P53-independent Pathway Research Articles

Abstract 159: Frankincense essential oil and doxorubicin treatment inhibited cell proliferation and induced apoptosis in CD133+ and CD90+ subpopulation hepatocellular carcinoma cancer stem cells

Abstract Frankincense essential oil has been known in traditional medicine of many countries as wealth of health for the treatment of inflammatory diseases, anti-bacterial, anti-fungal activities, and might possess anti-cancer activities, based on their anti-proliferative and pro-apoptotic activities, but its anticancer role against cancer stem cells (CSC) in hepatocellular carcinoma (HCC) cell lines and the underlying molecular mechanisms remain uninvestigated. Doxorubicin is one of the efficient factors for HCC treatment, but the resistance to it is presenting a major obstacle for HCC treatment. The main aim of this study, isolated CD133+/CD90+ subpopulation from HCC cell line by flow cytometry, and evaluated the effects of Frankincense essential oil and Doxorubicin treatment on cell viability, colony formation, cellular proliferation, cell cycle distribution and apoptosis induction through DNA fragmentation of HCC cells and its isolated CD133+/CD90+ CSCs. Cell viability was monitored using an MTT assay. In addition, apoptosis induction was labeled by Annexin V-fluorescein isothiocyanate/propidium iodide and measured using flow cytometry. Western blotting was used to examine the protein expression of p53, Bcl-2, cyclin D1, and cleaved-caspases-3 and -9. Our results demonstrated that Frankincense essential oil or Doxorubicin suppressed the cell viability of CD133+/CD90+cells in a concentration-dependent manner after 24hrs of treatment. In addition, Frankincense essential oil or Doxorubicin induced a significant apoptosis induction in CD133+/CD90+ subpopulation cells through DNA fragmentation, caspase-9 and caspase-3 activation, increased the expression of pro-apoptotic proteins, including p53, decreased the protein level of anti-apoptotic protein Bcl-2, and regulated the expression of cell cycle regulators as cyclin D1. Levels of cyclin D1 expression were gradually suppressed by Frankincense essential oil in tested cells. Our data revealed that Frankincense essential oil has been shown to arrest cancer cells at the G1-phase of cell cycle, suppresses cyclin D1, and E, cdk 2, as well as increases expression of p21 through a p53-independent pathway. Furthermore, the Frankincense essential oil treatment strongly inhibited stemness characteristics of CSC subpopulation, colony formation and dramatically inhibited CD133+/CD90+ tumor growth in vitro. In conclusion, our results suggested that Frankincense essential oil and Doxorubicin may be a potential treatment for apoptosis induction in CSC and may provide an attractive therapeutic strategy against HCC. Citation Format: Amira S. Fyala, Ahmed S. Sultan. Frankincense essential oil and doxorubicin treatment inhibited cell proliferation and induced apoptosis in CD133+ and CD90+ subpopulation hepatocellular carcinoma cancer stem cells [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 159.

Abstract 455: Cellular response to oxaliplatin treatment shows altered DNA damage, nucleolar and ribosomal stresses as main altered pathways

Abstract Oxaliplatin is a platinum-based drug playing a critical role in the treatment of colorectal carcinoma and various Hodgkin and non-Hodgkin lymphomas. The primary mechanism of action is reported to be DNA damage and double strand breaks response. However, platinum-based drugs are usually very reactive and covalently binds not only to DNA but also to RNA, proteins or glutathione. Concerning very high reactivity of platinum compounds, we have performed whole-cell proteomic profiling on highly chemosensitive CCRF-CEM cell line to identify all possible cellular response mechanisms. For modeling of actual drug response, CCRF-CEM cell line was treated with 5 x IC50 (29.3 µM) for half-time to caspase activation (240 min). Such cells were analyzed using current high-resolution mass spectrometry. Totally, 4049 proteins were identified over three biological replicates. Among these proteins, 76 were significantly downregulated and 31 significantly upregulated in the whole experiment. Bioinformatic analysis showed nucleolar and ribosomal stress, changes in secretory, mitotic and DNA damage related proteins. These response pathways were confirmed by functional analyses and targeted experiments aimed to expression changes of selected proteins. Results observed in this experiment suggests nucleolar and ribosomal stress as the most abundant stress responses to oxaliplatin treatment at a halftime to apoptosis. Down-regulation of ribosomal proteins indicates stop of ribosome synthesis, which is one kind of response to stress. In such a case, energy saved by stopping ribosome biogenesis could be invested in solving stress conditions. Dysregulated ribosomal proteins are reported activators of p53 as well. In conclusion, oxaliplatin-induced cellular stress caused an acute response at an early stage of the experiment. Acute response stopped ribosomal biosynthesis and reduced the nucleolar size by the currently unknown mechanism. Nucleolar and ribosomal stress then triggers apoptosis in both p53 dependent and independent pathways. This work was supported by Internal Grant of Palacky University in Olomouc (LF_2016_019), Ministry of School, Education and Youth of the Czech Republic (LO1304 and LM2015064) and Technological Agency of the Czech Republic (TE02000058). Citation Format: Tomáš Oždian, Dušan Holub, Zuzana Macečková, Lakshman Varanasi, Gabriela Rylova, Jiří Rehulka, Jana Vaclavkova, Hanuš Slavík, Pavel Moudry, Pawel Znojek, Jarmila Stanková, Juan Bautista de Sanctis, Marian Hajduch, Petr Džubák. Cellular response to oxaliplatin treatment shows altered DNA damage, nucleolar and ribosomal stresses as main altered pathways [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 455.

