Levels Of p21Cip1 Research Articles

Mortalin (GRP75/HSPA9) Promotes Survival and Proliferation of Thyroid Carcinoma Cells.

We previously reported that upregulation of mortalin (HSPA9/GRP75), the mitochondrial HSP70 chaperone, facilitates tumor cell proliferation and survival in human medullary thyroid carcinoma (MTC), proposing mortalin as a novel therapeutic target for MTC. In this report, we show that mortalin is also upregulated in other thyroid tumor types, including papillary thyroid carcinoma (PTC), follicular thyroid carcinoma (FTC), and anaplastic thyroid carcinoma (ATC), and that mortalin depletion can effectively induce growth arrest and cell death in human PTC (TPC-1), FTC (FTC133), and ATC (8505C and C643) cells in culture. Intriguingly, mortalin depletion induced varied effects on cell cycle arrest (G0/G1 phase arrest in TPC-1 and C643, G2/M phase arrest in 8505C, and mild G2/M phase arrest with increased sub-G0/G1 population in FTC133) and on the levels of TP53, E2F-1, p21CIP1, p27KIP1, and poly (ADP-ribose) polymerase cleavage in these cells, suggesting that thyroid tumor cells respond to mortalin depletion in a cell type-specific manner. In these cells, we also determined the efficacy of triphenyl-phosphonium-carboxy-proxyl (Mito-CP) because this mitochondria-targeted metabolism interfering agent exhibited similar tumor suppressive effects as mortalin depletion in MTC cells. Indeed, Mito-CP also induced robust caspase-dependent apoptosis in PTC and ATC cell lines in vitro, exhibiting IC50 lower than PLX4032 in 8505C cells and IC50 lower than vandetanib and cabozantinib in TPC-1 cells. Intriguingly, Mito-CP-induced cell death was partially rescued by mortalin overexpression, suggesting that Mito-CP may inactivate a mechanism that requires mortalin function. These findings support the significance of mortalin and mitochondrial activity in a broad spectrum of thyroid cancer.

Independent Roles of Estrogen Deficiency and Cellular Senescence in the Pathogenesis of Osteoporosis: Evidence in Young Adult Mice and Older Humans.

Estrogen deficiency is a seminal mechanism in the pathogenesis of osteoporosis. Mounting evidence, however, establishes that cellular senescence, a fundamental mechanism that drives multiple age-related diseases, also causes osteoporosis. Recently, we systematically identified an accumulation of senescent cells, characterized by increased p16Ink4a and p21Cip1 levels and development of a senescence-associated secretory phenotype (SASP), in mouse bone/marrow and human bone with aging. We then demonstrated that elimination of senescent cells prevented age-related bone loss using multiple approaches, eg, treating old mice expressing a "suicide" transgene, INK-ATTAC, with AP20187 to induce apoptosis of p16Ink4a -senescent cells or periodically treating old wild-type mice with "senolytics," ie, drugs that eliminate senescent cells. Here, we investigate a possible role for estrogen in the regulation of cellular senescence using multiple approaches. First, sex steroid deficiency 2 months after ovariectomy (OVX, n = 15) or orchidectomy (ORCH, n = 15) versus sham surgery (SHAM, n = 15/sex) in young adult (4-month-old) wild-type mice did not alter senescence biomarkers or induce a SASP in bone. Next, in elderly postmenopausal women, 3 weeks of estrogen therapy (n = 10; 74 ± 5 years) compared with no treatment (n = 10; 78 ± 5 years) did not alter senescence biomarkers or the SASP in human bone biopsies. Finally, young adult (4-month-old) female INK-ATTAC mice were randomized (n = 17/group) to SHAM+Vehicle, OVX+Vehicle, or OVX+AP20187 for 2 months. As anticipated, OVX+Vehicle caused significant trabecular/cortical bone loss compared with SHAM+Vehicle. However, treatment with AP20187, which eliminates senescent cells in INK-ATTAC mice, did not rescue the OVX-induced bone loss or alter senescence biomarkers. Collectively, our data establish independent roles of estrogen deficiency and cellular senescence in the pathogenesis of osteoporosis, which has important implications for testing novel senolytics for skeletal efficacy, as these drugs will need to be evaluated in preclinical models of aging as opposed to the current FDA model of prevention of OVX-induced bone loss. © 2019 American Society for Bone and Mineral Research.

