The implantation site impacts the tumour growth kinetics and tumour immune infiltrate in EO771 and 4T1 syngeneic breast cancer models

How critical is the Implantation site for the growth kinetics and immune infiltrate of syngeneic breast cancer models?

In our latest study, we tested three different implantation sites, including subcutaneous (SC) on the left flank, and orthotopically into two different mammary fat pad sites (MFP2 and MFP9). Our findings revealed that tumour growth, tumour condition, and tumour viability can all be impacted by the implantation site. We also characterised the composition of the tumour immune infiltrate in both the 4T1 and EO771 syngeneic models and found that the implantation site can affect the balance of the infiltrated immune cells.

Our conclusion was that tumours grown in the MFP9 implantation site exhibited the best overall growth kinetics, better tumour condition/viability, and a tumour immune infiltrate richer in B and T lymphocytes in both models. Therefore, the implantation site should be a key consideration when choosing models for the evaluation of therapeutics with different mechanisms of action1.