Silencing Of P53 Research Articles

Abstract 2362: NF-κB (p65) mediates interleukin-1 (IL-1) repression of androgen receptor (AR) in AR+prostate cancer (PCa) cell lines

Abstract Inflammation promotes cancer initiation and progression. The Nuclear Factor Kappa-Light-Chain-Enhancer of Activated B cells (NF-κB) family of transcription factor proteins, p65 (RelA), RelB, c-Rel, p105/p50 (NF-κB1), and p100/52 (NF-κB2), form homo- and heterodimeric complexes that mediate inflammatory cytokine signaling. We previously reported that the inflammatory cytokines, interleukin-1 alpha (IL-1α) and IL-1 beta (IL-1β), repress androgen receptor (AR) levels and activity in AR+ prostate cancer (PCa) cell lines. AR drives PCa tumorigenicity and, thus, AR is a therapeutic target. Our data suggests that IL-1 selects for ARlow/-PCa cell subpopulations that can evade AR-targeting therapy. Using RNA sequencing, we identified an IL-1-regulated gene signature predicted to supported AR-independent tumorigenicity in PCa cells. Pathway analysis of the RNA sequencing data predicted that AR is a target molecule of p65 (RELA). p50:p65 heterodimers are known to mediate IL-1 signaling, therefore, we investigated if NF-κB (p50:p65) signaling mediates IL-1 repression of AR. We found that siRNA silencing of p65 is sufficient to attenuate IL-1 repression of AR mRNA and protein levels and AR activity in AR+ PCa cell lines, while siRNA silencing of p50 had no effect on IL-1 repression of AR. Our data suggests that p65 represses AR levels, directly or indirectly, in response to IL-1. Thus, therapeutic inhibition of p65 activity could prevent the accumulation of inflammation-induced treatment-resistance ARlow/- PCa cell subpopulations. Citation Format: Shayna Elizabeth Thomas-Jardin, Haley Dahl, Monica Bautista, Freedom Ha, Joan Jacob, Afshan Fathima Nawas, Mohammed Kanshwala, Chao Xing, Nikki Delk. NF-κB (p65) mediates interleukin-1 (IL-1) repression of androgen receptor (AR) in AR+prostate cancer (PCa) cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2362.

LncRNA PLAC2 upregulates p53 to induce hepatocellular carcinoma cell apoptosis

It is known that lncRNA PLAC2 can inhibit glioma. This study explored the function of PLAC2 in hepatocellular carcinoma (HCC). Our data showed that PLAC2 expression in HCC was not affect by HCV and HBV infection, while PLAC2 levels were significantly lower in HCC tissues comparing to non-cancer tissues. Low PLAC2 levels in HCC tissues were associated with low overall 5-year survival rate. P53 mRNA was also downregulated in HCC and positively correlated with PLAC2. PLAC2 overexpression caused upregulated p53 and increase cancer cell apoptosis. P53 overexpression failed to affect PLAC2. In addition, p53 silencing reduced the effects of PLAC2 overexpression. Therefore, PLAC2 upregulated p53 to mediate cancer cell apoptosis.

4-Nonylphenol-enhanced EZH2 and RNF2 expression, H3K27me3 and H2AK119ub1 marks resulting in silencing of p21CDKN1Ain vitro.

Aim: To examine the impact of 4-nonylphenol (4-NP), on the expression of polycomb repressive complexes and cellular proliferation. Materials & methods: Cell proliferation assays, quantitative PCR, Western blotting, luciferase reporter assay, chromatin immunoprecipitation-quantitative PCR were used for the study. Results: The 4-NP at 100nM concentration significantly increased proliferation of MCF-7 cells. It enhanced the expression of RNF2-BMI1 and EZH2-SUZ12 and concomitantly increased H2AK119ub1 and H3K27me3 repressive marks at p21proximal promoter resulting in its reduced expression. Selective inhibition of RNF2 or EZH2 reverted the 4-NP action. The phospho-CREB, SP1 and E2F-1 are enriched at proximal promoter of RNF2 and EZH2 and cyclin D1, but not p21. Conclusion: The 4-NP-mediated upregulation of RNF2 and EZH2 resulted in epigenetic silencing of p21.