Wasabi 6-(methylsulfinyl)hexyl isothiocyanate induces apoptosis in human colorectal cancer cells through p53-independent mitochondrial dysfunction pathway.

6-(Methylsulfinyl)hexyl isothiocyanate (6-MSITC), a major bioactive compound in Wasabi [Wasabia japonica (Miq.) Matsum.], has revealed the inhibitory effect on colon carcinogenesis in rat cancer model although the underlying mechanism is unclear. In this study, we used two types of human colorectal cancer cells (HCT116 p53+/+ and HCT116 p53-/- ) to investigate the anticancer activity and molecular mechanisms of 6-MSITC. Interestingly, 6-MSITC inhibited the cell proliferation in both types of cells with similar IC50 value although a light increase in the phosphorylation and accumulation of P53 protein was observed in HCT116 p53+/+ cells at 24 h after treatment. In addition, 6-MSITC increased the ratio of proapoptotic cells in both types of cells with the same fashion in a p53-independent manner. The data from mitochondrial analysis revealed that 6-MSITC enhanced the ratio of proapoptotic B-cell lymphoma-2-associated X protein/antiapoptotic myeloid cell leukemia 1, and sequentially caused mitochondrial membrane potential (ΔΨm ) loss, cytochrome c release, and caspase-3 activation in both types of cells. Taken together, Wasabi 6-MSITC induced apoptosis of human colorectal cancer cells in p53-independent mitochondrial dysfunction pathway. These findings suggest that 6-MSITC might be a potential agent for colon cancer chemoprevention although with p53 mutation. © 2018 BioFactors, 2018.

NFκB regulates p21 expression and controls DNA damage-induced leukemic differentiation.

DNA damage exposure is a major modifier of cell fate in both normal and cancer tissues. In response to DNA damage, myeloid leukemia cells activate a poorly understood terminal differentiation process. Here, we show that the NFκB pathway directly activates expression of the proliferation inhibitor p21 in response to DNA damage in myeloid leukemia cells. In order to understand the role of this unexpected regulatory event, we ablated the NFκB binding site we identified in the p21 promoter, using CRISPR/Cas9-mediated genome editing. We found that NFκB-mediated p21 activation controls DNA damage-induced myeloid differentiation. Our results uncover a p53-independent pathway for p21 activation involved in controlling hematopoietic cell fate.

Ganoderma applanatum secondary metabolites induced apoptosis through different pathways: In vivo and in vitro anticancer studies

Ganoderma applanatum is a widely distributed saprobic or parasitic mushroom, it was found at the bases of decaying logs in Hakozaki Higashi-ku Fukuoka-shi. Japan. The mushroom was extracted with 80% methanol, and LC-HRMS analysis was conducted to illustrate the bioactive ingredients. The cytotoxicity of the total metabolite extract was evaluated against human colon cancer cell line (Caco-2) which showed IC50 value of 160 ± 4.08 μg/ml. G. applanatum methanolic extract caused different morphological alterations and increased glutathione level in the treated cells. Interestingly, G. applanatum increased Bax/Bcl-2 ratio significantly (P ˂ 0.05) at concentrations of 80 and 160 μg/ml on Caco-2 undergoing apoptotic p53-independent pathway with lake expression of p53 protein and up-regulated Cas-3 mRNA. The in vivo study on solid Ehrlich tumor (SEC) revealed a decrease in the volume of the developed tumor mass after five days of G. applanatum (200 μg/ml) treatment. The apoptotic p53-dependant pathway was confirmed by mRNA Bax/Bcl-2 increased ratio in addition to p53 and Cas-3 up-regulation. In conclusion, G. applanatum could exert apoptotic antitumor properties in Caco-2 by p53-independent pathway and p53-dependant in SEC. The findings proved that G. applanatum can be a promising candidate as alternative or co-anticancer medications.

