Abstract P6-10-20: Ductal carcinoma in situ (DCIS) of the breast: miRNA deregulation correlates with the Oncotype DX risk score

Background: Ductal carcinoma in situ (DCIS) is considered a non-obligate precursor of invasive breast cancer (IBC). It is estimated that 5-14% of women diagnosed with DCIS experience an ipsilateral IBC. Current clinical criteria do not discriminate well between women with DCIS who will and those who will not develop ipsilateral IBC or a DCIS recurrence. The Oncotype DX DCIS assay (12 genes) was derived from a multigene expression array (Oncotype DX, 21 genes), and includes 5 proliferation genes, PGR, GSTM1, and 5 reference genes. This assay has been shown to predict risk of subsequent ipsilateral IBC and DCIS, and is used by clinicians to evaluate both the risk of local recurrence and need for radiation therapy. Since abnormal expression of microRNAs (miRNAs) is thought to contribute to the development of IBC, and that very few studies have evaluated miRNA expression deregulation in DCIS lesions, we sought to determine if specific miRNA expression changes may help identify DCIS lesions with different Oncotype DX DCIS scores. Methods: For this study, we selected archived specimens from 52 women diagnosed with DCIS between 2012 and 2018, whose DCIS lesions were tested with the Oncotype DX DCIS assay (low (n=35), intermediate (n=11), high (n=6) risk scores). Total RNA was extracted by macrodissection of the DCIS lesions. MiRNA expression differences between DCIS lesions were evaluated using small-RNA next-generation sequencing. Quantitative PCR validations were performed using Taqman miRNA assays on the top 15 differentially expressed miRNAs Results: Small-RNA expression data obtained by next-generation sequencing of 43 DCIS RNA specimens identified miRNAs differentially expressed between the risk score groups. Fifteen differentially expressed miRNAs were selected for their association based on Oncotype DX DCIS score differences (miR-142-3p, miR-142-5p, miR-744, miR-155, miR-30c, miR-150, miR-146a, miR-190b, miR-135b, miR-193b) or on age of the patients (miR-19b, miR-19a, miR-135a, miR-132). QPCR validation of these 15 miRNAs, using RNA from 30 DCIS lesions with known Oncotypes DX DCIS scores, of which 21 were samples that had been sequenced (low (n=8), intermediate (n=9), and high (n=4)), and 9 were not sequenced (low (n=7), intermediate (n=1), high (n=1)) and identified 5 miRNAs (miR-135a (p= Citation Format: Olivier Loudig, Iddo Ben-Dov, Christina Liu, Miglena Komforti, Susan Fineberg. Ductal carcinoma in situ (DCIS) of the breast: miRNA deregulation correlates with the Oncotype DX risk score [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-10-20.