Related Experiment Video
Updated: Sep 26, 2026
Testing Targeted Therapies in Cancer using Structural DNA Alteration Analysis and Patient-Derived Xenografts
Published on: July 25, 2020
Medulloblastoma sensitivity to 17-allylamino-17-demethoxygeldanamycin requires MEK/ERKM
Christopher Calabrese1, Adrian Frank, Kirsteen Maclean
1Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
Abstract:
ERBB2 increases the sensitivity of breast cancer cells to the HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG). This has been attributed to the disruption of ERBB3/ERBB2 heterodimers that maintain a crucial cell survival signal via phosphatidylinositol 3-kinase/AKT. ERBB2 confers a poor clinical outcome in medulloblastoma, the most common malignant pediatric brain tumor. Here, we show that medulloblastoma cell sensitivity to 17-AAG is directly related to ERBB2 expression level. Furthermore, overexpression of exogenous ERBB2 in these cells induces spontaneous homodimerization, further enhancing cell sensitivity to 17-AAG. In contrast to breast cancer cells, this increased sensitivity to 17-AAG does not result from cell dependence on AKT1 activity. Rather, we show that 17-AAG generates a dose- and time-dependent increase in MEK/ERK signaling that is required for the drug to inhibit the proliferation of medulloblastoma cells and that ERBB2 sensitizes medulloblastoma cells to 17-AAG by up-regulating basal MEK/ERK signaling. We further show that down-regulation of MEK1 activity markedly reduces the sensitivity of medulloblastoma, breast, and ovarian cancer cells to 17-AAG, whereas expression of a constitutively active MEK1 potentiates the activity of 17-AAG against these cells. Therefore, intact MEK/ERK signaling may be required for optimal 17AAG activity against a variety of tumor cell types. These data identify a new mechanism by which 17-AAG inhibits the proliferation of cancer cells. Defining the precise mode of action of these agents within specific tumor cell types will be crucial if this class of drugs is to be efficiently developed in the clinic.
Insights
ERBB2 enhances sensitivity to the HSP90 inhibitor 17-AAG in medulloblastoma by up-regulating MEK/ERK signaling, not AKT. This MEK/ERK pathway is crucial for 17-AAG
Area of Science:
- Oncology
- Molecular Biology
- Cancer Therapeutics
Background:
- ERBB2 (ErbB-2) overexpression is linked to poor outcomes in medulloblastoma.
- ERBB2 enhances breast cancer cell sensitivity to the HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG), via ERBB3/ERBB2 heterodimer disruption.
- The role of ERBB2 in medulloblastoma response to 17-AAG and its underlying mechanisms are not fully understood.
Purpose of the Study:
- To investigate the relationship between ERBB2 expression and 17-AAG sensitivity in medulloblastoma cells.
- To elucidate the signaling pathways mediating 17-AAG's anti-proliferative effects in medulloblastoma.
- To determine if ERBB2 influences 17-AAG efficacy through AKT or other signaling pathways.
Main Methods:
- Medulloblastoma cell lines with varying ERBB2 expression levels were treated with 17-AAG.
- Exogenous ERBB2 was overexpressed to study its effect on 17-AAG sensitivity and dimerization.
- Western blotting and pharmacological inhibitors were used to assess MEK/ERK and AKT signaling pathways.
Main Results:
- Medulloblastoma cell sensitivity to 17-AAG directly correlated with ERBB2 expression levels.
- Overexpression of ERBB2 induced homodimerization and increased 17-AAG sensitivity, independent of AKT1.
- 17-AAG treatment increased MEK/ERK signaling in a dose- and time-dependent manner, which was essential for proliferation inhibition.
Conclusions:
- ERBB2 sensitizes medulloblastoma cells to 17-AAG by up-regulating basal MEK/ERK signaling.
- Intact MEK/ERK signaling is required for optimal 17-AAG activity across various cancer types.
- Understanding ERBB2-mediated MEK/ERK pathway activation is crucial for developing 17-AAG as a clinical cancer therapy.
