Preclinical and neoadjuvant trial data suggest that PIK3CA alterations confer resistance to HER2-targeted therapy and are associated with lower pathological complete response (pCR) rate in HER2-positive breast cancer.
Using this method, we assessed the clinical impact of changes in the frequency and topology of PIK3CA mutation and HER2 (ERBB2) amplification within HER2-positive breast cancer during neoadjuvant therapy.
Impact of somatic PI3K pathway and ERBB family mutations on pathological complete response (pCR) in HER2-positive breast cancer patients who received neoadjuvant HER2-targeted therapies.
However, about half of individuals with HER2-positive breast cancer do not respond to trastuzumab treatment because of various resistance mechanisms, including but not limited to: 1) shedding of the HER2 extracellular domain, 2) steric hindrance ( e.g., MUC4 and MUC1), 3) parallel pathway activation (this is the general mechanism cited in the quote above), 4) perturbation of downstream signaling events ( e.g., PTEN loss or PIK3CA mutation), and 5) immunologic mechanisms (such as FcR polymorphisms).
A preclinical evaluation of the PI3K alpha/delta dominant inhibitor BAY 80-6946 in HER2-positive breast cancer models with acquired resistance to the HER2-targeted therapies trastuzumab and lapatinib.
PIK3CA mutations are associated with reduced pathological complete response rates in primary HER2-positive breast cancer: pooled analysis of 967 patients from five prospective trials investigating lapatinib and trastuzumab.
Therefore, we conducted a meta-analysis to assess the association between PTEN loss, PIK3CA mutation and the efficacy of trastuzumab-based treatment in HER2-positive breast cancer patients.
This study investigated the association between PIK3CA genotype and pathologic complete response (pCR) rates in human epidermal growth factor receptor 2 (HER2)-positive breast cancer treated with either dual or single anti-HER2 treatment in addition to neoadjuvant chemotherapy.
<i>ERBB</i> gene family mutations, which are present in 7% of our HER2+ breast cancer cohort, may have the potential to alter cellular behaviour and the efficacy of HER- and PI3K-inhibition.
Combination inhibition of PI3K and mTORC1 yields durable remissions in mice bearing orthotopic patient-derived xenografts of HER2-positive breast cancer brain metastases.
A panel of HER2-positive breast cancer cells were profiled for mutational status and also for anti-proliferative response to refametinib alone and in combination with the PI3K inhibitor (PI3Ki) copanlisib and the HER2-targeted therapies trastuzumab and lapatinib.
The Neoadjuvant PI3K inhibition in HER2 OverExpressing Breast cancEr (NeoPHOEBE) trial evaluated the efficacy and safety of buparlisib, a pan-phosphatidylinositol 3-kinase (PI3K) inhibitor, plus trastuzumab and paclitaxel as neoadjuvant treatment for human epidermal growth factor receptor-2 positive (HER2+) breast cancer.
These results demonstrate that a PI3K p110α-isoform-selective inhibitor is an effective adjunct to trastuzumab in the treatment of HER2-positive breast cancer.
Human epidermal growth factor receptor 2 (HER2)-positive breast cancer is treated with HER2-targeted agents, such as trastuzumab and lapatinib, that suppress signaling by phosphatidylinositol 3-kinase (PI3K)-Akt and MAPK pathways.
Collectively, our results demonstrate that intracellular Cl<sup>-</sup> regulation by ANO1/ClC-3 participates in HER2 transcription, mediating the PI3K/AKT/mTOR and/or STAT3 signaling pathway(s) in HER2-positive breast cancer cells, and support the potential of ANO1/ClC-3 blockers as therapeutic options for patients with resistance to anti-HER2 therapies.
<b>Conclusion:</b> The trastuzumab/AT-101 combination may be a good candidate for patients with trastuzumab-resistant Her2-positive breast cancer and inhibition of the PI3K/AKT pathway may be one of the underlying mechanisms.