The MNRR1 activator nitazoxanide abrogates lipopolysaccharide-induced preterm birth in mice

Intra-amniotic inflammation leading to preterm birth is one of the leading causes of neonatal morbidity and mortality. We recently reported that the mitochondrial levels of MNRR1 (Mitochondrial Nuclear Retrograde, Regulator 1; also called CHCHD2, AAG10, or PARK22), an important bi-organellar regulator of cellular function, are reduced in the context of inflammation and that genetic and pharmacological increases in MNRR1 levels can counter the inflammatory profile. Herein, we show that nitazoxanide, a clinically approved drug, is an activator of MNRR1 and abrogates preterm birth in a well-characterized murine model caused by intra-amniotic lipopolysaccharide (LPS) injection.

HTS Identification of Activators and Inhibitors of Endoplasmic Reticulum (ER) Stress and the Unfolded Protein Response (UPR)

The identification of small molecules and natural product extracts that enhance or interfere with the productivity of protein folding in the endoplasmic reticulum (ER) has the potential to improve a wide variety of human pathologies. Every protein that is destined for a lysosome, integral to the cell membrane, or secreted, is folded, post-translationally modified, and exported to the cytoplasm from the ER-Golgi complex. The following protocols have successfully employed several high-fidelity cell-based luciferase high-throughput screens (HTS) to identify activators and inhibitors of ER stress and the unfolded protein response (UPR).

Targeting the unfolded protein response in head and neck and oral cavity cancers

Many FDA-approved anti-cancer therapies, targeted toward a wide array of molecular targets and signaling networks, have been demonstrated to activate the unfolded protein response (UPR). Despite a critical role for UPR signaling in the apoptotic execution of cancer cells by many of these compounds, the authors are currently unaware of any instance whereby a cancer drug was developed with the UPR as the intended target. With the essential role of the UPR as a driving force in the genesis and maintenance of the malignant phenotype, a great number of pre-clinical studies have surged into the medical literature describing the ability of dozens of compounds to induce UPR signaling in a myriad of cancer models. The focus of the current work is to review the literature and explore the role of the UPR as a mediator of chemotherapy-induced cell death in squamous cell carcinomas of the head and neck (HNSCC) and oral cavity (OCSCC), with an emphasis on preclinical studies.

Disulfiram (Antabuse) Activates ROS-Dependent ER Stress and Apoptosis in Oral Cavity Squamous Cell Carcinoma

A paucity of advances in the development of novel therapeutic agents for squamous cell carcinomas of the head and neck, oral cavity (OSCC) and oropharynx, has stagnated disease free survival rates over the past two decades. Although immunotherapies targeted against checkpoint inhibitors such as PD-1 or CTLA-4 are just now entering the clinic for late stage disease with regularity the median improvement in overall survival is only about three months. There is an urgent unmet clinical need to identify new therapies that can be used alone or in combination with current approaches to increase survival by more than a few months. Activation of the apoptotic arm of the unfolded response (UPR) with small molecules and natural products has recently been demonstrated to be a productive approach in pre-clinical models of OSCC and several other cancers. The aim of current study was to perform a high throughput screen (HTS) with a diverse chemical library to identify compounds that could induce CHOP, a component of the apoptotic arm of the UPR. Disulfiram (DSF, also known as Antabuse) the well-known aversion therapy used to treat chronic alcoholism emerged as a hit that could generate reactive oxygen species, activate the UPR and apoptosis and reduce proliferation in OSCC cell cultures and xenografts. A panel of murine embryonic fibroblasts null for key UPR intermediates (e.g., Chop and Atf4) was resistant to DSF suggesting that an intact UPR is a key element of the mechanism regulating the antiproliferative effects of DSF.

Disparities in impact of nasopharyngeal cancer: An analysis of global health burden

OBJECTIVES

Nasopharyngeal carcinoma has a unique worldwide racial and geographic distribution. Our objective was to evaluate socioeconomic disparities in the burden of nasopharyngeal cancer (NPC) between endemic and nonendemic regions.

