Fibronectin, laminin, and FGF-2 induce subtype-specific dormancy in ER+ and TNBC breast cancer cell lines

Cancer cell dormancy is a critical, poorly understood mechanism allowing residual tumor cells to evade therapy and cause recurrence years after initial treatment. Current in vitro models often fail to accurately recapitulate this quiescent, drug-resistant state, hindering research into its regulation. Understanding the microenvironmental factors that trigger dormancy, especially in aggressive subtypes like triple-negative breast cancer (TNBC), is crucial for developing strategies to prevent relapse and overcome therapeutic resistance. This study addresses the gap by establishing robust in vitro models for dormancy induction.

Researchers investigated microenvironmental cues inducing dormancy in estrogen receptor-positive (MCF-7) and triple-negative (MDA-MB-231) breast cancer cell lines. Cells were cultured for 9 days under hierarchical conditions: (a) normoxia or true hypoxia, (b) dishes coated with fibronectin or laminin or none, and (c) presence or absence of 10 ng/mL basic fibroblast growth factor (FGF-2) added on day 0. Dormancy was characterized by immunofluorescence for increased p-p38 and decreased p-ERK expression, reduced Ki67 expression, elevated p21 and p27 levels, absence of senescence via β-galactosidase staining, and resistance to doxorubicin.

Specific microenvironmental cues induced distinct dormancy-like phenotypes in a subtype-specific manner. For MCF-7 cells, fibronectin or laminin coatings were sufficient to induce dormancy under hypoxic conditions. Interestingly, under normoxic conditions, the addition of 10 ng/mL FGF-2 to fibronectin (but not laminin) could also induce dormancy. The MDA-MB-231 (TNBC) cells showed different requirements: FGF-2 was essential with laminin to induce dormancy under hypoxic conditions, while FGF-2 plus fibronectin were unable to do so. Under normoxic conditions, laminin or fibronectin alone were sufficient to induce dormancy in MDA-MB-231 cells. All induced dormant cells exhibited characteristic markers including increased p-p38 and decreased p-ERK expression, reduced Ki67 expression, elevated p21 and p27 levels, and resistance to doxorubicin. These findings establish robust in vitro models. > These findings reveal subtype-specific differences in dormancy regulation, with ER+ and TNBC cells responding uniquely to combinations of oxygen levels, extracellular matrix components, and growth factors.