Chinghai Kao

Establishing human prostate cancer cell xenografts in bone: Induction of osteoblastic reaction by prostate‐specific antigen‐producing tumors in athymic and SCID/bg mice using LNCaP and lineage‐derived metastatic sublines

LNCaP lineage‐derived human prostate cancer cell lines C4‐2 and C4‐2B4 acquire androgen independence and osseous metastatic potential in vivo. Using C4‐2 and C4‐2B4 the goals of the current investigation were 1) to establish an ideal bone xenograft model for prostate cancer cells in intact athymic or SCID/bg mice using an intraosseous route of tumor cell administration and 2) to compare prostate cancer metastasis by administering cells either through intravenous (i.v.) or intracardiac administration in athymic or SCID/bg mice. Subsequent to tumor cell administration, prostate cancer growth in the skeleton was assessed by radiographic bone density, serum prostate‐specific antigen (PSA) levels, presence of hematogenous prostate cancer cells and histopathologic evaluation of tumor specimens in the lymph node and skeleton. Our results show that whereas LNCaP cells injected intracardially failed to develop metastasis, C4‐2 cells injected similarly had the highest metastatic capability in SCID/bg mice. Retroperitoneal and mediastinal lymph node metastases were noted in 3/7 animals, whereas 2/7 animals developed osteoblastic spine metastases. Intracardiac injection of C4‐2 in athymic hosts produced spinal metastases in 1/5 animals at 8–12 weeks post‐injection; PC‐3 injected intracardially also metastasized to the bone but yielded osteolytic responses. Intravenous injection of either LNCaP or C4‐2 failed to establish tumor colonies. Intrailiac injection of C4‐2 but not LNCaP nor C4‐2B4 cells in athymic mice established rapidly growing tumors in 4/8 animals at 2–7 weeks after inoculation. Intrafemoral injection of C4‐2 (9/16) and C4‐2B4 (5/18) but not LNCaP (0/13) cells resulted in the development of osteoblastic bone lesions in athymic mice (mean: 6 weeks, range: 3–12 weeks). In SCID/bg mice, intrafemoral injection of LNCaP (6/8), C4‐2 (8/8) and C4‐2B4 (8/8) cells formed PSA‐producing, osteoblastic tumors in the bone marrow space within 3–5 weeks after tumor cell inoculation. A stepwise increase of serum PSA was detected in all animals. Reverse transcription‐polymerase chain reaction (RT‐PCR) to detect hematogenously disseminated prostate cancer cells could not be correlated to either serum PSA level or histological evidence of tumor cells in the marrow space. We have thus established a PSA‐producing and osteoblastic human prostate cancer xenograft model in mice. Int. J. Cancer 77:887–894, 1998.© 1998 Wiley‐Liss, Inc.

Aberrant expression of CARM1, a transcriptional coactivator of androgen receptor, in the development of prostate carcinoma and androgen-independent status

Coactivator‐associated arginine methyltransferase 1 (CARM1) is a transcriptional coactivator of the androgen receptor (AR). It is involved in the regulation of the biologic functions of the AR. It remains to be determined whether CARM1 is involved in prostatic carcinogenesis.

Lovastatin inhibits adipogenic and stimulates osteogenic differentiation by suppressing PPARγ2 and increasing Cbfa1/Runx2 expression in bone marrow mesenchymal cell cultures

The mechanism whereby lovastatin can counteract steroid-induced osteonecrosis and osteoporosis is poorly understood. We assessed the effect of lovastatin on a multipotential cell line, D1, which is capable of differentiating into either the osteoblast or the adipocyte lineage. The expression of bone cell and fat cell transcription factors Cbfa1/Runx2 and PPARgamma2, respectively, were determined. 422aP2 gene expression was analyzed. Osteocalcin promoter activity was measured by cotransfecting the cells with the phOC-luc and pSV beta-Gal plasmids. Lovastatin enhanced osteoblast differentiation as assessed by a 1.8x increase in expression of Cbfa1/Runx2 and by a 5x increase in osteocalcin promoter activity. Expression of PPARgamma2 was decreased by 60%. By enhancing osteoblast gene expression and by inhibiting adipogenesis, lovastatin may shunt uncommitted osteoprogenitor cells in marrow from the adipocytic to the osteoblastic differentiation pathway. Future evaluation of lovastatin and other lipid-lowering drugs will help determine their potential as therapeutic agents for osteonecrosis and osteoporosis.

