An EORTC phase I study of Bortezomib in combination with oxaliplatin, leucovorin and 5-fluorouracil in patients with advanced colorectal cancer

Synergistic Effect of a Combination of Proteasome and Ribonucleotide Reductase Inhibitors in a Biochemical Model of the Yeast Saccharomyces cerevisiae and a Glioblastoma Cell Line

Proteasome inhibitors are used in the therapy of several cancers, and clinical trials are underway for their use in the treatment of glioblastoma (GBM). However, GBM becomes resistant to chemotherapy relatively rapidly. Recently, the overexpression of ribonucleotide reductase (RNR) genes was found to mediate therapy resistance in GBM. The use of combinations of chemotherapeutic agents is considered a promising direction in cancer therapy. The present work aimed to evaluate the efficacy of the combination of proteasome and RNR inhibitors in yeast and GBM cell models. We have shown that impaired proteasome function results in increased levels of RNR subunits and increased enzyme activity in yeast. Co-administration of the proteasome inhibitor bortezomib and the RNR inhibitor hydroxyurea was found to significantly reduce the growth rate of S. cerevisiae yeast. Accordingly, the combination of bortezomib and another RNR inhibitor gemcitabine reduced the survival of DBTRG-05MG compared to the HEK293 cell line. Thus, yeast can be used as a simple model to evaluate the efficacy of combinations of proteasome and RNR inhibitors.

ERCC1 abundance is an indicator of DNA repair-apoptosis decision upon DNA damage

DNA repair is essential for successful propagation of genetic material and fidelity of transcription. Nucleotide excision repair (NER) is one of the earliest DNA repair mechanisms, functionally conserved from bacteria to human. The fact that number of NER genes vary significantly between prokaryotes and metazoans gives the insight that NER proteins have evolved to acquire additional functions to combat challenges associated with a diploid genome, including being involved in the decision between DNA repair and apoptosis. However, no direct association between apoptosis and NER proteins has been shown to date. In this study, we induced apoptosis with a variety of agents, including oxaliplatin, doxorubicin and TRAIL, and observed changes in the abundance and molecular weight of NER complex proteins. Our results showed that XPA, XPC and ERCC1 protein levels change during DNA damage-induced apoptosis. Among these, ERCC1 decrease was observed as a pre-mitochondria depolarisation event which marks the "point of no return" in apoptosis signalling. ERCC1 decrease was due to proteasomal degradation upon lethal doses of oxaliplatin exposure. When ERCC1 protein was stabilised using proteasome inhibitors, the pro-apoptotic activity of oxaliplatin was attenuated. These results explain why clinical trials using proteasome inhibitors and platinum derivatives showed limited efficacy in carcinoma treatment and also the importance of how deep understanding of DNA repair mechanisms can improve cancer therapy.

Yeast Ribonucleotide Reductase Is a Direct Target of the Proteasome and Provides Hyper Resistance to the Carcinogen 4-NQO

Various external and internal factors damaging DNA constantly disrupt the stability of the genome. Cells use numerous dedicated DNA repair systems to detect damage and restore genomic integrity in a timely manner. Ribonucleotide reductase (RNR) is a key enzyme providing dNTPs for DNA repair. Molecular mechanisms of indirect regulation of yeast RNR activity are well understood, whereas little is known about its direct regulation. The study was aimed at elucidation of the proteasome-dependent mechanism of direct regulation of RNR subunits in Saccharomyces cerevisiae. Proteome analysis followed by Western blot, RT-PCR, and yeast plating analysis showed that upregulation of RNR by proteasome deregulation is associated with yeast hyper resistance to 4-nitroquinoline-1-oxide (4-NQO), a UV-mimetic DNA-damaging drug used in animal models to study oncogenesis. Inhibition of RNR or deletion of RNR regulatory proteins reverses the phenotype of yeast hyper resistance to 4-NQO. We have shown for the first time that the yeast Rnr1 subunit is a substrate of the proteasome, which suggests a common mechanism of RNR regulation in yeast and mammals.