A novel mechanism of miRNA-mediated CBX8 associated with tumorigenesis in head and neck squamous cell carcinoma.

e17534 Background: Polycomb group (PcG) proteins influence the development and progression of cancer. However, the mechanism that contributes to tumorigenesis have not been fully understood in head and neck squamous cell carcinoma (HNSCC). Methods: The expression of chromobox 8 (CBX8), a member of the polycomb group (PcG) of proteins, on OSCC patients was determine by quantitative real-time PCR (qRT-PCR) and immunohistochemistry. Specific targeting by miRNAs was determined by software prediction, luciferase reporter assay, and correlation with target protein expression. The functions of miR-410-3p and CBX8 were accessed by transwell migration and invasion analyses using gain- and loss-of-function approaches. Results: Here we found that CBX8 is upregulated in HNSCC tissues and cell lines. Using CBX8 knockdown cDNA microarray, we identify a CBX8-mediated target gene MIPOL1 which is inversely correlated with CBX8 expression in HNSCC tissues. Ectopic expression of MIPOL1 could inhibit tumor invasion and migration, whereas MIPOL1 silencing suppressed these effects in CBX8-knockdown HNSCC cells. Otherwise, depletion of CBX8 also induced p53 activity and increased the expression level of p21 and p27 through MIPOL1-independent manner, which result in cell cycle arrest in G2M phase. Silencing of p53 could inhibit p21 and p27 accumulation in CBX8 knockdown cells. Furthermore, we demonstrated that down-regulation of miR-410-3p promoted HNSCC cells migration and invasion through directly targeting CBX8. Overexpression of miR-410-3p decreased CBX8 expression and reduced migration and invasion, while ectopic expression of CBX8 rescued the miR-410-3p-reduced migration and invasion. In clinical samples, miR-410-3p level closely inversely correlated with CBX8 and positively correlated with MIPOL1. Conclusions: Collectively, our findings indicate that miR-410-3p may act as a tumor suppressor via negatively regulating CBX8. The newly identified miR-410-3p/CBX8/MIPOL1 and miR-410-3p/CBX8/p53 signaling axes may suggest new therapeutic strategies against HNSCC.

Novel imidazo[1,2-a]pyridine inhibits AKT/mTOR pathway and induces cell cycle arrest and apoptosis in melanoma and cervical cancer cells.

The present study aimed to investigate the anti-cancer activity of imidazo[1,2-a]pyridine 5–7 in the A375 and WM115 melanoma and HeLa cervical cancer cell lines. The viability of cancer cells was analyzed by the MTT assay. Apoptosis was quantified by flow cytometry following staining of the cells with AnnexinV/propidium iodide (PI). The cell cycle was evaluated by flow cytometry after staining of cells with PI. The three compounds inhibited the proliferation of all cells for half maximal inhibitory concentration ranging from 9.7 to 44.6 µM following 48-h treatment. In addition, all cancer cells were more sensitive to compound 6 compared with the other compounds. Treatment with compound 6 induced G2/M cell cycle arrest and a significant increased level of intrinsic apoptosis in all tested cells. Furthermore, compound 6 reduced the levels of phospho (p)-protein kinase B and p-mechanistic target of rapamycin, and increased levels of the cell cycle inhibitors p53 and p21 and of the apoptosis-associated proteins BCL2 associated X protein and active caspase-9. Silencing p53 in A375 melanoma cells reduced compound 6-induced apoptosis, which suggested that compound 6 may induce p53-partially mediated apoptosis. These results demonstrated that imidazo[1,2-a]pyridines 5–7 are potential effective compounds in the treatment of melanoma and cervical cancers.

Long intergenic noncoding RNA p21 suppresses the apoptosis of hippocampus neurons in streptozotocin-diabetic mice by sponging microRNA-221 through upregulation of FOS.

Diabetes is associated with neurological complications, and accumulated evidence shows that biological pathways in diabetes are targeted by noncoding RNA transcripts. In this study, the role of long intergenic noncoding RNA (lincRNA) p21/microRNA-221 (miR-221)/fructooligosaccharide (FOS) axis was investigated in the mice with diabetes treatment. The streptozotocin-induced diabetic mouse model was established. The learning ability and the pathological changes in mice were analyzed. After that, the interaction among miR-221, lincRNA p21, and FOS was explored and verified. The subcellular location of lincRNA p21 was identified. Finally, the cell cycle and apoptosis of the hippocampus neurons were measured. In the diabetic mice, the levels of blood glucose were higher and the leaning abilities were inhibited. miR-221 was highly expressed in the diabetic mice whereas lincRNA p21 and FOS were poorly expressed. miR-221 could bind with both lincRNA p21 and FOS. miR-221 silencing or lincRNA p21 overexpression in the diabetes mice reduced the cell apoptosis rate, and the expression of Bax and cleaved Caspase-3, whereas increase the Bcl-2 expression. Overexpression of lincRNA p21 promotes FOS expression by binding to miR-221, thereby, inhibiting hippocampal neuron apoptosis in diabetic mice. This may offer potential targets for diabetes.

