The development of colorectal cancer in the azoxymethane-induced mouse model can be observed by using a miniaturized optical coherence tomography (OCT) imaging system. This system is uniquely capable of tracking disease development over time, allowing for the monitoring of morphological changes in the distal colon due to tumor development and the presence of lymphoid aggregates. By using genetically engineered mouse models deficient in Interleukin 6 (IL-6) and Smad family member 3 (Smad3), the role of inflammation on tumor development and the immune system can be elucidated. Smad3 knockout mice develop inflammatory response, wasting, and colitis associated cancer while deficiency of proinflammatory cytokine IL-6 confers resistance to tumorigenesis. We present pilot data showing that the Smad3 knockout group had the highest tumor burden, highest spleen weight, and lowest thymus weight. The IL-6 deficiency in Smad3 knockout mice prevented tumor development, splenomegaly, and thymic atrophy. This finding suggests that agents that inhibit IL-6 (e.g. anti-IL-6 antibody, non-steroidal anti-inflammatory drugs [NSAIDs], etc.) could be used as novel therapeutic agents to prevent disease progression and increase the efficacy of anti-cancer agents. OCT can also be useful for initiating early therapy and assessing the benefit of combination therapy targeting inflammation.

The NSAID sulindac has been successfully used alone or in combination with other agents to suppress colon tumorigenesis in patients with genetic predisposition and also showed its efficacy in prevention of sporadic colon adenomas. At the same time, some experimental and clinical reports suggest that a mutant oncogene may negate sulindac antitumor efficacy. To directly assess sulindac activity at suppressing premalignant lesions carrying K-RAS mutation, we utilized a novel mouse model with an inducible colon-specific expression of the mutant oncogene ( ). Tumor development and treatment effects were monitored by minimally invasive endoscopic Optical coherence tomography. Expression of the mutant allele accelerated azoxymethane (AOM)-induced colon carcinogenesis in C57BL/6 mice, a strain otherwise resistant to this carcinogen. Sulindac completely prevented AOM-induced tumor formation in wild-type ( wt) animals. In -mutant mice, a 38% reduction in tumor number, an 83% reduction in tumor volume ( ≤ 0.01) and an increase in the number of adenoma-free mice ( = 0.04) were observed. The partial response of animals to sulindac treatment was evident by the decrease in mucosal thickness ( < 0.01) and delay in progression of the precancerous aberrant crypt foci to adenomas. Molecular analyses showed significant induction in cyclooxygenase 2 (COX-2), cleaved caspase-3 (CC3), and Ki-67 expression by AOM, but not sulindac treatment, in all genotypes. Our data underscore the importance of screening for mutations in individuals with colon polyps to provide more personalized interventions targeting mutant signaling pathways. .

<p>Supplementary Table 1. Statistical analysis of endpoints derived from histology. Number of animals in different groups is listed in Figure 1B. Supplementary Table 2. Statistical analysis of adenoma grade by genotypes in the subset of AOM-induced mice, 34 weeks of age, from Table 1B. Number of slides analysed is presented in parentheses. Supplementary Table 3. Analysis of colon ACF by genotypes and treatment. Supplementary Figure 1. Comformation of colon-specific expression of mutant K-Ras allele in the compound Vil-Cre-ERT2K-rasG12D mouse. Supplementary Figure 2. Characterization downstream targets of mutant K-RAS in Vil-Cre-ERT2K-rasG12D mouse model by Western blot analysis in the colon tissue of Control and AOM-treated mice of different genotypes at 26 weeks of age (18 weeks after the last AOM injection when applicable).</p>

<p>Supplementary Table 1. Statistical analysis of endpoints derived from histology. Number of animals in different groups is listed in Figure 1B. Supplementary Table 2. Statistical analysis of adenoma grade by genotypes in the subset of AOM-induced mice, 34 weeks of age, from Table 1B. Number of slides analysed is presented in parentheses. Supplementary Table 3. Analysis of colon ACF by genotypes and treatment. Supplementary Figure 1. Comformation of colon-specific expression of mutant K-Ras allele in the compound Vil-Cre-ERT2K-rasG12D mouse. Supplementary Figure 2. Characterization downstream targets of mutant K-RAS in Vil-Cre-ERT2K-rasG12D mouse model by Western blot analysis in the colon tissue of Control and AOM-treated mice of different genotypes at 26 weeks of age (18 weeks after the last AOM injection when applicable).</p>

<div>Abstract<p>The NSAID sulindac has been successfully used alone or in combination with other agents to suppress colon tumorigenesis in patients with genetic predisposition and also showed its efficacy in prevention of sporadic colon adenomas. At the same time, some experimental and clinical reports suggest that a mutant <i>K-RAS</i> oncogene may negate sulindac antitumor efficacy. To directly assess sulindac activity at suppressing premalignant lesions carrying K-RAS mutation, we utilized a novel mouse model with an inducible colon-specific expression of the mutant <i>K-ras</i> oncogene (<i>K-ras^G12D</i>). Tumor development and treatment effects were monitored by minimally invasive endoscopic Optical coherence tomography. Expression of the mutant <i>K-ras</i> allele accelerated azoxymethane (AOM)-induced colon carcinogenesis in C57BL/6 mice, a strain otherwise resistant to this carcinogen. Sulindac completely prevented AOM-induced tumor formation in <i>K-ras</i> wild-type (<i>K-ras</i> wt) animals. In <i>K-ras^G12D</i>–mutant mice, a 38% reduction in tumor number, an 83% reduction in tumor volume (<i>P</i> ≤ 0.01) and an increase in the number of adenoma-free mice (<i>P</i> = 0.04) were observed. The partial response of <i>K-Ras^G12D</i> animals to sulindac treatment was evident by the decrease in mucosal thickness (<i>P</i> < 0.01) and delay in progression of the precancerous aberrant crypt foci to adenomas. Molecular analyses showed significant induction in cyclooxygenase 2 (COX-2), cleaved caspase-3 (CC3), and Ki-67 expression by AOM, but not sulindac treatment, in all genotypes. Our data underscore the importance of screening for <i>K-RAS</i> mutations in individuals with colon polyps to provide more personalized interventions targeting mutant <i>K-RAS</i> signaling pathways. <i>Cancer Prev Res; 11(1); 16–26. ©2017 AACR</i>.</p></div>