UBE2J1 inhibits colorectal cancer progression by promoting ubiquitination and degradation of RPS3

Ubiquitin-conjugating enzyme E2 J1 (UBE2J1) has been proven to participate in the ubiquitination of multiple substrate proteins. However, the underlying mechanisms of UBE2J1 as a ubiquitin-conjugating enzyme participating in cancer development and progression remain largely unknown. Here, we identified that UBE2J1 is downregulated in colorectal cancer (CRC) tissues and cell lines which are mediated by DNA hypermethylation of its promoter, and decreased UBE2J1 is associated with poor prognosis. Functionally, UBE2J1 serving as a suppressor gene inhibits the proliferation and metastasis of CRC cells. Mechanistically, UBE2J1-TRIM25, forming an E2-E3 complex, physically interacts with and targets RPS3 for ubiquitination and degradation at the K214 residue. The downregulated RPS3 caused by UBE2J1 overexpression restrains NF-κB translocation into the nucleus and therefore inactivates the NF-κB signaling pathway. Our study revealed a novel role of UBE2J1-mediated RPS3 poly-ubiquitination and degradation in disrupting the NF-κB signaling pathway, which may serve as a novel and promising biomarker and therapeutic target for CRC.

Pharmacogenomics Testing in Phase I Oncology Clinical Trials: Constructive Criticism Is Warranted

Simple Summary

Phase I clinical trials are a cornerstone of pharmaceutical development in oncology. Many studies have now attempted to incorporate pharmacogenomics into phase I studies; however, many of these studies have fundamental flaws that that preclude interpretation and application of their findings. Study populations are often small and heterogeneous with multiple disease states, multiple dose levels, and prior therapies. Genetic testing typically includes few variants in candidate genes that do no encapsulate the full range of phenotypic variability in protein function. Moreover, a plurality of these studies do not present scientifically robust clinical or preclinical justification for undertaking pharmacogenomics studies. A significant amount of progress in understanding pharmacogenomic variability has occurred since pharmacogenomics approaches first began appearing in the literature. This progress can be immediately leveraged for the vast majority of Phase I studies. The purpose of this review is to summarize the current literature pertaining to Phase I incorporation of pharmacogenomics studies, analyze potential flaws in study design, and suggest approaches that can improve design of future scientific efforts.

Abstract

While over ten-thousand phase I studies are published in oncology, fewer than 1% of these studies stratify patients based on genetic variants that influence pharmacology. Pharmacogenetics-based patient stratification can improve the success of clinical trials by identifying responsive patients who have less potential to develop toxicity; however, the scientific limits imposed by phase I study designs reduce the potential for these studies to make conclusions. We compiled all phase I studies in oncology with pharmacogenetics endpoints (n = 84), evaluating toxicity (n = 42), response or PFS (n = 32), and pharmacokinetics (n = 40). Most of these studies focus on a limited number of agent classes: Topoisomerase inhibitors, antimetabolites, and anti-angiogenesis agents. Eight genotype-directed phase I studies were identified. Phase I studies consist of homogeneous populations with a variety of comorbidities, prior therapies, racial backgrounds, and other factors that confound statistical analysis of pharmacogenetics. Taken together, phase I studies analyzed herein treated small numbers of patients (median, 95% CI = 28, 24–31), evaluated few variants that are known to change phenotype, and provided little justification of pharmacogenetics hypotheses. Future studies should account for these factors during study design to optimize the success of phase I studies and to answer important scientific questions.

Management of Side Effects in the Personalized Medicine Era: Chemotherapy-Induced Peripheral Neurotoxicity

Pharmacogenomics is a powerful tool to predict individual response to treatment, in order to personalize therapy, and it has been explored extensively in oncology practice. Not only efficacy on the malignant disease has been investigated but also the possibility to predict adverse effects due to drug administration. Chemotherapy-induced peripheral neurotoxicity (CIPN) is one of those. This potentially severe and long-lasting/permanent side effect of commonly administered anticancer drugs can severely impair quality of life (QoL) in a large cohort of long survival patients. So far, a pharmacogenomics-based approach in CIPN regard has been quite delusive, making a methodological improvement warranted in this field of interest: even the most refined genetic analysis cannot be effective if not applied correctly. Here we try to devise why it is so, suggesting how THE "bench-side" (pharmacogenomics) might benefit from and should cooperate with THE "bed-side" (clinimetrics), in order to make genetic profiling effective if applied to CIPN.