DEVELOPMENT OF PROSTATE-SPECIFIC ANTIGEN PROMOTER-BASED GENE THERAPY FOR ANDROGEN-INDEPENDENT HUMAN PROSTATE CANCER

PURPOSE The goal of this study is to develop a tissue-specific toxic gene therapy utilizing the prostate specific antigen (PSA) promoter for both androgen-dependent (AD) and androgen-independent (AI) PSA-secreting prostate cancer cells. Ideally this gene therapy would be effective without the necessity of exposing the target cells to circulating androgens. MATERIALS AND METHODS An AI subline of LNCaP, an AD PSA-secreting human prostate cancer cell line, C4-2, was used in this study. Castrated mice bearing C4-2 tumors secrete PSA. A transient expression experiment was used to analyze the activity of two PSA promoters, a 5837 bp long PSA promoter and a 642 bp short PSA promoter, in C4-2 cells. A recombinant adenovirus (Ad-PSA-TK) carrying thymidine kinase under control of the long PSA promoter was generated. The tissue-specific activity of Ad-PSA-TK was tested in vitro and in vivo. RESULTS The long PSA promoter had superior activity over short PSA promoter, and higher activity in C4-2 cells than in LNCaP cells. High activity of Ad-PSA-TK was observed in C4-2 cells in an androgen deprived condition. In vitro, Ad-PSA-TK was further demonstrated to induce marked C4-2 cell-kill by acyclovir in medium containing 5% FBS. No cell-kill was observed in control WH cells (a human bladder cancer cell line). In vivo, Ad-PSA-P-TK with acyclovir significantly inhibited subcutaneous C4-2 tumor growth and PSA production in castrated animals. CONCLUSION The 5837 bp long PSA promoter was active in the androgen free environment and could be used to target both androgen-dependent and independent PSA-producing prostate cancer cells in vitro, and prostate tumors in castrated hosts.

Phase I Dose Escalation Clinical Trial of Adenovirus Vector Carrying Osteocalcin Promoter-Driven Herpes Simplex Virus Thymidine Kinase in Localized and Metastatic Hormone-Refractory Prostate Cancer

Osteocalcin (OC), a major noncollagenous bone matrix protein, is expressed prevalently in prostate cancer epithelial cells, adjacent fibromuscular stromal cells, and osteoblasts in locally recurrent prostate cancer and prostate cancer bone metastasis [Matsubara, S., Wada, Y., Gardner, T.A., Egawa, M., Park, M.S., Hsieh, C.L., Zhau, H.E., Kao, C., Kamidono, S., Gillenwater, J.Y., and Chung, L.W. (2001). Cancer Res. 61, 6012-6019]. We constructed an adenovirus vector carrying osteocalcin promoter-driven herpes simplex virus thymidine kinase (Ad-OC-hsv-TK) to cotarget prostate cancer cells and their surrounding stromal cells. A phase I dose escalation clinical trial of the intralesional administration of Ad-OC-hsv-TK followed by oral valacyclovir was conducted at the University of Virginia (Charlottesville, VA) in 11 men with localized recurrent and metastatic hormone-refractory prostate cancer (2 local recurrent, 5 osseous metastasis, and 4 lymph node metastasis) in order to determine the usefulness of this vector for the palliation of androgen-independent prostate cancer metastasis. This is the first clinical trial in which therapeutic adenoviruses are injected directly into prostate cancer lymph node and bone metastasis. Results show that (1). all patients tolerated this therapy with no serious adverse events; (2). local cell death was observed in treated lesions in seven patients (63.6%) as assessed by TUNEL assay, and histomorphological change (mediation of fibrosis) was detected in all posttreated specimens; (3). one patient showed stabilization of the treated lesion for 317 days with no alternative therapy. Of the two patients who complained of tumor-associated symptoms before the treatment, one patient with bone pain had resolution of pain, although significant remission of treated lesions was not observed by image examination; (4). CD8-positive T cells were predominant compared with CD4-positive T cells, B cells (L26 positive), and natural killer cells (CD56 positive) in posttreated tissue specimens; (5). levels of HSV TK gene transduction correlated well with coxsackie-adenovirus receptor expression but less well with the titers of adenovirus injected; and (6). intrinsic OC expression and the efficiency of HSV TK gene transduction affected the levels of HSV TK protein expression in clinical specimens. Our data suggest that this form of gene therapy requires further development for the treatment of androgen-independent prostate cancer metastasis although histopathological and immunohistochemical evidence of apoptosis was observed in the specimens treated. Further studies including the development of viral delivery will enhance the efficacy of Ad-OC-hsv-TK.

