To investigate the involvement of SLX4 in telomere maintenance, we examined telomeric localization of endogenous SLX4 in different human cell lines, including telomerase-negative ALT cells (U2OS, WI38[VA13-2RA], and GM847), telomerase-positive cancer cells (HT1080, HeLa, and its subclone HeLa1.2.11), and primary cells (BJ and MRC5). The gene discussed is GPT; the disease is cancer.