Abstract B297: Clinical assessment of MUC1 protein expression in FFPE tissue: Developent and validation of an immunohistochemistry assay as a predictive assay for response to MUC1 vaccines.
Authors: Sankar Sabita , Wright Jennifer , Klucher Kevin , Peterson Scott , Galderisi Chad 
Published: August 2014

Background: Mucin-1 (MUC1, epithelial membrane antigen, EMA) is a transmembrane glycoporotein that is expressed on the apical membrane of epithelial cells of many tissues including breast, prostate, lung, pancreas, stomach, ovaries, intestines, and kidneys. In tumor cells, MUC1 is often overexpressed and aberrantly glycosylated, revealing new epitopes that can trigger a cytotoxic T-cell response. Several approaches are currently being pursued for targeting MUC1 in cancer therapy, mainly focused on vaccines targeting MUC1 antigens. We have developed an immunohistochemistry (IHC) assay to measure MUC1 expression in formalin fixed paraffin-embedded (FFPE) tissues as a potential biomarker assay for MUC1-targeted therapies.

Methods: The IHC assays were developed using the Ventana Benchmark™. The MUC1 antibody was obtained from Ventana. The assay was validated using the recommended protocol supplied by the vendor. The assay was optimized using cell pellets generated from cell lines overexpressing MUC1 cDNA as well as an FFPE breast tumor tissue array which consists of 16 cases of breast cancer paired with adjacent normal tissues. In addition, tissue specimens obtained from remnant material from surgery or autopsy were used for the assay optimization and validation.

Results: Specificity of the staining was demonstrated by positive staining with T47D breast cancer cell line as well as a B16 cell line overexpressing MUC1 and no staining with HMEC human mammary epithelial cells and the control B16 cell line. Thirty-six FFPE tumor tissues from lung, ovary, breast, colon, kidney, liver, thyroid, and prostate were evaluated for MUC1 expression. Tumor positive specimens were scored based on expression in at least 25% of tumor cells. In addition, staining intensities as well as patterns i.e. apical or membrane polarization and cytoplasmic patterns were noted. 29/36 specimens had positive MUC1 staining; negative staining was reported in thyroid, liver, colon, and prostate tumor tissues. In addition, evaluation of the array of paired normal/tumor breast tissues showed specific staining of tumor tissues in 14/16 specimens with no or little staining in the matched normal tissue. Interestingly, one of the tumor tissues exhibited very distinct apical staining pattern that was unique in the set of 16 breast cancer tissues.

Conclusions: We have developed a robust IHC assay for MUC1 that can clearly distinguish MUC1 expression in normal versus tumor tissue as well as demonstrated variable MUC1 expression in a variety of tumor tissues. We are currently exploring the utility of the assay as a biomarker for ONT-10, a novel liposomal cancer vaccine that is currently in clinical trials.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B297.

Citation Format: Sabita Sankar, Jennifer Wright, Kevin Klucher, Scott Peterson, Chad Galderisi. Clinical assessment of MUC1 protein expression in FFPE tissue: Developent and validation of an immunohistochemistry assay as a predictive assay for response to MUC1 vaccines. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B297.