Characterization of a Gene Expression Signature in Normal Rat Prostate Tissue Induced by the Presence of a Tumor Elsewhere in the Organ

Abstract

Implantation of rat prostate cancer cells into the normal rat prostate results in tumor-stimulating changes in the tumor-bearing organ, for example growth of the vasculature, an altered extracellular matrix, and influx of inflammatory cells. To investigate this response further, we compared prostate morphology and the gene expression profile of tumor-bearing normal rat prostate tissue (termed tumor-instructed/indicating normal tissue (TINT)) with that of prostate tissue from controls. Dunning rat AT-1 prostate cancer cells were injected into rat prostate and tumors were established after 10 days. As controls we used intact animals, animals injected with heat-killed AT-1 cells or cell culture medium. None of the controls showed morphological TINT-changes. A rat Illumina whole-genome expression array was used to analyze gene expression in AT-1 tumors, TINT, and in medium injected prostate tissue. We identified 423 upregulated genes and 38 downregulated genes (p<0.05, ≥2-fold change) in TINT relative to controls. Quantitative RT-PCR analysis verified key TINT-changes, and they were not detected in controls. Expression of some genes was changed in a manner similar to that in the tumor, whereas other changes were exclusive to TINT. Ontological analysis using GeneGo software showed that the TINT gene expression profile was coupled to processes such as inflammation, immune response, and wounding. Many of the genes whose expression is altered in TINT have well-established roles in tumor biology, and the present findings indicate that they may also function by adapting the surrounding tumor-bearing organ to the needs of the tumor. Even though a minor tumor cell contamination in TINT samples cannot be ruled out, our data suggest that there are tumor-induced changes in gene expression in the normal tumor-bearing organ which can probably not be explained by tumor cell contamination. It is important to validate these changes further, as they could hypothetically serve as novel diagnostic and prognostic markers of prostate cancer.

Prostate tumors downregulate microseminoprotein‐beta (MSMB) in the surrounding benign prostate epithelium and this response is associated with tumor aggressiveness

“…In our previous studies, we discovered that implantation of rat prostate cancer cells into the normal rat prostate resulted in adaptive and apparently tumor‐promoting changes in the benign prostate tissue. The magnitude and nature of these changes were related to tumor size, aggressiveness, and metastatic capacity . In prostate cancer patients, similar alterations as in the rat model were also detected in the benign parts of the prostate (by us named TINT = tumor instructed normal tissue).…”

“…The MSMB level in each sample was adjusted for the corresponding 18S level and relative expression was calculated using the 2 −ΔΔCT method. Prior to dissection, the fraction of epithelial cells in the encircled TINT areas were determined using stereological techniques (ie, a square lattice was mounted in the eye‐piece of a light microscope and the fraction of grid‐intersections falling on epithelial tissue was counted) as earlier described …”

“…Importantly, quantification of these changes could be used to prognosticate outcome in men with prostate cancer managed by watchful waiting . In reprogrammed/tinted rat prostate tissue, multiple genes were up‐regulated or downregulated in tumor and in TINT in parallel . One gene markedly downregulated in prostate tumors and decreased twofold in rat prostate TINT was Msmb .…”

Extracellular Vesicles from Metastatic Rat Prostate Tumors Prime the Normal Prostate Tissue to Facilitate Tumor Growth

“…3b) and in tumor cells. Furthermore, our previous study shows that the gene-expression pattern in tumor-adjacent non-malignant prostate is similar to that in wound healing suggesting that tumors activate the prostate stroma further away in the tumor-bearing organ3. We therefore explored if tumor-derived EVs could activate primary rat prostate fibroblasts in vitro .…”

Prostate cancer induces C/EBPβ expression in surrounding epithelial cells which relates to tumor aggressiveness and patient outcome

“…Tumors instruct adjacent and remote tissues to support the growth and spread of the tumor . We have hypothesized that one consequence of this might be that aggressive tumors―already when small―induce more profound extra‐tumoral changes than more indolent tumor types, and that this knowledge could be used to improve early diagnosis and treatment of aggressive prostate cancers . Implantation of rat prostate tumor cells into the prostate of immune‐competent syngeneic rats results in adaptive changes in the surrounding normal prostate tissue.…”