METHODS

To demonstrate trends regarding societal burden of NPC and socioeconomic development, national disability-adjusted life year (DALY) rates and human development indices (HDI) between 1990 and 2015 were evaluated. Countries were divided based on the endemic versus nonendemic presence of NPC and further analyzed by HDI status as specified by the United Nations Development Program. Gini coefficients and concentration index were used to evaluate global equality in NPC burden over this period.

RESULTS

Age-standardized DALYs dropped from 36.1 in 1990 to 26.5 in 2015 (26.6% decline) (r = -0.991, P < 0.001). Lower socioeconomic countries harbored greater NPC burden upon controlling by endemic and nonendemic regions, as demonstrated by progressively negative concentration indexes. Health inequality was greater in nonendemic countries than in endemic countries (P < 0.01).

CONCLUSION

To our knowledge, this is the first study to investigate socioeconomic-related changes in NPC burden using statistical tools such as the Gini coefficient and concentration index. Although the burden of NPC has steadily decreased, there remain persistent inequalities associated with socioeconomic disparities. Nasopharyngeal cancer burden is more pronounced in countries with lower HDI. Our results reinforce the importance of increasing resources for developing countries and continuing inquiry into the screening, diagnosis, and management of NPC.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:2482-2486, 2019.

Identification of Portimine B, a New Cell Permeable Spiroimine That Induces Apoptosis in Oral Squamous Cell Carcinoma

Spiroimines are a class of compounds produced by marine dinoflagellates with a wide range of toxicity and therapeutic potential. The smallest of the cyclic imines, portimine, is far less toxic than other known members in several animal models. Portimine has also been shown to induce apoptosis and reduce the growth of a variety of cancer cell lines at low nanomolar concentrations. In an effort to discover new spiroimines, the current study undertook a metabolomic analysis of cultures of cyclic imine-producing dinoflagellates, and a new analog of portimine was discovered in which the five-membered cyclic ether is open. Further scrutiny with human oral cavity squamous cell carcinoma (OCSCC) cell lines revealed that the open ring congener was less potent than portimine A but could still lead to the accumulation of apoptotic gene transcripts, fragment genomic DNA, and reduce cancer cell proliferation in the range of 100-200 nM.

Laryngeal cancer: Global socioeconomic trends in disease burden and smoking habits

OBJECTIVES/HYPOTHESIS

To characterize health burden and determine the associated level of equality of laryngeal carcinoma (LC) burden at a global level.

METHODS

One hundred eighty-four countries were organized by socioeconomic status using Human Development Index (HDI) categorizations provided by the United Nations Development Program. Disability-adjusted life years (DALYs), obtained from The Global Health Data Exchange, were calculated and compared between each HDI category for the period from 1990 to 2015. Equality of LC burden was then evaluated with concentration indices.

RESULTS

Global LC burden, as measured by age-standardized DALYs, has improved significantly over the 25-year period studied. This burden has declined for very high, high, and medium HDI countries, whereas it has remained unchanged for low HDI countries. The majority of LC global burden was found in high socioeconomic countries before 2010 and has shifted toward low socioeconomic countries, as indicated by concentration indices. Over the last 25 years, Central and Eastern Europe continue to have the largest disease burden in the world.

CONCLUSION

This is the first analysis that we are aware of investigating health disparities of LC at a global level. The global burden of the disease has declined, which is a trend corresponding with significantly reduced smoking behaviors in developed countries. Although the global inequality gap decreased between 2010 and 2015, there remain reasons for concern. Smoking continues to trend upward in low socioeconomic countries, which could increase LC burden in low socioeconomic countries in the near future. A new global initiative directed toward low socioeconomic countries may yield dividends in preventing subsequent disparities in the LC burden.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:2039-2053, 2018.

