Miyong Yun

Umbilical cord tissue-derived mesenchymal stem cells induce apoptosis in PC-3 prostate cancer cells through activation of JNK and downregulation of PI3K/AKT signaling

IntroductionAlthough mesenchymal stem cells (MSCs) have antitumor potential in hepatocellular carcinoma and breast cancer cells, the antitumor mechanism of human umbilical cord mesenchymal stem cells (hUCMSCs) in prostate cancer cells still remains unclear. Thus, in the present study, we elucidated the antitumor activity of hUCMSCs in PC-3 prostate cancer cells in vitro and in vivo.MethodshUCMSCs were isolated from Wharton jelly of umbilical cord and characterized via induction of differentiations, osteogenesis, and adipogenesis. Antitumor effects of UCMSCs on tumor growth were evaluated in a co-culture condition with PC-3 prostate cancer cells. PC-3 cells were subcutaneously (sc) injected into the left flank of nude mice, and UCMSCs were sc injected into the right flank of the same mouse.ResultsWe found that hUCMSCs inhibited the proliferation of PC-3 cells in the co-culture condition. Furthermore, co-culture of hUCMSCs induced the cleavage of caspase 9/3 and PARP, activated c-jun NH2-terminal kinase (JNK), and Bax, and attenuated the phosphorylation of phosphatidylinositol 3-kinase (PI3K)/ AKT, extracellular signal-regulated kinase (ERK), and the expression of survival genes such as Bcl-2, Bcl-xL, Survivin, Mcl-1, and cIAP-1 in PC-3 cells in Western blotting assay. Conversely, we found that treatment of specific JNK inhibitor SP600125 suppressed the cleavages of caspase 9/3 and PARP induced by hUCMSCs in PC-3 cells by Western blotting and immunofluorescence assay. The homing of hUCMSCs to, and TUNEL-positive cells on, the K562 xenograft tumor region were detected in Nu/nu-BALB/c mouse.ConclusionsThese results suggest that UCMSCs inhibit tumor growth and have the antitumor potential for PC-3 prostate cancer treatment.

Melatonin Sensitizes H1975 Non-Small-Cell Lung Cancer Cells Harboring a T790M-Targeted Epidermal Growth Factor Receptor Mutation to the Tyrosine Kinase Inhibitor Gefitinib

Background/Aims: The use of tyrosine kinase inhibitors (TKIs) to target active epidermal growth factor receptor (EGFR)-harbouring mutations has been effective in patients with advanced non-small-cell lung cancer (NSCLC). However, the use of TKIs in NSCLS patients with somatic EGFR mutations, particularly T790M, causes drug resistance. Thus, in the present study, we investigated overcoming resistance against the TKI gefitinib by combination treatment with melatonin in H1975 NSCLC cells harbouring the T790M somatic mutation. Methods: H1975 and HCC827 cells were treated with melatonin in combination with gefitinib, and cell viability, cell cycle progression, apoptosis, and EGFR, AKT, p38, Bcl-2, Bcl-xL, caspase 3 and Bad protein levels were examined. Results: Treatment with melatonin dose-dependently decreased the viability of H1975 cells harbouring the T790M somatic mutation compared to HCC827 cells with an EGFR active mutation. Melatonin-mediated cell death resulted in decreased phosphorylation of EGFR and Akt, leading to attenuated expression of survival proteins, such as Bcl-2, Bcl-xL and survivin, and activated caspase 3 in H1975 cells, but not in HCC827 cells. However, we did not observe a significant change in expression of cell cycle proteins, such as cyclin D, cyclin A, p21 and CDK4 in H1975 cells. Surprisingly, co-treatment of gefitinib with melatonin effectively decreased the viability of H1975 cells, but not HCC827 cells. Moreover, co-treatment of H1975 cells caused consistent down-regulation of EGFR phosphorylation and induced apoptosis compared to treatment with gefitinib or melatonin alone. Conclusions: Our findings demonstrate that melatonin acts as a potent chemotherapeutic agent by sensitising to gefitinib TKI-resistant H1975 cells that harbour a EGFR T790M mutation.

Cinnamaldehyde Derivative (CB-PIC) Sensitizes Chemo-Resistant Cancer Cells to Drug-Induced Apoptosis via Suppression of MDR1 and its Upstream STAT3 and AKT Signalling