A novel NF-κB regulator encoded by circPLCE1 inhibits colorectal carcinoma progression by promoting RPS3 ubiquitin-dependent degradation

BACKGROUND

Constitutive activation of nuclear factor-κB (NF-κB) signaling plays a key role in the development and progression of colorectal carcinoma (CRC). However, the underlying mechanisms of excessive activation of NF-κB signaling remain largely unknown.

METHODS

We used high throughput RNA sequencing to identify differentially expressed circular RNAs (circRNAs) between normal human intestinal epithelial cell lines and CRC cell lines. The identification of protein encoded by circPLCE1 was performed using LC-MS. The function of novel protein was validated in vitro and in vivo by gain or loss of function assays. Mechanistic results were concluded by immunoprecipitation analyses.

RESULTS

A novel protein circPLCE1-411 encoded by circular RNA circPLCE1 was identified as a crucial player in the NF-κB activation of CRC. Mechanistically, circPLCE1-411 promoted the ubiquitin-dependent degradation of the critical NF-κB regulator RPS3 via directly binding the HSP90α/RPS3 complex to facilitate the dissociation of RPS3 from the complex, thereby reducing NF-κB nuclear translocation in CRC cells. Functionally, circPLCE1 inhibited tumor proliferation and metastasis in CRC cells, as well as patient-derived xenograft and orthotopic xenograft tumor models. Clinically, circPLCE1 was downregulated in CRC tissues and correlated with advanced clinical stages and poor survival.

CONCLUSIONS

circPLCE1 presents an epigenetic mechanism which disrupts NF-κB nuclear translocation and serves as a novel and promising therapeutic target and prognostic marker.

Identifying Novel Actionable Targets in Colon Cancer

Colorectal cancer is the fourth cause of death from cancer worldwide, mainly due to the high incidence of drug-resistance toward classic chemotherapeutic and newly targeted drugs. In the last decade or so, the development of novel high-throughput approaches, both genome-wide and chemical, allowed the identification of novel actionable targets and the development of the relative specific inhibitors to be used either to re-sensitize drug-resistant tumors (in combination with chemotherapy) or to be synthetic lethal for tumors with specific oncogenic mutations. Finally, high-throughput screening using FDA-approved libraries of “known” drugs uncovered new therapeutic applications of drugs (used alone or in combination) that have been in the clinic for decades for treating non-cancerous diseases (re-positioning or re-purposing approach). Thus, several novel actionable targets have been identified and some of them are already being tested in clinical trials, indicating that high-throughput approaches, especially those involving drug re-positioning, may lead in a near future to significant improvement of the therapy for colon cancer patients, especially in the context of a personalized approach, i.e., in defined subgroups of patients whose tumors carry certain mutations.

NF-κB pathways in the development and progression of colorectal cancer

Nuclear factor-κB (NF-κB) has been widely implicated in the development and progression of cancer. In colorectal cancer (CRC), NF-κB has a key role in cancer-related processes such as cell proliferation, apoptosis, angiogenesis, and metastasis. The role of NF-κB in CRC is complex, owed to the cross talk with other signaling pathways. Although there is sufficient evidence gained from cell lines and animal models that NF-κB is involved in cancer-related processes, because of a lack of studies in human tissue, the clinical evidence of its importance is limited in patients with CRC. This review summarizes evidence relating to how NF-κB is involved in the development and progression of CRC and comments on future work to be carried out.

