siRNA knockdown of ribosomal protein gene RPL19 abrogates the aggressive phenotype of human prostate cancer.

We provide novel functional data that posttranscriptional silencing of gene RPL19 using RNAi not only abrogates the malignant phenotype of PC-3M prostate cancer cells but is selective with respect to transcription and translation of other genes. Reducing RPL19 transcription modulates a subset of genes, evidenced by gene expression array analysis and Western blotting, but does not compromise cell proliferation or apoptosis in-vitro. However, growth of xenografted tumors containing the knocked-down RPL19 in-vivo is significantly reduced. Analysis of the modulated genes reveals induction of the non-malignant phenotype principally to involve perturbation of networks of transcription factors and cellular adhesion genes. The data provide evidence that extra-ribosomal regulatory functions of RPL19, beyond protein synthesis, are critical regulators of cellular phenotype. Targeting key members of affected networks identified by gene expression analysis raises the possibility of therapeutically stabilizing a benign phenotype generated by modulating the expression of an individual gene and thereafter constraining a malignant phenotype while leaving non-malignant tissues unaffected.

PRKC-ζ Expression Promotes the Aggressive Phenotype of Human Prostate Cancer Cells and Is a Novel Target for Therapeutic Intervention.

We show protein kinase C-zeta (PKC-ζ) to be a novel predictive biomarker for survival from prostate cancer (P < 0.001). We also confirm that transcription of the PRKC-ζ gene is crucial to the malignant phenotype of human prostate cancer. Following siRNA silencing of PRKC-ζ in PC3-M prostate cancer cells, stable transfectant cell line si-PRKC-ζ-PC3-M(T1-6) is phenotypically nonmalignant in vitro and in vivo. Genome-wide expression analysis identified 373 genes to be differentially expressed in the knockdown cells and 4 key gene networks to be significantly perturbed during phenotype modulation. Functional interconnection between some of the modulated genes is revealed, although these may be within different regulatory pathways, emphasizing the complexity of their mutual interdependence. Genes with altered expression following PRKC-ζ knockdown include HSPB1, RAD51, and ID1 that we have previously described to be critical in prostatic malignancy. Because expression of PRKC-ζ is functionally involved in promoting the malignant phenotype, we propose PKC-ζ as a novel and biologically relevant target for therapeutic intervention in prostate cancer.

Increased expression of Id family proteins in small cell lung cancer and its prognostic significance.

PURPOSE: To study the molecular pathology of human small cell lung cancer (SCLC), molecular biology approaches were used to identify genes involved in malignant progression of the cancer cells. EXPERIMENTAL DESIGN: Microquantity differential display was used initially to identify genes expressed differentially between normal and malignant cell lines. The differences were verified by Western blot. Immunohistochemical analysis was done on paired normal and malignant lung tissues and on tissues taken by biopsy to assess the expression status of candidate genes and their prognostic significance. RESULTS: Inhibitor of DNA/differentiation (Id)1 gene was up-regulated in SCLC cells. Levels of Id1 in 8 of 10 cell lines were increased by 1.7- to 21.4-fold when compared with the benign cells. A similar increase was also found in levels of Id2 and Id3. On 26 pairs of lung tissues, all four Id proteins were significantly (Wilcoxon Signed Rank Test, P < 0.001-0.005) overexpressed in cytoplasm of the malignant cells. In nuclei of SCLC cells, Id1 expression was significantly reduced, whereas the levels of Id2, Id3, and Id4 were significantly (Wilcoxon Signed Rank Test, P < 0.001) increased. Immunohistochemical staining on biopsy specimens showed that the increased expression of Id2 in cytoplasm of cancer cells, not the other three proteins, was significantly associated with the increased survival of SCLC patients. CONCLUSION: Changed expression profiles of Id proteins may play important roles in malignant progression of SCLC, and the increased Id2 in cytoplasm is a novel prognostic factor to predict the patient outcomes.

Expression of cutaneous fatty acid-binding protein (C-FABP) in prostate cancer: potential prognostic marker and target for tumourigenicity-suppression.

C-FABP or E-FABP is a metastasis inducing gene over expressed in human prostate carcinomas. To study its prognostic significance, an archival set of prostate tissues was analysed immunohistochemically. Levels of both nuclear and cytoplasmic C-FABP expression in carcinoma cells were significantly higher than those in normal and BPH tissues and the increased C-FABP was significantly associated with a reduced patient survival time. To test the therapeutic potential of targeting C-FABP, a clone (Si-clone-2) of cells was established by interfering C-FABP expression in highly malignant PC-3M cells. Suppression of C-FABP in cancer cells significantly inhibited their proliferation and tumourigenicity in vitro. When Si-clone-2 cells were orthotopically implanted into the prostate gland of mouse, 2/13 mice produced primary tumours with an average size of 23+/-5 mg, and no metastasis was produced in any of the 13 animals. Whereas in the control group, all 14 mice produced primary tumours with an average size of 1450+/-370 mg and 9/14 (64.3%) produced metastasis. When inoculated subcutaneously, all 5 mice inoculated with control cells developed tumours from day 4, with an average size of 1471+/-544 mm(3) at 5 weeks after the inoculation; whereas Si-clone-2 cells produced no tumours in any of the 5 animals at any time-point, indicating the suppression occurred at the initiation stage. Our results suggest that C-FABP may be used as a potential prognostic marker to predict patient outcome and the increased C-FABP expression is a possible target to inhibit the malignant progression of prostate cancer cells.