Background/Aims: Our group reported that cinnamaldehyde derivative, (E)-4-((2-(3-oxopop-1-enyl)phenoxy)methyl)pyridinium malonic acid (CB-PIC) induced apoptosis in hypoxic SW620 colorectal cancer cells via activation of AMP-activated protein kinase (AMPK) and extracellular signal regulated kinase (ERK). Herein, sensitizing effect of CB-PIC was investigated in resistant cancer cells such as paclitaxel (PT) resistant lung cancer cells (H460/PT), and Adriamycin (Adr) resistant breast cancer (MCF7/Adr) and colon cancer (HCT15/cos) cells. Methods: Various drug resistant cell lines were treated with CB-PIC, and the signalling pathway and functional assay were explored by Western blot, Rhodamine assay, FACS, RT-PCR and MTT assay. Results: We found that CB-PIC effectively exerted cytotoxicity, increased sub G1 population and the cleaved form of poly (ADP-ribose) polymerase (PARP) and caspase 9 in drug resistant cancer cells. Furthermore, CB-PIC sensitized resistant cancer cells to adriamycin via downregulation of survival proteins such as survivin, Bcl-xL and Bcl-2, along with MDR1 suppression leading to accumulation of drug in the intracellular region. Of note, CB-PIC transcriptionally decreased MDR1 expression via suppression of STAT3 and AKT signalling in three resistant cancer cells with highly expressed P-glycoprotein. Nonetheless, CB-PIC did not affect transport activity of P-glycoprotein in a short time efflux assay, while epigallocatechin gallate (EGCG) accumulated Rhodamine 123 into intracellular region of cell by direct inhibition of MDR1 transport activity. Conclusions: These data demonstrate that CB-PIC suppresses the P-glycoprotein expression through inhibition of STAT3 and AKT signalling to overcome drug resistance in chemo-resistant cancer cells as a potent chemotherapeutic sensitizer.

Apoptosis Induced by Tanshinone IIA and Cryptotanshinone Is Mediated by Distinct JAK/STAT3/5 and SHP1/2 Signaling in Chronic Myeloid Leukemia K562 Cells

Though tanshinone IIA and cryptotanshinone possess a variety of biological effects such as anti-inflammatory, antioxidative, antimetabolic, and anticancer effects, the precise molecular targets or pathways responsible for anticancer activities of tanshinone IIA and cryptotanshinone in chronic myeloid leukemia (CML) still remain unclear. In the present study, we investigated the effect of tanshinone IIA and cryptotanshinone on the Janus activated kinase (JAK)/signal transducer and activator of transcription (STAT) signaling during apoptotic process. We found that both tanshinone IIA and cryptotanshinone induced apoptosis by activation of caspase-9/3 and Sub-G1 accumulation in K562 cells. However, they have the distinct JAK/STAT pathway, in which tanshinone IIA inhibits JAK2/STAT5 signaling, whereas cryptotanshinone targets the JAK2/STAT3. In addition, tanshinone IIA enhanced the expression of both SHP-1 and -2, while cryptotanshinone regulated the expression of only SHP-1. Both tanshinone IIA and cryptotanshinone attenuated the expression of bcl-xL, survivin, and cyclin D1. Furthermore, tanshinone IIA augmented synergy with imatinib, a CML chemotherapeutic drug, better than cryptotanshinone in K562 cells. Overall, our findings suggest that the anticancer activity of tanshinone IIA and cryptotanshinone is mediated by the distinct the JAK/STAT3/5 and SHP1/2 signaling, and tanshinone IIA has the potential for combination therapy with imatinib in K562 CML cells.

Melatonin Suppresses the Expression of 45S Preribosomal RNA and Upstream Binding Factor and Enhances the Antitumor Activity of Puromycin in MDA-MB-231 Breast Cancer Cells

Since the dysregulation of ribosome biogenesis is closely associated with tumor progression, in the current study, the critical role of ribosome biogenesis related signaling was investigated in melatonin and/or puromycin induced apoptosis in MDA-MB-231 breast cancer cells. Despite its weak cytotoxicity, melatonin from 3 mM attenuated the expression of 45S pre-ribosomal RNA (pre-rRNA), UBF as a nucleolar transcription factor, and fibrillarin at mRNA level and consistently downregulated nucleolar proteins such as UBF and fibrillarin at protein level in MDA-MB-231 cells. Furthermore, immunofluorescence assay revealed that UBF was also degraded by melatonin in MDA-MB-231 cells. In contrast, melatonin attenuated the expression of survival genes such as Bcl-xL, Mcl-1, cyclinD1, and cyclin E, suppressed the phosphorylation of AKT, mTOR, and STAT3, and cleaved PARP and activated caspase 3 only at a high concentration of 12 mM. However, combined treatment of melatonin (3 mM) and puromycin (1 μM) synergistically inhibited viability, attenuated the expression of 45S pre-rRNA and UBF, and consistently downregulated UBF, XPO1 and IPO7, procaspase 3, and Bcl-xL in MDA-MB 231 cells. Overall, these findings suggest that melatonin can be a cancer preventive agent by combination with puromycin via the inhibition of 45S pre-rRNA and UBF in MDA-MB 231 breast cancer cells.

