W1757 Interstitial Cells of Cajal in Achalasia

Abstract

Introduction: Genes that encode Cancer testis (CT) antigens are normally expressed only in the human germline. High frequencies of expression in various tumors and restricted expression in normal tissues make the CT antigens attractive cancer vaccine targets. PLAC1, MAGE3A and GAGE are genes with high expression in placenta/or testis and different cancer types with relatively restricted expression in normal tissues. The aim of this study was to evaluate PLAC1, MAGE3A and GAGE as vaccine targets in colorectal cancers. Method: Consenting CRC patients who underwent elective resection for whom tumor samples and preoperative blood samples were available comprise the study population. Basic demographic and clinical as well as short term outcome data was prospectively collected. Tissues were paraffin embedded and also stored at -80οC. Total purified RNA was isolated and cDNA synthesized. Comparative quantitative PCR (QPCR) was performed using the SYBR Green platform. Comparative quantitative analysis was performed based on delta-delta Ct method using GAPDH as internal control. Expression levels in tumors were compared to expression levels in Testis (MAGE3 and GAGE ) or levels in Placenta (PLAC1) and samples found to express 0.1% or more of the testis or placenta levels were considered positive for the expression of these genes. Results: 35 tumors and paired normal tissue samples were studied (83% colon, 17% rectal). Stage breakdown was as follows: stage 2, 18; stage 3, 16; and stage 4, 1 patient. Relative QPCR values of 35 malignant and paired normal samples for MAGEA3 and QPCR values of 31 pairs for PLAC1 and GAGE were available for analysis. Relative expression ratio of malignant to normal tissues over one(1) was higher for PLAC1 (77%) and moderate for GAGE (35.5%) and MAGEA3 (31%). However, both expression ratio over one (1) and expression levels above 0.1% of the levels in testis or placenta were noted for MAGE3A in 26%, PLAC1 (19%) but not for GAGE1. Conclusion: In a subset of tumors, the relative expression of MAGE3A and PLAC1 was considered above the expression in paired normal colon tissues and had more than 0.1% of the levels in testis and placenta. Serological evaluation and immunohistochemistry studies are needed to further evaluate the tumor subsets presenting MAGEA3 and PLAC1 expression. These results suggest that MAGEA3 and PLAC1 might be useful as vaccine targets for a subset of CRC patients and further studies are warranted.