I have determined the alpha/beta ratio of the cells I am working with at hypoxic (a/b Hypoxia) by growing the cells at 1% hypoxic environment and normoxic conditions (a/b Normoxia) (21% oxygen). Subequently, I calculated OER using the formula:
OER = α/β (Hyp)/ α/β (Nor). The OER value I obtained was equal to 1.4.
To validate OER, this is what I plan to do:
I have previously irradiated my cells grown in normoxic and hypoxic conditions with the following "STANDARD" conditions:
- Hyperfractionation : 5 Gy X 4
- Hypofractionation : 20 Gy X 1
Result: The hypoxic cells were resistant to hyperfractionation, and showed about 50% viability even at Day 14, where as only 20% normoxic cells seemed to survive at Day 14 after hyperfractionation.
Hypofractionation was much more effective in killing hypoxic cells.
Now, To validate the OER calculation, I plan to irradiate my hypoxic cells with the following parameters:
- Hyperfractionation : 7 Gy X 4
- Hypofractionation : 28 Gy X 1
And compare viability of the hypoxic cells with normoxic cells irradiated using "STANDARD" conditions. Is this the right thing to do?
Is there any papers that did similar validation of OER?
I would irradiate the cells under the similar hypoxic or normoxic conditions at which they were grown. For this, we have a transportable incubator which we can bring close to the irradiation room.
More questions:
Which cells are you working with?
Why are you using 1% oxygen?
Are you planning to use 3D in-vitro models? We do.
Moreover, do you have any access to ion therapy units, to compare with photons?
Good luck!
Wolfgang
Hi, I am using both cell lines and 3D cultures of head and neck cancers. I use 1% hypoxia as i found some papers that mention 1% or less is considered to be pathological hypoxic condition, although many people use 5%. I have done both 3 and 5 %. But 1% hypoxia make the cells most radioresistant. Do you do linear quadratic modelling from the viability data using the 3D cultures?
Coming back to my original question, i have already but irradiation using the "standard" doses mentioned in my question both for normoxic and hypoxic conditions. Is it correct to validate the calculated alpha beta ratio and OER by doing the experiments using the OER corrected radiation dose mentioned in my question?
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