Osteocalcin-directed gene therapy for prostate-cancer bone metastasis

Abstract Osteocalcin (OC) is a major noncollagenous bone protein whose expression is limited almost exclusively to osteotropic tumors and mature calcified tissue (differentiated osteoblasts). The function of OC, a highly conserved gamma-carboxyglutamic acid-containing protein, relies in part on its ability to bind hydroxyapatite and act as a chemoattractant for bone-resorbing cells. Serum osteocalcin levels are used clinically as an index of active bone turnover. Research in our laboratory has revealed that OC is expressed in several solid tumors, including osteosarcoma and ovarian, lung, brain, and prostate cancers. Evidence arising from reverse-transcription polymerase chain reaction (RT-PCR; detection of OC mRNA), immunohistochemical staining (detection of OC protein), and transient transfection and reporter assay (detection of OC mRNA transcription) reveals that OC expression is up-regulated in numerous solid tumors, with its expression being further elevated in androgen-independent prostate cancers. A recombinant, replication-defective adenovirus, Ad-OC-TK (OC promoter-driven herpes-simplex-virus thymidine kinase) was constructed and, when combined with the appropriate prodrug, either ganciclovir (GCV) or acyclovir (ACV), was found to be effective at destroying prostate-cancer cell lines in vitro and prostate tumor xenografts in vivo in both subcutaneous and bone sites. Additionally, via use of the OC promoter the supporting bone stromal cells are cotargeted when the prostate cancer interdigitates with bone stroma at the metastatic skeletal sites. Thus, maximal tissue-specific cell toxicity is achieved by the interruption of cellular communication between the prostate cancer and the bone stroma. We describe herein the preclinical foundation as well as the design and implementation of an ongoing phase I clinical trial at the University of Virginia that targets androgen-independent metastatic prostate cancer using the Ad-OC-TK vector.

High-level expression of EphA2 receptor tyrosine kinase in prostatic intraepithelial neoplasia.

EphA2 is a transmembrane receptor tyrosine kinase that is overexpressed in many carcinomas. Specific targeting of EphA2 with monoclonal antibodies is sufficient to inhibit the growth, migration and invasiveness of aggressive cancers in animal models. Using immunohistochemical analyses, we measured the expression of EphA2 in prostatic adenocarcinoma, high-grade prostatic intraepithelial neoplasia, and adjacent benign prostate tissue from ninety-three radical prostatectomy specimens. These results were related to multiple clinical and pathologicalcharacteristics. The fraction of cells staining positively with EphA2 in benign prostatic epithelium (mean, 12%) was significantly lower than that in high-grade prostatic intraepithelial neoplasia (mean, 67%, P < 0.001) and prostatic adenocarcinoma (mean, 85%, P < 0.001). Moreover, the intensity of EphA2 immunoreactivity in prostatic adenocarcinoma was significantly higher than in benign prostatic tissue (P < 0.001) or high-grade prostatic intraepithelial neoplasia (P < 0.001). Benign prostatic epithelium showed weak or no immunoreactivity for EphA2 in all cases examined. Whereas EphA2 immunoreactivity related to neoplastic transformation, it did not correlate with other clinical and pathological parameters examined. Our data suggest that EphA2 levels increase as prostatic epithelial cells progress toward a more aggressive phenotype. Progressively higher levels of EphA2 in high-grade prostatic intraepithelial neoplasia and prostatic carcinoma are consistent with recent evidence that EphA2 functions as a powerful oncogene. Moreover, the presence of high levels of EphA2 in these cells suggests opportunities for prostate cancer prevention and treatment.

