Hi Michael.

 Michael i have faced the same issues than you.  There are several reasons that can explain this. 

-          Have you tried different cell concentrations?  1,2,3,4 millions of cells in nude mice?

-          Cells co-injected with matrigel also can help to the grafting

-          Are your cells  bona fide tumoral cells?

-           Does your cells shoe in vitro tumoral properties

-          remember that Nude mice are not completely immune compromised mice, they still have immunity so you can tried using a more immuno compromised strain such as SCID

-          Try doing your experiment at a age of 7-8 weeks mice.  The older the mice the more probabilities they develop immune response.

At the end Michael I solved the issues using a more severe immunocompromised strain,  doing experiment at earlier  age.  But remember that each cell line has own properties.

Best.

Hi Michael.

 Michael i have faced the same issues than you.  There are several reasons that can explain this. 

-          Have you tried different cell concentrations?  1,2,3,4 millions of cells in nude mice?

-          Cells co-injected with matrigel also can help to the grafting

-          Are your cells  bona fide tumoral cells?

-           Does your cells shoe in vitro tumoral properties

-          remember that Nude mice are not completely immune compromised mice, they still have immunity so you can tried using a more immuno compromised strain such as SCID

-          Try doing your experiment at a age of 7-8 weeks mice.  The older the mice the more probabilities they develop immune response.

At the end Michael I solved the issues using a more severe immunocompromised strain,  doing experiment at earlier  age.  But remember that each cell line has own properties.

Best.

Hi  Carlos 

I have considered the same reasons actually , this cell line NTERA-2 developed tumor as reported previously at even lower cell number than I used here, and nude mice is 5 week old when I injected cells, so cell and mice age might not be the reason .

I think NOD/SCID is my only choice.

Thanks a lot for your help!

Why do you want the mice to develop tumors?

Hi Michael,

I think you can consider using NSG mice too!

When I did injections with kidney cancer cells, I met similar problem, but most mice will develop tumors again. After discussed with my colleagues, I found this issue is common for many kidney cancer cells in our current mouse strain. The previous strain is much better but discontinued. In our opinion, it means the tumorigenesis ability of this cell line is not strong in this mice strain, most cancer cells will die after injection and only a few of cancer cells (I am not sure if these are cancer stem cells) can survive and grow tumor again. If you keep the mice longer (around two months), you may see tumors again. If you still cannot see tumors, you have to change mice strain or try more cells per injection.

First of all why are you using nude mice for your experiments. There are more than often cases where one get weird results not only with tumorigenesis but with many other experiments too.

I had the same problem a year ago with nude mice. Then I did a revision about this issue and I concluded that if you want for any reason make the implantation in nude, will be necessary the utilization of Yellow nude mice (Avy, derived from C57BL/6JAvy mice), or in agreement with was explained here by other colleagues, in SCID mice. Maybe the spontaneous tumor regression occurs because of the kind of response in this tumor (Kidney tumors) that can be mediated by natural killer cells. 

Exp Cell Biol. 1979;47(2):129-35. Spontaneous tumors in nude mice: effect of the viable yellow gene. Stutman O.

9-19-2016,

Please study the Works of Nobel Prize winning (1980 for Physiology or Medicine) Immunologist and Geneticist, George D. Snell, from whom I learned basic Cancer Immuno-Genetics in Mice, at the Jackson Laboratories, in Bar Harbor, ME, which greatly enabled my successful Career, as a Cancer Research Scientist.  George Snell shared the Nobel Prize in 1980, with 2 others, for showing that very small genetic changes in MHC immunity genes, in closely inbred strains of mice, can greatly alter resistance to transplantable tumor establishment and growth in the host mice. 

These 2 below Publications by George Snell, may be helpful:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1209522/ , Alleles at the Histocompatibility-2 Locus in the Mouse as Determined by Tumor Transplantation., by George D. Snell and George F. Higgins, Genetics. 1951 May; 36(3): 306–310. 

PMCID: PMC1209522 .

http://cancerres.aacrjournals.org/content/12/8/543.full-text.pdf , The immunogenetics of tumor transplantation., by Snell GD, Cancer Res., 1952 Aug;12(8):543-6., PMID: 14945043.

Since slight genetic drift in the mouse strain, or the tumor cell line (cell source and passage number), can greatly alter the intended and expected experimental tumor model natural growth, and response to therapy, it is helpful to learn as much as possible, about the Immuno-Genetics of both, the experimental tumor cell model being used, and the mouse or rat donor and/or host strain being used.

Even different mouse breeding houses, at the same breeding Facility, can have slightly different genetic drift, which can alter your expected tumor/host model.

Careful Gross and Histopathological examination of all stages of tumor growth and regression, are very important, for full accurate description and understanding of results. Take many Photos.

If possible, frequent serological analysis of host immune response to tumor implant, and treatment, can be very helpful in describing and understanding results.

Try to double check all of the above, and try to control for as many tumor and host variables, as you can, in order to get the best reproducible, comparable, and meaningful results, for your Cancer Research Investigations.  Best of Luck.