Identification of a novel regulatory mechanism involved in inhibition of transcription of suvivin mRNA in breast cancer cells via p21cip–mediated regulation

Purpose: To evaluate the effect of p21Cip1 on survivin transcription levels in breast carcinoma, and to investigate the potential mechanisms.Methods: Epirubicin, a p21Cip1 activator, was used to treat MCF7 cells. Under the action of normal biological functions of p53, pEGFP-C2-p21 was transfected into MCF7 cells by lipofectamine and positive clones were screened out with G418. The expression levels of p21cip1, p53 and survivin mRNA were quantitated by real-time fluorescent polymerase chain reaction (RQ-PCR). MTT assay was utilized to measure cellular viability and proliferation after transfection. Flow cytometry was employed to determine the cell cycle. Hoechst 33342 staining was carried out to assess cell apoptosis. Lastly, several transcription factor sites located at the promoter region of survivin gene, such as, sp1 site, E2F site and p300/CBP, were measured by p21 overexpression using RT-PCR.Results: Following epirubicin treatment, within 24 h, the expression levels of endogenous p21cip1 and p53 were up-regulated, whereas that of survivin was down-regulated. After transfection treatment, p21 inhibited the proliferation of MCF7 cells on days 3 and 4, and MCF7 cells overexpressed p21 mRNA, whereas the level of survivin mRNA in MCF7-p21 groups was markedly down-regulated relative to control group, but overexpression of p21 was not sufficient to cause changes in p53 gene expression. The overexpressed p21 resulted in G1/G0 phase arrest based on cell cycle analysis, but apoptosis was not induced. In addition, co-transcription factors E2F-1, sp1 and p300/CBP mRNA levels decreased significantly compared with normal p21 expression groups.Conclusion: P21cip1 may down-regulate the expression of survivin gene partially by inhibiting the expression level of HAT.Keywords: Cyclin-dependent kinase inhibitor 1, Phosphoprotein p53, Survivin, Breast carcinoma, G1/G0 phase arrest, Epirubicin, Lipofectamine

Blockage of glutamine-dependent anaplerosis affects mTORC1/2 activity and ultimately leads to cellular senescence-like response.

ABSTRACTThe purpose of study was to explore the role of glutamine-dependent anaplerosis in cell fate determination (proliferation and senescence) and the potential associated mechanism by employing a pharmacological inhibitor of glutamine-dependent anaplerosis, amino-oxyacetate (AOA). Using the WI38 normal human embryonic fibroblast cell line, we found that exposure to AOA induced mTORC1 inactivation−mTORC2 activation (within day 1), cell cycle arrest (day 2–6) and cellular senescence (day 4–6). These AOA effects were blocked by concomitantly providing anaplerotic factors [α-ketoglutarate (αKG), pyruvate or oxaloacetate], and not affected by ROS scavenger N-acetyl-cysteine (NAC). Moreover, AOA-induced cellular senescence in WI38 cells is associated with elevated protein levels of p53, p21CIP1 and p16INK4A and decreased Rb protein level, which was blocked by αKG supplementation. In p16INK4A-deficient U2OS human osteosarcoma cells and p16INK4A-knockdown WI38 cells, AOA exposure also induced similar effects on cell proliferation, and protein level of P-Rb-S807/811 and Rb. Interestingly, no AOA induction of cellular senescence was observed in U2OS cells, yet was still seen in p16INK4A-knockdown WI38 cells accompanied by the presence of p16 antibody-reactive p12. In summary, we disclose that glutamine-dependent anaplerosis is essential to cell growth and closely associated with mTORC1 activation and mTORC2 inactivation, and impedes cellular senescence particularly associated with p16INK4A.

Activation of the Non-Canonical Estrogen Receptor Gper As a Novel Therapeutic Strategy Against Waldenström Macroglobulinemia

