Helping Eve Overcome ADAM: G-Quadruplexes in the ADAM-15 Promoter as New Molecular Targets for Breast Cancer Therapeutics

Abstract

ADAM-15, with known zymogen, secretase, and disintegrin activities, is a catalytically active member of the ADAM family normally expressed in early embryonic development and aberrantly expressed in various cancers, including breast, prostate and lung. ADAM-15 promotes extracellular shedding of E-cadherin, a soluble ligand for the HER2/neu receptor, leading to activation, increased motility, and proliferation. Targeted downregulation of both ADAM-15 and HER2/neu function synergistically kills breast cancer cells, but to date there are no therapeutic options for decreasing ADAM-15 function or expression. In this vein, we have examined a unique string of guanine-rich DNA within the critical core promoter of ADAM-15. This region of DNA consists of seven contiguous runs of three or more consecutive guanines, which, under superhelical stress, can relax from duplex DNA to form an intrastrand secondary G-quadruplex (G4) structure. Using biophysical and biological techniques, we have examined the G4 formation within the entire and various truncated regions of the ADAM-15 promoter, and demonstrate strong intrastrand G4 formation serving to function as a biological silencer element. Characterization of the predominant G4 species formed within the ADAM-15 promoter will allow for specific drug targeting and stabilization, and the further development of novel, targeted therapeutics.

Identification and characterization of a new G-quadruplex forming region within the kRAS promoter as a transcriptional regulator

“…The dose-response noted in EV and SV40 plasmids were comparable, and were considered to account for background effects of TMPyP4. This nonspecific effect is most likely due to dampening of the luciferin glow by the cationic compound, in agreement with a previous study showing the same decreased RLU but no transcriptional downregulation from the EV plasmid treated with 100 M TMPyP4, as measured by PCR [37]. Any significant changes in the extent of the dose response were compared to these background effects using a two-way ANOVA.…”

The Consequences of Overlapping G-Quadruplexes and i-Motifs in the Platelet-Derived Growth Factor Receptor β Core Promoter Nuclease Hypersensitive Element Can Explain the Unexpected Effects of Mutations and Provide Opportunities for Selective Targeting of Both Structures by Small Molecules To Downregulate Gene Expression

“…41 Although these three classes are quite distinct, they share a common feature in that their constituent poly-GC tracts are not shared between multiple isoforms and give rise to a single primary G-quadruplex, as is seen in the VEGF, 67,68 HIF-1α, 69 RET, 70,71 and PDGF-A 19 promoters, 41 although there may be complexities we do not appreciate at this point. The Class IV promoter-based G-quadruplex control elements comprise multiple contiguous guanine runs that form a dynamic set of G-quadruplexes from overlapping sequences, as found in the BCL2, 72,73 ADAM-15, 74 and PDGFR-β 20 promoters. 41 The PDGFR-β core promoter NHE comprises seven contiguous guanine runs, which nucleate to form a dynamic equilibrating set of at least four G-quadruplexes, and is the most complex Class IV promoter studied to date.…”

Oxidative Stress: Role and Response of Short Guanine Tracts at Genomic Locations

“…G-quadruplex, a non-Watson–Crick DNA structure, has drawn attention of scientific community due to its unique stability and polymorphic behavior. These structures are abundantly found in gene promoters of various oncogenes such as c-myc [21,22], c-Kit [23], KRAS [24], VEGF [25,26], PDGF [27], BCL-2 [28], c-Myb [29], RET [30], AR [31], ADAM [32], hTERT [33], and MET [34], genes associated with telomere homeostasis [35], neurodegenerative diseases [36,37,38], mental retardation [39], involved in neoplasia [40], and untranslated regions [41]. Genes harboring putative G-quadruplex forming sequences (PQS) and related diseases are tabulated in Table 1.…”