Bax is involved in the anticancer activity of Velcade in colorectal cancer

Numerous chemotherapeutic agents promote tumor cell death by activating the intrinsic apoptosis signaling pathway. This pathway is regulated by mitochondrial dysfunction, which occurs through an intricate process controlled by complex interactions between B-cell lymphoma 2 (Bcl-2) family members and other cellular proteins. Bcl-2-associated X protein (Bax) is a proapoptotic protein that is an essential component of the intrinsic apoptosis signaling pathway. Patients lacking Bax may be less sensitive to chemotherapy due to an impaired intrinsic apoptosis signaling pathway. The present study demonstrated that Bax expression in colorectal cancer (CRC) tissues was typically increased compared with that in adjacent normal tissues. Furthermore, Bax^-/- HCT-116 cells exhibited reduced proliferation and colony formation ability compared with Bax^+/+ HCT116 cells, although the rate of apoptosis of these cells remained unchanged. However, Bax^-/- HCT116 cells became more resistant to apoptosis when treated with Velcade. The results of the present study provide novel insights into the relevance of Bax expression to the prognosis of CRC.

Management of side effects in the personalized medicine era: chemotherapy-induced peripheral neuropathy

Pharmacogenomics has been establishing itself as a powerful tool to predict individual response to treatment, in order to personalize therapy management; this field has been explored in particular in Oncology. Not only efficacy on the malignant disease has been investigated, but also the possibility to predict adverse effects due to drug administration. Chemotherapy-Induced Neurotoxicity (CIPN) is one of those. This potentially severe and long-lasting/permanent side effect of commonly administered anticancer drugs can severely impair Quality of Life (QoL) in a large cohort of long survival patients. So far, a pharmacogenomics-based approach in CIPN regard has been quite delusive, making a methodological improvement warranted in this field of interest: even the most refined genetic analysis cannot be effective if not applied correctly. Here, we try to devise why it is so, suggesting how THE "bench-side" (Pharmacogenomics) might benefit from and should cooperate with THE "bed-side" (Clinimetrics), in order to make genetic profiling effective if applied to CIPN.

Platinum-induced neurotoxicity and preventive strategies: past, present, and future

Neurotoxicity is a burdensome side effect of platinum-based chemotherapy that prevents administration of the full efficacious dosage and often leads to treatment withdrawal. Peripheral sensory neurotoxicity varies from paresthesia in fingers to ataxic gait, which might be transient or irreversible. Because the number of patients being treated with these neurotoxic agents is still increasing, the need for understanding the pathogenesis of this dramatic side effect is critical. Platinum derivatives, such as cisplatin and carboplatin, harm mainly peripheral nerves and dorsal root ganglia neurons, possibly because of progressive DNA-adduct accumulation and inhibition of DNA repair pathways (e.g., extracellular signal-regulated kinase 1/2, c-Jun N-terminal kinase/stress-activated protein kinase, and p38 mitogen-activated protein kinass), which finally mediate apoptosis. Oxaliplatin, with a completely different pharmacokinetic profile, may also alter calcium-sensitive voltage-gated sodium channel kinetics through a calcium ion immobilization by oxalate residue as a calcium chelator and cause acute neurotoxicity. Polymorphisms in several genes, such as voltage-gated sodium channel genes or genes affecting the activity of pivotal metal transporters (e.g., organic cation transporters, organic cation/carnitine transporters, and some metal transporters, such as the copper transporters, and multidrug resistance-associated proteins), can also influence drug neurotoxicity and treatment response. However, most pharmacogenetics studies need to be elucidated by robust evidence. There are supportive reports about the effectiveness of several neuroprotective agents (e.g., vitamin E, glutathione, amifostine, xaliproden, and venlafaxine), but dose adjustment and/or drug withdrawal seem to be the most frequently used methods in the management of platinum-induced peripheral neurotoxicity. To develop alternative options in the treatment of platinum-induced neuropathy, studies on in vitro models and appropriate trials planning should be integrated into the future design of neuroprotective strategies to find the best patient-oriented solution.

