Metastatic conventional prostatic adenocarcinoma with diffuse chromogranin A and androgen receptor positivity

Gene expression signatures of neuroendocrine prostate cancer and primary small cell prostatic carcinoma

Background

Neuroendocrine prostate cancer (NEPC) may be rising in prevalence as patients with advanced prostate cancer potentially develop resistance to contemporary anti-androgen treatment through a neuroendocrine phenotype. While prior studies comparing NEPC and prostatic adenocarcinoma have identified important candidates for targeted therapy, most have relied on few NEPC patients due to disease rarity, resulting in thousands of differentially expressed genes collectively and offering an opportunity for meta-analysis. Moreover, past studies have focused on prototypical NEPC samples with classic immunohistochemistry profiles, whereas there is increasing recognition of atypical phenotypes. In the primary setting, small cell prostatic carcinoma (SCPC) is frequently admixed with adenocarcinomas that may be clonally related, and a minority of SCPCs express markers typical of prostatic adenocarcinoma while rare cases do not express neuroendocrine markers. We derived a meta-signature of prototypical high-grade NEPC, then applied it to develop a classifier of primary SCPC incorporating disease heterogeneity.

Methods

Prototypical NEPC samples from 15 patients across 6 frozen tissue microarray datasets were assessed for genes with consistent outlier expression relative to adenocarcinomas. Resulting genes were used to determine subgroups of primary SCPCs (N=16) and high-grade adenocarcinomas (N=16) profiled by exon arrays using formalin-fixed paraffin-embedded (FFPE) material from our institutional archives. A subgroup classifier was developed using differential expression for feature selection, and applied to radical prostatectomy cohorts.

Results

Sixty nine and 375 genes demonstrated consistent outlier expression in at least 80% and 60% of NEPC patients, with close resemblance in expression between NEPC and small cell lung cancer. Clustering by these genes generated 3 subgroups among primary samples from our institution. Nearest centroid classification based on the predominant phenotype from each subgroup (9 prototypical SCPCs, 9 prototypical adenocarcinomas, and 4 atypical SCPCs) achieved a 4.5% error rate by leave-one-out cross-validation. The classifier identified SCPC-like expression in 40% (2/5) of mixed adenocarcinomas and 0.3-0.6% of adenocarcinomas from prospective (4/2293) and retrospective (2/355) radical prostatectomy cohorts, where both SCPC-like retrospective cases subsequently developed metastases.

Conclusions

Meta-analysis generates a robust signature of prototypical high-grade NEPC, and may facilitate development of a primary SCPC classifier based on FFPE material with potential prognostic implications.

Electronic supplementary material

The online version of this article (10.1186/s12885-017-3729-z) contains supplementary material, which is available to authorized users.

Midkine is associated with neuroendocrine differentiation in castration-resistant prostate cancer

BACKGROUND

Castration-resistant prostate cancer (CRPC) is an incurable disease and both androgen-deprivation therapy (ADT) and neuroendocrine differentiation (NED) are closely related to CRPC transition. More knowledge concerning neuroendocrine (NE)-transformed PC cells, the NED process and its association with CRPC, is needed. Expression of growth factor midkine (MDK) is correlated with poor clinical outcomes in various human cancers, including PC. In the present study, we have evaluated MDK expression and NED in two separate tumor groups: early and advanced PC.

METHODS

Immunohistochemical analysis of MDK, the neuronal marker tubulin-beta III (TUBB3) and the NE-marker chromogranin A (CGA) in a human archival material consisting of hormone naive (HN)/stage T1b (n = 29) and CRPC (n = 24) tumors. Triple immunofluorescent imaging was performed on a selection of specimens.

RESULTS

MDK, TUBB3, and CGA were upregulated in CRPC compared to HN tumors. MDK was highly associated to the expression of both CGA and TUBB3, and identified MDK-positive NE-like looking cells found to co-express CGA or, more commonly, CGA together with TUBB3. CGA and TUBB3 staining displayed a partial expression overlap, an overlap almost exclusively displaying also MDK expression.

CONCLUSIONS

MDK upregulation in CRPC is associated with NED (shown by its relation to CGA and TUBB3). The results suggest that MDK represents an over-bridging marker between different populations of NE-like tumor cells, possibly as part of the NED process and associated CRPC transition, something that needs to be evaluated experimentally as does the applicability of MDK as a future target.

