Characterisation of deregulated micrornas in human non-small cell lung cancer and their role in tumour angiogenesis and metastasis / Ho Chai San
Lung cancer is the most commonly diagnosed cancer worldwide and ranks third in Malaysia with increasing mortality rate over the years. This is often due to late presentation of disease at the metastatic stage. MicroRNAs, even though are only small single-stranded non-coding RNAs, have been proven...
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| Format: | Thesis |
| Published: |
2017
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| Online Access: | http://studentsrepo.um.edu.my/9865/1/Ho_Chai_San.pdf http://studentsrepo.um.edu.my/9865/2/Ho_Chai_San_%E2%80%93_Thesis.pdf http://studentsrepo.um.edu.my/9865/ |
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| Summary: | Lung cancer is the most commonly diagnosed cancer worldwide and ranks third
in Malaysia with increasing mortality rate over the years. This is often due to late
presentation of disease at the metastatic stage. MicroRNAs, even though are only small
single-stranded non-coding RNAs, have been proven to be mighty micromanagers of
gene expression in many biological processes including cancer metastasis and
angiogenesis. They are comprehensively studied and thus proposed as potential
molecular targets for cancer treatment. However, the mechanisms microRNA is used to
modulate lung cancer metastasis remain unclear. High and low invasive A549 and SKLU-
1 sub-cell lines selected through serial transwell invasion assay for at least seven
generations from their parental cell lines, were used to analyse differentially expressed
metastasis-related microRNAs. Invasive phenotype in high invasive A549 and SK-LU-1
cells was found to be accompanied by gain of miR-92b and miR-378 expression as well
as loss of miR-1827 expression. Investigation into the roles of these microRNAs in
metastasis, particularly invasion, migration and angiogenesis, revealed that miR-378
functions as a cell invasion regulator while miR-1827 modulates cell migration. Both
microRNAs work in opposite manner to mediate angiogenesis. The conversion from
low invasive to high invasive phenotype by miR-378 and anti-miR-1827 was shown to
involve epithelial-mesenchymal transition. MiR-92b, on the other hand, is not
significant during the course of metastasis and angiogenesis in non-small cell lung
cancer. Subsequently, using bioinformatics approaches, dual luciferase reporter assay
and Western blotting, RBX1 and CRKL were identified as new targets of miR-378 and
miR-1827, respectively. Changes in cell invasion and migratory potentials were directly
controlled by RBX1 and CRKL under the negative regulation of miR-378 and miR-1827,
as the repressive and inductive effects of microRNA mimics and hairpin inhibitors
could be rescued by RBX1/ CRKL overexpression and knockdown. Nevertheless, restoration of RBX1 and CRKL expression only slightly reverted the angiogenic
activities, suggesting that angiogenesis in non-small cell lung cancer is not only
dependent on RBX1 and CRKL. These in vitro results were translated into in vivo
zebrafish embryo model. MiR-378 hairpin inhibitors- and miR-1827 mimics-treated
high invasive A549 cells demonstrated reduced number of metastases and ectopic vessel
formation in the embryonic fish compared to negative controls. Collectively, these
findings indicate that miR-378 and miR-1827 play important roles in metastasis and
angiogenesis by regulating epithelial-mesenchymal transition in non-small cell lung
cancer. In particular, miR-378 promotes cell invasion by targeting RBX1 while miR-
1827 suppresses cell migration by targeting CRKL. However, RBX1 and CKRL are not
the major players in miR-378- and miR-1827-mediated angiogenesis.
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