ATTACHMENT, INVASION, CHEMOTAXIS, AND PROTEINASE EXPRESSION OF B16-BL6 MELANOMA-CELLS EXHIBITING A LOW METASTATIC PHENOTYPE AFTER EXPOSURE TO DIETARY RESTRICTION OF TYROSINE AND PHENYLALANINE
Ce. Uhlenkott et al., ATTACHMENT, INVASION, CHEMOTAXIS, AND PROTEINASE EXPRESSION OF B16-BL6 MELANOMA-CELLS EXHIBITING A LOW METASTATIC PHENOTYPE AFTER EXPOSURE TO DIETARY RESTRICTION OF TYROSINE AND PHENYLALANINE, Clinical & experimental metastasis, 14(2), 1996, pp. 125-137
We previously reported that low levels of tyrosine (Tyr) and phenylala
nine (Phe) alter the metastatic phenotype of B16-BL6 (BL6) murine mela
noma and select for tumor cell populations with decreased lung coloniz
ing ability. To more specifically characterize the effects of Tyr and
Phe restriction on the malignant phenotype of BL6, we investigated in
vitro attachment, invasion, proteinase expression, and chemotaxis of h
igh and low metastatic BL6 variants. High metastatic variant cells wer
e isolated from subcutaneous tumors of mice fed a nutritionally comple
te diet (ND cells) and low metastatic variant cells were isolated from
mice fed a diet restricted in Tyr and Phe (LTP cells). Results indica
te that attachment to reconstituted basement membrane (Matrigel(TM)) w
as significantly reduced in LTP cells as compared to ND cells. Attachm
ent to collagen IV, laminin, and fibronectin were similar between the
two variants. Invasion through Matrigel(TM) and growth factor-reduced
Matrigel(TM) were significantly decreased in LTP cells as compared to
ND cells. Zymography revealed the presence of M(r). 92 000 and M(r) 72
000 progelatinases, tissue plasminogen activator, and urokinase plasm
inogen activator in the conditioned medium of both variants; however,
there were no differences in activity of these secreted proteinases be
tween the two variants. Growth of the variants on growth factor-reduce
d Matrigel(TM) similarly induced expression of the M(r) 92 000 progela
tinase. The variants exhibited similar chemotactic responses toward la
minin. However, the chemotactic response toward fibronectin by LTP cel
ls was significantly increased. MFR5, a monoclonal antibody which sele
ctively blocks function of the alpha(5) chain of the alpha(5) beta(1)
integrin, VLA-5, decreased the chemotactic response toward fibronectin
of ND cells by 37%; the chemotactic response by LTP cells was reduced
by 49%. This effect was specific for fibronectin-mediated chemotaxis
since the chemotaxis toward laminin and invasion through Matrigel(TM)
were not altered by the presence of MFR5. The surface expression of VL
A-5 was significantly increased in LTP cells as compared to ND cells b
y flow cytometric analysis. These observations suggest that limitation
of Tyr and Phe either directly modifies BL6 or selects for subpopulat
ions with altered in vitro invasion, chemotaxis, and integrin expressi
on.