Ganoderma microsporum immunomodulatory protein induces apoptosis and potentiates mitomycin C-induced apoptosis in urinary bladder urothelial carcinoma cells.

Current chemotherapy and immunotherapy treatments followed by transurethral resection for urinary bladder urothelial carcinoma (UC) usually suffer from poor prognosis and high recurrence rate. Design and modification of current formulation with the novel adjuvants are needed. A recombinant protein derived from Ganoderma microsporum named as Ganoderma microsporum immunomodulatory protein (GMIP) was used to treat UC cells. We found GMIP elicits a dose-dependent and time-dependent anti-UC cell proliferation effect, with a half-maximal inhibition concentration (IC50 ) comparable to mitomycin C (MMC), a commonly used chemotherapy agent. After GMIP treatment, UC cells showed apoptotic phenomenon including cell cycle arrest in the G1 phase, elevated sub-G1 population, mitochondrial membrane potential loss, up-regulated p21 expression, p21 nuclear translocation, caspase activation, and PARP cleavage in a p53-independent but p21-mediated pathways. Unlike lung cancer cells, GMIP treated UC cells showed no autophagic scheme including Beclin-1, an autophagy to apoptosis switch marker, was not cleaved by caspase 3 and slight LC3B-II accumulation. Also, the classic autophagic inhibitor, chloroquine had no effect in GMIP-mediated cell death made us conclude that GMIP induced apoptosis through caspase activation but not autophagy in UC cells. Additionally, GMIP showed synergistic effects with MMC in killing UC cells and thus decreased the concentration of MMC usage to reach the comparable apoptotic effects. Our results delineate novel strategies for treatment of UC by GMIP alone or in combination with MMC application and provide a promising therapeutic cocktail for better treatment of urinary bladder urothelial carcinoma.

ZFP36L1 and ZFP36L2 inhibit cell proliferation in a cyclin D-dependent and p53-independent manner

ZFP36 family members include ZFP36, ZFP36L1, and ZFP36L2, which belong to CCCH-type zinc finger proteins with two tandem zinc finger (TZF) regions. Whether ZFP36L1 and ZFP36L2 have antiproliferative activities similar to that of ZFP36 is unclear. In this study, when ZFP36L1 or ZFP36L2 was overexpressed in T-REx-293 cells, cell proliferation was dramatically inhibited and the cell cycle was arrested at the G1 phase. The levels of cell-cycle-related proteins, including cyclin B, cyclin D, cyclin A, and p21, decreased; however, p53 increased in ZFP36L1-or ZFP36L2-overexpressing T-REx-293 cells. Forced expression of ZFP36L1 or ZFP36L2 also inhibited cell proliferation and cyclin D gene expression in three human colorectal cancer cell lines: HCT116 p53+/+, HCT116 p53−/−, and SW620 (mutated p53) cells. However, it increased p53 and p21 expression only in HCT116 p53+/+ cells. Knockdown of ZFP36L1 or ZFP36L2 increased cell proliferation and cyclin D expression; furthermore, the mutation of the TZF of ZFP36L1 or ZFP36L2 caused them to lose their antiproliferative ability, to the extent that they could not inhibit cyclin D expression in these three cell lines. The results indicated that ZFP36L1 and ZFP36L2 play a negative role in cell proliferation; the underlying mechanisms might be mediated through a cyclin D-dependent and p53-independent pathway.