Celastrol induces apoptosis in hepatocellular carcinoma cells via targeting ER-stress/UPR

Hepatocellular carcinoma (HCC) is one of the most serious and deadly diseases worldwide with limited options for effective treatment. Biomarker-based active compound targeting therapy may shed some light on novel drugs for HCC. The endoplasmic reticulum (ER) stress and unfolded protein response (UPR) play important roles in the regulation of cell fate and have become novel signaling targets for the development of anticancer drugs. Celastrol, a triterpene from traditional Chinese medicine, has been reported to possess anti-tumor effects on various cancers. We, along with several other research groups, have recently reported that UPR was induced by celastrol in several different cancers, including hepatocellular carcinoma. However, UPR status in HCC still remains unclear. The role of ER stress and autophagy in response to celastrol also has yet to be elucidated. Our results demonstrated that celastrol could cause G2/M phase rest and inhibit proliferation in HepG2 and Bel7402. Exposure to celastrol resulted in the activation of the intrinsic apoptotic pathway, via ER stress and the UPR. In murine syngeneic model studies celastrol inhibited H22 tumor growth via the induction of ER stress and apoptosis. Our study suggests that celastrol is a potential drug for HCC therapy via targeting ER-stress/UPR.

Oropharyngeal lymphoma: A US population based analysis

OBJECTIVES

To describe the epidemiology and analyze factors determinant of survival in patients with oropharyngeal lymphoma, using the Surveillance Epidemiology and End Results (SEER) database.

METHODS

2504 patients with oropharyngeal lymphoma were identified using the most recent SEER database entry from 1976 to 2016. Demographic information, Ann Arbor stage, tumor histopathology and location were collected. Multivariate analysis was used to analyze patient and tumor characteristics associated with survival.

RESULTS

The mean age of the patients studied was 60.5years, 58.4% of the subjects were male and 81% were white. Diffuse large B cell lymphoma (DLBCL) was the most common histologic subtype involving 56.9% of cases. The most common subsite of origin was the tonsil, with 71% of lymphomas originating from there. The association of survival with stage, age, tumor location, presence of B symptoms, tumor pathology, gender and race was analyzed using multivariate regression. Decreased survival was significantly associated with patient age p<0.0001, Ann Arbor staging p=0.005, the presence of B symptoms p=0.003 and tumor histopathology (T cell tumors) p=0.01. Patients with tumors originating from the soft palate were significantly more likely to die asa result of their disease p=0.03.

CONCLUSION

Oropharyngeal lymphoma most commonly originates from the tonsil. DLBCL is the most common subtype and has a good prognosis. The presence of B symptoms, tumors originating from the soft palate and patients with T cell tumors have the worst prognosis. This information can potentially be of great utility to the head and neck surgeon discussing prognosis with patients suffering from oropharyngeal lymphoma.

The Utility of Real-Time Quantitative Polymerase Chain Reaction Genotype Detection in the Diagnosis of Urinary Tract Infections in Children

Urinary tract infections (UTIs) are the most common serious bacterial infection in children with significant morbidity with delayed diagnosis. Polymerase chain reaction (PCR) is very accurate in detecting bacteria and widely available, but has never been evaluated to detect UTIs in children. To assess the utility of PCR as a rapid diagnostic tool, we conducted a prospective cohort study of 193 urine samples from children younger than 36 months undergoing evaluation for UTI in the emergency department over a 10-month period. A quantification cycle (Cq) threshold of 26.15 identified all Escherichia coli positive samples with sensitivity and specificity of 100% and 99.5%, respectively (95% CI = 71.5%-100% and 97.9%-99.5%, respectively). A Cq threshold of 19.03 identified E coli infections >100 000 colony forming units/mL with sensitivity and specificity of 100% (95% CI = 72.2%-100% and 98.6%-100%, respectively). PCR is very accurate in diagnosing E coli UTIs in young children and could be useful as a rapid diagnostic tool.

Systemic therapy for head and neck squamous cell carcinoma: Historical perspectives and recent breakthroughs

OBJECTIVES

Despite dramatic developments in drugs established for other malignancies, historically there have been few novel systemic agents available for the management of head and neck squamous cell carcinoma (HNSCC). However, the last decade has observed increased interest in targeted therapies for HNSCC. In 2006, cetuximab became the first major drug for HNSCC to gain Food and Drug Administration (FDA) approval in 3 decades. Recently, both pembrolizumab and nivolumab gained FDA approval for treatment of recurrent or metastatic HNSCC, and trials for other indications in HNSCC are actively underway. As older agents including cisplatin and 5-fluorouracil continue to play a significant role in the management of advanced HNSCC, an understanding of their legacy is paramount. This historical review is not meant to exhaustively catalog every finding relating to HNSCC systemic therapy, but rather is meant to highlight important advances.

