ABCMdb

PMID: 19724874

Tsang TY, Tsang SW, Lai KP, Tsang WP, Co NN, Kwok TT
Facilitation of drug resistance development by gamma-irradiation in human cancer cells.
Oncol Rep. 2009 Oct;22(4):921-6., [PubMed]

Sentences

No. Mutations Sentence Comment

59 ABCB1 p.Gly10Arg HepG2 cells (G cells) were first subjected to radiation selection by two different regimes and the two radiation-conditioned sublines G2 and G10 cells; G2 cells survived after 10 days of 2 Gy radiation treatment while G10 cells survived after 2 days of 10 Gy radiation treatment. G, G2 and G10 cells were then incubated with increasing concentration of Dox for up to 10 bc;M and the three drug-selected sublines GR, G2R and G10R cells, which are the G, G2 and G10 cells survived after Dox treatment, respectively. Login to comment 74 ABCB1 p.Gly10Arg ABCB1 p.Gly10Arg By Western blot analysis, the protein level of Pgp in GR, G2R and G10R cells, which are the G, G2 and G10 cells survived after Dox selection respectively, were found to be significantly higher than that of their respective parental cells; G2R > GR > G10R cells (Fig. 2A). Login to comment 75 ABCB1 p.Gly10Arg ABCB1 p.Gly10Arg By RT-PCR, the mdr1 mRNA level was also highly expressed in GR, G2R and G10R cells; G2R > G10R > GR cells (Fig. 2B). Login to comment 78 ABCB1 p.Gly10Arg To investigate whether this is the case in the GR, G2R and G10R cells, Southern blot analysis was performed. Login to comment 80 ABCB1 p.Gly10Arg The fold increases in the mdr1 gene copy number in GR, G2R and G10R were 2.87&#b1;0.24, 12.80&#b1;0.45 and 5.49&#b1;0.37, respectively. Login to comment 83 ABCB1 p.Gly10Arg GR, G2R and G10R cells were highly resistant to Dox (Fig. 3A), Taxol, vincristine and etoposide (data not shown) when compared with their respective parental cells. Login to comment 98 ABCB1 p.Gly10Arg Furthermore, by assessing the sensitivity at a higher Dox concentration, G2R cells which have the highest Pgp overexpression are also the most resistant towards Dox (IC50 >10 bc;M), followed by G10R cells (IC50 = 3.5 bc;M) and GR cells (IC50 = 3.0 bc;M). Login to comment 103 ABCB1 p.Gly10Arg As expected, it was shown that GR, G2R and G10R cells have a much lower level of Dox accumulation when compared with their respective parental cells (Fig. 3B). Login to comment 107 ABCB1 p.Gly10Arg It was found that verapamil sensitized the Dox response in all HepG2 cells while the sensitization effect is more significant in the GR, G2R and G10R cells (Fig. 3A). Login to comment 108 ABCB1 p.Gly10Arg In addition, verapamil also increased the intracellular Dox accumulation and the effect was more significant in the GR, G2R and G10R cells (Fig. 3B). Login to comment 115 ABCB1 p.Gly10Arg ABCB1 p.Gly10Arg The Dox resistance in G2R cells remained unchanged for up to 11 weeks in Dox-free medium while decayed in GR and G10R cells; GR cells showed greater decay than G10R cells (Fig. 4A). Login to comment 117 ABCB1 p.Gly10Arg Dox sensitivity, mdr1 expression level and mdr1 gene amplification in GR, G2R and G10R cells culturing in Dox-free medium. Login to comment 118 ABCB1 p.Gly10Arg GR, G2R and G10R cells were cultured in Dox-free medium for up to 11 weeks. Login to comment 119 ABCB1 p.Gly10Arg (A) The Dox sensitivity of the GR, G2R and G10R cells was determined by MTT assay in 2-week intervals. Login to comment 120 ABCB1 p.Gly10Arg (c6;) Represents GR cells (a0;) represents G2R cells and (b2;) represents G10R cells. Login to comment 127 ABCB1 p.Gly10Arg However, even in Dox-free medium for 11 weeks, a low level of drug resistance was still maintained in the GR and G10R cells. Login to comment 129 ABCB1 p.Gly10Arg For G10R cells, the percentage survival towards 0.2 bc;M Dox was 47% (Fig. 4A) in comparison with 3% of parent G10 cells (Fig. 3A). Login to comment 130 ABCB1 p.Gly10Arg The Pgp protein level decreased by 80% in GR cells, followed by 40% in G10R cells while only a slight decrease was seen in G2R cells when cultured in Dox-free condition for 11 weeks (Fig. 4B). Login to comment 132 ABCB1 p.Gly10Arg For mdr1 gene amplification, the level of amplification in GR and G10R cells was reduced greatly while there was no significant change in G2R cells (Fig. 4D). Login to comment 142 ABCB1 p.Gly10Arg Even though all the Dox-selected HepG2 cells demonstrate drug resistance property associated with mdr1 overexpression, the characteristics of drug resistance is, however, different among the GR, G2R and G10R cells. Login to comment 156 ABCB1 p.Gly10Arg ABCB1 p.Gly10Arg However, the form of mdr1 gene amplification in G2R cells will likely be different from that in the G10R and GR cells as the mdr1 amplification in G2R cells persisted in the absence of Dox while the amplification decayed in G10R cells and even more in GR cells (Fig. 4D). Login to comment