Characterization of human ovarian carcinoma‐associated antigens defined by novel monoclonal antibodies with tumor‐restricted specificity

Abstract

Three new monoclonal antibodies (MAbs) (MOv16, MOv18 and MOv19) were raised against human ovarian carcinoma. To obtain more specific reagents than those produced so far, we adopted the following experimental approach which consisted of: the selection of a poorly differentiated ovarian carcinoma which was unreactive with all the MAb previously selected in our laboratory; and the application of a particular immunization protocol. The reactivity of the selected MAbs was studied by solid-phase RIA on live and fixed cells from tumor cell lines and by immunofluorescence on frozen sections from surgical specimens. The MAb MOv16 reacted with 60% of ovarian carcinomas as well as with a high percentage of other carcinomas and with some normal tissues. In contrast, MOv18 and MOv19 appeared to have restricted specificities for ovarian carcinomas and cystadenomas. Reactivity on other carcinomas was only observed in a few cases and no reactivity was found on non-epithelial tumors or normal tissues. Immunoprecipitation experiments indicated that MOv16 recognizes a 48-50-kDA protein, whereas MOv18 and MOv19 both identify a 38-40 kDA glycoprotein band. Cross-competition experiments, together with a double-determinant immunoradiometric assay which uses MOv18 as catcher and MOv19 as tracer, suggested that they recognize different epitopes carried by the same molecule. The affinity constants of MOv18 and MOv19 were estimated to be in the range of 10(8)-10(9) M-1. Taken together, the properties of these antibodies, their restricted ovarian tumor specificities and relative high affinity constants, suggest that they could represent promising tools for in vivo applications.

Downmodulation of caveolin-1 expression in human ovarian carcinoma is directly related to α-folate receptor overexpression

“…We found that aFR is constitutively expressed at high levels by ovarian carcinoma cells in vivo and in vitro (Miotti et al, 1987) and, in these cells (Alberti et al, 1990;Coney et al, 1991), aFR is only partially responsible for folate internalization . Antony, (1996) proposed that aFR might a ect cell proliferation independently of its involvement in folate internalization.…”

“…All of these tumors reportedly express medium-high levels of aFR (Miotti et al, 1987;To oli et al, 1997). Overexpression of aFR has been associated with tumor transformation and progression in experimental models and in ovarian cancer patients (Bottero et al, 1993; To oli et al, …”

Reversion of transformed phenotype in ovarian cancer cells by intracellular expression of anti folate receptor antibodies

“…5,6 Intrabodies are potentially suited for antiviral and antitumor gene therapy approaches, and preclinical and clinical studies have been promising. 7,8 One of the more specific tumor markers identified in our laboratory 9 is the a-isoform of the folate receptor (FR), a 38-40 kDa glycosyl-phosphatidyl-inositol-anchored molecule [10][11][12][13] that binds folic acid with high affinity. Detailed immunohistochemical analysis and evaluation of messenger RNA expression revealed moderate levels of FR expression on the cell surface of normal epithelial cells of kidney, lung and breast, and high levels in placental tissue.…”

“…Detailed immunohistochemical analysis and evaluation of messenger RNA expression revealed moderate levels of FR expression on the cell surface of normal epithelial cells of kidney, lung and breast, and high levels in placental tissue. 9,14-17 FR is not expressed in normal ovarian surface epithelium (OSE) 18 but is selectively overexpressed in the vast majority of nonmucinous ovarian carcinomas, 9,13 which arise from OSE. The association of FR expression with progression of the disease 13 has implicated this molecule in malignant transformation of this tissue.…”

“…18 Two monoclonal antibody/ies (Mab), MOV18 and MOV19, directed to nonoverlapping epitopes of FR, have been generated in our laboratories. 9 These Mab, and their chimeric or bispecific derivatives, were entered in several diagnostic and therapeutic trials with some relevant clinical responses. 20,21 To gain insight into the role of FR in ovarian cancer progression, we exploited the specificity of the anti FR MOV19 Mab to construct a single-chain (sc)Fv intrabody and tested the effects of functional downregulation of FR membrane expression on ovarian tumor cell proliferation and adhesion.…”