Serum-containing and serum-free immunoglobulin inhibitors of steroid hormone responsive cancer cell growth are disclosed, along with their methods of production. Also disclosed are defined cell culture media, assay protocols, and model systems using the inhibitors for demonstrating steroid hormone growth effects of natural and synthetic substances, and other cell culture applications. The disclosed compositions and methods employing the immunoglobulin inhibitors are also useful as reagents in research, and for the diagnosis, treatment and prevention of mucus epithelial cancers.