Expression of proto-oncogene c-kit in high risk prostate cancer

Tissue-Based Genomic Testing in Prostate Cancer: 10-Year Analysis of National Trends on the Use of Prolaris, Decipher, ProMark, and Oncotype DX

BACKGROUND

Prostate cancer (PCa) management is moving towards patient-tailored strategies. Advances in molecular and genetic profiling of tumor tissues, integrated with clinical risk assessments, provide deeper insights into disease aggressiveness. This study aims to offer a comprehensive overview of the pivotal genomic tests supporting PCa treatment decisions, analyzing-through real-world data-trends in their use and the growth of supporting literature evidence.

METHODS

A retrospective analysis was conducted using the extensive PearlDiver™ Mariner database, which contains de-identified patient records, in compliance with the Health Insurance Portability and Accountability Act (HIPAA). The International Classification of Diseases (ICD) and Current Procedural Terminology (CPT) codes were employed to identify patients diagnosed with PCa during the study period-2011 to 2021. We determined the utilization of primary tissue-based genetic tests (Oncocyte DX®, Prolaris®, Decipher®, and ProMark®) across all patients diagnosed with PCa. Subsequently, within the overall PCa cohort, patients who underwent radical prostatectomy (RP) and received genetic testing postoperatively were identified. The yearly distribution of these tests and the corresponding trends were illustrated with graphs.

RESULTS

During the study period, 1,561,203 patients with a PCa diagnosis were recorded. Of these, 20,748 underwent tissue-based genetic testing following diagnosis, representing 1.3% of the total cohort. An increasing trend was observed in the use of all genetic tests. Linear regression analysis showed a statistically significant increase over time in the use of individual tests (all p-values < 0.05). Among the patients who underwent RP, 3076 received genetic analysis following surgery, representing 1.27% of this group.

CONCLUSIONS

Our analysis indicates a growing trend in the utilization of tissue-based genomic testing for PCa. Nevertheless, they are utilized in less than 2% of PCa patients, whether at initial diagnosis or after surgical treatment. Although it is anticipated that their use may increase as more scientific evidence becomes available, their role requires further elucidation.

Immunolabelling of SCF and c-KIT in canine perianal gland tumours

c-KIT and its ligand stem cell factor (SCF) play a direct role in the oncogenesis of various cancers by regulating the cell fate. Recent evidence indicates that an increased expression of c-KIT/SCF, driven by hormonal imbalances, is an important step in the development of hormone-dependent cancers. We investigated the possible role of the c-KIT/SCF system in the carcinogenesis in 44 perianal gland tumours (16 adenomas, 15 epitheliomas and 13 carcinomas) and 10 normal perianal gland tissues by assessing the percentage and type of cells that expressed c-KIT and SCF as well as the cellular localization of immunoreactivity. No differences in immunolabelling of SCF were found between normal glands and neoplastic cells of any histotype. The highest expression of c-KIT was seen in carcinomas and a positive correlation was found between c-KIT labelling score and mitotic index (R = 0.876; P <0.01). c-KIT labelling patterns in hepatoid cells varied among the tumour histotypes with adenomas having only membranous labelling. Three labelling patterns (membranous only, membranous and cytosolic, and cytosolic only) were seen in the other tumour histotypes. Cytosolic labelling was statistically more frequent in carcinomas than in adenomas (P <0.001). These findings suggest that c-KIT expression and its cellular localization may play a role in the development and progression of perianal gland tumours by influencing cell proliferation.