Ribosomal protein l19 is a prognostic marker for human prostate cancer.

Microquantity differential display analysis of gene expression profiles between benign (PNT2) and malignant (PC3M) human prostate cell lines identified the gene encoding ribosomal protein L19 (RPL19) to be overexpressed in the malignant cells. Northern blot hybridization analysis done on a wide range of human cell lines and tissues confirmed the level of RPL19 mRNA to be 5-fold higher in malignant cell lines and 8-fold higher in malignant tissues, when compared with their benign counterparts. Analysis of RPL19 mRNA expression by in situ hybridization revealed a significant increase of RPL19 expression in a substantial number of prostate cancers. All of the eight normal prostatic tissues were unstained (100%). Of 32 benign prostatic hyperplasia (BPH) tissues, 15 (46.9%) were unstained, 9 (28.1%) stained weakly, and 8 (25%) stained moderately. Among 87 carcinomas, only 7 (8.1%) were unstained, whereas 22 (25.2%) stained weakly, 21 (24.1%) stained moderately, and 37 (42.61%) stained strongly. The intensity of staining of the malignant specimens was significantly higher than that of normal and BPH specimens (chi(2): n = 127, P < 0.001). Gleason scores of the carcinomas correlated with RPL19 expression (chi(2): n = 87, P < 0.001). Kaplan-Meier survival analysis confirmed increased RPL19 expression to be highly predictive of shorter patient survival (P < 0.05), revealing RPL19 to be a sensitive predictor of prostate cancer progression. Expression of this protein could be a valuable marker in prostate cancer diagnosis and patient management.

High-level expression of cutaneous fatty acid-binding protein in prostatic carcinomas and its effect on tumorigenicity.

The expression of cutaneous fatty acid-binding protein (C-FABP) in prostate tissues was examined by immunohistochemistry. Among the 76 cases, all seven (100%) normal tissues were unstained. Of the 35 benign prostatic hyperplasia (BPH), 25 (71.4%) specimens were unstained and 10 (28.6%) were stained positively. For the 34 prostatic carcinomas, the C-FABP expression was remarkably increased: 25 (73.5%) samples stained positively, and only nine (26.5%) were unstained. Transfection of a vector expressing an antisense C-FABP transcript into the PC-3M prostatic cancer cells yielded two transfectant lines: PC-3M-CFABP-1 and PC-3M-CFABP-3, producing, respectively, a 3.8- and a 6.9-fold reduction in C-FABP levels. Comparing with the control transfectants, the in vitro invasiveness of both PC-3M-CFABP-1 and PC-3M-CFABP-3 was significantly reduced. When tested in nude mouse, the average size of tumours produced by PC-3M-CFABP-1 and by PC-3M-CFABP-3 was reduced by 2.9- and 4.2-fold respectively, in comparison with that of tumours produced by the control transfectants. Analysis showed that the decreased vascular endothelial growth factor (VEGF) and microvessel densities in the tumours were associated with the reduced C-FABP. These data show that C-FABP is increased in prostatic carcinoma cells and suppression of its expression can significantly inhibit the tumorigenicity, probably by reducing the expression of VEGF.

Tazarotene-induced gene 1 (TIG1) expression in prostate carcinomas and its relationship to tumorigenicity.

BACKGROUND: Prostate cancer is the most common noncutaneous male cancer and one of the least understood malignant diseases. Identifying key genetic factors involved in the metastasis of prostate cancer cells is critical. In this study, we used selective subtractive differential gene display to identify a gene whose decreased expression may contribute to the growth and expansion of prostate cancer. METHODS: We used 192 primer pair combinations and polymerase chain reaction technology to identify genes expressed in the benign prostate cell line PNT-2 but not in the malignant prostate cancer cell lines LNCaP, Du-145, PC-3, or PC-3M. The tazarotene-induced gene 1 (TIG1) was chosen for further study. TIG1 expression in normal tissues and cell lines was analyzed by northern blot and in normal and tumor prostate tissue sections by in situ hybridization. The in vitro invasiveness (migration through extracellular matrix) and in vivo tumorigenicity (growth in nude mice) were assessed for the highly malignant PC-3M cell line transfected with TIG1 or control cDNA. All statistical tests were two-sided. RESULTS: TIG1 mRNA was expressed in a variety of normal tissues other than prostate tissue. TIG1 mRNA was detected in all 10 normal human prostate tissues and all 51 benign prostatic hyperplastic tissues analyzed but in only four of 51 malignant prostate tissues analyzed. Compared with vector-transfected cells, transfection of PC-3M cells with TIG1 decreased in vitro invasiveness from 14.7% to 3.7%, (mean difference = 11%; 95% confidence interval [CI] = 9.2% to 12.8%, P<.001) and decreased in vivo tumorigenicity from an average tumor weight of 1.31 g to 0.55 g, (mean difference = 0.76 g; 95% CI = 0.43 to 1.09 g, P<.001). CONCLUSION: TIG1 may be a tumor suppressor gene whose diminished expression is involved in the malignant progression of prostate cancer.