The majority of colorectal cancer (CRC) arises from precursor lesions known as polyps. The molecular determinants that distinguish benign from malignant polyps remain unclear. To molecularly characterize polyps, we utilized Cancer Adjacent Polyp (CAP) and Cancer Free Polyp (CFP) patients. CAPs had tissues from the residual polyp of origin and contiguous cancer; CFPs had polyp tissues matched to CAPs based on polyp size, histology and dysplasia. To determine whether molecular features distinguish CAPs and CFPs, we conducted Whole Genome Sequencing, RNA-seq, and RRBS on over 90 tissues from 31 patients. CAPs had significantly more mutations, altered expression and hypermethylation compared to CFPs. APC was significantly mutated in both polyp groups, but mutations in TP53, FBXW7, PIK3CA, KIAA1804 and SMAD2 were exclusive to CAPs. We found significant expression changes between CAPs and CFPs in GREM1, IGF2, CTGF, and PLAU, and both expression and methylation alterations in FES and HES1. Integrative analyses revealed 124 genes with alterations in at least two platforms, and ERBB3 and E2F8 showed aberrations specific to CAPs across all platforms. These findings provide a resource of molecular distinctions between polyps with and without cancer, which have the potential to enhance the diagnosis, risk assessment and management of polyps.

One of the keys to eliminating the personal and financial costs of cancer lies in the early detection of the disease. Consequently, effective cancer interventions increasingly rely on our understanding of the earliest cellular and nuclear events that lead to oncogenic transformation. Colorectal cancer, the third most prevalent cancer in the United States, results from the transformation of polyps. Our group demonstrated that the alteration of chromatin organization is a pivotal event in this oncogenic transformation. Here, we analyze the differences of the nucleosomal sensitivity to mocroccocal nuclease (MNase) between histopathologically matched pre-cancerous polyps taken from patients that did not develop cancer (cancer-free polyps, CFP) and those that did develop cancer (cancer-associated polyps, CAP). We produced high-resolution nucleosome distribution and nucleosome sensitivity maps from each of the five CFP patient samples and three CAP patient samples. We show that nucleosome distribution is largely invariant between CFP and CAP samples. Nucleosome sensitivity, however, is a powerful analysis that can identify genomic locations that distinguish CFP from CAP. We have identified more than 1000 genomic locations with altered nucleosomal sensitivity that discriminate between CAP and CFP. Furthermore, we show that these genomic locations with altered nucleosomal sensitivity between CFP and CAP include genes that play critical roles in oncogenic transformation. We propose that nucleosome sensitivity serves as a robust biomarker indicating the oncogenic potential of precancerous polyps and could be used for the early detection of polyps that will become cancerous.

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