DATA SOURCES

Case series and clinical trials available in the literature.

REVIEW METHODS

Historically significant series and trials evaluating HNSCC systemic therapy were evaluated.

RESULTS

Standard regimens employed today are largely comprised of drugs discovered over 4 decades ago, although a number of recent phase III clinical trials have shown great promise, leading to the adoption of several new chemotherapeutic agents and treatment strategies.

CONCLUSIONS

These findings reinforce the importance of supporting further HNSCC drug discovery as modern treatment strategies using systemic therapy have resulted in measurable improvements in oncologic outcomes. Laryngoscope, 127:2565-2569, 2017.

Recent Trends in Oral Cavity Cancer Research Support in the United States

The objectives were to characterize oral cavity cancer (OCC) funding from the National Institutes of Health (NIH) with a secondary aim of comparing NIH support provided to OCC and other malignancies. NIH awards supporting OCC inquiry from 2000 to 2014 were accessed from the NIH RePORTER database. These data were used to evaluate temporal trends and the role of human papilloma virus and to determine the academic training and professional profiles of the principal investigators. Comparison of 2014 funding levels with other malignancies was also performed, controlling for incidence. Overall funding totals decreased considerably after 2009. Funding administered through the National Institute of Dental and Craniofacial Research (NIDCR) was 6.5 times greater than dollars awarded by the National Cancer Institute in 2000. During the period evaluated, NIDCR support decreased in most years, while National Cancer Institute support increased and approached NIDCR funding levels. Funding for human papilloma virus-related projects gradually rose, from 3.4% of dollars in 2000 to 2004 to 6.2% from 2010 to 2014 ( P < 0.05). A majority of principal investigators had a PhD omnia solus (57%), and 13% possessed dual PhD/clinical degrees. Among clinicians with specialty training, otolaryngologists and oral/maxillofacial pathologists garnered the most funding. OCC had a 2014 funding:incidence ratio of $785, much lower than for other malignancies. There has been increased volatility in funding support in recent years possibly due to budget cuts and sequestration. The National Cancer Institute has played an increasingly important role in supporting OCC research, concomitant with decreasing NIDCR support. Our findings suggest that OCC is underfunded relative to other non-oral cavity malignancies, indicating a need to increase the focus on rectifying the disparity.

Dimethyl fumarate ameliorates myoclonus stemming from protein misfolding in oligodendrocytes

Multiple sclerosis (MS) is considered a primary autoimmune disease; however, this view is increasingly being challenged in basic and clinical science arenas because of the growing body of clinical trials' data showing that exclusion of immune cells from the CNS only modestly slows disease progression to disability. Accordingly, there is significant need for expanding the scope of potential disease mechanisms to understand the etiology of MS. Concomitantly, the use of a broader range of pre-clinical animal models for characterizing existing efficacious clinical treatments may elucidate additional or unexpected mechanisms of action for these drugs that augment insight into MS etiology. Herein, we explore the in vivo mechanism of action of dimethyl fumarate, which has been shown to suppress oxidative stress and immune cell responses in psoriasis and MS. Rather than studying this compound in the context of an experimental autoimmune-induced attack on the CNS, we have used a genetic model of hypomyelination, male rumpshaker (rsh) mice, which exhibit oligodendrocyte metabolic stress and startle-induced subcortical myoclonus during development and into adulthood. We find that myoclonus is reduced 30-50% in treated mutants but we do not detect substantial changes in metabolic or oxidative stress response pathways, cytokine modulation, or myelin thickness (assessed by anova). All procedures involving vertebrate animals in this study were reviewed and approved by the IACUC committee at Wayne State University.

Recent trends in oropharyngeal cancer funding and public interest

OBJECTIVES/HYPOTHESIS

The incidence of oropharyngeal cancer (OPC) has increased in the United States. This has been driven by an increase in human papillomavirus (HPV)-positive OPC. Our objective is to determine trends in National Institutes (NIH)-supported research funding and public interest in OPC.

