Biomedical subjects

Shamini Selvarajah

Publications and source records attributed to Shamini Selvarajah.

6 recordsLinked to original sources

PubMed2026

Clinicopathologic Spectrum and Intraprostatic Heterogeneity of Primary Mismatch Repair-Deficient Prostate Cancer.

Mismatch repair deficiency (MMRd) is identified in a small subset of prostate cancers and has implications for therapy selection and germline testing. The clinicopathologic spectrum of primary MMRd prostate cancer remains incompletely characterized. We evaluated 32 primary treatment-naive MMRd prostatic adenocarcinomas identified at a single institution. Grade group distribution included GG5 (n=12, 38%), GG4 (n=4, 13%), GG3 (n=7, 22%), and GG2 (n=9, 28%). Intraductal and/or invasive cribriform carcinoma was identified in 78% of cases overall and in 78% of GG2 tumors. MMR protein loss predominantly involved MSH2/MSH6 (78%), with isolated MSH6 loss in 16% and MLH1/PMS2 loss in 6%. Concordant pathogenic MMR gene alterations were identified on targeted NGS in all cases, while concurrent Tier 1/2 HRR gene alterations were present in 11 cases (35%), including ATM, BRCA1, and BRCA2. Germline testing performed in 15 cases identified Lynch syndrome in 5 (33%). MMR immunohistochemistry performed on multiple tissue blocks in 14 cases revealed discordant MMR status between tumor foci in 8 cases (57%), with MMR deficiency consistently restricted to the highest-grade focus and retained expression in spatially separate lower-grade foci. One additional case demonstrated apparent intratumoral heterogeneity within a single biopsy core, with MMR deficiency restricted to a higher-grade component and retained expression in the adjacent lower-grade tumor. These findings demonstrate a broader clinicopathologic spectrum of primary MMRd prostate cancer than previously recognized. Frequent discordance of MMR status between tumor foci highlights the importance of evaluating the highest-grade tumor focus when assessing multifocal primary prostate cancer.

cribriform↗

PubMed2006

Genomic mechanisms and measurement of structural and numerical instability in cancer cells.

The progression to cancer is often associated with instability and the acquisition of genomic heterogeneity, generating both clonal and non-clonal populations. Chromosomal instability (CIN) describes the excessive rate of numerical and structural genomic change in tumors. Mitotic segregation errors strongly influences copy number, while structural aberrations can occur at unstable genomic regions, or through aberrant DNA repair or methylation. Combined molecular cytogenetic analyses can evaluate cell-to-cell variation, and define the complexity of numerical and structural alterations. Because structural change may occur independently of numerical alteration, we propose the term structural chromosomal instability [(S)-CIN] to distinguish numerical from structural CIN.

Alu Elements↗

PubMed2006

The breakage-fusion-bridge (BFB) cycle as a mechanism for generating genetic heterogeneity in osteosarcoma.

Osteosarcoma (OS) is characterized by chromosomal instability and high copy number gene amplification. The breakage-fusion-bridge (BFB) cycle is a well-established mechanism of genome instability in tumors and in vitro models used to study the origins of complex chromosomal rearrangements and cancer genome amplification. To determine whether the BFB cycle could be increasing the de novo rate of formation of cytogenetic aberrations in OS, the frequency of anaphase bridge configurations and dicentric chromosomes in four OS cell lines was quantified. An increased level of anaphase bridges and dicentrics was observed in all the OS cell lines. There was also a strong association between the frequencies of anaphase bridges, dicentrics, centrosomal anomalies, and multipolar mitotic figures in all the OS cell lines, indicating a possible link in the mechanisms that led to the structural and numerical instabilities observed in OS. In summary, this study has provided strong support for the role of the BFB cycle in generating the extensive structural chromosome aberrations, as well as cell-to-cell cytogenetic variation observed in OS, thus conferring the genetic diversity for OS tumor progression.

Anaphase↗

PubMed2006

Stem cell enrichment approaches.

Adult somatic tissue, and the tumours that arise therein, are maintained by a small population of stem cells. In addition to the self-renewal potential and pluripotency, these stem cells express several phenotypic traits that can be used in isolation and enrichment strategies. Since most of the traits are not exclusive to the stem cells however, the resultant populations are typically heterogeneous and variable from one isolation to another. In this article, we review the strategies for isolation of stem cells, and the limitations thereof, with emphasis on mesenchymal tissue and bone tumours. The emerging evidence suggests that stem cell is not a distinct entity, but rather an indefinite state along a spectrum, characterized by phenotypic traits, epigenetic factors and the microenvironment.

Animals↗

PubMed2006

Three-color FISH analysis of TMPRSS2/ERG fusions in prostate cancer indicates that genomic microdeletion of chromosome 21 is associated with rearrangement.

The recent description of novel recurrent gene fusions in approximately 80% of prostate cancer (PCa) cases has generated increased interest in the search for new translocations in other epithelial cancers and emphasizes the importance of understanding the origins and biologic implications of these genomic rearrangements. Analysis of 15 PCa cases by reverse transcription-polymerase chain reaction was used to detect six ERG-related gene fusion transcripts with TMPRSS2. No TMPRSS2/ETV1 chimeric fusion was detected in this series. Three-color fluorescence in situ hybridization confirms that TMPRSS2/ERG fusion may be accompanied by a small hemizygous sequence deletion on chromosome 21 between ERG and TMPRSS2 genes. Analysis of genomic architecture in the region of genomic rearrangement suggests that tracts of microhomology could facilitate TMPRSS2/ERG fusion events.

Chromosome Aberrations↗

PubMed2005

An integrated mBAND and submegabase resolution tiling set (SMRT) CGH array analysis of focal amplification, microdeletions, and ladder structures consistent with breakage-fusion-bridge cycle events in osteosarcoma.

Osteosarcoma (OS) is characterized by chromosomal instability and high-copy-number gene amplification. The breakage-fusion-bridge (BFB) cycle is a well-established mechanism of genomic instability in tumors and in vitro models used to study the origins of complex chromosomal rearrangements and cancer genome amplification. However, until now, there have been no high-resolution cytogenetic or genomic array studies of BFB events in OS. In the present study, multicolor banding (mBAND) FISH and submegabase resolution tiling set (SMRT) array comparative genomic hybridization (CGH) were used to identify and map genomic signatures of BFB events in four OS cell lines and one patient tumor. The expected intermediates associated with BFB-dicentric chromosomes, inverted duplications, and intra- and interchromosomal amplifications-were identified. mBAND analysis provided detailed mapping of rearrangements in 1p, 6p, and 8q and showed that translocation junctions were often in close proximity to fragile sites. More detailed mBAND studies of OS cell line MG-63 revealed ladderlike FISH signals of equally spaced interchromosomal coamplifications of 6p21, 8q24, and 9p21-p22 in a homogeneously staining region (hsr). Focal amplifications that concordantly mapped to the hsr were localized to discrete genomic intervals by SMRT array CGH. The complex amplicon structure in this hsr suggests focal amplifications immediately adjacent to microdeletions. Moreover, the genomic regions in which there was deletion/amplification had a preponderance of fragile sites. In summary, this study has provided further support for the role of the BFB mechanism and fragile sites in facilitating gene amplification and chromosomal rearrangement in OS.

Cell Line, Tumor↗