Min Jee Jo

Molecular crosstalk between ferroptosis and apoptosis: emerging role of ER stress-induced p53-independent PUMA expression

Ferroptosis is a type of programmed cell death that depends on iron and is characterized by the accumulation of lipid peroxides. In the present study, we investigated the nature of the interplay between ferroptosis and other forms of cell death such as apoptosis. Human pancreatic cancer PANC-1 and BxPC-3 and human colorectal cancer HCT116 cells were treated with ferroptotic agents such as erastin and artesunate (ART) in combination with the apoptotic agent tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). We observed synergistic interaction of erastin or ART with TRAIL as determined by cell death assay, caspase activation, poly [ADP-ribose] polymerase 1 (PARP-1) cleavage, flow cytometry analysis, and lipid peroxidation assay. Moreover, erastin and ART induced endoplasmic reticulum (ER) stress and promoted p53 upregulated modulator of apoptosis (PUMA) expression via C/EBP-homologous protein (CHOP). Synergy of erastin/ART and TRAIL was abolished in PUMA-deficient HCT116 cells and CHOP-deficient mouse embryonic fibroblasts, but not in p53-deficient HCT116 cells. The results suggest the involvement of the p53-independent CHOP/PUMA axis in response to ferroptosis inducers, which may play a key role in ferroptotic agent-mediated sensitization to TRAIL-induced apoptosis.

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.

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.].

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.

Abstract 2254: Reactive oxygen species modulator 1 (Romo1) predicts unfavorable prognosis in colorectal cancer patients

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 (CRC) patients are not well-known. For the first time, we investigated the association between Romo1 and the clinical outcomes of CRC patients. 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 CRC cell lines. We observed significantly longer mean disease-free survival (DFS) in the low Romo1 group compared with the high Romo1 group (161 vs 127.6 months, p=0.035), and the median overall survival (OS) 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 CRC cells in contrast to the controlled cells. Romo1 overexpression in tumor tissue was associated with a high lymph node ratio (LNR) between the metastatic and examined lymph nodes (p=0.025). Romo1 overexpression in tumor tissue was significantly associated with survival in curatively resected CRC patients, suggesting Romo1 expression as a potential adverse prognostic marker. Increased Romo1 expression was found to be associated with high LNR. Cancer invasiveness appeared to be a key reason for the poor survival related to highly expressed Romo1. Citation Format: Min Jee Jo, Hong Jun Kim, Suk-Young Lee, Dae-Hee Lee, Sang Cheul Oh. Reactive oxygen species modulator 1 (Romo1) predicts unfavorable prognosis in colorectal cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2254. doi:10.1158/1538-7445.AM2017-2254