Abstract 5178: MUC13 is a novel molecular signature, for early detection and metastatic colorectal cancer
Authors: Tripathi Manish K. , Zacheaus Chidi , Doxtater Kyle , Stiles Zachary , Keramatnia Fatemeh , Zafar Nadeem , Amin Mahul , Jaggi Meena , Chauhan Subhash 
Published: August 2018

Objective: Colorectal cancer (CRC) is a leading cause of cancer mortality affecting over a million people every year. Biological markers for early detection and distant metastatic disease in patients with CRC are not well defined. We have identified transmembrane mucin MUC13, which is expressed in normal colon mucosa to be highly expressed in colorectal cancer, but the underlying pathways and the signaling mechanisms involved in CRC pathogenesis are not known. Our studies suggest MUC13 correlation with demographic and clinicopathologic characteristics.

Materials and Methods: Retrospective institutional tumor registry was reviewed to identify patients with resected colon adenocarcinoma. Archived FFPE tissue blocks were reviewed by an experienced pathologist. Selected representative tissue blocks were serially sectioned at 4 µm. IHC staining was performed using an in-house MAb for MUC13. Slides were digitally scanned and analyzed qualitatively as well as quantitatively using a modified H-score based on the intensity of expression and percentage of stained cells. MUC13 was correlated with disease stage, aggressiveness and inflammatory markers, indicating poor prognosis in CRC patients. MUC13 splice variants were probed using novel designed probes. MUC13 SNPs were identified using unbiased approach by analyzing dpGAP database.

Results: 196 tissues, of which 56.1% were female, 52% were white, and the median age at resection was 70. 38 (19.4%) were stage I, 64 (32.7%) stage II, 84 (42.9%) stage III, and 10 (5.1%) stage IV. 100% of colon adenocarcinoma tissues stained positively for MUC13, including definitive tumor epithelial staining, little-to-no background stromal staining, and mild staining of adjacent normal colon mucosa. Typical colon adenocarcinoma cells exhibited strong apical membranous staining with varying degrees of cytoplasmic staining. Advanced stage tumors were noted to more frequently exhibit basolateral and/or circumferential membranous staining compared to early stage tumors which more frequently displayed apical membrane staining alone. Five MUC13 transcript variants were identified by database analysis. Two of the protein coding MUC13 variants (long and short) showed differential expression in aggressive cell lines and patient tissues. Cyclic turnover between the short and long isoforms were observed during Anoikis resistance, cortisol, alcohol and BAP treatments. SNPs have been associated with increased risk of cancer incidence or fatality. Relevant MUC13 SNPs have been identified through systematic analysis of patient databases (dpGAP database). Verification and correlation of identified SNPs with patient disease stage and prognosis will also be presented.

Conclusion: This is the first study to correlate MUC13 expression with disease outcome. Alternative transcripts and single nucleotide polymorphisms gave genetic insight of the role of MUC13 in CRC pathogenesis.

Citation Format: Manish K. Tripathi, Chidi Zacheaus, Kyle Doxtater, Zachary Stiles, Fatemeh Keramatnia, Nadeem Zafar, Mahul Amin, Meena Jaggi, Subhash Chauhan. MUC13 is a novel molecular signature, for early detection and metastatic colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5178.