Motexafin gadolinium and zinc induce oxidative stress responses and apoptosis in B-cell lymphoma lines

Bibliometric analysis of research trends and topic areas in traditional Chinese medicine therapy for lymphoma

CONTEXT

Traditional Chinese Medicine (TCM) is effective as a cancer treatment modality. However, this is the first bibliometric analysis of TCM in lymphoma treatment.

OBJECTIVE

This study explores the current trends and research topics of TCM in treating lymphoma from 2000 to 2023.

MATERIALS AND METHODS

We searched within the Web of Science Core Collection (WoSCC) for publications on TCM in lymphoma treatment, spanning 2000 to 2023. Subsequently, we employed a comprehensive approach utilizing CiteSpace software and VOSviewer to visually analyze research trends, authors, institutions, co-cited references, and keywords.

RESULTS

From January 1, 2000, to August 31, 2023, annual scientific publications on TCM for lymphoma treatment have steadily increased. Among the leading institutions in this field, the Beijing University of Chinese Medicine and the Fujian Medical University occupied the top positions. Regarding the authors, Jun Peng, Jiumao Lin, and Hongwei Chen emerged as the top three contributors. In the co-citation analysis of references, the top three co-cited references were authored by Hanahan D, Elmore S, and Livak KJ with citations numbered 13, 14, and 17, respectively. In particular, keywords reflecting current emerging trends included 'pathway', 'traditional Chinese medicine', 'oxidative stress', and 'macrophage polarization'.

DISCUSSION AND CONCLUSIONS

This bibliometric analysis provides a comprehensive overview of TCM for lymphoma treatment. This analysis identified the predominant trends and research topics in the field. The findings are expected to be of significant value for researchers who focus on TCM in lymphoma treatment, helping them better understand the development of this field.

Recent advances in nano-based drug delivery systems for treatment of liver cancer

Liver cancer is one of the aggressive primary tumors as evident by high rate of incidence and mortality. Conventional treatments (e.g. chemotherapy) suffer from various drawbacks including wide drug distribution, low localized drug concentration, and severe off-site toxicity. Therefore, they cannot satisfy the mounting need for safe and efficient cancer therapeutics, and alternative novel strategies are needed. Nano-based drug delivery systems (NDDSs) are among these novel approaches that can improve the overall therapeutic outcomes. NDDSs are designed to encapsulate drug molecules and target them specifically to liver cancer. Thus, NDDSs can selectively deliver therapeutic agents to the tumor cells and avoid distribution to off-target sites which should improve the safety profile of the active agents. Nonetheless, NDDSs should be well designed, in terms of the preparing materials, nanocarriers structure, and the targeting strategy, in order to accomplish these objectives. This review discusses the latest advances of NDDSs for cancer therapy with emphasis on the aforementioned essential design components. The review also entails the challenges associated with the clinical translation of NDDSs, and the future perspectives towards next-generation NDDSs.

Cellular zinc metabolism and zinc signaling: from biological functions to diseases and therapeutic targets

Zinc metabolism at the cellular level is critical for many biological processes in the body. A key observation is the disruption of cellular homeostasis, often coinciding with disease progression. As an essential factor in maintaining cellular equilibrium, cellular zinc has been increasingly spotlighted in the context of disease development. Extensive research suggests zinc's involvement in promoting malignancy and invasion in cancer cells, despite its low tissue concentration. This has led to a growing body of literature investigating zinc's cellular metabolism, particularly the functions of zinc transporters and storage mechanisms during cancer progression. Zinc transportation is under the control of two major transporter families: SLC30 (ZnT) for the excretion of zinc and SLC39 (ZIP) for the zinc intake. Additionally, the storage of this essential element is predominantly mediated by metallothioneins (MTs). This review consolidates knowledge on the critical functions of cellular zinc signaling and underscores potential molecular pathways linking zinc metabolism to disease progression, with a special focus on cancer. We also compile a summary of clinical trials involving zinc ions. Given the main localization of zinc transporters at the cell membrane, the potential for targeted therapies, including small molecules and monoclonal antibodies, offers promising avenues for future exploration.

Hypoxia promotes the growth and metastasis of ovarian cancer cells by suppressing ferroptosis via upregulating SLC2A12

BACKGROUND

Ovarian cancer has been a worldwide health burden for women and its progression is highly hypoxia-independent. Here, we investigated the exact mechanisms by which hypoxia contributes to the malignant progression of ovarian cancer.

METHOD

MTT, transwell, colony formation, and scratch wound healing assays were carried out for cellular functions. The underlying mechanism by which hypoxia functions was explored by RNA-seq, enrichment analysis, western blotting, qRT-PCR, flow cytometry, ChIP, luciferase reporter, and ELISA. Finally, animal experiments including the xenograft model and tumor metastasis model were constructed to validate the role of SLC2A12 in vivo.

RESULTS

Hypoxia treatment promoted the cell proliferation, mobility, and colony growth abilities of the two ovarian cancer cell lines HO-8910 and A2780. RNA-seq and enrichment analysis showed that SLC2A12 was hyper-expressed under hypoxia condition and it may be related to glutathione and lipid metabolism. Besides, the expression of SLC2A12 was negatively correlated with overall survival. Hypoxia suppressed ferroptosis by SLC2A12 because silencing SLC2A12 declined the cell viability of HO-8910 and A2780 cells under hypoxia conditions, while the ferroptosis inhibitor ferrostatin-1 (Fer-1) breached that result and upregulated the expression of glutathione peroxidase 4 (GPX4). Moreover, hypoxia increased the expression of hypoxia inducible factor 1 A (HIF-1A), and the accumulated HIF-1A binds to hypoxia inducible factor 1 B (HIF1B) to form HIF-1 complex, then promoted the binding of hypoxic response elements (HRE) to SLC2A12 promoter by HIF-1/HRE signal. Subsequently, SLC2A12 regulated glutathione metabolism and in turn inhibited ferroptosis. The animal experiments indicated that silencing SLC2A12 could significantly inhibit tumor growth and metastasis in vivo.

CONCLUSION

Hypoxia promoted ovarian cancer progression by upregulating SLC2A12 and then regulating glutathione metabolism to inhibit ferroptosis.

