**11. Adaptation of PDX LuCaP lines to in vitro culture**

For therapeutic testing, the LuCaP series of >40 different models established from patient tumor samples donated at autopsies and surgeries provide an invaluable resource than long-used cultured cell lines. They have been molecularly and pharmacologically characterized, and encompass a large spectrum of the disease course and representative of human prostate cancer [39]. Transcriptomics and genomics data have shown that the gene expression of these cancer cells was concordant with that of the human tumors from which they originated. Indeed, these models were used in the preclinical study to determine efficacy of anti-prostatespecific membrane antigen (PSMA) ADC as they show a range of PSMA expression [59]. For AGR2, concordant expression has been determined by DNA microarrays [40], immunostaining [27], and ELISA measurement of secreted AGR2 [20, 38]. Similar to prostate cancer patient specimens, the adenocarcinoma lines are positive for AGR2 while the small cell carcinoma including some non-adenocarcinoma are negative or low for AGR2.

Their utility could be increased if they can be grown outside the mouse for in vitro testing of ADCC and CDC. We showed that LuCaP cells prepared from freshly excised tumors could be successfully cultured long-term in the presence of irradiated mouse embryonic fibroblasts (MEF) as feeder [60]. Furthermore, LuCaP cells could be viably frozen using a protocol for stem cells [60], which makes constant harvests from animals unnecessary. Both adenocarcinoma and small cell carcinoma LuCaP lines could be thus grown in culture (unpublished data). The in vitroadapted cell lines with differential AGR2 expression could be used to determine the molecular mechanism controlling AGR2 expression in cancer cells. The same methodology can be used to adapt CoCaB cells for in vitro growth and testing.
