  Discoveries of endogenous human stem cell-associated retroviruses (SCARs)
revealed consistent activation of specific endogenous retroviral elements in
human preimplantation embryos and documented the essential role of the
sustained retroviral activities in the maintenance of pluripotency, functional
identity and integrity of naive-state embryonic stem cells, and anti-viral
resistance of the early-stage human embryos. Activation of specific SCARs,
namely LTR7.HERVH and LTR5Hs.HERVK, has been demonstrated in patients diagnosed
with multiple types of cancer, autoimmune diseases, neurodegenerative disorders
and it is likely associated with the emergence of clinically lethal therapy
resistant death-from-cancer phenotypes in a sub-set of cancer patients
diagnosed with different types of malignant tumors.
