Purified murine hematopoietic stem cells function longer on nonirradiated W41/Wv than on +/+ irradiated stroma

Mouse bone marrow (BM) was separated into low-density, lineage- negative, wheat germ agglutinin-positive (WGA+), Rhodamine-123 bright (Rhbright) or dim (Rhdim) cells to obtain populations that were highly enriched for committed progenitors (Rhbright cells) or for more primitive stem cells (Rhdim). When 2,500 Rhbright or Rhdim cells were seeded onto 6-week-old irradiated (20 Gy) long-term BM cultures (LTBMC), the nonadherent cell production from Rhbright cells was transient and ended after 5 weeks. Production from Rhdim cells did not begin until week 3, peaked at week 5, and ended at week 8, when the irradiated stroma seemed to fail. Termination of cell production from Rhdim cells did not occur in nonirradiated LTBMC from W41/Wv mice. During peak nonadherent cell production, 25% to 30% of the cells in the nonirradiated LTBMC from W41/Wv mice had donor cell markers. Two approaches were tested to try to enhance the proportion or number of donor cells. Addition of Origen-HGF at the time of seeding Rhdim cells caused a nonspecific increase in both host and donor cell production, but a specific increase in production of donor cells was obtained by seeding the cultures at 2 weeks rather than 6 weeks. Limiting dilution of Rhdim cells gave the same frequency of wells producing cells on both irradiated +/+ and nonirradiated W41/Wv or W/Wv cultures.     

Mitotic Index is an Independent Predictor of Recurrence‐Free Survival in Meningioma

While World Health Organization (WHO) grading of meningioma stratifies patients according to recurrence risk overall, there is substantial within‐grade heterogeneity with respect to recurrence‐free survival (RFS). Most meningiomas are graded according to mitotic counts per unit area on hematoxylin and eosin sections, a method potentially confounded by tumor cellularity, as well as potential limitations of accurate mitotic figure detection on routine histology. To refine mitotic figure assessment, we evaluated 363 meningiomas with phospho‐histone H3 (Ser10) and determined the mitotic index (number of mitoses per 1000 tumor cells). The median mitotic indices among WHO grade I (n = 268), grade II (n = 84) and grade III (n = 11) tumors were 1, 4 and 12. Classification and regression tree analysis to categorize cut‐offs identified three subgroups defined by mitotic indices of 0–2, 3–4 and ≥5, which on univariate analysis were associated with RFS (P < 0.01). In multivariate analysis, mitotic index subgrouped in this manner was significantly associated with RFS (P < 0.01) after adjustment for Simpson grade, WHO grade and MIB‐1 index. Mitotic index was then examined within individual WHO grade, showing that for grade I and grade II meningiomas, mitotic index can add additional information to RFS risk. The results suggest that the use of a robust mitotic marker in meningioma could refine risk stratification.     

Enthalpy of hydrogen bond formation in a protein-ligand binding reaction.

Parallel measurements of the thermodynamics(free-energy, enthalpy, entropy and heat-capacity changes) of ligand binding toFK506 binding protein (FKBP-12) in H2O and D2O have been performed in an effortto probe the energetic contributions of single protein-ligand hydrogen bondsformed in the binding reactions. Changing tyrosine-82 to phenylalanine inFKBP-12 abolishes protein-ligand hydrogen bond interactions in the FKBP-12complexes with tacrolimus or rapamycin and leads to a large apparent enthalpicstabilization of binding in both H2O and D2O. High-resolution crystallographicanalysis reveals that two water molecules bound to the tyrosine-82 hydroxylgroup in unliganded FKBP-12 are displaced upon formation of the protein-ligandcomplexes. A thermodynamic analysis is presented that suggests that the removalof polar atoms from water contributes a highly unfavorable enthalpy change tothe formation of C=O...HO hydrogen bonds as they occur in the processes ofprotein folding and ligand binding. Despite the less favorable enthalpy change,the entropic advantage of displacing two water molecules upon binding leads to aslightly more favorable free-energy change of binding in the reactions withwild-type FKBP-12.     

Brain metastases from papillary thyroid carcinomas

Brain metastasis from papillary thyroid carcinoma (PTC) is extremely rare and carries a poor prognosis. We report nine cases (five females and four males) of brain metastasis of PTC. The age of patients ranged from 46 to 87 years old. The patients presented with nonspecific symptoms such as headaches. Brain metastasis was the first clinical presentation in three of nine patients; two of which had the aggressive tall cell variant of PTC. Six patients had prior history of PTC (four classic, one oncocytic variant, and one columnar cell variant) for 2 to 17 years with a median of 12 years. Gross total resection of brain metastasis was achieved for eight of our patients. Eight patients were treated with radioactive iodine. The median follow-up time was 12 months, ranging from 1 month to 4 years. Three patients died of their disease in 6 months, 21 months and 4 years, respectively after their first presentation of brain metastasis. It seems that these rare aggressive variants of PTC, such as tall cell variant, not only have higher propensity to develop brain metastasis, but also more frequently present with brain metastasis as their first clinical presentation than classic PTC. Furthermore, patients with PTC can develop brain metastasis even after many years.     

