Rearrangement of the transcription factor gene CHOP in myxoid liposarcomas with t(12;16)(q13;p11).

Most myxoid liposarcomas (MLS) are characterized cytogenetically by a t(12;16)(q13;p11). It is reasonable to assume that this translocation corresponds to the consistent rearrangement of one or two genes in 12q13 and/or 16p11, and that the loci thus affected are important in the normal control of fat cell differentiation and proliferation. We have used Southern blot technique to test whether a gene of the CCAAT/enhancer binding protein (C/EBP) family, CHOP, which maps to 12q13 and is assumed to be involved in adipocyte differentiation, could be the 12q gene in question. Using a cDNA probe that spans the CHOP coding region, we detected one rearranged and one wild type allele in nine of nine MLS with t(12;16). Using PCR generated, site-specific probes corresponding to the non-coding exons 1 and 2 and intron 2 of CHOP, rearrangements in five of seven tumors mapped to the 2.4 and 1.6 kbp PstI fragments that contain the first two exons and introns of the gene and the upstream promoter region. In contrast to the findings in MLS, no tumor without a t(12;16) exhibited aberrant CHOP restriction digest patterns. These tumors included one highly differentiated liposarcoma with abnormal karyotype but no involvement of 12q13, seven lipomas with various cytogenetic aberrations of 12q13-15, two uterine leiomyomas with t(12;14) (q14-15;q23-24), and one hemangiopericytoma and one chondroma, both of which also had 12q13 changes.(ABSTRACT TRUNCATED AT 250 WORDS)     

inv(12)(p11.2q13) in an endometrial polyp

A benign endometrial polyp from a 50-year-old postmenopausal woman has been cytogenetically investigated. A single clonal karyotypic anomaly, inv(12)(p11.2q13), was found in about 30% of cells analyzed after short-term culture. This finding contributes further to the hypothesis that the chromosomal segment 12q13-q14, which is also involved in chromosomal rearrangements in uterine leiomyomas, pleomorphic adenomas of the salivary glands, lipomas, and myxoid liposarcomas, contains a gene or genes that are related to cellular proliferation rather than to malignant transformation.     

Breakpoints in benign lipoma may be at 12q13 or 12q14

Chromosomal investigations in two unrelated lipoma samples are reported. The breakpoint involving 12q in chromosomal rearrangements could be assigned to band 12q13 in one case and 12q14 in the other case. Evidence is provided that cytogenetically distinct breakpoints on 12q may be found in lipoma cells, resolving previous disagreements based on interpretational difficulties.     

Consistent involvement of band 12q14 in two different translocations in three lipomas from the same patient

We studied cytogenetically three distinct lipomas from a patient with multiple subcutaneous lipomas in the left shoulder area. A breakpoint at 12q14 was involved in structural rearrangements in the three lipomas resulting in two different reciprocal translocations, i.e., t(3;12)(q28;q14) in two and a t(1;12)(q34.2;q14) in the third. These results confirm the consistency of involvement of the breakpoint at 12q14 in lipomas and give support to the hypothesis that multiple lipomas evolve from different stem cells.     

Localization of the chromosomal breakpoints of the t(12;16) in liposarcoma to subbands 12q13.3 and 16p11.2

Short-term cultures of two myxoid liposarcomas and two mixed-type (myxoid and round cell) liposarcomas were cytogenetically analyzed. A t(12;16)(q13;p11) was present in three tumors, whereas the fourth had an unbalanced 12;16-translocation with breaks in 12q13 and 12q22, with loss of the 12q13-q22 segment, and in 16p11. In the two mixed liposarcomas, the breakpoints could be determined at subband level to 12q13.3 and 16p11.2.     

