complex diseases. Existing genome-wide association study (GWAS) approaches are always built under a linear assumption, restricting their generalization in dissecting complicated causality such as the recessive genetic effect. Therefore, a sophisticated and general GWAS model that can work with different types of genetic effects is highly desired. Here, we introduce a deep association kernel learning (DAK) model to enable automatic causal genotype encoding for GWAS at pathway level. DAK can detect both common and rare variants with complicated genetic effects where existing approaches fail. When applied to four real-world GWAS datasets including cancers and schizophrenia, our DAK discovered potential casual pathways, including the association between dilated cardiomyopathy pathway and schizophrenia.

An investigation of the mechanisms underlying the proteasome inhibitor bortezomib resistance in PC3 prostate cancer cell line

The phenomenon of acquired resistance to chemotherapeutic agents is a long-standing conundrum in cancer treatment. To help delineate drug resistance mechanisms and pave the way for the development of novel strategies, we generated a PC3 prostate cancer cell line resistant to proteasome inhibitor bortezomib for the first time. The resistant cells were found to have an IC₅₀ value of 359.6 nM, whereas the IC₅₀ value of parental cells was 82.6 nM after 24 h of treatment with varying doses of bortezomib. The resistant cells were also partly cross-resistant to the novel proteasome inhibitor carfilzomib; however, they were not resistant to widely used chemotherapeutic agent vincristine sulfate, indicating that enhanced cellular drug efflux via the multidrug resistance (MDR) transporters is not the molecular basis of the resistance. Since both bortezomib and carfilzomib target and inhibit the chymotrypsin-related activity residing in the β5 subunit of the proteasome (PSMB5), we next examined its expression and found surprisingly no significant alteration in the expression profile of the mature form. However, a significant increase in the accumulation of the precursor form of PSMB5 in response to 100 nM bortezomib was observed in the parental cells without a significant accumulation in the resistant cells. The results presented here thus suggest that the molecular mechanisms causing resistance to proteasome inhibitors need to be examined in-depth to overcome the resistance to ubiquitin-proteasome pathway inhibitors in cancer treatment.

Quantitative structure-activity relationship and molecular docking studies on human proteasome inhibitors for anticancer activity targeting NF-κB signaling pathway

The abnormal ubiquitin-proteasome is found as an important target in various human diseases, especially in cancer, and recently it has received prevalent attention as a challenging therapeutic target. The current work is designed to derive a predictive two-dimensional quantitative structure-activity relationship model for anticancer human proteasome target of NF-κB signaling pathway. The established 2 D-QSAR is dependent on multiple linear regression approach and validated through leave-One-Out and external test set prediction method. The robust QSAR model showed the r² of 0.83 and q² of 0.80 and pred_r² of 0.77. Three chemical properties, electronegativity count, average potential, and T_2_N_6 were identified as significant descriptors to predict the anticancer activities of the proteasome antagonists. Besides, the predicted top hit compounds were considered to check out the compliance with Rule of five and pharmacokinetic parameters for oral bioavailability in the human body. The molecular docking was accomplished to unravel the molecular mode of action of best-predicted compounds which was compatible with the standard drug. Following this approach, lastly two compounds NP and AP were recognized as the best candidates since these top compounds follow all the standard limit point of entire filters and indicated effective and decent docking score. The outcomes of the study sturdily suggested that the developed model and top hit compound's binding conformation are rational in the exploration of unknown antagonist's anticancer activity. The research would be of great support and is supposed to be of immense significance in the development and designing of drug-like candidates in preliminary drug discovery. Communicated by Ramaswamy H. Sarma.

Impact of viral presence in tumor on gene expression in non-small cell lung cancer

Background

In our recent study, most non-small-lung cancer (NSCLC) tumor specimens harbored viral DNA but it was absent in non-neoplastic lung. However, their targets and roles in the tumor cells remain poorly understood. We analyzed gene expression microarrays to identify genes and pathways differentially altered between virus-infected and uninfected NSCLC tumors.

Methods

Gene expression microarrays of 30 primary and 9 metastatic NSCLC patients were preprocessed through a series of quality control analyses. Linear Models for Microarray Analysis and Gene Set Enrichment Analysis were used to assess differential expression.

