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Sensitivity to targeted therapy differs between HER2-amplified breast cancer cells harboring kinase and helical domain mutations in PIK3CA.
- Source :
-
Breast cancer research : BCR [Breast Cancer Res] 2021 Aug 03; Vol. 23 (1), pp. 81. Date of Electronic Publication: 2021 Aug 03. - Publication Year :
- 2021
-
Abstract
- Background: HER2-amplified breast cancer is a clinically defined subtype of breast cancer for which there are multiple viable targeted therapies. Resistance to these targeted therapies is a common problem, but the mechanisms by which resistance occurs remain incompletely defined. One mechanism that has been proposed is through mutation of genes in the PI3-kinase pathway. Intracellular signaling from the HER2 pathway can occur through PI3-kinase, and mutations of the encoding gene PIK3CA are known to be oncogenic. Mutations in PIK3CA co-occur with HER2-amplification in ~ 20% of cases within the HER2-amplified subtype.<br />Methods: We generated isogenic knockin mutants of each PIK3CA hotspot mutation in HER2-amplified breast cancer cells using adeno-associated virus-mediated gene targeting. Isogenic clones were analyzed using a combinatorial drug screen to determine differential responses to HER2-targeted therapy. Western blot analysis and immunofluorescence uncovered unique intracellular signaling dynamics in cells resistant to HER2-targeted therapy. Subsequent combinatorial drug screens were used to explore neuregulin-1-mediated resistance to HER2-targeted therapy. Finally, results from in vitro experiments were extrapolated to publicly available datasets.<br />Results: Treatment with HER2-targeted therapy reveals that mutations in the kinase domain (H1047R) but not the helical domain (E545K) increase resistance to lapatinib. Mechanistically, sustained AKT signaling drives lapatinib resistance in cells with the kinase domain mutation, as demonstrated by staining for the intracellular product of PI3-kinase, PIP <subscript>3</subscript> . This resistance can be overcome by co-treatment with an inhibitor to the downstream kinase AKT. Additionally, knockout of the PIP <subscript>3</subscript> phosphatase, PTEN, phenocopies this result. We also show that neuregulin-1, a ligand for HER-family receptors, confers resistance to cells harboring either hotspot mutation and modulates response to combinatorial therapy. Finally, we show clinical evidence that the hotspot mutations have distinct expression profiles related to therapeutic resistance through analysis of TCGA and METABRIC data cohorts.<br />Conclusion: Our results demonstrate unique intracellular signaling differences depending on which mutation in PIK3CA the cell harbors. Only mutations in the kinase domain fully activate the PI3-kinase signaling pathway and maintain downstream signaling in the presence of HER2 inhibition. Moreover, we show there is potentially clinical importance in understanding both the PIK3CA mutational status and levels of neuregulin-1 expression in patients with HER2-amplified breast cancer treated with targeted therapy and that these problems warrant further pre-clinical and clinical testing.<br /> (© 2021. The Author(s).)
- Subjects :
- Breast Neoplasms drug therapy
Cell Line, Tumor
Drug Resistance, Neoplasm drug effects
Female
Humans
Lapatinib pharmacology
Molecular Targeted Therapy
Mutation
Neuregulin-1 metabolism
Neuregulin-1 pharmacology
PTEN Phosphohydrolase genetics
PTEN Phosphohydrolase metabolism
Phosphatidylinositol Phosphates metabolism
Protein Domains
Protein Kinase Inhibitors pharmacology
Proto-Oncogene Proteins c-akt antagonists & inhibitors
Proto-Oncogene Proteins c-akt metabolism
Signal Transduction
Breast Neoplasms genetics
Class I Phosphatidylinositol 3-Kinases genetics
Drug Resistance, Neoplasm genetics
Receptor, ErbB-2 antagonists & inhibitors
Receptor, ErbB-2 genetics
Subjects
Details
- Language :
- English
- ISSN :
- 1465-542X
- Volume :
- 23
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Breast cancer research : BCR
- Publication Type :
- Academic Journal
- Accession number :
- 34344439
- Full Text :
- https://doi.org/10.1186/s13058-021-01457-0