A novel ruthenium complex with xanthoxylin induces S-phase arrest and causes ERK1/2-mediated apoptosis in HepG2 cells through a p53-independent pathway

Ruthenium-based compounds have gained great interest due to their potent cytotoxicity in cancer cells; however, much of their potential applications remain unexplored. In this paper, we report the synthesis of a novel ruthenium complex with xanthoxylin (RCX) and the investigation of its cellular and molecular action in human hepatocellular carcinoma HepG2 cells. We found that RCX exhibited a potent cytotoxic effect in a panel of cancer cell lines in monolayer cultures and in a 3D model of multicellular cancer spheroids formed from HepG2 cells. This compound is detected at a high concentration in the cell nuclei, induces DNA intercalation and inhibits DNA synthesis, arresting the cell cycle in the S-phase, which is followed by the activation of the caspase-mediated apoptosis pathway in HepG2 cells. Gene expression analysis revealed changes in the expression of genes related to cell cycle control, apoptosis and the MAPK pathway. In addition, RCX induced the phosphorylation of ERK1/2, and pretreatment with U-0126, an MEK inhibitor known to inhibit the activation of ERK1/2, prevented RCX-induced apoptosis. In contrast, pretreatment with a p53 inhibitor (cyclic pifithrin-α) did not prevent RCX-induced apoptosis, indicating the activation of a p53-independent apoptosis pathway. RCX also presented a potent in vivo antitumor effect in C.B-17 SCID mice engrafted with HepG2 cells. Altogether, these results indicate that RCX is a novel anticancer drug candidate.

Spice-derived phenolic, malabaricone B induces mitochondrial damage in lung cancer cellsviaa p53-independent pathway

The spice-derived phenolic, malabaricone B (mal B) showed selective toxicity to human lung cancer (A549), malignant melanoma (A375) and T cell leukemia (Jurkat) cell lines, without showing toxicity to human normal intestinal (INT407), human kidney (HEK293) and lung fibroblast (WI-38) cells. Among the chosen cancer cell lines, mal B showed maximum cytotoxicity to the A549 cells (IC50 = 8.1 ± 1.0 μM), which was significantly better than that of curcumin (IC50 = 26.7 ± 3.1 μM). Further morphological studies by phase contrast microscopy and a clonogenic assay of the A549 cells revealed that mal B treatment increased the number of shrinking cells and also abolished the clonal proliferation of the cells. Mal B induced apoptotic cell death was confirmed by DNA laddering and quantified by cytoplasmic oligonucleosome formation and annexin V/PI assays. The mal B-induced apoptosis was mediated by an increase in the intracellular reactive oxygen species (ROS), because the cell-permeable antioxidants, N-acetylcysteine (NAC) and PEG-SOD, strongly inhibited its cytotoxicity to the A549 cells. Mal B increased the BAX level while simultaneously decreasing the BCL-2 and BCL-XL levels in the A549 cells, triggering the mitochondrial apoptotic pathway as revealed from the release of cytochrome c, and the activation of caspase-9 and caspase-3. Pre-treatment of cells with caspase-9, caspase-3 and pan-caspase inhibitors made them more resistant to mal B treatment. This effect of mal B was strongly associated with the concomitant decrease in anti-apoptotic (IAP1, IAP2 and survivin), angiogenic (growth factors) and cancer invasiveness (matrix metalloproteinase-9, COX-2) modulating proteins. Mal B induced cytotoxicity was unaffected by the shRNA-mediated depletion of p53 in A549 cells. Most importantly, mal B sensitized a wide range of human carcinoma cells regardless of their p53 status. Finally, mal B (100 mg kg-1) also inhibited lung tumor (xenograft) growth in SCID mice.

The role of p53 pathways in radioactive iodine induced cell death in thyroid cells: Novel targets for therapy

Introduction: Radioactive iodine (RAI) use is well established in the treatment of differentiated thyroid cancers (DTC). However, the cellular mechanisms by which RAI exerts its cytotoxic effects are still unclear. The p53 gene is known to have a pivotal role in cell death following ionising radiation. Unlike in other cancers, p53 mutation is not required for the initiation of tumorgenesis in DTC. This review aims to determine the p53 dependent and independent pathways of cell death in response to radioiodine in thyroid cells. Elucidation these mechanisms will enable future development of new molecularly targeted therapies to improve the efficacy of radioiodine treatment.