Identification and validation of a novel cuproptosis-related gene signature in multiple myeloma

Background: Cuproptosis is a newly identified unique copper-triggered modality of mitochondrial cell death, distinct from known death mechanisms such as necroptosis, pyroptosis, and ferroptosis. Multiple myeloma (MM) is a hematologic neoplasm characterized by the malignant proliferation of plasma cells. In the development of MM, almost all patients undergo a relatively benign course from monoclonal gammopathy of undetermined significance (MGUS) to smoldering myeloma (SMM), which further progresses to active myeloma. However, the prognostic value of cuproptosis in MM remains unknown. Method: In this study, we systematically investigated the genetic variants, expression patterns, and prognostic value of cuproptosis-related genes (CRGs) in MM. CRG scores derived from the prognostic model were used to perform the risk stratification of MM patients. We then explored their differences in clinical characteristics and immune patterns and assessed their value in prognosis prediction and treatment response. Nomograms were also developed to improve predictive accuracy and clinical applicability. Finally, we collected MM cell lines and patient samples to validate marker gene expression by quantitative real-time PCR (qRT-PCR). Results: The evolution from MGUS and SMM to MM was also accompanied by differences in the CRG expression profile. Then, a well-performing cuproptosis-related risk model was developed to predict prognosis in MM and was validated in two external cohorts. The high-risk group exhibited higher clinical risk indicators. Cox regression analyses showed that the model was an independent prognostic predictor in MM. Patients in the high-risk group had significantly lower survival rates than those in the low-risk group (p < 0.001). Meanwhile, CRG scores were significantly correlated with immune infiltration, stemness index and immunotherapy sensitivity. We further revealed the close association between CRG scores and mitochondrial metabolism. Subsequently, the prediction nomogram showed good predictive power and calibration. Finally, the prognostic CRGs were further validated by qRT-PCR in vitro. Conclusion: CRGs were closely related to the immune pattern and self-renewal biology of cancer cells in MM. This prognostic model provided a new perspective for the risk stratification and treatment response prediction of MM patients.

Impact of the glutathione synthesis pathway on sulfasalazine-treated endometrial cancer

Glutathione is an antioxidant that has an important role in chemotherapeutic drug resistance in cancer. Cysteine is synthesized from cystine and is transported into the cell via the xCT antiporter. Another pathway for synthesizing cysteine involves intracellular methionine. We determined whether targeting the xCT represents a promising strategy for the treatment of endometrial cancer and identified factors that predict efficacy of this treatment strategy. In uterine serous carcinoma (USC) cell lines, the combination of cisplatin and the xCT inhibitor, sulfasalazine, significantly inhibited cell growth compared with single-agent cisplatin or sulfasalazine. Sulfasalazine treatment significantly decreased intracellular glutathione levels and induced apoptosis when combined with cisplatin in USC cell lines. On the one hand, the effectiveness of combined cisplatin and sulfasalazine was not evident in endometrioid carcinoma. USC cell lines exhibited increased expression of xCT and decreased expression of cystathionine gamma lyase (CGL), which is an enzyme involved in the synthesis of cysteine from methionine. On the other hand, endometrioid carcinoma cell lines exhibited increased CGL expression or decreased xCT expression. These findings suggest that using a glutathione synthesis pathway-based approach for selecting subjects for sulfasalazine treatment may be an effective strategy for circumventing glutathione-related chemotherapeutic drug resistance in endometrial carcinoma.

xCT inhibitor sulfasalazine depletes paclitaxel-resistant tumor cells through ferroptosis in uterine serous carcinoma

Glutathione (GSH) is a primary antioxidant that protects cells against reactive oxygen species (ROS), and high levels of GSH promote cancer cell survival and resistance to chemotherapy. The glutamine transporter xCT is essential for the intracellular synthesis of GSH, whereby xCT determines the intracellular redox balance. However, whether xCT inhibition can overcome GSH-mediated resistance to chemotherapeutic agents in uterine serous carcinoma (USC) remains unclear. Thus, the present study investigated the effect of the xCT inhibitor, sulfasalazine (SAS) on cytotoxicity in paclitaxel-sensitive and -resistant USC cell lines. The molecular mechanism by which SAS induces ferroptotic cell death in paclitaxel-resistant cells was assessed. The results of the cytotoxicity assay demonstrated that SAS was more cytotoxic in paclitaxel-resistant cells compared with in -sensitive cells; however, paclitaxel cytotoxicity was not enhanced in either of the USC cell lines. Immunoblotting analysis and the cell death assays performed using ferroptosis inhibitors indicated that SAS-mediated cell death was induced through ferroptosis, and not apoptosis, in paclitaxel-resistant cells. Furthermore, ROS production was increased in paclitaxel-resistant but not in -sensitive cells, even at low SAS concentration, and JNK was activated, which is a downstream target in the Ras signaling pathway. Knockdown of JNK reversed the inhibitory effect of SAS on cell proliferation and cell death. The synthetic lethal interaction between ROS accumulation and Ras effector JNK activation may be critical for enhancing the sensitivity to ferroptotic cell death mediated by xCT inhibitor, SAS. Taken together, the results of the present study suggest that xCT inhibition may be an effective treatment for patients with recurrent paclitaxel-resistant USC.

Micronutrients in autoimmune diseases: possible therapeutic benefits of zinc and vitamin D

A functional immune system is essential for healthy life. This is achieved by the coordinate activation and interaction of different immune cells. One should be aware that activation of the immune response is as important as its deactivation when the pathogens are cleared, as otherwise host tissue can be damaged up to life-threatening levels. Autoimmune diseases (AID) represent a phenomenon of immune cells attacking host cells and tissue. Five to eight percent of the world's population are currently affected by 80-100 AID. In recent years, the incidence has been constantly increasing, reaching alarmingly high numbers particularly for type 1 diabetes mellitus, Crohn's disease, rheumatoid arthritis, Sjogren's syndrome and multiple sclerosis. This indicates a higher societal burden of AID for the future. This article provides an overview of general concepts of triggers and underlying mechanisms leading to self-destruction. Lately, several original concepts of disease etiology were revised, and there is a variety of hypotheses on triggers, underlying mechanisms and preventive actions. This article concentrates on the importance of nutrition, especially zinc and vitamin D, for balancing the immune function. Homespun nutritional remedies seem to reenter today's therapeutic strategies. Current treatment approaches are largely symptomatic or suppress the immune system. However, recent studies reveal significant benefits of nutrition-related therapeutic approaches including prevention and treatment of established disease, which offer a cost-efficient and trigger-unspecific alternative addressing balancing rather than suppression of the immune system. Zinc and vitamin D are currently the best studied and most promising candidates for therapeutic intervention.

Inhibition of JAK2/STAT3 Signaling Pathway Suppresses Proliferation of Burkitt's Lymphoma Raji Cells via Cell Cycle Progression, Apoptosis, and Oxidative Stress by Modulating HSP70

Background

The aim of this study was to investigate the effect of the JAK2/STAT3 pathway on the proliferation, cell cycle distribution, apoptosis, and oxidative stress of Raji cells via regulating HSP70 expression.

Material/Methods

Raji cells were divided into Blank, HSP70 siRNA, NC siRNA, AG490 (a JAK2/STAT3 signaling pathway inhibitor), and HSP70 siRNA + rh JAK2 (recombinant human JAK2) groups. HSP70 expression was detected by quantitative real-time reverse transcription-PCR (qRT-PCR); the expression levels of HSP70 and JAK2/STAT3 pathway-related proteins were evaluated by Western blotting; cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays; cell cycle distribution was observed by flow cytometry; cell apoptosis was tested by Annexin V-FITC/PI and Hoechst 33342/PI staining; reactive oxygen species (ROS) production was measured by dichloro-dihydro-fluorescein diacetate (DCFH-DA) assays; and MDA content and SOD and GSH-Px activities were determined using detection kits.

