An increase of cytochrome C oxidase mediated disruption of gemcitabine incorporation into DNA in a resistant KB clone

Xiyong Liu, Bingsen Zhou, Shu Mi, Lijun Xue, Jennifer Shih, Janice Lee, Jennifer Chau, Frank Un, Yun Yen

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Mechanistic aberrations leading to Gemcitabine (2′,2′-dFdCyd,2,2-difluorodeoxycytidine, Gem) resistance may include alteration in its transport, metabolism and incorporation into DNA. To explore the mechanism of Gem resistance, the restriction fragment differential display PCR (RFDD-PCR) was employed to compare the mRNA expression patterns of KBGem (Gem resistant), KBHURs (hydroxyurea resistant) and KBwt (parental KB cell). Nine gene fragments were overexpressed specifically in the KBGem clone. Sequencing and BLAST results showed that three fragments represent cytochrome C oxidase (CCOX, respiration complex IV) subunit III (CCOX3). The cDNA microarray confirmed that the mRNAs of CCOX and ATP synthase subunits were upregulated in KBGem as compared to KBwt and KBHURs. The increase in CCOX1 protein and activity led to the increase of free ATP concentration, which is consistent with the gene expression profile of KBGem. Furthermore, the sensitivity to Gem could be reversed by sodium azide, a CCOX inhibitor. Following the treatment of sodium azide, the cellular accumulation of [3H]-Gem increased in a dose (of azide)-dependent manner, which is associated with increase of [3H]-Gem incorporation into DNA in KBGem. In summary, an increase of CCOX activity and free ATP level may reduce the transport, metabolism and DNA incorporation of Gem, resulting in Gem resistance.

Original languageEnglish
Pages (from-to)1927-1938
Number of pages12
JournalBiochemical Pharmacology
Volume73
Issue number12
DOIs
Publication statusPublished - Jun 15 2007
Externally publishedYes

Keywords

  • ATP
  • Cytochrome C oxidase
  • Drug resistance
  • Gemcitabine
  • Ribonucleotide reductase

ASJC Scopus subject areas

  • Pharmacology

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