Uterine leiomyoma cytogenetics

Uterine leiomyoma--a benign smooth muscle tumor--has recently been found to contain tumor-specific chromosome aberrations. Although only normal karyotypes were detected in 50 to 80% of cytogenetically investigated tumors, 104 leiomyomas with karyotypic aberrations have already been reported. At least four cytogenetically abnormal subgroups have been identified thus far, characterized by rearrangements of 6p, del(7)(q21.2q31.2), +12, and t(12;14)(q14-15;q23-24). The remaining abnormal tumors have had various nonrecurrent anomalies. Secondary karyotypic rearrangements, sometimes including ring chromosomes, have been found in one-third and reflect clonal evolution. Occasional leiomyomas have contained multiple numerical and structural rearrangements. Though benign, these cytogenetically grossly aberrant tumors often displayed more atypical histological features than are usually seen in leiomyoma. Multiple leiomyomas have been investigated from 69 patients, with detection of chromosome anomalies in at least two separate tumors from the same uterus in ten cases. In half of these patients unrelated aberrations were found in different leiomyomas from the same uterus. On other occasions the aberrations were identical, indicating that although some uterine leiomyomas originate independently, others may develop by intra-myometrial spreading from a common neoplastic clone. Some common features are discernible between the karyotypic pictures of uterine leiomyoma and angioleiomyoma; rearrangements of 6p, 13q, and 21q have been described in both tumor types. The cytogenetic similarities so far detected between leiomyoma and the malignant muscle tumors--leiomyosarcoma and rhabdomyosarcoma--are few and may be fortuitous. The cytogenetic profiles of leiomyoma and lipoma are strikingly similar; both tumor types have nonrandom rearrangements of 12q13-15, t(12;14) in leiomyoma and t(3;12) in lipoma, as well as variant rearrangements of the same 12q segment. Both also have cytogenetic subgroups characterized by changes in 6p and ring chromosomes. Finally, karyotypic similarities exists also between leiomyoma and pleomorphic adenoma of the salivary gland, which includes a subset of tumors with anomalies of 12q13-15, and with myxoid liposarcoma, which has t(12;16)(q13;p11) as a tumor-specific rearrangement.     

Consistent breakpoints in region 14q22-q24 in uterine leiomyoma

The chromosomes of nine consecutive human benign leiomyomas of the uterus were studied with banding methods following short-term culture. All of the tumors had a typical benign histology. Five exhibited clonal chromosome changes including three with consistent involvement of chromosomes 12 and 14 in a translocation, t(12;14)(q14-15;q23-q24), a direct insertion, dir ins(12;14)(p11.2;q22q24.1), and a direct insertion, dir ins(14;12)(q22-q23;q14-q15q23-q24.1). Thus, this study demonstrated the presence of consistent chromosome changes in another benign proliferation. Strikingly, the breakpoint observed at 12q14-q15 in two specimens is also involved nonrandomly in other benign proliferations such as mixed salivary gland tumors and lipomas. However, region 14q22-q24, which was involved in three specimens, may contain a DNA sequence critical for the genesis of uterine leiomyoma.     

Ring formation and structural rearrangements of chromosome 1 as secondary changes in uterine leiomyomas with t(12;14)(q14-15;q23-24)

Cytogenetic analysis of short-term cultures from two uterine leiomyomas revealed, in addition to the primary abnormality, the reciprocal translocation t(12;14)(q14-15;q23-24), secondary structural changes that in both cases included ring chromosomes and rearrangements of chromosome 1. One tumor had the karyotype 46,XX,r(1)(p34q32),ins(8;9)(q13;q13q22),t(12;14)(q14-15;q23- 24). Massive numerical rearrangements were found in the second leiomyoma, with chromosome numbers ranging from 47 to 92. In spite of this variability, two main cell populations could be discerned, one near-diploid, the other hypotetraploid, with most mitoses having chromosome numbers between 80 and 88. These findings were corroborated by flow cytometry, which revealed two peaks corresponding to DNA indexes of 0.97 and 1.77. The structural abnormalities t(1;1)(p31;q44) and t(12;14)(q14-15;q23-24) were present in all karyotypically abnormal cells, and one or more unidentified ring chromosomes were observed in most of the hypotetraploid mitoses. In no cells were double copies of the t(1;1) and t(12;14) rearrangements detected. The similarity between the secondary changes in the cases reported here suggests that clonal evolution in uterine leiomyoma is nonrandom.     