Results

AG490 obviously down-regulated HSP70 expression, inhibited proliferation, induced cell cycle arrest at the G0/G1 phase, and promoted apoptosis in Raji cells; these effects were similar to the effects of HSP70 siRNA. Furthermore, ROS production and MDA content were increased in Raji cells treated with HSP70 siRNA or AG490, while SOD and GSH-Px activities were reduced. Raji cells in the HSP70 siRNA + rh JAK2 group did not significantly differ from those in the Blank group in regards to proliferation, cell cycle, apoptosis, and oxidative stress.

Conclusions

Blocking the JAK2/STAT3 signaling pathway may inhibit proliferation, induce cell cycle arrest, and promote oxidative stress and apoptosis in Raji cells via the down-regulation of HSP70.

Triggering apoptosis in cancer cells with an analogue of cribrostatin 6 that elevates intracellular ROS

Elevation of reactive oxygen species (ROS) is both a consequence and driver of the upregulated metabolism and proliferation of transformed cells. The resulting increase in oxidative stress is postulated to saturate the cellular antioxidant machinery, leaving cancer cells susceptible to agents that further elevate their intracellular oxidative stress. Several small molecules, including the marine natural product cribrostatin 6, have been demonstrated to trigger apoptosis in cancer cells by increasing intracellular ROS. Here, we report the modular synthesis of a series of cribrostatin 6 derivatives, and assessment of their activity in a number of cell lines. We establish that placing a phenyl ring on carbon 8 of cribrostatin 6 leads to increased potency, and observe a window of selectivity towards cancer cells. The mechanism of activity of this more potent analogue is assessed and demonstrated to induce apoptosis in cancer cells by increasing ROS. Our results demonstrate the potential for targeting tumors with molecules that enhance intracellular oxidative stress.

Novel biomolecule lycopene-reduced graphene oxide-silver nanoparticle enhances apoptotic potential of trichostatin A in human ovarian cancer cells (SKOV3)

Background

Recently, there has been much interest in the field of nanomedicine to improve prevention, diagnosis, and treatment. Combination therapy seems to be most effective when two different molecules that work by different mechanisms are combined at low dose, thereby decreasing the possibility of drug resistance and occurrence of unbearable side effects. Based on this consideration, the study was designed to investigate the combination effect of reduced graphene oxide-silver nanoparticles (rGO-AgNPs) and trichostatin A (TSA) in human ovarian cancer cells (SKOV3).

Methods

The rGO-AgNPs were synthesized using a biomolecule called lycopene, and the resultant product was characterized by various analytical techniques. The combination effect of rGO-Ag and TSA was investigated in SKOV3 cells using various cellular assays such as cell viability, cytotoxicity, and immunofluorescence analysis.

Results

AgNPs were uniformly distributed on the surface of graphene sheet with an average size between 10 and 50 nm. rGO-Ag and TSA were found to inhibit cell viability in a dose-dependent manner. The combination of rGO-Ag and TSA at low concentration showed a significant effect on cell viability, and increased cytotoxicity by increasing the level of malondialdehyde and decreasing the level of glutathione, and also causing mitochondrial dysfunction. Furthermore, the combination of rGO-Ag and TSA had a more pronounced effect on DNA fragmentation and double-strand breaks, and eventually induced apoptosis.

Conclusion

This study is the first to report that the combination of rGO-Ag and TSA can cause potential cytotoxicity and also induce significantly greater cell death compared to either rGO-Ag alone or TSA alone in SKOV3 cells by various mechanisms including reactive oxygen species generation, mitochondrial dysfunction, and DNA damage. Therefore, this combination chemotherapy could be possibly used in advanced cancers that are not suitable for radiation therapy or surgical treatment and facilitate overcoming tumor resistance and disease progression.

Targeting Antioxidant Pathways with Ferrocenylated N-Heterocyclic Carbene Supported Gold(I) Complexes in A549 Lung Cancer Cells

Ferrocenylated-Au(i) carbenes were designed, synthesized, and studied for their ability to generate reactive oxygen species and target antioxidant pathways via multiple mechanisms.

Ferrocene containing N-heterocyclic carbene (NHC) ligated gold(i) complexes of the type [Au(NHC)₂]⁺ were prepared and found to be capable of regulating the formation of reactive oxygen species (ROS) via multiple mechanisms. Single crystal X-ray analysis of bis(1-(ferrocenylmethyl)-3-mesitylimidazol-2-ylidene)-gold(i) chloride (5) and bis(1,3-di(ferrocenylmethyl)imidazol-2-ylidene)-gold(i) chloride (6) revealed a quasi-linear geometry around the gold(i) centers (i.e., the C–Au–C bond angle were measured to be ∼177° and all the Au–C_carbene bonds distances were in the range of 2.00 (7)–2.03 (1) Å). A series of cell studies indicated that cell proliferation inhibition and ROS generation were directly proportional to the amount of ferrocene contained within the [Au(NHC)₂]⁺ complexes (IC₅₀ of 6 < 5 < bis(1-benzyl-3-mesitylimidazol-2-ylidene)-gold(i) chloride (4)). Complexes 4–6 were also confirmed to inhibit thioredoxin reductase as inferred from lipoate reduction assays and increased chelatable intracellular zinc concentrations. RNA microarray gene expression assays revealed that 6 induces endoplasmic reticulum stress response pathways as a result of ROS increase.

TrxR1 as a potent regulator of the Nrf2-Keap1 response system

SIGNIFICANCE

All cells must maintain a balance between oxidants and reductants, while allowing for fluctuations in redox states triggered by signaling, altered metabolic flow, or extracellular stimuli. Furthermore, they must be able to rapidly sense and react to various challenges that would disrupt the redox homeostasis.

RECENT ADVANCES

Many studies have identified Keap1 as a key sensor for oxidative or electrophilic stress, with modification of Keap1 by oxidation or electrophiles triggering Nrf2-mediated transcriptional induction of enzymes supporting reductive and detoxification pathways. However, additional mechanisms for Nrf2 regulation are likely to exist upstream of, or in parallel with, Keap1.

CRITICAL ISSUES

Here, we propose that the mammalian selenoprotein thioredoxin reductase 1 (TrxR1) is a potent regulator of Nrf2. A high chemical reactivity of TrxR1 and its vital role for the thioredoxin (Trx) system distinguishes TrxR1 as a prime target for electrophilic challenges. Chemical modification of the selenocysteine (Sec) in TrxR1 by electrophiles leads to rapid inhibition of thioredoxin disulfide reductase activity, often combined with induction of NADPH oxidase activity of the derivatized enzyme, thereby affecting many downstream redox pathways. The notion of TrxR1 as a regulator of Nrf2 is supported by many publications on effects in human cells of selenium deficiency, oxidative stress or electrophile exposure, as well as the phenotypes of genetic mouse models.

FUTURE DIRECTIONS

Investigation of the role of TrxR1 as a regulator of Nrf2 activation will facilitate further studies of redox control in diverse cells and tissues of mammals, and possibly also in animals of other classes.