Although estrogens have been shown to regulate normal B cell proliferation and differentiation, the impact of estrogen receptor (ER) signaling on B cell malignancies, including Waldenström Macroglobulinemia (WM), remains unexplored. To address this issue, we have analyzed, through preclinical WM models, the druggability either of the classical estrogen receptor ERβ, an emerging target for acute leukemias and certain types of lymphomas, and of the novel, more recently deorphanized G-protein coupled ER GPER, whose therapeutic potential in solid tumors has recently emerged.Both ERβ and GPER were found expressed at mRNA and protein level in a panel of WM and IgM-secreting lymphoma cell lines. However, while treatment with ERβ agonists did not elicit any effect, selective GPER activation significantly reduced WM cell viability. On this basis, we investigated GPER expression pattern and therapeutic potential in WM.By interrogating public microarray datasets, we found GPER transcript significantly upregulated in WM as compared to normal B cells; moreover, immunohistochemical analysis showed elevated GPER expression in lymph node biopsies from newly-diagnosed WM patients as compared to healthy lymph nodes. Treatment with the selective GPER agonist G-1 ( (±) -1-[(3aR*,4S*,9bS*)-4-(6-Bromo-1,3-benzodioxol-5-yl) -3a,4,5,9b-tetrahydro-3H cyclopenta [c]quinolin-8-yl] ethanone) led to reduced viability, clonogenicity and migration of WM and IgM-secreting lymphoma cell lines (IC50 at 48h ranging between 2.5 and 5.0 mM), including MYD88 and CXCR4 mutated cell lines, and even in the presence of bone marrow-derived stromal cells, while it did not affect healthy CD19+ B cell viability; conversely, GPER antagonists G-36 and G-15 slightly enhanced cell proliferation. The growth inhibitory activity of G-1 was associated with accumulation in G2/M cell cycle phase and induction of apoptosis, the latter phenomenon assessed by Annexin V/7AAD staining, analysis of mitochondrial membrane depolarization and cleavage of caspase 3, 7 and 9; hybridization of an antibody-array also highlighted G-1-induced down-regulation of anti-apoptotic proteins, including survivin and Bcl2. A significant effect of G-1 was also observed in primary tumor cells from refractory WM patients. Moreover, G-1 synergistically enhanced bortezomib and ibrutinib cytotoxicity in vitro. Importantly, intraperitoneal injection of G-1 (2mg/kg) significantly reduced the growth of BCWM-1 xenografts in NOD/SCID mice.To gain further insight into the consequences of selective GPER activation, we performed gene expression profile and GSEA analysis of WM cell lines treated with G-1. Of note, the p53 signaling pathway was strongly induced upon GPER activation, and upregulation of p53 and of its target genes or microRNAs (p21CIP1, Bax, Bad, PUMA and miR-34a) was confirmed both in G-1 treated WM cell lines and primary WM cells; moreover, G-1 combination with bortezomib or ibrutinib led to stronger increase in p53 and p21CIP1 levels as compared to single agent treatment. Finally, p53 knock-down partially reversed G-1-dependent anti-WM effects, thus suggesting p53 as downstream mediator of GPER.In summary, we report a significant anti-tumor activity upon selective GPER activation in WM cells, with apoptosis induction and a potent synergistic anti-WM activity in combination with ibrutinib and bortezomib. Altogether, these preclinical data suggest GPER agonists as a potential therapeutic option in WM. DisclosuresMunshi:OncoPep: Other: Board of director.

Abstract P5-21-15: The synergistic antitumor activity of entinostat (MS-275) in combination with palbociclib (PD 0332991) in estrogen receptor-positive and triple-negative breast cancer

Abstract BACKGROUND: CDK4/6 regulates the G1-S phase transition by phosphorylating the retinoblastoma protein (Rb). Given their potent clinical efficacy, CDK4/6 inhibitors used in combination with hormone receptor (HR) blockade (with an aromatase inhibitor or fulvestrant) are emerging as the standard of care for patients with metastatic HR-positive breast cancers. The CDK4/6 inhibitors palbociclib and ribociclib are FDA-approved for use in HR-positive breast cancer patients, and abemaciclib is currently in phase III trials. We observed that approximately 74% (25/34) of breast cancer cell lines had high phosphorylated Rb (phospho-Rb) expression levels and that triple-negative breast cancer (TNBC) cell lines often expressed phospho-Rb, suggesting that targeting phospho-Rb via CDK4/6 inhibition may be effective against TNBC. The histone deacetylase (HDAC) inhibitors increase p21Cip1 levels, promoting proteasomal degradation of cyclin B1 and resulting in G2/M arrest. Entinostat is an oral, class 1, selective HDAC inhibitor currently in phase III testing in HR-positive breast cancer. Preclinical and clinical data demonstrate that entinostat, in combination with HR blockade, has anticancer activity. Our group recently reported that entinostat combined with other anticancer drugs induced apoptosis via induction of proapoptotic proteins such as Noxa and Bim in breast cancer cell lines. Based on these findings, we hypothesized that entinostat-induced apoptosis and palbociclib-induced cell cycle arrest synergize to produce enhanced antitumor effects in estrogen receptor (ER)-positive breast cancer and TNBC cell lines with high phospho-Rb expression levels. METHODS: We assessed the combination antitumor effects and their mechanisms via CellTiter Blue and sulforhodamine B assays, flow cytometry, apoptosis (caspase 3/7) assays, anchorage-independent growth assays, Western blotting, reverse phase protein array (RPPA), and mammary fat pad xenograft mouse models. RESULTS: RPPA data showed that ER-positive and TNBC cell lines more often expressed phospho-Rb than did other breast cancer cell subtypes (7/10 and 8/17 cell lines, respectively). We found that the combination of entinostat and palbociclib synergistically inhibited tumor cell proliferation (combinational index less than 1.0), reduced in vitro colony formation (P < 0.05), inhibited in vivo tumor growth in ER-positive MCF-7 breast cancer cells (P < 0.05), and inhibited tumor growth in TNBC xenograft mouse models (MDA-MB-231) more effectively than did either drug alone. CONCLUSION: Taken together, our data provide evidence that combining entinostat with palbociclib enhances the antitumor effects of these drugs. Along with our continued effort to determine predictive biomarkers, our findings justify conducting a clinical trial of combination treatment with entinostat and palbociclib in patients with ER-positive breast cancer or TNBC. Citation Format: Lee J, Lim B, Pearson T, Tripathy D, Ordentlich P, Ueno NT. The synergistic antitumor activity of entinostat (MS-275) in combination with palbociclib (PD 0332991) in estrogen receptor-positive and triple-negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-21-15.

