Deletion 6q in three cases of mixed-type liposarcoma in addition to t(12;16)(q13;p11)

Limited Role of TP53 and TP53-Related Genes in Myxoid Liposarcoma

Aims

Circumstantial evidence suggests that genetic changes may lead to tumor progression within the myxoid liposarcoma tumors (MLTs) carrying non-random chromosomal translocation t(12;16).

Methods

To address this subject an immunophenotypic analysis, applying antibodies against proteins encoded by TP53, MDM2 and CDK4 genes, complemented by molecular analysis of eight suitable cases, was performed on 104 consecutive cases. Chromosomal translocations were assessed either by cytogenetic analysis or by RT-PCR in 9 suitable cases and chimeric transcripts were found in all cases but two pleomorphic liposarcomas.

Results

Based on immunophenotyping and tumor site, the case material consisted of three groups. The first one was made up of 92 non-retroperitoneal cases carrying a null p53, mdm2, cdk4 immunophenotype, which remained unchanged over the time of recurrences and along the gamut of histologic subtypes. The second group was represented by five p53+, mdm2-, cdk4- non-retroperitoneal cases, 4 of which were further analysed by PCR-SSCP for p53 mutation. The im-munophenotipic profile of these cases, complemented by the molecular findings, supported a role of TP53 in tumor progression in three high-grade MLTs. The third group, consisting of 7 retroperitoneal cases, showed a heterogeneous immunophenotype, sharing immunophenotypic and molecular features with the well-differentiated/evoluted (dedifferentiated) liposarcoma group.

Conclusions

TP53 mutations seem to play a role in tumor progression in a few cases of MLTs (2.8%) showing more aggressive histologic characteristics. The unexpected finding that a number of retroperitoneal LMTs display the immunophenotypic profile of the well differentiated/evoluted (dedifferentiated) liposarcomas, deserves further investigation.

Molecular alterations of h-warts/LATS1 tumor suppressor in human soft tissue sarcoma

h-warts/LATS1 is a human homolog of the Drosophila warts tumor suppressor gene, which functions as a component of the mitotic apparatus. LATS1-deficient (Lats1(-/-)) mice have been reported to develop ovarian stromal tumors and soft tissue sarcomas. We investigated the status of the h-warts/LATS1 in 50 human soft tissue sarcomas to address its potential function as a tumor suppressor in human sarcoma development. In our RT-PCR assay, 7 (14%) (3 of 4 myxoid liposarcomas, 3 of 7 leiomyosarcomas, 1 of 9 malignant fibrous histiocytomas) of 50 sarcomas examined had no or a reduced expression of the h-warts/LATS1, indicating down-regulated gene expression. We further analyzed alterations of the h-warts/LATS1 in these seven sarcomas. Using microsatellite markers for chromosome 6q23-25.1, to which the h-warts/LATS1 is localized, an allelic loss of this locus was detected in one leiomyosarcoma, in which a missense point mutation of the h-warts/LATS1 was detected by PCR single-strand conformation polymorphism. Clusters of CpG dinucleotides in a 5' putative promoter region were hypermethylated in the other six sarcomas. Our data suggest that the molecular alterations of the h-warts/LATS1 could be of pathologic importance in human sarcomagenesis.

LiSa-2, a novel human liposarcoma cell line with a high capacity for terminal adipose differentiation

LiSa-2 is a stable cell line derived from a poorly differentiated, pleomorphic liposarcoma. In serum-containing medium, LiSa-2 cells are fibroblastoid and rapidly dividing. In a serum-free, chemically defined culture medium containing physiological concentrations of insulin, triiodothyronine and cortisol, LiSa-2 cells divide slower and, extensively storing fat, acquire adipocyte morphology. In contrast to fibroblastoid LiSa-2 cells, these adipocyte-like LiSa-2 cells highly express transcripts for peroxisome proliferator-activated receptor-gamma, lipoprotein lipase, fatty acid synthetase, hormone-sensitive lipase, adipocyte most abundant gene transcript-1, glycerol-3-phosphate-dehydrogenase and the insulin-sensitive glucose transporter-4, all of which are specific for differentiated adipocytes. However, leptin mRNA expression was demonstrated only after preventing DNA methylation by incorporation of 5-aza-deoxycytidine into cellular DNA. Functionally, adipocyte-like LiSa-2 cells show increased insulin-dependent glucose uptake and lipid synthesis and are sensitive to lipolytic agents. This cell line may serve as an in vitro model for studying the regulation of human liposarcoma differentiation and for screening drugs for induction of differentiation-associated growth arrest in liposarcomas.

Retroperitoneal liposarcoma with combined well-differentiated and myxoid malignant fibrous histiocytoma-like myxoid areas

