Abstract 4849
Background
Endoplasmic reticulum (ER) stress-induced, unfolded protein response (UPR)-mediated apoptosis is a protective mechanism whose failure contributes to malignant tumor progression. XAF1 is a stress-inducible, pro-apoptotic tumor suppressor which is inactivated in many human tumor cells. The molecular signal mechanism explaining its function in controlling ER stress, however, remains largely unclear. In this study, we explored the role of XAF1 in UPR signaling and ER stress-induced apoptosis.
Methods
XAF1 and GRP78 expression were determined by RT-PCR and immunoblot assay. the interplay of XAF1 with GRP78 was defined using immunoprecipitation and in vitro pull-down assays. ER stress was induced using thapsigargin, tunicamycin and brefeldin A. Flow cytometry was used to assess cell cycle progression and apoptosis.
Results
XAF1 expression is upregulated at the transcriptional level in response to ER stress and this activation is abolished by suppression of PERK-Nrf2 but not of IRE1a or ATF6 signaling. This indicates that XAF1 is a target of Nrf2 in transcriptional level and activated by ER stress through the PERK pathway. This XAF1 induction greatly enhances the apoptotic response of tumor cells to ER stress while blockade of XAF1 induction reduces apoptotic sensitivity of tumor cells to ER stress. Intriguingly, XAF1 decreases the protein level of the ER stress sensor, GRP78, and consequently activates UPR signaling. Mechanistically, XAF1 binds directly to GRP78 and stimulates its proteasomal degradation in an E3 ligase ZNF313-dependent manner. XAF1 facilitates ZNF313 interaction with GRP78 and thereby promoting ZNF313-mediated K48 ubiquitination of GRP78. Unlikely wild-type XAF1, mutant XAF1 lacking GRP78- or ZNF313-binding domain shows no activity to promote ER stress-induced apoptosis.
Conclusions
Conclusion: XAF1 sensitizes cells to ER stress and drives apoptotic switch of UPR function away from cell cycle arrest by directly antagonizing GRP78 through the assembly of a ZNF313-mediated destruction complex. Our study identifies first a cell-fate decisions function of XAF1 under ER stress conditions.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Sung-Gil Chi.
Funding
BK.
Disclosure
All authors have declared no conflicts of interest.
Resources from the same session
920 - Efficacy of intravenous (IV) NEPA, a fixed NK1/5-HT3 receptor antagonist (RA) combination, for prevention of CINV following cisplatin- and anthracycline cyclophosphamide (AC)-based chemotherapy (CT)
Presenter: Lee Schwartzberg
Session: Poster Display session 1
Resources:
Abstract
5146 - Efficacy of olanzapine combination in prevention of nausea & vomiting in highly emetogenic chemotherapy
Presenter: Smitha Saldanha
Session: Poster Display session 1
Resources:
Abstract
1947 - Patient-reported outcome data during real-world use of NEPA for prevention of chemotherapy-induced nausea and vomiting in high-risk platin-receiving patients - A prospective multicenter trial
Presenter: Meinolf Karthaus
Session: Poster Display session 1
Resources:
Abstract
6163 - A study evaluating steroid induced metabolic syndrome after antiemetic dexamethasone therapy in patients received high emetic risk chemotherapy
Presenter: Hee Jun Kim
Session: Poster Display session 1
Resources:
Abstract
2154 - High incidence of nausea during initial and repeated courses if intravenous chemotherapy in patients receiving guideline consistent antiemetic prophylaxis - a prospective, observational, real world study.
Presenter: Teresa Smit
Session: Poster Display session 1
Resources:
Abstract
1637 - "Randomised controlled trial of Scalp Cooling (SC) for the prevention of Chemotherapy Induced Alopecia (CIA)”
Presenter: Jyoti Bajpai
Session: Poster Display session 1
Resources:
Abstract
5351 - Performance of the ‘4S rule’ to predict short-term outcomes in cancer outpatients with unsuspected pulmonary embolism.
Presenter: David Pesántez Coronel
Session: Poster Display session 1
Resources:
Abstract
1189 - Prevalence of venous thromboembolism based on intensive screening for patients with advanced solid tumor in prospective observational study
Presenter: Shota Omori
Session: Poster Display session 1
Resources:
Abstract
4340 - Short-term outcomes of cancer patients with pulmonary embolism according to the setting (hospital-acquired vs. outpatient) at diagnosis.
Presenter: Diego Muñoz Guglielmetti
Session: Poster Display session 1
Resources:
Abstract
4658 - Patient-reported outcomes associated with switching to rivaroxaban for the treatment of venous thromboembolism (VTE) in patients with active cancer
Presenter: Alexander Cohen
Session: Poster Display session 1
Resources:
Abstract