Novel cellular systems unveil mucosal melanoma initiating cells and a role for PI3K/Akt/mTOR pathway in mucosal melanoma fitness

BACKGROUND

Mucosal Melanomas (MM) are highly aggressive neoplasms arising from mucosal melanocytes. Current treatments offer a limited survival benefit for patients with advanced MM; moreover, the lack of pre-clinical cellular systems has significantly limited the understanding of their immunobiology.

METHODS

Five novel cell lines were obtained from patient-derived biopsies of MM arising in the sino-nasal mucosa and designated as SN-MM1-5. The morphology, ultrastructure and melanocytic identity of SN-MM cell lines were validated by transmission electron microscopy and immunohistochemistry. Moreover, in vivo tumorigenicity of SN-MM1-5 was tested by subcutaneous injection in NOD/SCID mice. Molecular characterization of SN-MM cell lines was performed by a mass-spectrometry proteomic approach, and their sensitivity to PI3K chemical inhibitor LY294002 was validated by Akt activation, measured by pAkt(Ser473) and pAkt(Thr308) in immunoblots, and MTS assay.

RESULTS

This study reports the validation and functional characterization of five newly generated SN-MM cell lines. Compared to the normal counterpart, the proteomic profile of SN-MM is consistent with transformed melanocytes showing a heterogeneous degree of melanocytic differentiation and activation of cancer-related pathways. All SN-MM cell lines resulted tumorigenic in vivo and display recurrent structural variants according to aCGH analysis. Of relevance, the microscopic analysis of the corresponding xenotransplants allowed the identification of clusters of MITF-/CDH1-/CDH2 + /ZEB1 + /CD271 + cells, supporting the existence of melanoma-initiating cells also in MM, as confirmed in clinical samples. In vitro, SN-MM cell lines were sensitive to cisplatin, but not to temozolomide. Moreover, the proteomic analysis of SN-MM cell lines revealed that RICTOR, a subunit of mTORC2 complex, is the most significantly activated upstream regulator, suggesting a relevant role for the PI3K-Akt-mTOR pathway in these neoplasms. Consistently, phosphorylation of NDRG1 and Akt activation was observed in SN-MM, the latter being constitutive and sustained by PTEN loss in SN-MM2 and SN-MM3. The cell viability impairment induced by LY294002 confirmed a functional role for the PI3K-Akt-mTOR pathway in SN-MM cell lines.

CONCLUSIONS

Overall, these novel and unique cellular systems represent relevant experimental tools for a better understanding of the biology of these neoplasms and, as an extension, to MM from other sites.

Antidiabetic and hypolipidemic potential of Campomanesia xanthocarpa seed extract obtained by supercritical CO2

Abstract Campomanesia xanthocarpa, a plant belonging to the Myrtaceae family, is popularly known as gabiroba. Leaves of gabiroba has been popularly used to treat various diseases, including inflammatory, renal, and digestive, among others. Additionally, studies have shown an effect to reduce blood cholesterol levels. The aim of this study was to evaluate the antihyperglycemic and hypolipidemic effects of Campomanesia xanthocarpa seed extract in hyperglycemic rats. The results showed that 400 mg/kg of seed extract was able to decrease blood glucose levels and to increase the muscular and hepatic glycogen content as well as to inhibit the sucrase and maltase activity. At doses of 200 mg/kg and 800 mg/kg, the activity of these enzymes was also reduced. In the lipid profile 400 mg/kg produced a decrease in total and LDL cholesterol serum levels; and with 200 mg/kg there was an increase in HDL cholesterol levels. The extract did not present hepatic and renal toxic effects at the different doses tested. The results suggest that the treatment with Campomanesia xanthocarpa seeds extract is useful in reducing glycemia, total cholesterol and LDL levels with potential adjuvant therapeutic in the treatment of diabetes and hypercholesterolemia, however, additional pharmacological and toxicological studies are still required.