Results

Various genes and gene sets had significantly altered expressions between virus-infected and uninfected NSCLC tumors. Notably, 22 genes on the viral carcinogenesis pathway were significantly overexpressed in virus-infected primary tumors, along with three oncogenic gene sets. A total of 12 genes, as well as seven oncogenic and 133 immunologic gene sets, were differentially altered in squamous cell carcinomas, depending on the virus. In adenocarcinoma, 14 differentially expressed genes (DEGs) were identified, but no oncogenic and immunogenic gene sets were significantly altered. In bronchioloalveolar carcinoma, several genes were highly overexpressed in virus-infected specimens, but not statistically significant. Only five of 69 DEGs (7.2%) from metastatic tumor analysis overlapped with 1527 DEGs from the primary tumor analysis, indicating differences in host cellular targets and the viral impact between primary and metastatic NSCLC.

Conclusions

The differentially expressed genes and gene sets were distinctive among infected viral types, histological subtypes, and metastatic disease status of NSCLC. These results support the hypothesis that tumor viruses play a role in NSCLC by regulating host genes in tumor cells during NSCLC differentiation and progression.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4748-0) contains supplementary material, which is available to authorized users.

Relapse-related long non-coding RNA signature to improve prognosis prediction of lung adenocarcinoma

Increasing evidence has highlighted the important roles of dysregulated long non-coding RNA (lncRNA) expression in tumorigenesis, tumor progression and metastasis. However, lncRNA expression patterns and their prognostic value for tumor relapse in lung adenocarcinoma (LUAD) patients have not been systematically elucidated. In this study, we evaluated lncRNA expression profiles by repurposing the publicly available microarray expression profiles from a large cohort of LUAD patients and identified specific lncRNA signature closely associated with tumor relapse in LUAD from significantly altered lncRNAs using the weighted voting algorithm and cross-validation strategy, which was able to discriminate between relapsed and non-relapsed LUAD patients with sensitivity of 90.9% and specificity of 81.8%. From the discovery dataset, we developed a risk score model represented by the nine relapse-related lncRNAs for prognosis prediction, which classified patients into high-risk and low-risk subgroups with significantly different recurrence-free survival (HR=45.728, 95% CI=6.241-335.1; p=1.69e-04). The prognostic value of this relapse-related lncRNA signature was confirmed in the testing dataset and other two independent datasets. Multivariable Cox regression analysis and stratified analysis showed that the relapse-related lncRNA signature was independent of other clinical variables. Integrative in silico functional analysis suggested that these nine relapse-related lncRNAs revealed biological relevance to disease relapse, such as cell cycle, DNA repair and damage and cell death. Our study demonstrated that the relapse-related lncRNA signature may not only help to identify LUAD patients at high risk of relapse benefiting from adjuvant therapy but also could provide novel insights into the understanding of molecular mechanism of recurrent disease.

Visualizing the antivascular effect of bortezomib on the hypoxic tumor microenvironment

Bortezomib, a novel proteasome inhibitor, has been approved for treating multiple myeloma and mantle cell lymphoma and studied pre-clinically and clinically for solid tumors. Preferential cytotoxicity of bortezomib was found toward hypoxic tumor cells and endothelial cells in vitro. The purpose of this study is to investigate the role of a pretreatment hypoxic tumor microenvironment on the effects of bortezomib in vitro and ex vivo, and explore the feasibility of dynamic contrast enhanced magnetic resonance imaging (DCE MRI) to noninvasively evaluate the biological effects of bortezomib. It was shown in vitro by Western blot, flow cytometry, and ELISA that bortezomib accumulated HIF-1α in non-functional forms and blocks its hypoxia response in human colorectal cancer cell lines. Ex vivo experiments were performed with fluorescent immunohistochemical staining techniques using multiple endogenous and exogenous markers to identify hypoxia (pimonidazole, HRE-TKeGFP), blood flow/permeability (Hoechst 33342), micro-vessels (CD31 and SMA), apoptosis (cleaved caspase 3) and hypoxia response (CA9). After bortezomib administration, overall apoptosis index was significantly increased and blood perfusion was dramatically decreased in tumor xenografts. More importantly, apoptosis signals were found preferentially located in moderate and severe pretreatment hypoxic regions in both tumor and endothelial cells. Meanwhile, DCE MRI examinations showed that the tumor blood flow and permeability decreased significantly after bortezomib administration. The present study revealed that bortezomib reduces tumor hypoxia response and blood perfusion, thus, presenting antivascular properties. It will be important to determine the hypoxic/perfusion status pre- and during treatment at further translational studies.