CXCR4 in human osteosarcoma malignant progression. The response of osteosarcoma cell lines to the fully human CXCR4 antibody MDX1338

Osteosarcoma (OS) is the most frequent primary malignant tumour of bone and metastases occur in 30% of cases, the 5-year survival rate is 25–30%.Although pre- and post-operative chemotherapy has improved prognosis in osteosarcoma (OS), high toxicity and natural and acquired drug-resistance are the first cause of treatment failure. The identification of new predictive and therapeutic biomarkers may increase drug sensitivity and better control localized and metastatic disease. By the evidence that CXCR4 receptor by binding its ligand CXCL12 activates downstream critical endpoints for tumour malignancy, we first studied human OS progression correlating CXCR4 expression in OS biopsy with patient clinical data. By Real-time PCR and immunoistochemistry we found that high levels of CXCR4 gene and protein expression significantly correlated with OS progression, emphasizing the role of CXCR4/CXCL12 axis in tumour prognosis. This was supported by univariate analyses that showed a higher probability of local and/or systemic relapse in OS patients with a high CXCR4 gene expression and a significant increase of metastasis risk associated with an increasing score of CXCR4 protein staining intensity. Secondarily, to study the role of CXCR4 as a target for new therapeutic strategies, we evaluated the response of OS cells to the fully human CXCR4 antibody, MDX1338. In the study we also included AMD3100, the most studied CXCR4 antagonist.In CXCR4-positive OS cells cultured in CXCL12-rich BM-MCS-CM (bone marrow-derived mesenchymal stem conditioned medium), a decrease of cell proliferation up to 30%–40% of control was seen after drug exposure. However, an increase of apoptosis was seen in p53-positive U2OS and 143B after CXCR4 inhibitor incubation, while no changes were seen in treated SAOS-2 cells which also present a different labeling profile. The role of p53 in apoptotic response to CXCR4 inhibitors was confirmed by p53 silencing in U2OS cell line. Our data suggest that the response to anti-CXCR4 agents could be influenced by the genetic background and labeling profile which induces a different cross-talk between tumour cells and environment. The delay in cell cycle progression associated with increased apoptosis could sensitize p53-positive cells to conventional therapy and in vivo preclinical experiments are on going with the aim to suggest new combined target therapies in human OS.

MON-316 DPYSL4 Regulates Oxygen Consumption Associating with Mitochondrial Supercomplexes

Metabolic regulatory function of p53 can play a role in maintaining homeostasis and protecting cells from damage. Here we have identified Dihydropyrimidinase-like 4 (DPYSL4) is a p53-inducible regulator of energy metabolism using RNA sequencingin both cancer cells and normal cells, such as adipocytes. DPYSL4 was localized in the mitochondria in response to DNA damage or hypoxia. Mitochondria was subjected to 2-D BN/SDS-PAGE followed by immunoblotting. DPYSL4 was detected in the same vertical position as complexes I,IIIand IV. To obtain direct evidence of a functional role in energy regulation, we examined the oxygen consumption rate (OCR) using flux analyzer. The knockdown of p53 or DPYSL4 by the CRISPR/Cas9 system showed reduction in OCR in preadipocytes. OCR of HCT116 p53+/+cellswas higher than p53-/-cells and OCR of p53 or DPYSL4 silencing were lower than p53+/+cells with treated by control siRNA. The overexpression of DPYSL4 in H1299 led to elevation of OCR and the overexpression of DPYSL4 deletion mutantdid not lead to elevation of OCR. Overexpression of DPYSL4 in H1299 cells led to a significant reduction matrigel invasion and canceled by DPYSL4 deletion mutant. In line with its loss of function in energy regulation and tumor suppressor function, DPYSL4 deletion mutant abolished its interaction with supercomplexes.Immunohistology of adipose tissues demonstrated that p53 was significantly upregulated in obese patients compared with non-obese patients. This is concomitant with marked infiltration of CD68-positive cells in adipocytes of obese patients. Taken together, these data indicate that DPYSL4 has a tumor suppressor function associated with OXPHOS regulation and may be concerned with pathogenesis of cancer and obesity regulated under p53.

MiR‑9 depletion suppresses the proliferation of osteosarcoma cells by targeting p16.