Antioxidant activity, antibacterial and inhibitory effect of intestinal disaccharidases of extracts obtained from Eugenia uniflora L. Seeds

Abstract The use of medicinal plants for disease prevention, treatment and cure is an ancient practice used by humanity, and many plants species are used in bioprospecting research. In this context, its stands out Eugenia uniflora L., populary known as pitangueira and belongs to the Myrtaceae family, with a wide geographic distribution and native of Brazil. In view of the therapeutic qualities of the plant and the lack of the studies on its seeds, the present study had as objective to evaluate the phytochemical profile of the extracts of Eugenia uniflora L. seeds, from different solvents, as well as their antibacterial activity, antioxidant and its inhibitory effect of intestinal disaccharidases. Results showed a high content of phenolic compounds and total flavonoids, thus characterizing antioxidant activity, also highlighting the best bacteriostatic action for the Gram positive strain of Staphylococcus aureus in the ethanolic fraction. Regarding the disaccharidases, a strong inhibitory action was observed for all concentrations, evidencing a antihyperglycemic potential. The present research allowed to concluded that Eugenia uniflora L. seeds have promising biological activities for the industrial sector, but a more detailed investigation is needed regarding their bioactive compounds.

Primary malignant ossifying fibromyxoid tumour of the bone. A clinicopathologic and molecular report of two cases

Objective

To report the exceptional occurrence of ossifying fibromyxoid tumour (OFMT) as a primary bone lesion. OFMT is a rare soft tissue tumour of uncertain differentiation and variable malignant potential, that occurs in adults with a slight male predominance. It is typically located in the subcutis or in the skeletal muscles of the extremities, followed by trunk or head and neck.

Methods

Two cases of OFMT proven to arise from bone are presented. The first is a 65-year old female with a history of rib "osteosarcoma", presenting with an inferior lobe left lung mass. The second is a man with a lytic lesion of the 5th cervical vertebra that recurred shortly after resection. Following H&E and immunohistochemical examination, tumour samples were analysed by NGS and by break-apart FISH to detect rearrangement of the PHF1 and TFE3 genes.

Results

PHF1 gene-rearrangement was identified by FISH on both the primary and the metastatic lesion of first patient. NGS identified a PHF1(intron1) and EPC1 (exon 10) fusion transcript later confirmed by positive PHF1 rearrangement on FISH in the second case.

Conclusions

The demonstration of PHF1 gene rearrangements represents a fundamental ancillary diagnostic test when presented with challenging examples of OFMT.

Clear cell sarcoma-like/malignant gastrointestinal neuroectodermal tumor of the tongue: a clinicopathologic and molecular case report

Malignant gastrointestinal neuroectodermal tumor (M-GNET) and clear cell sarcoma (CCS) of soft tissue represent closely related, extremely rare, malignant mesenchymal neoplasm of uncertain differentiation. Both entities are characterized genetically by the same molecular alterations represented by the presence of EWSR1-ATF1 and, more rarely, EWSR1-CREB1 fusion genes. The latter translocation seems to be more represented in M-GNET that, despite significant morphologic overlap with CCS, tends to lack overt features of melanocytic differentiation. Most M-GNET occur in the lower gastrointestinal tract, whereas occurrence in the upper tract has been reported only exceptionally. The differential diagnosis represents a major challenge, and accurate diagnosis impact significantly on therapeutic planning. We herein report the clinicopathologic features of a molecularly confirmed M-GNET that arose at the base of the tongue and review the pertinent literature.

Multifocal Medulloblastoma in an Adult Patient: Description of a Rare Presentation and Review of the Literature

Medulloblastoma is an embryonal neuroepithelial tumor that affects mainly childhood and more rarely adults. Medulloblastoma occurring as multiple nodules at diagnosis is a rare and tricky presentation. Here, we describe the case of a previously healthy 47-year-old woman with multiple posterior fossa cerebellar tumors. Histological, immunohistochemical, and molecular analyses were performed to best characterize the two excised lesions. The histopathological analysis revealed different variants of medulloblastoma in the excised nodules, one being extensive nodularity, rare in adults, and the other desmoplastic/nodular with areas of anaplasia. Immunostains and molecular analysis classified both nodules as SHH medulloblastoma. Adult medulloblastoma is extremely rare. Important differences exist between adult medulloblastoma and medulloblastoma arising in children and infants. Such differences are in location, distribution of histological variants and of molecular subgroups, survival rates, and therapeutic options. An extensive morphological and molecular characterization of such rare tumors is necessary to choice the best-tailored therapy.

