Gallium-68 DOTATOC PET/CT in vivo characterization of somatostatin receptor expression in the prostate

AIM

The aim was to investigate somatostatin receptor (sstr) expression in normal prostate by determining the maximum standardized uptake value (SUVmax) of (68)Ga-DOTATOC PET/CT in neuroendocrine tumor (NET) patients, without NET involvement of the prostate gland, for establishing the reference standard.

METHODS

Sixty-four NET patients underwent (68)Ga-DOTATOC PET/CT. SUVmax of the prostate gland, normal liver, testes, and gluteus muscles were evaluated. The prostate gland size was measured. Statistical analysis was performed using dedicated software (SPSS13).

RESULTS

Mean/median (68)Ga-DOTATOC SUVmax values were as follows: normal prostate 2.6 ± 0.0, slightly enlarged prostate 4.2 ± 1.6, prostatic hypertrophy 4.9 ± 1.6, prostatic hyperplasia 5.0 ± 1.5, prostate cancer 9.5 ± 2.1, normal liver 7.3 ± 1.8, testes 1.8 ± 0.5, and gluteus 1.0 ± 0.2. The normal prostate gland had three times less sstr expression than normal liver tissue. Strong correlation was found between patient age and sstr expression in prostate/prostate size. No significant difference existed in sstr expression between prostatic hypertrophy and hyperplasia. Much higher sstr expression was found in prostatic cancer compared with normal prostate.

CONCLUSION

(68)Ga-DOTATOC PET/CT defines the baseline sstr uptake in prostate not affected by NET (significantly lower than in the liver). Higher values were established in prostatic hyperplasia and hypertrophy. Only concomitant prostate cancer was associated with higher SUVmax in comparison with non-neoplastic liver.

The grey zone between pure (neuro)endocrine and non-(neuro)endocrine tumours: a comment on concepts and classification of mixed exocrine-endocrine neoplasms

Terms such as "mixed endocrine-exocrine carcinoma" (MEEC) and "adenocarcinoma with neuroendocrine (NE) differentiation" (ADC-NE) identify tumours belonging to the spectrum of neoplasms with divergent exocrine and (neuro)endocrine differentiation. These tumours display variable quantitative extent of the two components, potentially ranging from 1 to 99%, and variable structural patterns, ranging from single scattered NE cells to a well-defined NE tumour cell population organized in organoid, trabecular or solid growth patterns. In the present report, the grey zone of tumours/carcinomas with mixed NE and non-NE features is explored for various organs. From a practical point of view, MEECs differ from carcinomas with focal NE differentiation by (1) the extension of each component (more than 30%) and (2) the structural pattern of the NE component, either organoid for well-differentiated or solid/diffuse for poorly differentiated cases. In MEECs, the most aggressive cell population drives the clinical behaviour. Conversely, ADC-NE generally do not show a different clinical outcome, compared to the corresponding conventional forms, except for prostatic adenocarcinoma, in which NE cells are a negative prognostic factor. The recognition of MEECs may be of relevance for a targeted therapeutic strategy, foreseeing the use of biotherapies similar to those proposed for pure NE tumours.

Gene expression in the LNCaP human prostate cancer progression model: progression associated expression in vitro corresponds to expression changes associated with prostate cancer progression in vivo

Identification of the genes involved in prostate cancer (PCa) progression to a virulent and androgen-independent (AI) form is a major focus in the field. cDNA microarray was used to compare the gene expression profile of the indolent, androgen sensitive (AS) LNCaP PCa cell line to the aggressively metastatic, AI C4-2. Thirty-eight unique sequences from a 6388 cDNA array were found differentially expressed (> or =2-fold, 95% CI). The expression of 14 genes was lower in C4-2 than in LNCaP cells, while the reverse was true for 24 genes. Twelve genes were validated using Q-PCR, Western blotting and immunohistochemistry (IHC) of LNCaP and C4-2 xenograft. Q-PCR showed that 10 of 12 (83.3%) genes had similar patterns of expression to the array (LNCaP>C4-2: TMEFF2, ATP1B1, IL-8, BTG1, BChE, NKX3.1; LNCaP<C4-2: BNIP3, TM4SF1, AMACR, UCH-L1). By Western blot, 4/5 genes examined: TMEFF2, NKX3.1, AMACR, and UCH-L1, not IL-8, were consistent with RNA profiling. Protein expression levels were confirmed in human tumor xenografts using IHC. A large proportion of the markers found in this expression profile is consistent with those recently identified in human PCa tissues along with several novel genes that remain to be examined. These data further demonstrate the utility of the LNCaP human PCa progression model as a tool to investigate the phenotypic changes required for the progression to AI and metastasis.

