Document Type: Research Articles
Diagnostic and Biomedicine, Faculty of Health Science, Universiti Sultan Zainal Abidin, Gong Badak Compus, Kuala Nerus, Terengganu, Malaysia.
Department of Haematology, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Malaysia.
Institute for Community Health Development, Gong Badak Compus, Kuala Nerus, Terengganu, Malaysia.
Background: Epigenetic silencing of tumor suppressor genes (TSG) is involved in development and
progression of cancers. Re-expression of TSG is inversely proportionate with STAT3 signaling pathways.
Demethylation of DNA by 5-Azacytidine (5-Aza) results in re-expression of silenced TSG. Forced expression of
PRG2 by 5-Aza induced apoptosis in cancer cells. Imatinib is a tyrosine kinase inhibitor that potently inhibits BCR/
ABL tyrosine kinase resulting in hematological remission in CML patients. However, majority of CML patients treated
with imatinib would develop resistance under prolonged therapy. Methods: CML cells resistant to imatinib were
treated with 5-Aza and cytotoxicity of imatinib and apoptosis were determined by MTS and annexin-V, respectively.
Gene expression analysis was detected by real time-PCR, STATs activity examined using Western blot and methylation
status of PRG2 was determined by pyrosequencing analysis. Result: Expression of PRG2 was significantly higher in
K562-R+5-Aza cells compared to K562 and K562-R (p=0.001). Methylation of PRG2 gene was significantly decreased
in K562-R+5-Aza cells compared to other cells (p=0.021). STAT3 was inactivated in K562-R+5-Aza cells which showed
higher sensitivity to imatinib. Conclusion: PRG2 gene is a TSG and its overexpression might induce sensitivity to
imatinib. However, further studies are required to evaluate the negative regulations of PRG2 on STAT3 signaling.