A Pediatric Intra-Axial Malignant SMARCB1-Deficient Desmoplastic Tumor Arising in Meningioangiomatosis

SMARCB1 inactivation is a well-established trigger event in atypical teratoid/rhabdoid tumor. Recently, a role for SMARCB1 inactivation has emerged as a mechanism of clonal evolution in other tumor types, including rare brain tumors. We describe an unusual malignant intra-axial SMARCB1-deficient spindle cell desmoplastic neoplasm, occurring in a 6-year-old child with meningioangiomatosis and a long history of seizures. Striking features of the tumor were a storiform pattern and strong CD34 expression. Undifferentiated round cell areas with isolated rhabdoid cells showing high mitotic index and focal necrosis with INI1 expression loss were present. The meningioangiomatosis component showed few chromosomal imbalances, including chromosomal 22 monosomy (where SMARCB1 maps) and gain at 6q14.3. In addition to these abnormalities, the spindle cell desmoplastic neoplasm and its dedifferentiated SMARCB1-deficient component shared several other aberrations, including homozygous deletion at 9p21.3, losses at 1p, 3p, 3q, 10p, and 13q, gains and losses at 5p and 11p. In line with INI1 loss, the dedifferentiated component showed remarkably decreased levels of SMARCB1 transcript. The residual SMARCB1 allele was wildtype. Our findings suggest progression from the meningioangiomatosis to the malignant desmoplastic neoplasm through the occurrence of complex chromosomal abnormalities, and point to functional silencing of SMARCB1 in the dedifferentiation component.

Transcriptome sequencing identifies ETV6-NTRK3 as a gene fusion involved in GIST

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. The vast majority of GISTs are driven by oncogenic activation of KIT, PDGFRA or, less commonly, BRAF. Loss of succinate dehydrogenase complex activity has been identified in subsets of KIT/PDGFRA/BRAF-mutation negative tumours, yet a significant fraction of GISTs are devoid of any of such alterations. To address the pathobiology of these 'quadruple-negative' GISTs, we sought to explore the possible involvement of fusion genes. To this end we performed transcriptome sequencing on five KIT/PDGFRA/BRAF-mutation negative, SDH-proficient tumours. Intriguingly, the analysis unveiled the presence of an ETV6-NTRK3 gene fusion. The screening by FISH of 26 additional cases, including KIT/PDGFRA-mutated GISTs, failed to detect other ETV6 rearrangements beside the index case. This was a 'quadruple-negative' GIST located in the rectum, an uncommon primary site for GIST development (∼4% of all GISTs). The fusion transcript identified encompasses exon 4 of ETV6 and exon 14 of NTRK3 and therefore differs from the canonical ETV6-NTRK3 chimera of infantile fibrosarcomas. However, it retains the ability to induce IRS1 phosphorylation, activate the IGF1R downstream signalling pathway and to be targeted by IGF1R and ALK inhibitors. Thus, the ETV6-NTRK3 fusion might identify a subset of GISTs with peculiar clinicopathological characteristics which could be eligible for such therapies. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Shorter myotomy on the gastric site (≤2.5 cm) provides adequate relief of dysphagia in achalasia patients

The right length of the myotomy on the gastric side for esophageal achalasia is still a debated issue. We aimed to investigate the final outcome after classic myotomy (CM) as compared with a longer myotomy on the gastric side (LM) in two cohorts of achalasia patients. Forty-four achalasia patients who underwent laparoscopic Heller-Dor were considered; patients with a sigmoid-shaped esophagus were excluded. Symptoms were scored using a detailed questionnaire for dysphagia, regurgitation, and chest pain. Barium swallow, endoscopy, and esophageal manometry were performed before and 6 months after the surgical treatment; 24-hour pH-monitoring was also performed 6 months after the procedure. CM was defined as a gastric myotomy length in the range of 1.5-2.0 cm, while LM was 2.5-3 cm in length. The surgical treatment (CM or LM) was adopted in two consecutive cohorts. Treatment failure was defined as a postoperative symptom score >10th percentile of the preoperative score (i.e. >8). Of the 44 patients representing the study population, 20 had CM and 24 had LM. The patients' demographic and clinical parameters (age, sex, symptom score, duration of symptoms, esophageal diameter, and manometric pattern) were similar in the two groups. The median follow up was 24 months (interquartile range 12-39). One patient in each group was classified as a treatment failure. After the treatment, there was a significant decrease in both groups' symptom score, and resting and residual pressure (P < 0.01), with no statistically significant differences between the two groups in terms of postoperative symptom score, resting and residual pressure, or total and abdominal lower esophageal sphincter length and esophageal diameter. Extending the length of the myotomy on the gastric side does not seem to change the final outcome of the laparoscopic Heller-Dor procedure.