Emerging role of immunoproteasomes in pathophysiology

The immunoproteasome is a proteasome variant that is found only in jawed vertebrates. It is responsible for degrading intracellular proteins to generate a major source of peptides with substantial major histocompatibility complex I binding affinity. The immunoproteasome also has roles in T-cell survival, differentiation and proliferation in various pathological conditions. In humans, any alteration in the expression, assembly or function of the immunoproteasome can lead to cancer, autoimmune disorders or inflammatory diseases. Although the roles of the immunoproteasome in cancer and neurodegenerative disorders have been extensively studied, its significance in other disease conditions has only recently become known. Therefore, there is renewed interest in the development of drugs, vaccines and biomarkers that target the immunoproteasome. The current review highlights the involvement of this complex in disease pathology in addition to the advances made in immunoproteasome research.

KRAS-Mutant Lung Cancers in the Era of Targeted Therapy

KRAS-mutant lung cancers account for approximately 25% of non-small cell lung carcinomas, thus representing an enormous burden of cancer worldwide. KRAS mutations are clear drivers of tumor growth and are characterized by a complex biology involving the interaction between mutant KRAS, various growth factor pathways, and tumor suppressor genes. While KRAS mutations are classically associated with a significant smoking history, they are also identified in a substantial proportion of never-smokers. These mutations are found largely in lung adenocarcinomas with solid growth patterns and tumor-infiltrating lymphocytes. A variety of tools are available for diagnosis including Sanger sequencing, multiplex mutational hotspot profiling, and next-generation sequencing. The prognostic and predictive roles of KRAS status remain controversial. It has become increasingly clear, however, that KRAS mutations drive primary resistance to EGFR tyrosine kinase inhibition. Until recently, mutant KRAS was not thought of as a clinically-targetable driver in lung cancers. With the expansion of our knowledge regarding the biology of KRAS-mutant lung cancers and the role of MEK and PI3K/mTOR inhibition, the face of targeted therapeutics for this genomic subset of patients is slowly beginning to change.

NF-κB drives acquired resistance to a novel mutant-selective EGFR inhibitor

The clinical efficacy of EGFR tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC) harbouring activating EGFR mutations is limited by the emergence of acquired resistance, mostly ascribed to the secondary EGFR-T790M mutation. Selective EGFR-T790M inhibitors have been proposed as a new, extremely relevant therapeutic approach. Here, we demonstrate that the novel irreversible EGFR-TKI CNX-2006, a structural analog of CO-1686, currently tested in a phase-1/2 trial, is active against in vitro and in vivo NSCLC models expressing mutant EGFR, with minimal effect on the wild-type receptor. By integration of genetic and functional analyses in isogenic cell pairs we provide evidence of the crucial role played by NF-κB1 in driving CNX-2006 acquired resistance and show that NF-κB activation may replace the oncogenic EGFR signaling in NSCLC when effective and persistent inhibition of the target is achieved in the presence of the T790M mutation. In this context, we demonstrate that the sole, either genetic or pharmacologic, inhibition of NF-κB is sufficient to reduce the viability of cells that adapted to EGFR-TKIs. Overall, our findings support the rational inhibition of members of the NF-κB pathway as a promising therapeutic option for patients who progress after treatment with novel mutant-selective EGFR-TKIs.

Combined inhibition of Hsp90 and the proteasome affects NSCLC proteostasis and attenuates cell migration

Lung cancer remains the most common cause of cancer-related death worldwide. This malignancy is a complex disease, and it is important to identify potential biological targets, the blockade of which would affect multiple downstream signaling cascades. A growing number of reports recognize novel therapeutic targets in the protein homeostasis network responsible for generating and protecting the protein fold. The heat shock protein 90 (Hsp90) is an essential molecular chaperon involved in the posttranslational folding and stability of proteins. It is required for conformational maturation of multiple oncogenic kinases that drive signal transduction and proliferation of cancer cells. However, in the case of unfolded protein accumulation endoplasmic reticulum (ER) stress is induced and several response pathways such as proteasome functions are activated. The ubiquitin-proteasome system orchestrates the turnover of innumerable cellular proteins. Here, we suggest that the therapeutic efficacy of Hsp90 inhibition may be augmented by coadministering proteasome inhibitor on human non-small-cell lung cancer (NSCLC) cell lines. Indeed, we showed that coadministration of the Hsp90 inhibitor 17-demethoxygeldanamycin (17-DMAG) and proteasome inhibitor (velcade) induced ER stress evidenced by increased unfolded protein response markers. The consequences were evident in multiple aspects of the NSCLC phenotype: reduced viability and cell count, increased apoptotic cell death, and most profoundly, synergistically decreased cell motility. Our findings provide proof-of-concept that targeting ER homeostasis is therapeutically beneficial in NSCLC cell lines.

