Seong Hye Park

Metformin enhances TRAIL-induced apoptosis by Mcl-1 degradation via Mule in colorectal cancer cells

Metformin is an anti-diabetic drug with a promising anti-cancer potential. In this study, we show that subtoxic doses of metformin effectively sensitize human colorectal cancer (CRC) cells to tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), which induces apoptosis. Metformin alone did not induce apoptosis, but significantly potentiated TRAIL-induced apoptosis in CRC cells. CRC cells treated with metformin and TRAIL showed activation of the intrinsic and extrinsic pathways of caspase activation. We attempted to elucidate the underlying mechanism, and found that metformin significantly reduced the protein levels of myeloid cell leukemia 1 (Mcl-1) in CRC cells and, the overexpression of Mcl-1 inhibited cell death induced by metformin and/or TRAIL. Further experiments revealed that metformin did not affect mRNA levels, but increased proteasomal degradation and protein stability of Mcl-1. Knockdown of Mule triggered a significant decrease of Mcl-1 polyubiquitination. Metformin caused the dissociation of Noxa from Mcl-1, which allowed the binding of the BH3-containing ubiquitin ligase Mule followed by Mcl-1ubiquitination and degradation. The metformin-induced degradation of Mcl-1 required E3 ligase Mule, which is responsible for the polyubiquitination of Mcl-1. Our study is the first report indicating that metformin enhances TRAIL-induced apoptosis through Noxa and favors the interaction between Mcl-1 and Mule, which consequently affects Mcl-1 ubiquitination.

Genipin suppresses colorectal cancer cells by inhibiting the Sonic Hedgehog pathway

Genipin, a major component of Gardenia jasminoides Ellis fruit, has been shown to inhibit the growth of gastric, prostate, and breast cancers. However, the anti-proliferative activity of genipin in colorectal cancer (CRC) has not been characterized. Herein, we demonstrated that genipin inhibits the proliferation of CRC cells and that genipin suppressed the Hedgehog pathway. Further investigation showed that p53 and NOXA protein levels were increased during inhibition of Hedgehog pathway-mediated apoptosis in CRC cells. We also showed that p53 modulated the expression of NOXA during genipin-induced apoptosis, and suppression via SMO also played a role in this process. Subsequently, GLI1 was ubiquitinated by the E3 ligase PCAF. In a xenograft tumor model, genipin suppressed tumor growth, which was also associated with Hedgehog inactivation. Taken together, these results suggest that genipin induces apoptosis through the Hedgehog signaling pathway by suppressing p53. These findings reveal a novel regulatory mechanism involving Hedgehog/p53/NOXA signaling in the modulation of CRC cell apoptosis and tumor-forming defects.

Cyclopamine sensitizes TRAIL-resistant gastric cancer cells to TRAIL-induced apoptosis via endoplasmic reticulum stress-mediated increase of death receptor 5 and survivin degradation

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is one of the most effective cancer treatments owing to its ability to selectively kill cancer cells, without affecting normal cells. However, it has been reported that several gastric cancer cells show resistance to TRAIL because of a scarcity of death receptor 5 (DR5) expressed on the cell surface. In this study, we show that cyclopamine sensitizes gastric cancer cells to TRAIL-induced apoptosis by elevating the expression of DR5. Interestingly, survivin hampers the existence of DR5 protein under normal conditions and cyclopamine decreases the expression of survivin, thus acting as a TRAIL sensitizer. Mechanistically, cyclopamine induces endoplasmic reticulum (ER) stress via reactive oxygen species (ROS) and CHOP, the last protein of the ER stress pathway and it regulates the proteasome degradation of survivin. Taken together, our results indicate that cyclopamine can be used for combination therapy in TRAIL-resistant gastric cancer cells.

