Photomicrographs illustrate immunohistochemical validation of gene-expression array results for the transcription factor SOX-9 (A-D) and the protein tyrosine phosphatase receptor type Z (PTPRZ1) (E-H), a potential target for therapy. High expression of SOX-9 is noted in the large-cell neuroendocrine carcinoma (LCNEC) (A, inset in A) and the adenocarcinoma (arrow in A) components of the donor tumor and the MDA PCa 144-4 xenograft (B), whereas low expression is noted in the small-cell carcinoma (SCC) component of both the donor tumor (C) and the MDA PCa 144-13 xenograft (D). PTPRZ expression is low in the adenocarcinoma component (arrow in E) and moderate in the LCNEC component of the donor tumor (E, inset in E) and the 144-4 xenograft (F) but is high in the SCC component of the donor tumor (G) and the 144-13 xenograft (H). (Original magnification of A, E, × 100; inset boxes in A and E, BD, F-H × 200).