Influence of Nucleostemin Expression Down-Regulation on PI3K/AKT/mTOR Signal Pathway in HL-60 Cells

To explore the effect of nucleostemin(NS) RNAi on the expression of signal molecules in PI3K/AKT/mTOR pathway, a candidate of p53-independent signal pathway in the leukemia HL-60 cells. The expression of NS was interfered by transfection of P53-deficient HL-60 cells with the recombinant lentivirus expression vector NS-RNAi-GV248. The exression of NS and signal molecules of PI3K/AKT/mTOR pathway were detected by Western blot. The fluorescence microscopy showed that the recombinant lentivirus vector NS-RNAi-GV248 transfected HL-60 cells successfully with a 80% transfection rate. Western blot showed that the expression of NS protein was inhibited obviously in HL-60 cells, and the expression levels of AKT, p-AKT, p70s6k and p-p70s6k were not statistically different(t1=2.31,P>0.05;t2=3.62,P>0.05;t3=1.60,P>0.05;t4=2.72,P>0.05) in comparison with control; the expression of GβL protein was statistically down-regnlated (t=15.01,P=0.002). The changes of GβL protein correlats with NS knockdown. The PI3K/AKT/mTOR pathway may be one of nucleostemin p53-independent signal pathways.

Betanodavirus B2 protein triggers apoptosis and necroptosis in lung cancer cells that suppresses autophagy.

The betanodavirus B2 protein targets the mitochondria and acts as a “death factor”, but its effect on lung cancer cells is unknown. We examined the effect of the B2 protein on triggering apoptosis or necroptosis via P53-dependent and P53-independent pathways and increased in suppression of autophagy. The B2 protein targets the mitochondria of A549 (P53+/+) and H1299 (P53—/—) lung cancer cells due to a specific signal sequence (41RTFVISAHAA50). This triggers generation of reactive oxygen species within the mitochondria, and a minor stress response in A549 cells, but a strong stress response in H1299 cells. We examined the molecular mechanism of this cell death pathway, and found that B2 protein induces the P53/Bax-mediated apoptotic pathway in A549 cells, and that a P53 specific inhibitor (pifithrin-α) switches this response to RIP3-mediated necroptosis. On the other hand, B2 induces RIP3-mediated necroptosis pathway in H1299 cells, and a necroptosis inhibitor (necrostatin-1) switches this response to the apoptotic pathway. Both types of cell death signals inhibited autophagy via a tightly increased balance of beclin-1 and Bcl-2. Thus, B2 protein triggers P53-dependent apoptosis in A549 cells and ROS/RIP3-mediated necroptosis in H1299 cells, and crosstalk of these pathways limits initiation of autophagy. These findings provide new insights into the possible control and treatment of lung cancer.

Piperlongumine induces G2/M phase arrest and apoptosis in cholangiocarcinoma cells through the ROS-JNK-ERK signaling pathway.

Cholangiocarcinoma (CCA) is an aggressive, metastatic bile duct cancer. CCA is difficult to diagnose, and responds poorly to current radio- and chemo-therapy. Piperlongumine (PL) is a naturally-occurring small molecule selectively toxic to cancer cells by targeting reactive oxygen species (ROS). In this study, we demonstrated the potential anticancer activity of PL in CCA. PL markedly induced death in CCA cell lines in a dose- and time-dependent manner through the activation of caspase-3 and PARP. PL also stimulated ROS accumulation in CCA. Co-exposure of PL with the ROS scavenger N-acetyl-L-cysteine or GSH completely blocked PL-induced apoptosis in CCA cell lines. Increased p21 via the p53-independent pathway in PL-treated CCA cells led to G2/M phase arrest and cell apoptosis. In addition, the study showed that PL trigger CCA cell lines death through JNK-ERK activation. Furthermore, the different antioxidant capacity of CCA cell lines also indicates the susceptibility of the cells to PL treatment. Our findings reveal that PL exhibits anti-tumor activity and has potential to be used as a chemotherapeutic agent against CCA.

The nuclear mitotic apparatus protein NuMA controls rDNA transcription and mediates the nucleolar stress response in a p53-independent manner.

The nuclear mitotic apparatus protein, NuMA, is involved in major cellular events such as DNA damage response, apoptosis and p53-mediated growth-arrest, all of which are under the control of the nucleolus upon stress. Proteomic investigation has identified NuMA among hundreds of nucleolar proteins. Yet, the precise link between NuMA and nucleolar function remains undetermined. We confirm that NuMA is present in the nucleolus and reveal redistribution of NuMA upon actinomycin D or doxorubicin-induced nucleolar stress. NuMA coimmunoprecipitates with RNA polymerase I, with ribosomal proteins RPL26 and RPL24, and with components of B-WICH, an ATP-dependent chromatin remodeling complex associated with rDNA transcription. NuMA also binds to 18S and 28S rRNAs and localizes to rDNA promoter regions. Downregulation of NuMA expression triggers nucleolar stress, as shown by decreased nascent pre-rRNA synthesis, fibrillarin perinucleolar cap formation and upregulation of p27kip1, but not p53. Physiologically relevant nucleolar stress induction with reactive oxygen species reaffirms a p53-independent p27kip1 response pathway and leads to nascent pre-rRNA reduction. It also promotes the decrease in the amount of NuMA. This previously uncharacterized function of NuMA in rDNA transcription and p53-independent nucleolar stress response supports a central role for this nuclear structural protein in cellular homeostasis.