Bis-arylidene oxindole-betulinic Acid conjugate: a fluorescent cancer cell detector with potent anticancer activity

Molecules offering simultaneous detection and killing of cancer cells are advantageous. Hybrid of cancer cell-selective, ROS generator betulinic acid and bis-arylidene oxindole with amino propyl-linker is developed. With intrinsic fluorescence, the molecule exhibited cancer cell-specific residence. Further, it generated ROS, triggered apoptosis, and exhibited potent cytotoxicity in cancer cells selectively. We demonstrate the first example and use of isatins as betulinic acid conjugate for selective detection of cancer and subsequent killing of cancer cells via apoptosis.

Phase 1/2 trials of Temozolomide, Motexafin Gadolinium, and 60-Gy fractionated radiation for newly diagnosed supratentorial glioblastoma multiforme: final results of RTOG 0513

PURPOSE

The purpose of phase 1 was to determine the maximum tolerated dose (MTD) of motexafin gadolinium (MGd) given concurrently with temozolomide (TMZ) and radiation therapy (RT) in patients with newly diagnosed supratentorial glioblastoma multiforme (GBM). Phase 2 determined whether this combination improved overall survival (OS) and progression-free survival (PFS) in GBM recursive partitioning analysis class III to V patients compared to therapies for recently published historical controls.

METHODS AND MATERIALS

Dose escalation in phase 1 progressed through 3 cohorts until 2 of 6 patients experienced dose-limiting toxicity or a dose of 5 mg/kg was reached. Once MTD was established, a 1-sided 1-sample log-rank test at significance level of .1 had 85% power to detect a median survival difference (13.69 vs 18.48 months) with 60 deaths over a 12-month accrual period and an additional 18 months of follow-up. OS and PFS were estimated using the Kaplan-Meier method.

RESULTS

In phase 1, 24 patients were enrolled. The MTD established was 5 mg/kg, given intravenously 5 days a week for the first 10 RT fractions, then 3 times a week for the duration of RT. The 7 patients enrolled in the third dose level and the 94 enrolled in phase 2 received this dose. Of these 101 patients, 87 were eligible and evaluable. Median survival time was 15.6 months (95% confidence interval [CI]: 12.9-17.6 months), not significantly different from that of the historical control (P=.36). Median PFS was 7.6 months (95% CI: 5.7-9.6 months). One patient (1%) experienced a grade 5 adverse event possibly related to therapy during the concurrent phase, and none experience toxicity during adjuvant TMZ therapy.

CONCLUSIONS

Treatment was well tolerated, but median OS did not reach improvement specified by protocol compared to historical control, indicating that the combination of standard RT with TMZ and MGd did not achieve a significant survival advantage.

Inflammation, DAMPs, tumor development, and progression: a vicious circle orchestrated by redox signaling

SIGNIFICANCE

Increasing evidence indicates that cancer development and progression are promoted by the joint action of redox distress and inflammation, supporting the potential impact of therapies aimed at restoring the redox homeostasis and fighting inflammation.

RECENT ADVANCES

Most of the literature of the last 40 years converges to the view that continuous oxidative stress and chronic inflammation sustain each other, leads to transformation of a normal cell to a neoplastic cell, and promotes tumor progression. Some recent findings, however, support an alternative model whereby the increased production of reactive oxygen species (ROS) is an attempt to defend more than a pathogenetic factor in cancer. Rather, tumor development and progression may be promoted by an excess of antioxidants, induced in both transformed cells and recruited inflammatory cells as an adaptive response to ROS.

CRITICAL ISSUES

Although the link among redox stress, chronic inflammation, and cancer is widely recognized, the underlying mechanisms are far to be understood. The redox unbalance of the microenvironment is likely to modulate the bioactivity of damage-associated molecular pattern molecules such as HMGB1, which are released by stressed tissues and play pleiotropic functions on tumor and inflammatory cells, but how this occur, and the relevant consequences, are still unclear.

FUTURE DIRECTIONS

In vivo measurement of cell redox status is an important challenge for future investigations. The improvement of the methodologies for ROS and antioxidant detection will allow a better understanding of the redox-related events in the tumor microenvironment with tremendous application potential in the development of rational combination therapies for cancer treatment.

Expression of KLF4 is a predictive marker for survival in pediatric Burkitt lymphoma

Krüppel-like factor 4 (KLF4) is expressed in a variety of tissues with diverse physiological functions and activities. KLF4 can also function as a tumor suppressor or an oncogene, depending on the cellular context. Its role in hematological malignancies is controversial. This study examined the expression levels of KLF4 by immunohistochemistry in 73 pediatric non-Hodgkin lymphomas (NHLs) in a tissue microarray and also on several B-NHL cell lines. Elevated levels of KLF4 expression were detected in 66% of lymphoma cases and were more frequent in the Burkitt lymphoma (p = 0.05) subtype. There was a significant predictive power for outcome with low KLF4 expression, predicting a favorable overall survival compared to high levels. Multivariate analyses confirmed the association of KLF4 expression with unfavorable overall survival (p < 0.005). These findings were consistent with analyses in existing NHL microarray datasets. The present findings revealed that KLF4 is overexpressed in Burkitt pediatric lymphoma and is a potential biomarker for inferior overall survival.

Motexafin gadolinium: a novel radiosensitizer for brain tumors

Despite advances in the field of oncology, progress for patients with brain metastases and most primary brain tumors has been slow. New efforts to enhance the therapeutic index of radiation therapy are under way, including the use of radiosensitizers. Motexafin gadolinium (Xcytrin) is one such novel agent with several unique properties that enhance the cytotoxic potential of radiation therapy, as well as several chemotherapeutic agents, and possibly has independent cytotoxicity in certain lymphoid malignancies. Motexafin gadolinium is very well tolerated with tumor specific uptake. The rationale for the use of this drug as well as its current and future role as a radiation enhancer in the management of brain tumors is reviewed.

Role of glutathione in cancer progression and chemoresistance

Glutathione (GSH) plays an important role in a multitude of cellular processes, including cell differentiation, proliferation, and apoptosis, and disturbances in GSH homeostasis are involved in the etiology and progression of many human diseases including cancer. While GSH deficiency, or a decrease in the GSH/glutathione disulphide (GSSG) ratio, leads to an increased susceptibility to oxidative stress implicated in the progression of cancer, elevated GSH levels increase the antioxidant capacity and the resistance to oxidative stress as observed in many cancer cells. The present review highlights the role of GSH and related cytoprotective effects in the susceptibility to carcinogenesis and in the sensitivity of tumors to the cytotoxic effects of anticancer agents.

Texaphyrins and water-soluble zinc(II) ionophores: development, mechanism of anticancer activity, and synergistic effects

Texaphyrins, first prepared by Sessler and coworkers in the 1980s, represent early examples of expanded porphyrins. This class of pentaaza, oligopyrrolic macrocycles demonstrates excellent tumor localization and metal-chelating properties. In biological milieus, texaphyrins act as redox mediators and are able to produce reactive oxygen species. Furthermore, texaphyrins have been shown to upregulate zinc in vivo, an important feature that inspired us to develop new zinc ionophores that might allow the same function to be elicited but via a simpler chemical means. In this review, the basic properties of texaphyrins and the zinc ionophores they helped spawn will be discussed in the cadre of developing an understanding that could lead to the preparation of new, redox-active anticancer agents.