RNA sequencing reveals widespread transcriptome changes in a renal carcinoma cell line.

We used RNA sequencing (RNA-Seq) technology to investigate changes in the transcriptome profile in the Caki-1 clear cell renal cell carcinoma (ccRCC) cells, which overexpress monocyte chemoattractant protein-induced protein 1 (MCPIP1). RNA-Seq data showed changes in 11.6% and 41.8% of the global transcriptome of Caki-1 cells overexpressing wild-type MCPIP1 or its D141N mutant, respectively. Gene ontology and KEGG pathway functional analyses showed that these transcripts encoded proteins involved in cell cycle progression, protein folding in the endoplasmic reticulum, hypoxia response and cell signalling. We identified 219 downregulated transcripts in MCPIP1-expressing cells that were either unchanged or upregulated in D141N-expressing cells. We validated downregulation of 15 transcripts belonging to different functional pathways by qRT-PCR. The growth and viability of MCPIP1-expressing cells was reduced because of elevated p21Cip1 levels. MCPIP1-expressing cells also showed reduced levels of DDB1 transcript that encodes component of the E3 ubiquitin ligase that degrades p21Cip1. These results demonstrate that MCPIP1 influences the growth and viability of ccRCC cells by increasing or decreasing the transcript levels for proteins involved in cell cycle progression, protein folding, hypoxia response, and cell signaling.

A diphenyldiselenide derivative induces autophagy via JNK in HTB-54 lung cancer cells.

Symmetric aromatic diselenides are potential anticancer agents with strong cytotoxic activity. In this study, the in vitro anticancer activities of a novel series of diarylseleno derivatives from the diphenyldiselenide (DPDS) scaffold were evaluated. Most of the compounds exhibited high efficacy for inducing cytotoxicity against different human cancer cell lines. DPDS 2, the compound with the lowest mean GI50 value, induced both caspase‐dependent apoptosis and arrest at the G0/G1 phase in acute lymphoblastic leucemia CCRF‐CEM cells. Consistent with this, PARP cleavage; enhanced caspase‐2, ‐3, ‐8 and ‐9 activity; reduced CDK4 expression and increased levels of p53 were detected in these cells upon DPDS 2 treatment. Mutated p53 expressed in CCRF‐CEM cells retains its transactivating activity. Therefore, increased levels of p21CIP1 and BAX proteins were also detected. On the other hand, DPDS 6, the compound with the highest selectivity index for cancer cells, resulted in G2/M cell cycle arrest and caspase‐independent cell death in p53 deficient HTB‐54 lung cancer cells. Autophagy inhibitors 3‐methyladenine, wortmannin and chloroquine inhibited DPDS 6‐induced cell death. Consistent with autophagy, increased LC3‐II and decreased SQSTM1/p62 levels were detected in HTB‐54 cells in response to DPDS 6. Induction of JNK phosphorylation and a reduction in phospho‐p38 MAPK were also detected. Moreover, the JNK inhibitor SP600125‐protected HTB‐54 cells from DPDS 6‐induced cell death indicating that JNK activation is involved in DPDS 6‐induced autophagy. These results highlight the anticancer effects of these derivatives and warrant future studies examining their clinical potential.

Regulation of myoblast differentiation by metabolic perturbations induced by metformin.

The metabolic perturbation caused by calorie restriction enhances muscle repair by playing a critical role in regulating satellite cell availability and activity in the muscles of young and old mice. To clarify the underlying mechanisms we asked whether myoblast replication and differentiation are affected by metformin, a calorie restriction-mimicking drug. C2C12, a mouse myoblast cell line, readily differentiate in vitro and fuse to form myotubes. However, when incubated with metformin, C2C12 slow their replication and do not differentiate. Interestingly, lower doses of metformin promote myogenic differentiation. We observe that metformin treatment modulates the expression of cyclins and cyclin inhibitors thereby inducing a cell cycle perturbation that causes a delay in the G2/M transition. The effect of metformin treatment is reversible since after drug withdrawal, myoblasts can re-enter the cell cycle and/or differentiate, depending on culture conditions. Myoblasts cultured under metformin treatment fail to up-regulate MyoD and p21cip1, a key step in cell cycle exit and terminal differentiation. Although the details of the molecular mechanisms underlying the effect of the drug on myoblasts still need to be clarified, we propose that metformin negatively affects myogenic differentiation by inhibiting irreversible exit from the cell cycle through reduction of MyoD and p21cip1 levels.

