The HeLa cancer cell lines were first obtained from the cervix of Henrietta Lacks, a patient who had cervical cancer. The HeLa cancer cell lines are known to be the immortal cell line as the cells do not enter cellular senescence and undergo cell death. The HeLa cells can thus be cultured in-vivo for very long time under the controlled lab conditions. The primary reason for their immortality is the activity of the telomerase in restoring the length of telomere (protective end of DNA which gets shortened after every cell division). This process helps the HeLa cell in circumventing the Hayflick limit of cell division.