HSP90AA1 and cancer: Several studies have provided evidence supporting the existence of G4s in eukaryotic telomeres and oncogene promoters, including those of KRAS, HRAS, HSP90, c-MYC, c-KIT, BCL-2 and VEGF genes, and that small molecules stabilizing G4 structures are able to down-regulate oncogene transcription in tumor cell lines, inhibit telomerase activity and induce cancer cell growth arrest [15],[16],[17].