CRL4BDCAF11 E3 ligase targets p21 for degradation to control cell cycle progression in human osteosarcoma cells

Cell cycle progression in mammals is strictly controlled by a number of cyclin-dependent kinases (CDKs) and CDK inhibitors (CKIs), the expression of which is often dysregulated in cancer cells. Our previous work revealed that Cullin 4B (CUL4B), a critical component of the Cullin4B-RING E3 ligase complex (CRL4B), is overexpressed in human osteosarcoma cells through an unknown mechanism. Here, we demonstrated that CUL4B forms an E3 ligase with RBX1 (RING-box 1), DDB1 (DNA damage binding protein 1), and DCAF11 (DDB1 and CUL4 associated factor 11) in human osteosarcoma cells. In vitro and in vivo ubiquitination analyses indicated that CRL4BDCAF11 E3 ligase was able to specifically ubiquitinate a CDK inhibitor—p21Cip1 at K16, K154, K161 and K163 but not at K75 and K141. Knocking down any component of the CRL4BDCAF11 complex, including CUL4B, DDB1 or DCAF11, using short hairpin RNAs (shRNAs) attenuated the ubiquitination level of p21Cip1, inhibited osteosarcoma cell proliferation, led to cell cycle arrest at S phase, and decreased colony formation rate. Taken together, our data suggest that the CRL4BDCAF11 complex represents a unique E3 ligase that promotes the ubiquitination of p21Cip1 and regulates cell cycle progression in human osteosarcoma cells.

Cdk5 Directly Targets Nuclear p21CIP1 and Promotes Cancer Cell Growth.

The significance of Cdk5 in cell-cycle control and cancer biology has gained increased attention. Here we report the inverse correlation between the protein levels of Cdk5 and p21CIP1 from cell-based and clinical analysis. Mechanistically, we identify that Cdk5 overexpression triggers the proteasome-dependent degradation of p21CIP1 through a S130 phosphorylation in a Cdk2-independent manner. Besides, the evidence from cell-based and clinical analysis shows that Cdk5 primarily regulates nuclear p21CIP1 protein degradation. S130A-p21CIP1 mutant enables to block either its protein degradation or the increase of cancer cell growth caused by Cdk5. Notably, Cdk5-triggered p21CIP1 targeting primarily appears in S-phase, while Cdk5 overexpression increases the activation of Cdk2 and its interaction with DNA polymerase δ. The in vivo results show that Cdk2 might play an important role in the downstream signaling to Cdk5. In summary, these findings suggest that Cdk5 in a high expression status promotes cancer growth by directly and rapidly releasing p21CIP1-dependent cell-cycle inhibition and subsequent Cdk2 activation, which illustrates an oncogenic role of Cdk5 potentially applied for future diagnosis and therapy. Cancer Res; 76(23); 6888-900. ©2016 AACR.

Upregulated microRNA-143 inhibits cell proliferation in human nasopharyngeal carcinoma.

The aim of the present study was to investigate the possible functions and mechanism of microRNA (miR)-143 in cell proliferation of human nasopharyngeal carcinoma (NPC). The expression of miR-143 in NPC cells and tissues was investigated using reverse transcription-quantitative polymerase chain reaction. Cell viability assay, colony formation assay and flow cytometry were used to examine the cell proliferative ability and tumorigenicity. The expression levels of p21Cip1, p27Kip1, cyclin D1, phosphorylated (p)-retinoblastoma protein (Rb), Rb and cyclin-dependent kinase (CDK) 6 were determined by western blotting. Luciferase assay was used to confirm whether CDK6 was a direct target of miR-143. miR-143 was downregulated in NPC cell lines and tissues. Overexpression of miR-143 in NPC CNE1 cells inhibited proliferation, tumorigenicity and cell cycle progression. Additionally, ectopic expression of miR-143 downregulated cyclin D1 and p-Rb expression, and upregulated p21Cip1 and p27Kip1 expression, which subsequently inhibited NPC cell proliferation. It was also observed that CDK6 was a direct target of miR-143, which downregulated CDK6 expression. CDK6 suppression by miR-143 was associated with dysregulated expression of p21Cip1, p27Kip1, cyclin D1 and p-Rb, thereby serving an essential role in NPC cell growth. Our findings suggest that miR-143 inhibits proliferation by targeting CDK6, and may aid to identify new targets for anti-oncomiRs.

Ablation of human telomerase reverse transcriptase (hTERT) induces cellular senescence in gastric cancer through a galectin-3 dependent mechanism.

