Investigating the relationship between apoptosis and the matrix metalloproteinases
Apoptosis and matrix metalloproteinases remove redundant tissue. They are
independently described in similar situations but no causal relationship has been identified.
This thesis hypothesizes that the process of apoptosis induces MMP expression. A new cell
separation technique was developed allowing rapid separation of apoptotic and non-apoptotic
cells with 95% purity, something not previously described. Biotinylated Annexin- V was used
to label apoptotic cells and streptavadin-coated dynabeads and a magnetic particle separator
used to extract them. Apoptosis was induced in cell lines derived from colon and gastric
cancers and the cells separated and analysed using quantitative RT-PCR and real-time PCR.
In fibrosarcoma cells apoptosis effects large increases in MMP7 mRNA and decreases for the
inhibitor TIMP 4 whereas in malignant epithelial cells apoptosis increases production of
MTI-MMP, MMP2 and TIMP2 mRNA. In co-culture, apoptotic epithelial cells induce
mRNA production in fibrosarcoma cells for MTI-MMP and TIMP2~ MTI-MMP' combined
with TIMP2 is pivotal in the activation of MMP2. These results support the hypothesis that
the process of apoptosis leads to increased MMP production.
As chemotherapy largely functions by inducing apoptosis, the demonstration that
apoptosis may lead to increased matrix destruction and potential tumour shedding could
explain why, for many malignancies adjuvant or nee-adjuvant therapy is ineffective and why,
for others, efficacy is not as good in-vivo as predicted in-vitro.