Monosomy of chromosome 17 in breast cancer during interpretation of HER2 gene amplification

Monosomy of chromosome 17 may affect the assessment of HER2 amplification. Notably, the prevalence ranges from 1% up to 49% due to lack of consensus in recognition. We sought to investigate the impact of monosomy of chromosome 17 to interpretation of HER2 gene status. 201 breast carcinoma were reviewed for HER2 gene amplification and chromosome 17 status. FISH analysis was performed by using double probes (LSI/CEP). Absolute gene copy number was also scored per each probe. HER2 FISH test was repeated on serial tissue sections, ranging in thickness from 3 to 20 µm. Ratio was scored and subsequently corrected by monosomy after gold control test using the aCGH method to overcome false interpretation due to artefactual nuclear truncation. HER2 immunotests was performed on all cases. 26/201 cases were amplified (13%). Single signals per CEP17 were revealed in 7/201 (3.5%) cases. Five out of 7 cases appeared monosomic with aCGH (overall, 5/201, 2.5%) and evidenced single signals in >60% of nuclei after second-look on FISH when matching both techniques. Among 5, one case showed amplification with a pattern 7/1 (HER2/CEP17>2) of copies (3+ at immunotest); three cases revealed single signals per both probes (LSI/CEP=1) and one case revealed a 3:1 ratio; all last 4 cases showed 0/1+ immunoscore. We concluded that: 1) monosomy of chromosome 17 may be observed in 2.5% of breast carcinoma; 2) monosomy of chromosome 17 due to biological reasons rather than nuclear truncation was observed when using the cut-off of 60% of nuclei harboring single signals; 3) the skewing of the ratio due to single centromeric 17 probe may lead to false positive evaluation; 4) breast carcinomas showing a 3:1 ratio (HER2/CEP17) usually show negative 0/1+ immunoscore and <6 gene copy number at FISH.

Complex karyotype, older age, and reduced first-line dose intensity determine poor survival in core binding factor acute myeloid leukemia patients with long-term follow-up

Approximately 40% of patients affected by core binding factor (CBF) acute myeloid leukemia (AML) ultimately die from the disease. Few prognostic markers have been identified. We reviewed 192 patients with CBF AML, treated with curative intent (age, 15-79 years) in 11 Italian institutions. Overall, 10-year overall survival (OS), disease-free survival (DFS), and event-free survival were 63.9%, 54.8%, and 49.9%, respectively; patients with the t(8;21) and inv(16) chromosomal rearrangements exhibited significant differences at diagnosis. Despite similar high complete remission (CR) rate, patients with inv(16) experienced superior DFS and a high chance of achieving a second CR, often leading to prolonged OS also after relapse. We found that a complex karyotype (i.e., ≥4 cytogenetic anomalies) affected survival, even if only in univariate analysis; the KIT D816 mutation predicted worse prognosis, but only in patients with the t(8;21) rearrangement, whereas FLT3 mutations had no prognostic impact. We then observed increasingly better survival with more intense first-line therapy, in some high-risk patients including autologous or allogeneic hematopoietic stem cell transplantation. In multivariate analysis, age, severe thrombocytopenia, elevated lactate dehydrogenase levels, and failure to achieve CR after induction independently predicted longer OS, whereas complex karyotype predicted shorter OS only in univariate analysis. The achievement of minimal residual disease negativity predicted better OS and DFS. Long-term survival was observed also in a minority of elderly patients who received intensive consolidation. All considered, we identified among CBF AML patients a subgroup with poorer prognosis who might benefit from more intense first-line treatment.

Reagent and labor cost optimization through automation of fluorescence in situ hybridization (FISH) with the VP 2000: an Italian case study

In the modern molecular diagnostic laboratory, cost considerations are of paramount importance. Automation of complex molecular assays not only allows a laboratory to accommodate higher test volumes and throughput but also has a considerable impact on the cost of testing from the perspective of reagent costs, as well as hands-on time for skilled laboratory personnel. The following study tracked the cost of labor (hands-on time) and reagents for fluorescence in situ hybridization (FISH) testing in a routine, high-volume pathology and cytogenetics laboratory in Treviso, Italy, over a 2-y period (2011-2013). The laboratory automated FISH testing with the VP 2000 Processor, a deparaffinization, pretreatment, and special staining instrument produced by Abbott Molecular, and compared hands-on time and reagent costs to manual FISH testing. The results indicated significant cost and time saving when automating FISH with VP 2000 when more than six FISH tests were run per week. At 12 FISH assays per week, an approximate total cost reduction of 55% was observed. When running 46 FISH specimens per week, the cost saving increased to 89% versus manual testing. The results demonstrate that the VP 2000 processor can significantly reduce the cost of FISH testing in diagnostic laboratories.

