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Contributor Information

  • Name Anne Lykkesfeldt
  • Institute Danish Cancer Society

Tool Details

  • Tool name: MCF7/LetR-2 Cell Line
  • Tool type: Cell Lines
  • Tool sub-type: Continuous
  • Parental cell line: MCF7
  • Organism: Human
  • Tissue: Breast
  • Cancer type: Breast cancer
  • Disease: Cancer
  • Growth properties: Breast cancer cell line resistant to the aromatase inhibitor letrozole. Estrogen receptor negative.
  • Conditional: No
  • Description: The MCF7/LetR-2 Cell Line was developed as a model of resistance to anti-cancer treatment with aromatase inhibitors. Third generation aromatase inhibitors (AIs) have proven to be effective treatment for estrogen receptor positive (ER+) breast cancer and are today recommended as first line endocrine therapy for postmenopausal ER+ breast cancer patients, making up the majority of breast cancer patients. However, a major problem is development of resistance against AIs. Since molecular mechanisms of AI resistance are largely undisclosed, the development of cell lines resistant to the non-steroidal AI letrozole allows the study of the molecular basis for resistance to AIs to unravel new targets for treatment.
  • Research area: Cancer; Drug development
  • Production details: Letrozole-resistant cell lines were established from MCF-7 cells grown in medium with 10% NCS and 10â?‚ˆ?‚Â’7 M testosterone. A culture of MCF-7 cells were treated with 10â?‚ˆ?‚Â’6 M letrozole for one week, trypsinized and seeded in serial dilutions in 24-well plates. Single colonies were transferred to new wells and gradually expanded in medium with letrozole. After ~2â?‚€?‚“3 months, the isolated colonies gave rise to letrozole-resistant cell lines, which could be grown in letrozole-containing medium with a weekly split ratio of ~1:25. The MCF-7 cell line was authenticated in January 2014 by DNA profiling using short tandem repeat loci and found to be matching the genetic profile reported for the MCF-7 cell line.
  • Cellosaurus ID: CVCL_5A18

  • For Research Use Only

Target Details

  • Target: Letrozole resistant

Application Details

  • Application notes: Human breast cancer cell line derived from MCF-7 cells Other related cell lines: - LetR-1, LetR-3 and LetR-4 resistant to the non-steroidal AI letrozole - ExeR-1, ExeR-2, ExeR-3 and ExeR-4 resistant to the steroidal AI exemestane - AnaR-1, AnaR-2, AnaR-3 and AnaR-4 resistant to the non-steroidal AI anastrozole Passage 436 (AL3243, AL3244)


  • Format: Frozen
  • Passage number: Passage 436 (AL3243, AL3244)
  • Growth medium: Phenol-red-free DMEM/F12 medium supplemented with 10% newborn calf serum, 2.5 mM Glutamax, 6 ng/ ml insulin, 0.1 uM testosterone and 1 uM letrozole.
  • Shipping conditions: Dry ice



  •   Hole et al. 2015. Breast Cancer Res Treat. 149(3):715-26. PMID: 25667100.
  •   Hole et al. 2015. Int J Oncol. 46(4):1481-90. PMID: 25625755.
  •   Aurora kinase A and B as new treatment targets in aromatase inhibitor-resistant breast cancer cells.
  •   New cell culture model for aromatase inhibitor-resistant breast cancer shows sensitivity to fulvestrant treatment and cross-resistance between letrozole and exemestane.