Introduction
Colonoscopy is highly effective yet inefficient at colorectal cancer (CRC) prevention with a prevalence of target (advanced adenomas) of only about 8%. Thus, finding a modality to risk-stratify for colonoscopy would be of public health implications One approach is to leverage field carcinogenesis, the concept that the gene/environmental interaction that predispose to neoplastic lesions are diffuse and thus rectal mucosa can predict risk of proximal neoplasia (1). Given the diffuse molecular alterations, our group has focused on transcriptional assessment through chromatin nano-architecture. While epigenetics such as methylation, histone acetylation etc will be reflected in chromatin nano-architecture, microRNAs (mIRs) provide an independent impact on gene expression. We, therefore, wanted to test whether chromatin + miR markers from the rectum would predict concomitant adenomas.
Aims & Methods
Chromatin Nano-architecture: We used a novel nanoscale optics technology, partial wave spectroscopic microscopy (PWS) which enables us to go quantify chromatin heterogeneity through pixel-to-pixel variability in refractive indices (2). The calculated marker correlated with fractal dimension (D).
Human Studies: We recruited patients undergoing screening/surveillance colonoscopy with IRB consent. Following colonoscopy 6 biopsies of endoscopically normal rectum. We had 104 controls and 53 advanced adenoma patients for these studies. Advanced adenomas were defined as size >10mm, >25% villous features or high grade dysplasia. Controls were those without adenomas/carcinomas.
miR: We used RT-PCR with internal controls. We used literature to identify 4 candidates miRs and used the delta delta approach to compute fold change of miR expression (case versus control).
Results
We analyzed D from the rectal biopsies with PWS from our clinical dataset and observed excellent diagnostic performance of area under receiver operator characteristic curve (AUC) of = 0.85 for those with and without advanced adenomas sensitivity = 0.74, specificity = 0.83.
The potential of our biomarker is also evaluated via combining with epigenetic regulators microRNAs (miR) in an independent pilot study. Evaluating the 4 oncomiRs in 20 human rectal biopsies (10 control, 10 advanced adenoma) had increased expressions in patients harboring advanced adenomas (fold changes were miR137=3.4, miR92a=5.97, miR-135b-5p=174 and miR361-5p=2.01).
With our PWS marker, the elevation of miR-92a, miR-135b-5p, and D was synergistic for discriminating patients with vs. without advanced adenomas to 0.9 increase in AUC compared to D alone. AUC) = 0.90, sensitivity = 0.88, specificity = 0.85.
Conclusion
We demonstrate, for the first time, that the chromatin nano-architectural parameter, D had excellent performance for identifying patients screen relevant neoplasia elsewhere in the colon. Furthermore, adding several miR markers to provide a more comprehensive epigenetic profile was synergistic diagnostics with D. Future studies will employ more miRs and combine with artificial intelligence to further improve the already strong performance for potential clinical impact.
References
Rebello D, Rebello E, Custodio M, Xu X, Gandhi S, Roy HK. Field carcinogenesis for risk stratification of colorectal cancer. Adv Cancer Res. 2021;151:305-344. doi: 10.1016/bs.acr.2021.03.004. Epub 2021 Mar 31. PMID: 34148616.
Gladstein S, Damania D, Almassalha LM, Smith LT, Gupta V, Subramanian H, Rex DK, Roy HK, Backman V. Correlating colorectal cancer risk with field carcinogenesis progression using partial wave spectroscopic microscopy. Cancer Med. 2018 May;7(5):2109-2120. doi: 10.1002/cam4.1357. Epub 2018 Mar 23. PMID: 29573208; PMCID: PMC5943438.
Disclosure
Hemant Roy, Vadim Backman, and Hariharan Subramanian are co-founders, have equity stakes, own IP and are on the Board of Directors for Nanocytomics LLC, a biomedical company providing cancer risk-stratification tests based on their proprietary biophotonics technology platform, partial wave spectroscopic (PWS) microscopy which is being utilized in this research. Sravya Prabhala is also an employee of Nanocytomics LLC.