Model
Digital Document
Publisher
Florida Atlantic University
Description
A Down's Syndrome related Single Minded 2 gene (SIM2), previously known to be
associated with Trisomy 21 was predicted by bioinformatics to be colon cancer specific.
In previous work from the laboratory using a patient tissue repository, an isoform of this
gene, short form (SIM2-s) was shown to be colon cancer specific. Inhibition of SIM2-s
expression by antisense technology resulted in cancer-cell specific apoptosis within 24
hours. Microarray-based gene expression profiling of the antisense-treated colon cancer
cells provided a fingerprint of genes involving key cell cycle, apoptosis, DNA damage
and differentiation genes. Taking hints from the microarray database, experiments were
initiated to decipher the molecular mechanism underlying the cancer specific function of
the SIM2-s gene. Using an isogenic cell system, apoptosis was found to be dependent
on DNA damage and repair gene, GADD45-a. Further, key pathways including p38 MAP
kinase (MAPK) and specific caspases were essential for apoptosis. Programmed cell
death was not dependant on cell cycle and was preceded by the induction of terminal
differentiation. To clarify whether SIM2-s function is a critical determinant of differentiation, stable transfectants of SIM2-s were established in a murine adipocytic
cell line (3T3-L 1 ). SIM2-s overexpression caused a pronounced block of differentiation
of the pre-adipocytes into mature adipocytes. A study of the differentiation pathway in
3T3-L 1 cells suggested that this block occurs early on in the cascade. These results
supported the starting premise that SIM2-s is a critical mediator of cell differentiation. To
clarify whether the SIM2-s gene has transforming potential, the SIM2-s gene was
overexpressed in the NIH3T3 murine fibroblast cell line. The cells expressing the human
SIM2-s gene exhibited shorter doubling time, abrogation of growth serum requirement,
greater cell number at saturation density and focus formation. In vivo tumorigenicity
assays showed tumor formation with long latency. These results provide strong evidence
for the role of SIM2-s gene in tumor cell growth and differentiation, and validate drug
therapy use for the gene.
associated with Trisomy 21 was predicted by bioinformatics to be colon cancer specific.
In previous work from the laboratory using a patient tissue repository, an isoform of this
gene, short form (SIM2-s) was shown to be colon cancer specific. Inhibition of SIM2-s
expression by antisense technology resulted in cancer-cell specific apoptosis within 24
hours. Microarray-based gene expression profiling of the antisense-treated colon cancer
cells provided a fingerprint of genes involving key cell cycle, apoptosis, DNA damage
and differentiation genes. Taking hints from the microarray database, experiments were
initiated to decipher the molecular mechanism underlying the cancer specific function of
the SIM2-s gene. Using an isogenic cell system, apoptosis was found to be dependent
on DNA damage and repair gene, GADD45-a. Further, key pathways including p38 MAP
kinase (MAPK) and specific caspases were essential for apoptosis. Programmed cell
death was not dependant on cell cycle and was preceded by the induction of terminal
differentiation. To clarify whether SIM2-s function is a critical determinant of differentiation, stable transfectants of SIM2-s were established in a murine adipocytic
cell line (3T3-L 1 ). SIM2-s overexpression caused a pronounced block of differentiation
of the pre-adipocytes into mature adipocytes. A study of the differentiation pathway in
3T3-L 1 cells suggested that this block occurs early on in the cascade. These results
supported the starting premise that SIM2-s is a critical mediator of cell differentiation. To
clarify whether the SIM2-s gene has transforming potential, the SIM2-s gene was
overexpressed in the NIH3T3 murine fibroblast cell line. The cells expressing the human
SIM2-s gene exhibited shorter doubling time, abrogation of growth serum requirement,
greater cell number at saturation density and focus formation. In vivo tumorigenicity
assays showed tumor formation with long latency. These results provide strong evidence
for the role of SIM2-s gene in tumor cell growth and differentiation, and validate drug
therapy use for the gene.
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