Glioma‐derived cancer stem cells are hypersensitive to proteasomal inhibition

Although proteasome inhibitors (PIs) are used as anticancer drugs to treat various cancers, their relative therapeutic efficacy on stem cells vs. bulk cancers remains unknown. Here, we show that stem cells derived from gliomas, GSCs, are up to 1,000‐fold more sensitive to PIs (IC50, 27–70 nM) compared with their differentiated controls (IC50, 47 to »100 μM). The stemness of GSCs correlates to increased ubiquitination, whose misregulation readily triggers apoptosis. PI‐induced apoptosis of GSCs is independent of NF‐κB but involves the phosphorylation of c‐Jun N‐terminal kinase as well as the transcriptional activation of endoplasmic reticulum (ER) stress‐associated proapoptotic mediators. In contrast to the general notion that ER stress‐associated apoptosis is signaled by prolonged unfolded protein response (UPR), GSC‐selective apoptosis is instead counteracted by the UPR. ATF3 is a key mediator in GSC‐selective apoptosis. Pharmaceutical uncoupling of the UPR from its downstream apoptosis sensitizes GSCs to PIs in vitro and during tumorigenesis in mice. Thus, a combinational treatment of a PI with an inhibitor of UPR‐coupled apoptosis may enhance targeting of stem cells in gliomas.

Corrigendum to: Glioma-derived cancer stem cells are hypersensitive to proteasomal inhibition (EMBO reports, (2017), 18, 1, (150-168), 10.15252/embr.201642360)

The affiliations of Joonsung Hwang, Deric Park and Bo Yeon Kim were listed incorrectly. The authors have confirmed that JH and BYK are affiliated with World Class Institute, Anticancer Agents Research Center, Korea Research Institute of Bioscience & Biotechnology, Ochang Cheongwon, Korea. These authors have never been affiliated with Korea University Department of Neurosurgery. DP is affiliated with Neuro-Oncology Branch, CCR, NCI, National Institutes of Health in addition to the University of Virginia. The authors apologise for any inconvenience caused.

Abstract 3805: Effect of Imatinib mesylate in gastric cancer cell progression

Imatinib is a powerful tyrosine kinase inhibitor that specifically targets BCR-ABL, KIT, and PDGFR kinases that is used in the treatment of chronic myelogenous leukemia (CML), gastrointestinal stromal tumors (GIST), and other cancers. But, imatinib mesylate has not yet been reported about anti-cancer effect in gastric cancer. This study was undertaken to evaluate the in vitro effect of imatinib mesylate in gastric cancer cells and to define molecular mechanism underlying these effects. This study was to determine the expression of PDGFR molecules in gastric cancer cells (AGS, MKN28, MKN45, SNU638) by semi-quantitative polimerase chain reaction (PCR). The effects of imatinib mesylate on gastric cancer cells were examined in four human gastric cancer cell lines. The results showed expression of PDGFR in all four gastric cancer cells. We measured the sensitivity of gastric cancer cell line (AGS, MKN28, MKN45, SNU638) to imatinib mesylate using MTT assay. Cell viability of cell treated with imatinib mesylate was decreased in high dose. But cell viability was not change in high dose. Next, the results showed expression of PDGFR and suppression of its phosphorylation by imatinib mesylate in all four gastric cancer cells. Cell cycle analysis for sub-G1 and G2/M fraction also detected the increased cell death in the cells treated with imatinib mesylates. Results by Western blotting indicated that imatinib mesylates promotes apoptosis of gastric cancer cells by both activating caspase-3 and -9 and inducing PARP cleavage. And expression of p-AKT level was decreased. Cell migration and invasion that imatinib treated cells is decreased in low dose. Cell viability assay revealed that the combination of imatinib mesylate and chemo-reagent synergistically inhibited cell growth compared to cells treated with any of the agent alone. In conclusion, inhibition the PDGFR by imatinib mesylates lead to apoptosis of gastric cancer cell lines. And Imatinib suppressed motility and invasion of gastric cancer cells. The results suggest that imatinib mesylate may be useful in the treatment of gastric cancer. Note: This abstract was not presented at the meeting. Citation Format: Jung Lim Kim, Bo Ram Kim, Yoo Jin Na, Seong Hye Park, Yoon A Jeong, Sang Cheul Oh. Effect of Imatinib mesylate in gastric cancer cell progression. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3805. doi:10.1158/1538-7445.AM2015-3805

Correction: Genipin suppresses colorectal cancer cells by inhibiting the Sonic Hedgehog pathway [Oncotarget. 2017; 8:101952-101964] doi 10.18632/oncotarget.21882

[This corrects the article DOI: 10.18632/oncotarget.21882.].

Ferroptosis-inducing agents enhance TRAIL-induced apoptosis through upregulation of death receptor 5: LEE et al.