Motexafin-gadolinium and involved field radiation therapy for intrinsic pontine glioma of childhood: a children's oncology group phase 2 study

PURPOSE

To evaluate the effects on 1-year event-free survival (EFS) and overall survival (OS) of combining motexafin and gadolinium (MGd), a potent radiosensitizer, with daily fractionated radiation therapy in children with newly diagnosed intrinsic pontine gliomas.

METHODS AND MATERIALS

Patients with newly diagnosed intrinsic pontine glioma were treated with MGd daily for 5 consecutive days each week, for a total of 30 doses. Patients received a 5- to 10-min intravenous bolus of MGd, 4.4 mg/kg/day, given 2 to 5 h prior to standard dose irradiation. Radiation therapy was administered at a daily dose of 1.8 Gy for 30 treatments over 6 weeks. The total dose was 54 Gy.

RESULTS

Sixty eligible children received MGd daily, concurrent with 6 weeks of radiation therapy. The estimated 1-year EFS was 18%±5%, and the estimated 1-year OS was 53%±6.5%. The most common grade 3 to 4 toxicities were lymphopenia, transient elevation of liver transaminases, and hypertension.

CONCLUSIONS

Compared to historical controls, the addition of MGd to a standard 6-week course of radiation did not improve the survival of pediatric patients with newly diagnosed intrinsic pontine gliomas.

Gene-expression analysis of early- and late-maturation-stage rat enamel organ

Enamel maturation is a dynamic process that involves high rates of mineral acquisition, associated fluctuations in extracellular pH, and resorption of extracellular enamel proteins. During maturation, ameloblasts change from having a tall, thin, and highly polarized organization, characteristic of the secretory stage, to having a low columnar and widened morphology in the maturation stage. To identify potential differences in gene expression throughout maturation, we obtained enamel organ epithelial cells derived from the early- and late-maturation stages of rat incisor and analyzed the global gene-expression profiles at each stage. Sixty-three candidate genes were identified as having potential roles in the maturation process. Quantitative PCR was used to confirm the results of this genome-wide analysis in a subset of genes. Transcripts enriched during late maturation (n = 38) included those associated with lysosomal activity, solute carrier transport, and calcium signaling. Also up-regulated were transcripts involved in cellular responses to oxidative stress, proton transport, cell death, and the immune system. Transcripts down-regulated during the late maturation stage (n =25) included those with functions related to cell adhesion, cell signaling, and T-cell activation. These results indicate that ameloblasts undergo widespread molecular changes during the maturation stage of amelogenesis and hence provide a basis for future functional investigations into the mechanistic basis of enamel mineralization.

The cystine/cysteine cycle and GSH are independent and crucial antioxidant systems in malignant melanoma cells and represent druggable targets

AIMS

Cancer chemoresistance is often due to upregulation of antioxidant systems. Therapeutic targeting of these systems is however hampered by their redundancy. Here, we have performed a functional dissection of the antioxidant systems in different melanoma cases aimed at the identification of the most effective redox active drug.

RESULTS

We have identified two crucial antioxidant mechanisms: glutathione (GSH), the major intracellular redox buffer, and the cystine/cysteine cycle, which switches the extracellular redox state from an oxidized to a reduced state. The two mechanisms are independent in melanoma cells and may be substitutes for each other, but targeting both of them is lethal. Exposure to the pro-oxidant compound As(2)O(3) induces an antioxidant response. However, while in these cells the intracellular redox balance remains almost unaffected, a reduced environment is generated extracellularly. GSH depletion by buthioninesulfoximine (BSO), or cystine/cysteine cycle inhibition by (S)-4-carboxyphenylglycine (sCPG), enhanced the sensitivity to As(2)O(3). Remarkably, sCPG also prevented the remodeling of the microenvironment redox state.

INNOVATION

We propose that the definition of the prevalent antioxidant system(s) in tumors is crucial for the design of tailored therapies involving redox-directed drugs in association with pro-oxidant drugs.

CONCLUSION

In melanoma cells, BSO is the best enhancer of As(2)O(3) sensitivity. However, since the strong remodeling of the microenvironmental redox state caused by As(2)O(3) may promote tumor progression, the concomitant use of cystine/cysteine cycle blockers is recommended.

Docetaxel-mediated apoptosis in myeloid progenitor TF-1 cells is mitigated by zinc: potential implication for prostate cancer therapy

BACKGROUND

Docetaxel-based combination chemotherapy is approved by the FDA for the treatment of metastatic castration-resistant prostate cancer. Unfortunately, docetaxel's efficacy is significantly limited by its considerable toxicity on hematopoietic progenitor cells, thus necessitating dose reduction or even discontinuation of the chemotherapy. Induction of pre-mitotic arrest protects cells against docetaxel-mediated toxicity and affords therapeutic opportunities.

METHODS

Cell cycle progression was examined by propidium iodide staining. Zinc uptake was determined by FluoZin-3 AM staining. Apoptotic DNA fragmentation was detected using APO-BRDU kit.

RESULTS

In the course of our current work, we treated the myeloid progenitor TF-1 cells and the castration-resistant PC-3 and DU-145 prostate cancer cells with physiologically relevant concentrations of zinc. In doing so, we were able to prevent docetaxel-mediated mitotic arrest in zinc accumulating myeloid progenitor TF-1 cells but not in castration-resistant PC-3 and DU-145 prostate cancer cells. Moreover, pre-treatment with zinc abolished docetaxel-induced apoptosis in TF-1 cells, whereas such treatment had no effect on apoptosis in PC-3 and DU-145 prostate cancer cells.

CONCLUSIONS

Our results suggest that zinc can protect myeloid progenitor cells against docetaxel-induced toxicity without compromising the drug's anti-tumor activity.

Crown ether functionalized texaphyrin monomers and dimers

The synthesis and characterization of two 18-crown-6 functionalized analogues of an extensively studied gadolinium texaphyrin derivative, motexafin gadolinium (1, MGd), are reported. These are the monomeric and dimeric species, compounds 2 and 3, respectively. Both crown ether functionalized species proved to be stable at physiological pH and revealed distinct shifts in the UV spectrum when treated with sodium-, potassium-, ammonium- or zinc(II)-salts. Zinc(II) is believed to play a major role regulating apoptosis mechanisms in cancerous cells. Therefore, cytotoxicity studies of 2 and 3 were carried out using Ramos cell lines in the presence and absence of zinc(II).

