title: Abundant circulating microRNAs in breast cancer patients fluctuate considerably during neoadjuvant chemotherapy.
abstract: Previous studies have revealed the aberrant expression of a number of microRNAs (miRNA/miRs) in the blood circulation of patients with breast cancer (BC). The aim of the present study was to assess the effect of neoadjuvant chemotherapy on the levels of a panel of BC-associated miRNAs, which are at relatively low (let-7, miR-10b, miR-34, miR-155, miR-200c and miR-205) or abundant (miR-21, miR-195 and miR-221) levels in the circulation. Patients with primary operable or locally advanced BC were enrolled in the study. The plasma levels of the miRNAs at baseline and at the fourth cycle of treatment were compared. Patients with stage II disease exhibited higher basal miRNAs levels than those with higher stages. The difference was most evident for miR-155 and miR-21 (P=0.05). From the initial to the fourth cycle of chemotherapy, the miRNA levels changed substantially. In samples in which the miRNA levels generally declined, a marked decrease (≤15,500-fold) was evident for the abundant miRNAs. Notably, the occurrence of a decrease in miRNA levels was more frequent in patients with smaller tumor sizes (P<0.05 for miR-21 and miR-195). This proof-of-concept study provides evidence that highly expressed miRNAs are affected most frequently by chemotherapy, particularly in patients with early stage tumors. This information may be valuable in assessing the response of the patients to therapy.
authors.affiliation: Department of Basic Oncology, Oncology Institute, Istanbul University, Istanbul 34093, Turkey.
authors.forename: Ugur
authors.initials: U
authors.lastname: Gezer
authors.affiliation: Department of Clinical Oncology, Oncology Institute, Istanbul University, Istanbul 34093, Turkey.
authors.forename: Serkan
authors.initials: S
authors.lastname: Keskin
authors.affiliation: Department of General Surgery, Istanbul Medical Faculty, Istanbul University, Istanbul 34093, Turkey.
authors.forename: Abdullah
authors.initials: A
authors.lastname: Iğci
authors.affiliation: Department of General Surgery, Istanbul Medical Faculty, Istanbul University, Istanbul 34093, Turkey.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Tükenmez
authors.affiliation: Department of Basic Oncology, Oncology Institute, Istanbul University, Istanbul 34093, Turkey.
authors.forename: Duygu
authors.initials: D
authors.lastname: Tiryakioğlu
authors.affiliation: Department of Basic Oncology, Oncology Institute, Istanbul University, Istanbul 34093, Turkey.
authors.forename: Merve
authors.initials: M
authors.lastname: Cetinkaya
authors.affiliation: Department of Clinical Oncology, Oncology Institute, Istanbul University, Istanbul 34093, Turkey.
authors.forename: Rian
authors.initials: R
authors.lastname: Dişci
authors.affiliation: Department of Basic Oncology, Oncology Institute, Istanbul University, Istanbul 34093, Turkey.
authors.forename: Nejat
authors.initials: N
authors.lastname: Dalay
authors.affiliation: Department of Clinical Oncology, Oncology Institute, Istanbul University, Istanbul 34093, Turkey.
authors.forename: Yeşim
authors.initials: Y
authors.lastname: Eralp
keywords: breast cancer; circulating microRNAs; neoadjuvant chemotherapy