Ferroptosis is considered genetically and biochemically distinct from other forms of cell death. In this study, we examined whether ferroptosis shares cell death pathways with other types of cell death. When human colon cancer HCT116, CX‐1, and LS174T cells were treated with ferroptotic agents such as sorafenib (SRF), erastin, and artesunate, data from immunoblot assay showed that ferroptotic agents induced endoplasmic reticulum (ER) stress and the ER stress response‐mediated expression of death receptor 5 (DR5), but not death receptor 4. An increase in the level of DR5, which is activated by binding to tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL) and initiates apoptosis, was probably responsible for synergistic apoptosis when cells were treated with ferroptotic agent in combination with TRAIL. This collateral effect was suppressed in C/EBP (CCAAT‐enhancer‐binding protein)‐homologous protein (CHOP)‐deficient mouse embryonic fibroblasts or DR5 knockdown HCT116 cells, but not in p53‐deficient HCT116 cells. The results from in vitro studies suggest the involvement of the p53‐independent CHOP/DR5 axis in the synergistic apoptosis during the combinatorial treatment of ferroptotic agent and TRAIL. The synergistic apoptosis and regression of tumor growth were also observed in xenograft tumors when SRF and TRAIL were administered to tumor‐bearing mice.

Abstract 669: The regulation of ALOX15 expression in colorectal cancer to overcome the resistance to radiation therapy

Colorectal cancer (CRC) is the third most common cancer and the third leading cause of 9cancer related death9 world-wide. In case of CRC patients who have large sized tumor, radiation therapy is essential to decrease tumor size without having to eliminate the anus. However, radiation effects vary according to patients. Also, the association between genes and radiation sensitivity is still rarely researched. In this study, we elucidated that the expression level of ALOX15 regulates radiation sensitivity by TNFα signaling pathway in CRC cells. ALOX15 is known as the main metabolic enzyme for linoleic acid and arachidonic acid. Interestingly, stable cells which express low ALOX15 inhibit radiation-induced apoptosis. Mechanistically, inhibition of ALOX15 increases NF-kB under radiation therapy condition. NF-kB that plays a key role in the cellular response to DNA damage is a reason for ALOX15 to act as a radiation sensitizer. Taken together, our results indicate that ALOX15 is suggested as a prediction marker for radiation therapy. In addition, screening natural compound for elevating ALOX15 would be used for the purpose of combination therapy in radiation-resistant CRC cells. Citation Format: Yoo Jin Na, Dae-Hee Lee, Bo Ram Kim, Jung Lim Kim, So Yeon Jeong, Seong Hye Park, Min Jee Jo, Yoon A Jeong, Hye Kyeong Yun, Sang Cheul Oh. The regulation of ALOX15 expression in colorectal cancer to overcome the resistance to radiation therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 669.

Reactive oxygen species modulator-1 (Romo1) predicts unfavorable prognosis in colorectal cancer patients

Background Reactive oxygen species modulator-1 (Romo1) is a novel protein that has been reported to be crucial for cancer cell proliferation and invasion. However, its clinical implications in colorectal cancer patients are not well-known. For the first time, we investigated the association between Romo1 and the clinical outcomes of colorectal cancer patients. Study We examined Romo1 expression in resected tumor tissues immunohistochemically and assessed it with histological scores. We conducted survival analyses for patients who had curative resection (n = 190) in accordance with clinical parameters including level of Romo1 expression, and we examined the association between Romo1 expression and cell invasion using Matrigel invasion assay in colorectal cancer cells. Results We observed significantly longer mean disease-free survival in the low Romo1 group compared with the high Romo1 group (161 vs 127.6 months, p = 0.035), and the median overall survival of the low Romo1 group was significantly longer than that of the high Romo1 group (196.9 vs 171.3 months, p = 0.036). Cell invasiveness decreased in the Romo1 knockdown colorectal cancer cells in contrast to the controlled cells. Romo1 overexpression in tumor tissue was associated with a high lymph node ratio between the metastatic and examined lymph nodes (p = 0.025). Conclusions Romo1 overexpression in tumor tissue was significantly associated with survival in curatively resected colorectal cancer patients, suggesting Romo1 expression as a potential adverse prognostic marker. Increased Romo1 expression was found to be associated with high lymph node ratio. Cancer invasiveness appeared to be a key reason for the poor survival related to highly expressed Romo1.