We analyzed 28 thymic epithelial tumors (TETs) using next-generation sequencing and identified a missense mutation (chromosome 7 c.74146970T>A) in GTF2I at high frequency in type A thymomas, a relatively indolent subtype. In a series of 274 TETs, we detected the GTF2I mutation in 82% of type A and 74% of type AB thymomas but rarely in the aggressive subtypes, where recurrent mutations of known cancer genes have been identified. Therefore, GTF2I mutation correlated with better survival. GTF2I β and δ isoforms were expressed in TETs, and both mutant isoforms were able to stimulate cell proliferation in vitro. Thymic carcinomas carried a higher number of mutations than thymomas (average of 43.5 and 18.4, respectively). Notably, we identified recurrent mutations of known cancer genes, including TP53, CYLD, CDKN2A, BAP1 and PBRM1, in thymic carcinomas. These findings will complement the diagnostic assessment of these tumors and also facilitate development of a molecular classification and assessment of prognosis and treatment strategies.

Summary Background No standard treatments are available for advanced thymic epithelial tumours after failure of platinum-based chemotherapy. We investigated the activity of sunitinib, an orally administered tyrosine kinase inhibitor. Methods Between May 15, 2012, and Oct 2, 2013, we did an open-label phase 2 trial in patients with histologically confirmed chemotherapy-refractory thymic epithelial tumours. Patients were eligible if they had disease progression after at least one previous regimen of platinum-containing chemotherapy, an Eastern Cooperative Oncology Group performance status of two or lower, measurable disease, and adequate organ function. Patients received 50 mg of sunitinib orally once a day, in 6-week cycles (ie, 4 weeks of treatment followed by 2 weeks without treatment), until tumour progression or unacceptable toxic effects arose. The primary endpoint was investigator-assessed best tumour response at any point, which we analysed separately in thymoma and thymic carcinoma cohorts. Patients who had received at least one cycle of treatment and had their disease reassessed were included in the analyses of response. The trial was registered with ClinicalTrials.gov, number NCT01621568. Findings 41 patients were enrolled, 25 with thymic carcinoma and 16 with thymoma. One patient with thymic carcinoma was deemed ineligible after enrolment and did not receive protocol treatment. Of patients who received treatment, one individual with thymic carcinoma was not assessable because she died. Median follow-up on trial was 17 months (IQR 14·0–18·4). Of 23 assessable patients with thymic carcinoma, six (26%, 90% CI 12·1–45·3, 95% CI 10·2–48·4) had partial responses, 15 (65%, 95% CI 42·7–83·6) achieved stable disease, and two (9%, 1·1–28·0) had progressive disease. Of 16 patients with thymoma, one (6%, 95% CI 0·2–30·2) had a partial response, 12 (75%, 47·6–92·7) had stable disease, and three (19%, 4·1–45·7) had progressive disease. The most common grade 3 and 4 treatment-related adverse events were lymphocytopenia (eight [20%] of 40 patients), fatigue (eight [20%]), and oral mucositis (eight [20%]). Five (13%) patients had decreases in left-ventricular ejection fraction, of which three (8%) were grade 3 events. Three (8%) patients died during treatment, including one individual who died of cardiac arrest that was possibly treatment-related. Interpretation Sunitinib is active in previously treated patients with thymic carcinoma. Further studies are needed to identify potential biomarkers of activity. Funding National Cancer Institute (Cancer Therapy Evaluation Program).

Purpose We conducted a basket clinical trial to assess the feasibility of such a design strategy and to independently evaluate the effects of multiple targeted agents against specific molecular aberrations in multiple histologic subtypes concurrently. Patients and Methods We enrolled patients with advanced non–small-cell lung cancer (NSCLC), small-cell lung cancer, and thymic malignancies who underwent genomic characterization of oncogenic drivers. Patients were enrolled onto a not-otherwise-specified arm and treated with standard-of-care therapies or one of the following five biomarker-matched treatment groups: erlotinib for EGFR mutations; selumetinib for KRAS, NRAS, HRAS, or BRAF mutations; MK2206 for PIK3CA, AKT, or PTEN mutations; lapatinib for ERBB2 mutations or amplifications; and sunitinib for KIT or PDGFRA mutations or amplification. Results Six hundred forty-seven patients were enrolled, and 88% had their tumors tested for at least one gene. EGFR mutation frequency was 22.1% in NSCLC, and erlotinib achieved a response rate of 60% (95% CI, 32.3% to 83.7%). KRAS mutation frequency was 24.9% in NSCLC, and selumetinib failed to achieve its primary end point, with a response rate of 11% (95% CI, 0% to 48%). Completion of accrual to all other arms was not feasible. In NSCLC, patients with EGFR mutations had the longest median survival (3.51 years; 95% CI, 2.89 to 5.5 years), followed by those with ALK rearrangements (2.94 years; 95% CI, 1.66 to 4.61 years), those with KRAS mutations (2.3 years; 95% CI, 2.3 to 2.17 years), those with other genetic abnormalities (2.17 years; 95% CI, 1.3 to 2.74 years), and those without an actionable mutation (1.85 years; 95% CI, 1.61 to 2.13 years). Conclusion This basket trial design was not feasible for many of the arms with rare mutations, but it allowed the study of the genetics of less common malignancies.

