Circulating tumor cells and vitamin D in primary breast cancer.

Abstract

e12558 Background: Circulating tumor cells (CTCs) contributing to the metastatic cascade and represent an independent survival predictor in breast cancer (BC) patients. Vitamin D has pleiotropic effects and its low concentrations are associated with infections, cancer, but also other pathologic conditions. The aim of this study was to assess plasma vitamin D level in primary BC patients in relation to CTCs. Methods: This study included 91 non-metastatic breast cancer patients (stage I-III) with plasma samples available in the biobank of the National Cancer Institute in Slovakia. Blood samples for the analyses were drawn at the time of surgery. Peripheral blood mononuclear cells (PBMCs) were depleted of hematopoetic cells using RossetteSepTM negative selection kit. RNA extracted from CD45-depleted PBMCs was analyzed for the expression of transcription factors (TWIST1, SNAIL1, SLUG, ZEB1) that induce epithelial-to-mesenchymal transcription (EMT-TF) and epithelial ( CK19) gene transcripts using qRT-PCR. Patient samples with higher epithelial and/or mesenchymal gene transcripts than those of healthy donors (n = 60) were considered CTCs positive. Total 25-OH vitamin D was measured in plasma using ELISA. Results: CTCs were detected in 30 (33%) patients, 14 (15.4%) patients had detectable CTCs with epithelial characteristics, 13 (14.3%) patients had CTCs with an EMT phenotype, while peripheral blood of 3 (3.3%) patients exhibit both CTCs subtypes. Patients with detectable CTCs in peripheral blood had significantly lower vitamin D concentrations in comparison to patients without detectable CTCs (mean ± SD) 8.50 ± 3.89 µg/L for CTCs positive vs. 9.69 ± 3.49 µg/L for CTCs negative patients respectively, P = 0.03). There was no association between plasma vitamin D and other patient/tumor characteristics. At a median follow-up of 96.5 months (range: 8.4 - 109.4 months), 28 patients (30.8%) had experienced a progression and 24 patients (26.4%) had died. Patients with vitamin D above median had better overall survival (HR = 0.36, 95%CI 0.16 – 0.80, P = 0.017) compared to patients below median vitamin D. Conclusions: According to our knowledge, this is the first report of an association between plasma vitamin D concentrations and CTCs in primary breast cancer patients. We suggest that vitamin D could play a direct role in tumor dissemination and its supplementation might affect metastatic cascade. Alternatively, decreased vitamin D could be a consequence and hence a biomarker of a more invasive disease. Animal experiments and interventional studies are needed to prove the causality of the observed association.