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The proto-oncogene KRAS is targeted by miR-200c.

ABSTRACT: The GTPase K-ras is involved in a variety of cellular processes such as differentiation, proliferation and survival. However, activating mutations, which frequently occur in many types of cancer, turn KRAS into one of the most prominent oncogenes. Likewise, miR-200c is a key player in tumorigenesis functioning as a molecular switch between an epithelial, non-migratory, chemosensitive and a mesenchymal, migratory, chemoresistant state. While it has been reported that KRAS is modulated by several tumor suppressor miRNAs, this is the first report on the regulation of KRAS by miR-200c, both playing a pivotal role in oncogenesis. We show that KRAS is a predicted target of miR-200c and that the protein expression of KRAS inversely correlates with the miR-200c expression in a panel of human breast cancer cell lines. KRAS was experimentally validated as a target of miR-200c by Western blot analyses and luciferase reporter assays. Furthermore, the inhibitory effect of miR-200c-dependent KRAS silencing on proliferation and cell cycle was demonstrated in different breast and lung cancer cell lines. Thereby, the particular role of KRAS was dissected from the role of all the other miR-200c targets by specific knockdown experiments using siRNA against KRAS. Cell lines harboring an activating KRAS mutation were similarly affected by miR-200c as well as by the siRNA against KRAS. However, in a cell line with wild-type KRAS only miR-200c was able to change proliferation and cell cycle. Our findings suggest that miR-200c is a potent inhibitor of tumor progression and therapy resistance, by regulating a multitude of oncogenic pathways including the RAS pathway. Thus, miR-200c may cause stronger anti-tumor effects than a specific siRNA against KRAS, emphasizing the potential role of miR-200c as tumor suppressive miRNA.

SUBMITTER: Kopp F

PROVIDER: S-EPMC3960200 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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The proto-oncogene KRAS is targeted by miR-200c.

Kopp Florian F Wagner Ernst E Roidl Andreas A

Oncotarget 20140101 1

The GTPase K-ras is involved in a variety of cellular processes such as differentiation, proliferation and survival. However, activating mutations, which frequently occur in many types of cancer, turn KRAS into one of the most prominent oncogenes. Likewise, miR-200c is a key player in tumorigenesis functioning as a molecular switch between an epithelial, non-migratory, chemosensitive and a mesenchymal, migratory, chemoresistant state. While it has been reported that KRAS is modulated by several ...[more]

PMID: 24368337

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Project description:In human and mouse, the promoter of the KRAS gene contains a nuclease hypersensitive polypurine-polypyrimidine element (NHPPE) that is essential for transcription. An interesting feature of the polypurine G-rich strand of NHPPE is its ability to assume an unusual DNA structure that, according to circular dichroism (CD) and DMS footprinting experiments, is attributed to an intramolecular parallel G-quadruplex, consisting of three G-tetrads and three loops. The human and mouse KRAS NHPPE G-rich strands display melting temperature of 64 and 73 degrees C, respectively, as well as a K+-dependent capacity to arrest DNA polymerase. Photocleavage and CD experiments showed that the cationic porphyrin TMPyP4 stacks to the external G-tetrads of the KRAS quadruplexes, increasing the T(m) by approximately 20 degrees C. These findings raise the intriguing question that the G-quadruplex formed within the NHPPE of KRAS may be involved in the regulation of transcription. Indeed, transfection experiments showed that the activity of the mouse KRAS promoter is reduced to 20% of control, in the presence of the quadruplex-stabilizing TMPyP4. In addition, we found that G-rich oligonucleotides mimicking the KRAS quadruplex, but not the corresponding 4-base mutant sequences or oligonucleotides forming quadruplexes with different structures, competed with the NHPPE duplex for binding to nuclear proteins. When vector pKRS-413, containing CAT driven by the mouse KRAS promoter, and KRAS quadruplex oligonucleotides were co-transfected in 293 cells, the expression of CAT was found to be downregulated to 40% of the control. On the basis of these data, we propose that the NHPPE of KRAS exists in equilibrium between a double-stranded form favouring transcription and a folded quadruplex form, which instead inhibits transcription. Such a mechanism, which is probably adopted by other growth-related genes, provides useful hints for the rational design of anticancer drugs against the KRAS oncogene.

Dataset Information

The proto-oncogene KRAS is targeted by miR-200c.

Publications

The proto-oncogene KRAS is targeted by miR-200c.

Similar Datasets

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