STARD3: A New Biomarker in HER2-Positive Breast Cancer

Area of Science:

• Oncology
• Molecular Biology
• Biomarker Discovery

Background:

• Pathological complete response (pCR) is a key prognostic factor in HER2-positive breast cancer following neoadjuvant systemic treatment (NST).
• HER2 gene amplification in breast cancer often involves co-amplification and co-expression of other genes, including STARD3.
• The predictive role of STARD3 expression as a biomarker for NST response has not been previously investigated.

Purpose of the Study:

• To evaluate the predictive value of STARD3 protein expression for pathological response to NST in HER2-positive breast cancer.
• To assess the prognostic significance of STARD3 expression in this patient cohort.

Main Methods:

• Retrospective analysis of 112 non-metastatic HER2-positive breast cancer patients treated with NST and surgery (2007-2020).
• Development of an immunohistochemistry assay to assess STARD3 protein expression and subcellular localization.
• Scoring of STARD3 positivity based on granular intracellular signal pattern, indicative of endosomal localization.

Main Results:

• Half of the patients achieved pCR; STARD3 positivity was observed in 86.6% of cases.
• STARD3 positivity was significantly associated with pCR in univariate (p=0.013) and adjusted analyses (p=0.044).
• High sensitivity (96%) and negative predictive value (87%) for pCR prediction; similar survivals between STARD3 positive and negative groups.

Conclusions:

• STARD3-negative status in HER2-positive breast cancer is linked to a lower likelihood of achieving pCR after NST.
• Assessing STARD3 overexpression on initial biopsies can provide valuable information for managing patients with HER2-positive breast cancer, particularly those with a high probability of no pathological response.
• This finding supports STARD3 as a potential predictive biomarker for NST efficacy in HER2-positive breast cancer.