Apoptosis-induced chromosome breaks and chromosome rearrangements at mixed lineage leukaemia breakpoint cluster region in nasopharyngeal and leukaemia cells
Chromosome rearrangements such as additions, deletions, translocations and inversions are commonly observed in various types of cancer. In leukaemia, the Mixed Lineage Leukaemia (MLL) gene on chromosome llq23 had been found to translocate with many partner genes, resulting in the generation of fu...
| Main Author: | |
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| Format: | Thesis |
| Language: | English |
| Published: |
Universiti Malaysia Sarawak, (UNIMAS)
2008
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| Online Access: | http://ir.unimas.my/id/eprint/15435/ http://ir.unimas.my/id/eprint/15435/1/Grace%20%20%28ft%29.pdf |
| _version_ | 1848837851370749952 |
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| author | Siaw, Grace Ee Lu |
| author_facet | Siaw, Grace Ee Lu |
| author_sort | Siaw, Grace Ee Lu |
| building | UNIMAS Institutional Repository |
| collection | Online Access |
| description | Chromosome rearrangements such as additions, deletions, translocations and inversions
are commonly observed in various types of cancer. In leukaemia, the Mixed Lineage
Leukaemia (MLL) gene on chromosome llq23 had been found to translocate with many
partner genes, resulting in the generation of fusion genes. Chromosomal deletions and
additions at llq23 had been reported in nasopharyngeal carcinoma (NPC) though it was
unknown which gene was involved. The apoptotic nuclease was proposed to be involved
in these chromosomal rearrangements by fragmenting the genomic DNA into small
fragments forming the nucleosomal DNA ladder. In leukaemia, it was possible that the
MLL gene and its partner genes were being cleaved during apoptosis. In an effort to
rescue the cells, the DNA repair system may erroneously join the DNA fragments,
resulting in chromosome translocation. Epstein-Barr virus (EBV) infection and/or other
factors may induce apoptosis in NPC cells, resulting in chromosomal breaks and
subsequent rejoining may take place during the attempted DNA repair. As a result, the
surviving cells may harbour chromosome rearrangements such as deletions. Therefore,
the aim of this study was to detect apoptosis-induced chromosome breaks and
rearrangements using NPC and leukaemic cell lines as model systems. These cell lines
were induced to undergo apoptosis by overgrowing the cells to high densities followed by
revival in fresh medium to rescue them. The leukaemic cells were also induced to
undergo apoptosis by treatment for short time period with the low and high
concentrations of etoposide (VP-16). This was followed by revival of the apoptotic cells
in fresh medium to rescue them. In addition, both the NPC and leukaemic cells were
also treated with different concentrations of hydrogen peroxide (H202) to induce
apoptosis. Subsequently, detection of chromosome rearrangements and breaks was performed. Nested PCR using primers specific for MLL and AF9 (one of the common
translocation partners of MLL) was also performed. For NPC cells, nested PCR using
the primers specific for the MLL bcr and the telomere were carried out to detect deleted
chromosome with telomere sequence added. Our result showed that both the cell
density-induced apoptosis in NPC and leukaemic cells generated chromosomal breaks
near the 3' end of the MLL bcr. There was no telomere capturelhealing detected at the
cleavage sites of the revived NPC cells. The sequenced PCR bands of multiple sizes were
found to originate from other chromosomes. Both the 3' and 5' breaks of the MLL bcr
were detected in the revived VP-16-treated leukaemic cells. In some of the samples,
these 5' breaks were located centromeric to the MLL bcr region. However, no
translocation of other genes to the break sites was detected. NPC cells treated with
H202 showed chromosomal breaks near the 3' end of the MLL bcr with no telomere
sequences added. However, in leukaemic cells, translocation of the MLL bcr with
unknown genes from other chromosomes was detected. |
| first_indexed | 2025-11-15T06:46:13Z |
| format | Thesis |
| id | unimas-15435 |
| institution | Universiti Malaysia Sarawak |
| institution_category | Local University |
| language | English |
| last_indexed | 2025-11-15T06:46:13Z |
| publishDate | 2008 |
