Characterization of Expression and Function of the Formins FHOD1, INF2, and DAAM1 in HER2-Positive Breast Cancer
Minna Peippo1,2, Maria Gardberg1, Pauliina Kronqvist1
1Department of Pathology, Turku University Hospital, University of Turku, Turku, Finland.
Purpose:
Human epidermal growth factor receptor 2 (HER2)-targeted therapies, such as trastuzumab, benefit patients with HER2-positive metastatic breast cancer; however, owing to traditional pathway activation or alternative signaling, resistance persists. Given the crucial role of the formin family in shaping the actin cytoskeleton during cancer progression, these proteins may function downstream of the HER2 signaling pathway. Our aim was to uncover the potential correlations between formins and HER2 expression using a combination of public databases, immunohistochemistry, and functional in vitro assays.
Methods:
Using online databases, we identified a negative prognostic correlation between specific formins mRNA expression in HER2-positive cancers. To validate these findings at the protein level, immunohistochemistry was performed on HER2 subtype breast cancer tumors to establish the links between staining patterns and clinical characteristics. We then knocked down individual or combined formins in MDA-MB-453 and SK-BR-3 cells and investigated their effects on wound healing, transwell migration, and proliferation. Furthermore, we investigated the effects of erb-b2 receptor tyrosine kinase 2 (ERBB2)/HER2 small interfering RNA (siRNA)-mediated knockdown on the PI3K/Akt and MEK/ERK1 pathways as well as on selected formins.
Results:
Our results revealed that correlations between INF2, FHOD1, and DAAM1 mRNA expression and ERBB2 in HER2-subtype breast cancer were associated with worse outcomes. Using immunohistochemistry, we found that high FHOD1 protein expression was linked to higher histological grades and was negatively correlated with estrogen and progesterone receptor positivity. Upon formins knockdown, we observed effects on wound healing and transwell migration, with a minimal impact on proliferation, which was evident through single and combined knockdowns in both cell lines. Notably, siRNA-mediated knockdown of HER2 affected FHOD1 and INF2 expression, along with the phosphorylated Akt/MAPK states.
Conclusion:
Our study highlights the roles of FHOD1 and INF2 as downstream effectors of the HER2/Akt and HER2/MAPK pathways, suggesting that they are potential therapeutic targets in HER2-positive breast cancer.
Insights
Formins FHOD1 and INF2 are downstream of HER2 signaling in breast cancer. Targeting these formins may improve outcomes for HER2-positive breast cancer patients.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- HER2-targeted therapies improve outcomes for HER2-positive metastatic breast cancer.
- Resistance to HER2-targeted therapies persists due to pathway activation or alternative signaling.
- Formins, involved in actin cytoskeleton regulation, may play a role downstream of HER2 signaling.
Purpose of the Study:
- To investigate the correlation between formin expression and HER2 expression in breast cancer.
- To explore the functional role of formins in HER2-positive breast cancer progression.
- To identify potential therapeutic targets in HER2-positive breast cancer.
Main Methods:
- Analysis of public databases for correlations between formin mRNA and HER2 expression.
- Immunohistochemistry to assess formin protein levels and clinical characteristics in HER2-positive breast cancer.
- In vitro assays including formin knockdown, wound healing, migration, and proliferation assays.
- siRNA-mediated knockdown of ERBB2/HER2 to investigate effects on signaling pathways and formin expression.
Main Results:
- Negative prognostic correlation between INF2, FHOD1, and DAAM1 mRNA expression and ERBB2 in HER2-subtype breast cancer, associated with worse outcomes.
- High FHOD1 protein expression linked to higher histological grades and negatively correlated with ER/PR positivity.
- Formin knockdown affected wound healing and migration, with minimal impact on proliferation.
- HER2 knockdown influenced FHOD1 and INF2 expression and Akt/MAPK signaling.
Conclusions:
- FHOD1 and INF2 function as downstream effectors of HER2/Akt and HER2/MAPK pathways.
- These formins represent potential therapeutic targets in HER2-positive breast cancer.