To broaden the knowledge of myxoid morphology in liposarcoma, eight cases of unusual liposarcoma with combined well-differentiated and myxoid malignant fibrous histiocytoma (MFH)-like myxoid areas are reported. The tumors arose as huge retroperitoneal masses in elderly patients, except for one that occurred in the spermatic cord. Three cases had local recurrences, and one of the seven patients who were followed up had died of the tumor. Grossly, the tumors were mostly confluent and multinodular and showed a glistening myxoid appearance in variable proportions, which merged gradually into or were juxtaposed to yellow fatty or sclerotic whitish areas. Microscopically, in addition to areas of well-differentiated lipoma-like or sclerosing liposarcoma, all the tumors contained myxoid portions characterized by scattered multinucleated or bizarre giant cells and a prominent plexiform vascular pattern that resembled myxoid MFH or myxofibrosarcoma. The myxoid areas were associated with discernible lipogenesis. High-grade dedifferentiation was present in one tumor. Cytogenetically, in one case, the myxoid lesion had nonrandom chromosomal aberrations, such as ring and marker chromosomes, characteristic of a well-differentiated variant of liposarcoma. In a nested reverse transcription-polymerase chain reaction analysis using archival paraffin-embedded tissue, it was seen that none of the eight tumors with myxoid MFH-like features had TLS/FUS-CHOP fusion transcripts characteristic of myxoid and round cell liposarcomas. These clinicopathologic and molecular features suggest that the current myxoid tumors are more closely related to well-differentiated liposarcoma rather than to ordinary myxoid liposarcoma despite their unequivocal myxoid morphology. Missense point mutations of the p53 gene were detected in two (25%) cases by single-strand conformation polymorphism and sequence analyses. Immunohistochemical expressions of p53 and mdm2 were observed in 75% of the cases, in which immunoreactive tumor cells were seen more often in the myxoid MFH-like areas. Thus, altered p53 pathways, such as p53 gene mutation and mdm2-mediated inactivation of p53, may play a pathogenetic role in this form of tumor progression showing myxoid MFH-like morphology in liposarcoma, as has been suggested in dedifferentiated liposarcoma.

New diagnostic modalities in soft tissue sarcoma

Molecular and cytogenetic analysis of soft tissue sarcoma has provided a vast amount of new genetic information over the past 10 years. Recent advances in genetic technology, such as fluorescence in situ hybridization (FISH), reverse transcriptase-polymerase chain reaction (RT-PCR), and positional cloning techniques have greatly increased the rate of new discoveries and soon may bring cytogenetic and molecular analysis to standard pathology laboratories. Karotypic analysis of soft tissue tumors have demonstrated specific cytogenetic aberrations which have proved to be extremely useful diagnostically and have solidified and improved soft tissue tumor classification systems. Objective and reproducible prognostication in soft tissue sarcoma remains problematic. Presently, the grade and size of the sarcoma are the most important factors used to estimate risk of relapse and overall survival. Assigning a pathologic grade to an individual sarcoma as a means of predicting clinical behavior is often difficult with a 40% discordance rate even between expert sarcoma pathologists. There is mounting evidence that the composition of membrane phospholipid in tumor tissue is an important indicator of a tumor's cellularity, proliferative capacity, and differentiation state. However, there is a lack of information on the biochemical determinants of sarcoma proliferation and differentiation. To address these problems, novel quantitative ex vivo nuclear magnetic resonance (NMR) methods have been applied to determine the biochemical changes in tissue lipid for soft tissue sarcoma. The biochemical changes in tissue lipid have been found to correlate with sarcoma cellularity, growth rate, and differentiation. Continued prospective NMR analysis of tissue lipid biochemistry in soft tissue tumors will permit the development of a clinically relevant biochemical system of prognostic determinants for soft tissue sarcoma in the future.

[Multicentric liposarcoma. Apropos of a case]

INTRODUCTION

Though rare, observations of multiple liposarcomas show that the development of secondary tumors occur in sites usually considered as primary locations. This would be more frequent for myxoid liposarcomas than for other subtypes of the disease. Their origin, either multicentric (i.e., coexistence of several primary tumors) or due to metastatic spreading, is still debated.

EXEGESIS

We report a case of myxoid-type multicentric (i.e., right popliteal fossa, retroperitoneum and soft tissue of the left arm) liposarcomas of different sizes, without pulmonary, hepatic or osseous involvement. These liposarcomas were simultaneously diagnosed in a patient who presented with pain in the right knee.

CONCLUSION

This support the hypothesis that multiple liposarcomas have a multicentric origin. Initial and follow-up staging of such tumors must investigate not only usual metastatic sites but also classical primary locations.

Translocation (3;16)(q27;p11) in a patient with diffuse large B-cell lymphoma associated with the BCL-6 gene rearrangement

A patient with B-cell lineage diffuse large-cell lymphoma carrying the t(3;16)(q27;p11) and BCL-6 rearrangement is described. Cytogenetic studies showed 46,XY,t(3;16)(q27;p11.2)[.11]/46,idem,add(18)(q21)[7]/46,XY[2]. The chromosomal translocation involving the 3q27 locus was associated with the BCL-6 gene rearrangement identified by Southern blot analysis. This case involved systemic lymph nodes, as large as 3 cm in diameter, bilaterally in neck, axilla, and inguinal regions. The patient obtained complete remission with chemotherapy.

Gains and losses of DNA sequences in liposarcomas evaluated by comparative genomic hybridization

Comparative genomic hybridization (CGH) was used to detect and map the regions of gain, high-level amplification, and loss of DNA sequences in 14 liposarcomas. Thirteen tumors showed DNA sequence copy number changes of one or more genomic regions (mean, six aberrations/tumor; range, 0-17). These aberrations were observed in almost every chromosome but some chromosomal regions were affected more often than others. DNA sequence gains were more frequent than losses. The most common gain was seen at 12q14-21 (50% of tumors). Other frequent gains (29%) were of 1q21-24, 8cen-q21.2, 19q, and 20q. High-level amplification was observed in six (43%) tumors and included as minimal common segments bands 12q15, 1q22, and 1q24. In five (36%) tumors, sequences at 1q21-24 and 1q32 were found to be gained simultaneously with 12q14-21, which means that in 71% of the tumors with gain at 12q, an increase of DNA sequence copy number at 1q was also observed. The most common losses of DNA sequences (21%) occurred from regions 9p21-pter and 13q21-qter. Most of the aforementioned regions have not previously been reported to be altered in liposarcomas. The detection of a novel recurring amplicon at 1q21-24 with high-level amplification at 1q22 and frequent simultaneous DNA sequence gain at 12q14-21 (high-level amplification at 12q15) suggests that genes linked to both these regions may play a significant role in the development and progression of liposarcomas.