17 research outputs found
Patogeneza nowotwor贸w uk艂adu ch艂onnego
Lymphocyte development is a complex and multistep process that leads to generation of a repertoire of cells endowed with specific receptors and capable of recognizing and responding to antigens. The B- (BCR) and T-cell (TCR) receptors are generated as a result of immunoglobulin or TCR gene re颅arrangements that involve DNA double strand breaks. The DNA editing processes occurring in de颅veloping lymphocytes predispose cells to primary translocations and oncogenic mutations, followed by additional aberrations accumulating in the background of these primary lesions. Arising typical, recurrent genetic abnormalities are a diagnostic feature of certain lymphoid malignancies. Genetic and epigenetic lesions accumulating within cells lead to deregulated signaling pathways and un颅controlled cell proliferation, resistance to apoptosis and metabolic changes. Transformed cells retain some features of their normal counterparts, such as reliance on tonic BCR signaling and signals delivered by microenvironment. In the current manuscript, we provide a concise review of common pathogenic mechanisms in lymphoid tumors and their biological implications.Limfopoeza to z艂o偶ony proces fizjologiczny, kt贸rego celem jest stworzenie repertuaru kom贸rek ze swoistymi receptorami zdolnymi do odpowiedzi na antygeny. Powstanie receptora B-kom贸rkowego (BCR) lub T-kom贸rkowego (TCR) nast臋puje wskutek rearan偶acji gen贸w immunoglobulinowych lub gen贸w TCR, zachodz膮cych z udzia艂em reakcji obejmuj膮cych powstanie podw贸jnych p臋kni臋膰 DNA. Procesy edycji DNA BCR i TCR predysponuj膮 limfocyty do nabywania translokacji i mutacji o charakterze onkogennym stanowi膮cych t艂o dla akumulacji kolejnych zaburze艅. Aberracje gene颅tyczne to cz臋sty mechanizm patogenetyczny i w zwi膮zku z tym s膮 jednym z kryteri贸w diagnostycz颅nych nowotwor贸w uk艂adu ch艂onnego. Konsekwencj膮 genetycznych nieprawid艂owo艣ci jest zaburzenie aktywno艣ci uk艂ad贸w sygna艂owych i kluczowych funkcji biologicznych, takich jak cykl kom贸rkowy, apoptoza i metabolizm. Stransformowane kom贸rki zachowuj膮 niekt贸re z cech swoich prawid艂owych odpowiednik贸w, na przyk艂ad zale偶no艣膰 od tonicznego sygna艂u BCR i zdolno艣膰 do interakcji z ich naturalnym mikro艣rodowiskiem, stanowi膮cym 藕r贸d艂o sygna艂贸w wspieraj膮cych wzrost nowotworu. W niniejszej pracy przedstawiono najistotniejsze i najcz臋stsze mechanizmy patogenezy nowotwor贸w uk艂adu ch艂onnego oraz ich biologiczne konsekwencje
Zaburzenia mechanizm贸w epigenetycznych w ostrej bia艂aczce szpikowej
Epigenetic regulation influences gene expression without changing the nucleotide sequence of the deoxyribonucleic acid (DNA). The most important epigenetic mechanisms include DNA methylation, modifications of histone proteins and non-coding RNAs. The dysregulation of the above mentioned processes plays a significant role in the pathogenesis of acute myeloid leukemia (AML). Mutations in the genes that are essential for epigenetic regulations are common in 70% of patients with AML. The most frequent mutations involve the DNMT3A, TET2, IDH1/2 and ASXL1 genes. Their presence or absence may constitute a vital prognostic factor in the future as well as become a potential basis for targeted therapies. The present paper manifests the importance of epigenetic alterations in the development of acute myeloid leukemia and their impact on the course of the