Transformation-associated alterations in interactions between pre-B cells and fibronectin

Area of Science:

• Immunology
• Cell Biology
• Hematopoiesis

Background:

• Marrow stromal cells produce growth factors stimulating pre-B cell proliferation.
• Close contact between stromal and pre-B cells enhances the pre-B cell response.

Purpose of the Study:

• To investigate the role of fibronectin (FN) binding in pre-B cell proliferation and stromal cell interaction.
• To understand the mechanisms behind leukemic pre-B cell outgrowth and stromal independence.

Main Methods:

• Serum-free adherence assays to test pre-B cell binding to fibronectin (FN).
• Co-culture experiments with stromal cell lines (M2-10B4) and pre-B cells, using anti-FN receptor antibodies.
• Analysis of cell surface molecules and mRNA expression for FN receptors (VLA).

Main Results:

• Freshly isolated and immortalized nontumorigenic pre-B cells adhere to FN via an RGD site, a function lost upon differentiation into B cells.
• Anti-FN receptor antibodies significantly reduced proliferation of nontumorigenic pre-B cells co-cultured with stromal cells.
• Tumorigenic, stromal-independent pre-B cell lines did not bind to FN, and anti-FN receptor antibodies had minimal effect on their proliferation.
• Alterations in FN receptor (VLA) expression, specifically increased alpha chains and decreased beta 1 chain in some cases, were observed in tumorigenic pre-B cells.

Conclusions:

• Pre-B cell attachment to fibronectin (FN) on stromal cells is a key mechanism for stromal-supported proliferation.
• Loss of FN binding due to altered FN receptor expression may contribute to the development of stromal-independent, autocrine leukemic pre-B cells.