RESUMEN
JSI-124 (cucurbitacin I) has been recently described as a specific inhibitor of signal transducer and activator of transcription-3 (STAT3). As STAT3 activation is pathogenetically important in anaplastic lymphoma kinase-positive anaplastic large cell lymphoma (ALK+ ALCL), we investigated whether JSI-124 can mediate significant inhibitory effects in this cell type. In two ALK+ ALCL cell lines (Karpas 299 and SU-DHL-1), JSI-124 significantly reduced the number of viable cells to 50% of that of negative controls at a dose of 5-10 micromol/l at 24 h and 1-1.25 micromol/l at 48 h. This decrease in viability was associated with apoptosis, as confirmed by the increase in the subG(0/1) fraction, poly(ADP-ribose)polymerase cleavage and expression of active caspase 3. JSI-124 decreased the phosphorylated-STAT3 and -Janus kinase-3 (JAK3) levels in a dose-dependent fashion, and these changes were coupled with significant decreases in several STAT3 downstream targets, including mcl-1, bcl-2, bcl-xL and cyclin D3. Interestingly, JSI-124 also dramatically decreased the protein levels of JAK3 and nucleophosmin (NPM)-ALK, and these effects were reversible by MG132. Our data support that JSI-124 is a potentially useful therapeutic agent for ALK+ ALCL. In addition to its role as a tyrosine kinase inhibitor, JSI-124 appears to be involved in regulating proteosome degradation for proteins such as JAK3 and NPM-ALK.
Asunto(s)
Antineoplásicos/farmacología , Apoptosis/efectos de los fármacos , Linfoma de Células B Grandes Difuso/patología , Proteínas Tirosina Quinasas/antagonistas & inhibidores , Triterpenos/farmacología , Western Blotting , Relación Dosis-Respuesta a Droga , Regulación hacia Abajo/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Humanos , Janus Quinasa 3 , Linfoma de Células B Grandes Difuso/enzimología , Proteínas Tirosina Quinasas/biosíntesis , Transducción de Señal/efectos de los fármacos , Células Tumorales CultivadasRESUMEN
Previous studies showed that most cases of ALK(+) anaplastic large-cell lymphoma (ALK(+)ALCL) do not express SHP1, a tyrosine phosphatase and an important negative regulator for cellular signaling pathways such as that of JAK/STAT. To fully assess the biologic significance of loss of SHP1 in ALK(+)ALCL, we transfected SHP1 plasmids into 2 SHP1(-), ALK(+)ALCL cell lines, Karpas 299 and SU-DHL-1. After 24 hours of transfection, pJAK3 and pSTAT3 were decreased, and these changes correlated with down-regulation of STAT3 downstream targets including cyclin D3, mcl-1, and bcl-2. Expression of SHP1 in these 2 cell lines also resulted in marked decreases in the protein levels of JAK3 and NPM-ALK, and these effects were reversible by proteosome inhibitor MG132. Conversely, when SHP1 expression in SUP-M2 (a SHP1(+) ALK(+)ALCL cell line) was inhibited using siRNA, pSTAT3, pJAK3, JAK3, and NPM-ALK were all up-regulated. Coimmunoprecipitation studies showed that SHP1 was physically associated with JAK3 and NPM-ALK. SHP1 expression in Karpas 299 and SU-DHL-1 led to significant G(1) cell cycle arrest but not apoptosis. To conclude, loss of SHP1 contributes to the pathogenesis of ALK(+)ALCL by 2 mechanisms: (1) it leaves the tyrosine phosphorylation and activation of JAK3/STAT3 unchecked and (2) it decreases proteosome degradation of JAK3 and NPM-ALK.
Asunto(s)
Péptidos y Proteínas de Señalización Intracelular/metabolismo , Linfoma de Células B Grandes Difuso/metabolismo , Proteínas Tirosina Fosfatasas/metabolismo , Proteínas Tirosina Quinasas/metabolismo , Factor de Transcripción STAT3/metabolismo , Apoptosis , Secuencia de Bases , Ciclo Celular , Línea Celular Tumoral , Expresión Génica , Humanos , Péptidos y Proteínas de Señalización Intracelular/antagonistas & inhibidores , Péptidos y Proteínas de Señalización Intracelular/genética , Janus Quinasa 3 , Linfoma de Células B Grandes Difuso/genética , Complejo de la Endopetidasa Proteasomal/metabolismo , Proteína Tirosina Fosfatasa no Receptora Tipo 6 , Proteínas Tirosina Fosfatasas/antagonistas & inhibidores , Proteínas Tirosina Fosfatasas/genética , Proteínas Tirosina Quinasas/genética , ARN Neoplásico/genética , ARN Interferente Pequeño/genética , Factor de Transcripción STAT3/genética , Transducción de Señal , TransfecciónRESUMEN
Mantle cell lymphoma is an aggressive B-cell lymphoma for which the biology is incompletely understood. Previous studies have reported that somatic hypermutation of the variable region of the immunoglobulin heavy chain gene (V(H)), as commonly defined as <98% homology, can be detected in approximately one-third of mantle cell lymphoma, although the V(H) mutation status has not been found to significantly correlate with patient survival. In this study, we assessed V(H) mutation in 55 mantle cell lymphomas using a method slightly different from those used in the previous studies, and we came to different conclusions. Using DNA extracted from formalin-fixed/paraffin-embedded tumors in all cases, we identified monoclonal IGH bands in 54 of 55 cases with the FR1c/J(H) primer; a monoclonal IGH band was amplified using another IGH primer set, FR256/J(H), in the remaining case. Cloning was performed in all cases, and an average of six clones were sequenced and analyzed for each case. Intraclonal heterogeneity was detected in 45 (82%) cases. Further analysis was performed in 53 cases, in which a predominant IGH species was identified. Most (32 of 53 cases, 60%) cases were 'mutated', with <98% homology. V(H)1-69, V(H)4-59 and V(H)3-74 were utilized in 29 (55%) cases. Intraclonal evolution and non-productive V(H) rearrangements were more frequent in the mutated group. Patients with the 'mutated' genotype had longer overall survival (P=0.017, Log rank) that is independent of the international prognostic index. To conclude, our data suggest that the V(H) mutation frequency in mantle cell lymphoma may be higher than previously believed. Importantly, using our methodology, we found that the V(H) mutation status may be a useful prognostic marker for these patients.