Uterine leiomyomas, or fibroids, are benign tumors that affect millions of women worldwide and that can cause considerable morbidity. To study the genetic basis of this tumor type, we examined 18 uterine leiomyomas derived from 17 different patients by exome sequencing and identified tumor-specific mutations in the mediator complex subunit 12 (MED12) gene in 10. Through analysis of 207 additional tumors, we determined that MED12 is altered in 70% (159 of 225) of tumors from a total of 80 patients. The Mediator complex is a 26-subunit transcriptional regulator that bridges DNA regulatory sequences to the RNA polymerase II initiation complex. All mutations resided in exon 2, suggesting that aberrant function of this region of MED12 contributes to tumorigenesis.

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a tumor predisposition syndrome caused by heterozygous germline mutations in the fumarate hydratase (FH) gene. Cutaneous and uterine leiomyomas are the most common clinical manifestations of HLRCC, whereas only approximately 20% of the families display renal cell cancer (RCC). The number of RCC cases in these families varies from one to five. Interestingly, families with multiple RCC cases are mainly found in Finland and the USA. Such aggregation of RCC in only some families and populations has led to the hypothesis that besides FH mutations also other inherited genetic and/or environmental factors may contribute to the malignant kidney tumor formation. To search for such a genetic modifier we have performed a genome-wide linkage analysis in two and an identical by descent analysis in four Finnish HLRCC families with several RCC patients. Additional Finnish and French families were used in fine-mapping and haplotype analyses. The only region compatible with linkage was the locus surrounding the FH gene itself in chromosome 1q43. The genes in the putative candidate region were screened, but no potentially pathogenic alterations were observed. Although these data do not rule out the existence of a genetic modifier, they emphasize the contribution of the FH genotype in HLRCC related RCC. Therefore, as all FH mutation carriers may have an increased risk for developing renal cancer, counseling and genetic testing should be offered for all HLRCC family members and clinical follow-up should be organized for the mutation carriers.

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a tumor predisposition syndrome with cutaneous and uterine leiomyomatosis as well as renal cell cancer (RCC) as its clinical manifestations. HLRCC is caused by heterozygous germline mutations in the fumarate hydratase (fumarase) gene. In this study, we used array comparative genomic hybridization to identify the specific copy number changes characterizing the HLRCC-associated RCCs. The study material comprised formalin-fixed paraffin-embedded renal tumors obtained from Finnish patients with HLRCC. All 11 investigated tumors displayed the papillary type 2 histopathology typical for HLRCC renal tumors. The most frequent copy number changes detected in at least 3/11 (27%) of the tumors were gains in chromosomes 2, 7, and 17, and losses in 13q12.3-q21.1, 14, 18, and X. These findings provide genetic evidence for a distinct copy number profile in HLRCC renal tumors compared with sporadic RCC tumors of the same histopathological subtype, and delineate chromosomal regions that associate with this very aggressive form of RCC.

Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a hereditary tumor predisposition syndrome with fumarate hydratase (FH), which encodes a tricarboxylic acid cycle enzyme fumarase, as the predisposing gene. The HLRCC family members carry heterozygous germline mutations of the FH gene and the tumors often harbor a second hit making the growth fumarase deficient. The phenotype includes benign cutaneous and uterine leiomyomas as well as renal cell cancer (RCC). The HLRCC related RCCs usually belong to histological papillary type II subtype and are solitary, unilateral and aggressive. The benign leiomyomas are the most common manifestation of the syndrome affecting almost all FH mutation carriers whereas the renal cell cancer phenotype affects only about 20% of the HLRCC families. Interestingly, majority of the families with multiple renal cell cancer cases have concentrated in Finland and the U.S. Why the malignant phenotype affects only a part of the HLRCC patients is unknown. There is no genotype-phenotype correlation and type or site of the FH mutation does not affect the phenotype. The fumarase enzyme activity levels do not correlate with the phenotype either. Thus it is possible that the appearance of RCC requires, in addition to FH mutation, another genetic factor. To search for such a factor in four Finnish HLRCC families with multiple RCC cases we performed genome wide linkage and/or identical by descent (IBD) analyses. After finemapping procedures the only region compatible with linkage was the FH locus itself in 1q43. The genes of the region were screened but no pathognomonic mutations were found. Although these results do not exclude the existence of a genetic RCC risk modifier in HLRCC, the role of FH mutations behind RCC tumors is emphasized. Counseling and genetic testing should be available for HLRCC family members and the FH mutation carriers should be carefully followed up to enable early detection and treatment of the aggressive cancers. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1844.