Carfilzomib demonstrates broad anti-tumor activity in pre-clinical non-small cell and small cell lung cancer models

BACKGROUND

Carfilzomib (CFZ) is a proteasome inhibitor that selectively and irreversibly binds to its target and has been approved in the US for treatment of relapsed and refractory multiple myeloma. Phase 1B studies of CFZ reported signals of clinical activity in solid tumors, including small cell lung cancer (SCLC). The aim of this study was to investigate the activity of CFZ in lung cancer models.

METHODS

A diverse panel of human lung cancer cell lines and a SHP77 small cell lung cancer xenograft model were used to investigate the anti-tumor activity of CFZ.

RESULTS

CFZ treatment inhibited both the constitutive proteasome and the immunoproteasome in lung cancer cell lines. CFZ had marked anti-proliferative activity in A549, H1993, H520, H460, and H1299 non-small cell lung cancer (NSCLC) cell lines, with IC50 values after 96 hour exposure from <1.0 nM to 36 nM. CFZ had more variable effects in the SHP77 and DMS114 SCLC cell lines, with IC50 values at 96 hours from <1 nM to 203 nM. Western blot analysis of CFZ-treated H1993 and SHP77 cells showed cleavage of poly ADP ribose polymerase (PARP) and caspase-3, indicative of apoptosis, and induction of microtubule-associated protein-1 light chain-3B (LC3B), indicative of autophagy. In SHP77 flank xenograft tumors, CFZ monotherapy inhibited tumor growth and prolonged survival, while no additive or synergistic anti-tumor efficacy was observed for CFZ + cisplatin (CDDP).

CONCLUSIONS

CFZ demonstrated anti-proliferative activity in lung cancer cell lines in vitro and resulted in a significant survival advantage in mice with SHP77 SCLC xenografts, supporting further pre-clinical and clinical investigations of CFZ in NSCLC and SCLC.

Regulation of the proteasome: evaluating the lung proteasome as a new therapeutic target

SIGNIFICANCE

Lung diseases are on the second rank worldwide with respect to morbidity and mortality. For most respiratory diseases, no effective therapies exist. Whereas the proteasome has been successfully evaluated as a novel target for therapeutic interventions in cancer, neurodegenerative, and cardiac disorders, there is a profound lack of knowledge on the regulation of proteasome activity in chronic and acute lung diseases.

RECENT ADVANCES

There are various means of how the amount of active proteasome complexes in the cell can be regulated such as transcriptional regulation of proteasomal subunit expression, association with different regulators, assembly and half-life of proteasomes and regulatory complexes, as well as post-translational modifications. It also becomes increasingly evident that proteasome activity is fine-tuned and depends on the state of the cell. We propose here that 20S proteasomes and their regulators can be regarded as dynamic building blocks, which assemble or disassemble in response to cellular needs. The composition of proteasome complexes in a cell may vary depending on tissue, cell type and compartment, stage of development, or pathological context.

CRITICAL ISSUES AND FUTURE DIRECTIONS

Dissecting the expression and regulation of the various catalytic forms of 20S proteasomes, such as constitutive, immuno-, and mixed proteasomes, together with their associated regulatory complexes will not only greatly enhance our understanding of proteasome function in lung pathogenesis but will also pave the way to develop new classes of drugs that inhibit or activate proteasome function in a defined setting for treatment of lung diseases.

Secretory phospholipase A2-IIa upregulates HER/HER2-elicited signaling in lung cancer cells

