HS3ST4 and cancer: Indeed, the over-expression of telomere repeats binding factor 2 (TRF2), a key factor in telomere protection, can result in the upregulation of heparan sulfate-glucosamine 3-O-sulfotransferase 4 (HS3ST4) in cancer cells by binding to the interstitial telomeric repeat located within the HS3ST4 intron (106).