D. Olde Weghuis

Comparative genomic hybridization of germ cell tumors of the adult testis: Confirmation of karyotypic findings and identification of a 12p- amplicon

Comparative genomic hybridization (CGH) was carried out on 15 primary testicular germ cell tumors (TGCT) of adolescents and adults and two metastatic residual tumors after chemotherapeutic treatment. The results were compared with karyotypic data obtained form the same tumor specimens after direct harvesting of metaphases or short-term in vitro culture. Both techniques revealed that the most consistent abnormality in primary TGCT is gain of 12p-sequences. Although in most cases over-representation of the complete short arm was observed, CGH revealed a specific amplification of 12p11.1-p12.1 region in two independent primary tumors. In addition, loss of (parts of) chromosome 13 (always involving q31-qter), and gain of (parts of) chromosome 7 (mostly involving q11), (parts of) chromosome 8, and the X chromosome were detected in more than 25% of the tumors by this latter technique. Loss of 6q15-q21 in both residual tumors analyzed may suggest a role for this anomaly in acquired resistance to chemotherapeutic treatment. Overall, the CGH analyses confirmed gains and losses of certain chromosomal regions in TGCT as observed by karyotyping, and thus support their role in the development of these neoplasms. The amplification of a restricted region of 12p in primary TGCT confirms and extends our previous observations and, as such, represents an important step forward in the identification of gene(s) on 12p relevant for the pathogenesis of these tumors.

Distinct Xp11.2 breakpoint regions in synovial sarcoma revealed by metaphase and interphase FISH: relationship to histologic subtypes.

Fluorescence in situ hybridization (FISH) and molecular analyses of synovial sarcomas with cytogenetically similar (X;18)(p11.2;q11.2) translocations have revealed two alternative breakpoint regions in Xp11.2, one residing in the ornithine aminotransferase-like 1 (OATL1) region and the other one in the related but distinct OATL2 region. As these results were obtained by different groups, we set out to evaluate an extended series of tumors with special emphasis on the two possible X-related breakpoint regions. Together, seven synovial sarcomas were identified with a break in the OATL1 region and six with a break near OATL2, thereby confirming the actual existence of the two alternative Xp breakpoint regions. We speculate that there seems to be a relationship between the occurrence of these breakpoint regions and the histologic phenotype of the tumors, with a predominance of OATL1-related breakpoints in the classical biphasic tumors and of OATL2-related breakpoints in the monophasic fibrous tumors.

Towards the isolation of a human malignant extragonadal germ cell tumour-associated breakpoint in chromosome 11q13.

In a previous study we have defined a subgroup of human malignant extragonadal germ cell tumours that is characterized by complex translocations involving chromosomes 6 and 11 (Echten et al. 1995). Here we report (i) the use of fluorescent in situ hybridization, pulsed field gel electrophoresis and direct visual hybridization techniques to localize the tumour‐associated breakpoint within band 11q13, and (ii) the construction of a phage library enriched for this region to facilitate genomic walks towards the breakpoint. Extensive breakpoint‐flanking contigs were generated and within these contigs six candidate genes could be identified.