The expression of pluripotency marker Oct 3/4 in prostate cancer and benign prostate hyperplasia

BACKGROUND

Oct 3/4 (Octamer 3/4), a member of POU family has been considered as an important stem cell marker and essential transcription factor during human embryogenesis. In recent years, there have also been reports on presence of Oct 3/4 in differentiated benign and malignant human cells. The objective of this study was to investigate the transcription and the protein expression of Oct 3/4 isoforms in prostate cancer and benign prostate tissue.

METHODS

Thirty sex adenocarcinomas and eight cases of benign prostate hyperplasia were studied. The transcription of Oct 3/4 was analyzed using RT-PCR approach associated with restriction digestion analysis. Oct 3/4 protein expression was studied by immunohistochemistry on paraffin sections using two different antibodies.

RESULTS

We identified only the transcript 2 of Oct 3/4 in prostate tumors and benign prostate hyperplasia. Immunohistochemistry verified these results, demonstrating only cytoplasmic localization of Oct 3/4. Transcription of type 1 of Oct 3/4 as well as protein expression with nuclear localization of Oct 3/4 isoform 1 were not detected. Oct 3/4 immunopositive tumors were also displayed neuroendocrine differentiation and showed androgen receptor immunopositivity. The stem cell markers CD44 and CD117 were not detected in Oct 3/4 immunopositive cells.

CONCLUSION

Our results indicate that only the cytoplasmic isoform 2 of Oct 3/4 is present in prostate cancer and benign prostate hyperplasia. The malignant and benign prostate cells, which are immunopositive for variant 2 of Oct 3/4, lack other stem cell markers supporting previously published data that variant 2 of Oct 3/4 is not a pluripotency marker.

Selective expression of CD44, a putative prostate cancer stem cell marker, in neuroendocrine tumor cells of human prostate cancer

BACKGROUND

Hormonal therapy is effective for advanced prostate cancer (PC) but the disease often recurs and becomes hormone-refractory. It is hypothesized that a subpopulation of cancer cells, that is, cancer stem cells (CSCs), survives hormonal therapy and leads to tumor recurrence. CD44 expression was shown to identify tumor cells with CSC features. PC contains secretory type epithelial cells and a minor population of neuroendocrine cells. Neuroendocrine cells do not express androgen receptor and are quiescent, features associated with CSCs. The purpose of the study was to determine the expression of CD44 in human PC and its relationship to neuroendocrine tumor cells.

METHODS

Immunohistochemistry and immunofluorescence were performed to study CD44 expression in PC cell lines, single cells from fresh PC tissue and archival tissue sections of PC. We then determined if CD44+ cells represent neuroendocrine tumor cells.

RESULTS

In human PC cell lines, expression of CD44 is associated with cells of NE phenotype. In human PC tissues, NE tumor cells are virtually all positive for CD44 and CD44+ cells, excluding lymphocytes, are all NE tumor cells.

CONCLUSIONS

Selective expression of the stem cell-associated marker CD44 in NE tumor cells of PC, in combination with their other known features, further supports the significance of such cells in therapy resistance and tumor recurrence.

Long-term outcome of phase I/II clinical trial of Ad-OC-TK/VAL gene therapy for hormone-refractory metastatic prostate cancer

We evaluated the long-term safety and efficacy of Ad-OC-TK (recombinant adenoviral vector carrying an osteocalcin promoter-driven herpes simplex virus thymidine kinase gene) plus VAL (valacyclovir) gene therapy for hormone-refractory prostate cancer. Ad-OC-TK/VAL therapy is the first in vivo adenovirus-mediated gene therapy to be used to treat metastatic prostate cancer, including bone metastasis. Six patients were enrolled in this trial, and two doses of Ad-OC-TK (2.5 x 10(9) or 2.5 x 10(10) plaque-forming units) were injected into locally recurrent tumor or bone metastasis on day 1 and day 8. Patients were also given VAL (3 g/day) for 21 days. Safety and efficacy were evaluated for at least 8 months in each patient. All patients tolerated this therapy with no serious adverse events. One prostate-specific antigen (PSA) response (from 318.3 to 4.9 ng/ml) was observed with a time to PSA progression (TTP) of 12 months. Docetaxel (30 mg/m2 per week) and estramustine (560 mg/day) combination chemotherapy (DE) was given to three docetaxel-naive patients on PSA failure after gene therapy. All three patients had a PSA response to DE therapy with 21, 7, and 4 months of TTP. These results suggest that additional trials are warranted.