CD117/c-kit defines a prostate CSC-like subpopulation driving progression and TKI resistance

Cancer stem-like cells (CSCs) are associated with cancer progression, metastasis, and recurrence, and may also represent a subset of circulating tumor cells (CTCs). In our prior study, CTCs in advanced prostate cancer patients were found to express CD117/c-kit in a liquid biopsy. Whether CD117 expression played an active or passive role in the aggressiveness and migration of these CTCs remained an open question. In this study, we show that CD117 expression in prostate cancer patients is associated with decreased overall and progression-free survival and that activation and phosphorylation of CD117 increases in prostate cancer patients with higher Gleason grades. To determine how CD117 expression and activation by its ligand stem cell factor (SCF, kit ligand, steel factor) alter prostate cancer aggressiveness, we used C4-2 and PC3-mm human prostate cancer cells, which contain a CD117+ subpopulation. We demonstrate that CD117+ cells display increased proliferation and migration. In prostaspheres, CD117 expression enhances sphere formation. In both 2D and 3D cultures, stemness marker gene expression is higher in CD117+ cells. Using xenograft limiting dilution assays and serial tumor initiation assays, we show that CD117+ cells represent a CSC population. Combined, these data indicate that CD117 expression potentially promotes tumor initiation and metastasis. Further, in cell lines, CD117 activation by SCF promotes faster proliferation and invasiveness, while blocking CD117 activation with tyrosine kinase inhibitors (TKIs) decreased progression in a context-dependent manner. We demonstrate that CD117 expression and activation drives prostate cancer aggressiveness through the CSC phenotype and TKI resistance.

Transcriptome of Two Canine Prostate Cancer Cells Treated With Toceranib Phosphate Reveals Distinct Antitumor Profiles Associated With the PDGFR Pathway

Canine prostate cancer (PC) presents a poor antitumor response, usually late diagnosis and prognosis. Toceranib phosphate (TP) is a nonspecific inhibitor of receptor tyrosine kinases (RTKs), including vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR), and c-KIT. This study aimed to evaluate VEGFR2, PDGFR-β, and c-KIT protein expression in two established canine PC cell lines (PC1 and PC2) and the transcriptome profile of the cells after treatment with TP. Immunofluorescence (IF) analysis revealed VEGFR2 and PDGFR-β protein expression and the absence of c-KIT protein expression in both cell lines. After TP treatment, only the viability of PC1 cells decreased in a dose-dependent manner. Transcriptome and enrichment analyses of treated PC1 cells revealed 181 upregulated genes, which were related to decreased angiogenesis and cell proliferation. In addition, we found upregulated PDGFR-A, PDGFR-β, and PDGF-D expression in PC1 cells, and the upregulation of PDGFR-β was also observed in treated PC1 cells by qPCR. PC2 cells had fewer protein-protein interactions (PPIs), with 18 upregulated and 22 downregulated genes; the upregulated genes were involved in the regulation of parallel pathways and mechanisms related to proliferation, which could be associated with the resistance observed after treatment. The canine PC1 cell line but not the PC2 cell line showed decreased viability after treatment with TP, although both cell lines expressed PDGFR and VEGFR receptors. Further studies could explain the mechanism of resistance in PC2 cells and provide a basis for personalized treatment for dogs with PC.

Tumor⁻Microenvironment Interaction: Analysis of Mast Cell Populations in Normal Tissue and Proliferative Disorders of the Canine Prostate

Mast cells (MCs) are involved in angiogenesis, tissue remodeling and immunomodulation in several human and animal tumors, although their exact role is still controversial. Since no information is available in canine prostate carcinoma (PC) and normal prostate tissues, the aims of this study were to evaluate the possible correlations between MC distribution, molecular expression and microvessel density (MVD) in normal prostatic tissue and proliferative disorders of the canine prostate. All samples (6 normal, 15 benign prostate hyperplasia-BPH, 8 PC) were stained with Toluidine Blue and immunohistochemically evaluated for tryptase, c-Kit (CD117) and CD31. Mast cell density (MCD) and MVD were quantified by the hot-spot method. MCD was significantly increased in periglandular/peritumoral areas, when compared with intraglandular/intratumoral areas, in all groups (p = 0.03). C-Kit expression was strongly associated with PC (ρ = 0.75 p = 0.03), whereas positive correlation between tryptase and c-Kit expression (ρ = 0.64 p = 0.01) was observed in periglandular areas of BPH. MVD showed a correlation with MCD in BPH (ρ = 0.54 p = 0.04). Our data support the importance of c-Kit in regulating MC proliferation. The predominant location of MCs in peritumoral areas of canine PC was similar to the human counterpart, in which PC cells are supposed to produce substances attracting MCs to the tumor microenvironment.