Osteosarcoma (OS) is a common primary malignancy in adolescents and children. MicroRNAs (miRNAs or miRs) can regulate the progression of OS. Herein, we explored the target genes and effects of miR-9 in OS. Cell growth, colony formation and cell cycle were respectively examined using a cell counting kit-8 (CCK-8), crystal violet staining and flow cytometry. The target gene of miR-9 was predicted according to the MicroRNA.org website. Luciferase activity was examined using a dual luciferase reporter gene assay kit. The corresponding factors levels were analyzed by carrying out reverse transcription-quantitative PCR (RT-qPCR) and western blot analysis. A mouse model of OS was also established and the volume and weight of the tumors of the mice with OS were measured. The levels of p16 in the mice with OS were detected by immunohistochemistry (IHC). The data revealed a high expression of miR-9 and a low expression of p16 in the OS tissue. p16 was found to be the target gene for miR-9 in OS. miR-9 depletion decreased the proliferation and colony formation of Saos-2 cells by arresting the cells at the G1 phase, accompanied by the downregulation of cyclin A, cyclin D1 and c-Myc expression levels. Moreover, miR-9 depletion inhibited the phosphorylation of p38, c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK). In vivo, miR-9 depletion decreased the tumor volume and weight and increased p16 expression in the mouse tumor tissues. Nevertheless, p16 silencing reversed the suppressive effects of miR-9 inhibitors on OS cells. On the whole, the findings of this study substantiate that miR-9 depletion suppresses cell proliferation by targeting p16 in OS and by mediating the activation of the ERK/p38/JNK pathway.

MiR-499-5p Attenuates Mitochondrial Fission and Cell Apoptosis via p21 in Doxorubicin Cardiotoxicity.

Doxorubicin (DOX) is a broad-spectrum anti-tumor drug, but its cardiotoxicity limits its clinical application. A better understanding of the molecular mechanisms underlying DOX cardiotoxicity will benefit clinical practice and remedy heart failure. Our present study observed that DOX caused cardiomyocyte (H9c2) apoptosis via the induction of abnormal mitochondrial fission. Notably, the expression levels of p21 increased in DOX-treated cardiomyocytes, and the silencing of p21 using siRNA greatly attenuated mitochondrial fission and apoptosis in cardiomyocytes. We also found that miR-499-5p could directly target p21 and attenuated DOX-induced mitochondrial fission and apoptosis. The role of the miR-499-5p-p21 axis in the prevention of DOX cardiotoxicity was also validated in the mice model. DOX treatment induced an upregulation of p21, which induced subsequent abnormal mitochondrial fission and myocardial apoptosis in mouse heart. Adenovirus-harboring miR-499-5p-overexpressing mice exhibited significantly reduced p21 expression, mitochondrial fission and myocardial apoptosis in hearts following DOX administration. The miR-499-5p-overexpressing mice also exhibited improved cardiomyocyte hypertrophy and cardiac function after DOX treatment. However, miR-499-5p was not involved in the DOX-induced apoptosis of cancer cells. Taken together, these findings reveal an emerging role of p21 in the regulation of mitochondrial fission program. miR-499-5p attenuated mitochondrial fission and DOX cardiotoxicity via the targeting of p21. These results provide new evidence for the miR-499-5p-p21 axis in the attenuation of DOX cardiotoxicity. The development of new therapeutic strategies based on the miR-499-5p-p21 axis is a promising path to overcome DOX cardiotoxicity as a chemotherapy for cancer treatment.

LncRNA small nucleolar RNA host gene 20 predicts poor prognosis in glioma and promotes cell proliferation by silencing P21.

BackgroundIn multiple cancers, long non-coding RNA small nucleolar RNA host gene 20 (lncRNA SNHG20) is generally dysregulated. In the present study, both the biological role and clinicopathological value of lncRNA SNHG20 in glioma are explored.MethodsReal-time PCR was employed to determine lncRNA SNHG20 expression in glioma patients. The prognostic role of expression of lncRNA SNHG20 was evaluated in a retrospective cohort study. In addition, the association between lncRNA SNHG20 expression and the clinicopathological features of glioma patients, such as tumor recurrence, survival status, follow-up time, WHO grade, resection extent, tumor location, Karnofsky performance scale score, cystic change, tumor size, gender and age, was discussed. By constructing and transfecting siRNAs that targeted lncRNA SNHG20 into the glioma U87 cells, the effects of lncRNA SNHG20 on the proliferation and cell cycle of U87 cells were assessed through cell counting kit-8, colony formation and cell cycle assays, respectively. In addition, Western blot and real-time PCR measured the expression levels of P21 and CCNA1 in U87 cells after being transfected with SNHG20 siRNA.ResultsOur results suggested the high expression of lncRNA SNHG20 in human glioma tissues compared with normal brain tissues, which was related to recurrence-free survival and poor overall survival in glioma patients. According to the existing retrospective cohort study, high lncRNA SNHG20 expression was associated with tumor size, extent of resection, WHO grade, follow-up time, survival status and recurrence. Besides, knocking down the expression of lncRNA SNHG20 could inhibit the proliferation and colony formation abilities of glioma U87 cells through cell cycle arrest. Consequently, the expression of CCNA1 was inhibited, and the expression of P21 was up-regulated in U87 cells.ConclusionA high lncRNA SNHG20 expression level predicts the poor prognosis for glioma patients. Moreover, lncRNA SNHG20 can promote glioma proliferation through silencing P21 and thus lncRNA SNHG20 is an independent potential prognostic biomarker for glioma patients.

