Purpose Morphologically heterogeneous prostate cancers (PC) that behave clinically like small cell PC (SCPC) share their chemotherapy responsiveness. We asked whether these clinically defined, morphologically diverse, ‘aggressive variant PC’ (AVPC) also share molecular features with SCPC. Experimental Design 59 PC samples from 40 clinical trial participants meeting AVPC criteria, and 8 patient-tumor derived xenografts (PDX) from 6 of them, were stained for markers aberrantly expressed in SCPC. DNA from 36 and 8 PDX was analyzed by Oncoscan® for copy number gains (CNG) and losses (CNL). We used the AVPC PDX to expand observations and referenced publicly available data sets to arrive at a candidate molecular signature for the AVPC. Results Irrespective of morphology, Ki67 and Tp53 stained ≥ 10% cells in 80% and 41% of samples respectively. RB1 stained <10% cells in 61% of samples and AR in 36%. MYC (surrogate for 8q) CNG and RB1 CNL showed in 54% of 44 samples each and PTEN CNL in 48%. All but 1 of 8 PDX bore Tp53 missense mutations. RB1 CNL was the strongest discriminator between unselected castration resistant PC (CRPC) and the AVPC. Combined alterations in RB1, Tp53 and/or PTEN were more frequent in the AVPC than in unselected CRPC and in The Cancer Genome Atlas samples. Conclusions Clinically defined AVPC share molecular features with SCPC and are characterized by combined alterations in RB1, Tp53 and/or PTEN.

Purpose Small-cell prostate carcinoma (SCPC) morphology predicts for a distinct clinical behavior, resistance to androgen ablation, and frequent but short responses to chemotherapy. We sought to develop model systems that reflect human SCPC and can improve our understanding of its biology. Experimental Design We developed a set of CRPC xenografts and examined their fidelity to their human tumors of origin. We compared the expression and genomic profiles of SCPC and large cell neuroendocrine carcinoma (LCNEC) xenografts to those of typical prostate adenocarcinoma xenografts. Results were validated immunohistochemically in a panel of 60 human tumors. Results The reported SCPC and LCNEC xenografts retain high fidelity to their human tumors of origin and are characterized by a marked upregulation of UBE2C and other mitotic genes in the absence of AR, retinoblastoma (RB1) and cyclin D1 (CCND1) expression. We confirmed these findings in a panel of CRPC patients' samples. In addition, array comparative genomic hybridization of the xenografts showed that the SCPC/LCNEC tumors display more copy number variations than the adenocarcinoma counterparts. Amplification of the UBE2C locus and microdeletions of RB1 were present in a subset, but none displayed AR nor CCND1 deletions. The AR, RB1, and CCND1 promoters showed no CpG methylation in the SCPC xenografts. Conclusion Modeling human prostate carcinoma with xenografts allows in-depth and detailed studies of its underlying biology. The detailed clinical annotation of the donor tumors enables associations of anticipated relevance to be made. Futures studies in the xenografts will address the functional significance of the findings.

The up-regulated expression and telomerase activity of human telomerase reverse transcriptase (hTERT) are hallmarks of tumorigenesis. The hTERT promoter has been shown to promote hTERT gene expression selectively in tumor cells but not in normal cells. However, little is known about how tumor cells differentially activate hTERT transcription and induce telomerase activity. In this study, we identified activating enhancerbinding protein-2␤ (AP-2␤) as a novel transcription factor that specifically binds to and activates the hTERT promoter in human lung cancer cells. AP-2␤ was detected in hTERT promoter DNA-protein complexes formed in nuclear extracts prepared only from lung cancer cells but not from normal cells. We verified the tumor-specific binding activity of AP-2␤ for the hTERT promoter in vitro and in vivo and detected high expression levels of AP-2␤ in lung cancer cells. We found that ectopic expression of AP-2␤ reactivated hTERT promoter-driven reporter green fluorescent protein (GFP) gene and endogenous hTERT gene expression in normal cells, enhanced GFP gene expression in lung cancer cells, and prolonged the life span of primary lung bronchial epithelial cells. Furthermore, we found that inhibition of endogenous AP-2␤ expression by AP-2␤ gene-specific small interfering RNAs effectively attenuated hTERT promoter-driven GFP expression, suppressed telomerase activity, accelerated telomere shortening, and inhibited tumor cell growth by induction of apoptosis in lung cancer cells. Our results demonstrate the tumor-specific activation of the hTERT promoter by AP-2␤ and imply the potential of AP-2␤ as a novel tumor marker or a cancer therapeutic target.Telomerase is an RNA-dependent DNA polymerase ribonucleoprotein enzyme that synthesizes telomeres after cell division and maintains chromosomal stability, leading to cellular immortalization (1, 2). It comprises a template-containing RNA component and a human telomerase reverse transcriptase (hTERT) 2 in humans (3-6). The high activity of telomerase has been implicated in cellular immortalization, transformation, and oncogenesis. Most normal somatic cells do not display telomerase activity, whereas a high level of telomerase activity is detected in germinal cells, immortalized cell lines, and 85-90% of human cancer specimens (7-13). hTERT is the catalytic subunit of telomerase (4, 5). The elevated expression of hTERT is necessary to transform normal human cells into cancer cells and is regarded as a hallmark of tumorigenesis (14). The hTERT promoter has been showed to be capable of promoting both constitutive hTERT gene and transgene expression selectively in tumors but not in normal cells (15)(16)(17). This is largely attributed to the unique ability of tumor cells to up-regulate hTERT transcription. The expression of hTERT is tightly regulated by various cellular factors. For example, expression of c-Myc has been shown to induce the expression of hTERT, whereas the expression of SP1 (stimulating protein-1) suppresses it (18,19). Two E-boxes and an activating en...