Assuntos
Leucemia Linfocítica Crônica de Células B , Humanos , Biomarcadores , Deleção Cromossômica , DNA , Proteína Quinase Ativada por DNA/metabolismo , Proteínas de Ligação a DNA/metabolismo , Leucemia Linfocítica Crônica de Células B/tratamento farmacológico , Leucemia Linfocítica Crônica de Células B/genética , Prognóstico , Resistencia a Medicamentos Antineoplásicos , Cromossomos Humanos Par 11RESUMO
: The phosphatidyl-inositol 3 kinase (PI3K) δ inhibitor, idelalisib (IDE), is a potent inhibitor of the B-cell receptor pathway and a novel and highly effective agent for the treatment of chronic lymphocytic leukemia (CLL). We evaluated the activities of IDE in comparison to bendamusine (BEN), a commonly used alkylating agent, in primary CLL cells ex vivo. In contrast to BEN, IDE was cytotoxic to cells from extensively-treated patients, including those with a deletion (del)17p. Cross-resistance was not observed between BEN and IDE, confirming their different modes of cytotoxicity. Marked synergy was seen between BEN and IDE, even in cases that were resistant to BEN or IDE individually, and those with deletion (del) 17p. CD40L/interleukin 4 (IL4) co-treatment mimicking the CLL microenvironment increased resistance to IDE, but synergy was retained. PI3Kδ-deficient murine splenic B cells were more resistant to IDE and showed reduced synergy with BEN, thus confirming the importance of functional PI3Kδ protein. Although IDE was observed to induce γH2AX, IDE did not enhance activation of the DNA damage response nor DNA repair activity. Interestingly, IDE decreased global RNA synthesis and was antagonistic with 5,6-Dichlorobenzimidazole 1-b-D-ribofuranoside (DRB), an inhibitor of transcription. These findings add to the increasingly complex cellular effects of IDE, and B cell receptor (BCR) inhibitors in general, in CLL.
Assuntos
Biomarcadores Tumorais/genética , Leucemia Linfocítica Crônica de Células B/diagnóstico , Mucosa Bucal/patologia , Índice de Gravidade de Doença , Homeostase do Telômero/genética , Idoso , Estudos de Casos e Controles , Comorbidade , Feminino , Seguimentos , Humanos , Leucemia Linfocítica Crônica de Células B/genética , Masculino , Mucosa Bucal/metabolismo , PrognósticoRESUMO
The shelterin proteins play important roles in telomere maintenance and genome stability. These proteins have been found to be mutated in many cancers including CLL. Herein, we demonstrate here the presence of a novel spliced isoform of TIN2S in chronic lymphocytic leukemia (CLL), related to deletion of exon 2 in the TIN2 gene. The expressions of spliced TIN2S mRNA varied widely in CLL and there was an inverse relationship between the mRNA levels of full-length TIN2S and the spliced moiety. Small amounts of spliced TIN2S were also observed in normal B cells but not in T cells. Spliced TIN2S appeared dysfunctional, as immunoprecipitation studies showed the typical association of TRF2 and TIN2 in normal lymphocytes but not in CLL cells. Moreover, whereas TRF2 localized to the nucleus in normal lymphocytes, it was present in both nuclei and cytoplasm in CLL cells. The levels of spliced TIN2S increased with age and in 3 of 8 patients increased over time. The presence of the spliced variant failed to be related to telomere length in CLL suggesting other functions for this protein. Further studies are required to determine the etiology and biological significance of this unique spliced TIN2S variant.
Assuntos
Leucemia Linfocítica Crônica de Células B/genética , Isoformas de Proteínas , Proteínas de Ligação a Telômeros/genética , Fatores Etários , Núcleo Celular/química , Citoplasma/química , Humanos , Leucemia Linfocítica Crônica de Células B/patologia , Linfócitos/metabolismo , Ligação Proteica , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , RNA Mensageiro , Complexo Shelterina , Telômero/ultraestrutura , Proteínas de Ligação a Telômeros/metabolismo , Proteína 2 de Ligação a Repetições Teloméricas/metabolismo , Fatores de TempoRESUMO
Bendamustine (BEN) has structural similarities to an alkylating agent and a nucleoside analog, and effective against tumor cells that are resistant to standard therapy. In this study we compared the activities of BEN against that of the alkylating agent, chlorambucil (CLB), and the nucleoside analogs, fludarabine (FLU) and deoxyadenosine/pentostatin (dADO/PEN), in primary chronic lymphocytic leukemia (CLL) cells in vitro. Cross-resistance was observed between BEN, CLB and FLU, with previously treated patients or those with a deletion 17p being most resistant. In contrast, some resistant CLL cells retained moderate sensitivity to dADO/PEN. Like FLU and CLB, BEN induced apoptosis through both the mitochondrial and death receptor pathways. There was a greater increase in DNA double-strand breaks (DSB) following FLU, as compared to BEN and CLB. Synergistic cytotoxicity was seen on combining BEN or CLB with FLU or dADO/PEN, but not when combining BEN with CLB. These results demonstrate that BEN acts as an alkylating agent, demonstrates cross-resistance to CLB and FLU and resistance to cells with a del 17p. Synergistic cytotoxic activity was seen between BEN and dADO/PEN suggesting that the combination of BEN and PEN should be evaluated in the clinic.