Hi Elsayed,

Are you sure that you inject alive cancer cells? Are you use normal mice or mice model? cancer cells can grow on a weak immune system. If you use a regular mouse instead of mice that the immune system is weakened, it is difficult to grow because cancer is fought by the immune system.

good luck

 As pointed out above, you need to use an immune compromised animal like a nude mouse if you are trying to grow human tumor cells or you need to use tumor cells that come from the same strain of mouse as the recipient animal to avoid host immune problems.

 Are you using tail vein or IP injection? Tail vein injection is difficult in mice and may result in very little injectate entering the vein.  IP injection is much easier and a larger bore needle can be used.

Check the viability of the cells after passing them through the syringe and needle using trypan blue to make sure that they are not damaged. 

 Finally, a fairly large number of viable cells (1e6 to1e7) must be injected.

Actually I am using nude mice, and the cells were injected by open injection in the spleen.

Also I am using a large number of cells 1e7

What panc cancer cell type are you using?  Is it known to be tumorigenic in nude mice?  If so, then cell viability should be checked as mentioned earlier.

Mia Paca-2 cells

I remember a colleague of mine assesed the invasive potential of sarcoma cells using an in-vitro test:. http://paperity.org/p/46668872/a-mycoplasmal-protein-influences-tumour-cell-invasiveness-and-contact-inhibition-in-vitro

He was able to reduce the invasiveness of the tumour cells using antibodies directed against a protein on their cell surface.

Do you still find the injected cells in the spleen where you put them three weeks ago?

All the best.

yeah I still find them in the spleen, but actually I tried another type of pancreatic cancer cells and finally tumor occur in the liver,  thanks a lot for your advice

Highly interesting you seem to have a model with invasive and non-invasive pancreatic cancer cells. As metastasis is such an important problem - what does make one line non-invasive whereas the other line is? Is there a key to invasiveness?

actually I am not sure yet about the  invasive of the two cells so I think I have to try one more time the cells that was not invasive to have more accurate data