Lung cancer is the leading cause of cancer death worldwide. There is an urgent need for early diagnostic tools and novel therapies in order to increase lung cancer survival. Secretory phospholipase A2 group IIa (sPLA2-IIa) is involved in inflammation, tumorigenesis and metastasis. We were the first to uncover that cancer cells secrete sPLA2‑IIa. sPLA2‑IIa is overexpressed in almost all specimens of human lung cancers examined and is significantly elevated in the plasma of lung cancer patients. High levels of plasma sPLA2-IIa are significantly associated with advanced stage and decreased overall cancer survival. In this study, we further showed that elevated HER/HER2‑PI3K-Akt-NF-κB signaling contributes to sPLA2-IIa overexpression in lung cancer cells. sPLA2-IIa in turn phosphorylates and activates HER2 and HER3 in a time- and dose‑dependent manner in lung cancer cells. The structure and sequence‑based docking analysis revealed that sPLA2-IIa β hairpin shares structural similarity with the corresponding EGF hairpin. sPLA2-IIa forms an extensive interface with EGFR and brings the two lobes of EGFR into an active conformation. sPLA2-IIa also enhances the NF-κB promoter activity. Anti-sPLA2-IIa antibody, but not the small molecule sPLA2-IIa inhibitor LY315920, significantly inhibits sPLA2‑IIa-induced activation of NF-κB promoter. Our findings support the notion that sPLA2-IIa functions as a ligand for the EGFR family of receptors leading to an elevated HER/HER2-elicited signaling. Plasma sPLA2-IIa can potentially serve as lung cancer biomarker and sPLA2‑IIa is a potential therapeutic target against lung cancer.

An historic perspective of proteasome inhibition

The ubiquitin-proteasome system (UPS) and associated signaling pathways are regarded today as an exciting area of development for novel therapeutics. However, two decades ago, following the discovery and elucidation of ubiquitin and the 26S proteasome as key mediators of protein turnover, the concept of inhibiting the UPS was not even considered a feasible therapeutic approach due to the assumption that inhibition of this pathway would have widespread deleterious effects. Subsequent clinical developments with the first-in-class proteasome inhibitor bortezomib have radically overturned that view, with the proteasome now recognized as a validated target and proteasome inhibition demonstrated to be a highly successful treatment for a number of hematologic malignancies. Here we provide a historic perspective on the emergence of proteasome inhibition, sharing some of the lessons learned along the way. We describe the development of bortezomib and the elucidation of the effects of its novel mechanism of action, and place the cutting-edge work described elsewhere in this issue in the context of these historic developments.

Enhanced heme function and mitochondrial respiration promote the progression of lung cancer cells

Lung cancer is the leading cause of cancer-related mortality, and about 85% of the cases are non-small-cell lung cancer (NSCLC). Importantly, recent advance in cancer research suggests that altering cancer cell bioenergetics can provide an effective way to target such advanced cancer cells that have acquired mutations in multiple cellular regulators. This study aims to identify bioenergetic alterations in lung cancer cells by directly measuring and comparing key metabolic activities in a pair of cell lines representing normal and NSCLC cells developed from the same patient. We found that the rates of oxygen consumption and heme biosynthesis were intensified in NSCLC cells. Additionally, the NSCLC cells exhibited substantially increased levels in an array of proteins promoting heme synthesis, uptake and function. These proteins include the rate-limiting heme biosynthetic enzyme ALAS, transporter proteins HRG1 and HCP1 that are involved in heme uptake, and various types of oxygen-utilizing hemoproteins such as cytoglobin and cytochromes. Several types of human tumor xenografts also displayed increased levels of such proteins. Furthermore, we found that lowering heme biosynthesis and uptake, like lowering mitochondrial respiration, effectively reduced oxygen consumption, cancer cell proliferation, migration and colony formation. In contrast, lowering heme degradation does not have an effect on lung cancer cells. These results show that increased heme flux and function are a key feature of NSCLC cells. Further, increased generation and supply of heme and oxygen-utilizing hemoproteins in cancer cells will lead to intensified oxygen consumption and cellular energy production by mitochondrial respiration, which would fuel cancer cell proliferation and progression. The results show that inhibiting heme and respiratory function can effectively arrest the progression of lung cancer cells. Hence, understanding heme function can positively impact on research in lung cancer biology and therapeutics.

Overexpression of FoxM1 offers a promising therapeutic target in diffuse large B-cell lymphoma

BACKGROUND

FoxM1 has been shown to play a critical role in the pathogenesis of various epithelial malignancies. However, its role in lymphoid malignancies has not been fully clarified. We, therefore, investigated the role of FoxM1 expression in a large cohort of diffuse large B-cell lymphoma samples and panel of cell lines.

