|Sulindac inhibits tumor cell invasion by suppressing NF-κB-mediated transcription of microRNAs. |
Li, X; Gao, L; Cui, Q; Gary, BD; Dyess, DL; Taylor, W; Shevde, LA; Samant, RS; Dean-Colomb, W; Piazza, GA; Xi, Y
Non-steroidal anti-inflammatory drugs (NSAIDs) have been widely reported to display strong efficacy for cancer chemoprevention, although their mechanism of action is poorly understood. The most well-documented effects of NSAIDs include inhibition of tumor cell proliferation and induction of apoptosis, but their effect on tumor cell invasion has not been well studied. Here, we show that the NSAID, sulindac sulfide (SS) can potently inhibit the invasion of human MDA-MB-231 breast and HCT116 colon tumor cells in vitro at concentrations less than those required to inhibit tumor cell growth. To study the molecular basis for this activity, we investigated the involvement of microRNA (miRNA). A total of 132 miRNAs were found to be altered in response to SS treatment, including miR-10b, miR-17, miR-21 and miR-9, which have been previously implicated in tumor invasion and metastasis. We confirmed that these miRNA can stimulate tumor cell invasion and show that SS can attenuate their invasive effects by downregulating their expression. Employing luciferase and chromatin immunoprecipitation assays, NF-κB was found to bind the promoters of all four miRNAs to suppress their expression at the transcriptional level. We show that SS can inhibit the translocation of NF-κB to the nucleus by decreasing the phosphorylation of IKKβ and IκB. Analysis of the promoter sequences of the miRNAs suppressed by SS revealed that 81 of 115 sequences contained NF-κB-binding sites. These results show that SS can inhibit tumor cell invasion by suppressing NF-κB-mediated transcription of miRNAs.
|Mouse tissues that undergo neoplastic progression after K-Ras activation are distinguished by nuclear translocation of phospho-Erk1/2 and robust tumor suppressor responses. |
Parikh, N; Shuck, RL; Nguyen, TA; Herron, A; Donehower, LA
Molecular cancer research : MCR
Mutation of K-Ras is a frequent oncogenic event in human cancers, particularly cancers of lungs, pancreas, and colon. It remains unclear why some tissues are more susceptible to Ras-induced transformation than others. Here, we globally activated a mutant oncogenic K-Ras allele (K-Ras(G12D)) in mice and examined the tissue-specific effects of this activation on cancer pathobiology, Ras signaling, tumor suppressor, DNA damage, and inflammatory responses. Within 5 to 6 weeks of oncogenic Ras activation, mice develop oral and gastric papillomas, lung adenomas, and hematopoietic hyperproliferation and turn moribund. The oral, gastric, and lung premalignant lesions display activated extracellular signal-regulated kinases (Erk)1/2 and NF-κB signaling as well as activated tumor suppressor and DNA damage responses. Other organs such as pancreas, liver, and small intestine do not exhibit neoplastic progression within 6 weeks following K-Ras(G12D) activation and do not show a potent tumor suppressor response. Even though robust Erk1/2 signaling is activated in all the tissues examined, the pErk1/2 distribution remains largely cytoplasmic in K-Ras(G12D)-refractory tissues (pancreas, liver, and intestines) as opposed to a predominantly nuclear localization in K-Ras(G12D)-induced neoplasms of lung, oral, and gastric mucosa. The downstream targets of Ras signaling, pElk-1 and c-Myc, are elevated in K-Ras(G12D)-induced neoplastic lesions but not in K-Ras(G12D)-refractory tissues. We propose that oncogenic K-Ras-refractory tissues delay oncogenic progression by spatially limiting the efficacy of Ras/Raf/Erk1/2 signaling, whereas K-Ras-responsive tissues exhibit activated Ras/Raf/Erk1/2 signaling, rapidly form premalignant tumors, and activate potent antitumor responses that effectively prevent further malignant progression.
|MicroRNA-30c-2* limits expression of proadaptive factor XBP1 in the unfolded protein response. |
Byrd, AE; Aragon, IV; Brewer, JW
The Journal of cell biology
Stress in the endoplasmic reticulum (ER) triggers the unfolded protein response (UPR), a multifaceted signaling system coordinating translational control and gene transcription to promote cellular adaptation and survival. Microribonucleic acids (RNAs; miRNAs), single-stranded RNAs that typically function as posttranscriptional modulators of gene activity, have been shown to inhibit translation of certain secretory pathway proteins during the UPR. However, it remains unclear whether miRNAs regulate UPR signaling effectors directly. In this paper, we report that a star strand miRNA, miR-30c-2* (recently designated miR-30c-2-3p), is induced by the protein kinase RNA activated-like ER kinase (PERK) pathway of the UPR and governs expression of XBP1 (X-box binding protein 1), a key transcription factor that augments secretory capacity and promotes cell survival in the adaptive UPR. These data provide the first link between an miRNA and direct regulation of the ER stress response and reveal a novel molecular mechanism by which the PERK pathway, via miR-30c-2*, influences the scale of XBP1-mediated gene expression and cell fate in the UPR.