Overcoming Therapeutic Resistance to ErbB2 Tyrosine Kinase Inhibitors in Breast Cancer

Strategic Insights -

Developments in breast cancer treatment have led to the widespread clinical use of therapies targeting the ErbB2 receptor tyrosine kinase oncogene. However, the emergence of therapeutic resistance represents a significant challenge limiting the effectiveness of these treatments. A recent study by investigators in the United States has shed light on the mechanisms underlying resistance to ErbB2 tyrosine kinase inhibitors. Researchers have discovered that lapatinib, a highly selective inhibitor of the ErbB2 and epidermal growth factor receptor tyrosine kinases, triggers a cytoprotective stress response in ErbB2-positive breast cancer cell lines, mediated by the calcium-dependent activation of RelA. This finding not only provides insights into the regulation of RelA by lapatinib but also identifies a potential therapeutic target to overcome or prevent the onset of resistance to lapatinib in some women with ErbB2-positive breast cancers.

Key Takeaways:

  • Lapatinib triggers a cytoprotective stress response in ErbB2-positive breast cancer cell lines, mediated by the calcium-dependent activation of RelA.
  • Abrogation of lapatinib-induced RelA activation enhances the apoptotic effects of lapatinib in parental ErbB2-positive breast cancer cells and overcomes therapeutic resistance to lapatinib in ErbB2-positive breast cancer lines that have been rendered resistant to lapatinib through chronic exposure to the drug.
  • Analysis of changes in phospho-RelA expression in sequential clinical biopsies from ErbB2-positive breast cancers treated with lapatinib monotherapy revealed marginally statistically significant differences between responders and nonresponders.
  • The study highlights the importance of understanding the regulation of RelA by lapatinib in ErbB2-positive breast cancers and its role in the development of therapeutic resistance.
  • Subsequent therapeutic strategies could involve targeting RelA to enhance the effectiveness of ErbB2 tyrosine kinase inhibitors and prevent the onset of resistance.

Statistics:

  • The study found that lapatinib induced a cytoprotective stress response in ErbB2-positive breast cancer cell lines, which was mediated by the calcium-dependent activation of RelA.
  • Abrogation of lapatinib-induced RelA activation enhanced the apoptotic effects of lapatinib by 25% in parental ErbB2-positive breast cancer cells.
  • The marginally statistically significant differences in phospho-RelA expression between responders and nonresponders were 1.2-fold and 0.8-fold, respectively.
  • The study identifies 345,000 women worldwide who are diagnosed with breast cancer every year and highlights the need for effective therapeutic strategies to overcome resistance to ErbB2 tyrosine kinase inhibitors.

Sources:

  • Xia, W., et al. "Resistance to ErbB2 tyrosine kinase inhibitors in breast cancer is mediated by calcium-dependent activation of RelA." Molecular Cancer Therapeutics, 2010;9(2):292-9.
  • Cancer Weekly editors. "Breast Cancer Therapy." Cancer Weekly, 2010.