Activation of AMP‐activated Protein Kinase and Phosphorylation of Glycogen Synthase Kinase3 β Mediate Ursolic Acid Induced Apoptosis in HepG2 Liver Cancer Cells

Despite the antitumour effect of ursolic acid observed in several cancers, the underlying mechanism remains unclear. Thus, in the present study, the roles of AMP‐activated protein kinase (AMPK) and glycogen synthase kinase 3 beta (GSK3β) were examined in ursolic acid induced apoptosis in HepG2 hepatocellular carcinoma cells. Ursolic acid significantly exerted cytotoxicity, increased the sub‐G1 population and the number of ethidium homodimer and terminal deoxynucleotidyl transferase(TdT) mediated dUTP nick end labeling positive cells in HepG2 cells. Also, ursolic acid enhanced the cleavages of poly‐ADP‐ribose polymerase (PARP) and caspase3, attenuated the expression of astrocyte elevated gene (AEG1) and survivin in HepG2 cells. Interestingly, ursolic acid increased the phosphorylation of AMPK and coenzyme A carboxylase and also enhanced phosphorylation of GSK3β at inactive form serine 9, whereas ursolic acid attenuated the phosphorylation of AKT and mTOR in HepG2 cells. Conversely, AMPK inhibitor compound C or GSK3β inhibitor SB216763 blocked the cleavages of PARP and caspase 3 induced by ursolic acid in HepG2 cells. Furthermore, proteosomal inhibitor MG132 suppressed AMPK activation, GSK3β phosphorylation, cleaved PARP and deceased AEG‐1 induced by ursolic acid in HepG2 cells. Overall, our findings suggest that ursolic acid induced apoptosis in HepG2 cells via AMPK activation and GSK3β phosphorylation as a potent chemopreventive agent. Copyright

Ginkgetin induces apoptosis via activation of caspase and inhibition of survival genes in PC-3 prostate cancer cells

Ginkgetin is a natural biflavonoid isolated from leaves of Ginkgo biloba L. Though it was known to have anti-inflammatory, anti-influenza virus, anti-fungal activity, osteoblast differentiation stimulating activity and neuro-protective effects, the underlying antitumor mechanism of ginkgetin still remains unclear. Thus, in the present study, anti-cancer mechanism of ginkgetin was elucidated in human prostate cancer PC-3 cells. Ginkgetin suppressed the viability of PC-3 cells in a concentration-dependent manner and also significantly increased the sub-G1 DNA contents of cell cycle in PC-3 cells. Ginkgetin activated caspase-3 and attenuated the expression of survival genes such as Bcl-2, Bcl-xL, survivin and Cyclin D1 at protein and mRNA levels. Consistently, pan-caspase inhibitor Z-DEVD-fmk blocked sub G1 accumulation and cleavages of PRAP and caspase 3 induced by ginkgetin in PC-3 cells. Overall, these findings suggest that ginkgetin induces apoptosis in PC-3 cells via activation of caspase 3 and inhibition of survival genes as a potent chemotherapeutic agent for prostate cancer treatment.

TRAIP/RNF206 is required for recruitment of RAP80 to sites of DNA damage

RAP80 localizes to sites of DNA insults to enhance the DNA-damage responses. Here we identify TRAIP/RNF206 as a novel RAP80-interacting protein and find that TRAIP is necessary for translocation of RAP80 to DNA lesions. Depletion of TRAIP results in impaired accumulation of RAP80 and functional downstream partners, including BRCA1, at DNA lesions. Conversely, accumulation of TRAIP is normal in RAP80-depleted cells, implying that TRAIP acts upstream of RAP80 recruitment to DNA lesions. TRAIP localizes to sites of DNA damage and cells lacking TRAIP exhibit classical DNA-damage response-defect phenotypes. Biochemical analysis reveals that the N terminus of TRAIP is crucial for RAP80 interaction, while the C terminus of TRAIP is required for TRAIP localization to sites of DNA damage through a direct interaction with RNF20–RNF40. Taken together, our findings demonstrate that the novel RAP80-binding partner TRAIP regulates recruitment of the damage signalling machinery and promotes homologous recombination.

Generation of ROS by Decursin selectively induces the ER stress pathway components ATF4/PERK leading to the synergistic enhancement of TRAIL‐induced apoptosis

The TNF‐related apoptosis‐inducing ligand (TRAIL) is a promising anticancer agent due to its remarkable ability to selectively kill tumour cells. However, because most tumours exhibit resistance to TRAIL‐induced apoptosis, the development of combination therapies to overcome resistance to TRAIL is required for effective cancer therapy.

Decursin enhances TRAIL-induced apoptosis through oxidative stress mediated- endoplasmic reticulum stress signalling in non-small cell lung cancers.

The TNF‐related apoptosis‐inducing ligand (TRAIL) is a promising anticancer agent due to its remarkable ability to selectively kill tumour cells. However, because most tumours exhibit resistance to TRAIL‐induced apoptosis, the development of combination therapies to overcome resistance to TRAIL is required for effective cancer therapy.