Localization of immunoreactive HIF-1alpha and HIF-2alpha in neuroendocrine cells of both benign and malignant prostate glands

BACKGROUND

Hypoxia induces increased tumor growth by promoting angiogenic and glycolytic pathways. Tumors expressing hypoxia-inducible factor-1alpha (HIF-1alpha), an important transcriptional activator of oxygen-regulated genes, are resistant to chemotherapy and radiotherapy. The major challenge in prostate cancer therapy today is to gain a better understanding of the development of hormone-refractory tumors, which is often characterized by neuroendocrine differentiation. Here we studied the expression of HIF-1alpha and HIF-2alpha in neuroendocrine cells of the benign prostate and in prostate cancer.

METHODS

Tissue sections from 30 patients who underwent radical prostatectomy and from 21 patients operated by transurethral resection of the prostate were selected for immunohistochemical analysis for expression of HIF-1alpha, HIF-2alpha, androgen receptor (AR), neuroendocrine markers (chromogranin A, synaptophysin), and two gene products downstream of HIF-1alpha: VEGF and GAPDH.

RESULTS

Immunoreactive HIF-1alpha was detected in a subpopulation of AR-negative neuroendocrine cells in benign and malignant prostate tissue. Analysis of serial sections showed that the levels of expression of GAPDH and VEGF proteins are increased in AR-negative malignant neuroendocrine cells expressing HIF-1alpha. In situ-hybridization indicated that HIF-1alpha mRNA levels are not higher in neuroendocrine prostate cancer cells relative to corresponding non-neuroendocrine tumor cells. We also demonstrated induced stabilization of nuclear HIF-1alpha in LNCaP cells by hypoxia and long-term stimulation with interleukin-6. Focal HIF-2 expression was detected in benign neuroendocrine-like cells and in malignant prostatic cells.

CONCLUSIONS

The expression of HIF-1alpha and HIF-2alpha in prostate cancer has been confirmed, but we also identified immunoreactive HIF-1alpha and downstream gene products in benign and malignant prostate neuroendocrine cells.

Docetaxel and cisplatin in patients with metastatic androgen independent prostate cancer and circulating neuroendocrine markers

PURPOSE

A link between neuroendocrine cell differentiation and resistance to androgen deprivation has been observed in prostate cancer, suggesting the possible efficacy of specific treatments. We assessed the efficacy and toxicity of a chemotherapy regimen combining docetaxel and cisplatin in men with androgen independent prostatic adenocarcinoma and circulating neuroendocrine markers.

MATERIALS AND METHODS

A total of 41 patients were treated with a combination of 75 mg/m(2) docetaxel and 75 mg/m(2) cisplatin every 3 weeks for a maximum of 6 cycles. The primary study end point was the neuroendocrine response rate, defined as a decrease in neuron specific enolase and/or chromogranin A to 50% or greater of the supranormal baseline serum value. Median followup was 40 months.

RESULTS

A median of 6 cycles per patient was delivered. A neuroendocrine response was observed in 13 patients (33%). The median response duration was 4 months (range 2 to 10). The prostate specific antigen response rate was 48%. A clinical benefit was observed in 45% of patients who required analgesics at study entry. The objective response rate was 41% in 29 patients with measurable metastases. Five patients had to stop therapy due to toxicity. The main side effects were cumulative asthenia and sensitive neuropathy. Median survival was 12 months (range 1 to 38).

CONCLUSIONS

Regarding the disappointing efficacy and significant toxicity observed in this study, the combination of docetaxel and cisplatin cannot be recommended in daily practice. Further studies are necessary to determine whether patients with circulating neuroendocrine markers require specific therapeutic approaches.

Comprehensive expression analysis of l-dopa decarboxylase and established neuroendocrine markers in neoadjuvant hormone-treated versus varying Gleason grade prostate tumors

Current hormone withdrawal therapies used for treatment of advanced prostate cancer lead to androgen-independent tumor growth. Increased prostatic neuroendocrine (NE) cell density has been implicated in promoting progression of prostate cancer, but the process by which this occurs remains unclear. The aim of this study was to determine whether there is an association of increased NE differentiation with neoadjuvant hormone therapy and Gleason grade. Using adjacently sectioned tissue microarrays, the expression profile of novel and known NE markers were monitored. L-Dopa decarboxylase (DDC), a catecholamine synthesis enzyme and androgen receptor (AR) coregulator protein, was identified as an additional NE marker of prostate cancer. Immunohistochemical analysis of DDC with the established NE markers, chromogranin A and bombesin, revealed a significant increase in NE differentiation after 6 months of hormone therapy and after progression to androgen independence but no apparent correlation with Gleason grade. In addition, dual immunofluorescence analysis revealed that approximately 55% of the mixed population of DDC- and chromogranin A-expressing NE cells continue to express AR. Taken together, these results suggest that the increase of NE differentiation in prostate cancers depends specifically on duration of hormone therapy. This increase may be due to the transdifferentiation of AR-expressing epithelial-derived adenocarcinoma cells into an NE cell phenotype.

