Abstract B31: Sulindac inhibition of tumor cell transformation

Abstract

Abstract Cell transformation is the process in which normal cells acquire the properties of cancer. Sulindac Sulfide (SS) is one of non-steroidal anti-inflammatory drugs (NSAIDs), and its anticancer activity in prevention of tumor occurrence and progression has been documented in various human cancers. In this study, we observed the anti-transformative activity of SS in NIH/3T3 cells by using a two-stage transformation assay induced by the carcinogens, 3-methylcholanthrene (MCA) and 2-O-tetradecanoylphorbol-13-acetate (TPA) in which foci formation is used to characterize the transformed cells. We found that SS could inhibit foci formation by attenuation of TPA's promotive effect. K-Ras was upregulated in the transformed cells, while SS treatment could selectively inhibit the growth of transformed cell in which K-Ras was suppressed significantly. Loss-of-function study demonstrated that knockdown of K-Ras in NIH/3T3 cells could significantly reduce foci formation, which support that K-Ras might be one of the key targets involved in SS inhibiting tumor cell transformation. When studying the mechanism by which SS regulates K-Ras, we triggered two tumor suppressor miRNAs, let-7b and let-7g, which were previously reported to target K-Ras and repress its expression through the post-transcriptional or translational modulation. We found that let-7b and let-7g could be upregulated in the transformed cells by SS treatment. However, the inhibitory effect of SS on foci formation was significantly attenuated when let-7b and let-7g were knocked down by CRISPR/cas9. In parallel, K-Ras maintained static expression in the transformed cells, regardless of SS treatment. These results suggest that upregulation of let-7b and let-7g is the key step for SS to inhibit tumor transformation. In addition, we demonstrated that SS could suppress the expression of Lin28 that interacts with let-7 through a documented feedback loop. Given our previous studies reporting that SS was able to inhibit the transcriptional activity of NF-kappaB that is involved in regulation of Lin28 expression, our study demonstrates that the NF-kappaB/Lin28/Let-7/K-Ras axis addresses a new mechanism responsible for anti-transformative activity of SS. These results will provide novel insights into understanding the mechanisms involved in tumorigenesis and benefiting identification of new targets for drug development in prevention of tumor progression. This study is supported by the NIH/NCI R01 Grant (1R01CA192395) and the American Cancer Society Research Scholar Grant (RSG-13-265-01-RMC). Citation Format: Zhipin Liang, Xiangling Feng, Hong Chang, Bin Yi, Ruixia Ma, Yaguang Xi. Sulindac inhibition of tumor cell transformation. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Cancer Cell Cycle - Tumor Progression and Therapeutic Response; Feb 28-Mar 2, 2016; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(11_Suppl):Abstract nr B31.