Cytotoxic activity of nemorosone in neuroblastoma cells

Abstract

Neuroblastoma is the second most common solid tumour during childhood, characterized by rapid disease progression. Most children with metastasized neuroblastoma die despite intensive chemotherapy due to an intrinsic or acquired chemotherapy resistance. Thus, new therapeutic strategies are urgently needed. Here, we demonstrate that the novel compound nemorosone isolated from alcoholic extracts of Clusia rosea resins by reverse phase high pressure liquid chromatography (RP-HPLC) exerts cytotoxic activity in neuroblas-toma cell lines both parental and their clones selected for resistance against adriamycin, cisplatin, etoposide or 5-fluorouracil. Cell cycle studies revealed that nemorosone induces an accumulation in G0/G1- with a reduction in S-phase population combined with a robust up-regulation of p21Cip1. Furthermore, a dose-dependent apoptotic DNA laddering accompanied by an activation of caspase-3 activity was detected. Nemorosone induced a significant dephosphorylation of ERK1/2 in LAN-1 parental cells probably by the inhibition of its upstream kinase MEK1/2. No significant modulation of signal transducers JNK, p38 MAPK and Akt/PKB was detected. The enzymatic activity of immunoprecipitated Akt/PKB was strongly inhibited in vitro, suggesting that nemorosone exerts its anti-proliferative activity at least in part by targeting Akt/PKB in the cell lines studied. In addition, a synergistic effect with Raf-1 inhibitor BAY 43-9006 was found. Finally, nemorosone induced a considerable down-regulation of N-myc protein levels in parental LAN-1 and an etoposide resistant sub-line at the same drug-concentrations.

The anti-cancer agent nemorosone is a new potent protonophoric mitochondrial uncoupler

“…Moreover, in agreement with previous literature data ( Díaz-Carballo et al, 2008a), we observed that nemorosone exhibits only little toxicity in non-tumor HEK293T cells. Therefore, we believe the nemorosone acidic pK a value could be responsible for its apparent preferential toxicity on HepG2 cells, probably due to a higher proportion of the uncharged nondissociated nemorosone specie available for these cells.…”

“…Nemorosone, a naturally occurring polycyclic polyprenylated acylphloroglucinol, has received increasing attention due to its strong in vitro anti-cancer action (Cuesta-Rubio et al, 2002;Diaz-Carballo et al, 2003, 2008aPopolo et al, 2009). Several mechanisms have been proposed to account for this action, including its ability to target the Akt/PKB signal transducer (Díaz-Carballo et al, 2008a,b) and to induce p300 histone acetyltransferase (Dal Piaz et al, 2010).…”

“…The brown Cuban propolis, whose main component is nemorosone, exerts a significant anti-proliferative action on MCF-7 human breast cancer cells (Popolo et al, 2009). Isolated nemorosone, in turn, elicits cytotoxic action in vitro against a panel of tumor cell lines including breast, colon, brain, ovary, liver, blood and lung carcinoma (Cuesta-Rubio et al, 2002;Diaz-Carballo et al, 2003, 2008a. Specifically, nemorosone's toxicity to neuroblastoma and leukemia parental cell lines has been ascribed to its ability to target the Akt/PKB signal transducer (Díaz-Carballo et al, 2008a,b).…”

Atypical Cell Populations Associated with Acquired Resistance to Cytostatics and Cancer Stem Cell Features: The Role of Mitochondria in Nuclear Encapsulation

“…Even more important was the global change in the physiology of these cells forced by etoposide toward acquirement of the CSC status. In addition, the analysis and validation of iCSC microRNAs isolated from 79HF6 glioblastoma cells revealed a subtle deregulation of different miRNAs such as miR204-5p known to contribute to tumor aggressiveness and metastatic behavior (Díaz-Carballo et al, 2008b;Bao et al, 2013;Qiu et al, 2013). We decided to take a descriptive rather than analytic approach to the miRNA results, as the understanding of the function of the studied representatives and this field in general is still evolving (Fig.…”

Nemorosone and its emerging anti-neoplastic effects

“…Nemorosone is also effective in the management of intracranial tumors such as neuroblastomas. It mediates these anti-neoplastic effects by down-regulating N-myc levels [6]. An increase in the activity of caspase-3, and simultaneous inhibition of Akt/PKB also contributes to these anti-neoplastic effects.…”