Synergistic inhibitory effects on hepatocellular carcinoma with recombinant human adenovirus Aspp2 and oxaliplatin via p53-independent pathway in vitro and in vivo.

The present study was designed to investigate the synergistic inhibitory effects on hepatocellular carcinoma with recombinant human adenovirus Aspp2 (Aspp2-ad) and oxaliplatin via p53-independent pathway invitro and invivo. After being treated with Aspp2-ad and/or oxaliplatin for 24-48h, HepG2P53-/- and Hep3B cells showed a significant growth inhibition compared with vehicle control. Combination group showed a synergetic effect, the inhibitory rates were all above 80% at 48h point in HepG2P53-/- and Hep3B cells. The apoptotic cell numbers of Aspp2-ad and/or oxaliplatin treatment groups were increased remarkably, especially for the combined therapy group in the liver cancer cells. The Hep3B xenograft experiment also showed similar inhibition of Aspp2-ad and/or oxaliplatin to the invitro experiment. H&E results showed that combination group had the least mitotic indexes and the most necrosis. The immunohistochemistry results showed that PCNA, CD31 expression decreased greatly in treatment groups. These results suggested that Aspp2-ad might inhibit proliferation and vascular growth of hepatocarcinoma. Aspp2 induced apoptosis protein expression in Aspp2-ad and combination groups, the Aspp2, Bax and activation of caspase-3 expression increased greatly both invitro and invivo. But interestingly, the autophagy proteins showed different responses not only in HepG2P53-/- and Hep3B cells but also invitro and invivo. We found that Aspp2-ad downregulated the p-ERK, p-STAT3 expression, the synergistic effects were observed in combination group, while there was not response of mTOR to Aspp2-ad. In conclusion, Aspp2-ad, in P53-independent manner, regulated ERK and STAT3 signal moleculars to inhibit hepatocarcinoma in coordination with oxaliplatin by influencing the protein expression of proliferation, apoptosis, autophagy and vascular growth. Aspp2-ad has the potential to be developed in gene therapy for HCC, especially for P53 deletion or mutation in HCC.

The contribution of p53 and Y chromosome long arm genes to regulation of apoptosis in mouse testis.

Apoptosis of excessive or defective germ cells is a natural process occurring in mammalian testes. Tumour suppressor protein p53 is involved in this process both in developing and adult male gonads. Its contribution to testicular physiology is known to be modified by genetic background. The aim of this study was to evaluate the combined influence of the p53 and Y chromosome long arm genes on male germ cell apoptosis. Knockout of the transformation related protein 53 (Trp53) gene was introduced into congenic strains: B10.BR (intact Y chromosome) and B10.BR-Ydel (Y chromosome with a deletion in the long arm). The level of apoptosis in the testes of 19-day-old and 3-month-old male mice was determined using the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate in situ nick-end labelling (TUNEL) method. The study revealed that although p53 is involved in germ cell apoptosis in peripubertal testes, this process can also be mediated by p53-independent mechanisms. However, activation of p53-independent apoptotic pathways in the absence of the p53 protein requires engagement of the multicopy Yq genes and was not observed in gonads of B10.BR-Ydel-p53-/- males. The role of Yq genes in the regulation of testicular apoptosis seems to be restricted to the initial wave of spermatogenesis and is not evident in adult gonads. The study confirmed, instead, that p53 does participate in spontaneous apoptosis in mature testes.

