Re: Do BM derived cells contribute to tumor ECs?
This report of a mouse model in which tumor endothelium is not bone-marrow-derived is important and deserves careful attention, but it is very far from the last word on the subject for at least two reasons:
1) The extent to which local or BM derived cells are used to repopulate tissues is known to vary between species.
2) This was a mouse model. One of the key weaknesses of the mouse model in cancer research is the difference between human and mouse telomerase and telomeres. Humans turn off telomerase in almost all tissues, leading to the well-known "Hayflick limit." It is entirely possible, even likely, that under heavy stimulation from growth factors in a tumor, the local endothelium in human tumors exhausts its telomeres and subsequently must recruit from the bone marrow. As I understand it, this may even explain the spontaneous involution of infantile hemangiomas. Laboratory mice have very long telomeres and relatively short lives. This makes their tumors much less dependent on telomerase than human tumors. They may develop large, lethal tumors without ever exhausting the telomeres in the tumor or local endothelial compartment. This difference between mice and men delayed the discovery of the role of telomerase in human tumors and the subsequent development (ongoing) of anti-telomerase directed therapies.
If aged or transgenically telomere-deficient mice showed the same result in a repeat of the experiment, I would view it as a much stronger result with respect to applicability to humans.
Best Regards,
C-Peptide
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