Determining if Double Gene Knockdown of P65 and PDK2 Increases Cytotoxicity and Radiation Sensitivity of Pancreatic Cancer Cells

Background: Pancreatic ductal adenocarcinoma (PDA) is currently the 4th leading cause of cancer death in the US because of late detection and resistance to chemotherapy and radiation. This tumor resistance is partially due to high activity of the transcription factor, NF-[Symbol]B which promotes cell survival and pyruvate dehydrogenase kinase 2 (PDK2) which regulates aerobic glycolysis (Warburg Metabolism), cell proliferation, and inhibition of apoptosis. We have shown that simultaneous treatment with the chemical NF-B inhibitor DMAPT and the Warburg inhibitor DCA is cytotoxic and enhances radiation-induced cell death in human PDA cells. 
 Experimental Design: We hypothesize that double gene knockdown of the P65 subunit of NF-[Symbol]B and PDK2 by siRNA will lead to increased cytotoxicity and radiation sensitivity. The PDA cell line (Mia PaCa-2) was utilized and was transfected with appropriate siRNAs. The cells were plated and followed by irradiation with either 0, 2, 4, or 6 Gy of 160 kVp X-rays. 
 Results: Analysis of Western blots shows the successful silencing of P65, but the knockdown of PDK2 are pending. The differences in plating efficiency were not found to be statistically significant between the treatment groups. The differences in survival fraction were not found to be statistically significant at 2, 4, or 6 Gy, but there is a trend for enhancement at 6 Gy. 
 Conclusion: Preliminary data indicate there was no increase in cytotoxicity or radiation-induced cell killing after treatment with SiP65, SiPDK2, or both. However, to date we have no evidence that siPDK2 is working and further experiments are underway.

CELF1/p53 axis: a sustained antiproliferative signal leading to villus atrophy under total parenteral nutrition.

Intestinal villus atrophy is a major complication of total parenteral nutrition (TPN). Our previous study revealed that TPN-induced villus atrophy is accompanied by elevated expression of CUGBP, Elav-like family member 1 (CELF1); however, its mechanism of action has not been fully understood. Herein, we report a pivotal role of CELF1/p53 axis, which induces a sustained antiproliferative signal, leading to suppressed proliferation of intestinal epithelial cells (IECs). By using a rat model of TPN, we found synchronous upregulation of CELF1 and p53 in jejunum mucosa, accompanied by a 51% decrease in crypt cell proliferation rate. By using HCT-116 cells as an IEC model in vitro, we found that the expression of CELF1 altered dynamically in parallel to proliferation rate, suggesting a self-adaptive expression pattern in IECs in vitro. Furthermore, ectopic overexpression of CELF1 elicited a significant antiproliferative effect in HCT-116, Caco-2, and IEC-6 cells, whereas knockdown of CELF1 elicited a significant proproliferative effect. Moreover, cell-cycle assay revealed that ectopic overexpression of CELF1 induced sustained G2 arrest and G1 arrest in HCT-116 and IEC-6 cells, respectively, which could be abolished by p53 silencing. Mechanistically, polysomal profiling and nascent protein analysis revealed that regulation of p53 by CELF1 was mediated through accelerating its protein translation in polysomes. Taken together, our findings revealed a sustained suppression of IEC proliferation evoked by CELF1/p53 axis, which may be a potential therapeutic target for the treatment of TPN-induced villus atrophy.-Yan, J.-K., Zhang, T., Dai, L.-N., Gu, B.-L., Zhu, J., Yan, W.-H., Cai, W., Wang, Y. CELF1/p53 axis: a sustained antiproliferative signal leading to villus atrophy under total parenteral nutrition.