BM18: A novel androgen-dependent human prostate cancer xenograft model derived from a bone metastasis

BACKGROUND

Androgen-dependent prostate cancer (PrCa) xenograft models are required to study PrCa biology in the clinically relevant in vivo environment.

METHODS

Human PrCa tissue from a femoral bone metastasis biopsy (BM18) was grown and passaged subcutaneously through male severe combined immune-deficient (SCID) mice. Human mitochondria (hMt), prostate specific antigen (PSA), androgen receptor (AR), cytokeratin-18 (CK-18), pan-cytokeratin, and high molecular weight-cytokeratin (HMW-CK) were assessed using immunohistochemistry (IHC). Surgical castration was performed to examine androgen dependence. Serum was collected pre- and post-castration for monitoring of PSA levels.

RESULTS

BM18 stained positively for hMt, PSA, AR, CK-18, pan keratin, and negatively for HMW-CK, consistent with the staining observed in the original patient material. Androgen-deprivation induced tumor regression in 10/10 castrated male SCID mice. Serum PSA levels positively correlated with BM18 tumor size.

CONCLUSIONS

BM18 expresses PSA and AR, and rapidly regresses in response to androgen withdrawal. This provides a new clinically significant PrCa model for the study of androgen-dependent growth.

Skewing Towards Neuroendocrine Phenotype in High Grade or High Stage Androgen-Responsive Primary Prostate Cancer

OBJECTIVE

The prognostic influence of neuroendocrine (NE) differentiation in prostate cancer patients is not yet properly established. In a series of primary hormone-naive prostate cancers from a patient population that underwent radical prostatectomy, we wanted to determine the relationship between NE phenotype expression and Gleason sum, disease stage, and serum PSA concentration.

METHODS

Chromogranin A (CgA) expression was scored and compared in 105 consecutive primary prostate cancers with their homologous preoperative tumor prostate biopsies.

RESULTS

High grade or high stage prostate cancers expressed a significantly higher CgA score than low grade or localized diseases (p < 0.005). Both the CgA score of the surgical specimens and the PSA level in the serum increased linearly (p = 0.001). In the samples of many corresponding tumor biopsies no significant CgA staining was found.

CONCLUSION

NE differentiation in primary untreated prostate cancer is closely associated with the major prognostic parameters of survival. This association cannot be shown by evaluating the CgA staining in tumor biopsies.

Insulin-like growth factor 1, chromogranin A and prostate specific antigen serum levels in prostate cancer patients and controls

OBJECTIVE

Insulin-like growth factor 1 (IGF-1) and chromogranin A (CGA) are currently discussed as supplemental serum markers for prostate cancer (PC) diagnosis. To address this issue we determined serum levels of IGF-1, CGA and PSA in men with newly diagnosed PC and controls.

METHODS

A consecutive series of 156 men (median age: 67 yrs) with newly diagnosed, untreated PC and 271 controls (69 yrs) were recruited. The diagnosis of PC was made by transrectal ultrasound guided biopsies only. In controls, the presence of PC was excluded by digito-rectal examination, serum prostate specific antigen (PSA) levels by using age-specific reference values and-if indicated-by transrectal ultrasound guided 12-core biopsies. Serum levels of IGF-1, CGA and PSA were compared between cases and controls and correlated to histopathological findings and age.

RESULTS

Serum PSA-levels were significantly higher in men with PC (49.6+/-13.9 ng/ml, mean+/-standard error of the mean; median: 7.0 ng/ml) than in controls (2.6+/-0.2 ng/ml; median: 1.3 ng/ml) (p<0.001). In contrast, serum levels of IGF-1 (PC: 166+/-6.1 ng/ml, median: 155 ng/ml; controls: 159+/-4.5 ng/ml, 153 ng/ml) and CGA (PC: 92+/-7.4 U/l, median: 67 U/l; controls: 117+/-12.0 U/l; median: 74 U/l) were identical in both groups (p>0.05). Serum levels of IGF-1 and CGA revealed no correlation to serum PSA, Gleason score and number of positive biopsy cores. In the PC-cohort all three serum markers did not correlate with age. In controls, PSA (p=0.018) and CGA (p<0.001) correlated positively and IGF-1 (p<0.001) negatively with age.

CONCLUSION

Our data suggest that quantification of IGF-1 and CGA-serum levels provides no useful information in the diagnosis of PC.