Stromal and epithelial transcriptional map of initiation progression and metastatic potential of human prostate cancer

Abstract

While progression from normal prostatic epithelium to invasive cancer is driven by molecular alterations, tumor cells and cells in the cancer microenvironment are co-dependent and co-evolve. Few human studies to date have focused on stroma. Here, we performed gene expression profiling of laser capture microdissected normal non-neoplastic prostate epithelial tissue and compared it to non-transformed and neoplastic low-grade and high-grade prostate epithelial tissue from radical prostatectomies, each with its immediately surrounding stroma. Whereas benign epithelium in prostates with and without tumor were similar in gene expression space, stroma away from tumor was significantly different from that in prostates without cancer. A stromal gene signature reflecting bone remodeling and immune-related pathways was upregulated in high compared to low-Gleason grade cases. In validation data, the signature discriminated cases that developed metastasis from those that did not. These data suggest that the microenvironment may influence prostate cancer initiation, maintenance, and metastatic progression.Stromal cells contribute to tumor development but the mechanisms regulating this process are still unclear. Here the authors analyze gene expression profiles in the prostate and show that stromal gene signature changes ahead of the epithelial gene signature as prostate cancer initiates and progresses.

Fig. 1

Heatmaps of the GO biological processes enriched in a epithelial and b stromal compartments across healthy prostate tissues and stages of prostate cancer progression. The cells in the heatmaps are colored according to the FDR of the process in the gene set analysis. Dark blue color corresponds to significance at 0.05 level and yellow to FDR > 0.2. Categories across compartments show conserved to unique processes from H to B to P to T. Most relevant pathways are summarized in categories: Category 1 (top) epithelial: amino acid metabolism; Category 2 epithelial: secretory pathway; Category 3 epithelial: RNA synthesis; Category 4 epithelial: RNA, protein, and lipid synthesis; Category 5 epithelial: miscellaneous; Category 1 (top) stromal: muscle development and localization; Category 2 stromal: immune regulation, angiogenesis and cell proliferation; Category 3 stromal: signal transduction, cell migration and angiogenesis; Category 4 stromal: TGF beta, signal transduction and bone remodeling; Category 5 stromal: miscellaneous

Fig. 2

GO biological processes differentially enriched between a Benign and tumor epithelium; b Benign and tumor adjacent stroma. Lengths of the bars are equal to −log10(FDR) values from the gene set analysis. Negative values indicate enrichment in benign epithelium or stroma, respectively, positive values indicate enrichment in the tumor or tumor adjacent stroma

Fig. 3

Genes and pathways differentially expressed in benign tissue between cystoprostatectomy and RP specimens. a Heatmap of genes differentially expressed in benign epithelium of prostate cancer patients and cystoprostatectomy patients without prostate cancer. Gleason grade corresponds to the grade of the prostate tumor present in the block and NT (no tumor) denotes cystoprostatectomy cases. b Heatmap of genes and c heatmap of SNORDs differentially expressed in stroma surrounding benign glands from prostate cancer patients and cystoprostatectomy patients without prostate cancer. d –Log10 FDR-values from the pathways analysis of the genes differentially expressed in benign stroma using GO biological processes annotations

Fig. 4

Genes differentially expressed in stroma surrounding high-Gleason grade and low-Gleason grade prostate tumors. a ssGSEA score of the stromal signature in tumor adjacent stroma; b ssGSEA score of the stromal signature in benign-adjacent stroma; c ssGSEA score of the stromal signature in low cellularity TCGA samples; d ssGSEA score of the stromal signature in high cellularity TCGA samples; e ssGSEA score of the stromal signature between indolent and lethal cases from GSE46691 cohort; f Immunohistochemical staining of epithelial ALCAM in Gleason 3 + 3 case; g Immunohistochemical staining of epithelial gene ALCAM in Gleason 4 + 4 case; h Immunohistochemical staining of stromal SULF1 in Gleason 3 + 3 case; i Immunohistochemical staining of stromal SULF1 in Gleason 3 + 3 case. P-values in (a–e) are from corresponding t-tests