Restoration of the molecular clock is tumor suppressive in neuroblastoma.

MYCN activation is a hallmark of advanced neuroblastoma (NB) and a known master regulator of metabolic reprogramming, favoring NB adaptation to its microenvironment. We found that the expression of the main regulators of the molecular clock loops is profoundly disrupted in MYCN-amplified NB patients, and this disruption independently predicts poor clinical outcome. MYCN induces the expression of clock repressors and downregulates the one of clock activators by directly binding to their promoters. Ultimately, MYCN attenuates the molecular clock by suppressing BMAL1 expression and oscillation, thereby promoting cell survival. Reestablishment of the activity of the clock activator RORα via its genetic overexpression and its stimulation through the agonist SR1078, restores BMAL1 expression and oscillation, effectively blocks MYCN-mediated tumor growth and de novo lipogenesis, and sensitizes NB tumors to conventional chemotherapy. In conclusion, reactivation of RORα could serve as a therapeutic strategy for MYCN-amplified NBs by blocking the dysregulation of molecular clock and cell metabolism mediated by MYCN.

Tumor protein D52 (isoform 3) interacts with and promotes peroxidase activity of Peroxiredoxin 1 in prostate cancer cells implicated in cell growth and migration.

Tumor protein D52 (TPD52) is overexpressed in multiple cancers including prostate cancer due to gene amplification and investigations to understand its role in the pathophysiology of different cancers are continuing. GST pull-down assays and Tandem affinity purification of TPD52 as bait identified novel prey Peroxiredoxin 1 (PRDX1) in prostate cancer (PCa) cells. PRDX1 interaction with TPD52 was confirmed in immunoprecipitation and affinity interaction assays. Mapping of interaction domain indicated that PRDX1 interacts with C-terminal region of TPD52 containing PEST domain between 152 and 179 amino acids, a new binding region of TPD52. Here we show that TPD52 interaction with PRDX1 increased its peroxidase activity and ectopic expression of TPD52 induced dimerization of PRDX1 in PCa cells. Moreover, H2O2 exposure evoked the interaction between TPD52 and PRDX1 while depletion of both proteins led to the accumulation of H2O2 suggesting peroxidase activity is important to maintain oxidative capacity in PCa cells. We also observed that overexpression or downregulation of TPD52 and PRDX1 individually or together affecting PCa cells growth, survival, and migration. Altogether, our results show a novel interaction partner of TPD52 providing new insights of its functions and ascertain the role of TPD52-PRDX1 interaction in PCa progression.

Dimethylarginine dimethylaminohydrolase-1 (DDAH1) is frequently upregulated in prostate cancer, and its overexpression conveys tumor growth and angiogenesis by metabolizing asymmetric dimethylarginine (ADMA).

Tissue microarray analysis confirmed higher dimethylarginine dimethylaminohydrolase-1 (DDAH1) expression in prostate cancer (PCa) compared to benign and normal prostate tissues. DDAH1 regulates nitric oxide (NO) production by degrading endogenous nitric oxide synthase (NOS) inhibitor, asymmetric dimethylarginine (ADMA). This study examined whether DDAH1 has any physiological role in PCa progression. Using overexpression of DDAH1 in PCa (PC3 and LNCaP) cell lines, we found that DDAH1 promotes cell proliferation, migration and invasion by lowering ADMA levels, as well as increasing NO production. VEGF, HIF-1α and iNOS were upregulated in DDAH1 expressing cells as result of elevated NO. DDAH1 increased secretion of pro-angiogenic signals bFGF and IL-8, into conditioned media. Treatment of DDAH1-positive PCa cells with NOS inhibitors (L-NAME and 1400 W) attenuated DDAH1 activity to promote cell growth. Xenografts derived from these cells grew significantly faster (> twofold) than those derived from control cells. Proliferation rate of cells stably expressing mutant DDAH1 was same as control cells unlike wild-type DDAH1-positive PCa cells. Xenograft tumors derived from mutant-positive cells did not differ from control tumors. VEGF, HIF-1α and iNOS expression did not differ in DDAH1 mutant-positive tumors compared to control tumors, but was upregulated in wild-type DDAH1 overexpressing tumors. Furthermore, CD31 immunostaining on xenograft tissues demonstrated that DDAH1 tumors had high endothelial content than mutant DDAH1 tumors. These data suggest that DDAH1 is an important mediator of PCa progression and NO/DDAH pathway needs to be considered in developing therapeutic strategies targeted at PCa.