[11C]5-HTP and microPET are not suitable for pharmacodynamic studies in the rodent brain

The PET tracer [¹¹C]5-hydroxytryptophan ([¹¹C]5-HTP), which is converted to [¹¹C]5-hydroxytryptamine ([¹¹C]5-HT) by aromatic amino acid decarboxylase (AADC), is thought to measure 5-HT synthesis rates. But can we measure these synthesis rates by kinetic modeling of [¹¹C]5-HTP in rat? Male rats were scanned with [¹¹C]5-HTP (60 minutes) after different treatments. Scans included arterial blood sampling and metabolite analysis. 5-HT synthesis rates were calculated by a two-tissue compartment model (2TCM) with irreversible tracer trapping or Patlak analysis. Carbidopa (inhibitor peripheral AADC) dose-dependently increased [¹¹C]5-HTP brain uptake, but did not influence 2TCM parameters. Therefore, 10 mg/kg carbidopa was applied in all subsequent study groups. These groups included treatment with NSD 1015 (general AADC inhibitor) or p-chlorophenylalanine (PCPA, inhibitor of tryptophan hydroxylase, TPH). In addition, the effect of a low-tryptophan (Trp) diet was investigated. NSD 1015 or Trp depletion did not affect any model parameters, but PCPA reduced [¹¹C]5-HTP uptake, and the k₃. This was unexpected as NSD 1015 directly inhibits the enzyme converting [¹¹C]5-HTP to [¹¹C]5-HT, suggesting that trapping of radioactivity does not distinguish between parent tracer and its metabolites. As different results have been acquired in monkeys and humans, [¹¹C]5-HTP-PET may be suitable for measuring 5-HT synthesis in primates, but not in rodents.     

cIMPACT‐NOW update 7: advancing the molecular classification of ependymal tumors

Advances in our understanding of the biological basis and molecular characteristics of ependymal tumors since the latest iteration of the World Health Organization (WHO) classification of CNS tumors (2016) have prompted the cIMPACT‐NOW group to recommend a new classification. Separation of ependymal tumors by anatomic site is an important principle of the new classification and was prompted by methylome profiling data to indicate that molecular groups of ependymal tumors in the posterior fossa and supratentorial and spinal compartments are distinct. Common recurrent genetic or epigenetic alterations found in tumors belonging to the main molecular groups have been used to define tumor types at intracranial sites; C11orf95 and YAP1 fusion genes for supratentorial tumors and two types of posterior fossa ependymoma defined by methylation group, PFA and PFB. A recently described type of aggressive spinal ependymoma with MYCN amplification has also been included. Myxopapillary ependymoma and subependymoma have been retained as histopathologically defined tumor types, but the classification has dropped the distinction between classic and anaplastic ependymoma. While the cIMPACT‐NOW group considered that data to inform assignment of grade to molecularly defined ependymomas are insufficiently mature, it recommends assigning WHO grade 2 to myxopapillary ependymoma and allows grade 2 or grade 3 to be assigned to ependymomas not defined by molecular status.     

BRAF V600E mutant oligodendroglioma‐like tumors with chromosomal instability in adolescents and young adults

We performed genome‐wide methylation analysis on 136 pediatric low‐grade gliomas, identifying a unique cluster consisting of three tumors with oligodendroglioma‐like histology, BRAF p.V600E mutations and recurrent whole chromosome gains of 7 and loss of 10. Morphologically, all showed similar features, including a diffusely infiltrative glioma composed of round nuclei with perinuclear halos, a chicken‐wire pattern of branching capillaries and microcalcification. None showed astrocytic features or characteristics suggestive of high‐grade tumors including necrosis or mitotic figures. All tumors harbored multiple chromosomal copy number abnormalities (>10 chromosomes altered), but none showed 1p/19q co‐deletion or IDH1 p.R132H mutation. Hierarchical clustering and t‐stochastic neighbor embedding analyses from DNA methylation data cluster them more closely to previously described pediatric‐type low‐grade gliomas and separate from adult gliomas. These tumors exhibit distinct clinical features; they are temporal lobe lesions occurring in adolescents and young adults with a prolonged history of seizures and all are alive with no recurrence (follow‐up 3.2 to 13.2 years). We encountered another young adult case with quite similar pathological appearance and molecular status except for TERT promoter mutation. Although the series is small, these may represent a new category of IDH wild‐type low‐grade gliomas which may be confused with “molecular GBM.” Further, they highlight the heterogeneity of IDH wild‐type gliomas and the relatively indolent behavior of “pediatric‐type” gliomas.