Secretory acid sphingomyelinase activity is elevated in White but not Black individuals with colorectal neoplasia

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Abstract
Changes in lipid metabolism have been associated with the development of colorectal cancer (CRC), and they may serve as diagnostic markers to identify patients who have developed colorectal neoplasia. This study aimed to identify such biomarkers using untargeted lipidomics. Lipidomics were performed in serum from a racially diverse series of CRC cases and controls from Chicago and Tucson. In addition, enzymatic activity of secretory acid sphingomyelinase (aSMase; S-SMase) was measured in samples from the Tucson CRC series, and two series of adenoma patients. Untargeted lipidomics in the Chicago CRC series revealed significant alterations in sphingolipids. Targeted lipidomics revealed a robust signature of five sphingomyelins (SMs) that were significantly decreased in Chicago CRC patients compared to controls and were validated in the Tucson series. S-SMase activity, which degrades serum SMs, was elevated in CRC cases (0.13 ± 0.10 Cer/SM UACC CRC cases vs. 0.05 ± 0.04 Cer/SM controls; p<0.0001). In mostly white adenoma patients from Tucson, serum S-SMase activity could predict the presence of colorectal neoplasia (0.13 ± 0.07 Cer/SM in UACC adenoma cases vs. 0.03 ± 0.02 Cer/SM in controls; p<0.0001). However, S-SMase activity was not significantly different in Black adenoma patients from Chicago compared to controls. Together, these studies demonstrate for the first time the potential for S-SMase activity to serve as a biomarker for colorectal neoplasia in specific populations.