No abstract

TIG1 may be a tumor suppressor gene whose diminished expression is involved in the malignant progression of 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 (m 2 : n = 127, P < 0.001). Gleason scores of the carcinomas correlated with RPL19 expression (m 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.

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.

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 Id1in 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.

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.

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Background:Heat shock protein 27 (Hsp-27) encoded by gene HSPB1 is a critical regulator of the behavioral phenotype of human prostate cancer (PCa) cells, enhanced expression being associated with highly aggressive disease and poor clinical outcome. In contrast, the protein is not expressed in PCas of low malignant potential. To gain insight into the mechanism regulating its expression, we tested the hypothesis that differential methylation of CpG islands within HSPB1 controls transcription and subsequent translation of the gene.Methods:We studied prostate epithelial cell lines and tissue biopsies, including 59 BPH and 415 PCas, of which 367 were a cohort of men with up to 20 years of follow-up. Methylation across the gene (DNA methylation (DNAme)) was assayed by pyrosequencing. Hsp-27 expression was assessed by western blot and immunohistochemistry.Results:In cancer tissues, methylation increased in a 3′ direction (P<0.0001) whereas in benign hyperplasia methylation was constantly below 5%, a cutoff giving a specificity of 100% and sensitivity of 50%. Although methylation of the promoter region was significantly discriminating between benign and malignant prostatic epithelia, it compared poorly with methylation of the first intron. The prognostic value of HSPB1 DNAme was confirmed by both univariate (hazard ratio 1.77 per 50% increment, P=0.02) and multivariate models. Interaction between HSPB1 methylation and Gleason score revealed high DNAme to be a reliable prognostic marker of poor outcome in men with low Gleason score (P=0.014).Conclusions:Our data indicate CpG methylation of the first HSPB1 intron to be an important biomarker that identifies aggressive PCas otherwise regarded as low risk by current clinical criteria but that, biologically, require immediate active management.