Balloon cells of distinct focal cortical dysplasias type IIb (FCD(IIb)) and giant cells of cortical tubers in tuberous sclerosis (TSC) constitute neuropathological hallmarks and cytological similarities. In TSC, frequent mutations in the TSC1 or TSC2 genes result in mTOR-signaling activity. Here, we addressed whether Pi3K-pathway activation differentiates balloon cells from giant cells. We used immunohistochemistry with antibodies against p-PDK1 (S241), p-Akt (S473), p-tuberin (T1462), p-p70(S6K) (T389), p-p70(S6K) (T229) and phalloidin-staining to analyze stress fiber formation in balloon cells of FCD(IIb) (n = 23) compared with cortical tuber giant cells (n = 5) and adjacent normal CNS tissue as control. We have further established an in vitro assay to assess potential phosphorylation between Akt and S6. We observed phosphorylated (p-)PDK1, p-Akt, p-tuberin, and p-p70-kDa S6-kinase (p-p70(S6K); residue T229) in balloon cells, whereas giant cells showed only equivalent levels of p-tuberin, p-p70(S6K) and stress fibers. Furthermore, Pi3K-cascade activity in balloon cells may reflect pathway "cross-talk". An in vitro assay revealed S6, a major target of p70(S6K), to increase phosphorylation of Akt. Our data suggest recruitment of different Pi3K-cascade factors in the molecular pathogenesis of giant cells in cortical tubers vs. balloon cells in FCD(IIb) and provides new implications for the development of treatment strategies for these cortical malformations.

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Focal cortical dysplasias (FCD) with Taylor-type balloon cells (FCD(IIb)) are frequently observed in biopsy specimens of patients with pharmacoresistant focal epilepsies. The molecular pathogenesis of FCD(IIb), which lack familial inheritance, is only poorly understood. Due to their highly differentiated, malformative nature and glioneuronal phenotype, FCD(IIb) share neuropathological characteristics with lesions observed in familial disorders such as cortical tubers present in patients with autosomal dominant tuberous sclerosis complex (TSC), related to mutations in the TSC1 or TSC2 genes, and dysplastic gangliocytomas of the cerebellum found in Cowden disease. Current data have indicated distinct allelic variants of TSC1 to accumulate in FCD(IIb). TSC1 represents a tumor suppressor operating in the phosphatidylinositol 3-kinase (PI3K)/insulin pathway. The tumor-suppressor gene PTEN is mutated in Cowden disease. Like PTEN, also carboxyl-terminal modulator protein (CTMP) modulates PI3K-pathway signaling, both via inhibition of Akt/PKB, a kinase inactivating the TSC1/TSC2 complex. Here, we have analyzed alterations of Akt, PTEN and CTMP relevant for insulin signaling upstream of TSC1/TSC2 in FCD(IIb). Immunohistochemistry with antibodies against phosphorylated Akt (phospho-Akt; Ser 473) in FCD(IIb) (n=23) showed strong phospho-Akt expression in dysplastic FCD(IIb) components. We have further studied sequence alterations of PTEN (n=34 FCD(IIb)) and CTMP (n=20 FCD(IIb)) by laser microdissection/single-strand conformation polymorphism analysis. We observed a somatic mutation in an FCD(IIb), i.e., amino-acid exchange at nucleotide position 834 (PTEN cDNA, GenBank AH007803.1) in exon 8 with replacement of phenylalanine by leucine (F278L). We also found several silent polymorphisms of PTEN in exon 2 and exon 8 as well as silent and coding polymorphisms but no mutations in CTMP. No loss of heterozygosity in FCD(IIb) (n=6) at 10q23 was observed. To our knowledge, we here report on the first somatic mutation of a tumor-suppressor gene, i.e., PTEN, in FCD(IIb). However, our study also demonstrates that mutational alterations of PTEN and CTMP do not play major pathogenetic roles for activation of Akt in FCD(IIb). Future studies need to determine the origin of insulin pathway activation upstream of TSC1/TSC2 in FCD(IIb).