BRAF V600E is a determinant of sensitivity to proteasome inhibitors

A critical step toward defining tailored therapy in patients with cancer is the identification of genetic interactions that may impair-or boost-the efficacy of selected therapeutic approaches. Cell models able to recapitulate combinations of genetic aberrations are important to find drug-genotype interactions poorly affected by the heterogeneous genetics of human tumors. In order to identify novel pharmacogenomic relationships, we employed an isogenic cell panel that reconstructs cancer genetic scenarios. We screened a library of 43 compounds in human hTERT-HME1 epithelial cells in which PTEN or RB1 were silenced in combination with the targeted knockin of cancer-associated mutations in EGFR, KRAS, BRAF, or PIK3CA oncogenes. Statistical analysis and clustering algorithms were applied to display similar drug response profiles and mutation-specific patterns of activity. From the screen, we discovered that proteasome inhibitors show selectivity toward BRAF V600E-mutant cells, irrespective of PTEN or RB1 expression. Preferential targeting of BRAF-mutant cells by proteasome inhibitors was corroborated in a second BRAF V600E isogenic model, as well as in a panel of colorectal cancer cell lines by the use of the proteasome inhibitor carfilzomib. Notably, carfilzomib also showed striking in vivo activity in a BRAF-mutant human colorectal cancer xenograft model. Vulnerability to proteasome inhibitors is dependent on persistent BRAF signaling, because BRAF V600E blockade by PLX4720 reversed sensitivity to carfilzomib in BRAF-mutant colorectal cancer cells. Our findings indicated that proteasome inhibition might represent a valuable targeting strategy in BRAF V600E-mutant colorectal tumors.

Bortezomib stabilizes mitotic cyclins and prevents cell cycle progression via inhibition of UBE2C in colorectal carcinoma

Substantial evidence implicates the ubiquitin-conjugating enzyme E2C (UBE2C) gene, in several human cancers, including colorectal carcinoma (CRC). We therefore investigated the prognostic value of UBE2C alterations in CRC and UBE2C signaling in CRC cell lines. UBE2C protein expression and UBE2C gene copy number were evaluated on clinical samples by immunohistochemistry and fluorescence in situ hybridization in a TMA format. The effect of the proteasome inhibitor bortezomib and small-interfering RNA knockdown was assessed by apoptotic assays and immunoblotting. UBE2C dysregulation was associated with proliferative marker Ki-67, accumulation of cyclin A and B1, and a poor overall survival. UBE2C expression was an independent prognostic marker in early-stage (I and II) CRC. UBE2C depletion resulted in suppression of cellular growth and accumulation of cyclin A and B1. In vitro, bortezomib treatment of CRC cells caused inhibition of cell viability via down-regulation of UBE2C. UBE2C knockdown by bortezomib or transfection with specific small-interfering RNA against UBE2C also caused cells to be arrested at the G2/M level, leading to accumulation of cyclin A and cyclin B1. In vivo, a significant reduction in tumor volume and weight was noted in mice treated with a combination of subtoxic doses of oxaliplatin and bortezomib compared with treatment with oxaliplatin or bortezomib alone. Altogether, our results suggest that UBE2C and the ubiquitin-proteasome pathway may be potential targets for therapeutic intervention in CRC.

Marizomib, a proteasome inhibitor for all seasons: preclinical profile and a framework for clinical trials

The proteasome has emerged as an important clinically relevant target for the treatment of hematologic malignancies. Since the Food and Drug Administration approved the first-in-class proteasome inhibitor bortezomib (Velcade) for the treatment of relapsed/refractory multiple myeloma (MM) and mantle cell lymphoma, it has become clear that new inhibitors are needed that have a better therapeutic ratio, can overcome inherent and acquired bortezomib resistance and exhibit broader anti-cancer activities. Marizomib (NPI-0052; salinosporamide A) is a structurally and pharmacologically unique β-lactone-γ-lactam proteasome inhibitor that may fulfill these unmet needs. The potent and sustained inhibition of all three proteolytic activities of the proteasome by marizomib has inspired extensive preclinical evaluation in a variety of hematologic and solid tumor models, where it is efficacious as a single agent and in combination with biologics, chemotherapeutics and targeted therapeutic agents. Specifically, marizomib has been evaluated in models for multiple myeloma, mantle cell lymphoma, Waldenstrom's macroglobulinemia, chronic and acute lymphocytic leukemia, as well as glioma, colorectal and pancreatic cancer models, and has exhibited synergistic activities in tumor models in combination with bortezomib, the immunomodulatory agent lenalidomide (Revlimid), and various histone deacetylase inhibitors. These and other studies provided the framework for ongoing clinical trials in patients with MM, lymphomas, leukemias and solid tumors, including those who have failed bortezomib treatment, as well as in patients with diagnoses where other proteasome inhibitors have not demonstrated significant efficacy. This review captures the remarkable translational studies and contributions from many collaborators that have advanced marizomib from seabed to bench to bedside.