Abstract 3475: Inhibitory effects of ZFP36L1 and ZFP36L2 on the cell proliferation in human colorectal cancer cells

Abstract ZFP36 family members include ZFP36 (also named TTP and TIS11), ZFP36L1 (also called BRF1, ERF1 or TIS11B) and ZFP36L2 (also called BRF2, ERF2 and TIS11D), which belong to the CCCH-type zinc finger protein with 2 tandem zinc finger region (TZF). These ZFP36 family proteins can function as RNA-binding protein through binding to AU-rich elements (AREs) in the 3’ untranslated region (3’ UTR) of mRNA, which promote the mRNA degradation or translation repression. Previously, ZFP36 has been found to inhibit cell proliferation through p53-dependent manner. In this study, we’d like to investigate whether ZFP36L1and ZFP36L2 have anti-proliferative activity as same as ZFP36 work. Tetracycline-inducible (Tet-On) system was used to induce the overexpression of ZFP36L1 or ZFP36L2 proteins in T-REx-293 cells by doxycycline (Dox) treatment. While ZFP36L1 or ZFP36L2 was overexpressed, we found that cell proliferation was dramatically inhibited, but didn’t cause cell death significantly. The importance of TZF was confirmed by using TZF mutants, and found that cell proliferation was deprived in HEK-293 cells with overexpression of ZFP36L1 mutant (C135/173R). Using western blot analysis, it was revealed that expression level of p53 protein was increased after the overexpression of ZFP36L1 or ZFP36L2 protein. Whereas, the levels of cell cycle-related proteins including cyclin B1, cyclin D1, cyclin A2 and p21 were decrease. Next, three human colorectal cancer cells HCT116 p53+/+, HCT116 p53-/- and SW620 (mutated p53) cells were used and ZFP36L1 or ZFP36L2 gene was transduced into these three cells by lentivirus. Overexpression of ZFP36L1 or ZFP36L2 also inhibited the cyclin D1 protein expression and cell proliferation in these three cells, however, increased the p53 and p21 protein expression in HCT116 p53+/+ cells, and decreased the c-Myc expression only in SW620 cells. On the other hand, knockdown of ZFP36L1 or ZFP36L2 increased cell proliferation, and mutation in TZF of ZFP36L1 (C135/173R) or ZFP36L2 (C174/212R) lost their anti-proliferative abilities in these three cells. Taken together, the results suggest that ZFP36L1 and ZFP36L2 play a negative role in cell proliferation of human colorectal cancer cells, and the underlying mechanisms might be mediated through downregulation of cyclin D1 and p53-independent pathway. Citation Format: Fat-Moon Suk, Ya-Ting Chen, Yu-Chih Liang. Inhibitory effects of ZFP36L1 and ZFP36L2 on the cell proliferation in human colorectal cancer cells [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 3475. doi:10.1158/1538-7445.AM2017-3475

Abstract 2127: p53-independent Noxa induction by cisplatin is regulated by ATF3/ATF4 in HNSCC cells

Abstract Head and neck cancer is the sixth leading cancer worldwide and head and neck squamous cell carcinoma (HNSCC) accounts for more than 90% of incident cases. The long-term prognosis of patients with advanced HNSCC has shown little improvement over the last three decades. Induction chemotherapy with platinum-based compounds, taxanes, and 5-fluorouracil is beneficial for head and neck cancer patients, but the prolonged use of chemotherapeutic drugs is limited by their toxicity and by the development of resistance. Tumor cell death induced by both conventional and targeted chemotherapy is often mediated by the BCL-2 family-dependent mitochondrial apoptotic pathway. However, initiators of this apoptotic pathway, such as p53, are frequently mutated or deleted in HNSCC rendering it refractory to treatment. To counter such resistance, direct therapeutic targeting of the BCL-2 family is conceptually appealing. We have investigated the cytotoxic effects of a DNA damaging agent, cisplatin that is used for a standard therapy for locally advanced HNSCC. Cisplatin produces anticancer effects mainly by generating DNA lesions and activating DNA damage response followed by inducing BCL-2 family-dependent mitochondrial apoptosis. Cisplatin induces the expression of a pro-apoptotic BH3-only protein, Noxa that binds to the pro-survival BCL-2 family protein, MCL-1 to inactivate its function and induces cell death. To examine the contribution of Noxa in cisplatin-induced apoptosis, shRNA for Noxa was introduced in p53-null HNSCC cells, since p53 is mutated or deleted in more than 50% of HNSCC. We found that the up-regulation of Noxa is critical for cisplatin-induced apoptosis in p53-independent HNSCC cells. This Noxa induction is regulated at the transcriptional level. Thus, we examined the regulation of the Noxa promoter with a series of luciferase reporter assays. We found that the CRE (cAMP responsive element located at -66~-59 from the transcription start site) on the promoter plays a critical role in Noxa induction. The CRE is known to be regulated by ATF/CREB transcription factors. Downregulation of ATF3 or ATF4 by shRNAs clearly reduced Noxa induction. Furthermore, the binding of these transcription factors to the CRE on the Noxa promoter was increased by cisplatin treatment, determined by chromatin-immunoprecipitation assays. In conclusion, ATF3 and ATF4 are important regulators for cisplatin-induced Noxa in a p53-independent pathway. The results suggest that modulation of the signaling pathways that activate ATF3/ATF4 could be an alternative approach to induce Noxa followed by apoptosis in HNSCC. Citation Format: Kanika Sharma, Thien-Trang Vu, Mitra Naseri, Wataru Nakajima, Kevin Zhan, Hisashi Harada. p53-independent Noxa induction by cisplatin is regulated by ATF3/ATF4 in HNSCC cells [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 2127. doi:10.1158/1538-7445.AM2017-2127

