The proteasomal and apoptotic phenotype determine bortezomib sensitivity of non-small cell lung cancer cells

Enhanced angiogenesis of human umbilical vein endothelial cells via THP-1-derived M2c-like macrophages and treatment with proteasome inhibitors 'bortezomib and ixazomib'

The leading cause of cancer-related death is lung cancer, with metastasis being the most common cause of death. To elucidate the role of macrophages in lung cancer and angiogenesis processes, we established an in vitro co-culture model of A549 or HUVEC with THP-1 cells that polarized to M2c macrophages with hydrocortisone. The proteasome inhibitors bortezomib and ixazomib were investigated for their effects on proliferation, invasion, migration, metastasis, and angiogenesis pathways. The effects of bortezomib and ixazomib on gene expression in gene panels, including crucial genes related to angiogenesis and proteasomes, were investigated after the co-culture model to determine these effects at the molecular level. In conclusion, bortezomib and ixazomib showed antiproliferative effects in both cells, as well as in M2c macrophage co-culture. M2c macrophages also increased invasion in A549 cells and both invasion and migration in HUVEC. mRNA expression upregulation, specifically in the NFKB and VEGF genes, supported the metastatic and angiogenic effects found in A549 and HUVEC with M2c macrophage co-culture. Additionally, bortezomib inhibited the VEGFB pathway in HUVEC and NFKB1 in A549 cells. The significant findings obtained as a result of this study will provide information regarding angiogenesis induced by M2 macrophages.

Non-classical ferroptosis inhibition by a small molecule targeting PHB2

Ferroptosis is a new type of programmed cell death characterized by iron-dependent lipid peroxidation. Ferroptosis inhibition is thought as a promising therapeutic strategy for a variety of diseases. Currently, a majority of known ferroptosis inhibitors belong to either antioxidants or iron-chelators. Here we report a new ferroptosis inhibitor, termed YL-939, which is neither an antioxidant nor an iron-chelator. Chemical proteomics revealed the biological target of YL-939 to be prohibitin 2 (PHB2). Mechanistically, YL-939 binding to PHB2 promotes the expression of the iron storage protein ferritin, hence reduces the iron content, thereby decreasing the susceptibility to ferroptosis. We further showed that YL-939 could substantially ameliorate liver damage in a ferroptosis-related acute liver injury model by targeting the PHB2/ferritin/iron axis. Overall, we identified a non-classical ferroptosis inhibitor and revealed a new regulation mechanism of ferroptosis. These findings may present an attractive intervention strategy for ferroptosis-related diseases.

Modulating TRADD to restore cellular homeostasis and inhibit apoptosis

Cell death in human diseases is often a consequence of disrupted cellular homeostasis. If cell death is prevented without restoring cellular homeostasis, it may lead to a persistent dysfunctional and pathological state. Although mechanisms of cell death have been thoroughly investigated^1-3, it remains unclear how homeostasis can be restored after inhibition of cell death. Here we identify TRADD^4-6, an adaptor protein, as a direct regulator of both cellular homeostasis and apoptosis. TRADD modulates cellular homeostasis by inhibiting K63-linked ubiquitination of beclin 1 mediated by TRAF2, cIAP1 and cIAP2, thereby reducing autophagy. TRADD deficiency inhibits RIPK1-dependent extrinsic apoptosis and proteasomal stress-induced intrinsic apoptosis. We also show that the small molecules ICCB-19 and Apt-1 bind to a pocket on the N-terminal TRAF2-binding domain of TRADD (TRADD-N), which interacts with the C-terminal domain (TRADD-C) and TRAF2 to modulate the ubiquitination of RIPK1 and beclin 1. Inhibition of TRADD by ICCB-19 or Apt-1 blocks apoptosis and restores cellular homeostasis by activating autophagy in cells with accumulated mutant tau, α-synuclein, or huntingtin. Treatment with Apt-1 restored proteostasis and inhibited cell death in a mouse model of proteinopathy induced by mutant tau(P301S). We conclude that pharmacological targeting of TRADD may represent a promising strategy for inhibiting cell death and restoring homeostasis to treat human diseases.