Expression of tumour progression-associated genes in circulating tumour cells of patients at different stages of prostate cancer

OBJECTIVE

To evaluate the presence of circulating tumour cells (CTCs) at different stages of prostate cancer using the AdnaTest^® ProstateCancerDetect kit (Qiagen). Moreover, we aimed to assess the expression of transcripts that are specific for cancer stem cells (AdnaTest StemCell) and epithelial-mesenchymal transition (EMT) in CTCs (AdnaTest EMT), as well as additional genes that are known to promote prostate cancer progression.

PATIENTS AND METHODS

In this prospective study, we included 81 patients who underwent treatment for prostate cancer between 07/2014 and 02/2015, including: Group A, 18 patients (22.2%) with low-risk clinically localised prostate cancer; Group B, 25 patients (30.9%) with high-risk clinically localised prostate cancer; Group C, 11 patients (13.6%) with metastatic castration-sensitive prostate cancer (mCSPC); and Group D, 27 patients (33.3%) with metastatic castration-resistant prostate cancer (mCRPC). AdnaTest ProstateCancer and AdnaTest StemCell/EMT were performed in all cases. In addition, expression of the androgen receptor (AR), c-met, c-kit and thymidylate synthase (TYMS) in CTCs was assessed using specific polymerase chain reaction assays.

RESULTS

A positive AdnaTest ProstateCancer was present in three (16.7%), two (8.0%), six (54.5%) and 19 (70.5%) patients in groups A, B, C and D, respectively (P < 0.01, chi-squared test). The AdnaTest EMT and AdnaTest StemCell were positive in zero (0.0%), zero (0.0%), one (9.1%), and two (7.4%); and in five (27.8%), four (16.0%), three (27.3%), and 11 (40.7%) patients in groups A, B, C and D, respectively, with no significant differences noted between groups. CTCs expressing TYMS (44.4% and 50.0% vs 13.9%) or AR (18.2% and 25.9% vs 0.0%) were seen more commonly in patients in groups C and D vs patients with non-metastatic disease (all P < 0.05). Expression of c-kit and c-met were rare events, with only two patients positive for either marker.

CONCLUSIONS

AdnaTest ProstateCancerDetect exhibits positive results mainly in patients with metastatic disease. Expression of AR and TYMS are frequent events in CTCs of patients with advanced disease, whereas c-met and c-kit gene expression is seen in only a small proportion of patients. The implications of these results for the use of CTC analysis as a decision factor for personalised treatment strategies in advanced prostate cancer remain to be determined.

Protein expression patterns of cell cycle regulators in operable breast cancer

Background-Aim

To evaluate the prognostic role of elaborate molecular clusters encompassing cyclin D1, cyclin E1, p21, p27 and p53 in the context of various breast cancer subtypes.

Methods

Cyclin E1, cyclin D1, p53, p21 and p27 were evaluated with immunohistochemistry in 1077 formalin-fixed paraffin-embedded tissues from breast cancer patients who had been treated within clinical trials. Jaccard distances were computed for the markers and the resulted matrix was used for conducting unsupervised hierarchical clustering, in order to identify distinct groups correlating with prognosis.

Results

Luminal B and triple-negative (TNBC) tumors presented with the highest and lowest levels of cyclin D1 expression, respectively. By contrast, TNBC frequently expressed Cyclin E1, whereas ER-positive tumors did not. Absence of Cyclin D1 predicted for worse OS, while absence of Cyclin E1 for poorer DFS. The expression patterns of all examined proteins yielded 3 distinct clusters; (1) Cyclin D1 and/or E1 positive with moderate p21 expression; (2) Cyclin D1 and/or E1, and p27 positive, p53 protein negative; and, (3) Cyclin D1 or E1 positive, p53 positive, p21 and p27 negative or moderately positive. The 5-year DFS rates for clusters 1, 2 and 3 were 70.0%, 79.1%, 67.4% and OS 88.4%, 90.4%, 78.9%, respectively.