Safety and feasibility of motexafin gadolinium administration with whole brain radiation therapy and stereotactic radiosurgery boost in the treatment of ≤ 6 brain metastases: a multi-institutional phase II trial

To determine the safety, tolerability, and report on secondary efficacy endpoints of motexafin gadolinium (MGd) in combination with whole-brain radiotherapy (WBRT) and stereotactic radiosurgery (SRS) for patients with ≤ 6 brain metastases. We conducted an international study of WBRT (37.5 Gy in 15 fractions) and SRS (15-21 Gy) with the addition of MGd (5 mg/kg preceding each fraction beginning week 2). The primary endpoint was to evaluate the rate of irreversible grade 3 or any grade ≥ 4 neurotoxicity and establish feasibility in preparation for a phase III trial. Sixty-five patients were enrolled from 14 institutions, of which 45 (69%) received SRS with MGd as intended and were available for evaluation. Grade ≥ 3 neurotoxicity attributable to radiation therapy within 3 months of SRS was seen in 2 patients (4.4%), including generalized weakness and radionecrosis requiring surgical management. Immediately following the course of MGd plus WBRT, new brain metastases were detected in 11 patients (24.4%) at the time of the SRS treatment planning MRI. The actuarial incidence of neurologic progression at 6 months and 1 year was 17 and 20%, respectively. The median investigator-determined neurologic progression free survival and overall survival times were 8 (95% CI: 5-14) and 9 months (95% CI: 6-not reached), respectively. We observed a low rate of neurotoxicity, demonstrating that the addition of MGd does not increase the incidence or severity of neurologic complications from WBRT with SRS boost.

Acute cytokine-mediated downregulation of the zinc transporter ZnT8 alters pancreatic beta-cell function

Genetic studies suggest that Zn transporters such as ZnT8 play a role in insulin secretion by pancreatic beta-cells; however, little is known about the dynamic roles of Zn trafficking pathways on beta-cell physiology. To test the acute effects of the inflammatory cytokines interleukin 1 beta (IL1 beta) and tumor necrosis factor alpha (TNFalpha) on Zn homeostasis, the mRNA expression profile of Zn transporters of the ZnT and ZIP families was examined. Exposure of MIN6 cells or primary murine islets to IL1 beta or TNFalpha altered the mRNA expression profile of Zn transporters; most notable was decreased ZnT8 mRNA levels. siRNA-mediated gene knockdown was used to examine the effects of decreased ZnT8 expression in primary dispersed murine islet cells from C57/BL6 mice and MIN6 cells. ZnT8 knockdown in these murine islets led to reduced glucose stimulated insulin secretion without altering the total cellular insulin content or cell viability at normal or supraphysiological Zn concentrations. The labile Zn content determined by flow cytometry after loading with the Zn-specific sensor FluoZin-3 AM was decreased in MIN6 cells following ZnT8 knockdown or IL1 beta treatment. These results suggest that an acute decrease in ZnT8 levels impairs beta-cell function and Zn homeostasis, and may contribute to inflammatory cytokine-induced alterations in beta-cell function.

Survivin mediates prostate cell protection by HIF-1alpha against zinc toxicity

BACKGROUND

The prostate contains extremely high concentrations of zinc, but survives and grows without apparent injury. This begs the question as to how prostate cells avoid the toxic effects of zinc. In a previous study, the authors found that; HIF-1alpha is expressed concomitantly with the accumulation of zinc in the epithelial cells of normal rat prostates, the zinc ion stabilizes HIF-1alpha in prostate cells, and that HIF-1alpha protects prostate cells from zinc toxicity. In the present study, the authors addressed the mechanism responsible for the protective effect of HIF-1alpha in a high zinc environment.

METHODS

Immunofluorescent staining, immunoblotting, reverse transcription-polymerase chain reaction, reporter assay, and cell cycle analysis.

RESULTS

Survivin was induced by ZnCl(2) in a HIF-1 dependent manner in both DU-145 and PNT2 prostate cells. Furthermore, HIF-1 induced survivin expression at the transcriptional level and the induction of survivin was abolished by HIF-1alpha knock-down. In addition, HIF-1-dependent survivin overexpression promoted prostrate cell survival and prevented cell arrest in the presence of high zinc concentrations, and si-survivin transfected cells under zinc rich conditions contained markedly higher levels of cleaved caspase-9 and PARP than si-con transfected cells. Finally, survivin expression patterns well matched rat prostate proliferation statuses.

CONCLUSION

Under zinc rich conditions, prostate epithelial cells HIF-1-dependently express survivin, which promotes prostate cell proliferation, and prevents apoptosis and cell cycle arrest. Accordingly, the HIF-1alpha-survivin pathway appears to facilitate prostate cell survival and growth in zinc rich environments, and this pathway could be a therapeutic target for the treatment of prostate hyperplasia.

N-Acetylcysteine interacts with copper to generate hydrogen peroxide and selectively induce cancer cell death

A variety of metal-binding compounds have been found to exert anti-cancer activity. We postulated that N-acetylcysteine (NAC), which is a membrane-permeable metal-binding compound, might have anti-cancer activity in the presence of metals. We found that NAC/Cu(II) significantly alters growth and induces apoptosis in human cancer lines, yet NAC/Zn(II) and NAC/Fe(III) do not. We further confirmed that this cytotoxicity of NAC/Cu(II) is attributed to reactive oxygen species (ROS). These findings indicate that the combination of Cu(II) and thiols generates cytotoxic ROS that induce apoptosis in cancer cells. They also indicate a fourth class of anti-neoplastic metal-binding compounds, the "ROS generators".

Metal ionophores - an emerging class of anticancer drugs

Compounds that bind metals such as copper and zinc have many biological activities, including the ability to induce apoptosis in cancer cells. Although some of these compounds have been considered to act as chelators of metals, decreasing their bioavailability, others increase intracellular metal concentrations. We review recent work regarding the recognition of the biological effects of metal ionophores with different structures, particularly with regard to their actions upon cancer cells focusing on dithiocarbamates, pyrithione, and the 8-hydroxyquinoline derivative, clioquinol. We provide a biologically based classification of metal-binding compounds that allows an experimental distinction between chelators and ionophores that can be readily used by biologists, which may lead to further study and classification of metal-binding drugs. Metal ionophores may kill cancer cells by a number of mechanisms, including lysosomal disruption and proteasome inhibition, and likely others. Because some of these compounds have been safely administered to animals and humans, they have the potential to become clinically useful anticancer agents.

Modulation of cell surface protein free thiols: a potential novel mechanism of action of the sesquiterpene lactone parthenolide

Background

There has been much interest in targeting intracellular redox pathways as a therapeutic approach for cancer. Given recent data to suggest that the redox status of extracellular protein thiol groups (i.e. exofacial thiols) effects cell behavior, we hypothesized that redox active anti-cancer agents would modulate exofacial protein thiols.

Methodology/Principal Findings

To test this hypothesis, we used the sesquiterpene lactone parthenolide, a known anti-cancer agent. Using flow cytometry, and western blotting to label free thiols with Alexa Fluor 633 C₅ maleimide dye and N-(biotinoyl)-N-(iodoacetyl) ethylendiamine (BIAM), respectively, we show that parthenolide decreases the level of free exofacial thiols on Granta mantle lymphoma cells. In addition, we used immuno-precipitation techniques to identify the central redox regulator thioredoxin, as one of the surface protein thiol targets modified by parthenolide. To examine the functional role of parthenolide induced surface protein thiol modification, we pretreated Granta cells with cell impermeable glutathione (GSH), prior to exposure to parthenolide, and showed that GSH pretreatment; (a) inhibited the interaction of parthenolide with exofacial thiols; (b) inhibited parthenolide mediated activation of JNK and inhibition of NFκB, two well established mechanisms of parthenolide activity and; (c) blocked the cytotoxic activity of parthenolide. That GSH had no effect on the parthenolide induced generation of intracellular reactive oxygen species supports the fact that GSH had no effect on intracellular redox. Together these data support the likelihood that GSH inhibits the effect of parthenolide on JNK, NFκB and cell death through its direct inhibition of parthenolide's modulation of exofacial thiols.