Abstract 300: Taeumjowi-tang (TJ001) induces G2/M cell cycle arrest but not apoptosis in p53-mutant prostate cancer via up-regulation of p21WAF/CIP1

Abstract Taeumjowi-tang (TJ001) is a traditional Korean medicine that usually prescribed for Tae-um person to regulate stomach-related symptoms including headache, indigestion, and jaundice. Other studies on anti-obesity effect of TJ001 have also been researched, but have never been reported as a cure for cancer. In the present study, we investigated the molecular mechanism that TJ001 induces G2/M cell cycle arrest in DU145 (p53-mutant) prostate cancer cells. The missense mutation in human p53 gene (TP53) confers oncological effect to tumor suppressor p53-mutant protein. In prostate cancer, this gain-of-function of p53-mutant is associated with androgen-independence, increased angiogenesis, and metastasis. Our in vitro studies showed that a water extract of TJ001 induced G2/M cell cycle arrest via p53-mutant status and p21WAF/CIP1 up-regulation. Conventinally, p21WAF/CIP1 is induced by mediating p53 regulation, but, in experiments, handling the p53-dependent and -independent pathway. Although serine15-phosphorylated p53 and p53 proteins remained unchanged, p21WAF/CIP1 expression is induced and cyclin B1/Cdc2 complex is inactivated by a decrease of cyclin B1. In addition, in p53-independent pathway, the level of Cdc25C expression decreased and Serine-216 phosphorylated Cdc25C increased. Generally, concomitant with G2/M cell cycle arrest come the apoptosis cell death, but in the study, prolonged G2/M cell cycle arrest developed not apoptosis but cell senescence. Therefore, our data suggest that TJ001 is helpful for p53-mutant prostate cancer treatment. Citation Format: Soo-Yeon Kang, Hyo In Kim, Se Hyang Hong, Jin Mo Ku, Kangwook Lee, Myeong-Sun Kim, Yu-jeong Choi, Chunhoo Cheon, Youme Ko, Ching Wen Huang, Yui Sasaki, Sohyeon Kang, Hye-Sook Seo, Tai Young Kim, Ji Hye Kim, Yong Cheol Shin, Seong-Gyu Ko. Taeumjowi-tang (TJ001) induces G2/M cell cycle arrest but not apoptosis in p53-mutant prostate cancer via up-regulation of p21WAF/CIP1 [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 300. doi:10.1158/1538-7445.AM2017-300

Human U3 protein 14a plays an anti-apoptotic role in cancer cells.

Human U three protein 14a (hUTP14a) binds p53 and promotes p53 degradation. Here, we report that hUTP14a plays an anti-apoptotic role in tumor cells through a p53-independent pathway. Knockdown of hUTP14a activated the intrinsic pathway of apoptosis and sensitized tumor cells to chemotherapeutic drug-induced apoptosis. In addition, the protein level of hUTP14a decreased upon chemotherapeutic drug- or irradiation-induced apoptosis. Importantly, the decrease of hUTP14a during induced apoptosis was not blocked by pan-caspase inhibitor z-VAD-FMK, indicating that the down-regulation of hUTP14a is an upstream event in apoptosis. Furthermore, ectopically expressed hUTP14a protected tumor cells from chemotherapeutic drug-induced apoptosis. In summary, our data showed that hUTP14a protected tumor cells from chemotherapeutic drug-induced apoptosis and thus might possess a potential as a target for anti-tumor therapy.