Conclusions

It seems that the expression of cell cycle regulators in the absence of p53 protein is associated with favorable prognosis in operable breast cancer.

The stem cell factor (SCF)/c-KIT signalling in testis and prostate cancer

The stem cell factor (SCF) is a cytokine that specifically binds the tyrosine kinase receptor c-KIT. The SCF/c-KIT interaction leads to receptor dimerization, activation of kinase activity and initiation of several signal transduction pathways that control cell proliferation, apoptosis, differentiation and migration in several tissues. The activity of SCF/c-KIT system is linked with the phosphatidylinositol 3-kinase (PI3-K), the Src, the Janus kinase/signal transducers and activators of transcription (JAK/STAT), the phospholipase-C (PLC-γ) and the mitogen-activated protein kinase (MAPK) pathways. Moreover, it has been reported that cancer cases display an overactivation of c-KIT due to the presence of gain-of-function mutations or receptor overexpression, which renders c-KIT a tempting target for cancer treatment. In the case of male cancers the most documented activated pathways are the PI3-K and Src, both enhancing abnormal cell proliferation. It is also known that the Src activity in prostate cancer cases depends on the presence of tr-KIT, the cytoplasmic truncated variant of c-KIT that is specifically expressed in tumour tissues and, thus, a very interesting target for drug development. The present review provides an overview of the signalling pathways activated by SCF/c-KIT and discusses the potential application of c-KIT inhibitors for treatment of testicular and prostatic cancers.

An aptamer-based targeted delivery of miR-26a protects mice against chemotherapy toxicity while suppressing tumor growth

The efficacy of traditional chemotherapy is limited by its toxicity, especially with regard to hematopoiesis. Here we show that miR-26a plays a critical role in protecting mice against chemotherapy-induced myeloid suppression by targeting a proapoptotic protein (Bak1) in hematopoietic stem/progenitor cells (HSPCs). Because c-Kit is expressed at high levels in HSPCs, we designed a microRNA-aptamer chimera that contains miR-26a mimic and c-Kit-targeting aptamer and successfully delivered miR-26a into HSPCs to attenuate toxicity of 5' fluorouracil (5-FU) and carboplatin. Meanwhile, our in silico analysis revealed widespread and prognosis-associated downregulation of miR-26a in advanced breast cancer and also showed that KIT is overexpressed among basal-like breast cancer cells and that such expression is associated with poor prognosis. Importantly, the miR-26a aptamer effectively repressed tumor growth in vivo and synergized with 5-FU or carboplatin in cancer therapy in the mouse breast cancer models. Thus, targeted delivery of miR-26a suppresses tumor growth while protecting the host against myelosuppression by chemotherapy.

Clinical significance of endothelial cell marker CD34 and mast cell marker CD117 in prostate adenocarcinoma

Prostate cancer is the second cause of cancer-related deaths in men and this is attributed to its aggressiveness and metastatic identity. Our objective was to evaluate the expression patterns of endothelial cell marker CD34 and mast cell marker CD117 in prostate adenocarcinoma (PCa) compared to benign prostate tissue and their relation to the clinicopathological features. A total of 90 prostate samples, including 45 PCa and 45 benign prostate tissues were immunohistochemically examined for the detection of CD34 and CD117 markers. The expression of these markers was also correlated with clinicopathological parameters. Significant overexpression of CD34 was found in PCa group compared to benign prostate tissues (P≤0.001). The expression of CD34 and CD117 in PCa with advanced Gleason score was more than PCa with early Gleason score (P=0.02 and P=0.005, respectively). A significant positive correlation was observed between CD34 expression and the level of total serum prostate specific antigen (sPSA) (P=0.006). In addition, CD34High/CD117High phenotype was frequently observed in PCa cases compared to benign prostate tissues (P≤0.001). There was a positive significant association between CD34High/CD117High phenotype with advanced Gleason score (P≤0.001) and total sPSA level (P=0.02). Our findings showed that increased expression of CD34 and CD117 markers confer tumor progression and aggressiveness on PCa. These molecules may be good candidates for targeted therapy of PCa patients.

