Decreased Camptothecin Sensitivity of the Stem-Cell-Like Fraction of Caco2 Cells Correlates with an Altered Phosphorylation Pattern of Topoisomerase I

作者：Roy Amit; Tesauro Cinzia; Frohlich Rikke; Hede Marianne S; Nielsen Maria J; Kjeldsen Eigil; Bonven Bjarne; Stougaard Magnus; Gromova Irina; Knudsen Birgitta R^*

来源：PLos One, 2014, 9(6): e99628.

DOI：10.1371/journal.pone.0099628

The CD44+ and CD44- subpopulations of the colorectal cancer cell line Caco2 were analyzed separately for their sensitivities to the antitumor drug camptothecin. CD44+ cells were less sensitive to camptothecin than CD44- cells. The relative resistance of CD44+ cells was correlated with (i) reduced activity of the nuclear enzyme topoisomerase I and (ii) insensitivity of this enzyme to camptothecin when analyzed in extracts. In contrast, topoisomerase I activity was higher in extracts from CD44- cells and the enzyme was camptothecin sensitive. Topoisomerase I from the two subpopulations were differentially phosphorylated in a manner that appeared to determine the drug sensitivity and activity of the enzyme. This finding was further supported by the fact that phosphorylation of topoisomerase I in CD44+ cell extract by protein kinase CK2 converted the enzyme to a camptothecin sensitive, more active form mimicking topoisomerase I in extracts from CD44- cells. Conversely, dephosphorylation of topoisomerase I in extracts from CD44- cells rendered the enzyme less active and camptothecin resistant. These findings add to our understanding of chemotherapy resistance in the Caco2 CD44+ cancer stem cell model.

• 出版日期2014-6-24