The human Telomerase Reverse Transcriptase (hTERT) gene encodes a rate-limiting catalytic subunit of telomerase that maintains genomic integrity. Suppression of hTERT expression could induce cellular senescence and is considered a potent approach for gastric cancer therapy. However, control of hTERT expression and function remains poorly understood in gastric cancer. In this study, we demonstrated that high expression levels of hTERT in malignant tissues are correlated with poor survival probability in gastric cancer patients. Knockdown of hTERT expression retarded cell proliferation and cellular senescence, which was confirmed by increased protein expression levels of p21cip1 and p27kip1, and decreased phosphorylation of Rb. In contrast, overexpression of hTERT increased cell proliferation and decreased cellular senescence. Remarkably, the down-regulation of hTERT expression was detected in lgals3−/− mouse embryo fibroblasts (MEFs). Knockdown of galectin-3 decreased the expression of hTERT in gastric cancer cells. Galectin-3 ablation-induced cellular senescence was rescued by concomitant overexpression of hTERT. hTERT ablation-induced cellular senescence and p21cip1 and p27kip1 expression was rescued by concomitant overexpression of galectin-3. The size of tumor burdens was increased in hTERT-overexpressed gastric cancer cells xenografted mice, whereas it was repressed by concomitant depletion of galectin-3. Additionally, we determined that the N-terminal domain of galectin-3 directly interacted with hTERT. The telomeric activity of hTERT was also decreased by galectin-3 ablation. Taken together, ablation of hTERT induces cellular senescence and inhibits the growth of gastric cancer cells, suggesting that it could be a potent target in gastric cancer therapy. We also propose that galectin-3 is an important regulator of hTERT expression and telomeric activity in gastric tumorigenesis.

Abstract LB-334: The Nrf2-subcellular localization in human acute myeloblastic leukemic cells is regulated by the bone marrow mesenchymal stem/stromal cells

Abstract BACKGROUND. The redox metabolism is a key actor in the pathophysiology of acute myeloblastic leukemia (AML). High level of reactive oxygen species (ROS) is observed in the leukemic bulk, whereas leukemic stem cells (LSCs) have a low level of ROS, and we reported that glutathione peroxydase 3 (GPx-3) promotes competitiveness of LSCs in which Gpx3 overexpression is associated with a decreased level of ROS and inactivation of p38 MAPK (Herault O et al, J Exp Med 2012, 209:895). NF-E2-related factor 2 (Nrf2) transcription factor, the master regulator of antioxidant responses, is highly expressed in acute myeloblastic leukemia (AML) and is involved in its chemoresistance (Rushworth SA et al, Blood 2012, 120,5188). Since leukemic cells interact with mesenchymal stem/stromal cells (MSCs) in the bone marrow (BM) niche, the aim of our study was to evaluate the effects of MSC-contact on the Nrf2 sub-cellular localization in acute myeloid leukemia (AML) cells and to concomitantly assess the the GPx-3/ROS/p38 MAPK axis and cell cycle status. METHODS. BM MSCs (from consenting patients undergoing orthopaedic surgery) were used at P2. The mesenchymal differentiation capacity was systematically checked. The KG1a (FAB M0 AML) cell line and primary AML blasts were cultured for 72h in presence of MSCs and compared to their counterpart cultured in presence of supernatant from MSCs alone or medium alone. ROS level measurements (DCFDA), cell cycle analyses (Vignon C et al, PLOS One 2013, 8: e68425) and proliferation assays (CFSE) of the leukaemic cells were performed by flow cytometry. Expression levels of 24 key antioxidant genes, CDKN1A (p21, Cip1) and 22 Nrf2-regulated genes were quantified by qRT-PCR. Western-blot analyses were also realized to determine the expression levels of GPx-3 and p21(Cip1), the activation of p38 MAPK (T180/Y182) and the localization of Nrf2 after subcellular fractionation. RESULTS. Adherent KG1a cells were characterized by major decrease in nuclear translocation of Nrf2 and expression of Nrf2-regulated genes. We concomitantly observed overexpression of GPX3 mRNA and protein, major decrease in ROS levels and inactivation of p38 MAPK. Similar results were obtained with adherent primary leukemic cells. These effects were concomitantly observed with major decrease in nuclear translocation of Nrf2 and expression of Nrf2-regulated genes. Interestingly, the increased G0 phase, together with the decreased S and M phases, and overexpression of CDKN1A mRNA and protein demonstrated cell cycle inhibition and reduced mitotic activity. The supernatant of MSCs did not impact on Nrf2-subcellular localization, GPx-3 expression and ROS levels in leukemic cells. CONCLUSION. Altogether these findings suggest that the niche (direct contact to MSCs) plays a key role in the regulation of the oxidative metabolism in leukemic cells by modifying the subcellular localization of Nrf2 and by promoting the inhibition of the ROS/p38 MAPK axis through the induction of GPx-3, resulting in a reduced proliferation. Targeting the Nrf2 pathway in leukemic cells by a modulation of microenvironmental interactions may be a clinically relevant chemosensitizing approach. Citation Format: Olivier Herault, Christine Vignon, Christelle Debeissat, Florence Rouleux-Bonnin, Emmanuel Gyan, Frederic Mazurier, Fabrice Gouilleux, Jorge Domenech. The Nrf2-subcellular localization in human acute myeloblastic leukemic cells is regulated by the bone marrow mesenchymal stem/stromal cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-334.

