Anita Y. Bahar

Inflammation is likely a key contributor to the pathogenesis of Parkinson's disease (PD), a progressively debilitating neurodegenerative disease that is accompanied by a pathological accumulation of the α-synuclein protein in a staged manner through the brain. What leads to the accumulation of α-synuclein in PD and how this relates to inflammatory pathways, however, is not entirely clear. Toll-like receptor (TLR) signaling is a major pathway mediating inflammation and, in particular, TLR2 is increasingly being implicated in PD. We have, therefore, examined the expression of TLR2 in postmortem brain tissue from PD patients and matched controls. We confirm that TLR2 is increased in PD brain, and find that levels of TLR2 correlate with the accumulation of pathological α-synuclein. TLR2 was expressed on neurons as well as microglia; however, the neuronal rather than glial expression of TLR2 was significantly increased in PD brain in accordance with disease staging, and TLR2 was strongly localized to α-synuclein positive Lewy bodies. In cell culture, activation of neuronal TLR2 induced an inflammatory response, including the secretion of inflammatory cytokines and microglial-activating chemokines, as well as the production of reactive oxygen species. Moreover, activation of neuronal TLR2 increased levels of endogenous α-synuclein protein, which was in turn associated with increased levels of the autophagy/lysosomal pathway marker p62. Finally, promoting autophagy with rapamycin or pharmacological inhibition of the TLR2 signaling pathway prevented the TLR2-mediated increase in α-synuclein in neuronal cell cultures. These results implicate neuronal TLR2 expression in human PD pathogenesis. In particular, the increased expression of TLR2 on neurons may provide new insight into disease pathogenesis and/or options for therapeutic intervention.

Relapse following remission induction chemotherapy remains a barrier to survival in approximately 20% of children suffering from acute lymphoblastic leukemia (ALL). To investigate the mechanism of relapse, 27 matched diagnosis and relapse ALL samples were analyzed for clonal populations using polymerase chain reaction (PCR)-based detection of multiple antigen receptor gene rearrangements. These clonal markers revealed the emergence of apparently new populations at relapse in 13 patients. More sensitive clone-specific PCR revealed that, in 8 cases, these "relapse clones" were present at diagnosis and a significant relationship existed between presence of the relapse clone at diagnosis and time to first relapse (P < .007). Furthermore, in cases where the relapse clone could be quantified, time to first relapse was dependent on the amount of the relapse clone at diagnosis (r = -0.84; P = .018). This observation, together with demonstrated differential chemosensitivity between subclones at diagnosis, argues against therapy-induced acquired resistance as the mechanism of relapse in the informative patients. Instead these data indicate that relapse in ALL patients may commonly involve selection of a minor intrinsically resistant subclone that is undetectable by routine PCR-based methods. Relapse prediction may be improved with strategies to detect minor potentially resistant subclones early during treatment, hence allowing intensification of therapy.

UNLABELLED: The relative timing of genetic alterations that contribute to follicular lymphoma remains unknown. We analyzed a donor-recipient pair who both developed grade 2/3A follicular lymphoma 7 years after allogeneic transplantation and donor lymphocyte infusions. Both patients harbored identical BCL2/IGH rearrangements also present in 1 in 2,000 cells in the donor lymphocyte infusion, and the same V(D)J rearrangement, which underwent somatic hypermutation both before and after clonal divergence. Exome sequencing of both follicular lymphomas identified 15 shared mutations, of which 14 (including alterations in EP300 and KLHL6) were recovered from the donor lymphocyte infusion by ultra-deep sequencing (average read coverage, 361,723), indicating acquisition at least 7 years before clinical presentation. Six additional mutations were present in only one follicular lymphoma and not the donor lymphocyte infusion, including an ARID1A premature stop, indicating later acquisition during clonal divergence. Thus, ultrasensitive sequencing can map clonal evolution within rare subpopulations during human lymphomagenesis in vivo. SIGNIFICANCE: For the first time, we define the molecular ontogeny of follicular lymphoma during clonal evolution in vivo. By using ultrasensitive mutation detection, we mapped the time-course of somatic alterations after passage of a malignant ancestor by hematopoietic cell transplantation.