FTY720 in resistant human epidermal growth factor receptor 2-positive breast cancer

Area of Science:

• Oncology
• Pharmacology

Background:

• Human epidermal growth factor receptor 2 (HER2)-positive breast cancer prognosis has improved, but resistance to anti-HER2 therapies like trastuzumab remains a challenge.
• FTY720, a sphingosine-1-phosphate receptor modulator approved for multiple sclerosis, has demonstrated anti-cancer properties.
• The PIK3CA mutation is common in HER2-positive breast cancer and can contribute to treatment resistance.

Purpose of the Study:

• To evaluate the efficacy of FTY720 in overcoming trastuzumab resistance in HER2-positive breast cancer cells.
• To investigate the underlying mechanisms of FTY720's action in resistant cancer models.
• To assess the in vivo efficacy of FTY720 in a relevant preclinical model.

Main Methods:

• Cell viability was assessed using WST-1 assays and cytotoxicity was measured with LDH assays.
• Protein expression was analyzed via Western blot.
• Apoptosis was quantified using annexin V staining and TUNEL assays with flow cytometry.
• In vivo efficacy was evaluated in a HCC1954 xenograft mouse model.

Main Results:

• FTY720 demonstrated efficacy against trastuzumab-resistant HER2-positive breast cancer cell lines, including those with PIK3CA mutations.
• FTY720 treatment led to significantly reduced tumor growth in the HCC1954 xenograft mouse model compared to controls.
• Morphological changes, apoptosis induction, and specific protein expression alterations were observed following FTY720 treatment.

Conclusions:

• FTY720 represents a potential therapeutic strategy to overcome trastuzumab resistance in HER2-positive breast cancer.
• Combination therapy with FTY720 and trastuzumab may offer enhanced efficacy in vitro and in vivo.
• Further investigation into FTY720's mechanism and clinical application is warranted for HER2-positive breast cancer treatment.