Identification of key candidate tumor biomarkers in non-small-cell lung cancer by in silico analysis

Lung cancer is a common malignancy worldwide. The aim of the present study was to investigate differentially expressed genes (DEGs) between non-small-cell lung cancer (NSCLC) and normal lung tissue, and to reveal the potential molecular mechanism underlying NSCLC. The Gene Expression Omnibus database was used to obtain three gene expression profiles (GSE18842, GSE30219 and GSE33532). DEGs were obtained by GEO2R. Gene Ontology and pathway enrichment analyses were performed for DEGs in the Database for Annotation, Visualization and Integrated Discovery. A protein-protein interaction (PPI) network of DEGs was constructed and analyzed using the Search Tool for the Retrieval of Interacting Genes/Proteins database and Cytoscape software. A survival analysis was performed and protein expression levels of DEGs in human NSCLC were analyzed in order to determine clinical significance. A total of 764 DEGs were identified, consisting of 428 upregulated and 336 downregulated genes in NSCLC tissues compared with normal lung tissues, which were enriched in the 'cell cycle', 'cell adhesion molecules', 'p53 signaling pathway', 'DNA replication' and 'tight junction'. A PPI network of DEGs consisting of 51 nodes and 192 edges was constructed. The top 10 genes were identified as hub genes from the PPI network. High expression of 4 of the 10 hub genes was associated with worse overall survival rate in patients with NSCLC, including CDK1, PLK1, RAD51 and RFC4. In conclusion, the present study aids in improving the current understanding of aberrant gene expression between NSCLC tissues and normal lung tissues underlying tumorgenesis in NSCLC. Identified hub genes can be used as a tumor marker for diagnosis and prognosis or as a drug therapy target in NSCLC.

Next-generation proteasome inhibitors for cancer therapy

Over 2 decades ago, the proteasome was considered a risky or even untenable therapeutic target. Today, proteasome inhibitors are a mainstay in the treatment of multiple myeloma (MM) and have sales in excess of 3 billion US dollars annually. More importantly, the availability of proteasome inhibitors has greatly improved the survival and quality of life for patients with MM. Despite the remarkable success of proteasome inhibitor therapies to date, the potential for improvement remains, and the development and optimal use of proteasome inhibitors as anticancer agents continues to be an active area of research. In this review, we briefly discuss the features and limitations of the 3 proteasome inhibitor drugs currently used in the clinic and provide an update on current efforts to develop next-generation proteasome inhibitors with the potential to overcome the limitations of existing proteasome inhibitor drugs.

Positioning of proteasome inhibitors in therapy of solid malignancies

Targeting of the protein degradation pathway, in particular, the ubiquitin-proteasome system, has emerged as an attractive novel cancer chemotherapeutic modality. Although proteasome inhibitors have been most successfully applied in the treatment of hematological malignancies, they also received continuing interest for the treatment of solid tumors. In this review, we summarize the current positioning of proteasome inhibitors in the treatment of common solid malignancies (e.g., lung, colon, pancreas, breast, and head and neck cancer), addressing topics of their mechanism(s) of action, predictive factors and molecular mechanisms of resistance.

Endothelin-1 (ET-1) induces resistance to bortezomib in human multiple myeloma cells via a pathway involving the ETB receptor and upregulation of proteasomal activity

PURPOSE

Bortezomib (BTZ) is used for the treatment of multiple myeloma (MM). However, a significant proportion of patients may be refractory to the drug. This study aimed to investigate whether the endothelin (ET-1) axis may act as an escape mechanism to treatment with bortezomib in MM cells.

METHODS

NCI-H929 and RPMI-8226 (human MM cell lines) were cultured with or without ET-1, BTZ, and inhibitors of the endothelin receptors. ET-1 levels were determined by ELISA, while the protein levels of its receptors and of the PI3K and MAPK pathways' components by western blot. Effects of ET-1 on cell proliferation were studied by MTT and on the ubiquitin proteasome pathway by assessing the chymotryptic activity of the 20S proteasome in cell lysates.