Imatinib Spares cKit-Expressing Prostate Neuroendocrine Tumors, whereas Kills Seminal Vesicle Epithelial-Stromal Tumors by Targeting PDGFR-β

Prostate cancer is a leading cause of cancer-related death in males worldwide. Indeed, advanced and metastatic disease characterized by androgen resistance and often associated with neuroendocrine (NE) differentiation remains incurable. Using the spontaneous prostate cancer TRAMP model, we have shown that mast cells (MCs) support in vivo the growth of prostate adenocarcinoma, whereas their genetic or pharmacologic targeting favors prostate NE cancer arousal. Aiming at simultaneously targeting prostate NE tumor cells and MCs, both expressing the cKit tyrosine kinase receptor, we have tested the therapeutic effect of imatinib in TRAMP mice. Imatinib-treated TRAMP mice experience a partial benefit against prostate adenocarcinoma, because of inhibition of supportive MCs. However, they show an unexpected outgrowth of prostate NE tumors, likely because of defective signaling pathway downstream of cKit receptor. Also unexpected but very effective was the inhibition of epithelial-stromal tumors of the seminal vesicles achieved by imatinib treatment. These tumors normally arise in the seminal vesicles of TRAMP mice, independently of the degree of prostatic glandular lesions, and resemble phyllodes tumors found in human prostate and seminal vesicles, and in breast. In both mice and in patients, these tumors are negative for cKit but express PDGFR-β, another tyrosine kinase receptor specifically inhibited by imatinib. Our results imply a possible detrimental effect of imatinib in prostate cancer patients but suggest a promising therapeutic application of imatinib in the treatment of recurrent or metastatic phyllodes tumors. Mol Cancer Ther; 16(2); 365-75. ©2016 AACR.

Current Stem Cell Biomarkers and Their Functional Mechanisms in Prostate Cancer

Currently there is little effective treatment available for castration resistant prostate cancer, which is responsible for the majority of prostate cancer related deaths. Emerging evidence suggested that cancer stem cells might play an important role in resistance to traditional cancer therapies, and the studies of cancer stem cells (including specific isolation and targeting on those cells) might benefit the discovery of novel treatment of prostate cancer, especially castration resistant disease. In this review, we summarized major biomarkers for prostate cancer stem cells, as well as their functional mechanisms and potential application in clinical diagnosis and treatment of patients.

CD117⁺ cells in the circulation are predictive of advanced prostate cancer

Circulating tumor cells (CTCs) are associated with cancer progression, aggressiveness and metastasis. However, the frequency and predictive value of CTCs in patients remains unknown. If circulating cells are involved in tumor aggressiveness and metastasis, then cell levels should decline upon tumor removal in localized cancer patients, but remain high in metastatic patients. Accordingly, proposed biomarkers CD117/c-kit, CD133, CXCR4/CD184, and CD34-positive cell percentages in the blood of patients undergoing radical prostatectomy for localized cancer were assessed by flow cytometry prior to intervention and 1–3 months postoperatively. Only circulating CD117⁺ cell percentages decreased after radical prostatectomy, increased with cancer progression and correlated with high PSA values. Notably, postoperative CD117⁺ levels did not decrease in patients experiencing biochemical recurrence. In a xenograft model, CD117-enriched tumors were more vascularized and aggressive. Thus, CD117 expression on CTCs promotes tumor progression and could be a biomarker for prostate cancer diagnosis, prognosis, and/or response to therapy.

