Six human
ovarian cancer cell lines and samples of
ascites cells isolated from 27 patients with stage III or IV ovarian papillary
serous cystadenocarcinoma were studied individually to test whether recombinant human
Mullerian inhibiting substance (rhMIS) acts via its receptor. To do these experiments, we scaled up production of rhMIS and labeled it successfully with
biotin for binding studies, cloned the human
MIS type II receptor for
mRNA detection, and raised
antibodies to an extracellular domain peptide for
protein detection. These probes were first tested on the human
ovarian cancer cell lines and then applied to primary ovarian
ascites cells. rhMIS inhibited colony growth of five of six cell lines that expressed the human
MIS type II receptor mRNA by Northern analysis while not inhibiting receptor-negative COS cells. Flow cytometry performed on MIS-sensitive
ovarian cancer cell lines demonstrated specific and saturable binding of rhMIS (Kd = 10.2 nM).
Ascites cells from 15 of 27 or 56% of patients tested bound biotinylated MIS (MIS-
biotin) and, of the 11 that grew in soft
agarose, 9 of 11 or 82% showed statistically significant inhibition of colony formation. Of the 15 patients who bound biotinylated MIS,
mRNA was available for analysis from 9, and 8 of 9 expressed
MIS type II receptor mRNA by reverse transcription-PCR, showing a statistically significant correlation, compared with binding, by chi2 analysis (P = 0.025). Solid
ovarian cancers were positive for the
MIS type II receptor protein by immunohistochemical staining, which colocalized with staining for antibody to CA-125 (OC-125). Thus, the detection of the MIS type I receptor by flow cytometry may be a useful predictor of therapeutic response to MIS and may be a modality to rapidly choose patients with late-stage
ovarian cancer for treatment with MIS.