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1.  Celastrol induces unfolded protein response-dependent cell death in head and neck cancer 
Experimental cell research  2014;330(2):412-422.
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.
doi:10.1016/j.yexcr.2014.08.014
PMCID: PMC4280347  PMID: 25139619
Celastrol; ER stress; Unfolded protein response; Oral cancer; Apoptosis; Drug discovery; Chaperone; Protein folding
2.  SMAD4 is a potential prognostic marker in human breast carcinomas 
SMAD4 is a downstream mediator of transforming growth factor beta. While its tumor suppressor function has been investigated as a prognostic biomarker in several human malignancies, its role as a prognostic marker in breast carcinoma is still undefined. We investigated SMAD4 expression in breast carcinoma samples of different histologic grades to evaluate the association between SMAD4 and outcome in breast cancer. We also investigated the role of SMAD4 expression status in MDA-MB-468 breast cancer cells in responding to TGF-β stimulation. SMAD4 expression was assessed in 53 breast ductal carcinoma samples and in the surrounding normal tissue from 50 of the samples using immunohistochemistry, Western blot, and real-time PCR. TGF-β-SMAD and non-SMAD signaling was assessed by Western blot in MDA-MB-468 cells with and without SMAD4 restoration. SMAD4 expression was reduced in ductal breast carcinoma as compared to surrounding uninvolved ductal breast epithelia (p <0.05). SMAD4 expression levels decreased from Grade 1 to Grade 3 ductal breast carcinoma as assessed by immunohistochemistry (p <0.05). Results were recapitulated by tissue array. In addition, immunohistochemistry results were further confirmed at the protein and mRNA level. We then found that non-SMAD MEK/MAPK signaling was significantly different between SMAD4 expressing MDA-MB-468 cells and SMAD4-null MDA-MB-468 cells. This is the first study indicating that SMAD4 plays a key role in shifting MAPK signaling. Further, we have demonstrated that SMAD4 has a potential role in the development of breast carcinoma and SMAD4 was a potential prognostic marker of breast carcinoma. Our findings further support the role of SMAD4 in breast carcinoma development. In addition, we observed an inverse relationship between SMAD4 levels and breast carcinoma histological grade. Our finding indicated that SMAD4 expression level in breast cancer cells played a role in responding non-SMAD signaling but not the canonic SMAD signaling. Further mechanistic studies are necessary to establish the role of SMAD4 in breast carcinoma prognosis and potential specific targeting.
doi:10.1007/s13277-013-1088-1
PMCID: PMC4142205  PMID: 23975369
Ductal breast carcinoma; SMAD4; Immunohistochemistry; Tissue array; Quantitative real-time PCR; Western blot analysis; Prognosis; TGF-β; Non-SMAD signaling
3.  Large-scale analysis of UPR-mediated apoptosis in human cells 
Methods in Enzymology  2011;491:57-71.
The historic distinction between academic- and industry-driven drug discovery, whereby investigators at universities worked to uncover the elusive principles of basic science and drug companies advanced the identification of drug targets and 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.
doi:10.1016/B978-0-12-385928-0.00004-3
PMCID: PMC3390927  PMID: 21329794
4.  Complementary Cell-Based High Throughput Screens Identify Novel Modulators of the Unfolded Protein Response 
Journal of Biomolecular Screening  2011;16(8):825-835.
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 two 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, we 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. We 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 sub-pathways. A ~66K compound collection was screened at the University of Michigan Center for Chemical Genomics that included a unique library of pre-fractionated natural product extracts. The mycotoxin methoxycitrinin was isolated from a natural extract and found to selectively activate the CHOP-luciferase reporter at 80μM. A series of citrinin derivatives were isolated from these extracts, including a unique congener that has not been previously described. In an effort to identify more potent compounds we examined the ability of citrinin and the structurally related mycotoxins ochratoxin A and patulin to activate the UPR. Strikingly, we found that patulin at 2.5 – 10μM 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.
doi:10.1177/1087057111414893
PMCID: PMC3374590  PMID: 21844328
unfolded protein response; endoplasmic reticulum stress; cell-based assay; luciferase reporter; natural products
5.  UPR pathways combine to prevent hepatic steatosis caused by ER stress-mediated suppression of transcriptional master regulators 
Developmental cell  2008;15(6):829-840.
Summary
The unfolded protein response (UPR) is linked to metabolic dysfunction, yet it is not known how ER disruption might influence metabolic pathways. Using a multilayered genetic approach, we find that mice with genetic ablations of either ER stress sensing pathways (ATF6α, eIF2α, IRE1α), or of ER quality control (p58IPK), share a common dysregulated response to ER stress that includes the development of microvesicular steatosis. The rescue of ER protein processing capacity by the combined action of UPR pathways during stress prevents the suppression of a subset of metabolic transcription factors that regulate lipid homeostasis. This suppression occurs in part by unresolved ER stress perpetuating expression of the transcriptional repressor CHOP. As a consequence, metabolic gene expression networks are directly responsive to ER homeostasis. These results reveal an unanticipated direct link between ER homeostasis and the transcriptional regulation of metabolism and suggest mechanisms by which ER stress might underlie microvesicular steatosis.
doi:10.1016/j.devcel.2008.10.015
PMCID: PMC2923556  PMID: 19081072

Results 1-5 (5)