Complex chromosome rearrangements involving 12q14 in two uterine leiomyomas

Cytogenetic analysis of short-term cultures from 10 uterine leiomyomas revealed normal karyotypes in 8 and clonal complex chromosome rearrangements in 2 tumors. In both leiomyomas with clonal abnormalities, 12q14, but not 14q22-24, was involved in translocations with 1q43 in one tumor and with 12q24 in the other. Additional chromosome abnormalities were found in both cases: 1-5 rings and monosomy of chromosome 9 in case 1, and complex numerical and structural abnormalities of chromosomes 1, 6-8, 11, 13, 16, 17, and 22 in case 2. The consistent cytogenetic rearrangement of 12q14 in uterine leiomyomas, sometimes without concomitant 14q changes, indicates that a gene of critical importance for leiomyoma development may be found in this band.     

Cytogenetic studies of adipose tissue tumors. II. Recurrent reciprocal translocation t(12;16)(q13;p11) in myxoid liposarcomas

Detailed chromosome studies, briefly reported previously, from short-term cultures of tumor cells from myxoid liposarcomas are reported. A common reciprocal translocation, t(12;16)(q13;p11), was found in three cases and a complex t(1;12;16)(p11;q13;p11) in the fourth one. This nonrandom primary change, not described before in solid tumors, could characterize the myxoid form of liposarcoma. The involvement of a closely located breakpoint on chromosome #12 in a reciprocal t(3;12)(q28;q14) described in a lipoma in the previous article of this series, suggests a common basis in the biological process of proliferation of tumors sharing a common histogenesis.     

No amplification or rearrangement of INT1, GLI, or COL2A1 in uterine leiomyomas with t(12;14)(q14-15;q23-24)

We have studied three uterine leiomyoma tumors, all previously cytogenetically analyzed and shown to have the clonal abnormality t(12:14)(q14-15;q23-24), with the purpose of detecting amplification or rearrangement of three genes that are localized close to the 12q breakpoint region. The genes studied were the two putative oncogenes INT1 and GLI, and the collagen type II alpha 1 gene, COL2A1. No rearrangement or amplification could be detected for any of the three gene sequences.     

Cytogenetic and histologic findings in 17 pulmonary chondroid hamartomas: Evidence for a pathogenetic relationship with lipomas and leiomyomas

Pulmonary chondroid hamartomas (PCH) are benign tumors that contain mesenchymal and epithelial components. In this series, we identified clonal chromosome aberrations in mesenchymal cells from 10 of 17 PCH. Chromosome band 12q15 was rearranged most frequently (N = 4), and one case had a t(12;14)(q15;q24) that was identical cytogenetically to the characteristic translocation in uterine leiomyomas. Histologic review revealed diverse mesenchymal populations, including undifferentiated cells, cartilage, adipose tissue, and smooth muscle, in most of the PCH. These findings suggest that PCH result from neoplastic transformation of a primitive mesenchymal cell that differentiates along chondroid, adipose, and smooth muscle pathways.     

Cytogenic and molecular analysis of an aggressive angiomyxoma.

Aggressive angiomyxoma is a rare mesenchymal tumor occurring mainly in the vulvar region extending into the paravaginal and perirectal region. Histologically, this tumor is rich in vascular structures and in collagen fibers and is of myxoid appearance. Cytogenetic and molecular analysis was performed on a case of an aggressive angiomyxoma and revealed clonal karyotypic abnormalities. All 50 metaphases analyzed showed a translocation involving the chromosomal region 12q14-15. Chromosomal aberrations involving the breakpoint region 12q14-15 are frequently seen in a variety of other mesenchymal tumors as uterine leiomyomas, lipomas, hamartomas of the lung, liposarcomas, or hemangiopericytomas. Therefore, this breakpoint region seems to be the most frequent chromosomal abnormality associated with the initiation of human mesenchymal neoplasms. To narrow down the breakpoint region on a molecular level in the cells of the angiomyxoma we performed FISH analysis with different cosmid clones originating from a yeast artificial chromosome and cosmid contig overspanning parts of the region 12q14-15. We were able to narrow down the region to approximately 70-80 kb belonging to an area designated a multiple aberration region, because it also includes the breakpoints of leiomyomas, lipomas, and pleomorphic adenomas with 12q13-15 abnormalities. Our molecular and cytogenic data suggest that angiomyxomas or at least a subset of them molecularly belong to the benign group of mesenchymal tumors showing multiple aberration region involvement.     