Summary: Low-grade glioneuronal lesions involving tumors such as gangliogliomas and focal cortical dysplasias (FCD) predispose individuals to pharmacoresistant epilepsy. A frequent variant of FCD is composed of dysplastic cytomegalic neurons and Taylor-type balloon cells (FCD IIb ). Those are similar to cellular elements, which are present in cortical tubers in the autosomal dominant inherited tuberous sclerosis complex (TSC). This phacomatosis is caused by mutations in the TSC1 or TSC2 genes. Recent data have indicated accumulation of distinct allelic variants of TSC1 also in FCD IIb . TSC1 represents a key factor in the phosphatidylinositol 3-kinase (PI3K) pathway. A variety of alterations in the PI3K-pathway have been recently reported in epilepsy-associated glioneuronal malformations. Here, we discuss pathogenetic similarities and differences between cortical dysplasias as well epilepsyassociated glioneuronal tumors and TSC-associated cortical tubers with a focus on PI3K-pathway components including ezrin, radixin and moesin (ERM), which represent downstream effectors involved in cytoskeleton-membrane interference. No evidence has been found for mutational events of ERM genes to play a major pathogenetic role in epilepsy-associated glioneuronal malformations. In contrast, aberrant expression of ERM proteins in FCDs and gangliogliomas was observed. These alterations may relate to compromised interactions of dysplastic cellular components in epilepsy-associated glioneuronal lesions and be involved in aberrant PI3K-pathway signaling in epilepsy-associated malformations. However, the underlying cause of PI3K-pathway activation and the functional relationship of PI3K-pathway activity to generation of seizures in epilepsyassociated glioneuronal lesions will need to be determined in the future.

IntroductionObjective of our study was to determine the agreement between version 1 (v1) and v2 of the Prostate Imaging Reporting and Data System (PI-RADS) for evaluation of multiparametric prostate MRI (mpMRI) and to compare their diagnostic accuracy, their inter-observer agreement and practicability.Material and MethodsmpMRI including T2-weighted imaging, diffusion-weighted imaging (DWI) and dynamic contrast-enhanced imaging (DCE) of 54 consecutive patients, who subsequently underwent MRI-guided in-bore biopsy were re-analyzed according to PI-RADS v1 and v2 by two independent readers. Diagnostic accuracy for detection of prostate cancer (PCa) was assessed using ROC-curve analysis. Agreement between PI-RADS versions and observers was calculated and the time needed for scoring was determined.ResultsMRI-guided biopsy revealed PCa in 31 patients. Diagnostic accuracy for detection of PCa was equivalent with both PI-RADS versions for reader 1 with sensitivities and specificities of 84%/91% (AUC = 0.91 95%CI[0.8–1]) for PI-RADS v1 and 100%/74% (AUC = 0.92 95% CI[0.8–1]) for PI-RADS v2. Reader 2 achieved similar diagnostic accuracy with sensitivity and specificity of 74%/91% (AUC = 0.88 95%CI[0.8–1]) for PI-RADS v1 and 81%/91% (AUC = 0.91 95%CI[0.8–1]) for PI-RADS v2. Agreement between scores determined with different PI-RADS versions was good (reader 1: κ = 0.62, reader 2: κ = 0.64). Inter-observer agreement was moderate with PI-RADS v2 (κ = 0.56) and fair with v1 (κ = 0.39). The time required for building the PI-RADS score was significantly lower with PI-RADS v2 compared to v1 (24.7±2.3 s vs. 41.9±2.6 s, p<0.001).ConclusionAgreement between PI-RADS versions was high and both versions revealed high diagnostic accuracy for detection of PCa. Due to better inter-observer agreement for malignant lesions and less time demand, the new PI-RADS version could be more practicable for clinical routine.