RESULTS

Endothelin receptors A and B (ETAR and ETBR, respectively) were found to be expressed in both cell lines, with the RPMI-8226 cells that are considered resistant to BTZ, expressing higher levels of ETBR and in addition secreting ET-1. Treatment of the NCI-H929 cells with ET-1 increased proliferation, while co-incubation of these cells with ET-1 and BTZ decreased BTZ efficacy with concomitant upregulation of 20S proteasomal activity. Si-RNA silencing or chemical blockade of ETBR abrogated the protective effects of ET-1. Finally, data suggest that the predominant signaling pathway involved in ET-1/ETBR-induced BTZ resistance in MM cells may be the MAPK pathway.

CONCLUSION

Our data suggest a possible role of the ET-1/ETBR axis in regulating the sensitivity of MM cells to BTZ. Thus, combining bortezomib with strategies to target the ET-1 axis could prove to be a novel promising therapeutic approach in MM.

BAK and NOXA are critical determinants of mitochondrial apoptosis induced by bortezomib in mesothelioma

Based on promising preclinical efficacy associated with the 20S proteasome inhibitor bortezomib in malignant pleural mesothelioma (MPM), two phase II clinical trials have been initiated (EORTC 08052 and ICORG 05–10). However, the potential mechanisms underlying resistance to this targeted drug in MPM are still unknown. Functional genetic analyses were conducted to determine the key mitochondrial apoptotic regulators required for bortezomib sensitivity and to establish how their dysregulation may confer resistance. The multidomain proapoptotic protein BAK, but not its orthologue BAX, was found to be essential for bortezomib-induced apoptosis in MPM cell lines. Immunohistochemistry was performed on tissues from the ICORG-05 phase II trial and a TMA of archived mesotheliomas. Loss of BAK was found in 39% of specimens and loss of both BAX/BAK in 37% of samples. However, MPM tissues from patients who failed to respond to bortezomib and MPM cell lines selected for resistance to bortezomib conserved BAK expression. In contrast, c-Myc dependent transactivation of NOXA was abrogated in the resistant cell lines. In summary, the block of mitochondrial apoptosis is a limiting factor for achieving efficacy of bortezomib in MPM, and the observed loss of BAK expression or NOXA transactivation may be relevant mechanisms of resistance in the clinic.

The role of proteasome inhibition in nonsmall cell lung cancer

Lung cancer therapy with current available chemotherapeutic agents is mainly palliative. For these and other reasons there is now a great interest to find targeted therapies that can be effective not only palliating lung cancer or decreasing treatment-related toxicity, but also giving hope to cure these patients. It is already well known that the ubiquitin-proteasome system like other cellular pathways is critical for the proliferation and survival of cancer cells; thus, proteosome inhibition has become a very attractive anticancer therapy. There are several phase I and phase II clinical trials now in non-small cell lung cancer and small cell lung cancer using this potential target. Most of the trials use bortezomib in combination with chemotherapeutic agents. This paper tends to make a state-of-the-art review based on the available literature regarding the use of bortezomib as a single agent or in combination with chemotherapy in patients with lung cancer.

Emerging targeted therapies for bladder cancer: a disease waiting for a drug

Urothelial cell carcinoma is the fifth most common cancer and the costliest to treat. This is largely because of all new cases, about 70% present as superficial disease and this while rarely fatal, tends to recur, requiring long-term follow-up and repeat interventions. The standard of care, intravesical chemo- and immunotherapy, while effective, is associated with a considerable side-effect profile and approximately 30% of patients either fail to respond to treatment or suffer recurrent disease within 5 years. Muscle-invasive bladder cancer is life threatening, showing modest chemosensitivity, and usually requires radical cystectomy. Although bladder cancer is fairly well-genetically characterized, clinical trials with molecularly targeted agents have, in comparison to other solid tumors such as lung, breast and prostate, been few in number and largely unsuccessful, with no new agents being registered in the last 20 years. Hence, bladder cancer represents a considerable opportunity and challenge for molecularly targeted therapy.

