We are trying to see change in MMTV mouse with our gene knockout. Can anybody suggest how to proceed with it. I mean what would be the strategy to observe the changes in terms of number/size of tumor formation, metastasis.
thanks in advance
Dear Raise,
are you referring to the MMTV-PyMT model? Which background?
estudios previos realizados en nuestro país sobre el tema con el modelo experimental propuesto ( Selgrad S y García Tamayo J, Rev Inst Nac Hig.1997,28:9 ) hemos descrito la citología, histología y ultraestructura del tumor mamario transplantable (Ca.-MMT-INHRR-984), de la Cepa de ratones N: NIH (S) desarrollado por inoculación intraperitoneal y subcutánea con la presencia de cambios ultraestructurales, así como la detección de partículas virales correspondientes a retrovirus tipo B. Ref: Selgrad Farago S, García Tamayo J. Carcinoma mamario Murino transplantable (Ca.-MMT-INHRR-984): modelo biológico para el estudio de la oncogénesis viral. Rev Inst Nac Hig (Ven) 28: 9-14, 1997
There are lots of publications that use this model so you can see a few different approaches. When we did it, for the FVB strain (where tumor development is rapid), we let all mice reach a defined age (eg 80 or 100 days) then euthanize, and remove each mammary tumor (generally all 10 glands will have them), taking measurements in 2 dimensions to get volume and weight - the combined weight gives you overall tumor burden. We then remove the lungs carefully, inflating with Bouins fixative. We count surface tumor foci on the lungs under a dissecting microscope. Then, after processing and embedding, cut sections at multipe different depths 300 microns apart, H &E stain the slides and count the number of foci per section, adding the numbers for each depth.
Another approach is to count a certain number of days (e.g 28 days) after the first mammary tumor is palpated on each mouse and then perform necropsy as above.
Dear Raise,
The best solution would be to take mice at different time point for the metastatic study, while it will be enough to anesthetize and measure with a caliper the dimension of the 10 mammary tumors. The MMTV-model should have palpable tumors by the 8th week of age. Form that time on it will take extra 7 weeks to reach a full blown adenocarcinoma. As for the metastases, you should be able to observe micrometastases already at 12 weeks, while macrometastases should be present by 16 weeks, or at least this is what we see in our lab.
For our KO studies we have tumor measurement once a week for at least 4 weeks and we either study the growth from an initial indolent stage to a carcinoma (8-12 weeks) or the progression to an adenocarcinoma with metastatic phenotype (11-15 weeks).
Given our ethical permit, we are not allowed to keep mice alive for more than 18 weeks, but already at 16 weeks the tumor burden is so big that sometimes mice cannot walk any longer as the tumors impede their movements.
Good luck,
Matteo
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