title: Fractionated irradiation can induce functionally relevant multidrug resistance gene and protein expression in human tumor cell lines.
abstract: The molecular basis of radiotherapy-related multidrug resistance (MDR) is still unclear. Here we report on a study investigating the effect of fractionated irradiation on expression of the MDR-associated proteins P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP), and lung resistance-related protein (LRP), the respective mRNAs, and the functional consequences. Cells of six colon and five breast cancer cell lines were irradiated with a total dose of 27 Gy, five fractions of 1.8 Gy per week. The mRNA expression was measured by quantitative RT-PCR, protein levels and drug sensitivity to cisplatin, doxorubicin and bendamustine were assessed by flow cytometry. Breast cancer cell lines showed enhancement of the mRNAs encoding for P-gp, MRP1 and LRP in comparison to nonirradiated cells. No up-regulation of the three mRNA species was observed in the colon cancer cell lines. After irradiation, three breast cancer cell lines showed an up-regulation of LRP, one line an up-regulation of MRP1, and four lines a small up-regulation of P-gp. In the colon cancer cell lines, radiation induced significant enhancement of all three proteins. In comparison to controls, the irradiated cells lines showed a significant resistance to cisplatin, doxorubicin and bendamustine. This study confirms the prior reports of enhancement of P-gp and MRP1 after irradiation, which is accompanied by a multidrug resistance phenomenon, but in addition proposes a novel mechanism in the appearance of MDR after radiation-induced enhancement of LRP.
authors.affiliation: University Hospital Ulm, Department of Radiotherapy, 89081 Ulm, Germany. dirk.bottke@uniklinik-ulm.de
authors.forename: Dirk
authors.initials: D
authors.lastname: Bottke
authors.forename: Daniel
authors.initials: D
authors.lastname: Koychev
authors.forename: Antonia
authors.initials: A
authors.lastname: Busse
authors.forename: Karin
authors.initials: K
authors.lastname: Heufelder
authors.forename: Thomas
authors.initials: T
authors.lastname: Wiegel
authors.forename: Eckhard
authors.initials: E
authors.lastname: Thiel
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hinkelbein
authors.forename: Ulrich
authors.initials: U
authors.lastname: Keilholz
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics*; D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D005786:Gene Expression Regulation / Q000528:radiation effects*; D006801:Humans; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics*; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012680:Sensitivity and Specificity; D020394:Vault Ribonucleoprotein Particles / Q000235:genetics*; D000099187:Major Vault Protein
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012333:RNA, Messenger; D020394:Vault Ribonucleoprotein Particles; D000099187:Major Vault Protein