4t1 luc2

4T1⁵¹ (CRL-2539™, ATCC) and 4T1luc2 (BW124087, Perkin Elmer, Waltham, MA) were purchased; 4T1luc-D6 clone was described previously^{16 (link)}. Cells were cultured and passaged as recommended by the manufacturers. Both cell lines express luciferase encoded by luc2 gene (http://www.perkinelmer.com.cn/CMSResources/Images/46-176379PST-WMIC2015-Using-brighter-red-shifted-luciferase-in-vivo-tumor-bioluminescence-imaging.pdf) Luc2 is a synthetic gene for “yellow” firefly luciferase engineered to improve mammalian expression through codon optimization (Promega; https://se.promega.com/products/reporter-assays-and-transfection/reporter-vectors-and-cell-lines/pgl4-luciferase-reporter-vectors/promoterless-firefly-luciferase-vectors/). The time course of the proliferation of the parental 4T1, and 4T1luc2D6 and 4T1luc2 (PerkinElmer) clones was determined using Nikon Biostation CT (Nikon, Japan).

Carbon-coated magnetic (CCM) beads were purchased from Turbo beads (Zurich, Switzerland). Information about the synthesis and chemistry of the beads can be found elsewhere [20 (link)]. Penicillin-streptomycin was purchased from Gibco Life Technologies (Carlsbad, CA, USA). Sodium chloride (NaCl), magnesium chloride (MgCl₂), phosphate-buffered saline pH 7.4 (PBS), tris(hydroxymethyl)aminomethane (tris-base), boric acid, ethylenediaminetetraacetic acid (EDTA) disodium dihydrate, sodium azide, and hydrochloric acid were purchased from Sigma-Aldrich (St. Louis, MO, USA; https://www.sigmaaldrich.com/united-states.html (accessed on 10 February 2021)). The size exclusion chromatographic column was obtained from Izon Science Ltd. (Lyon, France). Amicon Ultra Centrifugal Filter (0.5 mL) was supplied from EMD Millipore (Sigma, Burlington, MA, USA; https://www.merckmillipore.com (accessed on 10 May 2020)). DNA purification kit (Qiagen, Hilden, Germany), RT2 first strand kit (Qiagen, cat No 330401), and purified labeled and unlabeled oligonucleotides were purchased from Metabion International (Planegg, Germany; http://www.metabion.com (accessed on 10 May 2021)), as shown in Table 1 and Table 2. Luciferase-expressing 4T1 murine breast cancer cells (4T1-Luc2) were purchased from PerkinElmer and cultured as reported previously [21 (link)].

The human breast carcinoma cell line MDA-MB-231 (ECACC, Salisbury, UK), its brain metastatic variant MDA-MB-231BR, bone metastatic variant MDA-MB-231SCP2, and murine TNBC cell line 4T1/luc2 (PerkinElmer, Waltham, MA) were cultured in RPMI-1640 (Thermo Fisher Scientific Inc., Waltham, MA) with 10% fetal bovine serum. MDA-MB-231BR and MDA-MB-231SCP2 were kind gifts from Dr. Patricia Steeg and Dr. Joan Massagué, respectively. Contamination by Mycoplasma or fungi was routinely checked, and the cells were treated or discarded when necessary; only uncontaminated cells were used. All cells were maintained under a humidified atmosphere of 5% CO₂ at 37 °C.