Bortezomib induces schedule-dependent modulation of gemcitabine pharmacokinetics and pharmacodynamics in non-small cell lung cancer and blood mononuclear cells

Bortezomib combination with gemcitabine/cisplatin in patients with advanced tumors, predominantly non-small cell lung cancer (NSCLC), showed an unexpected transient drop in the deoxycytidine plasma levels, a marker for gemcitabine activity. This study investigates the pharmacokinetic/pharmacodynamic effect of bortezomib on gemcitabine in NSCLC and peripheral blood mononuclear cells (PBMC). Gemcitabine metabolites, including difluoro-dCTP (dFdCTP), were studied in PBMCs from bortezomib/gemcitabine/cisplatin-treated patients and from volunteers and NSCLC cells (H460 and SW1573) exposed to 4 h simultaneous or sequential treatments of gemcitabine (50 μmol/L, 4 h) and bortezomib (100 nmol/L, 2 h). Gemcitabine total phosphate levels measured by liquid chromatography-tandem mass spectrometry in PBMCs from bortezomib/gemcitabine/cisplatin-treated patients were strongly reduced after 90 min (-82.2%) up to 4 h post-gemcitabine infusion compared with gemcitabine/cisplatin-treated patients. Accordingly, bortezomib/gemcitabine combinations reduced dFdCTP in PBMCs treated ex vivo. Surprisingly, differential effects were observed in NSCLC cells. dFdCTP decreased after 4 h following gemcitabine removal in H460 but continued to increase for 24 h in SW1573. However, dFdCTP significantly increased (2-fold) in both cell lines in the bortezomib → gemcitabine exposure, coinciding with a major reduction in cell growth compared with single drugs, and the highest increase of deoxycytidine kinase expression, possibly mediated via E2F-1. Bortezomib affects differently gemcitabine pharmacokinetics/pharmacodynamics in PBMCs and NSCLC cells, suggesting that PBMCs are not adequate to evaluate the anticancer activity of bortezomib/gemcitabine combinations. The bortezomib → gemcitabine/cisplatin schedule appeared a safe and active combination for the treatment of advanced NSCLC and the bortezomib → gemcitabine was the most cytotoxic combination in NSCLC cells. The increase of deoxycytidine kinase and dFdCTP might contribute to this synergistic interaction and supports its further clinical investigation.

Bcl-2 family proteins contribute to apoptotic resistance in lung cancer multicellular spheroids

Combinatorial therapies using the proteasome inhibitor, bortezomib, have been found to induce synergistic apoptosis in cancer cells grown as monolayers; however, three-dimensional spheroid culture may be a better model for the multicellular resistance found in solid tumors, such as lung cancer. We tested the combinatorial apoptotic strategy of using bortezomib together with TNF-related apoptosis-inducing ligand (TRAIL), both in monolayers and in spheroids of A549 lung cancer cells. Indeed, bortezomib plus TRAIL induced synergistic apoptosis in A549 cells grown as monolayers, but had little effect on A549 cells grown as three-dimensional multicellular spheroids. The acquired resistance of spheroids was not due to a limitation of diffusion, to survival pathways, such as NF-kappaB or PI3K/Akt/mTOR, or to the up-regulation of FLIP(S) (Fas-associated death domain-like IL-1 beta-converting enzyme inhibitory protein, short). We then investigated a role for the Bcl-2 family of anti- and proapoptotic proteins. When cells formed spheroids, antiapoptotic Bcl-2 increased, whereas antiapoptotic Mcl-1 decreased. ABT-737, a small molecule that inhibits Bcl-2, but not Mcl-1, abolished the multicellular resistance of A549 spheroids to bortezomib plus TRAIL. In another lung cancer cell line, H1299, acquisition of multicellular resistance in spheroids was also accompanied by an increase in Bcl-2 and decrease in Mcl-1. In H1299 spheroids compared with those of A549, however, Mcl-1 remained higher, and Mcl-1 knockdown was more effective than ABT-737 in removing multicellular resistance. Our study suggests that the balance of Bcl-2 family proteins contributes to the acquired multicellular resistance of spheroids, and suggests a possible target for improving the response of lung cancer to bortezomib therapies.