A B S T R A C T PurposeA key challenge in the treatment of thymoma and thymic carcinoma (TC) is in improving our understanding of the molecular biology of these relatively rare tumors. In recent years, significant efforts have been made to dissect the molecular pathways involved in their carcinogenesis. Here we discuss the results of large-scale genomic analyses conducted to date and review the most active chemotherapies and targeted treatments. MethodsWe reviewed the literature for chemotherapeutic trials in the last 20 years and trials involving targeted therapies between

Poly(ADP-ribose)polymerase 1 (PARP1) is well characterized for its role in base excision repair (BER), where it is activated by and binds to DNA breaks and catalyzes the poly(ADP-ribosyl)ation of several substrates involved in DNA damage repair. Here we demonstrate that PARP1 associates with telomere repeat binding factor 2 (TRF2) and is capable of poly(ADP-ribosyl)ation of TRF2, which affects binding of TRF2 to telomeric DNA. Immunostaining of interphase cells or metaphase spreads shows that PARP1 is detected sporadically at normal telomeres, but it appears preferentially at eroded telomeres caused by telomerase deficiency or damaged telomeres induced by DNA-damaging reagents. Although PARP1 is dispensable in the capping of normal telomeres, Parp1 deficiency leads to an increase in chromosome end-to-end fusions or chromosome ends without detectable telomeric DNA in primary murine cells after induction of DNA damage. Our results suggest that upon DNA damage, PARP1 is recruited to damaged telomeres, where it can help protect telomeres against chromosome end-to-end fusions and genomic instability.

The Cdc14 dual-specificity phosphatases regulate key events in the eukaryotic cell cycle. However, little is known about the function of mammalian CDC14B family members. Here, we demonstrate that subcellular localization of CDC14B protein is cell cycle regulated. CDC14B can bind, bundle, and stabilize microtubules in vitro independently of its catalytic activity. Basic amino acid residues within the nucleolar targeting domain are important for both retaining CDC14B in the nucleolus and preventing microtubule bundling. Overexpression of CDC14B resulted in the formation of cytoplasmic CDC14B and microtubule bundles in interphase cells. These microtubule bundles were resistant to microtubule depolymerization reagents and enriched in acetylated ␣-tubulin. Expression of cytoplasmic forms of CDC14B impaired microtubule nucleation from the microtubule organization center. CDC14B is thus a novel microtubule-bundling and -stabilizing protein, whose regulated subcellular localization may help modulate spindle and microtubule dynamics in mitosis.

The stability of many proteins is controlled by the ubiquitin proteolytic system, which recognizes specific substrates through the action of E3 ubiquitin ligases [1]. The SCFs are a recently described class of ubiquitin ligase that target a number of cell cycle regulators and other proteins for degradation in both yeast and mammalian cells [2] [3] [4] [5] [6]. Each SCF complex is composed of the core protein subunits Skp1, Rbx1 and Cul1 (known as Cdc53 in yeast), and substrate-specific adaptor subunits called F-box proteins [2] [3] [4]. To understand the physiological role of SCF complexes in mammalian cells, we generated mice carrying a deletion in the Cul1 gene. Cul1(-/-) embryos arrested around embryonic day 6.5 (E6.5) before the onset of gastrulation. In all cells of the mutant embryos, cyclin E protein, but not mRNA, was highly elevated. Outgrowths of Cul1(-/-) blastocysts had limited proliferative capacity in vitro and accumulated cyclin E in all cells. Within Cul1(-/-) blastocyst cultures, trophoblast giant cells continued to endocycle despite the elevated cyclin E levels. These results suggest that cyclin E abundance is controlled by SCF activity, possibly through SCF-dependent degradation of cyclin E.

Genetic alterations and etiology of thymic epithelial tumors (TETs) are largely unknown, hampering the development of effective targeted therapies for patients with TETs. Here TETs of advanced-stage patients enrolled in a clinical trial of molecularly-guided targeted therapies were employed for targeted sequencing of 197 cancer-associated genes. Comparative sequence analysis of 78 TET/blood paired samples obtained from 47 thymic carcinoma (TC) and 31 thymoma patients revealed a total of 86 somatic non-synonymous sequence variations across 39 different genes in 33 (42%) TETs. TCs (62%; 29/47) showed higher incidence of somatic non-synonymous mutations than thymomas (13%; 4/31; p < 0.0001). TP53 was the most frequently mutated gene in TETs (n = 13; 17%), especially in TCs (26%), and was associated with a poorer overall survival (p < 0.0001). Genes in histone modification [BAP1 (n = 6; 13%), SETD2 (n = 5; 11%), ASXL1 (n = 2; 4%)], chromatin remodeling [SMARCA4 (n = 2; 4%)], and DNA methylation [DNMT3A (n = 3; 7%), TET2 (n = 2; 4%), WT1 (n = 2; 4%)] pathways were recurrently mutated in TCs, but not in thymomas. Our results suggest a potential disruption of epigenetic homeostasis in TCs, and a substantial difference in genetic makeup between TCs and thymomas. Further investigation is warranted into the roles of epigenetic dysregulation in TC development and its potential for targeted therapy.