Anaplastic ependymoma of the third ventricle

Supratentorial ependymomas are rare, especially in the third ventricle. We report the case of an ependymoma of the posterior third ventricle that was endoscopically removed just by aspiration through a flexible scope. Histologically, beside the typical pattern of growth with perivascular pseudorosettes, the tumor featured hypercellular areas with more than 10 mitoses per 10 high-power fields, consistent with grade III-anaplastic tumor. A few months later, a second neuroendoscopy offered the unique chance to appreciate the total absence of tumor tissue and the restored anatomy. However, consistently with the high grade, the tumor recurred in two different locations including the endoscopic trajectory, and spread through the cerebrospinal fluid. The patient underwent a second resective surgery and radiosurgery. Despite a cycle of chemotherapy, multiple lesions both in the ventricular system and at the level of cauda equina appeared 12 months later. A comprehensive review of intraventricular anaplastic ependymomas is also provided.

Autism and esophageal achalasia in childhood: a possible correlation? Report on three cases

Chronic gastrointestinal symptoms are commonly reported in autistic patients. Dysphagia is often present, and it is generally related to behavioral eating disorders. The association between autism and esophageal achalasia has not been described in literature yet. We report our experience with three cases of autistic children we recently treated for esophageal achalasia. In the first case (a 14-year-old male), achalasia was diagnosed with barium swallow and esophageal manometry and was successfully treated with three pneumatic endoscopic dilatations (follow-up: 3 years). In the second case (a 12-year-old female), achalasia was diagnosed with barium swallow and esophageal manometry and was treated with Heller myotomy after two unsuccessful pneumatic endoscopic attempts (follow-up: 3 months). In the last case, a 15-year-old male underwent barium swallow and endoscopy that confirmed achalasia. He was treated with Heller myotomy, and he is asymptomatic at a 6-month follow-up. To our knowledge, this is the first report of a possible association between autism and esophageal achalasia. Because of the rarity of both diseases, their association in the same patient is unlikely to be casual even if speculation on their common etiology is impossible at present. This finding needs further confirmation, but it is sufficient, in our opinion, to indicate proper evaluation with barium swallow and/or manometry in any autistic children with eating difficulty.

A "twist box" code of p53 inactivation: twist box: p53 interaction promotes p53 degradation

Twist proteins have been shown to contribute to cancer development and progression by impinging on different regulatory pathways, but their mechanism of action is poorly defined. By investigating the role of Twist in sarcomas, we found that Twist1 acts as a mechanism alternative to TP53 mutation and MDM2 overexpression to inactivate p53 in mesenchymal tumors. We provide evidence that Twist1 binds p53 C terminus through the Twist box. This interaction hinders key posttranslational modifications of p53 and facilitates its MDM2-mediated degradation. Our study suggests the existence of a Twist box code of p53 inactivation and provides the proof of principle that targeting the Twist box:p53 interaction might offer additional avenues for cancer treatment.

Age- and cell-related gene expression of aromatase and estrogen receptors in the rat testis

Spermatogenesis is a complex and coordinated process leading to the formation of spermatozoa. This event, which is under the control of numerous endocrine and paracrine factors, seems to also be controlled by estrogens which exert their effects via nuclear estrogen receptors (ESRs) ESR1 and ESR2. Estrogens are synthesized by aromatase which is biologically expressed in the rat testis. The objective of our study was to clarify the gene expression patterns of aromatase and ESRs according to age and in the two compartments of the adult rat testis. In the adult, transcripts of aromatase vary according to the germ cell type and to the stages of seminiferous epithelium, a maximum being observed at stage I. The ESR1 gene is highly expressed in the adult testis and in stages from VIIc-d to XIV. Moreover, both ESR mRNA levels are higher in purified round spermatids than in pachytene spermatocytes, suggesting a putative role of estrogens in the haploid steps of spermatogenesis. The variability of the results in the expression of both ESRs led us to explore the putative presence of variants in the rat testis. Concerning ESR1, we have shown the presence of the full-length form and of one isoform with exon 4 deleted. For ESR2, besides the wild type, three isoforms were observed: one with exon 3 deleted, another with an insertion of 54 nucleotides, and the last one with both modifications. Therefore, the stage-regulated expression of aromatase and ESR1 genes in the rat testis suggests a likely role of estrogens in spermatogenesis.