Conclusions/Significance

Based on these data, we postulate that one component of parthenolide's anti-lymphoma activity derives from its ability to modify the redox state of critical exofacial thiols. Further, we propose that cancer cell exofacial thiols may be important and novel targets for therapy.

The novel expanded porphyrin, motexafin gadolinium, combined with [90Y]ibritumomab tiuxetan for relapsed/refractory non-Hodgkin's lymphoma: preclinical findings and results of a phase I trial

PURPOSE

Therapeutic strategies to enhance the efficacy of radioimmunotherapy have not been explored. Motexafin gadolinium is a novel anticancer agent that targets redox-dependent pathways and enhances sensitivity of tumor cells to ionizing radiation.

EXPERIMENTAL DESIGN

We did preclinical studies examining motexafin gadolinium combined with rituximab and/or radiation in lymphoma cells. We subsequently completed a phase I clinical trial combining escalating doses of motexafin gadolinium concurrently with standard [(90)Y]ibritumomab tiuxetan for patients with relapsed/refractory non-Hodgkin's lymphoma.

RESULTS

In HF1 lymphoma cells, motexafin gadolinium and rituximab resulted in synergistic cytotoxicity (combination index, 0.757) through a mitochondrial-mediated caspase-dependent pathway, whereas cell death in Ramos and SUDHL4 cells was additive. Motexafin gadolinium/rituximab combined with radiation (1-3 Gy) resulted in additive apoptosis. Twenty-eight of 30 patients were evaluable on the phase I clinical trial. Median age was 65 years (47-87 years), and histologies were marginal-zone (n = 1), mantle-cell (n = 3), diffuse large cell (n = 6), and follicular lymphoma (n = 18). Of all patients, 86% were rituximab refractory. Therapy was well tolerated, and no dose-limiting toxicity was seen. Overall response rate was 57% [complete remission (CR), 43%], with median time-to-treatment failure of 10 months (1-48+ months) and median duration-of-response of 17 months. Of note, all responses were documented at 4 weeks. Furthermore, in rituximab-refractory follicular lymphoma (n = 14), overall response rate was 86% (CR, 64%), with a median time-to-treatment failure of 14 months (2-48+ months).

CONCLUSIONS

This represents the first report of a novel agent to be combined safely concurrently with radioimmunotherapy. Furthermore, tumor responses with [(90)Y]ibritumomab tiuxetan/motexafin gadolinium were prompt with a high rate of CRs, especially in rituximab-refractory follicular lymphoma.

Stress as an intercellular signal: the emergence of stress-associated molecular patterns (SAMP)

Abstrct Cells are continuously exposed to stressful situations that generally entail generation of reactive oxygen species and other redox alterations. Low levels of stress are physiological and can transmit essential survival or adaptive signals. At higher levels, however, the responses become maladaptive and cause damage. Frequently, stressful events occurring in a few cells propagate, resulting in tissue or even systemic response. Here we review recent evidence suggesting that stressed cells signal their state by expressing on their surface and secreting suitable molecular clues, which we propose to term Stress-Associated Molecular Patterns (SAMP). A unifying mechanism seems to involve the release of oxidoreductases and redox modifiers into the intercellular space, with structural and functional alterations in key signaling molecules. These observations open the way to novel therapeutic strategies.

Elesclomol induces cancer cell apoptosis through oxidative stress

Elesclomol (formerly STA-4783) is a novel small molecule undergoing clinical evaluation in a pivotal phase III melanoma trial (SYMMETRY). In a phase II randomized, double-blinded, controlled, multi-center trial in 81 patients with stage IV metastatic melanoma, treatment with elesclomol plus paclitaxel showed a statistically significant doubling of progression-free survival time compared with treatment with paclitaxel alone. Although elesclomol displays significant therapeutic activity in the clinic, the mechanism underlying its anticancer activity has not been defined previously. Here, we show that elesclomol induces apoptosis in cancer cells through the induction of oxidative stress. Treatment of cancer cells in vitro with elesclomol resulted in the rapid generation of reactive oxygen species (ROS) and the induction of a transcriptional gene profile characteristic of an oxidative stress response. Inhibition of oxidative stress by the antioxidant N-acetylcysteine blocked the induction of gene transcription by elesclomol. In addition, N-acetylcysteine blocked drug-induced apoptosis, indicating that ROS generation is the primary mechanism responsible for the proapoptotic activity of elesclomol. Excessive ROS production and elevated levels of oxidative stress are critical biochemical alterations that contribute to cancer cell growth. Thus, the induction of oxidative stress by elesclomol exploits this unique characteristic of cancer cells by increasing ROS levels beyond a threshold that triggers cell death.

The redox state of the lung cancer microenvironment depends on the levels of thioredoxin expressed by tumor cells and affects tumor progression and response to prooxidants

Here we report that human nonsmall cell lung carcinomas overexpress macrophage migration inhibitory factor (MIF) and thioredoxin (Trx), 2 oxidoreductases with cytokine function, and contain more abundant nonprotein thiols (glutathione and cysteine) than nonneoplastic lung tissues. Cell clones derived from the same lung carcinoma cell lines but expressing different levels of Trx and/or MIF displayed growth rates in vitro and in vivo correlating with Trx but not with MIF. Interestingly, the different clones generate extracellularly reduced nonprotein thiols, in amounts related to the Trx content and inhibited by inhibitors of Trx function. Each clone also showed distinct responses to the prooxidant compound arsenic trioxide. Cells with a strongly antioxidant and aggressive phenotype were more susceptible to the cytotoxic effect of the drug than cells expressing little Trx. The latter counteracted the oxidative stress by increasing Trx expression and thiol release. Together these results indicate that different human lung cancer cell lines have distinct redox properties defined by the levels of Trx and nonprotein thiols, the higher antioxidant phenotype correlating with the higher aggressiveness. Moreover, the redox phenotype dictates their response to prooxidant drugs and must be taken into account when therapeutic interventions with redox active substances are considered.

