Transformation-associated alterations in interactions between pre-B cells and fibronectin.
Marrow stromal elements produce as yet uncharacterized soluble growth factors that can stimulate the proliferation of murine pre-B cells, although close contact between these two cell types appears to ensure a better pre-B cell response. We have now shown that freshly isolated normal pre-B cells (ie, the B220+, surface mu- fraction of adult mouse bone marrow) adhere to fibronectin (FN) via an RGD cell-attachment site, as shown in a serum-free adherence assay, and they lose this functional ability on differentiation in vivo into B cells (ie, the B220+, surface mu+ fraction). Similarly, cells from an immortalized but stromal cell-dependent and nontumorigenic murine pre-B cell line originally derived from a Whitlock-Witte culture were also found to adhere to fibronectin (FN) via an RGD cell-attachment site. Moreover, in the presence of anti-FN receptor antibodies, the ability of this immortalized pre-B cell line to proliferate when co-cultured with a supportive stromal cell line (M2-10B4 cells) was markedly reduced (down to 30% of control). This suggests that pre-B cell attachment to FN on stromal cells may be an important component of the mechanism by which stromal cells stimulate normal pre-B cell proliferation and one that is no longer operative to control their more differentiated progeny. Two differently transformed pre-B cell lines, both of which are autocrine, stromal-independent, tumorigenic in vivo, and partially or completely differentiation-arrested at a very early stage of pre-B cell development, did not bind to FN. In addition, anti-FN receptor antibodies were much less effective in diminishing the ability of these tumorigenic pre-B cells to respond to M2-10B4 cell stimulation, which could still be demonstrated when the tumorigenic pre-B cells were co-cultured with M2-10B4 cells at a sufficiently low cell density. Analysis of cell surface molecules immunoprecipitated from both the nontumorigenic and tumorigenic pre-B cell lines by an anti-FN receptor antibody showed an increase in very late antigen (VLA) alpha chain(s) in both tumorigenic pre-B cell lines and a decrease in the beta 1 chain in one. Interestingly, all of the pre-B cell lines expressed similar amounts of messenger RNA for the beta 1 chain of the FN receptor. These results suggest that alteration of FN receptor expression on pre-B cells may represent a mechanism contributing to the outgrowth of leukemic pre-B cells with an autocrine phenotype and capable of stromal cell-independent, autonomous growth.
Lemoine
F M
FM
Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, Canada.
Dedhar
S
S
Lima
G M
GM
Eaves
C J
CJ
D000011:Abelson murine leukemia virus; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001854:Bone Marrow Cells; D002448:Cell Adhesion; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D002472:Cell Transformation, Viral; D005353:Fibronectins / Q000378:metabolism*; D015870:Gene Expression; D006412:Hematopoietic Stem Cells / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008970:Molecular Weight; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000032:analysis; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic / Q000235:genetics / Q000276:immunology / Q000502:physiology
D000906:Antibodies; D005353:Fibronectins; D012333:RNA, Messenger; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic