T cells, on the other hand, showed clearly increased clonality and higher levels of cytotoxic T cells, yet their ability to control tumour was limited, possibly due to poor infiltration or retention outside the tumour core due to high stromal expression of the CXCR4 ligand, CXCL12 or/and the adoption of senescent phenotype. Here, CXCL12 is linked to neoplasm.