Differential involvement of TAK1, RIPK1 and NF-κB signaling in Smac mimetic-induced cell death in breast cancer cells.

Smac mimetics (SMs) are considered promising cancer therapeutics. However, the mechanisms responsible for mediating cell death by SMs are still only partly understood. Therefore, in this study, we investigated signaling pathways upon treatment with the bivalent SM BV6 using two SM-sensitive breast cancer cell lines as models. Interestingly, genetic silencing of transforming growth factor (TGF)β activated kinase (TAK)1, an upstream activator of the nuclear factor-kappaB (NF-κB) subunit RelA (p65), increased BV6-induced cell death only in EVSA-T cells, although it reduced BV6-mediated upregulation of tumor necrosis factor (TNF)α in both EVSA-T and MDA-MB-231 cells. By comparison, genetic silencing of p65, a key component of canonical NF-κB signaling, blocked BV6-induced cell death in MDA-MB-231 but not in EVSA-T cells. Similarly, knockdown of NF-κB-inducing kinase (NIK) rescued MDA-MB-231 cells from BV6-induced cell death, while it failed to do so in EVSA-T cells. Consistently, silencing of p65 or NIK reduced BV6-stimulated upregulation of TNFα in MDA-MB-231 cells. In conclusion, TAK1, receptor-interacting kinase 1 (RIPK1) as well as canonical and non-canonical NF-κB signaling are differentially involved in SM-induced cell death in breast cancer cells. These findings contribute to a better understanding of SM-induced signaling pathways.

Generation of Fanconi Anemia iPSC Clones By Addition of a Small Molecule Inhibitor of p53 during Reprogramming

Fanconi anemia (FA) is an inherited bone marrow failure syndrome characterized by loss of function mutations in any of at least 22 FANC genes that are critical for DNA repair. Progressive loss of hematopoietic stem/progenitor cells (HSPCs) in FA patients has been attributed in part to a heightened p53/p21 axis that restricts the cell cycle to G0/G1 in response to accumulation of unresolved DNA damage and replicative stress. Silencing of p53 was previously shown to rescue HSPC defects in FA models in vitro and in vivo. Due to insufficient numbers of primary HSPCs in FA for disease modeling and cell therapies, the concept of generating induced pluripotent stem cells (iPSCs) from an individual patient, and differentiating the FA-iPSCs into a theoretically infinite supply of autologous HSPCs arose. However, reprogramming FA cells has proven to be challenging and mostly dependent on hypoxic culture conditions or genetic complementation of the defect by integrating lentiviral vectors expressing a normal FANC gene. A recent study reported low-efficiency generation of integration-free FA-iPSCs by electroporation of fibroblasts with episomal plasmid vectors expressing both reprogramming factors and p53 shRNA. Here we sought to develop an improved and streamlined reprogramming strategy for FA by transduction of readily accessible FA mononuclear cells (MNCs) with commercially available non-integrating reprogramming Sendai Viruses (SeV2), combined with a more adaptable inhibition of the p53 pathway by addition of variable concentrations of a small molecule during reprogramming. Approximately 100,000 MNCs from an FA patient with confirmed biallelic mutations in FANCA were cultured for 10 days under hypoxic conditions (5% O2) favoring either myeloid or erythroid expansion. While myeloid cultures led to minimal proliferation of FA MNCs, we observed a 6-fold increase in total cell numbers in the presence of EPO. Erythroid-expanded FA cells were transduced with SeV2 harboring four standard reprogramming transcription factors (SOX2, OCT4, KLF4 and c-MYC). Cells were subsequently cultured under hypoxia for at least 30 days in a reprogramming cocktail supplemented or not with 0.3uM, 0.6µM or 1.2µM cyclic pifthrin-α (cPFT), a reversible small molecule inhibitor of p53-dependent gene transcription. In the absence of cPFT, no FA-iPSC clones were obtained, consistent with reported reprogramming barriers in FA cells. In contrast, several iPSC colonies were generated with cPFT-treated FA cells, albeit at much slower kinetics (~30 days) compared to MNCs without FA mutations (~20 days). The overall efficiency of reprogramming was ~0.01%, with a trend toward enhanced efficiencies in cultures containing the highest concentration of cPFT (1.2µM). To investigate the need for p53 inhibition beyond the reprogramming period, half of the FA-iPSC clones were passaged and further cultured in 5% O2 with cPFT 1.2µM, whereas the remaining clones were similarly treated but without p53 inhibitor. None of the FA-iPSC clones that were maintained in cPFT-containing cultures following reprogramming survived further passaging. In contrast, when cPFT was removed after reprogramming, all iPSC clones could stably undergo repeated passages provided that hypoxia (5% O2) was maintained. The FA-iPSC clones expressed high levels alkaline phosphatase and were TRA 1-60- and NANOG-positive, preliminarily validating their pluripotent nature. Karyotyping, trilineage differentiation, and in vivo teratoma assays are ongoing. Overall, this study provides a practical approach for successful reprogramming of FA peripheral blood cells based on commercially available non-integrating SeV2 reprogramming strategies supplemented with p53 inhibition. Regulated addition of variable concentrations of a small molecule inhibitor of p53 at various steps of the reprogramming process will allow further enhancement of reprogramming efficiencies in FA. DisclosuresNo relevant conflicts of interest to declare.

