Co-ordinate loss of protein kinase C and multidrug resistance gene expression in revertant MCF-7/Adr breast carcinoma cells

Br J Cancer. 1997;75(9):1330-5. doi: 10.1038/bjc.1997.225.


The aim of this study was to investigate the link between protein kinase C (PKC) and multidrug resistance (mdr) phenotype. The expression of both was studied in doxorubicin-resistant MCF-7/Adr cells as they reverted to the wild-type phenotype when cultured in the absence of drug. The following parameters were measured in cells 4, 10, 15, 20 and 24 weeks after removal of doxorubicin; (1) sensitivity of the cells towards doxorubicin; (2) levels of P-glycoprotein (P-gp) and MDR1 mRNA; (3) levels and cellular localization of PKC isoenzyme proteins alpha, theta and epsilon; and (4) gene copy number of PKC-alpha and MDR1 genes. Cells lost their resistance gradually with time, so that by week 24 they had almost completely regained the drug sensitivity seen in wild-type MCF-7 cells. P-gp levels measured by Western blot mirrored the change in doxorubicin sensitivity. By week 20, P-gp had decreased to 18% of P-gp protein levels at the outset, and P-gp was not detectable at week 24. Similarly, MDR1 mRNA levels had disappeared by week 24. MCF-7/Adr cells expressed more PKCs-alpha and -theta than wild-type cells and possessed a different cellular localization of PKC-epsilon. The expression and distribution pattern of these PKCs did not change for up to 20 weeks, but reverted back to that seen in wild-type cells by week 24. MDR1 gene amplification remained unchanged until week 20, but then was lost precipitously between weeks 20 and 24. The PKC-alpha gene was not amplified in MCF-7/Adr cells. The results suggest that MCF-7/Adr cells lose MDR1 gene expression and PKC activity in a co-ordinate fashion, consistent with the existence of a mechanistic link between MDR1 and certain PKC isoenzymes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / biosynthesis
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / genetics
  • Breast Neoplasms / drug therapy
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism*
  • DNA Primers / chemistry
  • Doxorubicin / pharmacology*
  • Drug Resistance, Multiple / genetics*
  • Female
  • Gene Amplification
  • Gene Expression Regulation, Neoplastic*
  • Genes, MDR / genetics*
  • Humans
  • Isoenzymes / biosynthesis
  • Polymerase Chain Reaction
  • Protein Kinase C / biosynthesis*
  • Protein Kinase C / genetics
  • RNA, Messenger / metabolism
  • Tumor Cells, Cultured


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • DNA Primers
  • Isoenzymes
  • RNA, Messenger
  • Doxorubicin
  • Protein Kinase C