PGR and neoplasm: Figure 3 shows the expression of ER and PR in tumour tissue from patient 56, tumour tissue from F2 generation of PDX 56, and tumour tissue from F2 generation of cryopreserved PDX 56 generation F1, using either FCS/DMSO or vitrification (Fig. 3). PR expression increased in F2 generations compared with the primary tumour. Neither of the storage methods influenced the expression levels of ER and PR (Fig. 3).