Background: KRAS mutations have been associated with lung metastases at diagnosis of metastatic colorectal cancer (mCRC), but the impact of this mutation on subsequent development of lung metastasis is unknown. We investigated KRAS mutation as a predictor of lung metastasis development.

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3522 Background: Preliminary data suggests that ctDNA can serve as a marker of minimal residual disease following colorectal cancer (CRC) tumor resection. Applicability of current ctDNA testing is limited by the requirement of sequencing known individual tumor mutations. We explored the applicability of a multi-gene panel ctDNA detection technology in CRC. Methods: Plasma was prospectively collected from CRC patients (pts) undergoing hepatic resections with curative intent between 1/2013 to 9/2016. In a blinded manner 5ml of preoperative (preop) and immediate post-operative (postop) plasma were tested using a novel 30kb ctDNA digital sequencing panel (Guardant Health) covering SNVs in 21 genes and indels in 9 genes based on the landscape of genomic alterations in ctDNA from over 10,000 advanced cancer pts with a high theoretical sensitivity (96%) for CRC. Median unique molecule coverage for this study is 9000 for cfDNA inputs ranging from 10 – 150 ng (media input preop = 27 ng, median input postop = 49 ng) with 120,000X sequencing depth on an IIlumina HiSeq2500. Results: A total of 54 pts underwent liver metastectomies with curative intent with a median follow-up of 33 months. Preop blood was a median of 49 days from last systemic chemotherapy and 3 days prior to surgery; postop blood was a median of 17 days after resection. Tumor mutations from standard of care hotspot multigene panel testing (at MDACC) were identified in 46 of 54 pts (85%). Preop ctDNA mutation detection rate was 80% (43/54) and 44% (24/54) in postop setting, with postop median allele frequency of 0.16% (range 0.01% to 20%). In pts with a minimum of 1 year follow up, sensitivity of postop ctDNA for residual disease was 58% (95%CI; 41%-74%), and specificity was 100% (66%-100%). In 43 patients who underwent successful resection of all visible disease, postop detection of ctDNA significantly correlated with RFS (P = 0.002, HR 3.1; 95% CI 1.7-9.1) with 2-year RFS of 0% vs. 47%. Recurrence was detected in ctDNA a median of 5.1 months prior to radiographic recurrence. Conclusions: The detection of postop ctDNA using an NGS panel-based approach is feasible and is associated with a very high rate of disease recurrence.

According to the "distorted key" theory as elaborated in a review article years ago (Chou, K.C.: Analytical Biochemistry, 1996, 233, 1-14), the knowledge of the cleavable peptides by SARS-CoV M(pro) (severe acute respiratory syndrome coronavirus main proteinase) can provide very useful insights on developing drugs against SARS. In view of this, the softwares, ZCURVE_CoV 1.0 and ZCURVE_CoV 2.0 (http://tubic.tju.edu.cn/sars/), developed recently for SARS-Coronavirus are used to analyze the 36 complete SARS-Coronavirus RNA sequences in the gene bank NCBI (http://www.ncbi.nlm.nih.gov/) from different sources for protein coding genes, and to search for the cleavage sites of SARS-CoV M(pro) in polyproteins pp1a and pp1ab. A total of 396 cleavage points are found in the 36 SARS-Coronavirus and 11 cleavable octapeptides abstracted from the 396 cleavage sites. The statistical distributions of amino acids for the cleavable octapeptides at the subsites R4, R3, R2, R1, R1', R2', R3' and R4' are calculated. The cleavage-specific positions are on R2, R1 and R1', and the positions R3 and R4 are featured by some certain specificity for SARS-CoV M(pro). The structural characters of amino acid residues around the cleavage-specific positions are discussed. Two most promising octapeptides, i.e., NH(2)-ATLQ downward arrowAIAS-COOH and NH(2)-ATLQ downward arrowAENV-COOH, are selected to be the candidates for chemical modification, converting into the inhibitors of SARS-CoV M(pro). A possible strategy to convert a cleavable octapeptide by SARS enzyme into a drug candidate against SARS is elucidated.

ObjectiveEnhancer aberrations are beginning to emerge as a key epigenetic feature of colorectal cancers (CRC), however, a comprehensive knowledge of chromatin state patterns in tumour progression, heterogeneity of these patterns and imparted therapeutic opportunities remain poorly described.DesignWe performed comprehensive epigenomic characterisation by mapping 222 chromatin profiles from 69 samples (33 colorectal adenocarcinomas, 4 adenomas, 21 matched normal tissues and 11 colon cancer cell lines) for six histone modification marks: H3K4me3 for Pol II-bound and CpG-rich promoters, H3K4me1 for poised enhancers, H3K27ac for enhancers and transcriptionally active promoters, H3K79me2 for transcribed regions, H3K27me3 for polycomb repressed regions and H3K9me3 for heterochromatin.ResultsWe demonstrate that H3K27ac-marked active enhancer state could distinguish between different stages of CRC progression. By epigenomic editing, we present evidence that gains of tumour-specific enhancers for crucial oncogenes, such as ASCL2 and FZD10, was required for excessive proliferation. Consistently, combination of MEK plus bromodomain inhibition was found to have synergistic effects in CRC patient-derived xenograft models. Probing intertumour heterogeneity, we identified four distinct enhancer subtypes (EPIgenome-based Classification, EpiC), three of which correlate well with previously defined transcriptomic subtypes (consensus molecular subtypes, CMSs). Importantly, CMS2 can be divided into two EpiC subgroups with significant survival differences. Leveraging such correlation, we devised a combinatorial therapeutic strategy of enhancer-blocking bromodomain inhibitors with pathway-specific inhibitors (PARPi, EGFRi, TGFβi, mTORi and SRCi) for EpiC groups.ConclusionOur data suggest that the dynamics of active enhancer underlies CRC progression and the patient-specific enhancer patterns can be leveraged for precision combination therapy.