Katharina Pauls

Gastrointestinal stromal tumors (GIST) are characterized by a strong KIT receptor activation most often resulting from KIT mutations. In a smaller subgroup of tumors without KIT mutations, analogous activating mutations are found in the platelet-derived growth factor receptor alpha (PDGFRalpha) gene. Both PDGFRalpha and KIT receptors are targets of the tyrosine kinase inhibitor imatinib (Glivec) which has improved the treatment of advanced GISTs significantly. However, a subgroup of tumors show a secondary progress under therapy with imatinib after initial response. One possible mechanism of secondary resistance is the development of newly acquired KIT mutations. In the present study, we evaluated the frequency of such secondary KIT mutations in a series of GIST patients in which tumor tissue was resected under treatment. We examined one to seven different tumor areas in 32 cases (total of 104 samples) and found up to four newly acquired KIT mutations in 14 patients (43.8%). These were always located in exons encoding the first or second tyrosine kinase domain (exon 13, 14, or 17). Mutations were found only in a subset of samples analyzed from each case whereas others retained the wild-type sequence in the same region. There was never more than one new mutation in the same sample. Consistent with a secondary clonal evolution, the primary mutation was always detectable in all samples from each tumor. According to our results, the identification of newly acquired KIT mutations in addition to the primary mutation is dependent on the number of tissue samples analyzed and has high implications for further therapeutic strategies.

Mutations in the valosin-containing protein (VCP) gene on chromosome 9p13-p12 recently have been shown to cause autosomal dominant inclusion body myopathy associated with Paget's disease of the bone and frontotemporal dementia. Here, we report the central nervous system autopsy findings in a 55-year-old German patient with inclusion body myopathy and frontotemporal dementia who harbors a heterozygous R155C missense mutation residing in the N-terminal CDC48 domain of VCP, which is involved in ubiquitin binding. We demonstrate that mutant VCP causes a novel type of frontotemporal dementia characterized by neuronal nuclear inclusions containing ubiquitin and VCP.

BACKGROUND: The aim of the present study was to examine fetal male germ cells for expression of proteins associated with differentiation and maturation and to compare them with morphologically defined subpopulations. METHODS: Testes of 61 fetuses from week 12 of gestation to the newborn period were selected. Immunohistochemistry was performed using antibodies to proteins associated with differentiation of germ cells (c-KIT, AP-2gamma) or pluripotency (OCT3/4), oncofetal protein M2A and spermatogonial marker MAGE-A4. RESULTS: Two subtypes of fetal germ cells were detected by quantification and immunohistochemistry. Nearly all germ cells with morphological criteria of gonocytes and intermediate cells co-expressed OCT3/4, c-KIT, M2A and AP-2gamma. Starting from week 12, their number increased up to week 18/19 and then declined continuously during further development. After week 25, pre-spermatogonia were predominant and expressed MAGE-A4 selectively. CONCLUSIONS: Fetal male germ cells are comprised of two major groups with distinct immunohistochemical phenotypes. Germ cells that are predominantly found before week 25 of gestation co-express oncofetal proteins OCT3/4, c-KIT, M2A and AP-2gamma. After week 25, most germ cells have lost their pluripotent potential and acquire a spermatogonial phenotype defined by expression of MAGE-A4.