The use of chromogranin, synaptophysin and islet amyloid polypeptide as markers for neuroendocrine tumours

Neuroendocrine gene subsets are uniquely dysregulated in prostate adenocarcinoma

Prostate cancer has heterogeneous growth patterns, and its prognosis is the poorest when it progresses to a neuroendocrine phenotype. Using bioinformatic analysis, we evaluated RNA expression of neuroendocrine genes in a panel of five different cancer types: prostate adenocarcinoma, breast cancer, kidney chromophobe, kidney renal clear cell carcinoma and kidney renal papillary cell carcinoma. Our results show that specific neuroendocrine genes are significantly dysregulated in these tumors, suggesting that they play an active role in cancer progression. Among others, synaptophysin (SYP), a conventional neuroendocrine marker, is upregulated in prostate adenocarcinoma (PRAD) and breast cancer (BRCA). Our analysis shows that SYP is enriched in small extracellular vesicles (sEVs) derived from plasma of PRAD patients, but it is absent in sEVs derived from plasma of healthy donors. Similarly, classical sEV markers are enriched in sEVs derived from plasma of prostate cancer patients, but weakly detectable in sEVs derived from plasma of healthy donors. Overall, our results pave the way to explore new strategies to diagnose these diseases based on the neuroendocrine gene expression in patient tumors or plasma sEVs.

Validade dos marcadores tumorais

Considerando-se o número crescente dos chamados marcadores tumorais e a sua incorporação sistemática à prática médica, procedeu-se a um levantamento, por meio de Medline® 1995, na Biblioteca Central do Instituto Nacional de Câncer - INCA, e revisão de 95 resumos de trabalhos publicados de 1995 a abril de 1997. Verificou-se que a validade dos marcadores é maior para o diagnóstico patológico de alguns tipos tumorais e determinação de alguns fatores prognósticos; que poucos são os de real utilidade clínica, seja para prevenção, diagnóstico ou prognóstico, vez que a maioria deles só alcança significância quando a doença já provoca algum sinal ou sintoma; que a maioria das referências correspondem, a rigor, a trabalhos repetidos, que avaliam os mesmos marcadores, embora em diferentes tumores; e que há trabalhos que se referem a poucos casos, quando não pouquíssimos, e cujos resultados tomam-se, por isso, inconsistentes. Neste artigo, os marcadores tumorais são classificados por tipos (genes, expressões genéticas, substâncias circulantes, substâncias celulares, receptores da membrana celular e índices de proliferação tumoral) e por finalidades (prevenção, detecção, diagnóstico, estadiamento, monitoração terapêutica, seguimento pós-tratamento e prognóstico) e são correlacionados com o(s) tumor(es) em que foram pesquisados. Apresentam-se três grupos de critérios de validação (estatísticos, biomédicos e por finalidades) e resume-se, a partir também de mais 16 outras referências bibliográficas, a utilidade de marcadores dos cânceres de mama [ADN, fração de Fase S, índice de ADN, C-erbB-2 (HER-2/neu), P53, CAT-D, CA15.3 e CEA - sem validade; marcadores tumorais hormonais - úteis para a indicação de hormonioterapia adjuvante ou paliativa]; colorretal [LASA, CA 19.9, índice de ADN, fração de Fase S, p53 e ras - sem validade; CEA-com validade para estadiamento e planejamento cirúrgico, e para seguimento pós-operatório (dosagem seriada a cada 2-3 meses por 2 anos, se houve suspeita de metástase hepática em estádios cirúrgicos II e III)] e de próstata (PSA com utilidade para a detecção, mas associado ao toque retal, em homens acima de 40-50 anos, como indicativos da necessidade de exames mais acurados, e para o seguimento dos casos tratados). E inquestionável a utilidade da dosagem de alfa-feto-proteína (aFP) e da gonadotrofina coriônica (hCG), para o estadiamento, tratamento, avaliação da resposta terapêutica e seguimento dos casos tratados de tumores testiculares (aFP e hCG) e de neoplasia trofoblástica gestacional (hCG). Também inquestionável é o papel da identificação dos marcadores de diferenciação celular no diagnóstico patológico de leucemias e linfomas. Os dilemas evidenciados a partir deste estudo referem-se a cinco binômios: 1) ausência de sinal ou sintoma versus positividade de marcador tumoral; 2) detecção de recidiva assintomática versus a qualidade e a quantidade da sobrevida do indivíduo; 3) natureza da causa versus aumento do marcador; 4) exame falso-positivo versus tratamento; e 5) baixo risco de evolução de neoplasia detectada versus tratamento. Conclui-se que, exceto pelos marcadores de validade estabelecida para o diagnóstico, o seguimento do tratamento ou o prognóstico dos casos de alguns cânceres, o médico precisa, além de conhecer os marcadores tumorais e suas siglas, saber os limites das suas indicações e ter opinião, crítica e método na sua utilização.

