Clusterin (CLU) is an important
glycoprotein involved in various cellular functions. Different reports have mentioned that the two
isoforms of CLU; secretary (sCLU) and nuclear (nCLU) have opposite (paradoxical) roles in
cancer development. sCLU provides pro-survival signal, whereas nCLU is involved in pro-apoptotic signaling. However, the molecular mechanism of CLU gene regulation is not clear as of yet. We hypothesize that CLU gene is regulated by DNA methylation and histone modifications and
clusterin plays an important role in
colon cancer. To evaluate the hypothesis, we investigated CLU expression in
colon cancer tissues and DNA methylation and
histone modification status of CLU gene promoter. It is apparent from immonohistology data that both benign and cancerous (primary and
metastasis)
formalin fixed
paraffin embedded (FFPE) tissue samples exhibit CLU expression. However and interestingly only noncancerous tissue samples show nCLU expression. Ectopic expression of nCLU either by epigenetic modulators or by nCLU transfection is responsible for
colon cancer cell death. To clarify the molecular mechanisms for regulation of expression of CLU
isoforms, we have analyzed DNA methylation and histone modifications, such as
histone H3K9me3, H3K27me3,
H3K4me3, and H3K9AcS10P patterns around the CLU promoter. There is no remarkable change in the DNA methylation status upon treatment of the cells by AZA,
TSA and SAM. Our findings clearly show that promoter
histone H3K9me3 and H3K27me3 marks are elevated in comparison to
H3K4me3 and H3K9AcS10P marks in
colon cancer cell lines.