Synthesis and anticancer properties of water-soluble zinc ionophores

Several water-solubilized versions of the zinc ionophore 1-hydroxypyridine-2-thione (ZnHPT), synthesized as part of the present study, have been found both to increase the intracellular concentrations of free zinc and to produce an antiproliferative activity in exponential phase A549 human lung cancer cultures. Gene expression profiles of A549 cultures treated with one of these water-soluble zinc ionophores, PCI-5002, reveal the activation of stress response pathways under the control of metal-responsive transcription factor 1 (MTF-1), hypoxia-inducible transcription factor 1 (HIF-1), and heat shock transcription factors. Additional oxidative stress response and apoptotic pathways were activated in cultures grown in zinc-supplemented media. We also show that these water-soluble zinc ionophores can be given to mice at 100 micromol/kg (300 micromol/m(2)) with no observable toxicity and inhibit the growth of A549 lung and PC3 prostate cancer cells grown in xenograft models. Gene expression profiles of tumor specimens harvested from mice 4 h after treatment confirmed the in vivo activation of MTF-1-responsive genes. Overall, we propose that water-solubilized zinc ionophores represent a potential new class of anticancer agents.

Glioma pathogenesis-related protein 1 exerts tumor suppressor activities through proapoptotic reactive oxygen species-c-Jun-NH2 kinase signaling

Glioma pathogenesis-related protein 1 (GLIPR1), a novel p53 target gene, is down-regulated by methylation in prostate cancer and has p53-dependent and -independent proapoptotic activities in tumor cells. These properties suggest an important tumor suppressor role for GLIPR1, yet direct genetic evidence of a tumor suppressor function for GLIPR1 is lacking and the molecular mechanism(s), through which GLIPR1 exerts its tumor suppressor functions, has not been shown. Here, we report that the expression of GLIPR1 is significantly reduced in human prostate tumor tissues compared with adjacent normal prostate tissues and in multiple human cancer cell lines. Overexpression of GLIPR1 in cancer cells leads to suppression of colony growth and induction of apoptosis. Mice with an inactivated Glipr1 gene had significantly shorter tumor-free survival times than either Glipr1(+/+) or Glipr1(+/-) mice in both p53(+/+) and p53(+/-) genetic backgrounds, owing to their development of a unique array of malignant tumors. Mechanistic analysis indicated that GLIPR1 up-regulation increases the production of reactive oxygen species (ROS) leading to apoptosis through activation of the c-Jun-NH(2) kinase (JNK) signaling cascade. Thus, our results identify GLIPR1 as a proapoptotic tumor suppressor acting through the ROS-JNK pathway and support the therapeutic potential for this protein.

HIF-1alpha promotes survival of prostate cells at a high zinc environment

BACKGROUND

The prostate contains extremely high concentrations of zinc, which may be required for male reproduction. Although zinc is essential for many cellular functions, excessive zinc induces cellular toxicity in general. However, despite exposure to high zinc environment, prostate cells survive and proliferate. Thus, the aim of this study was to identify the intrinsic molecular species that endow prostate cells with the ability to overcome zinc toxicity.

METHODS

Immunohistochemistry, histofluorescent zinc staining, Western blot, in vitro binding assay, immunoprecipitation, caspase activity assay, and proteasome activity assay.

RESULTS

In rat and human prostates, HIF-1alpha was found to be robustly expressed in epithelial layers containing high zinc levels. Moreover, in cultured prostate cells, HIF-1alpha expression was zinc-dependently induced even under normoxic conditions. Mechanistically, zinc ions inhibited HIF-1-prolyl hydroxylase (PHD) activity, and therefore blocked von Hippel-Lindau tumor suppressor protein (pVHL) binding to HIF-1alpha in vivo and in vitro. The HIF-1alpha stabilization was mediated by oxidative stress induced by zinc ion. Even when prostate cells were treated with high concentrations of zinc ion for extended times, only 10% of cells showed apoptotic death. However, this population of apoptotic cells was increased threefold after HIF-1alpha was knocked-down by siRNA.

CONCLUSION

These results suggest that HIF-1alpha functions as an intrinsic defense molecule that enables prostate cells to survive in a zinc-rich environment.

Motexafin gadolinium injection for the treatment of brain metastases in patients with non-small cell lung cancer

Despite recent advances in technology, targeting, and chemotherapy, brain metastasis from non-small cell lung cancer (NSCLC) remains a significant problem. The vast majority of patients with this diagnosis undergo whole brain radiation therapy (WBRT). However, outcomes are still quite poor with median survivals measured in only months. In an effort to enhance outcomes from external beam radiation treatments, radiosensitizers have been investigated. Motexafin gadolinium (MGd) (Xcytrin^®, Sunnyvale, CA, USA) is a novel radiation sensitizer with a unique mechanism of action that may increase the therapeutic index of WBRT for patients with brain metastases, particularly in those with NSCLC histologies. Here we review the rationale for the use of this drug as well as its current and future role as a radiation enhancer in the management of NSCLC brain metastasis.

The antitumor agent imexon activates antioxidant gene expression: evidence for an oxidative stress response

PURPOSE

The aim of this study was to identify biomarkers that may be predictive for the clinical activity of the redox-active antitumor agent imexon.

EXPERIMENTAL DESIGN

cDNA microarray and quantitative real-time PCR were used to identify global changes in gene expression in peripheral blood mononuclear cells (PBMC) collected from patients treated with imexon during a phase I trial. Electrophoretic mobility shift assays and Western blot analysis were done using the RPMI8226 myeloma cell line grown in vitro and PBMCs treated ex vivo to investigate the molecular mechanism responsible for these gene changes.

RESULTS

Both cDNA microarray and quantitative real-time PCR showed the up-regulation of many antioxidant genes, including thioredoxin reductase-1, glutaredoxin-2, and peroxiredoxin-3 in PBMCs collected from patients treated with imexon. Studies in PBMCs treated ex vivo and RPMI8226 myeloma cells showed that imexon increased binding to the activator protein-1 consensus sequence measured by electrophoretic mobility shift assay. Supershift analysis showed that the majority of the activator protein-1 DNA binding activity was c-Jun, with minor contribution of Jun-D. Nuclear translocation of the nuclear factor (erythroid-derived 1)-like 2 transcription factor and its binding to the antioxidant response element was also increased after imexon treatment, which correlated with an increase in the message levels for nuclear factor (erythroid-derived 1)-like 2/antioxidant response element-regulated antioxidant genes.

CONCLUSIONS

Together, these results show that a predominant biological effect of imexon is a change in redox state that can be detected in surrogate normal tissues as increased redox-sensitive transcription factor binding and increased antioxidant gene expression.

Motexafin gadolinium in the treatment of brain metastases

Motexafin gadolinium (MGd) is a novel, MRI-detectable, anticancer agent that enhances the cytotoxic potential of radiation therapy through several mechanisms, including depleting intracellular reducing metabolites that are necessary for repairing the oxidative damage induced by irradiation. It has tumor-specific uptake, normal tissue sparing, and tolerable and reversible toxicities in clinical trials. MGd's use in conjunction with whole-brain radiation therapy (WBRT) has demonstrated an improvement in neurocognitive decline, neurologic progression, and quality of life in patients with brain metastases from NSCLC. Its use in conjunction with radiosurgery and whole brain radiation therapy in the setting of brain metastases is currently being studied, as is MGd with radiation and temozolomide in patients with glioblastoma multiforme. MGd is also being actively investigated as a single agent or in combination with chemotherapy or radiation therapy in other tumors, including pediatric brain tumors, NSCLC, lymphoma, renal cell carcinoma, and pancreatic and biliary tumors.