The loss of ATRX in gliomas [13], neuroendocrine tumors [14] and various sarcoma types [15–19] facilitates alternative lengthening of the telomeres (ALT) and thereby stabilizes the genome of cancer cells during cancer development, a crucial step in the immortalization of cancer cells in general and a requirement for the formation of malignant tumors in humans [20]. This evidence concerns the gene ATRX and cancer.