PDGFD up-regulation due to reversible promoter demethylation contributes
to gemcitabine resistance via STAT3 activation
Abstract
Background and Purpose. Drug resistance is a major problem in cancer
treatment with traditional or targeted therapeutics. Gemcitabine, a
traditional chemotherapeutics, is approved for several human cancers and
the first line treatment for locally advanced or metastatic pancreatic
ductal adenocarcinoma (PDAC). However, gemcitabine resistance is
frequently observed and a major problem in successful treatments of
these cancers and the mechanism of gemcitabine resistance remains
largely unknown. In this study, we aim to seek new and understand the
molecule mechanisms of gemcitabine resistance in PDAC. Experimental
Approach. Using whole genome Reduced Representation Bisulfite Sequencing
analysis, we investigated a gemcitabine resistant PDAC cell line M3K
compared with its parental MiaPaCa-2 cells and the resistance revertant
cell line Rev followed by detailed analyses of PDGFD in gemcitabine
resistance using MTT survival assay, bisulfite sequencing, Western blot,
siRNA knockdown and over-expression. Key Results. We found that 65 genes
had reversible methylation changes in their promoters in gemcitabine
resistant PDAC cells. One of these genes, PDGFD, was further studied in
detail for the reversible methylation change in its promoter and shown
to reversibly up-regulate in expression, contribute to gemcitabine
resistance in vitro and in vivo via activating STAT3 signaling in both
autocrine and paracrine manners. Its expression also positively
associates with poor outcome of PDAC patients. Conclusion and
Implications. Reversible epigenetic regulation may play an important
role in gemcitabine resistance and targeting PDGFD signaling may
alleviate gemcitabine resistance for PDAC treatment.