Concomitant chronic lymphocytic leukemia and acute myeloid leukemia: evidence of simultaneous expansion of two independent clones

The simultaneous appearance of chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML) has been rarely reported, with AML occurring more frequently as a secondary event in patients receiving cytotoxic drugs for a primary lymphoproliferative disorder. We describe a case of simultaneous CLL and AML documented by morphological and cytometric analysis in a previously untreated patient. In particular, on the basis of morphological and immunological features, the patient was diagnosed as being affected by CD34 + /CD13 + /CD33 + /HLA-DR + /CD7 + FAB-M2 AML, along with a B-CLL characterized by neoplastic cells expressing a VH3-53/D3-22/JH4 Ig, bearing, on average, 3.9% IgVH mutations without evidence of antigen-driven selection. To establish whether the two neoplastic cell populations shared some common molecular signature, we performed IgH gene rearrangement studies on CD34 + /CD19- and CD34-/CD19 + immunomagnetically sorted cell populations: only genomic DNA from the CD19 + /CD34- cell fraction revealed the presence of the IgH gene rearrangement. These results provide evidence that the rare concomitant association of CLL and AML likely arises from simultaneous expansion of two independent clones.

The biochemical basis of Parkinson's disease: the role of catecholamine o-quinones: a review-discussion

This paper reviews the possible role of catecholamine o-quinones (oQs) in the genesis of Parkinson's disease (PD). This disease is characterized by damage caused to the pigmented catecholaminergic cells in various areas of the brain. The pigment involved is neuromelanin that is the end product of catecholamine oxidation by the o-quinone route. Evidence is presented regarding the overproduction in PD of these catecholamine oQs that damage the electron chain in the mitochondria leading to cell death. The roles of glutathione S-transferase and reactive oxygen species in this are also surveyed. A review of all known biochemical properties of these o-quinones is included. The hypothesis is put forward that an important factor in the genesis of PD may be the overload by environmental toxins of enzymes such as glutathione S-transferase that also detoxify catecholamine oQs.

Differences of ropivacaine and bupivacaine relevant to antiinflammatory activity, platelet aggregation and antioxidant activity in vitro

Ropivacaine and bupivacaine affect the in vitro growth of rat fibroblasts and monkey kidney Vero cells with bupivacaine generally showing the stronger effect. Up to 3 mM concentration the two anesthetics affect the expression of genes differently for CD2, CD3 gamma, CD40L, IL-2, IL-2R alpha, IL-2R beta, IL-2R gamma, IL-4, and IL-4R during activation of human lymphocytes, with bupivacaine showing the higher effect. Human platelet aggregation is inhibited by the two anesthetics which also show an antioxidant effect on lipid peroxidation of rat liver microsomes. In both cases bupivacaine seems more active than ropivacaine.

Enzymatic dopamine peroxidation in substantia nigra of human brain

The main metabolic pathway affected in Parkinson's disease is that of dopamine oxidation and melanin formation in substantia nigra which involves both oxidative and reductive enzymes. The cyclic nature of the biosynthetic pathway from dopamine to melanin implies that a derangement at any of the steps may result in the disappearance of melanin. Possible pathogenetic events such as oxidative stress have therefore no clearcut interpretation since they may be both cause or consequence of the disease. This paper documents the existence of a peroxidase converting dopamine to dopaminochrome in the presence of hydrogen peroxide in the substantia nigra of autopsied human brain. The activatory effect of dopaminochrome on a purified peroxidase is shown, together with the inhibitory effect of dopaminochrome-derived melanin and the activatory effect of melanin/Fe. The toxic effect of dopaminochrome on murine neuroblastoma cells cultured in vitro is demonstrated together with the inhibition of dopaminochrome melanization induced by acetylcholine in vitro.

Toxicity of dopamine and dopaminochrome on cultured cells

Cultured rat fibroblasts, monkey kidney tumor cells (line Vero) and murine neuroblastoma cells were exposed to dopamine or dopaminochrome in the presence and absence of ascorbic acid. Ascorbic acid is able to potentiate the toxicity of both dopamine and dopaminochrome for all the tested cells. The toxicity of dopaminochrome was higher than that of dopamine. There is a correlation between toxicity and levels of bioreductive defenses of the cells, e.g. DT-diaphorase (NAD(P)H:quinone oxidoreductase EC 1.6.99.2) and glutathione. In general, tumor cells have lower defenses and seem to be more sensitive to the toxic action.