Estrogens down-regulate the stem cell factor (SCF)/c-KIT system in prostate cells: Evidence of antiproliferative and proapoptotic effects

The development of prostate cancer (PCa) is intimately associated with the hormonal environment, and the sex steroids estrogens have been implicated in prostate malignancy. However, if some studies identified estrogens as causative agents of PCa, others indicated that these steroids have a protective role counteracting prostate overgrowth. The tyrosine kinase receptor c-KIT and its ligand, the stem cell factor (SCF), have been associated with the control of cell proliferation/apoptosis and prostate carcinogenesis, and studies show that estrogens regulate their expression in different tissues, though, in the case of prostate this remains unknown. The present study aims to evaluate the role of 17β-estradiol (E2) in regulating the expression of SCF/c-KIT in human prostate cell lines and rat prostate, and to investigate the consequent effects on prostate cell proliferation and apoptosis. qPCR, Western Blot, and immuno(cito)histochemistry analysis showed that E2-treatment decreased the expression of SCF and c-KIT both in human prostate cells and rat prostate. Furthermore, the diminished expression of SCF/c-KIT was underpinned by the diminished prostate weight and reduced proliferation index. On the other hand, the results of TUNEL labelling, the increased activity of caspase-3, and the augmented expression of caspase-8 and Fas system in the prostate of E2-treated animals indicated augmented apoptosis in response to E2. The obtained results demonstrated that E2 down-regulated the expression of SCF/c-KIT system in prostate cells, which was associated with antiproliferative and proapoptotic effects. Moreover, these findings support the protective role of estrogens in PCa and open new perspectives on the application of estrogen-based therapies.

[C-KIT in gastrointestinal stromal tumors and associated malignancies: A Study in a population with genetic isolation]

INTRODUCTION

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. Numerous studies have reported the association between GIST and other neoplasms.

OBJECTIVES

The aim of this study was to investigate the possible association between GIST and other tumors in a genetically isolated population.

METHODS

A retrospective study was conducted of patients with GIST between 2002 and 2009 at our center. Epidemiological, pathological and family data in patients with GIST alone (group A) were compared with those in patients with GIST associated with other neoplasms (group B). A possible common genetic mechanism was investigated between GIST and associated malignancies by testing the detection of the immunohistochemical marker, CD117, in all tumors.

RESULTS

Twenty-two patients with GIST were identified, 10 in group A (45%) and 12 in group B (55%). In group B, the associated tumor was malignant in 6 patients (50%) and benign in another 6 (50%). Of the 22 patients with GIST, 8 (36%) had a family history of malignancies. Of these 8 patients, 7 (87.5%) were in group B (p=0.03) and 3 (37.5%) showed the same pathological type of neoplasm as their relatives. All GIST were positive for CD117 whereas associated malignancies were negative for this marker.

CONCLUSION

We did not find immunohistochemical positivity for CD117 in malignancies associated with GIST. Given the special characteristics of the study population, the association between GIST and associated malignancies may be incidental.

Validation of stem cell markers in clinical prostate cancer: α6-integrin is predictive for non-aggressive disease

BACKGROUND

Stem cells are postulated to mediate prostate cancer progression, and represent a small fraction of the entire tumor. Various proteins (α2-integrin, α6-integrin, CD117, CD133, EZH2, OCT3/4) are associated with a prostate cancer stem cell phenotype in cell lines and xenografts. Our objective was to investigate expression of stem cell markers in clinical prostate cancer in relation to outcome.

METHODS

We validated immunohistochemical expression of stem cell markers in 481 prostate cancer patients and correlated expression with clinicopathologic parameters.

