Inhibition of osteotropic breast cancer cell motility by zoledronic acid in a 3D spheroid culture

Abstract

Conventional cell culture techniques grow cells in a two‐dimensional (2D) format on compatible surfaces, but cells do not grow like this in vivo. A fast‐emerging alternative is three‐dimensional (3D) cell culture, which encourages cells to work together while suspended in a matrix rather than relying on adhesion to a treated surface. Most studies utilize a commercially available, industry standard recombinant basement membrane substitute—Matrigel®; however, this is proprietary and expensive. For these studies, the objective was to refine an alternative to commercial matrices for use as a suspension media. Our efforts focused on economical Methocel™ (methylcellulose dissolved into basal growth media) in combination with rat tail collagen Type I. Methocel promoted the formation of spheroids among several cell lines including three isogenic variants of a triple‐negative metastatic breast cancer cell line, MDA‐MB‐231, with differing organotropic propensity and difficult to grow in spheroid culture. While not required for all cell lines, the addition of Type I collagen greatly increased the efficacy of spheroid formation among all cell lines tested. Once harvested, spheroids were suspended within a Methocel‐collagen gel. Cultures were treated with various chemotherapy drugs including bisphosphonates (ibandronic and zoledronic acids) and docetaxol. The effectiveness of these drugs to inhibit migration through a surrogate extracellular matrix was determined by the amount of invasion as measured by distance migrated from the spheroid periphery. Osteotropic cells (MDA‐MB‐231Bo) showed a high degree of translocation through the matrix compared to MDA‐MB‐231 control cells but were dramatically more affected by the cytostatic action of zoledronic acid, a drug know to suppress skeletal‐related events. Furthermore, using RT‐PCR to evaluate canonical cell adhesion molecules including the a2b1 integrin, Cadherins, Twist, and Snail, we see a time‐dependent change in gene expression among the three MDA‐MB‐231 variants when grown in the presence of chemotherapeutic drugs. Taken together, our results demonstrate a simple, cost‐effective system that provides an in vivo‐like microenvironment to study gene expression alterations in tumor progression and metastasis.Support or Funding InformationFresno State faculty‐student scholarly research award.