The identification of two germ-line mutations in the human breast cancer resistance protein gene that result in the expression of a low/non-functional protein

Pharm Res. 2007 Jun;24(6):1108-17. doi: 10.1007/s11095-007-9235-2. Epub 2007 Mar 21.

Abstract

Purpose: We examined the effects of the nine nonsynonymous germ-line mutations/SNPs in the breast cancer resistance protein (BCRP/ABCG2) gene on the expression and function of the protein.

Materials and methods: We generated cDNAs for each of these mutants (G151T, C458T, C496G, A616C, T623C, T742C, T1291C, A1768T, and G1858A BCRP) and compared the effects of their exogenous expression in PA317 cells with a wild-type control.

Results: PA/F208S cells (T623C BCRP-transfectants) expressed marginal levels of a BCRP protein species (65kDa), which is slightly smaller than wild-type (70kDa), but this mutant did not appear on the cell surface or confer drug resistance. PA/F431L cells (T1291C BCRP-transfectants) were found to express both 70 kDa and 65 kDa BCRP protein products. In addition, although PA/F431L cells expressed 70 kDa BCRP at comparable levels to PA/WT cells, they showed only marginal resistance to SN-38. PA/T153M cells (C458T BCRP-transfectants) and PA/D620N cells (G1858A BCRP-transfectants) expressed lower amounts of BCRP and showed lower levels of resistance to SN-38 compared with PA/WT cells.

Conclusions: We have shown that T623C BCRP encodes a non-functional BCRP and that T1291C BCRP encodes a low-functional BCRP. Hence, these mutations may affect the pharmacokinetics of BCRP substrates in patients harboring these alleles.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily G, Member 2
  • ATP-Binding Cassette Transporters / genetics*
  • ATP-Binding Cassette Transporters / metabolism
  • Animals
  • Base Sequence
  • Breast Neoplasms / genetics*
  • Cells, Cultured
  • DNA Primers
  • DNA, Complementary
  • Germ-Line Mutation*
  • Humans
  • Mice
  • Neoplasm Proteins / genetics*
  • Neoplasm Proteins / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transfection

Substances

  • ABCG2 protein, human
  • ATP Binding Cassette Transporter, Subfamily G, Member 2
  • ATP-Binding Cassette Transporters
  • DNA Primers
  • DNA, Complementary
  • Neoplasm Proteins