Abstract 1922: miR-301 expression is deregulated in rhabdomyosarcoma

Abstract Rhabdomyosarcoma (RMS) is an aggressive pediatric soft tissue sarcoma of myogenic derivation. Conversely to normal myoblasts, RMS cells are unable to differentiate, thus they proliferate indefinitely. MicroRNAs (miRNAs) are short (20-24 nt) non-coding RNAs that are involved in post-transcriptional regulation of gene expression by affecting both the stability and translation of mRNAs. They are fundamental regulators of myogenesis and their deregulation has been involved in the pathogenesis of RMS. We evaluate here the expression and regulation of miR-301, which has been related to tumorigenesis in other types of cancers. We report here that the expression of miR-301 is upregulated in primary samples of both the alveolar RMS, which bears the fusion protein PAX3-FOXO1 (P3F) (ARMS), and the fusion-negative embryonal RMS (ERMS) compared to normal muscle tissues. Similarly, it appears higher in RMS cell lines versus normal skeletal myoblasts. Using an inhibitor of miR-301 (CONTRAmiR) we demonstrate that this miRNA favors RMS cell mobility and down-regulates p21Cip1, PTEN and DICER1 levels. However, the inhibition of miR-301 with the CONTRAmiR does not reduce tumor cell proliferation suggesting that the regulation of cell cycle is not under the control of this miRNA in RMS. Interestingly, the expression of SKA2 (Spindle And Kinetochore Associated Complex Subunit 2), whose gene hosts miR-301, is also upregulated in our setting. Experiments are ongoing to determine whether miR-301 and SKA2 are associated with RMS pathogenesis and could be targets for an anti-RMS therapy. This work was supported by the Associazione Italiana per la Ricerca sul Cancro (AIRC). Citation Format: Rossella Rota, Alberto Gualtieri, Cristina Cossetti, Silvia Pomella, Laura Adesso, Franco Locatelli. miR-301 expression is deregulated in rhabdomyosarcoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1922.

Halofuginone and artemisinin synergistically arrest cancer cells at the G1/G0 phase by upregulating p21Cip1 and p27Kip1.

Combinational drug therapy is one of the most promising strategies in modern anticancer research. Traditional Chinese medicine (TCM) formulas represent a wealth of complex combinations proven successful over centuries of clinical application. One such formula used to treat a variety of diseases, including cancer, contains two herbs, whose main active components are Halofuginone (HF) and Artemisinin (ATS). Here we studied the anticancer synergism of HF and ATS in various cancer cell lines and in a xenograft nude mice model. We found that the HF-ATS combination arrested more cells at the G1/G0 phase than either one alone, with the concomitant increased levels of CDK2 inhibitors, p21Cip1 and p27Kip1. By knocking down p21Cip1 and p27Kip1 separately or simultaneously in HCT116 cells and MCF-7 cells, we found that p21Cip1 was required for HF induced G1/G0 arrest, whereas p21Cip1 and p27Kip1 were both required for ATS or HF-ATS combination-mediated cell cycle arrest. Moreover, HF-ATS combination synergistically inhibited tumor growth in xenograft nude mice, and this was associated with the increased levels of p21Cip1 and p27Kip1. Collectively, these data indicate that the upregulation of p21Cip1 and p27Kip1 contributes to the synergistic anticancer effect of the HF-ATS combination.

KLF4α stimulates breast cancer cell proliferation by acting as a KLF4 antagonist.

Krüppel-like factor 4 (KLF4), a transcription factor involved in both tumor suppression and oncogenesis in various human tumors, is subject to alternative splicing that produces KLF4α. KLF4α is primarily expressed in the cytoplasm because it lacks exon 3 of KLF4, which contains the nuclear localization signal. The role of KLF4 in breast cancer remains unclear and nothing is known yet about the expression and function of the isoform KLF4α. Here, we show that KLF4α is expressed in normal and tumoral tissue of the breast and provide evidence that the KLF4α/KLF4(full-length) (FL) ratio is increased in tumors compared to corresponding normal tissue. Forced increase of the KLF4α/KLF4(FL) ratio in the metastatic breast cancer cell line MDA-MB-231 decreases the levels of E-Cadherin, p21Cip1, and p27Kip1, three known KLF4(FL) target genes, and stimulates cell proliferation. We suggest that cytoplasmic KLF4α binds to KLF4(FL) and retains it in the cytoplasm thereby antagonizing the gene regulatory activities of KLF4(FL) in the nucleus. Our results establish KLF4α as a KLF4 isoform that opposes the function of KLF4(FL) and as an important factor in the complex and unresolved role of KLF4(FL) in breast carcinogenesis.

PRMT7 Preserves Satellite Cell Regenerative Capacity.