METHODS

The NIH Research Portfolio Online Reporting Tools database was evaluated for projects related to OPC between 2004 and 2015. Projects were evaluated for total funding, relation to HPV, principal investigator departmental affiliation and degree, and NIH agency or center responsible for grant. The Google Trends database was evaluated for relative Internet search popularity of oropharyngeal cancer and related search terms between 2004 and 2015.

RESULTS

In terms of NIH funding, 100 OPC-related projects representing 242 grant years and $108.5 million were funded between 2004 and 2015. Total NIH funding for OPC projects increased from $167,406 in 2004 to $16.2 million in 2015. Funding for HPV-related OPC increased from less than $2 million yearly between 2004 and 2010 up to $12.7 million in 2015. Principal investigators related to radiation oncology ($41.8 million) and with doctor of medicine degrees ($52.8 million) received the largest share of total funding. Relative Internet search popularity for oropharyngeal cancer has increased from 2004 to 2015 compared to control cancer search terms.

CONCLUSION

Increased public interest and NIH funding has paralleled the rising incidence of OPC. NIH funding has been driven by projects related to the role of HPV in OPC.

LEVEL OF EVIDENCE

2c. Laryngoscope, 127:1345-1350, 2017.

Head and Neck Cancer

Despite a considerable expansion in our therapeutic repertoire for management of other malignancies, mortality from head and neck cancer (HNC) has not significantly improved in recent decades. Upon normalizing National Institutes of Health-awarded R01 and R01-equivalent grants by incidence, thyroid cancer ($214) and HNC ($1329) received the fewest funding dollars. Upon adjusting funding totals by mortality, HNC was 7th out of 9 cancers evaluated ($6138). These findings highlight HNC as an underfunded disease versus other cancers. As data detailing grant applications (including unsuccessful grants) are not publicly available, it is not clear if these disparities stem from fewer applications or fewer opportunities. Our hope is that this commentary will spur further investigation into strategies to increase HNC inquiry and funding for trainees as well as early-stage and established investigators.

Borrelidin Induces the Unfolded Protein Response in Oral Cancer Cells and Chop-Dependent Apoptosis

Oral squamous cell carcinoma (OSCC) is the most common cancer affecting the oral cavity, and US clinics will register about 30,000 new patients in 2015. Current treatment modalities include chemotherapy, surgery, and radiotherapy, which often result in astonishing disfigurement. Cancers of the head and neck display enhanced levels of glucose-regulated proteins and translation initiation factors associated with endoplasmic reticulum (ER) stress and the unfolded protein response (UPR). Previous work demonstrated that chemically enforced UPR could overwhelm these adaptive features and selectively kill malignant cells. The threonyl-tRNA synthetase (ThRS) inhibitor borrelidin and two congeners were discovered in a cell-based chemical genomic screen. Borrelidin increased XBP1 splicing and led to accumulation of phosphorylated eIF2α and UPR-associated genes, prior to death in panel of OSCC cells. Murine embryonic fibroblasts (MEFs) null for GCN2 and PERK were less able to accumulate UPR markers and were resistant to borrelidin. This study demonstrates that UPR induction is a feature of ThRS inhibition and adds to a growing body of literature suggesting ThRS inhibitors might selectively target cancer cells.

Novel Lobophorins Inhibit Oral Cancer Cell Growth and Induce Atf4- and Chop-Dependent Cell Death in Murine Fibroblasts

As part of the International Cooperative Biodiversity Groups (ICBG) Program, we were interested in identifying biologically active unfolded protein response (UPR) inducing compounds from marine microorganisms isolated from Costa Rican biota. With this aim in mind we have now generated more than 33,000 unique prefractionated natural product extracts from marine and terrestrial organisms that have been submitted to the Center of Chemical Genomics (CCG) at the University of Michigan for high throughput screening (HTS). An effective complementary cell-based assay to identify novel modulators of UPR signaling was used for screening extracts. Active fractions were iteratively subjected to reverse-phase HPLC chromatographic analysis, and together with lobophorin A, B, E, and F (1-4), three new lobophorin congeners, designated as CR1 (5), CR2 (6), and CR3 (7) were isolated. Herein, we report that secondary assays revealed that the new lobophorins induced UPR-associated gene expression, inhibited oral squamous cell carcinoma cell growth, and led to UPR-dependent cell death in murine embryonic fibroblast (MEF) cells.