disease. The article also discusses some possibilities for the use of epigenetic modifications in the AML therapy.Regulacja epigenetyczna wp艂ywa na ekspresj臋 gen贸w, nie zmieniaj膮c zapisu sekwencji nukleo颅tydowej kwasu deoksyrybonukleinowego (DNA). Mechanizmy epigenetyczne obejmuj膮 zmiany struktury chromatyny wskutek metylacji DNA i modyfikacji bia艂ek histonowych oraz regulacj臋 ekspresji gen贸w poprzez niekoduj膮ce cz膮steczki kwasu rybonukleinowego. Nieprawid艂owy przebieg powy偶szych proces贸w odgrywa istotn膮 rol臋 w patogenezie ostrej bia艂aczki szpikowej (AML). Mutacje gen贸w koduj膮cych regulatory epigenetyczne wyst臋puj膮 u 70% chorych z AML i najcz臋艣ciej dotycz膮 gen贸w DNMT3A, TET2, IDH1/2 oraz ASXL1. Obecno艣膰 lub brak mutacji w wymienionych ge颅nach mo偶e stanowi膰 w przysz艂o艣ci wa偶ny czynnik prognostyczny oraz potencjalny punkt uchwytu dla terapii celowanych. W poni偶szym artykule om贸wiono znaczenie zaburze艅 epigenetycznych w rozwoju AML, ich wp艂yw na przebieg choroby oraz mo偶liwo艣膰 wykorzystania w terapii
Familial Alzheimer鈥檚 Disease Lymphocytes Respond Differently Than Sporadic Cells to Oxidative Stress: Upregulated p53-p21 Signaling Linked with Presenilin 1 Mutants
MEK Inhibition Sensitizes Precursor B-Cell Acute Lymphoblastic Leukemia (B-ALL) Cells to Dexamethasone through Modulation of mTOR Activity and Stimulation of Autophagy
<div><p>Resistance to glucocorticosteroids (GCs) is a major adverse prognostic factor in B-ALL, but the molecular mechanisms leading to GC resistance are not completely understood. Herein, we sought to elucidate the molecular background of GC resistance in B-ALL and characterize the therapeutic potential of targeted intervention in these mechanisms. Using exploratory bioinformatic approaches, we found that resistant cells exhibited significantly higher expression of MEK/ERK (MAPK) pathway components. We found that GC-resistant ALL cell lines had markedly higher baseline activity of MEK and small-molecule MEK1/2 inhibitor selumetinib increased GCs-induced cell death. MEK inhibitor similarly increased <i>in vitro</i> dexamethasone activity in primary ALL blasts from 19 of 22 tested patients. To further confirm these observations, we overexpressed a constitutively active MEK mutant in GC-sensitive cells and found that forced MEK activity induced resistance to dexamethasone. Since recent studies highlight the role GC-induced autophagy upstream of apoptotic cell death, we assessed LC3 processing, MDC staining and GFP-LC3 relocalization in cells incubated with either DEX, SEL or combination of drugs. Unlike either drug alone, only their combination markedly increased these markers of autophagy. These changes were associated with decreased mTOR activity and blocked 4E-BP1 phosphorylation. In cells with silenced beclin-1 (BCN1), required for autophagosome formation, the synergy of DEX and SEL was markedly reduced. Taken together, we show that MEK inhibitor selumetinib enhances dexamethasone toxicity in GC-resistant B-ALL cells. The underlying mechanism of this interaction involves inhibition of mTOR signaling pathway and modulation of autophagy markers, likely reflecting induction of this process and required for cell death. Thus, our data demonstrate that modulation of MEK/ERK pathway is an attractive therapeutic strategy overcoming GC resistance in B-ALL patients.</p></div
Primer sequences used for MEK1 mutagenesis.