The Effect of Flubendazole on Adhesion and Migration in SW480 and SW620 Colon Cancer Cells.

Colon cancer is the most common type of gastrointestinal cancer. Despite advances during the last two decades, the efficacy of colorectal cancer treatment is still insufficient and new anticancer agents are necessary. In our study, colon cancer cells derived from a primary tumor (SW480) and lymph node metastasis (SW620) from the same patient were used and compared. The effect of flubendazole (FLU) on cell adhesion and migration was monitored using the x-CELLigence Real-Time Cell Analysis system. Expressions of molecules involved in adhesion and migration were analyzed using RT-PCR and western blot. Furthermore, RNA silencing of nuclear factor-κB in SW620 cells was used to determine the involvement of the NF-κB p65 regulation pathway in FLU action. FLU significantly suppressed the adhesion of SW480 cells and reduced the expression of adhesion markers (ICAM-1, αE-catenin; β-catenin; integrin α5 and β1). Moreover, a significant anti-migratory potential of FLU was manifested in the SW620 cells. In addition, FLU suppressed the phosphorylation of NF-κB p65 and potentiated the suppression of several metastatic markers (ICAM-1, EpCAM, integrin α5, β1, α-tubulin) caused by NF-κB p65 silencing. FLU has a significant anti-migratory effect in intestinal cancer cell SW480 and its lymph node metastatic cells SW620. FLU decreases the expression of some proteins involved in metastatic processes and inhibits activation of NF-κB p65.

A novel all-trans retinoic acid derivative inhibits proliferation and induces apoptosis of myelodysplastic syndromes cell line SKM-1 cells via up-regulating p53

Myelodysplastic syndromes (MDS) are a varied set of hematologic neoplasms and a high risk of progression to acute myeloid leukemia (AML). 4-Amino-2-trifluoromethyl-phenyl retinate (ATPR), a novel all-trans retinoic acid (ATRA) derivative, play an important role in various types of cancer cells as a tumor inhibitor. However, little is known concerning its antitumor effect on MDS. The cell viability and the percentage of apoptotic cells were used to measure MTT, Flow Cytometry and Hoechst 33342/PI staining. In addition, real-time quantitative RT-PCR (qRT-PCR) and western blotting were used to analyzed the expression of p53, as well as the levels of BNIP3, apoptosis proteins of Caspase-3, BAX and BCL-2. After SKM-1 cells were incubated with DAC, ATRA and ATPR, the viability of the SKM-1 cells was inhibited in a dose- and time-dependent manner. Both Hoechst staining and flow cytometry showed the apoptosis of SKM-1 cells was increased. Moreover, SKM-1 cells treated with ATPR unveiled elevated mRNA and protein levels of p53, BNIP3, BAX and Caspase-3 expression and decreased BCL-2 expression. However, silencing p53 suppressed the pro-apoptosis function of ATPR. Consequently, these data provide the first evidence for ATPR increased apoptosis in SKM-1 cells by p53 that is mutually dependent on and obligatorily linked to BNIP3 gene activation.

Quinaldic acid induces changes in the expression of p53 tumor suppressor both on protein and gene level in colon cancer LS180 cells.

Origin, synthesis and activity of quinaldic acid (QA), proposed derivative of kynurenic acid, have been poorly studied to date. Previously, we have demonstrated the antiproliferative effect of QA in a colon cancer model in vitro. The goal of present study was to verify QA activity to modify the expression of p53 tumor suppressor in colon cancer cells, and to relate it to its cancer cell growth inhibiting activity in vitro. LS180 colon cancer cells possessing the wild type form of p53 were used in the study. Real-time PCR and immunobloting techniques were used to test the expression of p53 at gene and protein level, respectively. Next, immunocytochemistry was used to visualize the localization of p53 protein within the cells. Furthermore, the antiproliferative activity of QA was retested in cells with siRNA silenced P53 gene. The activity of QA to modify both the expression and phosphorylation of p53 protein as well as the level of P53 gene is shown. Concomitantly, the nuclear and cytoplasmic localization of phospho-p53 protein upon QA treatment is also presented. Moreover, reduced activity of QA in colon cancer cells with silenced p53 expression is observed. QA affects the expression of p53 tumor suppressor, both at gene and protein level. The prominent contribution of p53 to the antiproliferative effect of QA in LS180 colon cancer cells can be suggested.

