We analyzed PTMs that occur in the most important biomarkers of cell proliferation, such as octamer-binding transcription factor 4 (OCT4), SRY-box transcription factor 2 (SOX2), and NANOG, cluster of differentiation CD24/44, cyclin-dependent kinases (CDKs), Ki-67 nuclear biomarker used by histopathologists to identify proliferating cells by immunohistochemical techniques, and specificity protein 1 (SP1), known to modulate cancer cell proliferation through its translocation during the cell cycle progression. This evidence concerns the gene MKI67 and cancer.