RESULTS

Sporadic expression of α2-integrin was present in a fraction of tumor cells (<5%) in 94.7% of tumors and associated with PSA > 10 ng/ml (P = 0.04). α6-Integrin expression (<5%) occurred in 28.4% patients, while ≥5% α6-integrin expression was associated with PSA≤10 ng/ml (P = 0.01), Gleason score <7 (P < 0.01) and pT2-disease (P = 0.02). α6-integrin was predictive for biochemical recurrence (P < 0.01), local recurrence (P = 0.03) and disease specific death (P = 0.03). EZH2 expression was generally low with 2.6% of tumors showing ≥1% positive cells. EZH2 was associated with Gleason score ≥7 (P = 0.01) and biochemical recurrence (P = 0.01). We did not identify expression of CD117, CD133, and OCT3/4 in prostate cancer samples.

CONCLUSIONS

Expression of α2-integrin and EZH2 in a small fraction of prostate cancer cells is supportive for their role as stem cell marker. Although α6-integrin was not a unique stem cell marker, it was predictive for prostate cancer biochemical and local recurrence, and disease specific death. The validity of CD117, CD133, and OCT3/4 as prostate cancer stem cell marker is questionable since these proteins were not expressed in clinical prostate cancer.

Diagnostic and prognostic utility of a DNA hypermethylated gene signature in prostate cancer

We aimed to identify a prostate cancer DNA hypermethylation microarray signature (denoted as PHYMA) that differentiates prostate cancer from benign prostate hyperplasia (BPH), high from low-grade and lethal from non-lethal cancers. This is a non-randomized retrospective study in 111 local Asian men (87 prostate cancers and 24 BPH) treated from 1995 to 2009 in our institution. Archival prostate epithelia were laser-capture microdissected and genomic DNA extracted and bisulfite-converted. Samples were profiled using Illumina GoldenGate Methylation microarray, with raw data processed by GenomeStudio. A classification model was generated using support vector machine, consisting of a 55-probe DNA methylation signature of 46 genes. The model was independently validated on an internal testing dataset which yielded cancer detection sensitivity and specificity of 95.3% and 100% respectively, with overall accuracy of 96.4%. Second validation on another independent western cohort yielded 89.8% sensitivity and 66.7% specificity, with overall accuracy of 88.7%. A PHYMA score was developed for each sample based on the state of methylation in the PHYMA signature. Increasing PHYMA score was significantly associated with higher Gleason score and Gleason primary grade. Men with higher PHYMA scores have poorer survival on univariate (p = 0.0038, HR = 3.89) and multivariate analyses when controlled for (i) clinical stage (p = 0.055, HR = 2.57), and (ii) clinical stage and Gleason score (p = 0.043, HR = 2.61). We further performed bisulfite genomic sequencing on 2 relatively unknown genes to demonstrate robustness of the assay results. PHYMA is thus a signature with high sensitivity and specificity for discriminating tumors from BPH, and has a potential role in early detection and in predicting survival.

Mast cell targeting hampers prostate adenocarcinoma development but promotes the occurrence of highly malignant neuroendocrine cancers

Mast cells (MC) are c-Kit-expressing cells, best known for their primary involvement in allergic reactions, but recently reappraised as important players in either cancer promotion or inhibition. Here, we assessed the role of MCs in prostate tumor development. In prostate tumors from both tumor-prone transgenic adenocarcinoma of the mouse prostate (TRAMP) mice and human patients, MCs are specifically enriched and degranulated in areas of well-differentiated (WD) adenocarcinoma but not around poorly differentiated (PD) foci that coexist in the same tumors. We derived novel TRAMP tumor cell lines, representative of WD and PD variants, and through pharmacologic stabilization or genetic ablation of MCs in recipients mice, we showed that MCs promote WD adenocarcinoma growth but are dispensable for PD tumors. WD tumors rely on MCs for matrix metalloprotease 9 (MMP-9) provision, as reconstitution of MC-deficient mice with wild-type but not MMP-9(-/-) MCs was sufficient to promote their growth. In contrast, PD tumors are MMP-9 self-competent, consistently with epithelial-to-mesenchymal transition. Such a dual source of MMP-9 was confirmed in human tumors, suggesting that MCs could be a good target for early-stage prostate cancer. Interestingly, in testing whether MC targeting could block or delay tumorigenesis in tumor-prone TRAMP mice, we observed a high incidence of early and aggressive tumors, characterized by a neuroendocrine (NE) signature and c-Kit expression. Taken together, these data underscore the contribution of MCs in tumor progression and uncover a new, opposite role of MCs in protecting against the occurrence of aggressive NE variants in prostate cancer.

