Glucose-limiting conditions induce an invasive population of MDA-MB-231 breast cancer cells with increased connexin 43 expression and membrane localization

Abstract

Gap junctional intercellular communication (GJIC) is a homeostatic process mediated by membrane channels composed of a protein family known as connexins. Alterations to channel activity can modulate suppression or facilitation of cancer progression. These varying roles are influenced by the cancer cell genetic profile and the context-dependent mechanisms of a dynamic extracellular environment that encompasses fluctuations to nutrient availability. To better explore the effects of altered cellular metabolism on GJIC in breast cancer, we generated a derivative of the triple-negative breast cancer cell line MDA-MB-231 optimized for growth in low-glucose. Reduced availability of glucose is commonly encountered during tumor development and leads to metabolic reprogramming in cancer cells. MDA-MB-231 low-glucose adapted cells exhibited a larger size with improved cell–cell contact and upregulation of cadherin-11. Additionally, increased protein levels of connexin 43 and greater plasma membrane localization were observed with a corresponding improvement in GJIC activity compared to the parental cell line. Since GJIC has been shown to affect cellular invasion in multiple cancer cell types, we evaluated the invasive qualities of these cells using multiple three-dimensional Matrigel growth models. Results of these experiments demonstrated a significantly more invasive phenotype. Moreover, a decrease in invasion was noted when GJIC was inhibited. Our results indicate a potential response of triple-negative breast cancer cells to reduced glucose availability that results in changes to GJIC and invasiveness. Delineation of this relationship may help elucidate mechanisms by which altered cancer cell metabolism affects GJIC and how cancer cells respond to nutrient availability in this regard.

Macro- and micro-nutrient–based multiplex stress conditions modulate in vitro tumorigenesis and aggressive behavior of breast cancer spheroids

“…Though the expression of integrin β1 does not alter much in MCF7 cells under combined stress, its altered trafficking to the membrane might play a critical role [46]. On the other hand, the complete inability of stressed MDA MB 231 cells to form spheroid even with ECM can be explained by the absence of E-cadherin, N-cadherin, and Claudin 1 [47].…”

Connexins and Glucose Metabolism in Cancer

“…A study from a different perspective evaluated the effects of reduced glucose availability on metastatic breast cancer cells. Using the MDA-MB-231 triple-negative breast cancer cell line, long-term glucose limitations induced the emergence of an adapted population with altered morphology and a significantly increased invasive capacity through Matrigel [ 224 ]. These cells matched the proliferative capacity and viability of non-adapted cells grown in higher glucose concentrations.…”

“…( D ) Adaptation to reduced glucose availability can lead to increased connexin expression, membrane localization and GJIC with associated increases in phenotypic qualities such as survival and invasion, Refs. [ 224 , 225 ]. Abbreviations: Glu, glucose; HCO 3 − , bicarbonate; Lac, lactate; CAC, citric acid cycle.…”