Tissue structure, nuclear organization, and gene expression in normal and malignant breast

Area of Science:

• Cellular Biology
• Molecular Biology
• Tissue Engineering

Background:

• Cells possess identical genetic information, yet exhibit selective gene expression within tissues.
• Gene expression is regulated by a complex interplay of physical and biochemical signals.
• Cellular decisions (proliferation, differentiation, apoptosis) depend on their microenvironment.

Purpose of the Study:

• To investigate the hypothesis that the three-dimensional tissue, not the genome or cell alone, is the fundamental unit of function.
• To explore the bidirectional communication between the cellular microenvironment and the nucleus.
• To understand how tissue structure influences selective gene expression and malignancy.

Main Methods:

• Utilized human and mouse mammary cell lines in "designer microenvironments".
• Employed a three-dimensional (3D) culture assay with reconstituted basement membrane.
• Analyzed extracellular matrix-receptor (integrin) signaling and epidermal growth factor receptor (EGFR) pathways.

Main Results:

• 3D cultures distinguished normal (growth-arrested, organized acini) from malignant (uncontrolled growth) breast cells.
• Correcting extracellular matrix-receptor signaling reverted the malignant phenotype in breast tumor cells.
• Reciprocal integration of beta1 integrin and EGFR signaling observed in 3D cultures, but not in 2D monolayers.

Conclusions:

• Tissue structure is dominant over the genome in regulating cellular phenotype and gene expression.
• Nuclear organization can modulate cellular and tissue phenotype, influencing gene expression.
• Tissue structural integrity is critical for preventing malignant progression, even with genetic mutations.