C-kit and its ligand stem cell factor: potential contribution to prostate cancer bone metastasis

The tyrosine kinase receptor c-kit and its ligand stem cell factor (SCF) have not been explored in prostate cancer (PC) bone metastasis. Herein, we found that three human PC cell lines and bone marrow stromal cells express a membrane-bound SCF isoform and release a soluble SCF. Bone marrow stromal cells revealed strong expression of c-kit, whereas PC cells showed very low levels of the receptor or did not express it all. Using an experimental model of PC bone metastasis, we found that intraosseous bone tumors formed by otherwise c-kit-negative PC3 cells strongly expressed c-kit, as demonstrated using immunohistochemical and Western blot analyses. Subcutaneous PC3 tumors were, however, c-kit-negative. Both bone and subcutaneous PC3 tumors were positive for SCF. Immunohistochemical analysis of human specimens revealed that the expression frequency of c-kit in epithelial cells was of 5% in benign prostatic hyperplasia, 14% in primary PC, and 40% in PC bone metastases, suggesting an overall trend of increased c-kit expression in clinical PC progression. Stem cell factor expression frequency was more than 80% in all the cases. Our data suggest that the bone microenvironment up-regulates c-kit expression on PC cells, favoring their intraosseous expansion.

Grundlagen der systemischen Therapie

Die Einführung sog. »zielgerichteter Medikamente« hat einen Paradigmenwechsel in der Systemtherapic maligner Erkrankungen ausgelöst. Voraussetzung hierfür waren die in den letzten 25 Jahren gesammelten Erkenntnisse der molekularbiologischen, molekulargenetischen und immunologischen Grundlagenforschung, die ein besseres Verständnis der pathogenetischen Prozesse im Rahmen der malignen Transformation und Tumorprogression sowie die Identifikation strategischer Zielstrukturen (»Targets«) ermöglichen. Auf diese Weise wurde ein neuer Ansatz der Entwicklung antineoplastischer Therapeutika angestoßen, der auf die Wirkung an spezifischen Molekülaktivitäten und nicht primär auf zelluläre Endpunkte (Wachstumshemmung, Zelltod) ausgerichtet ist.

Interaction and functional cooperation between the serine/threonine kinase bone morphogenetic protein type II receptor with the tyrosine kinase stem cell factor receptor

Transmembrane receptors with intrinsic serine/threonine or tyrosine kinase domains regulate vital functions of cells in multicellular eukaryotes, e.g., differentiation, apoptosis, and proliferation. Here, we show that bone morphogenetic protein type II receptor (BMPR-II) which has a serine/threonine kinase domain, and stem cell factor receptor (c-kit) which contains a tyrosine kinase domain form a complex in vitro and in vivo; the interaction is induced upon treatment of cells with BMP2 and SCF. Stem cell factor (SCF) modulated BMP2-dependent activation of Smad1/5/8 and phosphorylation of Erk kinase. SCF also enhanced BMP2-dependent differentiation of C2C12 cells. We found that BMPR-II was phosphorylated at Ser757 upon co-expression with and activation of c-kit. BMPR-II phosphorylation required intact kinase activity of BMPR-II. Abrogation of the c-kit/SCF-dependent phosphorylation of BMPR-II at the Ser757 interfered with the cooperative effect of BMP2 and SCF. Our data suggest that the complex formation between c-kit and BMPR-II leads to phosphorylation of BMPR-II at Ser757, which modulates BMPR-II-dependent signaling.