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> I am currently working with an androgen independent prostate
>cancer cell line. Using the Oncor ApopTag kit, I have gotten beautiful
>pictures of cells undergoing apoptosis, however, there are a few
>phenomenas that I notice that I can't explain- namely:
> 1. Apoptosis is supposed to be marked by cell shrinkage whereas
>my cells (which underwent ionizing irradiation) are markedly larger than
>the control cells.
> 2. In the positive controls and cells that undergo a lot of
>apoptosis, I notice a lot of cells have FITC label only on the membrane
>creating a "ring" around these cells. Is this indicative of early apoptosis?
>(the cells have been fixed)
I am studying apoptosis induced by chemotherapeutic drugs (such as taxol and
vincristine) in human Burkitt's lymphoma cell lines. I am also adding
radiation to the treatment protocol. I see the phenomenom you decribed in
paragraph #1 frequently.
Ionizing radiation causes cells to pause in the G2 phase of the cell cycle.
This pause continues for a dose-dependent length of time (about 1 hr/Gy or
more for some cell lines). During this pause, the cells continue protein
synthesis. This is the reason why they get larger. At high enough doses
(several hundred Gy) cells cease to divide entirely and multinucleated giant
cells can be observed. Cells may remain in this state for several weeks.
Thomas L. Morgan, Ph.D.
Department of Radiation Oncology
Kaiser Permanente Regional Medical Center
4950 Sunset Blvd.
Los Angeles, CA 90027
(213) 667-3560 FAX (213) 667-4568 e-mail: MORGANTL@aol.com
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