Differential positioning and close spatial proximity of translocation-prone genes in nonmalignant B-cells from multiple myeloma patients

Cytogenomic Profile of Uterine Leiomyoma: In Vivo vs. In Vitro Comparison

We performed a comparative cytogenomic analysis of cultured and uncultured uterine leiomyoma (UL) samples. The experimental approach included karyotyping, aCGH, verification of the detected chromosomal abnormalities by metaphase and interphase FISH, MED12 mutation analysis and telomere measurement by Q-FISH. An abnormal karyotype was detected in 12 out of 32 cultured UL samples. In five karyotypically abnormal ULs, MED12 mutations were found. The chromosomal abnormalities in ULs were present mostly by complex rearrangements, including chromothripsis. In both karyotypically normal and abnormal ULs, telomeres were ~40% shorter than in the corresponding myometrium, being possibly prerequisite to chromosomal rearrangements. The uncultured samples of six karyotypically abnormal ULs were checked for the detected chromosomal abnormalities through interphase FISH with individually designed DNA probe sets. All chromosomal abnormalities detected in cultured ULs were found in corresponding uncultured samples. In all tumors, clonal spectra were present by the karyotypically abnormal cell clone/clones which coexisted with karyotypically normal ones, suggesting that chromosomal abnormalities acted as drivers, rather than triggers, of the neoplastic process. In vitro propagation did not cause any changes in the spectrum of the cell clones, but altered their ratio compared to uncultured sample. The alterations were unique for every UL. Compared to its uncultured counterpart, the frequency of chromosomally abnormal cells in the cultured sample was higher in some ULs and lower in others. To summarize, ULs are characterized by both inter- and intratumor genetic heterogeneity. Regardless of its MED12 status, a tumor may be comprised of clones with and without chromosomal abnormalities. In contrast to the clonal spectrum, which is unique and constant for each UL, the clonal frequency demonstrates up or down shifts under in vitro conditions, most probably determined by the unequal ability of cells with different genetic aberrations to exist outside the body.

FGFR3 preferentially colocalizes with IGH in the interphase nucleus of multiple myeloma patient B-cells when FGFR3 is located outside of CT4

Many B-cell malignancies are characterized by chromosomal translocations involving IGH and a proto-oncogene. For translocations to occur, spatial proximity of translocation-prone genes is necessary. Currently, it is not known how such genes are brought into proximity with one another. Although decondensed chromosomes occupy definitive, non-random spaces in the interphase nucleus known as chromosome territories (CTs), chromatin at the edges of CTs can intermingle, and specific genomic regions from some chromosomes have been shown to "loop out" of their respective CTs. This extra-territorial positioning of specific genomic regions may provide a mechanism whereby translocation-prone genes are brought together in the interphase nucleus. FGFR3 and MAF recurrently participate in translocations with IGH at different frequencies. Using 3D, 4-color FISH, and 3D analysis software, we show frequent extra-territorial positioning of FGFR3 and significantly less frequent extra-territorial positioning of MAF. Frequent extra-territorial positioning may be characteristic of FGFR3 in B-cells from healthy adult donors and non-malignant B-cells from patients, but not in hematopoietic stem cells from patients with translocations. The frequency of extra-territorial positioning of FGFR3 and MAF in B-cells correlates with the frequency of translocations in the patient population. Most importantly, in patient B-cells, we demonstrate a significant proportion of extra-territorial FGFR3 participating in close loci pairs and/or colocalizing with IGH. This preliminary work suggests that in patient B-cells, extra-territorial positioning of FGFR3 may provide a mechanism for forming close loci pairs and/or colocalization with IGH; indirectly facilitating translocation events involving these two genes. © 2016 Wiley Periodicals, Inc.

MiRNome expression is deregulated in the peripheral lymphoid compartment of multiple myeloma

MicroRNAs (miRNAs) are short non-coding RNAs involved in the regulation of gene expression. Selected groups of miRNAs are differentially expressed in various types of cancers. Alterations in miRNAs gene expression have been shown in cells from the B-cell malignancy, multiple myeloma (MM). However, although MM is a disease of plasma cells, abnormalities have been detected in the peripheral blood of the patients. The goal of our study was to analyse the entire miRNome in peripheral lymphocytes of MM patients using reverse transcription quantitative polymerase chain reaction. Using in silica analysis, we also evaluated some of the most interesting and significant pathways. Analysis revealed that MM samples had a distinct miRNA profile compared to the controls. This resulted in the identification of 203 miRNAs, 85 of which were over-expressed and 118 under-expressed. Of these, 184 possessed validated or highly predicted mRNA targets. We identified 12 354 mRNA targets of the transcriptome: 36·4% of the related proteins are involved in death processes while the 21% are required for growth and cell proliferation. We have demonstrated that miRNAs are differentially expressed in the peripheral blood of MM patients compared to controls, affecting some pathways involved in the anti-apoptotic process, cell proliferation and maybe anti-angiogenesis.

Differential nuclear organization of translocation-prone genes in nonmalignant B cells from patients with t(14;16) as compared with t(4;14) or t(11;14) myeloma

Gene organization in nonmalignant B cells from t(4;14) and t(11;14) multiple myeloma (MM) patients differs from that of healthy donors. Among recurrent IGH translocations in MM, the frequency of t(4;14) (IGH and FGFR3) or t(11;14) (IGH and CCND1) is greater than the frequency of t(14;16) (IGH and MAF). Gene organization in t(14;16) patients may influence translocation potential of MAF with IGH. In patients, three-dimensional FISH revealed the positions of IGH, CCND1, FGFR3, and MAF in nonmalignant B cells that are likely similar to those when MM first arose, compared with B cells from healthy donors. Overall, IGH occupies a more central nuclear position while MAF is more peripherally located. However, for B cells from t(4;14) and t(11;14) patients, IGH and FGFR3, or IGH and CCND1 are found in spatial proximity: IGH and MAF are not. This differs in B cells from t(14;16) patients and healthy donors where IGH is approximately equidistant to FGFR3, CCND1, and MAF, suggesting that gene organization in t(14;16) patients is different from that in t(4;14) or t(11;14) patients. Translocations between IGH and MAF may arise only in the absence of close proximity to the more frequent partners, as appears to be the case for individuals who develop t(14;16) MM.