Understanding convergent signaling regulation in metastatic breast cancer cells using a bioengineered stem cell microenvironment

Aim: The convergence of tumorigenic and embryonic signaling pathways drives us to exploit the embryonic stem cell (ESC) microenvironment to restrict metastatic potential of cancer cells. We have previously demonstrated that bioengineered ESC microenvironments could restrict growth and metastatic potential of highly aggressive breast cancer cell (BCC). This study aims to further understand the regulation of convergent EGFR and canonical Wnt/β-catenin signaling pathway function in triple negative metastatic BCCs using the 3D in vitro ESC microenvironment created by encapsulating ESCs in alginate hydrogel microstrands. Methods: Co-culture with ESC-microstrands increased sensitivity to two chemotherapeutic drugs in metastatic BCCs. To test whether these changes were due to restored signaling pathway regulation in BCCs, we probed for changes in gene expression of key molecules related to the EGFR and canonical Wnt/β-catenin signaling pathways using quantitative reverse transcription polymerase chain reaction and Western blot analysis. Results: ESC-microstrands are able to alter the gene expression of highly aggressive BCCs at both mRNA and protein levels. These changes are indicative of a reversal of EGFR and canonical Wnt/β-catenin signaling pathway hyperactivation following co-culture. Increased NKD2 mRNA and protein expression coinciding with dual signaling pathway inhibition within co-cultured BCCs suggests that this reversal may be attributable to restored regulation of NKD2 within these pathways. Conclusion: ESC-microstrands are able to reverse oncogenic signaling pathway hyperactivation and restore signaling pathway regulation in metastatic BCCs. Further studies could provide insight into what role NKD2 up-regulation plays in BCC inhibition, leading to the development of a new targeted therapy for metastatic breast cancer.