Forcing ATGL expression in hepatocarcinoma cells imposes glycolytic rewiring through PPAR-\u03b1/p300-mediated acetylation of p53

Metabolic reprogramming is a typical feature of cancer cells aimed at sustaining high-energetic demand and proliferation rate. Here, we report clear-cut evidence for decreased expression of the adipose triglyceride lipase (ATGL), the first and rate-limiting enzyme of triglyceride hydrolysis, in both human and mouse-induced hepatocellular carcinoma (HCC). We identified metabolic rewiring as major outcome of ATGL overexpression in HCC-derived cell lines. Indeed, ATGL slackened both glucose uptake/utilization and cell proliferation in parallel with increased oxidative metabolism of fatty acids and enhanced mitochondria capacity. We ascribed these ATGL—downstream events to the activity of the tumor-suppressor p53, whose protein levels—but not transcript—were upregulated upon ATGL overexpression. The role of p53 was further assessed by abrogation of the ATGL-mediated effects upon p53 silencing or in p53-null hepatocarcinoma Hep3B cells. Furthermore, we provided insights on the molecular mechanisms governed by ATGL in HCC cells, identifying a new PPAR-α/p300 axis responsible for p53 acetylation/accumulation. Finally, we highlighted that ATGL levels confer different susceptibility of HCC cells to common therapeutic drugs, with ATGL overexpressing cells being more resistant to glycolysis inhibitors (e.g., 2-deoxyglucose and 3-bromopyruvate), compared to genotoxic compounds. Collectively, our data provide evidence for a previously uncovered tumor-suppressor function of ATGL in HCC, with the outlined molecular mechanisms shedding light on new potential targets for anticancer therapy.

P53 Silencing and Mammosphere Formation in Breast Cancer Cells Harbouring P53 Gain-of-Function Mutations Trigger Epithelial-Mesenchymal Transition

Background: Mutations in p53 gene are observed in ∼50% of all human cancers. In breast cancer alone, 12%-32% of luminal, 84% of basal-like and 75% of HER-2 expressing tumors have apparent p53 mutations. Tumor cells undergo epithelial-mesenchymal transition (EMT) to metastasise from primary sites to form secondary tumors at distant regions of the body. EMT is a complex biologic phenomenon which governs the transition of cancer cells with epithelial characteristics to mesenchymal traits, gaining new properties such as aggressiveness and invasiveness. Recent studies revealed that mutations in the p53 gene can give rise to alternate functional phenotypes leading to tumor initiation and progression. Aim: The aim of this study is to develop a robust human breast cancer cellular model to investigate p53 gain-of-function (GOF) mutations and EMT as well as evaluating the EMT phenotype associated with these mutations. Methods: Two breast cancer cell lines, namely MDA-MB-468 and HCC38 carrying the R273H and R273L missense mutations, respectively, were subjected to p53 knockdown using shRNA directed against p53 gene through lentiviral vector transduction. The transduced cells were then harvested for Western blotting to evaluate the protein expression of EMT markers which includes E-cadherin, SNAIL, ZEB1 and vimentin compared with the nontransduced control cells. Subsequently, both cell lines were subjected to mammosphere generation and redifferentiation to determine the basal expression of the EMT markers. Results: Silencing of p53 using siRNA in MDA-MB-468 and HCC38 downregulated E-cadherin expressions but upregulated vimentin levels. Furthermore, E-cadherin levels reduced significantly after conversion from adherent parental cells to mammospheres, but rebound upon redifferentiation. Conversely, vimentin was upregulated in mammospheres as compared with the parental and redifferentiated groups. Conclusion: p53 knockdown in breast cancer cells harboring R273H and R273L mutations favor vimentin expression but not E-cadherin, suggesting that p53-GOF mutants are involved in EMT and the development of metastatic tumors. The mammosphere model accurately recapitulates cell plasticity between epithelial and mesenchymal states, as evidenced by the expression of mesenchymal cell markers in the mammospheres, and epithelial cell markers in adherent and redifferentiated cells.