N. Gesmundo et al., EFFECT OF HYDROSTATIC-PRESSURE AND CHOLESTEROL DEPLETION ON THE EXPRESSION OF A TUMOR-ASSOCIATED ANTIGEN, European journal of biochemistry, 217(1), 1993, pp. 337-343
The molecular events related to the expression of three tumor-associat
ed epitopes, Ca-MOv17, Ca-MOv18 and Ca-MOv19 have been addressed. The
epitopes are carried by a 38-kDa glycoprotein (gp38), recently cloned
and identified as a human folate-binding protein. They were found to b
e coexpressed on the surface of the ovarian carcinoma cell line OVCA43
2, while they are not coordinately expressed on other adenocarcinoma c
ell lines (IGROV1, HT-29). This lack of coexpression was investigated
from a molecular point of view. We studied three carcinoma cell lines,
characterized by a different reactivity with the three relevant monoc
lonal antibodies MOv17, MOv18 and MOv19. The epitope expression was ex
amined after modifying the membrane properties by using hydrostatic pr
essure and/or the variation of cholesterol content. Measurement of the
expression after cell labelling by mAbs was performed by indirect imm
unofluorescence, using both fluorescence microscopy and flow cytometry
. At variance with HT-29 cells, treatment of ovarian carcinoma IGROV1
cells with hydrostatic pressure failed to exert any effect. On IGROV1,
instead, cholesterol depletion affected the expression Ca-MOv17, incr
easing, in the indirect immunofluorescence tests, the proportion of po
sitive cells from 0 to 66 +/- 9%. Moreover, restoring the cholesterol
content of the plasma membrane did not reverse the induced epitope exp
ression. In parallel, immunoprecipitation experiments confirmed that,
on IGROV1 surface, gp38 was recognized by all three mAbs. The data pre
sented suggest that in IGROV1 cells the selective lacking of the epito
pe expression is related to the physical state of the plasma membrane.
An explanation is provided by the model of membrane microdomains in w
hich epitope expression may be influenced by the cholesterol level of
different plasma membrane regions.