<p>Primer sequences used for MEK1 mutagenesis.</p
Serine biosynthesis pathway supports MYC-miR-494-EZH2 feed-forward circuit necessary to maintain metabolic and epigenetic reprogramming of burkitt lymphoma cells
Burkitt lymphoma (BL) is a rapidly growing tumor, characterized by high anabolic requirements. The MYC oncogene plays a central role in the pathogenesis of this malignancy, controlling genes involved in apoptosis, proliferation, and cellular metabolism. Serine biosynthesis pathway (SBP) couples glycolysis to folate and methionine cycles, supporting biosynthesis of certain amino acids, nucleotides, glutathione, and a methyl group donor, S-adenosylmethionine (SAM). We report that BLs overexpress SBP enzymes, phosphoglycerate dehydrogenase (PHGDH) and phosphoserine aminotransferase 1 (PSAT1). Both genes are controlled by the MYC-dependent ATF4 transcription factor. Genetic ablation of PHGDH/PSAT1 or chemical PHGDH inhibition with NCT-503 decreased BL cell lines proliferation and clonogenicity. NCT-503 reduced glutathione level, increased reactive oxygen species abundance, and induced apoptosis. Consistent with the role of SAM as a methyl donor, NCT-503 decreased DNA and histone methylation, and led to the re-expression of ID4, KLF4, CDKN2B and TXNIP tumor suppressors. High H3K27me3 level is known to repress the MYC negative regulator miR-494. NCT-503 decreased H3K27me3 abundance, increased the miR-494 level, and reduced the expression of MYC and MYC-dependent histone methyltransferase, EZH2. Surprisingly, chemical/genetic disruption of SBP did not delay BL and breast cancer xenografts growth, suggesting the existence of mechanisms compensating the PHGDH/PSAT1 absence in vivo
Schematic diagram showing a postulated mechanism of MEK inhibition鈥攊nduced sensitization to GCs via modulation of autophagy.
<p>Schematic diagram showing a postulated mechanism of MEK inhibition鈥攊nduced sensitization to GCs via modulation of autophagy.</p
Overexpression of a constitutively active MEK1 mutant (MEK-Q56P) in GC-sensitive RS4;11 cells induces resistance to DEX.
<p>(A) RS4;11 cells were retrovirally transduced with MEK-Q56P or empty control. Cells were lysed and ERK1/2 phoshorylation status was assessed by immunoblotting. (B-C) Control cells and MEK-Q56P鈥攖ransduced cells were incubated with DEX (0.05, 2 or 30 渭g/ml) for 72h. Thereafter, cell death was assessed by annexinV/PI staining and flow cytometry analysis. Absolute, averaged numbers of apoptotic cells in two independent experiments are indicated in (C). Error bars represent SD. P value was calculated using Student鈥檚 t-test.</p
MEK1/2 inhibitor, selumetinib sensitizes GC-resistant ALL cells to dexamethasone.
<p>(A) GC-resistant cells exhibit coordinate upregulation of MAPK/ERK pathway components. GSEA plots show relative upregulation of MAPK/ERK cascade components in GC-resistant ALL cells in two independent datasets [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155893#pone.0155893.ref025" target="_blank">25</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155893#pone.0155893.ref026" target="_blank">26</a>]. Relative expression of pathway components is visualized by the heat map. FDR- false discovery rate. (B) ALL cell lines with active MAPK/ERK pathway (SEMK2, 697, CCRF-CEM) and ALL cells with undetectable expression of MAPK/ERK pathway (RS4;11) were incubated for 4h with MEK1/2 inhibitor, selumetinib (SEL, 200 nM). Thereafter, phosphorylation status of ERK1/2 and its substrate p90RSK were assessed by immunoblotting. (C) ALL cell lines were incubated with DEX (0.05 渭g/ml 2 渭g/ml and 30 渭g/ml), SEL (200 nM) or combination of DEX+SEL for 72h and cell death was assessed by annexinV/PI staining followed by flow cytometry analysis. * p<0.05, ** p<0.01, ns- not significant. Error bars represent SD of three independent experiment. P values were calculated using Student鈥檚 t-test. (D) Cells were incubated as in (C) and used to determine the phosphorylation status of ERK1/2 by immunoblotting.</p