Regions of Prostate-specific Antigen (PSA) Promoter Confer Androgen-independent Expression of PSA in Prostate Cancer Cells

Prostate-specific antigen (PSA) is expressed primarily by both normal prostate epithelium and the vast majority of prostate cancers. Increases in serum PSA during endocrine therapy are generally considered as evidence for prostate cancer recurrence or progression to androgen independence. The mechanisms by which PSA up-regulation occurs in androgen-refractory prostate cancer cells are unknown. In this study, by using LNCaP and its lineage-derived androgen-independent PSA-producing subline, C4-2, we identified two cis-elements within the 5.8-kilobase pair PSA promoter that are essential for the androgen-independent activity of PSA promoter in prostate cancer cells. First, a previously reported 440-bpandrogen-responsive element enhancer core (AREc) was found to be important for the high basal PSA promoter activity in C4-2 cells. Both mutation analysis and supershift experiments demonstrated that androgen receptor (AR) binds to the AREs within the AREc and activate the basal PSA promoter activity in C4-2 cells under androgen-deprived conditions. Second, a 150-bp pN/H region was demonstrated to be a strong AR-independent positive-regulatory element of the PSA promoter in both LNCaP and C4-2 cells. Through DNase I footprinting and linker scan mutagenesis, a 17-bp RI site was identified as the key cis-element within the pN/H region. Data from electrophoretic mobility shift analysis and UV cross-linking experiments further indicated that a 45-kDa (p45) cell-specific transcription factor associates with RI in prostate cancer cells and may be responsible for driving the PSA promoter activity independent of androgen and AR. Furthermore, by juxtaposing AREc and pN/H, we produced a chimeric PSA promoter (supra-PSA) that exhibits 2–3-fold higher activity than the wild type PSA promoter in both LNCaP and C4-2 cells.

Cytotoxic Effects of Recombinant Adenovirus p53 and Cell Cycle Regulator Genes (p21 sup WAF1/CIP1 and p16 sup CDKN4) in Human Prostate Cancers

AbstractPurpose: Overexpressing or restoring the basal levels of tumor suppressor genes in cancer cells can suppress tumorigenicity of cancer cells. In this communication, we compared tumor suppressive activities of three well-defined tumor suppressive genes (p53, p21WAF1/CIP1, and p16CDKN2) delivered individually to prostate cancer cells with adenoviral vector (Ad).Materials and Methods: Efficacy of growth inhibition by recombinant adenoviruses bearing p53, p21WAF1/CIP1, or p16CDKN2 (Ad5CMV-p53, Ad5CMV-p21, Ad5CMV-p16) genes were tested in vitro on androgen-dependent (LNCaP) and androgen-independent (C4-2, DU-145, and PC-3) human prostate cancer cells, ex vivo and in vivo on PC-3 tumor.Results: Ad5CMV-p53 was observed to exert the greatest growth inhibitory action on all of the cell lines tested; inhibition appeared to be cytolytic. In comparison to control Ad5CMV-PA added samples, the growth inhibitory action of Ad5CMV-p21 and Ad5CMV-p16 appeared to be cytostatic. Ad5CMV-p53 is more effective than Ad5CM...

Gene Therapy for Prostate Cancer by Controlling Adenovirus E1a and E4 Gene Expression with PSES Enhancer

PSES is a chimeric enhancer containing enhancer elements from prostate-specific antigen (PSA) and prostate-specific membrane antigen (PSMA) genes that are prevalently expressed in androgen-independent prostate cancers. PSES shows strong activity equivalent to cytomegalovirus (CMV) promoter, specifically in PSA/PSMA-positive prostate cancer cells, the major cell types in prostate cancer in the absence of androgen. We developed a recombinant adenovirus (AdE4PSESE1a) by placing adenoviral E1a and E4 genes under the control of the bidirectional enhancer PSES and enhanced green fluorescent protein gene for the purpose of intratumoral virus tracking under the control of CMV promoter. Because of PSES being very weak in nonprostatic cells, including HEK293 and HER911 that are frequently used to produce recombinant adenovirus, AdE4PSESE1a can only be produced in the HER911E4 cell line which expresses both E1 and E4 genes. AdE4PSESE1a showed similar viral replication and tumor cell killing activities to wild-type adenovirus in PSA/PSMA-positive prostate cancer cells. The viral replication and tumor cell killing activities were dramatically attenuated in PSA/PSMA-negative cells. To test whether AdE4PSESE1a could be used to target prostate tumors in vivo, CWR22rv s.c. tumors were induced in nude mice and treated with AdE4PSESE1a via intratumoral and tail vein injection. Compared to tumors treated with control virus, the growth of CWR22rv tumors was dramatically inhibited by AdE4PSESE1a via tail vein injection or intratumoral injection. These data show that adenoviral replication can be tightly controlled in a novel fashion by controlling adenoviral E1a and E4 genes simultaneously with a single enhancer.