DESIGN AND METHODS

FoxM1 expression was investigated in a large series of diffuse large B-cell lymphoma tissues in a tissue microarray format by immunohistochemistry. Apoptosis was measured by flow cytometry and protein expression was detected by immunoblotting using diffuse large B-cell lymphoma cell lines following treatment with either pharmacological inhibitor of FoxM1 or small interference RNA knockdown strategy. Invasion/migration and soft agar colony assays were also performed following treatment with FoxM1 inhibitor.

RESULTS

FoxM1 expression was detected in 84.6% of diffuse large B-cell lymphoma tumors and found to be significantly associated with proliferative tumor marker Ki67 (P<0.0001), matrix metalloproteinases-2 (P=0.0008), matrix metalloproteinases-9 (P=0.0002), S-phase kinase associated protein-2 (P<0.0001) and inversely associated with p27 expression (P=0.0215). Expression of small interference RNA targeted against FoxM1 or treatment of diffuse large B-cell lymphoma cells with thiostrepton caused its downregulation accompanied by decreased expression of matrix metalloproteinases-2 and matrix metalloproteinases-9. Inhibition of FoxM1 in diffuse large B-cell lymphoma cells also decreased invasive and migratory capability, and induced caspase dependent apoptosis via activation of the mitochondrial apoptotic pathway. Finally, combined thiostrepton and bortezomib at sub-toxic doses led to efficient apoptosis in diffuse large B-cell lymphoma cells.

CONCLUSIONS

Altogether, these results suggest that FoxM1 is over-expressed in the majority of diffuse large B-cell lymphoma samples. These data also indicate that targeting FoxM1 signaling can serve as a potential therapeutic modality in the management of diffuse large B-cell lymphoma.

Heterozygosity for the proteasomal Psmc1 ATPase is insufficient to cause neuropathology in mouse brain, but causes cell cycle defects in mouse embryonic fibroblasts

The ubiquitin proteasome system (UPS) is a fundamental cellular pathway, degrading most unwanted intracellular soluble proteins. Dysfunction of the UPS has been associated with normal aging as well as various age-related pathological conditions, including chronic human neurodegenerative diseases such as Alzheimer's and Parkinson's diseases, leading to a significant interest in the involvement of this degradative system in neurones. We previously reported that the 26S proteasome was essential for neuronal homeostasis and survival in mouse brains following conditional genetic homozygous knockout of a key subunit of the multi-meric 26S proteasome (19S ATPase Psmc1). Here, we investigated the effects of Psmc1 heterozygosity in the mouse brain and primary mouse embryonic fibroblasts. Neuropathologically and biochemically, Psmc1 heterozygous (Psmc1(+/-)) knockout mice were indistinguishable from wild-type mice. However, we report a novel age-related accumulation of intraneuronal lysine 48-specific polyubiquitin-positive granular staining in both wild-type and heterozygous Psmc1 knockout mouse brain. In Psmc1(+/-) MEFs, we found a significant decrease in PSMC1 levels, altered 26S proteasome assembly and a notable G2/M cell cycle arrest that was not associated with an increase in the cell cycle regulatory protein p21. The disturbance in cell cycle progression may be responsible for the growth inhibitory effects in Psmc1(+/-) MEFs.

Immunohistochemical analysis of the ubiquitin-conjugating enzyme UbcH10 in lung cancer: a useful tool for diagnosis and therapy

The ubiquitin-conjugating enzyme (UbcH10) plays important roles in the regulation of cell cycle progression. Recently, UbcH10 expression has been demonstrated in several human and experimental tumors, and proteasome inhibitors have been tested in trials for pulmonary neoplasms; however, the underlying mechanisms as well as the clinicopathological relevance of UbcH10 in the genesis and progression of lung cancer remain largely unknown. Therefore, the authors evaluated the expression of UbcH10 in human lung cancer and evaluated its possible diagnostic and prognostic use. They found that most cases of lung adenocarcinoma, squamous cell carcinoma, and large cell and small cell carcinoma were positive for UbcH10. The expression levels of UbcH10 progressively increased with decreasing degree of tumor differentiation. There was a statistically significant difference of UbcH10 positivity between grade I/III of lung adenocarcinoma (p=0.013) and squamous cell carcinoma (p=0.002). No significant differences were found between histological types (p=0.072). In the case of cell blocks prepared from pleural effusions, inflammatory and reactive mesothelial elements did not show appreciable UbcH10 expression, whereas neoplastic cells exhibited clear UbcH10 positivity. The results suggest that UbcH10 might represent a new and promising diagnostic and prognostic marker in both histologic and cytologic specimens of lung cancer.