bims-myxlip Biomed News
on Myxoid liposarcoma
Issue of 2021‒06‒27
two papers selected by
Laura Mannarino
Humanitas Research

  1. Hum Cell. 2021 Jun 23.
      Spindle cell/sclerosing rhabdomyosarcoma (ssRMS) is a rare subtype of rhabdomyosarcoma (RMS) that has fascicular spindle cell and/or sclerosing morphology. SsRMS has a diverse molecular background and is categorized into three groups: congenital/infantile ssRMS with a gene fusion involving the NCOA2 and VGLL2, ssRMS with the MYOD1 mutation, and ssRMS with no recurrent identifiable genetic alterations. Because ssRMS is a newly defined disease concept of RMS, the optimal treatment methods have not been determined. This results in unfavorable prognosis and consequently signals the urgent need for continuous research. Patient-derived cell lines are essential tools in basic and translational research. However, only two ssRMS cell lines with the MYOD1 mutation have been reported to date. Thus, we established a novel ssRMS cell line named NCC-ssRMS2-C1 using a surgically resected tumor tissue from an adult ssRMS patient. NCC-ssRMS2-C1 cells retained the copy number alterations corresponding to the original tumor and are categorized into the group with no recurrent identifiable genetic alterations. NCC-ssRMS2-C1 cells demonstrated constant proliferation, spheroid formation, and capability for invasion in vitro, reflecting the malignant features of the original tumor tissue. In a drug screening test, ssRMS demonstrated remarkable sensitivity to romidepsin, trabectedin, actinomycin D, and bortezomib. Hence, we conclude that the NCC-ssRMS2-C1 cell line is the first ssRMS cell line which belongs to the group with no recurrent identifiable genetic alterations, and it will be a useful resource in both basic and translational studies for ssRMS.
    Keywords:  Patient-derived cancer model; Patient-derived cell line; Sarcoma; Spindle cell/sclerosing rhabdomyosarcoma
  2. Mod Pathol. 2021 Jun 24.
      Myxoid pleomorphic liposarcoma is a recently defined subtype of liposarcoma, which preferentially involves the mediastinum of young patients and shows mixed histological features of conventional myxoid liposarcoma and pleomorphic liposarcoma. While myxoid pleomorphic liposarcoma is known to lack the EWSR1/FUS-DDIT3 fusions characteristic of the former, additional genetic data are limited. To further understand this tumor type, we extensively examined a series of myxoid pleomorphic liposarcomas by fluorescence in situ hybridization (FISH), shallow whole genome sequencing (sWGS) and genome-wide DNA methylation profiling. The 12 tumors occurred in 6 females and 6 males, ranging from 17 to 58 years of age (mean 33 years, median 35 years), and were located in the mediastinum (n = 5), back, neck, cheek and leg, including thigh. Histologically, all cases consisted of relatively, bland, abundantly myxoid areas with a prominent capillary vasculature, admixed with much more cellular and less myxoid foci containing markedly pleomorphic spindled cells, numerous pleomorphic lipoblasts and elevated mitotic activity. Using sWGS, myxoid pleomorphic liposarcomas were found to have complex chromosomal alterations, including recurrent large chromosomal gains involving chromosomes 1, 6-8, 18-21 and losses involving chromosomes 13, 16 and 17. Losses in chromosome 13, in particular loss in 13q14 (including RB1, RCTB2, DLEU1, and ITM2B genes), were observed in 4 out of 8 cases analyzed. Additional FISH analyses confirmed the presence of a monoallelic RB1 deletion in 8/12 cases. Moreover, nuclear Rb expression was deficient in all studied cases. None showed DDIT3 gene rearrangement or MDM2 gene amplification. Using genome-wide DNA methylation profiling, myxoid pleomorphic liposarcomas and conventional pleomorphic liposarcomas formed a common methylation cluster, which segregated from conventional myxoid liposarcomas. While the morphologic, genetic and epigenetic characteristics of myxoid pleomorphic liposarcoma suggest a link with conventional pleomorphic liposarcoma, its distinctive clinical features support continued separate classification for the time being.