Chemotherapy-induced peripheral neurotoxicity in the era of pharmacogenomics

Development of advanced and high-throughput methods to study variability in human genes means we can now use pharmacogenomic analysis not only to predict response to treatment but also to assess the toxic action of drugs on normal cells (so-called toxicogenomics). This technological progress could enable us to identify individuals at high and low risk for a given side-effect. Pharmacogenomics could be very useful for stratification of cancer patients at risk of developing chemotherapy-induced peripheral neurotoxicity, one of the most severe and potentially permanent non-haematological side-effects of modern chemotherapeutic agents. However, study data reported so far are inconsistent, which suggests that methodological improvement is needed in clinical trials to obtain reliable results in this clinically relevant area.

[The role of NF-kappaB in colon cancer]

Colon cancer is the 3rd common malignancy and 4th common cause of cancer death in Korea. Recent studies have shown that abnormal inflammatory response plays a critical role in colon carcinogenesis. A striking example of connection between inflammation and cancer is NF-kappaB, in which key regulator of inflammation and immune response is associated with target for colon cancer treatment. Constitutive NF-kappaB expression in colon cancer is 40-80% in vivo as well as in vitro, and the inactivation of IKKbeta subunit can reduce tumor multiplicity. The possible mechanisms by which NF-kappaB can contribute to colon carcinogenesis include the activator of antiapoptotic gene expression, enhanced cell survival and proliferation, regulation of angiogenesis and promotion of metastasis of cancer cells. Recent insights into the role of NF-kappaB involved in colon cancer development as well as their relevance as therapeutic targets are herein discussed.

A Phase Ib pharmacokinetic study of the anti-angiogenic agent CKD-732 used in combination with capecitabine and oxaliplatin (XELOX) in metastatic colorectal cancer patients who progressed on irinotecan-based chemotherapy

BACKGROUND

We conducted a Phase I clinical trial to evaluate the safety, tolerability, and pharmacokinetics (PK) of CKD-732 [6-O-(4-dimethylaminoethoxy) cinnamoyl fumagillol hemioxalate] in combination with capecitabine and oxaliplatin (XELOX) in nine metastatic colorectal cancer patients who had progressed on irinotecan-based chemotherapy.

METHODS

Using a dose-escalation schedule, CKD-732 doses of 2, 5, or 10 mg/m(2)/d were administered twice weekly for 2 weeks, followed by a 1-week rest. Oxaliplatin (130 mg/m(2)) was administered on day 1, and capecitabine (1,000 mg/m(2) twice a day) was orally administered for 14 days of a 3-week cycle.

RESULTS

In the group given the 10 mg/m(2)/d dose, two patients experienced dose limiting toxicities (one had grade 3 nausea, insomnia, and fatigue; the other had grade 3 insomnia). The maximum tolerated dose was 10 mg/m(2)/d, and the clinically recommended dose was 5 mg/m(2)/d for CKD-732 in combination with XELOX. Frequently encountered non-hematological grade 3/4 adverse events included insomnia (22.2%), fatigue (11.1%), sensory neuropathy (11.1%), hyperbilirubinemia (11.1%), and dyspnea (11.1%). The area under the concentration-time curve and maximum concentration of CKD-732 increased in a dose-dependent manner. There were no notable effects of CKD-732 on the PK of capecitabine and oxaliplatin-derived platinum.

CONCLUSION

The Phase II recommended dose of CKD-732 was determined to be 5 mg/m(2)/d, and this dose was safely combined with a conventional dose of capecitabine and oxaliplatin in this patient population. Further studies on the effects of CKD-732 in combination with XELOX and other chemotherapies using a larger study population are warranted.

Targeting NF-kappaB for colorectal cancer

IMPORTANCE OF THE FIELD

Colorectal cancer (CRC) is the second leading cause of cancer death. Progress has been made in the development of chemotherapy for advanced CRC. Targeted therapies against VEGF or EGFR are now commonly used. Many cases show that tolerance develops to such treatments and thus new strategies are required to replace or complement current therapies. The NF-kappaB signaling pathway plays critical roles in physiological and pathological processes, and the relationship between colon cancer development and NF-kappaB is becoming clear.