| publisher | Universiti Malaysia Sarawak, (UNIMAS) |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | unimas-154352023-08-09T07:02:12Z http://ir.unimas.my/id/eprint/15435/ Apoptosis-induced chromosome breaks and chromosome rearrangements at mixed lineage leukaemia breakpoint cluster region in nasopharyngeal and leukaemia cells Siaw, Grace Ee Lu R Medicine (General) Chromosome rearrangements such as additions, deletions, translocations and inversions are commonly observed in various types of cancer. In leukaemia, the Mixed Lineage Leukaemia (MLL) gene on chromosome llq23 had been found to translocate with many partner genes, resulting in the generation of fusion genes. Chromosomal deletions and additions at llq23 had been reported in nasopharyngeal carcinoma (NPC) though it was unknown which gene was involved. The apoptotic nuclease was proposed to be involved in these chromosomal rearrangements by fragmenting the genomic DNA into small fragments forming the nucleosomal DNA ladder. In leukaemia, it was possible that the MLL gene and its partner genes were being cleaved during apoptosis. In an effort to rescue the cells, the DNA repair system may erroneously join the DNA fragments, resulting in chromosome translocation. Epstein-Barr virus (EBV) infection and/or other factors may induce apoptosis in NPC cells, resulting in chromosomal breaks and subsequent rejoining may take place during the attempted DNA repair. As a result, the surviving cells may harbour chromosome rearrangements such as deletions. Therefore, the aim of this study was to detect apoptosis-induced chromosome breaks and rearrangements using NPC and leukaemic cell lines as model systems. These cell lines were induced to undergo apoptosis by overgrowing the cells to high densities followed by revival in fresh medium to rescue them. The leukaemic cells were also induced to undergo apoptosis by treatment for short time period with the low and high concentrations of etoposide (VP-16). This was followed by revival of the apoptotic cells in fresh medium to rescue them. In addition, both the NPC and leukaemic cells were also treated with different concentrations of hydrogen peroxide (H202) to induce apoptosis. Subsequently, detection of chromosome rearrangements and breaks was performed. Nested PCR using primers specific for MLL and AF9 (one of the common translocation partners of MLL) was also performed. For NPC cells, nested PCR using the primers specific for the MLL bcr and the telomere were carried out to detect deleted chromosome with telomere sequence added. Our result showed that both the cell density-induced apoptosis in NPC and leukaemic cells generated chromosomal breaks near the 3' end of the MLL bcr. There was no telomere capturelhealing detected at the cleavage sites of the revived NPC cells. The sequenced PCR bands of multiple sizes were found to originate from other chromosomes. Both the 3' and 5' breaks of the MLL bcr were detected in the revived VP-16-treated leukaemic cells. In some of the samples, these 5' breaks were located centromeric to the MLL bcr region. However, no translocation of other genes to the break sites was detected. NPC cells treated with H202 showed chromosomal breaks near the 3' end of the MLL bcr with no telomere sequences added. However, in leukaemic cells, translocation of the MLL bcr with unknown genes from other chromosomes was detected. Universiti Malaysia Sarawak, (UNIMAS) 2008 Thesis NonPeerReviewed text en http://ir.unimas.my/id/eprint/15435/1/Grace%20%20%28ft%29.pdf Siaw, Grace Ee Lu (2008) Apoptosis-induced chromosome breaks and chromosome rearrangements at mixed lineage leukaemia breakpoint cluster region in nasopharyngeal and leukaemia cells. Masters thesis, Universiti Malaysia Sarawak. |
| spellingShingle | R Medicine (General) Siaw, Grace Ee Lu Apoptosis-induced chromosome breaks and chromosome rearrangements at mixed lineage leukaemia breakpoint cluster region in nasopharyngeal and leukaemia cells |
| title | Apoptosis-induced chromosome breaks and chromosome rearrangements at mixed lineage leukaemia breakpoint cluster region in nasopharyngeal and leukaemia cells |
| title_full | Apoptosis-induced chromosome breaks and chromosome rearrangements at mixed lineage leukaemia breakpoint cluster region in nasopharyngeal and leukaemia cells |
| title_fullStr | Apoptosis-induced chromosome breaks and chromosome rearrangements at mixed lineage leukaemia breakpoint cluster region in nasopharyngeal and leukaemia cells |
| title_full_unstemmed | Apoptosis-induced chromosome breaks and chromosome rearrangements at mixed lineage leukaemia breakpoint cluster region in nasopharyngeal and leukaemia cells |
| title_short | Apoptosis-induced chromosome breaks and chromosome rearrangements at mixed lineage leukaemia breakpoint cluster region in nasopharyngeal and leukaemia cells |
| title_sort | apoptosis-induced chromosome breaks and chromosome rearrangements at mixed lineage leukaemia breakpoint cluster region in nasopharyngeal and leukaemia cells |
| topic | R Medicine (General) |
| url | http://ir.unimas.my/id/eprint/15435/ http://ir.unimas.my/id/eprint/15435/1/Grace%20%20%28ft%29.pdf |