Induction of BCL2-Interacting Killer, BIK, is Mediated for Anti-Cancer Activity of Curcumin in Human Head and Neck Squamous Cell Carcinoma Cells

Naturally occurring diarylheptanoid curcumin (CUR), a principal component of the Asian spice turmeric, has been shown to have anti-cancer effects in many tumor types. However, a detailed mechanism regarding CUR induced tumor cell killing remain to be comprehensively explored. Using two head neck squamous cell carcinoma (HNSCC) cell lines FaDu (hypopharyngeal) and Cal27 (tongue), we demonstrated a novel mechanism by which CUR levies the cytotoxic effect. We found that CUR induced upregulation of pro-apoptotic Bik, down-regulation of survival signaling by AKT and NF-κB prior to the induction of the caspase-cascade reduction of cell proliferation, are primary mechanisms of CUR-induced cell death, thus providing insights into the anti-tumor activity of CUR in HNSCC cells.

Discovery of Sulfonamidebenzamides as Selective Apoptotic CHOP Pathway Activators of the Unfolded Protein Response

Cellular proteins that fail to fold properly result in inactive or disfunctional proteins that can have toxic functions. The unfolded protein response (UPR) is a two-tiered cellular mechanism initiated by eukaryotic cells that have accumulated misfolded proteins within the endoplasmic reticulum (ER). An adaptive pathway facilitates the clearance of the undesired proteins; however, if overwhelmed, cells trigger apoptosis by upregulating transcription factors such as C/EBP-homologous protein (CHOP). A high throughput screen was performed directed at identifying compounds that selectively upregulate the apoptotic CHOP pathway while avoiding adaptive signaling cascades, resulting in a sulfonamidebenzamide chemotype that was optimized. These efforts produced a potent and selective CHOP inducer (AC₅₀ = 0.8 μM; XBP1 > 80 μM), which was efficacious in both mouse embryonic fibroblast cells and a human oral squamous cell cancer cell line, and demonstrated antiproliferative effects for multiple cancer cell lines in the NCI-60 panel.

Celastrol induces unfolded protein response-dependent cell death in head and neck cancer

The survival rate for patients with oral squamous cell carcinoma (OSCC) has not seen marked improvement in recent decades despite enhanced efforts in prevention and the introduction of novel therapies. We have reported that pharmacological exacerbation of the unfolded protein response (UPR) is an effective approach to killing OSCC cells. The UPR is executed via distinct signaling cascades whereby an initial attempt to restore folding homeostasis in the endoplasmic reticulum during stress is complemented by an apoptotic response if the defect cannot be resolved. To identify novel small molecules able to overwhelm the adaptive capacity of the UPR in OSCC cells, we engineered a complementary cell-based assay to screen a broad spectrum of chemical matter. Stably transfected CHO-K1 cells that individually report (luciferase) on the PERK/eIF2α/ATF4/CHOP (apoptotic) or the IRE1/XBP1 (adaptive) UPR pathways, were engineered [1]. The triterpenoids dihydrocelastrol and celastrol were identified as potent inducers of UPR signaling and cell death in a primary screen and confirmed in a panel of OSCC cells and other cancer cell lines. Biochemical and genetic assays using OSCC cells and modified murine embryonic fibroblasts demonstrated that intact PERK-eIF2-ATF4-CHOP signaling is required for pro-apoptotic UPR and OSCC death following celastrol treatment.

