The mutant form of lamin A responsible for the premature aging disease Hutchinson-Gilford progeria syndrome (termed progerin) acts as a dominant negative protein that changes the structure of the nuclear lamina. How the perturbation of the nuclear lamina in progeria is transduced into cellular changes is undefined. Using patient fibroblasts and a variety of cell-based assays, we determined that progerin expression in Hutchinson-Gilford progeria syndrome inhibits the nucleocytoplasmic transport of several factors with key roles in nuclear function. We found that progerin reduces the nuclear/cytoplasmic concentration of the Ran GTPase and inhibits the nuclear localization of Ubc9, the sole E2 for SUMOylation, and of TPR, the nucleoporin that forms the basket on the nuclear side of the nuclear pore complex. Forcing the nuclear localization of Ubc9 in progerin-expressing cells rescues the Ran gradient and TPR import, indicating that these pathways are linked. Reducing nuclear SUMOylation decreases the nuclear mobility of the Ran nucleotide exchange factor RCC1 in vivo, and the addition of SUMO E1 and E2 promotes the dissociation of RCC1 and Ran from chromatin in vitro. Our data suggest that the cellular effects of progerin are transduced, at least in part, through reduced function of the Ran GTPase and SUMOylation pathways.The nuclear lamina provides an architectural framework that defines the size, shape, and physical properties of the nucleus (29). A critical function of the nuclear lamina is to provide a scaffold for chromatin attachment, and there is a growing body of evidence linking the nuclear lamina to the regulation of gene expression and chromosome positioning within interphase cells (49). The nuclear periphery, including the region proximal to the lamina, is rich in heterochromatin and provides a nuclear subcompartment that promotes transcriptional silencing (19). The mechanisms responsible for transcriptional silencing associated with the lamina appear to involve epigenetic regulation and modulation of the higherorder chromatin structure (2). Other functions of the lamina include roles in DNA replication and apoptosis (22,29). The principal components of the lamina are lamin A/C and lamin B, which are encoded by the LMNA and LMNB genes, respectively (22, 29). More than 300 mutations in LMNA have been described (http://www.umd.be/LMNA/) and have been linked to 12 diseases collectively known as laminopathies. These diseases include dilated cardiomyopathy with conduction defects (DCM-CD), familial partial lipodystrophy (FPLD), atypical Werner's syndrome, Emery-Dreifuss muscular dystrophy (EDMD), and Hutchinson-Gilford progeria syndrome (HGPS) (9, 70, 77).The nuclear lamina also provides a scaffold for organizing nuclear pore complexes (NPCs) within the nuclear membrane (1). NPCs span the nuclear lamina and both the inner and outer nuclear membranes and serve as conduits for nuclear import and export (73). Nucleoporins that comprise the NPC are organized into subcomplexes that disassemble and reassemble duri...

Background: Liquid biopsy for plasma circulating tumor DNA (ctDNA) next-generation sequencing (NGS) is commercially available and increasingly adopted in clinical practice despite a paucity of prospective data to support its use. Methods: Patients with advanced lung cancers who had no known oncogenic driver or developed resistance to current targeted therapy (n ¼ 210) underwent plasma NGS, targeting 21 genes. A subset of patients had concurrent tissue NGS testing using a 468-gene panel (n ¼ 106). Oncogenic driver detection, test turnaround time (TAT), concordance, and treatment response guided by plasma NGS were measured. All statistical tests were two-sided. Results: Somatic mutations were detected in 64.3% (135/210) of patients. ctDNA detection was lower in patients who were on systemic therapy at the time of plasma collection compared with those who were not (30/70, 42.9% vs 105/140, 75.0%; OR ¼ 0.26, 95% CI ¼ 0.1 to 0.5, P < .001). The median TAT of plasma NGS was shorter than tissue NGS (9 vs 20 days; P < .001). Overall concordance, defined as the proportion of patients for whom at least one identical genomic alteration was identified in both tissue and plasma, was 56.6% (60/106, 95% CI ¼ 46.6% to 66.2%). Among patients who tested plasma NGS positive, 89.6% (60/ 67; 95% CI ¼ 79.7% to 95.7%) were also concordant on tissue NGS and 60.6% (60/99; 95% CI ¼ 50.3% to 70.3%) vice versa. Patients who tested plasma NGS positive for oncogenic drivers had tissue NGS concordance of 96.1% (49/51, 95% CI ¼ 86.5% to 99.5%), and directly led to matched targeted therapy in 21.9% (46/210) with clinical response. Conclusions: Plasma ctDNA NGS detected a variety of oncogenic drivers with a shorter TAT compared with tissue NGS and matched patients to targeted therapy with clinical response. Positive findings on plasma NGS were highly concordant with tissue NGS and can guide immediate therapy; however, a negative finding in plasma requires further testing. Our findings support the potential incorporation of plasma NGS into practice guidelines.

TTF-1 expression was evaluable in 479 (75%) of all patients reviewed, and was positive in 383 (80%, 95% CI 76-83%). Clinicopathologic features were similar between TTF-1 positive and TTF-1 negative tumors, except EGFR mutations were more common in TTF-1 positive cases (24% vs 6%, p<0.001). In univariate analysis, overall survival was significantly longer in patients with TTF-1 positive versus TTF-1 negative tumors (18 months vs 9 months, p<0.0001). In multivariate analysis, TTF-1 positivity remained associated with better overall survival (HR=0.38, p<0.0001), exceeding the prognostic impact of Karnofsky performance status >/=80% (HR 0.62, p=0.0003) and receipt of first-line combination chemotherapy or targeted therapy (HR relative to first-line single agent chemotherapy 0.59, p=0.05 and 0.51, p=0.05 respectively). Both patients with TTF-1 positive and TTF-1 negative cancers had longer durations of initial therapy when treated with pemetrexed-based chemotherapy. In patients with advanced lung adenocarcinomas, TTF-1 expression is associated with better survival but is not predictive of distinct benefit from pemetrexed-based chemotherapy.

PP2A comprising B56 regulatory subunit isoforms (PP2A) is a serine/threonine phosphatase essential for mitosis. At the kinetochore, PP2A both stabilizes microtubule binding and promotes silencing of the spindle assembly checkpoint (SAC) through its association with the SAC protein BubR1. Cells depleted of the B56 regulatory subunits of PP2A are delayed in activation of Cdc20-containing APC/C (APC/C), which is an essential step for mitotic exit. It has been hypothesized that this delay arises from increased production of the mitotic checkpoint complex (MCC), an APC/C inhibitor formed at unattached kinetochores through SAC signaling. In contrast to this prediction, we show that depletion of B56 subunits does not increase the amount or stability of the MCC. Rather, delays in APC/C activation in B56-depleted cells correlate with impaired Cdc20 binding to APC/C. Stimulation of APC/C assembly does not require binding between PP2A and BubR1, and thus this contribution of PP2A towards mitotic exit is distinct from its functions at kinetochores. PP2A associates with APC/C constitutively in a BubR1-independent manner. A mitotic phosphorylation site on Cdc20, known to be a substrate of PP2A, modulates APC/C assembly. These results elucidate the contributions of PP2A towards completion of mitosis.