AREAS COVERED IN THIS REVIEW

We discuss evidence for the participation of activated NF-kappaB in carcinogenesis and consider the possibility of NF-kappaB being a target for CRC treatment.

WHAT THE READER WILL GAIN

NF-kappaB activation might be involved in development of not only colitis-associated cancer, but also sporadic CRC. NF-kappaB activation is associated with hallmarks of cancer. Constitutive NF-kappaB activation is frequently observed in CRC and is associated with angiogenesis and resistance to chemotherapy. Several NF-kappaB inhibitors have proven to be useful.

TAKE HOME MESSAGE

Induction of NF-kappaB activation leads to resistance to chemotherapy and constitutively activated NF-kappaB can often be seen in CRC. Anti-NF-kappaB therapy may rescue many cases of CRC and should be examined further for use as a therapy target.

Neurophysiological, histological and immunohistochemical characterization of bortezomib-induced neuropathy in mice

Bortezomib, a proteasome inhibitor, is an antineoplastic drug to treat multiple myeloma and mantle cell lymphoma. Its most clinically significant adverse event is peripheral sensory neuropathy. Our objective was to characterize the neuropathy induced by bortezomib in a mouse model. Two groups were used; one group received vehicle solution and another bortezomib (1mg/kg/twice/week) for 6weeks (total dose as human schedule). Tests were performed during treatment and for 4weeks post dosing to evaluate electrophysiological, autonomic, pain sensibility and sensory-motor function changes. At the end of treatment and after washout, sciatic and tibial nerves, dorsal ganglia and intraepidermal innervation were analyzed. Bortezomib induced progressive significant decrease of sensory action potential amplitude, mild reduction of sensory velocities without effect in motor conductions. Moreover, it significantly increased pain threshold and sensory-motor impairment at 6weeks. According to these data, histopathological findings shown a mild reduction of myelinated (-10%; p=0.001) and unmyelinated fibers (-27%; p=0.04), mostly involving large and C fibers, with abnormal vesicular inclusion body in unmyelinated axons. Neurons were also involved as shown by immunohistochemical phenotypic switch. After washout, partial recovery was observed in functional, electrophysiological and histological analyses. These results suggest that axon and myelin changes might be secondary to an initial dysfunctional neuronopathy.

NFkappaB signaling in carcinogenesis and as a potential molecular target for cancer therapy

It has become increasingly clear that deregulation of the NFkappaB signaling cascade is a common underlying feature of many human ailments including cancers. The past two decades of intensive research on NFkappaB has identified the basic mechanisms that govern the functioning of this pathway but uncovering the details of why this pathway works differently in different cellular contexts or how it interacts with other signaling pathways remains a challenge. A thorough understanding of these processes is needed to design better and more efficient therapeutic approaches to treat complex diseases like cancer. In this review, we summarize the literature documenting the involvement of NFkappaB in cancer, and then focus on the approaches that are being undertaken to develop NFkappaB inhibitors towards treatment of human cancers.

The ubiquitin-proteasome system as a molecular target in solid tumors: an update on bortezomib

The ubiquitin-proteasome system has become a promising molecular target in cancer therapy due to its critical role in cellular protein degradation, interaction with cell cycle and apoptosis regulation, and unique mechanism of action. Bortezomib (PS-341) is a potent and specific reversible proteasome inhibitor, which has shown strong in vitro antitumor activity as single agent and in combination with other cytotoxic drugs in a broad spectrum of hematological and solid malignancies. In preclinical studies, bortezomib induced apoptosis of malignant cells through the inhibition of NF-|B and stabilization of pro-apoptotic proteins. Bortezomib also promotes chemo- and radiosensitization of malignant cells in vitro and inhibits tumor growth in murine xenograft models. The proteasome has been established as a relevant target in hematologic malignancies and bortezomib has been approved for the treatment of multiple myeloma. This review summarizes recent data from clinical trials in solid tumors.