Validation of SV2A-Targeted PET Imaging for Noninvasive Assessment of Neuroendocrine Differentiation in Prostate Cancer

Neuroendocrine prostate cancer (NEPC) is an aggressive and lethal variant of prostate cancer (PCa), and it remains a diagnostic challenge. Herein we report our findings of using synaptic vesicle glycoprotein 2 isoform A (SV2A) as a promising marker for positron emission tomography (PET) imaging of neuroendocrine differentiation (NED). The bioinformatic analyses revealed an amplified SV2A gene expression in clinical samples of NEPC versus castration-resistant PCa with adenocarcinoma characteristics (CRPC-Adeno). Importantly, significantly upregulated SV2A protein levels were found in both NEPC cell lines and tumor tissues. PET imaging studies were carried out in NEPC xenograft models with ¹⁸F-SynVesT-1. Although ¹⁸F-SynVesT-1 is not a cancer imaging agent, it showed a significant uptake level in the SV2A⁺ tumor (NCI-H660: 0.70 ± 0.14 %ID/g at 50–60 min p.i.). The SV2A blockade resulted in a significant reduction of tumor uptake (0.25 ± 0.03 %ID/g, p = 0.025), indicating the desired SV2A imaging specificity. Moreover, the comparative PET imaging study showed that the DU145 tumors could be clearly visualized by ¹⁸F-SynVesT-1 but not ⁶⁸Ga-PSMA-11 nor ⁶⁸Ga-DOTATATE, further validating the role of SV2A-targeted imaging for noninvasive assessment of NED in PCa. In conclusion, we demonstrated that SV2A, highly expressed in NEPC, can serve as a promising target for noninvasive imaging evaluation of NED.

Differential Protein Expression in Small Intestinal Neuroendocrine Tumors and Liver Metastases

OBJECTIVE

Small intestinal neuroendocrine tumors (SI-NETs) are often detected after they have become metastatic. Using a novel protein array, we identified pathways important in SI-NET metastasis development in surgically resected patients.

METHODS

Paired primary tumors and liver metastases from 25 patients undergoing surgical resection for metastatic SI-NETs were harvested. Extracted proteins were separated by sodium dodecyl sulfate gel and multiplex immunoblots were performed with 136 antibodies. Significant Analysis of Microarray was used to select for differentially expressed proteins. A tissue microarray was constructed from 27 archived specimens and stained by immunohistochemistry.

RESULTS

Comparing primary SI-NETs with matched normal small-bowel mucosa, 9 proteins were upregulated and cyclin E was downregulated. The SI-NET liver metastases demonstrated upregulation of P-ERK and p27 but downregulation of CDK2 and CDC25B. When comparing primary SI-NET with their paired liver metastases, cyclin E demonstrated a significant upregulation in the liver metastasis. Tissue microarray demonstrated higher p38 expression and lower Cdc 25b expression in SI-NETs versus liver metastases and confirmed higher expression of p27 in liver metastases versus normal liver.

CONCLUSIONS

Few studies have compared protein expression in paired primary and metastatic SI-NETs. Our findings reveal changes in a limited number of proteins, suggesting that these may be targets for therapy.

Biochemistry of neuroendocrine tumours

Several circulating or urinary tumour markers can be used for the diagnosis and follow-up of functioning and clinically non-functioning neuroendocrine tumours of the pancreatic islet cells and intestinal tract. Among the specific tumour markers are serotonin and its metabolites--e.g. 5-hydroxyindoleacetic acid (5-HIAA)--in carcinoid tumours and the carcinoid syndrome, insulin and its precursors or breakdown products in insulinoma, and gastrin in gastrinoma. Plasma vasointestinal polypeptide (VIP) determinations have been used in the diagnosis of VIPoma, plasma glucagon for glucagonoma, and serum somatostatin for somatostatinoma. Among the tumour-non-specific markers are: chromogranins, neuron-specific enolase (NSE), alpha-subunits of the glycoprotein hormones, catecholamines, pancreatic polypeptide (PP), ghrelin and adrenomedullin.

N-terminal chromogranin-derived peptides as dilators of bovine coronary resistance arteries

N-terminal peptides of chromogranin A and B (CGA and CGB) were compared for dilator responses in isolated bovine coronary arteries (bCoA), measuring diameter changes as a function of pressure. bCoA developed and maintained myogenic tone (MYT) at approximately 20% from 50 to 150 mm Hg. In contrast to CGB(1-40), CGA(1-40) and CGA(1-76) (VS-I) both displayed significant intrinsic vasodilator effects. CGA(1-40) reduced myogenic reactivity from 70 to 150 mm Hg (p<0.05, n=6). At 75 mm Hg, CGA(1-40) showed a concentration-dependent dilatation at 0.1 nM-10 microM. The dilator effect of CGA(1-40) persisted at moderately elevated [K(+)](e) (8.4-16 mM). However, this effect was diminished by pertussis toxin (PTX) and abolished by antagonists to several subtypes of K(+) channels (tetraethylammonium, Ba(2+) and glibenclamide). These results demonstrate that the N-terminal domain of CGA has dilator effect in the myogenically active bCoA. We propose that CGA(1-40) and the naturally occurring vasostatin I are regulatory peptides of relevance for the coronary microcirculation and that a G(alphai) sub-unit and K(+) channel activation may be involved in the signal pathway.