The Type I Insulin-like Growth Factor Receptor (IGF-IR) clearly plays a critical role in breast tumorigenesis through its capacity to facilitate malignant transformation, promote cell proliferation, and protect malignant cells from apoptosis. The human IGF-IR mRNA contains an extraordinarily long (1,038 nucleotides) leader sequence (5'-untranslated RNA, 5'-UTR), which functions as the equivalent of a """"""""promoter"""""""" at the RNA level. We have identified three regulatory proteins (HuR, TIAR, hnRNP C) that bind in a sequence-specific manner to the IGF-IR 5'-UTR and appear to control the efficiency with which the IGF1R mRNA is translated into protein. We hypothesize that alterations in the dynamic interactions between these RNA-binding proteins and the 5'-untranslated sequence of the IGF-IR transcript may be responsible for IGF-IR overexpression in a proportion of human breast tumors, and ultimately contribute to the molecular pathogenesis of this disease. Indeed we have found a marked increase in IGF-IR translational efficiency in association with significant alterations in the activities of these RNA-binding proteins in the human breast carcinoma cell line T47D, which overexpresses IGF-IR. In addition, we propose to test the potential therapeutic utility of the isolated IGF-IR 5'-untranslated RNA, functioning as a dominant negative regulatory RNA, to specifically counteract IGF-IR overexpression and reverse the associated adverse phenotypic consequences in human breast cancer cells. We have established that such a strategy can be used to induce dramatic, favorable phenotypic alterations, including mitotic cell death and loss of tumorigenicity.
The Specific Aims are: 1. Establish the function of the RNA-binding proteins TIAR and hnRNP C in the regulation of IGFIR expression at the translational level. 2. Assay primary human breast tumor specimens for the activities of sequence, specific translation-regulatory proteins binding the 5'-untranslated region of the human IGFIR transcript (including HuR, TIAR, and hnRNP C), and correlate changes in activities of these RNA-binding proteins with IGF-IR overexpression and the malignant phenotype. 3. Ectopically express the isolated IGFIR 5'-untranslated RNA sequence in human breast cancer cells, assess the potential of this non-coding RNA sequence to modulate IGF1R expression, and consequently limit proliferative capacity, enhance apoptotic susceptibility, and reverse tumorigenicity of human breast cancer cells.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA108886-04
Application #
7234131
Study Section
Drug Discovery and Molecular Pharmacology Study Section (DMP)
Program Officer
Spalholz, Barbara A
Project Start
2004-08-18
Project End
2009-05-31
Budget Start
2007-06-01
Budget End
2008-05-31
Support Year
4
Fiscal Year
2007
Total Cost
$216,542
Indirect Cost
Name
University of Alabama Birmingham
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
063690705
City
Birmingham
State
AL
Country
United States
Zip Code
35294
Vaklavas, Christos; Grizzle, William E; Choi, Hyoungsoo et al. (2016) IRES inhibition induces terminal differentiation and synchronized death in triple-negative breast cancer and glioblastoma cells. Tumour Biol 37:13247-13264
Vaklavas, Christos; Meng, Zheng; Choi, Hyoungsoo et al. (2015) Small molecule inhibitors of IRES-mediated translation. Cancer Biol Ther 16:1471-85
Meng, Zheng; Jackson, Nateka L; Shcherbakov, Oleg D et al. (2010) The human IGF1R IRES likely operates through a Shine-Dalgarno-like interaction with the G961 loop (E-site) of the 18S rRNA and is kinetically modulated by a naturally polymorphic polyU loop. J Cell Biochem 110:531-44
Blume, Scott W; Jackson, Nateka L; Frost, Andra R et al. (2010) Northwestern profiling of potential translation-regulatory proteins in human breast epithelial cells and malignant breast tissues: evidence for pathological activation of the IGF1R IRES. Exp Mol Pathol 88:341-52
Choi, Hyoungsoo; Jackson, Nateka L; Shaw, Denise R et al. (2008) mrtl-A translation/localization regulatory protein encoded within the human c-myc locus and distributed throughout the endoplasmic and nucleoplasmic reticular network. J Cell Biochem 105:1092-108
Meng, Zheng; Jackson, Nateka L; Choi, Hyoungsoo et al. (2008) Alterations in RNA-binding activities of IRES-regulatory proteins as a mechanism for physiological variability and pathological dysregulation of IGF-IR translational control in human breast tumor cells. J Cell Physiol 217:172-83
Meng, Zheng; King, Peter H; Nabors, L Burt et al. (2005) The ELAV RNA-stability factor HuR binds the 5'-untranslated region of the human IGF-IR transcript and differentially represses cap-dependent and IRES-mediated translation. Nucleic Acids Res 33:2962-79