Neuroendocrine differentiation in extrahepatic bile duct carcinomas and its prognostic significance

Neuroendocrine differentiation is known to be one of the prognostic factors in many carcinomas. However, the characteristics of neuroendocrine differentiation are not well elucidated in extrahepatic bile duct (EBD) carcinomas. One hundred ninety-four cases of EBD carcinomas were analyzed using immunohistochemistry with synaptophysin and chromogranin. The tumors were graded as degree 0, 1, and 2 when the positive tumor cells were 5% or less, 6% to 25%, and 26% or more, respectively. Immunohistochemical results were compared with clinicopathologic variables and survival rate. Synaptophysin and chromogranin were positive in 54 (27.8%) and 74 (38.1%) cases, respectively. Thirty-four cases (17.5%) were positive for both synaptophysin and chromogranin, 20 (10.3%) and 40 cases (20.6%) were positive only for synaptophysin and for chromogranin, respectively, and 100 cases (51.6%) were negative for both markers. There was a significant survival difference between overall synaptophysin-positive (median, 27 months) and synaptophysin-negative (38 months) groups (P < .05). However, there was no survival difference between chromogranin-positive and chromogranin-negative groups. There was a significant survival difference between the dual-positive expression to synaptophysin and chromogranin group (median, 21 months) and the dual-negative expression group (median, 35 months; P < .05). In summary, synaptophysin expression was an important prognostic factor because synaptophysin-positive cases showed a worse prognosis than synaptophysin-negative cases. The more tumor cells expressed chromogranin, the poorer the survival. Therefore, immunohistochemical studies for neuroendocrine differentiation may be helpful in routine pathological examinations for evaluating the survival and the prognosis of patients with EBD carcinomas.

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.

Neuroendocrine differentiation in prostate cancer: implications for new treatment modalities

OBJECTIVES

This review aims to provide practising clinicians with the most recent knowledge of the biological nature of prostate cancer (PC) to facilitate investigation of new treatment modalities for patients with PC, especially the hormone-refractory state of the disease.

METHODS

Review of the literature using PubMed search and scientific journal publications.

RESULTS

Much progress has been made towards an understanding of the development and progression of PC, and the factors which drive the development of androgen independence. Neuroendocrine (NE) cells may provide an intriguing link between NE cell differentiation and tumour progression in PC with the genetically supported formation of androgen-independent clones which regulate the proliferation of neighbouring non-NE-phenotype cancer cells in a paracrine manner by secretion of NE products. Various NE peptides stimulate proliferation of androgen-independent PC through transactivation of the androgen receptors (AR). Therefore, cancerous epithelial cells that increase their responsiveness to NE factors or induce NE cells to release trophic factors may have a survival advantage over their siblings.

CONCLUSION

This review shows the need to improve our understanding of the biological nature of PC, especially cancer cells of the NE phenotype and their regulatory products to develop new therapeutic protocols and trials based on NE hormones and their agonists/antagonists.

Changes in chromogranin a serum levels during endocrine therapy in metastatic prostate cancer patients

INTRODUCTION

The concept of neuroendocrine (NE) differentiation in prostate cancer has become more widely recognized as its diagnostic, prognostic, and therapeutic usefulness.

PATIENTS AND METHODS

We enrolled 38 patients with stage D prostate cancer who underwent endocrine therapy by medical or surgical castration and oral antiandrogen. According to PSA response, serum levels of CGA as a marker of NE differentiation were measured at the multiple points of time; (1) pre-treatment, (2) complete response (CR), (3) a nadir level of PSA, (4) PSA failure or hormone independent progression. We compared these serum values in relation to efficacy of endocrine therapy.

RESULTS

There was no correlation between serum PSA and CGA values. Patients consisted of 27 with CR and 11 without CR. Serum CGA increased as intervals of endocrine therapy became longer with positive correlation (p < 0.05). Its velocity was higher in patients with PSA failure than in those without it (6.98 vs. 2.09 ng/ml/month, p = 0.011).

CONCLUSION

During endocrine therapy in metastatic prostate cancer patients, serum CGA values were not related to serum PSA levels, and increased as treatment periods became longer. It is suggested that CGA velocity has potential to predict androgen independent progression after endocrine therapy.

Expression of serotonin receptors and role of serotonin in human prostate cancer tissue and cell lines

BACKGROUND

Increase in the number of serotonin (5-HT) releasing neuroendocrine (NE) cells has been shown to be correlated with tumor progression, loss of androgen dependence, and poor prognosis. Serotonin is a well-known mitogen which mediates a wide variety of physiological effects via multiple receptors, of which receptor subtype 1 (5-HTR1) has been identified in prostate cancer (PC) cell lines. Recently, 5-HT has been found to show growth-promoting activity and to be functionally related to oncogenes.