Normal blood lymphocytes from patients with adipose tissue tumors with rearrangements at 12q13-q14 do not express the fragile site fra(12)(q13.1)

An association between chromosomal fragile sites and cancer-specific breakpoints has been found to be statistically significant. Cancer patients have been shown to be carriers of fragile sites in chromosome regions involved in rearrangements in malignant cells. Based on these observations it has been hypothesized that fragile sites may be involved in the pathogenesis of human tumors. We have recently described a new recurrent cancer breakpoint at chromosomal region 12q13-q14 in adipose tissue tumors. The possible involvement in these tumors of the rare folate-sensitive fragile site 12q13.1 has been investigated in PHA-stimulated peripheral blood cells from three patients carrying the t(12;16)(q13;p11) in their liposarcoma cells and one patient with the t(3;12)(q28;q14) in his lipoma cells. No expression of the fragile site 12q13.1 could be detected in the blood lymphocytes of any of the patients. The involvement of the fragile site 12q13.1 in the pathogenesis of adipose tissue tumors with a 12q13-q14 breakpoint remains to be established.     

Clonal chromosome abnormalities in two liposarcomas

Two liposarcomas were analyzed with chromosome banding technique. The sole chromosomal abnormality in one of the tumors, a mixed type (myxoid and round cell) liposarcoma, was t(12;16)(q13;p11), a rearrangement previously reported to be associated with myxoid liposarcoma. The other tumor, a pleomorphic liposarcoma, displayed massive numerical rearrangements (modal chromosome number 94-112), and numerous, mostly unidentifiable, marker chromosomes. The following clonal structural aberrations were recognized: del(1)(p22), del(1)(q23), t(7;?)(p22;?), i(17q), and t(19;?)(q13;?).     

Cytogenetic studies of adipose tissue tumors. I. A benign lipoma with reciprocal translocation t(3;12)(q28;q14)

Detailed clinical histories and cytogenetic investigations using short-term cultures are reported in three typical benign lipomas. Although a diploid (normal) karyotype was observed in two cases, a reciprocal chromosome translocation t(3;12)(q28;q14) was found in the third case, which was briefly reported previously. These data are discussed in light of a lipoma with similar karyotypic changes reported by Heim et al. and a similar translocation observed by us in malignant myxoid liposarcomas. The nonrandom involvement of segment 12q13-q14 in benign and malignant lipomatous tumors suggest a common basis for at least one of the possible multiple steps in the genesis of neoplastic processes.     

A case of lipoblastoma with t(3;8)(q12;q11.2).

We studied a single case of lipoblastoma in a 4-year-old boy. Cytogenetic analysis of the tumor cells showed two abnormal clones: 47,XY,t(3;8)(q12;q11.2),+mar, and 46,XY,t(3;8)(q12;q11.2). To our knowledge, this is the second report of chromosome findings in this rare tumor. Although lipoblastomas are frequently confused with myxoid liposarcomas, breakpoints in our patient were different from those of myxoid liposarcoma.     

Recurrent rearrangements in the proximal 15q11-q14 region: a new breakpoint cluster specific to unbalanced translocations

Unbalanced translocations, that involve the proximal chromosome 15 long arm and the telomeric region of a partner chromosome, result in a karyotype of 45 chromosomes with monosomy of the proximal 15q imprinted region. Here, we present our analysis of eight such unbalanced translocations that, depending on the parental origin of the rearranged chromosome, were associated with either Prader-Willi or Angelman syndrome. First, using FISH with specific BAC clones, we characterized the chromosome 15 breakpoint of each translocation and demonstrate that four of them are clustered in a small 460 kb interval located in the proximal 15q14 band. Second, analyzing the sequence of this region, we demonstrate the proximity of a low-copy repeat 15 (LCR15)-duplicon element that is known to facilitate recombination events at meiosis and to promote rearrangements. The presence, in this region, of both a cluster of translocation breakpoints and a LCR15-duplicon element defines a new breakpoint cluster (BP6), which, to our knowledge, is the most distal breakpoint cluster described in proximal 15q. Third, we demonstrate that the breakpoints for other rearrangements including large inv dup (15) chromosomes do not map to BP6, suggesting that it is specific to translocations. Finally, the translocation breakpoints located within BP6 result in very large proximal 15q deletions providing new informative genotype-phenotype correlations.