Breast cancer is the second most common
cancer in the world based on incidence, reaching more than 2 million new cases in 2018, while continuing to increase. Invasive
ductal carcinoma is the most common type of this
cancer, making up approximately 70-80% of all
breast cancer diagnoses. In particular, the type of
breast cancer overexpressing
human epidermal growth factor receptor 2 (HER2) has potential of strong proliferation, migration and invasion and early treatment is necessary. The authors identified and studied a single patient displaying complete therapeutic resistance to monoclonal anti-HER2 antibody
therapy,
chemotherapy and
radiotherapy. A patient who exhibited resistance to postoperative adjuvant
therapy after
mastectomy was selected from HER2-positive
breast cancer, and this patient had the grade of T4bN2aM0, Stage IIIB. The patient samples, blood serum and
cancer tissue, were analyzed by metabolome and immunostaining technique, respectively. The characteristics of peripheral blood serum and solid
tumor were investigated, aiming to find new serum
biomarker(s) using the metabolomics technique. A correlation between the appearance of HER2-positive
cancer tissue and serum concentration of the
sphingomyelin family was found. In addition, HER2-positive
tumor tissue in both the primary and recurrent
cancer express the
sphingomyelinase. These results suggest that
sphingomyelins from this
cancer tissue leads to
therapy resistance, induction of invasion and strong proliferation.