Regeneration of skeletal muscle requires the continued presence of quiescent muscle stem cells (satellite cells), which become activated in response to injury. Here, we report that whole-body protein arginine methyltransferase PRMT7(-/-) adult mice and mice conditionally lacking PRMT7 in satellite cells using Pax7-CreERT2 both display a significant reduction in satellite cell function, leading to defects in regenerative capacity upon muscle injury. We show that PRMT7 is preferentially expressed in activated satellite cells and, interestingly, PRMT7-deficient satellite cells undergo cell-cycle arrest and premature cellular senescence. These defects underlie poor satellite cell stem cell capacity to regenerate muscle and self-renew after injury. PRMT7-deficient satellite cells express elevated levels of the CDK inhibitor p21CIP1 and low levels of its repressor, DNMT3b. Restoration of DNMT3b in PRMT7-deficient cells rescues PRMT7-mediated senescence. Our findings define PRMT7 as a regulator of the DNMT3b/p21 axis required to maintain muscle stem cell regenerative capacity.

Adipocyte progenitor cells initiate monocyte chemoattractant protein-1-mediated macrophage accumulation in visceral adipose tissue.

ObjectiveMacrophages are important producers of obesity-induced MCP-1; however, initial obesity-induced increases in MCP-1 production precede M1 macrophage accumulation in visceral adipose tissue (VAT). The initial cellular source of obesity-induced MCP-1 in vivo is currently unknown. Preliminary reports based on in vitro studies of preadipocyte cell lines and adherent stroma-vascular fraction cells suggest that resident stromal cells express MCP-1. In the past several years, elegant methods of identifying adipocyte progenitor cells (AdPCs) have become available, making it possible to study these cells in vivo. We have previously published that global deletion of transcription factor Inhibitor of Differentiation 3 (Id3) attenuates high fat diet-induced obesity, but it is unclear if Id3 plays a role in diet-induced MCP-1 production. We sought to determine the initial cellular source of MCP-1 and identify molecular regulators mediating MCP-1 production.MethodsId3+/+ and Id3−/− mice were fed either a standard chow or HFD for varying lengths of time. Flow cytometry, semi-quantitative real-time PCR, ELISAs and adoptive transfers were used to assess the importance of AdPCs during diet-induced obesity. Flow cytometry was also performed on a cohort of 14 patients undergoing bariatric surgery.ResultsFlow cytometry identified committed CD45−CD31−Ter119−CD29+CD34+Sca-1+CD24− adipocyte progenitor cells as producers of high levels of MCP-1 in VAT. High-fat diet increased AdPC numbers, an effect dependent on Id3. Loss of Id3 increased p21Cip1 levels and attenuated AdPC proliferation, resulting in reduced MCP-1 and M1 macrophage accumulation in VAT, compared to Id3+/+ littermate controls. AdPC rescue by adoptive transfer of 50,000 Id3+/+ AdPCs into Id3−/− recipient mice increased MCP-1 levels and M1 macrophage number in VAT. Additionally, flow cytometry identified MCP-1-producing CD45−CD31−CD34+CD44+CD90+ AdPCs in human omental and subcutaneous adipose tissue, with a higher percentage in omental adipose. Furthermore, high surface expression of CD44 marked abundant MCP-1 producers, only in visceral adipose tissue.ConclusionsThis study provides the first in vivo evidence, to our knowledge, that committed AdPCs in VAT are the initial source of obesity-induced MCP-1 and identifies the helix-loop-helix transcription factor Id3 as a critical regulator of p21Cip1 expression, AdPC proliferation, MCP-1 expression and M1 macrophage accumulation in VAT. Inhibition of Id3 and AdPC expansion, as well as CD44 expression in human AdPCs, may serve as unique therapeutic targets for the regulation of adipose tissue inflammation.

Extra-Nuclear Signaling Pathway Involved in Progesterone-Induced Up-Regulations of p21cip1 and p27kip1 in Male Rat Aortic Smooth Muscle Cells

Previously, we demonstrated that progesterone (P4) at physiologic levels (5-500 nM) inhibited proliferation in cultured rat aortic smooth muscle cells (RASMCs) through a P4 receptor (PR)-dependent pathway. We also showed that P4-induced cell cycle arrest in RASMCs occurs when the cyclin-CDK2 system is inhibited just as p21cip1 and p27kip1 protein levels are augmented. In the present study, we further investigated the molecular mechanism underlying P4-induced up-regulations of p21cip1 and p27kip1 in RASMCs. We used pharmacological inhibitors as well as dominant negative constructs and conducted Western blot analyses to delineate the signaling pathway involved. Our data suggest that P4 up-regulated the expression of p21cip1 and p27kip1 in RASMCs through increasing the level of p53 protein mediated by activating the cSrc/Kras/Raf-1/AKT/ERK/p38/IκBα/NFκB pathway. The findings of the present study highlight the molecular mechanism underlying P4-induced up-regulations in p21cip1 and p27kip1 in RASMCs.