Complementary cell-based high-throughput screens identify novel modulators of the unfolded protein response

Despite advances toward understanding the prevention and treatment of many cancers, patients who suffer from oral squamous cell carcinoma (OSCC) confront a survival rate that has remained unimproved for more than 2 decades, indicating our ability to treat them pharmacologically has reached a plateau. In an ongoing effort to improve the clinical outlook for this disease, we previously reported that an essential component of the mechanism by which the proteasome inhibitor bortezomib (PS-341, Velcade) induced apoptosis in OSCC required the activation of a terminal unfolded protein response (UPR). Predicated on these studies, the authors hypothesized that high-throughput screening (HTS) of large diverse chemical libraries might identify more potent or selective small-molecule activators of the apoptotic arm of the UPR to control or kill OSCC. They have developed complementary cell-based assays using stably transfected CHO-K1 cell lines that individually assess the PERK/eIF2α/CHOP (apoptotic) or the IRE1/XBP1 (adaptive) UPR subpathways. An 66 K compound collection was screened at the University of Michigan Center for Chemical Genomics that included a unique library of prefractionated natural product extracts. The mycotoxin methoxycitrinin was isolated from a natural extract and found to selectively activate the CHOP-luciferase reporter at 80 µM. A series of citrinin derivatives was isolated from these extracts, including a unique congener that has not been previously described. In an effort to identify more potent compounds, the authors examined the ability of citrinin and the structurally related mycotoxins ochratoxin A and patulin to activate the UPR. Strikingly, it was found that patulin at 2.5 to 10 µM induced a terminal UPR in a panel of OSCC cells that was characterized by an increase in CHOP, GADD34, and ATF3 gene expression and XBP1 splicing. A luminescent caspase assay and the induction of several BH3-only genes indicated that patulin could induce apoptosis in OSCC cells. These data support the use of this complementary HTS strategy to identify novel modulators of UPR signaling and tumor cell death.

Large-scale analysis of UPR-mediated apoptosis in human cells

The historic distinction between academic- and industry-driven drug discovery, whereby academicians worked to identify therapeutic targets and pharmaceutical companies advanced probe discovery, has been blurred by an academic high-throughput chemical genomic revolution. It is now common for academic labs to use biochemical or cell-based high-throughput screening (HTS) to investigate the effects of thousands or even hundreds of thousands of chemical probes on one or more targets over a period of days or weeks. To support the efforts of individual investigators, many universities have established core facilities where screening can be performed collaboratively with large chemical libraries managed by highly trained HTS personnel and guided by the experience of computational, medicinal, and synthetic organic chemists. The identification of large numbers of promising hits from such screens has driven the need for independent labs to scale down secondary in vitro assays in the hit to lead identification process. In this chapter, we will describe the use of luminescent and quantitative reverse transcription real-time PCR (qRT-PCR) technologies that permit evaluation of the expression patterns of multiple unfolded protein response (UPR) and apoptosis-related genes, and simultaneously evaluate proliferation and cell death in 96- or 384-well format.

Proteasome inhibitor PS-341 induces apoptosis in cisplatin-resistant squamous cell carcinoma cells by induction of Noxa

Cisplatin is one of the most common DNA-damaging agents used for treating patients with solid tumors such as squamous cell carcinoma (SCC). Unfortunately, significant levels of resistance in SCC cells emerge rapidly following cisplatin treatment. Here we report that the proteasome inhibitor PS-341, the representative of a new class of chemotherapeutic drugs, was capable of inducing apoptosis in cisplatin-resistant SCC cells via the endoplasmic reticulum stress. PS-341 stimulated the phosphorylation of PERK and the unfolded protein response, resulting in the induction of the transcription factor ATF-4. Importantly, the Bcl-2 homology domain 3-only (BH3-only) protein Noxa was found to be strongly induced in cisplatin-resistant SCC cells by PS-341 but not by cisplatin. The knock-down of Noxa using small interference RNA significantly abolished PS-341-mediated apoptosis in SCC cells. Using eIF2alpha mutant mouse embryonic fibroblasts, we found that functional eIF2alpha played an essential role in PS-341-induced Noxa expression. Taken together, our novel findings reveal a direct link between PS-341-induced endoplasmic reticulum stress and the mitochondria-dependent apoptotic pathway and suggest that PS-341 may be utilized for overcoming cisplatin-resistance in human SCC.