MATERIALS AND METHODS

Localization, protein content, and mRNA expression of 5-HTR subtype 1A, 1B, and 1D was studied in prostatic tissue (35 patients), metastases, PC cell lines, a benign prostatic stromal cell line (human prostate cell preparation (hPCP)), and xenografts of PC-3 cells by immunohistochemistry (IHC), Western blotting, and RT-PCR, respectively. The growth-inhibition effect of a 5-HT1A antagonist (NAN-190) on PC cell lines was studied using a bromodeoxyuridine (BrdU) assay.

RESULTS

A strong immunoreaction of 5-HTR1A and 1B was demonstrated in high-grade tumor cells (35/35) and a small number of BPH cells, whereas 5-HTR1D was confined to vascular endothelial cells. 5-HTR1A was also demonstrated in PC cells metastasized to lymph node and bone, PC-3, DU145, LNCaP, and in xenografts of PC-3 cells and hPCP. Western blot analysis gave strong bands from PC tissue extracts compared to BPH tissue. Using RT-PCR, 5-HTR1A mRNA was demonstrated in all PC cell lines. An antagonist of 5-HTR1A (NAN-190) inhibited the growth of PC-3, DU145, and LNCaP cells but not of hPCP cells.

CONCLUSIONS

This is the first study demonstrating an overexpression of 5-HTR subtypes 1A and 1B in PC cells, especially in high-grade tumors. Moreover, 5-HT stimulates proliferation of PC cells and 5-HTR1A antagonists inhibit proliferation. Thus, we propose that 5-HT has an important role in tumor progression, especially in the androgen-independent state of the disease. The design of specific antagonists for this type of receptor might be useful for the growth control of androgen-independent tumors.

Somatostatin receptors: from basic science to clinical approach. Unlabeled somatostatin analogues-1: Prostate cancer

Neuroendocrine cells have been found in all the stages of prostate cancer, but their clinical significance is not completely understood. Neuroendocrine cells are androgen receptor- and prostate-specific antigen-negative, do not proliferate, and secrete many neuropeptides, such as chromogranin A. Neuroendocrine differentiation of prostate cancer correlates with an advancing tumour stage, poor prognosis and tumour progression after androgen deprivation. Furthermore, neuroendocrine phenotype is associated with the increased expression of neo-angiogenesis and vascular endothelial growth factor and with an over-expression of survivin, a new anti-apoptosis protein. Chromogranin A is the quantitatively major secretory protein of the vesicles inside neuroendocrine prostate cells and it is the marker most frequently used to detect neuroendocrine features, both in tissues and in general circulation. Tumours displaying neuroendocrine phenotype tend to be more aggressive and resistant to hormone-therapy. Neuroendocrine differentiation seems to be a dynamic phenomenon: in vitro and in vivo data suggest that it can be induced by androgen suppression. Moreover, the differences in the expression of somatostatin receptors between primary and hormone-refractory prostate cancer are likely to be related to the changes in neuroendocrine phenotype during androgen deprivation. Circulating chromogranin A levels seem to be scarcely affected by endocrine- and chemotherapy, while they significantly decreased after treatment with somatostatin analogs.

National Comprehensive Cancer Network guidelines for the management of prostate cancer

Guidelines for the management of prostate cancer issued by the National Comprehensive Cancer Network provide a basis for rational treatment decisions. These guidelines represent consensus recommendations by a panel of experts that are evidence based and are designated according to the degree of consensus within the expert panel. The initial stratification point is the patient's life expectancy (>5 or <5 years). If life expectancy is >5 years, the recommended intervention is based on clinical stage, prostate-specific antigen (PSA) level, and Gleason score, as well as the presence of symptoms. These assessments establish the patient's risk of recurrence after therapy. Specific initial therapies are then recommended according to whether the risk category is low, intermediate, high, or very high. The guidelines also describe the appropriate use of observation ("watchful waiting") versus active intervention in certain patients. After definitive therapy, patients should be monitored with PSA determinations, digital rectal examination, and bone scans, as outlined in the guidelines. Patients who exhibit increasing PSA levels after prostatectomy are candidates for salvage therapy with androgen ablation, radiotherapy, or observation. If PSA levels begin to increase after radiotherapy, surgery may then be an additional option. Systemic salvage therapy generally consists of androgen ablation; the benefit of total androgen blockade versus initial monotherapy remains controversial. Relapse after initial androgen ablation is treated with an antiandrogen, if none had been administered previously. Patients refractory to further hormonal manipulations are observed or receive palliative therapy, including chemotherapy. The treatment of prostate cancer is complex. Optimal treatment is risk-adapted to the specific characteristics of the cancer and the expected longevity and personal preferences of the patient.